Electronic control of elastomeric microfluidic circuits with shape memory actuators.

Recently, sophisticated fluidic circuits with hundreds of independent valves have been built by using multi-layer soft-lithography to mold elastomers. However, this shrinking of microfluidic circuits has not been matched by a corresponding miniaturization of the actuation and interfacing elements that control the circuits; while the fluidic circuits are small ( approximately 10-100 micron wide channels), the Medusa's head-like interface, consisting of external pneumatic solenoids and tubing or mechanical pins to control each independent valve, is larger by one to four orders of magnitude (approximately mm to cm). Consequently, the dream of using large scale integration in microfluidics for portable, high throughput applications has been stymied. By combining multi-layer soft-lithography with shape memory alloys (SMA), we demonstrate electronically activated microfluidic components such as valves, pumps, latches and multiplexers, that are assembled on printed circuit boards (PCBs). Thus, high density, electronically controlled microfluidic chips can be integrated alongside standard opto-electronic components on a PCB. Furthermore, we introduce the idea of microfluidic states, which are combinations of valve states, and analogous to instruction sets of integrated circuit (IC) microprocessors. Microfluidic states may be represented in hardware or software, and we propose a control architecture that results in logarithmic reduction of external control lines. These developments bring us closer to building microfluidic circuits that resemble electronic ICs both physically, as well as in their abstract model.