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.