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Transon V. Nguyen, Philip N. Duncan, Siavash Ahrar, Elliot E. Hui

Department of Biomedical Engineering, University of California, Irvine, CA, USA.

Abstract Microfluidic large-scale integration achieves highly complex fluid control, but typically relies upon unwieldy off-chip pneumatic and electronic components that interface to the chip through a maze of tubing. To alleviate this problem, digital logic constructed out of microfluidic valves and channels could potentially enable fully self-contained microfluidic systems that are controlled by onboard circuitry. We present a significant advance in microfluidic digital logic that brings us close to achieving fully autonomous microfluidic systems. Building on previous work in the field, our implementation is based upon normally closed microfluidic valves that can be treated analogously to NMOS transistors in the construction of digital circuits, allowing us to create several fundamental logic circuits in microfluidics. Specifically, we demonstrate the first true finite state machine (FSM) controller in microfluidics. Our 2-bit FSM, which provides four output states, behaves by storing its current state in memory while simultaneously calculating the next state to transition to based upon its current state. We also report precision microfluidic oscillators for use in on-chip clocking and fluid control, asynchronous counters for measuring periods of time, and a semi-autonomous fluid handling system that requires only 5 connections to a constant vacuum and no dependence on programmable external controllers such as computers. The semi-autonomous fluid handling system is capable of metering, mixing, incubating, and flushing out two liquids, and all fluid routing and pumping is entirely controlled by on-chip circuitry. The integration of these components into a single microfluidic chip has the potential to create a fully-autonomous device capable of complex fluid handling, with only a single connection to a modest vacuum source (such as a syringe or a hand pump) for power. 

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