1 Introduction

Additive manufacturing (AM), commonly known as 3D printing (3DP), is a rapidly evolving technology that has made significant strides in modern manufacturing and is transforming various industries. The American Society for Testing and Materials (ASTM) defined AM as “a procedure of linking constituents to generate things from 3D model statistics, typically layer upon layer, as divergent to subtractive engineering procedures” [1]. Emerging in the mid-1980s, AM has become a forefront technology driving the latest industrial revolution. It involves the layer-by-layer construction of three-dimensional (3D) structures directly from computer-aided design (CAD) models [2]. AM techniques offer several advantages, including design freedom, minimum tool usage and the ability to fabricate technically competent products. It is also a sustainable manufacturing method, resulting in reduced energy consumption, resource requirements, and associated CO2 emissions throughout the material’s lifecycle. Moreover, it brings changes to labor agreements and contributes to the transition to a digitalized supply chain [3]. Nowadays, AM technologies are progressively employed in fabricating a range of groundbreaking items, such as artificial heart pumps [4], cornea [5], PGA rocket engines [6], jewelry collections [7], steel bridges in Amsterdam [8], and other products in major industries like biomedical, food processing, construction, aeronautical, and textile industries. Nevertheless, it is crucial to enhance the inherent material properties in AM while enabling precise control at the atomic and molecular scale to drive advancements across diverse industries. Hence, the integration of nanotechnology into AM processes is emerging as a pivotal catalyst capable of revolutionizing the manufacturing landscape, offering unparalleled improvements in material properties, precise control at the atomic and molecular scale, and the emergence of groundbreaking functionalities.

Nanotechnology, a forefront technology, enables precise manipulation of materials at atomic, molecular, and super-molecular levels, showcasing its revolutionary potential. It allows unprecedented control over material properties and structure by engineering constituents at the nanoscale, leading to the development of functional systems with unique physical, chemical, and biological properties [9]. AM has undergone a remarkable transformation with the application of NMs, including conventional polymeric, ceramic, metal, and carbon-based materials (at the nanoscale), revolutionizing the entire industry [10]. These NMs possess immense potential to accelerate manufacturing and introduce enriched technical aspects for constructing sophisticated structures and complex shapes. Incorporating NMs into AM has recently garnered considerable interest in creating paradigm shifts, undertaking revolutionary applications, and making innovative technology more accessible and affordable. The blend of tunable physicochemical properties of NMs and the simplicity of producing intricate structures with a simple mouse click in AM has captured widespread attention [11]. NMs can be incorporated into AM through three primary methods: solvent blending, melt compounding, and in situ generation. Solvent blending involves dispersing NMs in a solvent, mixing them with the feedstock material, followed by the removal of the solvent through evaporation or drying [12]. Melt compounding, on the other hand, involves melting the polymer matrix and incorporating the NMs through processes such as extrusion or twin-screw compounding [13]. In-situ generation is another approach that involves synthesizing or forming NMs directly within the feedstock material during AM process itself, facilitating their immediate integration into the printed structure [14]. The incorporation of NMs in AM devices enables the achievement of highly customizable functionalities across electrical, mechanical, optical, and chemical domains, driven by the scale-dependent performance of specific materials [15].

This comprehensive review aims to provide a thorough and up-to-date overview of NM-based AM, highlighting its dynamic properties, prospects, and challenges. The article extensively explores the various categories of NMs utilized in AM, their implementation into different AM categories, and the resulting impact on the properties of the final products. Furthermore, the review identifies the latest advancements in NM-based AM and explores its potential applications across diverse fields. Lastly, the article addresses critical challenges that arise when integrating NMs into AM, including cost considerations, scalability limitations, reproducibility challenges, and safety concerns.

2 Nanomaterial and its categories for implementation in AM

Nanomaterial (NM), as defined by the European Commission (EC), is “A natural, incidental, or manufactured material containing particles, in an unbound state or as an aggregate or as an agglomerate, where, for 50% or more of the particles in the number size distribution, one or more external dimensions is in the size range 1 nm—100 nm” [16]. NMs can be composed of a single constituent material or a combination of different constituents [Fig. 1(A)]. Although NMs often tend to aggregate with diverse compositions, as shown in [Fig. 1(B)], the synthesis of pure single-composition NMs can be achieved using various straightforward methods [17, 18]. The primary objective in designing NMs is to exhibit unique characteristics, such as superior strength, chemical reactivity, or conductivity, compared to related materials with macroscale features [17].

Fig. 1
figure 1

A Illustration of a Single material; and b Composites fabricated from nanomaterials, adapted from [17]; B Naturally formed nanomaterials from natural and biological products, for example, nanoscopic materials of fundamental selenium coated with microbial proteins developed by bio-reductive or oxidative metabolism in bacteria and fungi, adapted from [18]

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Surface and quantum effects are two significant explanations for the inverse behavior of NMs compared to bulk materials. One aspect of inverse behavior is related to the size-dependent properties of NMs, which play a crucial role in this phenomenon. At the nanoscale, the high surface-to-volume ratio becomes prominent, and the behavior of NMs is strongly influenced by the increased proportion of atoms or molecules located on the surface. This can lead to enhanced reactivity, surface energy, or surface-related phenomena, such as increased catalytic activity or altered surface chemistry, which distinguish NMs from bulk materials. In addition, the confinement of electrons and the quantization of energy levels in NMs lead to quantum effects. As the size of NMs decreases, the confinement of electrons becomes more pronounced, leading to changes in their electronic structure and energy bandgap. Consequently, NMs exhibit size-dependent optical, electronic, and magnetic properties that deviate from those of bulk materials [19].

These unique properties and phenomena exhibited by NMs have opened up new avenues for their integration into AM process. NMs can be broadly categorized into carbon-based, metallic, ceramic, and polymer (Fig. 2) [20]. Each category offers distinct properties that contribute to enhancing mechanical strength, conductivity, thermal stability, and the ability to customize functionalities in 3D-printed objects.

Fig. 2
figure 2

Different nanomaterial categories integrated into additive manufacturing for versatile product fabrication

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2.1 Carbon-based nanomaterials

The integration of carbon-based NMs into AM has gained significant attention due to their potential for enhancing the properties and performance of printed materials. Carbon-based NMs, such as carbon nanotubes (CNTs) and graphene, possess unique structural, electrical, and mechanical properties, making them ideal candidates for improving the functionality and strength of AM components [21]. Researchers have focused on incorporating CNTs into AM processes to enhance the mechanical strength, conductivity, and thermal stability of printed materials. In a recent study by [22], the impact of incorporating multi-walled carbon nanotube (MWCNT) into 3D-printed bio-inspired spherical-roof cubic cores was investigated in terms of peak force, stability, and energy-absorbing properties. The findings revealed that coating the cores with MWCNTs substantially enhanced their compressive performance, highlighting their potential as lightweight energy-absorbing components [22]. In another recent study conducted by, [23], a comparison between graphene and MWCNT as fillers in ethylene vinyl acetate (EVA) for fabricating flexible electrically conductive polymer composites through AM was performed. Both fillers enhanced conductivity, with MWCNT demonstrating lower resistance. However, the MWCNT composites showcased improved flow behavior at higher temperatures, dimensional stability, and the potential for fabricating flexible electrically conductive parts [23].

Recent studies have emphasized the exceptional biocompatibility of single-walled carbon nanotubes (SWCNTs) for tissue engineering applications. [24] proposed a one-step method to enhance the cytocompatibility of 3D-printed scaffolds using conductive SWCNTs. The functionalization with SWCNTs improved cell adhesion, proliferation, and differentiation, while the conductive coating enabled electrical stimulation for enhanced cellular behavior and expression of osteogenic gene markers. These findings demonstrate a simple and effective approach to improve the performance of 3D-printed scaffolds in bone tissue engineering applications [24]. In addition, SWCNTs were used as reinforcing materials to create functional nanocomposites. [25] demonstrated the significance of CNTs in 3D printing for fabricating electrically conductive polymer nanocomposites with enhanced mechanical properties. The incorporation of MWCNT and SWCNT improved the modulus, tensile strength, and electrical conductivity of the printed composites. These findings indicate the potential of these nanocomposites for applications in thermoelectric devices and sensors, benefiting from their multifunctional properties and the ability to achieve complex geometries through 3D printing. SWCNTs also enhance thermal conductivity, making them well-suited for applications that demand efficient heat dissipation [25].

Graphene, another carbon-based NMs, has demonstrated its prowess in AM. Incorporating graphene has enhanced the electrical conductivity of printed objects, rendering them suitable for applications in electronics and sensors [26]. Graphene-based NMs (GNMs) can play a pivotal role as ink formulations in the 3D printing process[27] demonstrated the capability of graphene nanoinks to enable the direct layer-by-layer fabrication of high-quality graphene nanosheets into three-dimensional graphene aerogels using freeze 3D printing. This was achieved with the assistance of water-soluble imidazolium-based poly-(ionic liquid) stabilizers. The results showcased the great potential of this scalable technique for applications in batteries and supercapacitors, owing to the achieved stability and concentration of graphene dispersions [27]. In addition, remarkable enhancements in the mechanical properties of the printed structures were observed, including increased hardness and modulus, highlighting the significant reinforcing impact of graphene [28]. The potential of GNMs as a tissue engineering scaffold holds great promise. [29] successfully fabricated 3D printed scaffolds using GNMs, which exhibited specific topography that facilitated cell alignment and orientation. Moreover, graphene played a critical role in promoting cell differentiation, such as induced pluripotent stem cells (iPSC) commitment to neuroectoderm and facilitating myoblast fusion into multinuclear myotubes. These findings highlight the potential of these scaffolds as promising tools for various tissue engineering applications [29].

In addition to CNTs and graphene, carbon nanofibers (CNFs) and carbon black (CB) have also exhibited significant potential for AM components. [30] demonstrated the crucial impact of CNFs on improving mechanical properties in additive manufactured thermoplastic composites. The incorporation of CNFs enhanced modulus, strength, and strain, with nozzle geometry influencing tensile strength and void geometry. Improved material performance resulted from the dispersion and alignment of nanofibers, while fracture surface analysis revealed a fiber pullout mechanism and higher fractured energy, underscoring the potential of CNFs for enhancing failure resistance [30]. On the contrary, CB has found application as a conductive filler in printing inks for creating conductive structures. Its exceptional electrical conductivity enables the printing of functional components, including electrodes and antennas [31].

2.2 Metallic nanomaterials

Metallic NMs offer promising opportunities for enhancing the performance and functionality of AM processes. Various metallic nanoparticles (NPs), including gold, silver, copper, and titanium, have been explored by researchers to develop advanced AM materials with improved mechanical, electrical, optical and thermal properties [32]. Among these, gold NPs (AuNPs) have been extensively investigated in AM to fabricate scaffolds for bone tissue engineering due to their biocompatibility, biodegradability, and ability to stimulate osteogenic differentiation and bone development. [33] conducted research demonstrating the considerable potential of incorporating AuNPs onto AM scaffolds with a polydopamine (PDA) coating for bone tissue engineering. This innovative approach effectively stimulated osteogenesis and played a crucial role in the healing and remodeling processes of bone defects [33]. Moreover, AuNPs have also shown prospects in the field of cardiac tissue engineering. In a recent study, [34] integrated AuNPs into poly-ε-caprolactone (PCL) nanocomposite scaffolds for 3D printing. The incorporation of AuNPs enhanced the mechanical properties, electrical conductivity, and wettability of the scaffolds, making them suitable for cardiovascular applications—notably, the scaffold containing 0.5 wt.% AuNPs demonstrated optimal characteristics, including increased compressive strength, electrical conductivity, and improved hydrophilicity. This highlights the potential of AuNPs in AM for developing electroconductive scaffolds for myocardial tissue engineering [34].

Silver nanoparticles (AgNPs) have been extensively studied for their applications in AM. In a recent study by [35], the potential of incorporating AgNPs into photopolymer resins for AM was highlighted. This incorporation led to improved thermal properties and enhanced heat flow characteristics. The optimization of process parameters, including layer resolution, laser power, and exposure time, played a crucial role in successfully reinforcing resins with AgNPs using AM. The inclusion of AgNPs resulted in significant advancements in the thermal performance of photopolymer resins, offering new possibilities for tailored nanocomposites in AM applications [35]. [36] successfully synthesized AgNPs using a green technique, yielding large electrochemically active sites and high electrical conductivity. The incorporation of AgNPs onto pencil graphite electrodes (PGEs) with a chitosan (CS) matrix within a 3D printed microfluidic platform resulted in a high-performance symmetric supercapacitor. The supercapacitor exhibited rapid charge–discharge rates, high specific areal capacitance, exceptional stability, and notable electro-catalytic activity for detecting hydrogen peroxide (H2O2). The sensor demonstrated high accuracy, selectivity, and sensitivity in detecting H2O2 in cosmetic and medical samples, highlighting its potential as a disposable and low-cost device for H2O2 detection [36]. In addition, AgNPs enhance electrical characteristics in nanocomposites by improving conductivity, facilitating efficient charge transfer, and lowering the percolation threshold for a continuous conductive network. Recent research by [37] revealed the critical role of AgNPs in enhancing the electrical and electrochemical properties of functionalized graphene. Using the AM technique, they successfully produced uniformly distributed microarchitectures of graphene decorated with AgNPs, highlighting remarkable electrical conductivity. These structures showcased their adaptability in various flexible electronic devices, such as sensors and electromagnetic interference (EMI) shielding grids, highlighting the promising prospects of AgNP-graphene 3D microarchitectures in advanced printed electronics [37].

Copper nanomaterials (CuNMs) integrated into AM offer enhanced mechanical properties and biocidal capabilities, making them valuable for medical applications [38]. Demonstrated the successful use of CuNMs as fillers in vat photopolymerization (VPP) AM resin, resulting in nanocomposites with improved mechanical responses. The fabricated nanocomposites exhibited approximately 33.7% increased mechanical performance and sufficient antibacterial activity, showcasing their potential for effective nanocomposite fabrication in medical applications using the AM process [38]. In addition, titanium NPs have also garnered significant attention for their potential in AM [38]. Successfully incorporated titanium nitride (TiN) NPs into acrylonitrile butadiene styrene (ABS) nanocomposites using the material extrusion (ME) AM method. This integration resulted in notable improvements in the mechanical properties of the 3D-printed structures, including enhanced flexural modulus of elasticity (42.3%) and toughness (54.0%). The findings of this research demonstrate the promising potential of TiN NPs in augmenting the mechanical response of thermoplastic polymers in AM [39]. Moreover, iron oxide (Fe3O4) NPs in 3D printing have shown promise in anticancer treatment [40]. Successfully incorporated Fe3O4 NPs into the fabrication of PCL/Fe3O4 mat through AM. The incorporation of Fe3O4 NPs effectively induced hyperthermia, resulting in a high cell death rate and inhibition of tumor growth in vivo. This magnetic mat presents a promising solution for localized hyperthermia cancer therapy, offering precise delivery of Fe3O4 NPs and demonstrating prolonged therapeutic efficacy [40].

2.3 Ceramic and semiconductor nanomaterials

Ceramic and semiconductor NMs have found extensive applications in various AM fields, leveraging their unique characteristics such as exceptional mechanical durability, superior electrical conductivity, and high thermal stability [41, 42]. Biodegradable ceramic nanostructures have proven effective in bone tissue applications, enabling the creation of meticulously designed scaffolds and personalized implants for bone replacements. Ceramic NMs, such as hydroxyapatite (HA), have been widely used in 3D printing for biomedical purposes, particularly in the fabrication of personalized implants that exhibit superior biocompatibility, osteoconductive and promote bone growth [43]. Similarly, semiconductor NPs like quantum dots have been used to fabricate highly sensitive diagnostic sensors for detecting biomarkers and diseases [44]. Also, semiconductor NPs, such as silicon carbide (SiC), have been implemented into 3D printed electronics, leading to substantial enhancements in conductivity and structural integrity [41].

The utility of ceramic and semiconductor NPs has also been evident in energy-related applications. In the fabrication of solid oxide fuel cells (SOFCs) using AM, ceramic NPs like yttria-stabilized zirconia (YSZ) have been leveraged to enhance ionic conductivity and thermal stability [45]. On the other hand, semiconductor NPs like cadmium telluride (CdTe) have been used in the fabrication of solar cells via AM, resulting in improved light absorption and conversion efficiency [46]. Besides the energy and biomedical sectors, ceramic and semiconductor NPs have found applications in various functional domains. For instance, titanium carbide (TiC) NPs have been employed in AM for aerospace applications, offering enhanced capabilities for producing aerospace components with superior thermal and mechanical properties. The incorporation of TiC NPs has shown promising results in improving the performance and reliability of aerospace structures, contributing to the advancement of aerospace technology [47]. Simultaneously, the use of semiconductor NPs like gallium nitride (GaN) has facilitated the production of high-performance light-emitting diodes (LEDs) via AM, providing improved brightness and energy efficiency [48].

2.4 Polymeric nanomaterials

Polymeric NMs have garnered significant interest in AM due to their ability to enhance the properties and functionalities of printed objects. These NMs, typically ranging in size from 1 to 100 nm, can be incorporated into the polymer matrix to improve mechanical strength, flexibility, and other desired characteristics [49]. For example, [50] demonstrated the advantages of incorporating polyhedral oligomeric silsesquioxane (POSS) NMs, and cartilage-derived extracellular matrix (ECM) particles, into polycaprolactone (PCL)/poly-(lactic-co-glycolic acid) (PLGA) polymeric biomaterial inks for 3D-printed scaffolds in cartilage tissue engineering. This incorporation resulted in improved mechanical uniformity, increased hydrophilicity, optimal formation of pores, and enhanced biocompatibility [50]. In another research, [38] highlighted the suitability of polylactic acid (PLA) NPs for AM, emphasizing their safety, cost-effectiveness, and environmentally friendly nature. They successfully incorporated AgNPs into PLA through a reactive melt mixing process, producing antimicrobial and anti-adhesive objects with tunable properties. This approach addressed the drawbacks associated with pre-made AgNPs, including high cost, agglomeration, and uncertainty in nanoparticle quality, offering cost-effective alternatives for various metallic objects in healthcare settings [51].

Polymeric NMs for AM can be synthesized using various methods like emulsion polymerization, nanoprecipitation, and electrostatic assembly, employing diverse materials, including biodegradable polymers, polymers with specific functionalities, and hybrid polymer-metal NPs. These techniques allow precise control of the NMs' size, shape, and surface characteristics, resulting in enhanced dispersion within the polymer matrix and optimized material properties [52]. Additionally, functional NMs, such as drug-loaded NPs or NPs with sensing capabilities, can be incorporated into polymers, enabling the production of multifunctional printed objects [53].

In a recent study, [54] successfully integrated AgNPs into poly-lactic-co-glycolic acid (PLGA) polymer to produce antibacterial scaffolds through 3D printing. These scaffolds demonstrated exceptional mechanical properties, biocompatibility, and effective antibacterial activity, highlighting their potential application in bone tissue engineering [54]. Polymeric NMs can also enable precise drug release in 3D-printed medical devices. For example, [55] successfully developed a novel drug delivery system by incorporating tocopheryl polyethylene glycol succinate (TPEGS) and PLGA-based methotrexate-loaded NPs into alginate-gelatine 3D printable hydrogel ink. The resulting 3D-printed tablets exhibited high accuracy, and in vitro studies showed a controlled and prolonged release of methotrexate over 24 h, mimicking gastrointestinal conditions [55]. These advancements open up possibilities for the development of tailored medical implants or drug delivery systems using polymeric NMs.

Table 1 summarizes some research findings related to the utilization of various nanomaterial categories in AM for different applications.

Table 1 Various categories of nanomaterials employed in diverse AM-based applications
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3 Integration of nanomaterials in different AM categories

The American Society for Testing and Materials (ASTM) has established standards (ISO/ASTM 52900:2021) that classify AM processes into seven classes based on the method used to create the final products. These classes include binder jetting, directed energy deposition, material extrusion, material jetting, powder bed fusion, sheet lamination, and vat photopolymerization [79]. NMs, typically ranging in sizes from a few to hundreds of nanometers and existing in various forms such as nanoparticles, nanofibers, and nanosheets. These NMs are effectively incorporated into different categories of AM processes through advanced preparation techniques [80]. Innovative methods are used to prepare and introduce these NMs into the AM processes. Techniques like chemical vapor deposition, ball milling, and sol–gel synthesis are employed. These techniques provide a high degree of control over the physical structure and chemical composition of the NMs. This control ensures that the NMs are uniformly distributed within the materials used for AM [81]. This section delves into the seamless integration of nanomaterials (NMs) into diverse AM categories, showcasing their potential to create high-performance components with augmented mechanical, electrical, and thermal properties.

3.1 Binder jetting

Binder jetting (BJT) is an AM technique that operates on a powder-based principle, where layers of powdered materials are selectively adhered together using liquid binder [Fig. 3(A)] [82]. NMs can be integrated into the BJT process by incorporating them into the binder solution or modifying the powder material with nanomaterial coatings [83, 84]. One significant advantage of integrating NMs in BJT is the potential to improve the mechanical properties of the printed objects. Studies have shown that adding NMs can enhance strength, toughness, and stiffness, producing more durable and robust components [85]. For example, [86] demonstrated the successful processing of NMs-loaded inks in BJT, specifically using graphite NPs, by addressing stability, dispersion, and drop formation. By optimizing parameters such as binder mass fraction and particle size distribution, and employing ultrasonic treatment, ink formulations with a maximum particle mass fraction of 10 m% were qualified for binder jetting. These formulations offered improved sintering ability and adaptable material properties in printed parts [86]. Moreover, the integration of NMs can also introduce additional functionalities to the printed components. The incorporation of conductive NMs enables the creation of printed components with electrical conductivity, expanding their applications in fields such as electronics and wearable (bio) sensors [87].

Fig. 3
figure 3

A Schematic diagram of binder jetting process, and B Directed energy deposition process

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However, the successful integration of NMs in BJT requires careful consideration of numerous factors. These factors include the dispersion and distribution of NMs within the binder and their interaction with the powder bed material. Optimizing printing parameters, such as binder composition, viscosity, and deposition techniques, is crucial to achieve the desired material properties and part performance. Additionally, ensuring uniform incorporation of NMs throughout the printed object is essential to maintain consistent and reliable results [85, 88].

3.2 Directed energy deposition

Directed Energy Deposition (DED) is an AM technique that involves the precise deposition of a material using a focused energy source, such as a laser or electron beam [Fig. 3(B)]. [89]. NMs can be integrated into the DED technique by dispersing them within the feedstock material [90]. Incorporating NMs into DED can significantly improve the mechanical properties and expand the capabilities of DED-formed composites. Carbon-based NMs, CNTs, graphene, and graphene oxide (GO), have shown promising results in enhancing metal matrix composites (MMCs) and ceramic matrix composites (CMCs). The addition of these carbon-based NMs has led to improved mechanical performance due to their low density, exceptional strength, and high hardness. GO, in particular, has demonstrated its suitability as a reinforcement in GO-MMCs and GO-CMCs in laser DED processes, enabling the fabrication of composite materials with improved properties. The unique properties of GO, such as improved high-temperature stability and easier dispersion in other materials, make it an appealing choice for integration into DED processes. The addition of GO in composites has shown improvements in microhardness, compressive properties, and mechanical performance [91]. The GO reinforcement mechanisms have also been investigated, shedding light on interactions and microstructural improvements.

Another benefit of incorporating NMs, specifically nano-carbon, into DED processes is their impact on powder delivery behavior. The presence of nano-carbon enhances the convergence and velocity of the composite powder during deposition, resulting in improved quality of the DED-formed composites. This improvement in powder delivery allows for better control over the deposition process, resulting in more precise and accurate manufacturing [92]. The improved powder delivery behavior achieved through nano-carbon decoration contributes to the development of high-quality composites and improves the process development of DED-formed components. Furthermore, in wire-arc DED, a promising technique for producing large-scale, lightweight Mg alloy components, the mechanical properties and corrosion resistance have been limited. To address these limitations, the stress state and microstructure modification of wire-arc DED-fabricated AZ31 Mg alloy has been explored by incorporating laser shock peening (LSP) as a post-treatment technology. The LSP treatment improves corrosion resistance and microstructural properties such as nanocrystallization and the presence of NPs, leading to an overall improvement in the material's mechanical properties, including lower yield strength and improved performance [93].

Additionally, integrating NMs into DED has been explored in fabricating complex integral impellers using 316 L stainless steel. A novel hybrid approach combining DED and subtractive milling has been developed to address the surface quality limitations of DED. This hybrid approach allows for the direct production of internal and complex structural parts with ideal dimensional accuracy. The combination of DED, followed by subtractive thermal milling, results in nearly fully dense specimens with high microhardness and tensile strength. By optimizing the process parameters, exceptional mechanical properties surpassing those of wrought and cast samples can be achieved. The hybrid DED and thermal milling process exhibits the potential to meet industry requirements for 316 L stainless steel components [94]. In summary, the integration of NMs in DED offers tremendous potential for enhancing the performance, functionality, and efficiency of manufactured parts, particularly through improved mechanical properties, enhanced powder delivery behavior and the fabrication of complex structures.

3.3 Material extrusion

Material Extrusion (MEX) is one of the most widely used AM techniques. In this process, a thermoplastic filament is melted in an extruder and then precisely deposited layer by layer onto a build platform, following a predetermined path guided by CAD data [Fig. 4(A)]. MEX includes methods such as fused deposition modeling (FDM) and fused filament fabrication (FFF) [95]. The integration of NMs in MEX has gained significant attention in recent years, and it can be achieved by incorporating NMs into the filament or ink used for printing [96]. This integration can be achieved by dispersing the NMs, such as NPs or nanofibers, within the polymer matrix or binder material. This approach involves the incorporation of nanoscale particles, such as NPs, nanofibers, and nanotubes, into thermoplastic materials during the printing process [97].

Fig. 4
figure 4

A Principle of the material extrusion process, and B Material jetting process

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The incorporation of NMs in MEX offers several advantages. For example, [96] incorporated AgNMs into PLA through a solution-phase method in MEX, resulting in the production of an antibacterial filament for AM. The printed objects demonstrated antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa without significant alteration to the bulk properties of PLA [96]. One of the key advantages of integrating NMs in MEX is the enhancement of mechanical properties. For instance, the addition of CNTs or graphene to the polymer matrix can significantly improve the tensile strength, modulus, and toughness of the printed parts [98]. In a recent study, [99] showed that MEX-printed thermoplastic composite exhibited significantly enhanced flexural strength and bending modulus, surpassing the effects of CNTs or GNPs [99]. In addition, integrating NMs in MEX can enhance the thermal and electrical conductivity of printed parts. By incorporating metallic NPs or carbon-based NMs, heat dissipation and electrical conduction can be significantly improved, making it advantageous for applications in heat sinks, electronic components, and electromagnetic shielding [59].

MEX presented distinct advantages in the expedient fabrication of lightweight and intricately shaped components with minimal waste. Nonetheless, challenges concerning surface roughness, anisotropic behavior, and the accuracy of part shapes had persisted. The introduction of NMs, facilitated by controlled 3D printing parameters and enhanced through laser-based post-processing, effectively addressed these limitations [100]. Undertook the fabrication of PLA/CNT nanocomposites using the MEX technique and subsequently enhanced their properties through the utilization of low-cost CO2 laser cutting. This approach yielded noteworthy improvements in both the accuracy of component shapes and surface roughness [100]. This broadens the potential of nanocomposite-based applications across diverse sectors such as biomedical, aeronautics, automotive, and electronics, showcasing the pivotal role of NMs in augmenting the capabilities of the MEX process.

However, effective incorporation of NMs in MEX requires careful consideration of numerous factors. These include the selection of appropriate NMs, their dispersion and distribution within the filament, and the control of processing parameters to ensure compatibility and effective incorporation. Understanding the interactions between the NMs and the matrix polymer is essential to achieve desired material properties and part performance [101, 102]. In conclusion, although the integration of NMs in MEX shows promise, further research and advancements are required to fully unleash the capabilities of these composite systems in AM.

3.4 Material jetting

Material jetting (MJT) is an AM method that involves the precise deposition of liquid photopolymer materials using multiple print heads equipped with micro-nozzles. These materials are jetted onto a build platform and subsequently solidified through rapid curing using ultraviolet (UV) light, enabling the formation of solid layers with high precision and fine details [Fig. 4(B)] [103]. NMs can be integrated into MJT by incorporating NPs into the liquid photopolymer resin typically used in the process. This nanocomposite resin is precisely deposited onto the build platform and then cured or solidified using UV light, layer by layer, to form the desired object. Incorporating NMs into MJT can significantly enhance the properties of the printed objects. For example, [104] printed carbon nano-onions (CNOs) on polyethylene terephthalate substrates using MJT. The integration of CNOs led to a notable decrease in viscosity (approximately 1.2 mPa.s) compared to that of conventional silver nanoparticle (Ag-NP) ink (approximately 6 mPa.s). This incorporation also facilitated the achievement of an optimal resolution (220 μm) and precise control of layer thickness (resulting in an approximate thickness of 180 nm after 10 printing passes). The printed objects exhibited high electrical resistivity and strong sensitivity to temperature and humidity, making them promising materials for environmental and gas sensors [104]. In another study, [105] developed a scalable graphene NM ink and created 3D graphene–silicone composites using MJT. These composites showcased unique mechanical and electrical properties for applications in wearable and flexible electronics [105].

Moreover, using NMs in MJT has demonstrated exceptional outcomes in fabricating ceramic components. The inclusion of Zirconia (ZrO2) NPs in MJT enabled the fabrication of ZrO2 ceramic components with excellent density, surface quality, dimensional accuracy, mechanical properties, and microstructure representation. The anisotropic characteristics observed in the printed parts, where top surfaces exhibited superior accuracy and hardness while bottom surfaces excelled in fracture toughness, along with the innovative grid-building printing strategy, facilitated effortless support removal, and enabled the production of overly complex geometries. These findings highlight the significance of ZrO2 NPs in achieving glossy surfaces, precise shrinkage control and overall advantages in utilizing nanomaterials in MJT [106].

One of the significant advantages of nanomaterial-based MJT is its ability to print on a wide range of substrates, including plastics, paper, and textiles. This versatility allows for the application of MJT in various industries and opens up new possibilities for functional printing. Additionally, NMs-based MJT is considered environmentally friendly and cost-effective compared to traditional printing techniques. It minimizes material waste, consumes less energy and offers faster production times [107]. However, there are challenges associated with the integration of NMs in MJT that need to be addressed. Achieving uniform dispersion of NMs within the resin is crucial for ensuring consistent and predictable printing outcomes. Furthermore, the presence of NMs in the resin may potentially alter the curing behavior of the materials during the MJT process. Therefore, understanding the interaction between the NMs and the resin and their influence on the curing process is essential for maintaining the desired materials characteristics and achieving optimal printing results.

3.5 Powder bed fusion

Powder Bed Fusion (PBF) is an AM method that involves using a laser or an electron beam to fuse and join powdered material, creating a 3D object layer-by-layer [Fig. 5(A)]. PBF allows for the production of parts with intricate geometrical designs, which may be challenging or unattainable with traditional manufacturing approaches. The PBF process incorporates various techniques, such as direct metal laser deposition (DMLS), selective laser sintering (SLS), selective laser melting (SLM), electron beam melting (EBM), and selective heat sintering (SHS) [108]. The incorporation of NMs into PBF can be achieved in various ways, such as blending with base powder, where the nanomaterial-infused powder is used in the standard PBF process [109]. Alternative techniques involve surface modification of the base powder, in which NPs are affixed to the primary powder particles’ surface [110]. Nanocomposite powders can also be generated through a high-energy milling procedure, resulting in a molecular mixture of the base material and the NM [111]. Also, it may be possible to produce NMs in situ during the PBF process by integrating precursor elements into the powder [112].

Fig. 5
figure 5

A Schematic diagram of powder bed fusion process, and B Sheet lamination process

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The introduction of NMs into PBF technology significantly enhances the mechanical properties of the fabricated parts. For example, [113] demonstrated that the incorporation of graphene–TiO2 nanohybrid into an aluminum matrix during the laser PBF process improved the mechanical properties, wear resistance, and corrosion behavior of the composite [113]. Another recent study showed that the addition of ZrO2 NPs to GNPs in the laser PBF process significantly improved the tensile strength and ductility of the GNPs/Aluminum composite, effectively overcoming the limitations observed in GNPs/aluminum composites. This study emphasized the dual enhancements of strength and ductility achieved by incorporating GNPs/ZrO2 nanofillers in the laser PBF fabricated composite [114]. In addition, NM-based PBF technology can result in improved precision and superior surface quality of the produced components. It enables the formation of structures with complex shapes, high resolution, and remarkable precision, which were challenging to achieve in the past [115]. Nonetheless, it is essential to manage the dispersion of NMs within the powder bed, minimize their agglomeration, and address potential health concerns associated with handling NMs.

3.6 Sheet lamination

Sheet Lamination (SHL) is a versatile AM method that involves the layer-by-layer deposition and bonding of thin sheets of material to create three-dimensional objects [Fig. 5(B)]. Laminated Object Manufacturing (LOM) and ultrasonic consolidation (UC) are two techniques that fall under the category of SL [116]. The integration of NMs within this process has garnered significant attention due to their unique properties and potential for enhancing the performance of printed objects. NMs are dispersed within a polymer matrix and deposited onto a substrate using a precise deposition method [117]. Various techniques, including ultrasonication, high-shear mixing, and surface modification, can be employed to ensure proper dispersion and distribution of NMs within the matrix material [118]. Additionally, process parameters such as printing temperature, layer thickness, and printing speed are crucial to maintain the integrity and homogeneity of the printed nanocomposite structures [119].

One of the key benefits of integrating NMs into SHL is the enhancement of mechanical properties [120]. Exhibited that the integration of graphene NMs in SHL significantly enhanced the mechanical properties of continuous carbon fiber reinforced polymer composites (CFRPCs), surpassing existing AM-produced structures. Here, the use of graphene as an interface modifier improved interfacial bonding strength, resulting in increased lap shear strength, flexural strength, and modulus, making it a promising scalable manufacturing method for high-performance CFRPCs in various industrial applications [120].

Moreover, the incorporation of NMs in SHL enables the development of functional materials with tailored properties [121]. Demonstrated that the combination of graphene NMs and SHL allowed for the fabrication of a diverse range of 3D graphene objects. These objects exhibited desirable properties, including excellent electrical conductivity and mechanical strength, making them well-suited for applications in energy storage and flexible electronic sensors [121]. Similarly, the use of ceramic NMs can enhance the thermal stability and wear resistance of printed objects, making them suitable for high-temperature applications [122]. These findings highlight the potential of nanomaterial-based SHL techniques for producing advanced functional structures.

3.7 Vat photo-polymerization

Vat photo-polymerization (VPP) is a popular AM method that utilizes light-induced polymerization to fabricate complex three-dimensional objects [Fig. 6]. It is a fundamental process that involves solidifying photosensitive polymers using laser, light, or UV radiation. Two notable techniques based on VPP are stereo-lithography (SLA) and digital light processing (DLP) [123]. NMs can be included in VPP by incorporating them into the resin formulation, ensuring uniform dispersion and optimizing their concentration to achieve desired properties and performance [124]. The addition of NMs like CNTs, graphene, and metal NPs to the polymer matrix offers the opportunity to enhance mechanical strength, conductivity, and heat dissipation properties [125]. For example, [126] successfully fabricated high-performance ordered graphene/polymer composites using an electrically assisted continuous VPP technique. The incorporation of graphene nano-platelets improved the mechanical properties, ductility, and electrical conductivity of the composite materials, showcasing their potential for applications in self-sensing structures [126].

Fig. 6
figure 6

Schematic illustration of vat photopolymerization process

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Recent studies have shown that the integration of NMs in VPP offers new opportunities for the development of functional and high-performance components [127]. Demonstrated a straightforward and cost-effective method for fabricating nanocomposites with improved mechanical strength and bacteria-inhibiting properties by adding Cuprous Oxide (Cu2O) NPs into the VPP technique. The incorporation of Cu2O NPs at lower ratios significantly enhanced the mechanical response and antibacterial performance of the materials, making them well-suited for various engineering and medical applications [127]. In another recent study, [128]. fabricated controlled micro-/nano-dual-scale super-hydrophobic structures by integrating MWCNTs in electrically assisted vat photo-polymerization (e-VPP). The MWCNTs enhanced super-hydrophobic properties, mechanical strength, and liquid surface attaching forces in biomimetic systems. This research offers promising applications in droplet control, micro-droplet reactors, non-loss transportation, antibacterial surfaces, water robots, and oil–water separation through optimized interfacial performance via material composition and distribution adjustment [128].

Furthermore, it is possible to fabricate objects with combined functionalities by integrating NMs with different properties into the resin [129]. Showed that the addition of ZnO NPs in VPP reduces light penetration and prevents unwanted curing, leading to the formation of stronger cured layers and the ability to print overhanging structures without the need for support. This research exhibited the potential of ZnO NPs to replace conventional photo-absorbers, thereby enhancing dimensional accuracy and preserving the mechanical properties of printed parts [129]. In another study, [130] successfully incorporated magnetic NPs into a photopolymer resin, enabling the printed objects to possess structural and magnetic properties [130].

In addition, the integration of NMs in VPP not only improves mechanical and functional characteristics but also enhances the printing process itself. In their study, [131] demonstrated the crucial role of AuNPs as efficient photo-initiators in VPP. The researchers synthesized AuNPs in situ within the polymer matrix, simplifying the printing process by eliminating the need for solvents, surfactants, and purification steps. The resulting nanocomposites exhibited unique plasmonic properties, indicating their potential applications in surface-enhanced Raman spectroscopy (SERS) detection and the precise design of sub-millimeter resolution objects in plasmonic-based platforms [131]. Despite these advancements, challenges persist in integration of NMs in VPP. It is crucial to ensure uniform dispersion of NPs within the resin to maintain consistent properties throughout the printed object [124]. Besides, careful optimization of the selection and concentration of NMs is essential to prevent any adverse negative impact on the printing process and the final properties of the printed objects.

Overall, the incorporation of NMs into different AM techniques introduces notable benefits but also raises concerns regarding their proper management and safety. This necessitates a comprehensive evaluation of the handling procedures and safety measures associated with the integration of these tiny NMs. It is imperative to ensure that the NMs are dispensed, mixed, and processed within controlled environments to minimize potential hazards. Additionally, a thorough understanding of the potential health and environmental impacts is essential in order to establish guidelines and protocols that ensure the secure and responsible use of NMs in AM processes.

4 Properties of nanomaterial integrated AM products

Traditional AM products, typically made from a single material, often suffer from inadequate robustness, resulting in part failure even under minor stress [42]. However, integrating nano-fillers can address this limitation and enhance properties. The combination of nanotechnology and AM offers opportunities to generate innovative nanocomposites, overcoming the capabilities of traditional methods and opening new possibilities. Nanoscale entities possess distinctive characteristics such as unique electrochemical, thermal, friction and wear resistance, optical, and antibacterial properties, which differ from those of bulk materials or molecules [132]. For instance, AuNMs demonstrate unique biocompatibility, reduced cytotoxicity, corrosion resistance and size-dependent optical properties due to collective electrons oscillation upon interaction with specified wavelengths of light [133]. Silver, gold or bimetallic NMs have demonstrated effective antibacterial properties against Gram-positive and -negative bacteria due to their physiochemical properties, synergistic effects and diverse action mechanisms [134]. These characteristics are significantly influenced by the composition, size, high surface area to volume ratio (quantum effects) and geometry of the NMs. Furthermore, NMs can streamline production processes and enhance the characteristics of specific applications, unlocking novel possibilities for complex structures and forms [135].

Recent studies have demonstrated that integrating NMs with AM can significantly enhance the value of the final product. The addition of NMs as fillers can positively impact mechanical and magnetic properties. For instance, [136] incorporated laser PBF AM to develop a nickel-based alloy (Haynes 230) with potential aerospace and defense applications. MWCNT was incorporated as the reinforcement filler to improve performance. The nickel nanocomposite filled with 2.5% MWCNT demonstrated superior relative density (99.36%), modulus of elasticity (34 ± 2.1 msi), yield strength (164 ± 2 ksi) and ultimate strength (197 ± 5.4 ksi) compared to the control nickel [136]. In another study, [137] combined antibacterial NPs with a photo-curable resin using VPP AM to produce an enhanced product with improved performance. Titanium dioxide (TiO2) and ZnO NPs were separately added to a standard UV-curing photopolymer. While both products demonstrated antibacterial properties, ZnO NPs showed superior mechanical properties. The nanocomposite with ZnO NPs demonstrated substantial improvement of 14.3%, in Young’s modulus, 42.2% in tensile strength and 15.8%, in abrasion resistance, compared to the photopolymer without NPs [137]. [138] proposed a metallic NMs filled nanocomposite produced through ME, exhibiting outstanding magnetic properties. Fe3O4 magnetite NPs were added to polyethylene glycol-polyvinyl butyral (PEG-PVB) polymer matrix and silicone gel to introduce magnetism. The nanocomposite with PEG-PVB demonstrated superior results in terms of remanence (Mr/Ms = 0.185), saturation, coercive field (15,1–20,9 mT) and squareness (+ 25%), compared to nanocomposite with silicone gel or non-composites [138]. The nanocomposite consisting of acrylonitrile butadiene styrene (ABS) and a low loading (0.06 wt.%) of GO demonstrated enriched multifunctional properties. By maintaining stiffness, the addition of GO enhanced the strength, strain-to-failure, and toughness of the thermoplastic. These improvements make the resulting nanocomposites suitable for various static and dynamic loading applications, offering increased versatility [139].

The presence of photothermal sensitizers (PTS) in printed materials poses challenges in terms of color and appearance, limiting their market applications. To address this issue, Powell et al. (2018) investigated the use of gold nanorods (AuNRs) in different polymer matrices to control the optical properties of AM objects. Their findings opened up possibilities for utilizing low-power light sources to sinter plasmonic NPs, enabling the production of vibrant and functional AM items with a more uniform white appearance [140]. Relatedly, [141] successfully developed a nanocomposite by incorporating a small quantity of AuNPs into a PVA matrix, resulting in a dichroic effect without compromising the characteristics or printability of the polymer. The inclusion of AuNPs within the polymer produced a reflective brownish color and a transmitted purple color, offering exciting opportunities to explore the optical properties of NPs and integrate them into their artistic ventures [141].

The exceptional biodegradability, biocompatibility, and antibacterial properties exhibited by various NPs make them highly suitable for the fabrication of biomedical implants using AM techniques [142]. Explored the antibacterial mechanisms of AgNPs and their effects on osteogenic cells to improve the biocompatibility of AgNPs. Their findings recommended the utilization of advanced 3D printing-based implant modification technologies [142]. In a recent study, [143] successfully developed a multifunctional scaffold with controlled dual-stage drug release, incorporating GO nanosheets. This scaffold enabled effective antibacterial therapy and bone regeneration in infected bone defects, offering a promising strategy to address implant-related bone infection and surgical failure [143]. Similarly, [144] fabricated a 3D-printed nanocomposite scaffold using PCL, hydroxyapatite (HA) NPs, and di-acrylate poly-(ethylene glycol) (PEGDA). The scaffold exhibited interconnected channels, appropriate porosity for osteoblast migration and proliferation, and demonstrated non-cytotoxicity, holding significant potential for bone regeneration and offering new possibilities for 3D tissue substitutes [144]. Recent times have seen a significant rise in interest in the fabrication of NM-based AM drug dosing studies [145]. Developed drug carrier NPs using cannabidiol (CBD) and cannabigerol (CBG), which were incorporated into 3D-printed films made from sodium alginate. These films showed initial wound healing enhancements within 6 h, satisfactory cell viability at 0.1 mg/mL concentration for 24 h and CBG NPs remaining safe even after 48 h. The fabricated films exhibited excellent release profiles and thermal stability and achieved complete drug release within 24 h, showing promise for wound healing applications [145].

The incorporation of NMs in AM enables the fabrication of highly conductive nanocomposite inks for use in smart wearable sensors [146]. Developed highly conductive AM inks using CNT/PLA nanocomposites. The incorporation of these nanocomposites resulted in a significant increase in transparency, reaching up to 75%. Furthermore, the printed structures exhibited a remarkable improvement in electromagnetic interference (EMI) shielding effectiveness, with an approximate increase of 200%. These findings have significant implications for applications that require transparent materials with enhanced EMI shielding, such as airplane technologies, handheld electronic gadgets, and smart wearable textiles [146].

The significance of NMs implementation on the properties and performance of the additively manufactured goods is represented in Table 2.

Table 2 Impact of NMs on the properties and performance of the AM products
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5 Prospects of AM using nanotechnology

The incorporation of nanotechnology with AM has the potential to revolutionize various industries, including healthcare, food, fashion, construction, and architecture (Fig. 7). This integration opens new horizons for innovation, customization, and sustainability in these sectors. In this section, the promising prospects of AM using nanotechnology in these fields will be explored.

Fig. 7
figure 7

Significance of nanomaterial-based additive manufacturing for application in different industries

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5.1 Human healthcare

The integration of NMs in AM is leading to significant advancements in the healthcare sector, unlocking immense potential across a wide range of applications. This technique enables the creation of intricate and personalized structures, with applications in prosthetics and implants customized for individual patients, as well as the generation of organ and tissue constructs [15, 157]. The incorporation of NMs such as CNTs, metallic NPs, and graphene enhances the mechanical strength, biocompatibility, and biofunctionality of the 3D printed structures, offering new opportunities for personalized therapies and patient-specific treatments [20, 158].

3D bioprinting, a prominent area of research within tissue engineering, focuses on creating biological materials, regeneration processes, and manufacturing biodegradable scaffolds with enhanced properties. The integration of NMs and NPs in bioprinting opens up exciting possibilities for applications in nerve repair, targeted drug delivery, cardiovascular regeneration, and numerous other potential advancements [159]. In orthopedics and dentistry, the synergy between NMs/NPS and AM has resulted in the creation of implants tailored to the specific anatomical and biomechanical needs of individual patients, leading to improved patient comfort and faster recovery times. This advancement has substantially impacted orthopedic and dental practices, offering customized solutions for enhanced patient well-being and quicker recuperation [160]. In drug delivery, 3D-printed devices incorporating NMs can facilitate controlled and targeted drug release, enhancing treatment efficacy while minimizing adverse effects [161]. Additionally, printing appropriate NMs allows for the extraction of renewable energy from body glucose, presenting a viable method for energy harvesting [162]. Recent advancements in the fabrication of 3D-printed nerve guide conduits, utilizing state-of-the-art bioinks that incorporate NMs, have shown promise in the treatment of peripheral nerve injuries [163].

Nonetheless, the adoption of AM incorporating NMs in the healthcare sector comes with challenges. There are issues related to the potential toxicity of specific NMs, the durability of 3D-printed frameworks, and regulatory considerations that need to be tackled. Consequently, rigorous scientific research and cross-disciplinary collaboration are crucial to address these challenges and fully realize the potential of this technology in human healthcare.

5.2 Fashion industry

The emerging of NM-based AM has brought significant advancements to the fashion industry. This innovative technology enables the crafting intricate designs and patterns, opening up new possibilities that traditional manufacturing techniques cannot match [164]. By utilizing NMs, such as nano-fibers, nano-composites, nano-coatings, and nano-finishing, clothing items can achieve superior attributes, including vivid color intensity, enhanced durability, and self-cleaning capabilities [165]. In the textile industry, NMs are printed to make 3D garments, improving mechanical characteristics and introducing technical functionalities like conductivity and UV protection [166]. In addition, the utilization of NMs in AM in the fashion industry has the potential to contribute to sustainable textile production methods through waste reduction and environmentally friendly materials [167]. The integration of NMs into AM processes within the fashion industry has also paved the way for the development of wearable technology, opening exciting opportunities in this field. By leveraging conductive NMs in AM, it is possible to fabricate flexible smart wearable e-textiles with enhanced functionality. These e-textiles can interface with electronic systems, enabling a wide range of applications, including healthcare monitoring, fitness tracking, sports analysis, fashion design, and interactive gaming experiences [166, 168]. The ability to create customized garments and accessories to meet individual needs and preferences is another promising aspect of NM-based AM in fashion [169].

Despite the potential benefits and advancements, there are challenges that need to be addressed. The risks associated with the use of NMs, such as potential toxicity and environmental impact, require further research. Moreover, the industry needs to overcome technical challenges in scaling up production and maintaining cost efficiency. Regulatory issues related to the use of nanomaterials in fashion also need to be addressed.

5.3 Construction and architecture industry

The application of NM-based AM has transformed the construction and architecture industry. This progressive technology facilitates the production of intricate structures with higher precision compared to traditional construction methods [170]. The use of NMs, like CNTs and graphene, significantly enhances the strength, durability, and thermal properties of building materials, promoting the development of more robust and energy-efficient constructions [171]. Moreover, the adoption of NM-based AM in construction and architecture offers several advantages. The ability to produce custom designs according to specific requirements reduces waste, aligning the construction industry with sustainable and eco-friendly practices [172]. In addition, advancements in printing technologies for large-scale structures have the potential to accelerate construction processes, resulting in significant cost and time savings [173]. However, the deployment of NM-based AM in the construction and architecture industry also presents several challenges that need to be addressed. These include potential environmental impacts of NMs, adherence to building regulations and codes, and technical obstacles associated with scaling production. Therefore, it is imperative to conduct further research to address these issues and ensure the safe, effective, and sustainable application of this technology in the construction and architecture industry.

5.4 Food science and fabrication

The integration of NMs in AM has emerged as an innovative tool in food science and fabrication, enabling the creation of complex food structures and tailored nutritional compositions that enhance the consumer experience. The incorporation of edible NMs, such as nano-fillers and nano-additives, into food matrices, several properties of the food product, including its color, flavor, texture, and nutritional content, can be improved [174]. Furthermore, NMs have potential antimicrobial properties that can enhance food safety and extend shelf life [175]. The implementation of NMs in AM processes can also aid in embedding bioactive compounds, providing control over their delivery mechanisms and consequently enhancing the safety and quality of food [176]. In addition, AM facilitates the formulation of tailored nutrition schemes, aligning with the expanding field of personalized healthcare and wellness trends. The capability to produce custom food items that meet unique dietary needs is one of the potential benefits of incorporating NMs in AM [177]. Although considerable progress has been made in this area, it is crucial to address the potential drawbacks linked to the utilization of NMs in food. Concerns regarding human health, environmental effects, and regulatory matters regarding the deployment of NMs in food are significant and require careful consideration. Therefore, further scientific exploration is necessary to mitigate these concerns and establish safe and sustainable methodologies for the integration of NMs in AM within food science.

6 Challenges of nanomaterial-based AM

The integration of nanotechnology and AM enables the fabrication of novel nanocomposites that complement and enhance existing techniques. The ability to scale materials down from macro to nano or transition from bulk to molecular dimensions empowers the modification of their fundamental characteristics. Additionally, the incorporation of nanohybrids introduces unique attributes that were not present in the original components, opening up possibilities for a broader range of applications and increased functionality. However, despite advancements in this field, significant knowledge gaps about the utilization of NMs in AM still exist. Specifically, there is a lack of information regarding the intricate interactions between nanohybrids and the materials employed in the printing process. The performance of printable composites can be influenced by the physical and chemical processability at the micro or nano-level during incorporation. Factors related to physical–chemical processability are primarily associated with the unique reactivity of nano-scaled particles due to their reduced size and increased surface area [178]. There are several additional limitations to consider when integrating NMs into AM. These include financial implications, environmental friendliness, potential health and safety effects of nanohybrids, and the need for special treatment during processing [179]. Figure 8 provides a comprehensive overview of the critical challenges that need to be addressed for the successful integration of NMs into the AM process.

Fig. 8
figure 8

Challenges of nanomaterial integration in the additive manufacturing process

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The replacement of prevalent technologies in bulk production poses a significant challenge for the integration of nanocomposites developed by AM. The fragile nature of the products limits their application in various fields [180]. Commercializing nanocomposites produced by AM is particularly challenging due to factors such as the high cost of nanoscale material design, volume production consistency, limited reproducibility, and thermal and oxidative instability [181]. Further, the customization of materials for specific AM methods and products can lead to additional costs, including the establishment of secondary producers of raw materials, such as powder processing service providers or an integrated powder processing unit and the increased energy consumption associated with laser usage [182].

Incorporating NMs like CNTs, nanowires, and quantum dots into host matrices, including polymers, metals, and ceramics, using AM can strengthen the production capabilities of nanocomposites. However, AM processes have downsides when it comes to incorporating NMs. These downsides include nozzle clogging, aggregation within liquid media, increased viscosity in the MJ and VPP, nano-powder agglomeration, low rheological properties in PBF processes, and poor surface texture of printed objects [183]. NMs are often prone to agglomerate, leading to issues such as particle collision, growth at elevated temperatures, particle attraction due to van der Waals, covalent or metaling forces, and adhesive nature, which compromise product consistency and increased nozzle blockage [184]. Accurate printability of the printing paste is vital to overcome these difficulties. It is necessary to achieve an even dispersion of filler NMs within the matrix paste to ensure uniform properties and minimize the risk of nozzle clogging.

Formulating inks with bio-interactive elements is challenging as it requires achieving a stable ink that maintains the functionality of the bio-interactive substance throughout the printing and is well-fitted with the MJ. Challenges encompass maintaining the controlled and consistent performance of the nano biomaterials in terms of vascularization, nutrient-gas exchange, biodegradability, and biocompatibility [185]. Biocompatibility is particularly important since it relates to living cells and tissues that may be sensitive to the printing method. Additional challenges arise from possible damage caused by shear stresses during the jetting process, as well as issues such as sedimentation, agglomeration, adhesion to internal print head surfaces, crystallization at the nozzle, and various aspects of rheology such as surface tension, viscosity, and non-Newtonian behavior. Furthermore, the modification of the print head may be crucial, involving adjustments in geometries, the application of hydrophobic or hydrophilic coatings, and the selection of suitable substances to prevent issues like wetting or adhesion to the print head nozzle and nozzle plate when working with specific nano biomaterials. To preserve the functionality of NMs, it may be necessary to closely monitor humidity and temperature levels. Special attention should be given to effectively preventing potential issues related to disinfection and cross-contamination [186].

The introduction of NMs and nanohybrids in PBF can result in higher levels of porosity and increased surface roughness when compared to components printed without the inclusion of NMs. Reasons for this include disrupted powder bed bonding flowability due to the presence of NMs, non-uniform dispersion of the NMs in the matrix, interference of laser-powder bed interactivity, powder bed contamination due to agglomeration, and partial fusing or thermal mismatch of the nanohybrid components [187]. Most of these difficulties can be attributed to the diverse nature of the substances utilized. Furthermore, NMs tend to settle in the powder bed, resulting in non-homogeneous fabricated printed parts [188]. In the case of core–shell hybrid nanostructures, where the core is composed of NMs and the shell contains the printing substance, it exhibits a notable increase in the density of the resulting components. This matter will extend various new printing objects that acquire distinctive properties such as electrical, thermal conductivity and hardness while concurrently producing nanocomposites as dense as nanostructure-free printed components [189].

Budgetary constraints also play a crucial role in implementing AM on an industrial scale, particularly when incorporating nanohybrids. The considerable investment required for machinery and materials, due to their high costs, poses a significant challenge. Other than purchase and installation expenses, high energy consumption, lower productivity, and the cost associated with NMs preparation can mount up to a substantial economic toll [190]. [182] presented a radar graph comparing PBF to traditional manufacturing processes in financial and non-financial aspects [Fig. 9] [182].

Fig. 9
figure 9

© 2018, Elsevier

A radar chart of traditional industrial methods vs PBF (scale 0–9, with 9 being the extremely substantial factor), reused with permission from [182]

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The environmental stability and disposal of nanohybrids pose challenges in terms of their eco-friendliness. The small particles at the nanoscale can become toxic to living organisms as they can be easily absorbed on the outer surface and enter living tissues or body fluids as foreign materials [191]. Certain NMs, like metal and alloy NPs, tend to undergo oxidation when exposed to air, resulting in the modification or potential loss of their unique properties [192]. Adding to that, their extremely small sizes contribute to challenges related to higher mobility, bioaccumulation and disposal [193].

Evaluating the quantities of nanohybrid materials can be challenging due to the inherent properties and processing method employed in their creation. The final characteristics of the nanohybrid are directly influenced by the constituent nanocomponent, necessitating the adoption and validation of a proper nanoanalytical evaluation system for assessing the final nanohybrid [194]. The use of multilayer coatings is an example that highlights the challenges in assessing the toxicity of nanohybrids based on their constituent ingredients. For instance, coating ZnO NPs with an amorphous nano-scale layer of silicon dioxide can reduce the dissolution of ZnO NPs while preserving their optical capabilities, resulting in a significant reduction in DNA damage potential [195, 196].

The inclusion of nanohybrids also alters the processing conditions in AM, necessitating adjustments to AM processing parameters. For instance, when employing a VPP method with nanohybrids, it is crucial to select nanohybrids suitable for the specific wavelength of the UV light source [197]. The ability of NMs to absorb or scatter UV radiation can impact the cure depth of the VPP. Therefore, a comprehensive characterization of nanohybrid photopolymer solutions is required to understand the specific influence of different NMs and UV wavelengths on the cure depth and cure shape profiles [189].

Despite the ability of AM to effectively address scalability concerns in the fabrication of nano-enabled products, it is important to recognize that there is no universally applicable solution that fits all circumstances. Precise selection of precursor raw materials is imperative to ensure compatibility with a specific AM method. Furthermore, it is essential to ensure that the fabricated item remains structurally sound and maintains its integrity throughout its entire service period, preventing potential risks comparable to a vulnerable "house of cards" situation [182]. Reproducibility is another key concern with AM. Because each item is constructed layer by layer, the quality of parts produced by different machines or the same machine at different periods should be comparable. Conversely, AM may not be well-suited for one of its most promising applications, namely the production of parts for critical and high-demand applications. Maintaining parameters at a proper level for different materials and assuring repeatability and reproducible product quality are complicated and daunting tasks but inevitable for the success of nanomaterial-based AM [196].

7 Future directions

As research progresses, the abundance of products from AM using nanotechnology is expected to increase. Recent times have witnessed the emergence of numerous opportunities and potential applications in diverse fields such as medicine, manufacturing, material sciences, energy, information technology, and environmental sciences. Notably, noteworthy progress has already been made in healthcare, where nanodevices and nanostructures fabricated through AM have demonstrated their effectiveness in monitoring, repairing, constructing, and regulating human biological systems. The development of nanotechnology-based drugs and drug delivery systems has also yielded noteworthy outcomes. Promising areas of future research in healthcare encompass tissue and organ development, customization of prostheses and inserts, creation of physical models, design of tailored drug dose structures, efficient drug conveyance, drug screening, and breakthroughs in drug research. These avenues hold enormous potential for further exploration and advancement in healthcare.

The integration of NMs into AM for the food industry has led to significant advancements, particularly in the creation of intricate shapes. Biopolymer NMs, such as cellulose, hemicellulose, gelatin, alginate, starch, agarose, and chitosan, are particularly appealing due to their non-toxicity, edibility, abundance, and bioactivity, making them suitable for 3D food printing applications. While AM technology is currently utilized in military and space food production, further research is needed to explore the rheological qualities, thermodynamic properties, and binding mechanisms, as well as optimize pretreatments and post-processing procedures for NMs-based 3D printed food manufacturing. Investigating these aspects will contribute to advancing the field and unlocking the full potential of nanomaterial-based AM in the food industry.

Incorporating NMs in AM holds promise for various applications, particularly in biology and medicine. However, manufacturing repeatability and scalability challenges need to be addressed to facilitate the industrial use of NMs produced through AM. There are still many unanswered questions regarding the interactions of NMs with molecules in the blood or inside the cells, as well as the ability of hybrid NMs to deliver drugs across the blood–brain barrier.

The incorporation of NMs in AM allows for the creation of novel nanocomposites with distinctive properties and functionalities. However, there are still considerable gaps in our understanding of interactions between nanohybrids and printing media and the need for standardized process parameters and synthesis techniques to ensure consistency in manufacturing various nanohybrids [189].

Ink in AM can be used in diverse fields, ranging from surface coloration to imparting conductivity. For instance, constituents of deliberately formulated ink can deliver functionalities in polymer-based materials, such as developing microelectrodes and generating bio-collaborative elements for biochemical investigations. Conductive inks can potentially construct conductive pathways for integrating electrical components in microfluidics [198]. Formulating conductive inks using NM suspensions offer benefits such as rapid drying and ease of distribution in water.

To ensure optimal flow through printing nozzles, research is warranted to ascertain how various nanohybrids impact viscosity. Additionally, changing surface tension due to nanohybrids is another area that needs investigation. To solve the agglomeration problem, organic linker molecules could be explored to functionalize NMs. Linkers refer to organic molecules that can be used to functionalize NMs and prevent them from agglomerating. When implanted in the printing media, linkers can keep particles separate. They act as spacers between the NMs, preventing them from clumping together and enabling better dispersion in the printing media [199, 200]. Therefore, the use of linkers is a promising strategy to address the agglomeration problem associated with NMs and improve their dispersion in 3D printing media. This improvement is crucial for the development of advanced NMs-based AM applications.

Considering the environmental impact of nanohybrids requires a comprehensive assessment of their entire life cycle, from synthesis to disposal. It is important to follow standard policies and conduct extensive investigations throughout the entire process. Nanohybrids present different physicochemical properties compared to their individual NM constituents, and it is essential to evaluate if, and under what circumstances, nanohybrids cause new environmental hazards due to these transformed characteristics.

Advanced processing techniques, such as personalized geometry-specific solutions provided by AM, offer significant advantages over traditional technologies. Furthermore, the integration of innovative hybrid NMs through novel processes, along with the utilization of biomedical properties and novel composite materials, enhances the capabilities of AM. However, further research, experimentation, and comprehensive investigations are imperative to fully comprehend and effectively utilize these benefits. Future research endeavors should focus on exploring the rheological and thermodynamic properties of NMs, elucidating binding mechanisms, optimizing pretreatments, and developing efficient post-processing methods for AM food fabrication. In the realm of human healthcare, promising research prospects lie in the customization of tissue and organ creation for prostheses, inserts, and physical models, as well as the development of tailored drug dose structures, advancements in drug conveyance, drug screening techniques, and groundbreaking discoveries in drug research. These research directions will unlock the full potential of integrating NMs into AM, fostering innovation across diverse fields.

By addressing these research areas and challenges, we can better understand and harness the potential of NM-based AM, leading to advancements in various industries and applications.