3D-printed Multimaterial Microfluidic Transistors

Abstract

Microfluidic actuators, including elastomeric microvalves and microfluidic transistors, are increasingly used to augment and simplify flow automation. The vast majority of these actuators regulate flow using microfabricated, thin membranes that are inherently difficult to fabricate and integrate into small devices. The performance of these actuator platforms is critically determined by the membrane’s mechanical performance, which calls for scalable and reliable membrane microfabrication techniques. Previous approaches for manufacturing elastomeric membranes in microfluidic actuators enabled either their high-resolution fabrication (e.g., soft lithography) or their facile manufacturability (e.g., 3D printing), but not both. Here we present a photopolymer resin that closely mimics the Young’s Modulus (elasticity) and reversible stretchability (no hysteresis) of poly(dimethylsiloxane) (PDMS) without compromising its high resolution or biocompatibility. This development enables the fabrication of microfluidic transistors (i.e., microvalves capable of proportional amplification) by multimaterial stereolithography (mSLA). Our mSLA-printed microfluidic transistors display proportional pressure amplification occasionally reaching large intrinsic gains (>300), although reliably printing complex multi-transistor devices will require high-resolution 3D-printers. Moreover, the absence of hysteresis overcomes a longstanding problem of unequal opening and closing thresholds found in most microfluidic actuators, allowing us to demonstrate the first mSLA-printed pressure amplifiers. This work represents an advancement towards building more complex microfluidic automats.