Hierarchical Metal Oxide Wrinkles as Responsive Chemical Sensors

Easily observed wrinkle structures comprise various materials. Because evolutionary wrinkle structures exhibit a broad surface area, light scattering, and hydrophobicity, the structural advantages of wrinkles have been exploited in several research fields. Wrinkle structures have been applied to various materials as well as used in metals, graphene, and polymers; however, it is extremely difficult to prepare metal oxide-based wrinkle structures because of the brittle nature of metal oxide. In this study, a universal method for synthesizing hierarchical metal oxide wrinkle (hereafter referred to as the H-wrinkle) structures with precise morphology control was developed. Metal oxide H-wrinkles were prepared using a polymer sacrificial layer and transferred for consecutive thermal oxidations on the target substrate. To investigate the morphological properties of the H-wrinkle, the CuO H-wrinkle was applied to gas-sensing devices; it showed a sensitivity 6.07 times greater than that of the pristine CuO film sensors. This significant improvement corresponding to the unique morphological properties of H-wrinkles renders considerable adsorption sites and high surface permeability and subsequently permits the facile penetration of gas into the sensing layers. In this study, we demonstrated a first example of the use of the metal oxide wrinkle structure in electronic devices and thus confirmed its use in various applications.