A Microfluidic Transistor for Liquid Signal Processing

Abstract/SummaryMicrofluidics have enabled significant advances in molecular biology1-3, synthetic chemistry4,5, diagnostics6,7, and tissue engineering8. However, there has long been a critical need in the field to manipulate fluids and suspended matter with the precision, modularity, and scalability of electronic circuits9-11. Just as the electronic transistor enabled unprecedented advances in the control of electricity on an electronic chip, a microfluidic analogue to the transistor could enable improvements in the complex, scalable control of reagents, droplets, and single cells on an autonomous microfluidic chip. Prior works on creating a microfluidic analogue to the electronic transistor12-14 could not replicate the transistors saturation behavior, which is crucial to perform analog amplification15 and is fundamental to modern circuit design16. Here we exploit the fluidic phenomenon of flow-limitation17 to develop a microfluidic element with flow-pressure characteristics completely analogous to the current-voltage characteristics of the electronic transistor. As this microfluidic transistor successfully replicates all of the key operating regimes of the electronic transistor (linear, cut-off and saturation), we are able to directly translate a variety of fundamental electronic circuit designs into the fluidic domain, including the amplifier, regulator, level shifter, logic gate, and latch. Finally, we demonstrate a "smart" particle dispenser that senses single suspended particles, performs liquid signal processing, and accordingly controls the movement of said particles in a purely fluidic system without electronics. By leveraging the vast repertoire of electronic circuit design, microfluidic transistor-based circuits are easy to integrate at scale, eliminate the need for external flow control, and enable uniquely complex liquid signal processing and single-particle manipulation for the next generation of chemical, biological, and clinical platforms.