Microfluidic Solution Isolated Pumping (μSIP)

Abstract

One of the core requirements for the further maturity in microfluidics is to develop a fluid actuation method in bubble-free and power-efficient manner. Although kinds of active and passive fluid control techniques have been described over the past several decades, complex microfluidic systems still require bulky or energy-inefficient actuation components and simpler systems lack the functionality required for a simple field diagnostic test. Here a novel microfluidic pumping strategy is reported which utilizes the high air permeability of silicone materials to actuate fluid flow, named as Microfluidic Sample Isolated Pumping (μSIP). The key elements of μSIP are two channel networks, the fluidic channel and the degas channel, isolated by selective barriers and located in close proximity to each other. The selective barriers allow gas to pass through while being inaccessible for aqueous liquids due to low surface energy of the porous material. An air concentration gradient across the two networks generates an in-situ diffusive flux out of the fluidic channel. It results in fluidic channel pressure reduction which drives the liquid solution into the fluidic channel while the solution being kept isolated from the surrounding degas channels by the selective barrier. To understand the physics behind μSIP, theoretical analysis and experimental characterizations were performed, the experimental data could be well illustrated and predicted by the developed theories and also average flow velocities in the range of 0.7 to 7 mm/s were observed with the current designs. The μSIP provides tunable, reproducible, and bubble-free microfluidic pumping without any auxiliary equipment or device pre-treatment, providing a powerful liquid handling tool for a broad range of applications.