Advanced 3D printing-based triboelectric nanogenerator for mechanical energy harvesting and self-powered sensing

Abstract

Triboelectric nanogenerator (TENG) is an innovative technology that it has sparked a revolution in distributed energy supply and self-powered system. Integration of advanced TENG with burgeoning 3D printing (3DP) technologies fosters the emergence of 3DP-based TENGs. It will inevitably promote the rapid development and widespread applications of next-generation portable electronics and multifaceted artificial intelligence. However, due to the different subject field between researchers specializing in TENG and those good at 3DP, they are not always a perfect combination. It is rather difficult to achieve with both excellent electrical properties and outstanding practical performances. For that, a review is presented more systematic and comprehensive of 3DP-based TENGs for the first time. In which the quantitatively statistics and correlation data of research progress are given, such as publications, 3DP technologies and materials, structure designs and functionalities, working modes and mechanisms, output performances, unique advantages, potential technical challenges and promising application fields that can impede their sizable production and applications are discussed. It is hoped that this review will not only deepen the intersection and amalgamation between 3DP and TENGs, but also push forward more in-depth research and applications of future TENGs.

Introduction

Nowadays, the rapid advancement of multifunctional electronic devices and energy technologies are changing every aspect of our daily life and the way of working, as it confirmed that the electricity and its way of supply have played the most critical role in the history of the technology revolution. Starting from the electromagnetic induction discovered by Faraday in august 1831 [1] mechanical energy was converted into electric power that can be generated by the burning of fossil fuels, wind, hydropower and nuclear fission, which has marked the mankind has entered an entirely new age of electricity. And invented solar cells based on photovoltaic effect is a kind of green energy that has succeeded in converting sunlight directly into electrical energy [2] which is widely used in the fields of energy storage and aerospace industry. In a way, with the development and utilize of electricity, this has symbolized the progressive degree of human society and the developed level of science and technology. However, with the rapid consumption of finite fossil fuels as well as people fully have woken to the importance of environmental protection, in which the traditional centralized and ordered energy supply patterns based on power plants are incompatible with the present development of distributed energy and portability electronic devices [3]. Besides, a comprehensive advantage of light weight, flexible, miniaturization and portability is needed. As the information age of applied 5G and 6G is coming, billions of things must be connected with various sensors for large data, artificial intelligence, face recognition, block chain, and many other new technology development and application [4]. These rapid advance mobile, individual, randomly, massively of the distributed and portability electronic devices also require the corresponding matched of energy supply pattern. In fact, it turns out that the unreasonable way of energy supply patterns and energy structure lead to the current development dilemma, i.e. one of the more prominent of them is frequent charging and its slow process [4]. Portable energy storage technologies are the most efficient solutions, that may be to provide a reasonable way for the above predicaments. For portable power sources, the most effective way now is to utilize the small scale, high energy density and rechargeable energy storage devices, which mainly include conventional solid-state battery, electrochemical capacitor, ultracapacitor and lithium ion battery, etc. However, with the inherent shortcomings of frequent charging, limited storage capacity, short service lifetime, certain safe hidden trouble, and serious environmental hazards, above all the electricity storage of these power sources still draws from conventional supply patterns. So that, these are also not fundamental solution for future distributed and portability electronic devices. Furthermore, from long-term development objective and environmental perspective, power acquisition directly from our natural environment is the ideal choice for future energy supply [5], [6]. This idea was first proposed by Z.L. Wang in 2006 that is invented nanogenerator (NG), this technology is now well received and recognized worldwide [7], [8]. Though the existing mature energy technologies show that have better performances for generate electricity, yet they are generally excessive reliance on external factors and supporting conditions, such as abundant sunshine, the proper temperature range and active catalyst, making them difficult to be effectively utilized on the energy supply of distributed and portable patterns.

With continual advances in energy nanotechnology, triboelectric nanogenerator (TENG, by Z.L. Wang discovered in 2012) as a revolutionary of mechanical energy harvesting technology stands out from the rest with its own advantages and stand-out features [9], [10]. It makes possible to expediently recycle and converts mechanical energy into electrical energy by the coupling effect between the contact electrification and electrostatic induction, which is through the periodic contact-separation between two triboelectric materials with different abilities of gaining or losing electrical charges. This new approach to harvest mechanical energy can high-efficiency energy conversion low-frequency mechanical energies from our living environment, and is capable of supplying electricity for distributed and portability applications [11], [12], [13], [14]. TENGs have received increasing interest among researchers in recent years and have been regarded as effective technological means to harvest mechanical energy and self-powered sensing, which have broad application prospects in distributed and portable energy technology, such as motion tracking, physiological monitoring, medical rehabilitation, intelligent humanoid robot and human–computer interaction [12], [13], [14], [15], [16], [17], [18], [19], [20]. Particularly, when advanced TENGs in combination with emerging 3D printing [21] (3DP, or umbrella term additive manufacturing technology gained popularity in the 2000s) contributes to the emergence of a series of revolutionary mechanical energy harvesting devices, i.e., termed 3DP-based TENGs, which make full use of their respective merits and will inevitably promote the rapid development of new era energy harvesting technology and self-powered sensing. This technical approach was first proposed by Z.L. Wang in 2018, while report a practical, ultraflexible and three-dimensional TENG that is capable of driving conventional electronics by harvesting biomechanical energy [22]. It is now well received worldwide and 3DP has been utilized to fabricate TENGs [23]. Fig. 1 demonstrates several kinds of 3DP-based TENGs as well as their structure and a more diverse set of real application, such as the motion of the human, vibration energy, wind energy and blue energy from the natural environment. It can be found that portable power socrce and self-powered sensing are their two main applications. It is usually used for distributed energy supply and active sensing in many aspect such as action, motion, pressure, tactile, healthcare, safe guarding, information acquisition, signals transmit of big data and more powerful human–machine interacting. The number of published research papers about 3DP-based TENGs from the top-ranked countries are demonstrated in Fig. 1b. The overall situation of publications about 3DP-based TENGs was investigated and annual number were statistical analysed, as shown in Fig. 1c. Although related researches are just starting, according to the latest published resultes, it is shown that 3DP-based TENGs studies range is wide, applied foreground is hopeful, simple structure, ease of operation and integration, huge potential of research. Due to the differences of mechanical energy in the environment, so have to optimizing design and select suitable process for the fabricated 3DP-based TENGs to be applicable to real-world applications. As technology develops, it can be believed that 3DP-based TENGs will bring new field of research and more possibilities for next-generation low-power electronics, and lead the way of people’s life toward a more intelligent and portable developing direction in the near future.

As technology advances and more prototypes of 3DP-based TENG have been largely fabricated and extensively reported, several fundamental issues must finally confront together, such as current research status and practicability, 3DP technologies classification and characteristics, 3DP materials selection and preparation, integration methodology and structural design, working mechanisms, electrical properties improvement methods and promising application occasions, etc., at the moment these are still not comprehensively and systematically overviewed. And in particular, the basic knowledge of 3DP and the approaches to efficient integration TENG energy harvesting technologies with 3DP are also not roundly and comparatively summarized. These urgent issues have greatly bound the development of commercialization and industrialization of 3DP-based TENG, which results in a large gap between the best current devices and real applications.

Herein, we cover the recent progress of 3DP-based TENGs for both energy harvesting and self-powered sensing in the natural environment, discuss the major research challenges and also point out a clear direction for future development. We expect this review article to greatly benefit the related developers and research teams. Our objectives not only gave a summary report for the research situation and applications, but also more importantly is to provide a reference for future research.