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Antenna-Based Popup Vapor Sensor Guided by Controlled Compressive Buckling

A novel highly stretchable gas sensor is reported that is based on popup antenna reconfiguration due to the strain induced by the swelling of a polydimethylsiloxane (PDMS) substrate when exposed to diethyl ether. When the swollen substrate is removed from the volatile solvent environment, the PDMS volume increase is reversed leading to compressive stress in an attached antenna transforming a 2D structure to a 3D structure through mechanically induced shaping. This provides a low cost and simple route to tune the antenna resonant frequency and gain in direct response to a chemical stimulus. Our proposed solvent sensor is able to measure 0 to 60% PDMS swelling corresponding to diethyl ether concentrations up to 1620 ppm via a resonant frequency shift from 4 to 2.4 GHz. A fatigue life study indicated 103.5 life cycles which demonstrates the durability of these sensors to accommodate large strain and repeatability of the sensing process. Multiphysics Finite Element Method (FEM) modelling of the mechanical and RF simulations along with analytical results based on an equivalent circuit model were in good agreement with experimental data and demonstrate the potential of these structures as sensors.