A passive hydrogel-based inertial switch integrated with micromachined L-C resonator

This work presents the development of an inertial switch employing stimuli-sensitive hydrogel integrated with a passive inductor/capacitor (LC) resonator. The device consists of a glass substrate with capacitor plates and an inductor coil, and a PDMS microfluidic chip with micro-channels and micro-cavities containing hydrogel and water droplet. When the acceleration exceeds the designed threshold-level, the water passes through the channel to the hydrogel cavity. The hydrogel swells and changes the capacitance of the integrated LC resonator, which in turn changes the resonant frequency that can be remotely detected. All the PDMS structures were fabricated by using soft lithography. The L-C resonator was fabricated by lift-off process for patterning metal layers on a glass substrate. The size of the device is 15mm×10mm×1mm. The functionalities of proposed device were demonstrated. The measurement shows that the resonant frequencies shift from 72MHz to about 57MHz as the device is activated by acceleration.