Transient Ionogels for AC-Driven Thermal–Tactile Sensing in Soft Robotic Manipulation
Abstract
Thermal–tactile sensing is a key capability for robotic perception, enabling temperature estimation and material discrimination during physical interaction. In soft robotic manipulation, the integration of compliant sensing technologies is essential to preserve the intrinsic adaptability of deformable end-effectors while providing meaningful information about the environment and manipulated objects. This requirement calls for sensing materials that combine mechanical compliance with stable thermal transduction and straightforward integration into soft robotic bodies. Here, we report an AC-driven thermal–tactile sensing platform based on eco-friendly ionogel that combines stable ionic sensing, dedicated signal-conditioning electronics, and deployment in robotic manipulation tasks. The ionogel is fabricated through a simple water-based solvent-casting process using natural-derived choline lactate, poly(vinyl alcohol), and poly(vinyl pyrrolidone), yielding a compliant material with temperature–dependent ionic conductivity. Unlike conventional DC-operated ionic sensors, the proposed approach exploits alternating-current excitation to mitigate polarization, ionic accumulation, and electrochemical degradation. A complete sensing unit comprising the ionogel element, compliant electrodes, encapsulation, and portable electronics was developed and characterized. The sensor exhibited reversible thermal responses from –22 to 56 °C, with a theoretical resolution of ∼0.1 °C and pressure cross-sensitivity below ∼0.05 °C/N, while maintaining robust operation under repeated measurements. The sensing platform was integrated into a Pisa/IIT SoftHand mounted on a robotic manipulator. The resulting system successfully performed temperature estimation and material recognition tasks based on thermal conductivity signatures acquired during physical interaction. These results demonstrate how ionic thermal sensing materials can be translated from material-level characterization to system-level robotic perception, providing a sustainable thermal–tactile sensing strategy for soft robotic manipulation.