Highly Mobile Palladium Thin Films on an Elastomeric Substrate: Nanogap-Based Hydrogen Gas Sensors

摘要

The design of chemical sensors for commercial applications needs to be improved to meet the requirement of mass production, yet many current strategies in sensor design are increasingly complicated and less accessible to manufacturers. These designs mostly rely on making nanoscale gaps in a material of interest, which allow enhancements in performance and miniaturization. In hydrogen gas (H2) sensors, nanoscale gaps in palladium nanowires have been widely used to study sensor mechanisms and to develop reversible gas sensing capabilities, which is an important step forward in rational sensor design. However, integrating these nano-gaps into a large-scale device has been a significant challenge, and as a consequence, it has been difficult to realize a commercially viable device. Approaches that overcome the problem inherent to scalability have been developed in Pd thin-film H2 sensors, but they suffer from low sensitivity, low speed, and poor reliability. Herein, we present a novel, low cost, scalable, and lithography-free but nanogap-based sensing method. This highly mobile thin film on elastomer (MOTIFE) utilizes crack formation in a Pd (and PdNi) thin film generated by stretching the film on an elastomeric substrate to reliably and reproducibly provide highly sensitive H2 sensors. Not only do we demonstrate that stretching a Pd (and PdNi) thin film on an elastomer creates uniform nanogaps over large areas, the size of which can be controlled down to 300 nm at 25 % strain, but we also show that these structures may be used for a high-performance H2 sensor.