Adaptive dual-mode photoelectric eutectogel interface for closed-loop human-machine interaction

Human-machine interaction (HMI) devices based on conductive gel interfaces provide an effective approach for recognizing users' manipulation intentions by capturing mechanical signals. However, achieving intuitive feedback, high accuracy, and environmental adaptability remains challenging. Herein, we report a novel dual-mode photoelectric eutectogel interface (PEGI) constructed by incorporating deep eutectic solvents (DES) and ionic liquid into a photonic crystal-embedded matrix for HMI applications. The strain-induced structural color change of PEGI provides intuitive visual feedback (1.99 nm per %) and serves as a calibration reference for strain response, thereby effectively enhancing the HMI experience. Moreover, PEGI demonstrates high sensitivity, characterized by an ultra-low detection limit (< 1% strain) and a gauge factor of 3.0, along with a good linearity over a broad strain range (0–100%) and outstanding cycling stability (>5000 cycles). Significantly, PEGI remains mechanically stable and flexible under extreme conditions down to −50 °C, and exhibits exceptional stretchability exceeding 2400% at room temperature, owing to the multiple hydrogen-bond network formed between the deep eutectic solvent (betaine and ethylene glycol) and the ionic liquid. The remote end-effectors (e.g., trolley and manipulator) designed based on PEGI and a microcontroller enable continuous operation, high signal stability, and efficient interactive control guided by optical feedback. This study demonstrates the great potential of PEGI for the development of closed-loop HMI systems integrating sensing, feedback, and actuation.