Single-layer “domino” diodes via optofluidic lithography for ultra-low Reynolds number applications

Autonomous fluidic components are critical to the advancement of integrated micro/nanofluidic circuitry for lab-on-a-chip applications, such as point-of-care (POC) molecular diagnostics and on-site chemical detection. Previously, a wide range of self-regulating microfluidic components, such as fluidic diodes, have been developed; however, achieving effective functionality at ultra-low Reynolds number (e.g., Re <; 0.05) has remained a significant challenge. To overcome this issue, here we introduce single-layer microfluidic “domino” diodes, which utilize free-standing rotational microstructures - constructed in situ via optofluidic lithography - in order to passively regulate the fluidic resistance based on the flow polarity, thereby enabling flow rectification under ultra-low Re conditions. COMSOL simulation results revealed a theoretical Diodicity (Di) of 31 for a singular domino diode component. Experimental results (for systems with four microstructures) revealed Di's ranging from 13.0±1.9 to 25.4±1.9 corresponding to 0.025 <; Re <; 0.030 and 0.010 <; Re <; 0.015 flow, respectively, which represent the largest Di's reported for Re <; 0.05 fluid flow.