Circular Microchannels Enhance Diodicity Performance at Ultra-low Reynolds Number for Microfluidic Bead-based Diodes

Self-regulating fluidic components are critical to the advancement of micro/nanofluidic circuitry for chemical and biological applications, including sample preparation on chip and point-of-care (POC) molecular diagnostics. Previously, a variety of diodic components have been developed to enable flow rectification in fluidic technologies (e.g., microscale drug delivery systems in which backflow could be medically harmful). In particular, prior works have utilized suspended microbeads as dynamic resistive elements to achieve microfluidic diodes for ultra-low Reynolds Number (i.e., Re < 0.25) applications; however, using spherical beads to block fluid flow through rectangular channels is inherently limited. To overcome this issue, here we present a microfluidic bead-based diode that uses a targeted circular-shaped microchannel for microbead docking to rectify fluid flow under Re ≤ 0.25 conditions. Experimental results revealed Diodicities (Di’s) ranging from 1.34±0.15 to 5.32±0.64 for Re varying from 0.05 to 0.25.