Fig. 1. High-density thermopneumatic microvalve arrays for sample processing in PCR chips. (A) separation (A, B) and combination (B, C) of particle in a microchannel network; (B) Cross-section of a microvalve and a photodiode used for particle sensing in the channel network. Source: Baechi et al. (2001). [Fig. 1 (A) and (B) reprinted with permission from Baechi et al. (2001). Copyright (2001) Kluwer Academic Publishers.]

Fig. 2. (A) Operation principle of the SMA microvalves. Source: Kohl et al. (2000); (B) Principle of chip-integrated microvavles for sample exact positioning (A — the pressure-driven fluid plug (blue) passes the hydrophobic ventilation hole (diameter = 800 μm) and stops immediately after it; B — the air can escape through the hole; C-After closing the hole by a piston the sample plug can move on). Source: Münchow et al. (2005). [Fig. 2 (A) reprinted with permission from Kohl et al. (2000). Copyright (2000) Elsevier Science Ltd.; (B) reprinted with permission from Münchow et al. (2005). Copyright (2005) Future Drugs Ltd.]

Fig. 3. (A): (a) Illustration of the hydrogel valve's volume changes as the gel's temperature varies. The top (a) and bottom (b) rows correspond, respectively, to temperature above and below the critical temperature T_c. The left and right columns provide, respectively, top and side views. (b) A PCR chamber equipped with two hydrogel valves. Source: Wang et al. (2005); (B): (a) A photography of the microfluidic cassette comprising a PCR reactor, conduits, an incubation chamber and hydrogel microvalves. (b) A cartridge integrating the cassette (a) with the lateral flow strip. Source: Wang et al. (2006). [Fig. 3 (A) reprinted with permission from Wang et al. (2005). Copyright (2005) Springer Science + Business Media, Inc.; (B) reprinted with permission from Wang et al. (2006). Copyright (2006) Royal Society of Chemistry.]

Fig. 4. Monolithic integrated PC-based DNA assay device. Serpentine PCR channel (PCR), hybridization channel (HC), Pluronics valves (V1–V4), Pluronic traps (T), hydrophobic air-permeable membrane (M), PCR reagent loading holes (SL), sample driving syringe pump P1, waste-withdrawing syringe pump (P2), and wash syringe pump (P3). Source: Liu et al. (2002c). [Reprinted with permission from Liu et al. (2002c). Copyright (2002) American Chemical Society.]

Fig. 5. (A) The reversible paraffin phase change microvalve with external air/vacuum systems. (i) Loading wax by actuating inlet port heater; (ii) Closing valve by actuating the inlet port and stem channel heaters with pressure at inlet port; (iii) Opening valve by actuating the stem channel and intersection heaters with vacuum at the inlet port. Source: Pal et al. (2004); (B) The integrated microfluidic device with reversible paraffin phase change microvalves. Source: Pal et al. (2005); (C) Schematic illustrations of a close-open paraffin microvalve design (A, B) and an open-close-open microvalve design (C–E). A photograph (F) of the PCR chamber surrounded by five paraffin based microvalves: valves 1–3 are open–close valves, and valves 4 and 5 are close–open valves. All valves are in “closed” position prior to initiating PCR. Source: Liu et al. (2004b). [Fig. 5 (A) reprinted with permission from Pal et al. (2004). Copyright (2004) American Chemical Society; (B) reprinted with permission from Pal et al. (2005). Copyright (2005) Royal Society of Chemistry; (C) reprinted with permission from Liu et al. (2004b). Copyright (2004) American Chemical Society.]

Fig. 6. Schematic views of the world-to-chip microfluidic interfacing approach with modular built-in valves for both sample loading and sample sealing. (A) Sample loading mode; (B) Sample sealing mode. Source: Oh et al. (2005a). [Fig. 6 (A) and (B) reprinted with permission from Oh et al. (2005a). Copyright (2005) Royal Society of Chemistry.]

Fig. 7. The PCR-CE microfluidic device (A) with pneumatically actuated membrane microvalves and hydrophobic vents (B). Source: Lagally et al. (2001b). [Fig. 7 (A) and (B) reprinted with permission from Lagally et al. (2001b). Copyright (2001) American Chemical Society.]

Fig. 8. Cross-section and top views of three-layer (A) and four-layer (B) monolithic pneumatic PDMS membrane microvalves. Source: Grover, et at. (2003). [Fig. 8 (A) and (B) reprinted with permission from Grover et al. (2003). Copyright (2003) Elsevier Science Ltd.]

Fig. 9. (A) Schematic diagram of two-step micro RT-PCR chip integrated with micropumps and microvalves for controlling biosample transportation. Source: Liao et al. (2005); (B) Schematic illustration of a microfluidic chip capable of DNA/RNA amplification, electrophoretic injection, separation, and on-line detection of product detection. Source: Huang et al. (2006); (C) Schematic illustration of the integrated RT-PCR chip. Several components including a microtemperature module, a bead collection module, and a microfluidic control module are integrated onto a single chip. Source: Lien et al. (2007). [Fig. 9 (A) reprinted with permission from Liao et al. (2005). Copyright (2005) Oxford University Press; (B) reprinted with permission from Huang et al. (2006). Copyright (2006) WILEY-VCH Verlag GmbH & Co. KGaA; (C) reprinted with permission from Lien et al. (2007). Copyright (2006) Elsevier Science Ltd.]

Fig. 10. (A) Process flow for multilayer soft lithography; (B) Schematic of pneumatically-actuated in-line microvalve closing for square and rounded channels. The dotted lines indicated the contour of the top of the channel for rectangular (left) and rounded (right) channels as pressure was increased. Source: Unger et al., 2000. (C) Schematic diagram of the N = 20 matrix chip to perform 400 independent PCR reactions, with in total 2860 in-line microvalves that was controlled by only two independent pneumatic pressure supplies. Source: Liu et al. (2003a). [Fig. 10 (A) and (B) reprinted with permission from Unger et al. (2000). Copyright (2000) American Association for the Advancement of Science; (C) reprinted with permission from Liu et al. (2003a). Copyright (2003) American Chemical Society.]

Fig. 11. Schematic representation of the valving finger assembly actuated by three servomotors. Source: Pilarski et al. (2005). [Reprinted with permission from Pilarski et al. (2005). Copyright (2005) Elsevier Science Ltd.]

Fig. 12. (A) Overview and functionality of the passive plug (PP) microvalves. (B) Picture of the nine-array PCR-CE glass microfluidic chip integrated with the PP microvalves. Source: Prakash and Kaler (2007). [Fig. 12 (A) and (B) reprinted with permission from Prakash and Kaler (2007). Copyright (2006) Springer-Verlag.]

Fig. 13. (A) A 3D scale diagram of a pneumatic peristaltic micropump. Source: adapted from Unger et al. (2000); (B) An oblique view of the three-layer pneumatic diaphragm micropump. Source: adapted from Grover et al. (2003). [Fig. 13 (A) reprinted with permission from Unger et al. (2000). Copyright (2000) American Association for the Advancement of Science; (B) reprinted with permission from Grover et al. (2003). Copyright (2003) Elsevier Science Ltd.]

Fig. 14. Sequence of the valving finger actuation during a pumping circle. The fingers were driven by three electric servomotors. Source: Pilarski et al. (2005). [Reprinted with permission from Pilarski et al. (2005). Copyright (2005) Elsevier Science Ltd.]

Fig. 15. Schematic of the fully integrated PCR chip with a thermopneumatic air micropump (#4) and three electrochemical pumps (#1–3). Source: Liu et al. (2004b). [Reprinted with permission from Liu et al. (2004b). Copyright (2004) American Chemical Society.]

Fig. 16. Diagrammatic principle of electrokinetic synchronized cyclic continuous flow PCR process. (A) Sample injection; (B) Sample cycling. Source: adapted from Chen et al. (2005a). [Reprinted with permission from Chen et al. (2005a). Copyright (2005) American Chemical Society.]

Fig. 17. Ferrofluidic magnetic micropump scheme for the oscillating-flow PCR chip. Source: Münchow et al. (2005). [Reprinted with permission from Münchow et al. (2005). Copyright (2005) Future Drugs Ltd.]

The characteristics of thermally-actuated phase change microvalves used in PCR chips

Note: R — reversible; I — irreversible; NC — normally closed microvalves; NO — normally open microvalves; B — bistable; O — opening; C — closing.

Mechanical micropumps reported in PCR chips

Note: S — series configuration; V — micropump operating voltage; f — micropump operating frequency; p_max —