Passive Time-Controlled Fluid Delivery in Microfluidic Devices Using One-Shot Dissolvable Poly(vinyl) Alcohol Microvalves

Featured Application: Low-cost, passive time-controlled fluid delivery in microfluidic devices without external actuation. Passive microvalves enable autonomous operation of microfluidic devices by allowing time-controlled fluid delivery without external actuation. Here, we report a simple, low-cost, single-use passive microvalve based on poly(vinyl alcohol) (PVA) for time-programmed fluid delivery. The valve operates through dissolution of a solidified PVA plug formed inside poly(methyl methacrylate) (PMMA) microchannels after evaporation of the solvent phase. The valve dissolves when exposed to an aqueous medium, enabling fluid flow. The valve opening time was experimentally characterized as a function of the injected liquid volume using three PVA formulations and three microchannel cross-sections fabricated in PMMA. Experimental results showed a non-linear dependence of the opening time on the injected volume, as well as the influence of PVA formulation, channel geometry, and temperature. In addition, a demonstrative multi-valve device showed sequential valve opening with delays up to 7 h. The proposed approach enables simple and autonomous timed fluid release using inexpensive materials and straightforward fabrication processes, representing a promising strategy for low-cost microfluidic applications.