Thermal-sensitive ionogel with NIR-light controlled adhesion for ultrasoft strain sensor

With the widespread prevailing of flexible electronics in human—machine interfaces, health monitor, and human motion detection, ultrasoft flexible sensors are urgently desired with critical demands in conformality. Herein, a temperature-sensitive ionogel with near-infrared (NIR)-light controlled adhesion is prepared by electrostatic interaction of poly(diallyl dimethylammonium chloride) (PDDA) and acrylic acid, as well as the incorporation of the conductive polydopamine modified polypyrrole nanoparticles (PPy-PDA NPs). The PPy-PDA NPs could weaken the tough interaction between polymer chains and depress the Young’s modulus of the ionogel, thus promoting the ionogel ultrasoft (34 kPa) and highly stretchable (1,013%) performance to tensile deformations. In addition, the high photothermal conversion capacity of PPy-PDA NPs ensured the ionogel excellent NIR-light controlled adhesion and temperature sensitivity, which facilitated the ionogel on-demand removal and promised a reliable thermal sensor. Moreover, the resulted ultrasoft flexible sensor exhibited high sensitivity and stability to both strain and pressure in a broad range of deformations, enabling a precise monitoring on various human motions and physiological activities. The temperature-sensitive, ultrasoft, and controlled adhesive capabilities prompted great potential of the flexible ionogel in medical diagnosis and wearable electronics.