Flexible Iontronic Tactile Sensors Based on Silver Nanowire Electrode with Sandpaper-Roughened Surface and Ionic Liquid Gel Electrolyte with Porous Foam Structure for Wearable Sensing Applications

Abstract

The need for wearable electronics has remarkably increased due to the fast development of flexible tactile sensors with the unique capability of responding to external pressure stimuli while maintaining a high degree of deformability. To meet the practical wearable sensing requirement, outstanding sensitivity and a wide detection range are always highly desired. Herein, we report the design and fabrication of a flexible iontronic tactile sensor based on a stretchable silver nanowire (AgNW)/Ecoflex composite film with a sandpaper-roughened surface as the electron-conductive electrode and a porous polyurethane (PU)/poly(vinylidene fluoride) hexafluoropropylene copolymer (PVDF)/1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF₄]) composite foam as the ion-conductive electrolyte through a facile dip-coating method. Because of the supercapacitive sensing mechanism and the surface and internal microstructures, an ultrahigh sensitivity of 422.22 kPa^–1 and a maximum wide detection range of 80 kPa are simultaneously achieved after thorough compositional and structural optimization. Toward practical wearable sensing applications, the developed iontronic tactile sensor is demonstrated to be capable of detecting various subtle and large pressures caused by different parts of the human body, such as wrist pulse, swallowing, speaking, and bending of the finger, wrist, and elbow. The proposed material and structure strategy would provide a concept and methodology for the development of sensors with excellent performance.