%0 Journal Article %T Pd films on soft substrates: a visual, high-contrast and low-cost optical hydrogen sensor %J - %D 2019 %R https://doi.org/10.1038/s41377-018-0114-x %X For the rapid development of the hydrogen economy, a reliable and low-cost hydrogen sensor appears to be extremely important. Here, we first show that a palladium film deposited on polydimethylsiloxane (PDMS) can obtain an exceedingly high-reflectance contrast of 25.78 over the entire visible band upon exposure to 4£żvol% hydrogen gas (H2) mixed with nitrogen gas. This high-reflectance contrast results from the surface deformation induced by the volume inflation after exposure to H2, leading to the transition of the near-specular surface to a diffusing surface. In addition, a change in brightness is readable by naked eye upon exposure to H2 with various concentrations from 0.6 to 1£żvol% under the illumination of a fluorescent tube. Furthermore, this sensor possesses an excellent recyclability and quick response time of a few seconds. Compared with Pd nanostructure-based hydrogen sensors, this visual, high-contrast and low-cost sensor is of great potential for practical hydrogen sensing %U https://www.nature.com/articles/s41377-018-0114-x