Soft Bimodal Sensor Array Based on Conductive Hydrogel for Driving Status Monitoring

：Driving status monitoring is important to safety driving which could be adopted to improve driving behaviors through hand gesture detection by wearable electronics. The soft bimodal sensor array (SBSA) composed of strain sensor array based on ionic conductive hydrogels and capacitive pressure sensor array based on ionic hydrogel electrodes is designed to monitor drivers' hand gesture. SBSA is fabricated and assembled by the stretchable functional and structural materials through a sol-gel process for guaranteeing the overall softness of SBSA. The piezoresistive strain and capacitive pressure sensing abilities of SBSA are evaluated by the data acquisition system and signal analyzer with the external physical stimuli. The gauge factor (GF) of the strain sensor is 1.638 under stretched format, and -0.726 under compressed format; sensitivity of the pressure sensor is 0.267 kPa^-1 below 3.45 and 0.0757 kPa^-1 in the range of 3.45-12 kPa, which are sensitive enough to hand gesture detection and driving status monitoring. The simple recognition method for the driver's status behavior is proposed to identify the driver's behaviors with the piezoresistive properties of conductive polymers, and the turning angles are computed by the strain and pressure values from SBSA. This work demonstrates an effective approach to integrate SBSA seamlessly into an existing driving environment for driving status monitoring, expanding the applications of SBSA in wearable electronics.