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A biomimetic hydrogel valve capable of directional flow control in response to the local fluid environment in microfluidic channels is described. The valve consists of a pair of photopolymerized hydrogel bistrips with different pH sensitivities, and becomes activated or deactivated reversibly based on local pH as a result of volume and shape changes. When activated at pH 8, the valve mimics anatomic venous valves both functionally and structurally, allowing fluid flow in one direction under forward pressure while restricting flow in the opposite direction. At an applied pressure of 0.71 psi, the forward flow rate was 140 μL/min, compared to a backward leakage rate of 2.3 μL/min.
Yu et al. (Mon,) studied this question.