A new microfluidic pressure-controlled Field Effect Transistor (pFET) in digital fluidic switch operation mode

Lab-on-Chip is currently considered the technology with the potential to revolutionize future biochemical analysis providing miniaturized, low-reagent volume microchips as an alternative to traditional benchtop analysis. Automated control of droplet flow is currently a key objective in microfluidics research, aiming for droplet logic microfluidic circuits. To this end, microfluidic research has been following the electronics paradigm, with several digital fluidic components being demonstrated towards the realization of digital fluidic circuits for automated liquid control and delivery. In this work, we introduce a new concept of microfluidic pressure controlled field-effect transistors (pFETs), towards droplet logic operations. Using a fluidic with porous and hydrophobic walls, the inherently pinned plug depins by pressure application through the porous wall (backpressure), thus enabling the actuation and the downward transportation of the plug due the action of gravity. This concept resembles the logic operation of a metal–oxide–semiconductor field-effect transistor (MOSFET). The pFET operating parameters are thus defined in a manner analogous to MOSFET digital switches and their dependence on the channel width is studied also for the first time. The successful operation of pFET devices for droplet logic operation is verified in continuous ON/OFF cycles, achieving OFF-ON and ON-OFF switching times under 1 s (0.864 s and 0.841 s respectively) and therefore promising rapid liquid switching times, comparable to electronic circuit ones.