Stretchable self-sensing conductive hydrogel with tunable photothermal response and actuation capability

Hydrogel-based actuators have shown great potential in the field of biomimetic soft robots due to their excellent flexibility and tunable mechanical properties. Despite considerable research efforts aimed at advancing hydrogel-based actuator technology, these actuators have not yet fully replicated the ``recognition-judgment-execution" cycle characteristic of conscious, intelligent organisms, primarily due to the absence of integrated sensing mechanisms. To address this gap and mimic the intelligent actuation patterns of conscious organisms, we have developed an attractive soft actuator that combines substantial contraction capability with sensing functionality. This actuator innovatively integrates piezoresistive strain sensing and photo/thermal actuation functions within a single hydrogel material including gelatin, polyvinyl alcohol and MXene (GPM), enabling remote near-infrared (NIR) light-triggered actuation control. We propose a method of storing and releasing elastic potential energy, which can generate a high contraction force of up to 600 kPa, effectively overcoming the limitations of traditional osmosis-based actuation mechanisms in hydrogels. Moreover, the shape changes during actuation trigger the migration of MXene and significant alterations in the conductive network, endowing the GPM hydrogel with a wide sensing range (1–200% tensile strain), fast response time (191 ms), and excellent output signal linearity. Consequently, the actuator acquires self-sensing capabilities to monitor its deformation state in real time. Ultimately, inspired by the biological characteristics of snails, we designed an intelligent adaptive actuator capable of actively senseing external environmental stimuli and consciously adjusting its shape change accordingly. This integrated sensing-actuation hydrogel provides crucial insights and theoretical support for advancing artificial intelligence soft robots with higher autonomy and complexity.