A transparent stretchable sensor for distinguishable detection of touch and pressure by capacitive and piezoresistive signal transduction

• Published in: NPG Asia materials Vol. 11; no. 1
• Main Authors: Hwang, Byeong-Ung, Zabeeb, Arsalan, Trung, Tran Quang, Wen, Long, Lee, Jae Deuk, Choi, Young-In, Lee, Han-Byeol, Kim, Ju Hyun, Han, Jeon Geon, Lee, Nae-Eung
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.12.2019; Nature Publishing Group
• Subjects: 639/301/1005/1007; 639/301/1005/1009; Biomaterials; Chemistry and Materials Science; Cursor control devices; Dimpling; Electrodes; Electronics; Energy Systems; Indium tin oxides; Input devices; Ionic liquids; Materials Science; Multilayers; Optical and Electronic Materials; Polymers; Pressure sensors; Sensitivity; Sensor arrays; Sensors; Service life assessment; Signal transduction; Stimuli; Stretchability; Structural Materials; Substrates; Surface and Interface Science; Thin Films; Touch; Touch screens; Wearable technology; Wrist
• DOI: 10.1038/s41427-019-0126-x
• ISSN: 1884-4049

Transparent stretchable (TS) sensors capable of detecting and distinguishing touch and pressure inputs are a promising development in wearable electronics. However, realization of such a device has been limited by difficulties in achieving optical transparency, stretchability, high sensitivity, stability, and distinguishable responsivity to two stimuli simultaneously. Herein, we report a TS sensor in which touch and pressure stimuli can be detected and distinguished on a substrate with a stress-relieving three-dimensional (3D) microstructured pattern providing multidirectional stretchability and increased pressure sensitivity. The TS capacitive device structure is a dielectric layer sandwiched between an upper piezoresistive electrode of a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/ionic liquid composite, which enables touch and pressure stimuli to be distinguished, and a lower electrode of metal/indium tin oxide/metal multilayer. The TS sensor array was demonstrated as a wearable input device for controlling a small vehicle. The TS touch-pressure sensor has great potential to be used as a multimodal input device for future wearable electronics. Wearable electronics: bumpy textures improve human–machine interactions A 3D-textured material has helped researchers develop a transparent patch that can act as an ergonomic electronic controller. Nae-Eung Lee from Sungkyunkwan University in Suwon, South Korea, and colleagues created a body-attachable touchscreen using an organic polymer that conducts different amounts of electricity depending on how hard it is pressed. After assembling this polymer into a transparent thin-film capacitor, the team encased it in a silicone material with thousands of microscale dimples. Experiments showed that the bumpy coating randomized the effects of mechanical stress effects occurring when the patch was attached to the wrist of human volunteers, extending device lifetime to over 10,000 cycles. The polymer device could electronically distinguish between a light touch and sustained pressure, enabling subjects to steer or accelerate a toy car with just one finger. A transparent stretchable (TS) capacitive sensor, which can detect pressure (force) and touch inputs distinguishably was fabricated by forming with a TS dielectric layer sandwiched between the upper piezoresistive electrode of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)–ionic liquid composite enabling to distinguish touch and pressure stimuli and the lower TS electrode of metal/indium tin oxide/metal multilayer on a transparent elastomeric substrate with stress-relieving three-dimensional microstructured pattern providing multi-directional stretchability and high pressure sensitivity. The TS sensor array demonstrated a good control of the interaction with a small vehicle as a multi-functional input device for future wearable electronics.