Triboelectric Array by Selective UV Irradiation of Thermoplastic Block Copolymer for Tactile Sensor

Multi-functional electronic skin (e-skin) sensors have been proposed to mimic the sensory functions of human skin such as strain, pressure, temperature, and humidity. Among various stimuli, tactile sensing that can directly convert surrounding tactile information into electrical signal have the key function for the e-skin because of potential application in human-machine interfaces, the Internet of things (IoT), etc. In terms of functionality, many studies have been conducted on deformability, lightweight, and high sensitivity. However, low power consumption and simple structure remain problems to be solved.<br/>Tactile sensors based on self-powered technologies such as piezoelectric, ferroelectric, and triboelectric power generation can not only solve the problem of power supply, an essential part of conventional electronic devices but also reduce the number of device components required to drive sensors. Among the various self-powered sensors, triboelectric tactile sensors have attracted great attention because of their simple structure, low cost, and high sensing output even with low stimulation. As another problem, the previously reported sensors had difficulty increasing the number of sensing pixels in a single sensor because the number of pixelated patterns and the number of interconnections receiving information from each pixel increase exponentially as the number of pixels increases In order to solve this problem, it is necessary to manufacture a sensor that can form multiple pixels on a single electrode. To implement this, i) there is a large difference in the contact charge between the selective surface and the base surface on the layer, and ii) the contact charge of the selective surface can be adjustable and iii) the selective pattern should be able to be manufactured with a simple process. Many papers have been reported on improving the contact charge through various treatments on the surface of the dielectric. However, there are difficulties in satisfying all three conditions.<br/>In this study, a thermoplastic block copolymer (BCP) film was patterned to have different triboelectric properties on each area by UV irradiation and used as the sensing layer of a wearable self-powered tactile sensor. Arbitrarily designated pixels on the BCP film were controlled to generate different triboelectric charges by changing the UV crosslinking time. BCP film with UV patterning on stretchable electrodes can form multiple sensor arrays with only one wiring. In the skin, sensors can detect the position and sequence of touches, the movement and speed of the touched object, and the shape of the object.