Soft Robots Proprioception Through Stretchable Laser-Induced Graphene Strain Sensors

Soft robotic grippers enable the safe manipulation of delicate objects, guaranteeing their integrity when handled and collected. Integrating sensors into these grippers can enable their proprioception but must avoid compromising flexibility or functionality. This study presents a pneumatic finger-based soft gripper with a novel piezoresistive sensor made of laser-induced graphene (LIG) embedded in dragon skin (DS), an elastomer matrix, offering continuous bending angle measurement. The LIG/DS composite is studied to confirm minimal impact on the gripper's stiffness. Mechanical and electromechanical characterizations are performed for two sensor designs, n1 and n2. Design n1 exhibits superior performance, with a gauge factor (Formula presented.), a linear response of up to 30% strain, and durability exceeding 10 000 cycles. A finite-element method analysis identifies the fingers’ neutral bending plane, guiding optimal sensor placement. Experimental validation confirms theoretical predictions and finds the ideal sensor location, achieving a linear response up to 110° with low hysteresis (8%). The sensor enables real-time monitoring of finger bending during grasping tasks, with a calibration curve linking resistance changes to bending angles. This cost-effective, stretchable, and durable sensor demonstrates high potential for soft robotic applications, offering precise and reliable proprioception without compromising the gripper's soft properties.