Pressure driven digital logic in PDMS based microfluidic devices fabricated by multilayer soft lithography

TLDR

Microfluidics now enables unprecedented parallelization and integration of biochemical reactions, yet control hardware remains costly and complex because each independently actuated valve set requires its own external pressure signal. The study aims to introduce a new implementation of digital fluidic logic that is fully analogous to electronic logic and offers significant performance improvements. This is achieved by a simple post‑modification to the multilayer soft lithography fabrication process that enables normally closed static gain valves. We demonstrate a normally closed static gain valve and a range of fluidic logic circuits—including NOT, NAND, NOR gates, flip‑flops, oscillators, peristaltic pumps, and a 12‑bit shift register—that exhibit cascade‑ability, feedback, programmability, bi‑stability, autonomous control, and deliver smaller devices, higher clock rates, simpler designs, and easier fabrication and integration into multilayer soft lithography microfluidics.

Abstract

Advances in microfluidics now allow an unprecedented level of parallelization and integration of biochemical reactions. However, one challenge still faced by the field has been the complexity and cost of the control hardware: one external pressure signal has been required for each independently actuated set of valves on chip. Using a simple post-modification to the multilayer soft lithography fabrication process, we present a new implementation of digital fluidic logic fully analogous to electronic logic with significant performance advances over the previous implementations. We demonstrate a novel normally closed static gain valve capable of modulating pressure signals in a fashion analogous to an electronic transistor. We utilize these valves to build complex fluidic logic circuits capable of arbitrary control of flows by processing binary input signals (pressure (1) and atmosphere (0)). We demonstrate logic gates and devices including NOT, NAND and NOR gates, bi-stable flip-flops, gated flip-flops (latches), oscillators, self-driven peristaltic pumps, delay flip-flops, and a 12-bit shift register built using static gain valves. This fluidic logic shows cascade-ability, feedback, programmability, bi-stability, and autonomous control capability. This implementation of fluidic logic yields significantly smaller devices, higher clock rates, simple designs, easy fabrication, and integration into MSL microfluidics.