Hydrogels are generally thought to be formed by nano-to micrometre-scale fibres or polymer chains, either physically branched or entangled with each other to trap water. Although there are also anisotropic hydrogels with apparently ordered structures, they are essentially polymer fibre/discrete polymer chains-based network without exception. Here we present a type of polymer-free anisotropic lamellar hydrogels composed of 100-nm-thick water layers sandwiched by two bilayer membranes of a self-assembled nonionic surfactant, hexadecylglyceryl maleate. The hydrogels appear iridescent as a result of Bragg's reflection of visible light from the periodic lamellar plane. The particular lamellar hydrogel with extremely wide water spacing was used as a soft two-dimensional template to synthesize singlecrystalline nanosheets in the confined two-dimensional space. As a consequence, flexible, ultrathin and large area single-crystalline gold membranes with atomically flat surface were produced in the hydrogel. The optical and electrical properties were detected on a single gold membrane.

Artificial intelligent skins hold the potential to revolutionize artificial intelligence, health monitoring, soft robotics, biomedicine, flexible, and wearable electronics. Present artificial skins can be characterized into electronic skins ( e-skins) that convert external stimuli into electrical signals and photonic skins ( p-skins) that convert deformations into intuitive optical feedback. Merging both electronic and photonic functions in a single skin is highly desirable, but challenging and remains yet unexplored. We report herein a brand-new type of artificial intelligent skin, an optoelectronic skin ( o-skin), which combines the advantages of both e-skins and p-skins in a single skin device based on one-dimensional photonic crystal-based hydrogels. Taking advantage of its anisotropic characteristics, the resulting o-skin can easily distinguish vector stimuli such as stress type and movement direction to meet the needs of multi-dimensional perception. Furthermore, the o-skin also demonstrates advanced functions such as full-color displays and intelligent response to the environment in the form of self-adaptive camouflage. This work represents a substantial advance in using the molecular engineering strategy to achieve artificial intelligent skins with multiple anisotropic responses that can be integrated on the skin of a soft body to endow superior functions, just like the natural organisms that inspire us.

Nonvolatile ionogels are promising soft electrolyte materials for flexible electronics, but it is challenging to fabricate stable electrolytes with mechanical robustness. Here, through rationally optimizing the chemical structure of polymer matrix and ionic liquids, the high-performance ionogel electrolytes with mechanical robustness and stability were fabricated. There are double hydrogen bonding networks in the as-prepared ionogel electrolytes, one of which exists between the polymer chains while the other one existing between the polymer chains and ionic liquid molecules. By adjusting the content of the ionic liquid and the ratio of the two hydrogen bonding networks, the prepared ionogel electrolytes exhibit tunable properties with an elasticity of 1.3−30 kPa, a stretchability of more than 1800%, a fracture energy of 125.8−548.3 KJ m −3 , and a coordinated self-healing efficiency of 6.2−37.9% to satisfy the needs of different application scenarios. The assembled wearable sensors based on the high-performance ionogel electrolytes can be attached to a part of the human body, detecting various motions and body temperature. Benefiting from the nonvolatile and hydrophobic properties of the ionogel electrolytes, the wearable sensors can be operated under extreme environments including high/low temperature (−15 − 100 °C) and high humidity (100% relative humidity). It is believed that this work provides prospects for the application of wearable electronic devices.