A Sample‐Triggered Microvalve Based on Material Property Regulation Mechanism for Reagent Storage and on‐Demand Release

Prestoring and on‐demand releasing of reagents is an essential feature for further automation and integration of lab‐on‐a‐chip (LOC). The current microvalves rely on external drive to trigger release the prestored reagent. Herein, a novel microvalve that can achieve long‐term prestorage and tested‐sample‐triggered release of reagents is developed. The microvalve functions based on water‐triggered material property regulation mechanism: the waterproof film contributes to the reagent stable storage; the water‐solvable film would lose most of its mechanical strength once triggered by water; then the bilayer film would fracture under the stress of the microspring, releasing the prestored reagent. The functionality of the microvalve is demonstrated in a microfluidic chip. The microvalve is triggered open by the test sample, and the released prestored reagent flows to the reserved reaction area few minutes later. The delay time could be adjusted from 0.1 to 11 min as required by sample reaction, through controlling the structure of the time‐delay valve. Compared to previous reported microvalves that rely on the external drive, the novel microvalve reported herein provides a new approach to realize internal signal‐triggered release of the prestored reagent, thus achieving a real accessory‐free, portable, and user‐friendly self‐contained LOC for rapid and point‐of‐care diagnostics.