A simple micro check valve using a photo-patterned hydrogel valve core

Micro check valves play a pivotal role in many microfluidic systems. However, there is still an unmet need for low-cost check valves with good performance and easy integration. In this work, we present a planar micro check valve using a hydrogel valve core fabricated in situ in a microchannel. This valve is characterized by a simple fabrication process and easy integration with other microfluidic devices. Experimental results proved that the check valve performs better than most existing in-plane micro check valves, especially in low-pressure operations, with nearly zero forward cracking pressure and reverse leakage, adjustable forward fluidic resistance, and good repeatability. We further proposed a normally-closed check valve with controllable cracking pressure to meet different requirements of microfluidic devices. Precise cracking pressures could be achieved by regulating the valve spring width. To demonstrate the valve usefulness, we employed these valves to make a finger-actuated micro-mixer and a bio-actuated micro-pump. This study makes the flow control more simplified in integrated microfluidic systems. (C) 2020 Elsevier B.V. All rights reserved.