A self-sustained hydrogel oscillator, fueled by constant light, exhibits omnidirectional oscillation and powerful phototactic locomotion.

Significance: Here cheap candle soot is utilized to make superhydrophobic photothermal icephobic surfaces. The candle soot provides the hierarchical structure for superhydrophobicity; meanwhile, sunlight can be trapped in the hierarchical structure to enhance the light absorption leading to a high photothermal efficiency. The superhydrophobicity can help maintain the excellent photothermal performance. Firstly, the superhydrophobic candle soot surface can remove the melted water immediately leaving a dry surface, which avoids the reflectance and thermal mass of melted water and thus reduces the heat loss. Secondly, the surface is capable of self-cleaning; dust and other contaminants can be washed away by rain or melted water to prevent the blocking and scattering of sunlight, highly benefiting the maintaining of long-term high photothermal efficiency.

Mimicking biological neuromuscular systems’ sensory motion requires the unification of sensing and actuation in a singular artificial muscle material, which must not only actuate but also sense their own motions. These functionalities would be of great value for soft robotics that seek to achieve multifunctionality and local sensing capabilities approaching natural organisms. Here, we report a soft somatosensitive actuating material using an electrically conductive and photothermally responsive hydrogel, which combines the functions of piezoresistive strain/pressure sensing and photo/thermal actuation into a single material. Synthesized through an unconventional ice-templated ultraviolet–cryo-polymerization technique, the homogenous tough conductive hydrogel exhibited a densified conducting network and highly porous microstructure, achieving a unique combination of ultrahigh conductivity (36.8 milisiemens per centimeter, 10³-fold enhancement) and mechanical robustness, featuring high stretchability (170%), large volume shrinkage (49%), and 30-fold faster response than conventional hydrogels. With the unique compositional homogeneity of the monolithic material, our hydrogels overcame a limitation of conventional physically integrated sensory actuator systems with interface constraints and predefined functions. The two-in-one functional hydrogel demonstrated both exteroception to perceive the environment and proprioception to kinesthetically sense its deformations in real time, while actuating with near-infinite degrees of freedom. We have demonstrated a variety of light-driven locomotion including contraction, bending, shape recognition, object grasping, and transporting with simultaneous self-monitoring. When connected to a control circuit, the muscle-like material achieved closed-loop feedback controlled, reversible step motion. This material design can also be applied to liquid crystal elastomers.