Lithography-free, Pd-based bimorph cantilever switches for zero-standby-power chemo-mechanical H2 detection

Currently available hydrogen (H2) detection methods are fundamentally inefficient because, although leaks are rare, continuous, power-consuming monitoring across large sensor networks is necessary owing to the flammable and explosive nature of H2. A cost-effective fabrication strategy for chemo-mechanical switches that enables zero-standby-power H2 detection is presented herein. The switches comprise a palladium (Pd)-based bimorph cantilever structure and are fabricated by tilted metal deposition on water-soluble electrospun nanofiber templates, without the need for conventional photolithography. This approach also permits the use of nonhazardous chemicals, thereby reducing the environmental burden and safety risks during fabrication. The Pd-based cantilevers function as chemo-mechanical H2 switches; H2 absorption in the Pd layer induces asymmetric expansion within the bimorph, bending the cantilever, thus closing the gap and establishing electrical contact. The chemo-mechanical H2 switches are experimentally characterized for various fabrication parameters, and their H2 detection performances are evaluated in terms of detection threshold, sensitivity, and transient response. The H2 switches exhibit noise-level currents of ~2.2 pA in the absence of H2, a low detection limit of 0.3% H2, short response time of 37.2 s, and high sensitivity exceeding 1.35 × 105.