Many modern user interfaces are based on touch, and such sensors are widely used in displays, Internet of Things (IoT) projects, and robotics. From lamps to touchscreens of smartphones, these user interfaces can be found in an array of applications. However, traditional touch sensors are bulky, complicated, inflexible, and difficult-to-wear devices made of stiff materials. The touch screen is gaining further importance with the trend of current IoT technology flexibly and comfortably used on the skin or clothing to affect different aspects of human life. This review presents an updated overview of the recent advances in this area. Exciting advances in various aspects of touch sensing are discussed, with particular focus on materials, manufacturing, enhancements, and applications of flexible wearable sensors. This review further elaborates on the theoretical principles of various types of touch sensors, including resistive, piezoelectric, and capacitive sensors. The traditional and novel hybrid materials and manufacturing technologies of flexible sensors are considered. This review highlights the multidisciplinary applications of flexible touch sensors, such as e-textiles, e-skins, e-control, and e-healthcare. Finally, the obstacles and prospects for future research that are critical to the broader development and adoption of the technology are surveyed.

Layered Sn-based chalcogenides and heterostructures are widely used in batteries and photocatalysis, but its utilizations in a supercapacitor is limited by its structural instability and low conductivity. Here, SnS_x thin films are directly and conformally deposited on a three-dimensional (3D) Ni-foam (NF) substrate by atomic layer deposition (ALD), using tetrakis(dimethylamino)tin [TDMASn, ((CH₃)₂N)₄Sn] and H₂S that serves as an electrode for supercapacitor without any additional treatment. Two kinds of ALD-SnS_x films grown at 160 °C and 180 °C are investigated systematically by X-ray diffractometry, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy (TEM). All of the characterization results indicate that the films deposited at 160 °C and 180 °C predominantly consist of hexagonal structured-SnS₂ and orthorhombic-SnS phases, respectively. Moreover, the high-resolution TEM analyses (HRTEM) reveals the (001) oriented polycrystalline hexagonal-SnS₂ layered structure for the films grown at 160 °C. The double layer capacitance with the composite electrode of SnS_x@NF grown at 160 °C is higher than that of SnS_x@NF at 180 °C, while pseudocapacitive Faradaic reactions are evident for both SnS_x@NF electrodes. The superior performance as an electrode is directly linked to the layered structure of SnS₂. Further, the optimal thickness of ALD-SnS_x thin film is found to be 60 nm for the composite electrode of SnS_x@NF grown at 160 °C by controlling the number of ALD cycles. The optimized SnS_x@NF electrode delivers an areal capacitance of 805.5 mF/cm² at a current density of 0.5 mA/cm² and excellent cyclic stability over 5000 charge/discharge cycles.