Flexible highly sensitive hydrogen gas sensor based on a TiO2 thin film on polyimide foil

Abstract There is currently a high demand for highly-sensitive semiconductor gas sensors operating at low temperature, which would be compatible with semiconductor technology and could be incorporated in one chip with other electronic circuits. Although some suitable sensors were already developed, recent trend of flexible electronics brings yet another challenge for researchers − to prepare such sensors on flexible substrates. In this work, we present a flexible semiconductor gas sensor of hydrogen prepared on 38 μm thick Kapton ® polyimide foil, based on a TiO 2 thin film with platinum interdigital electrodes on top. In dry conditions, the sensor is highly sensitive even at room temperature, with response (R 0 /R H2 ) reaching ∼10 4 for 10000 ppm H 2 in synthetic air and its capability of sensing H 2 concentrations as low as ∼30 ppm has been demonstrated. At elevated temperature of 150 °C, the response reached more than ∼10 6 for 10000 ppm H 2 . Humidity negatively affects the sensor performance particularly at room temperature, where at 32% relative humidity the sensor response to 10000 ppm H 2 decreased to ∼10 3 and the lowest detected H 2 concentration was ∼300 ppm H 2 . Bending the sensor 1000 times over diameter of 10 mm did not cause any significant damage of the device or decrease of sensitivity. On the contrary, the response of the sensor at close-to-room temperatures and at low concentrations of H 2 increased after the bending.