Skin-inspired gradient ionogels induced by electric field for ultrasensitive and ultrafast-responsive multifunctional ionotronics

Abstract

Ionogels have garnered great attention for fabricating flexible soft ionotronics as they can mimic human skin that responds to external stimuli. However, the low detection sensitivity and limited responsiveness as well as the complicated fabrication process significantly limit their wide applications. Herein, a skin-inspired stretchable, compressible, self-adhesive ionogel with gradient and hierarchical microstructures and properties has been prepared by a one-step electric-field assisted photo-polymerization method. By regulating the ions of ionic liquids (ILs) and poly(ionic liquid)s (PILs), these PIL ionogels also exhibit good adjustable hydrophilicity/hydrophobicity and environmental adaptability. Based on the gradient conductivity capacity along with the gradient mechanical structure, the gradient ionogel-based flexible ionotronic shows high sensitivity up to 1.0 kPa⁻¹ over a wide range of detection up to 400 kPa, low minimum detection (0.15 Pa), fast response time (8 ms), wide working temperature range (−85 to 360 °C), and good durability (5000 cycles). More importantly, the developed high-resolution pressure-sensing array can accurately detect the contour and output three-dimensional pressure distribution maps. Furthermore, advanced soft ionotronic sensors with multimodal sensation capabilities are further designed, which can detect various motions, such as liquid drop sensing, human joint motion detection, and real-time pulse wave monitoring.