Tough hydrogels, polymeric network structures with excellent mechanical properties (such as high stretchability and toughness), are emerging soft materials. Despite their remarkably mechanical features, tough hydrogels exhibit two flaws (freezing around the icing temperatures of water and drying under arid conditions). Inspired by cryoprotectants (CPAs) used in the inhibition of the icing of water in biological samples, a versatile and straightforward method is reported to fabricate extreme anti-freezing, non-drying CPA-based organohydrogels with long-term stability by partially displacing water molecules within the pre-fabricated hydrogels. CPA-based Ca-alginate/polyacrylamide (PAAm) tough hydrogels were successfully fabricated with glycerol, glycol, and sorbitol. The CPA-based organohydrogels remain unfrozen and mechanically flexible even up to -70 °C and are stable under ambient conditions or even vacuum.

Transient electronics, arising electronic devices with dissolvable or degradable features on demand, is still at an early stage of development due to the limited choices of materials and strategies. Herein, a facile fabrication method for transient circuits by the combination of room-temperature liquid metals (RTLMs) as the electronic circuit and water-soluble poly(vinyl alcohol) (PVA) as the packaging material is reported. The as-made transient circuits exhibit remarkable durability and stable electric performance upon bending and twisting, while possessing short transience times, owing to the excellent solubility of PVA substrates and the intrinsic flexibility of RTLM patterns. Moreover, the RTLM-based transient circuit shows an extremely high recycling efficiency, up to 96% of the employed RTLM can be recovered. As such, the economic and environmental viability of transient electronics increases substantially. To validate this concept, the surface patterning of RTLMs with complicated shapes is demonstrated, and a transient antenna is subsequently applied for passive near-field communication tag and a transient capacitive touch sensor. The application of the RTLM-based transient circuit for sequentially turning off an array of light-emitting-diode lamps is also demonstrated. The present RTLM-based PVA-encapsulated circuits substantially expand the scope of transient electronics toward flexible and recyclable transient systems.

Soft electronics are rising electronic technologies towards applications spanning from healthcare monitoring to medical implants. However, poor adhesion strength and significant mechanical mismatches inevitably cause the interface failure of devices. Herein we report a self-adhesive conductive polymer that possesses low modulus (56.1-401.9 kPa), high stretchability (700%), high interfacial adhesion (lap-shear strength >1.2 MPa), and high conductivity (1-37 S/cm). The self-adhesive conductive polymer is fabricated by doping the poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) composite with a supramolecular solvent (β-cyclodextrin and citric acid). We demonstrated the solution process-based fabrication of self-adhesive conductive polymer-based electrodes for various soft devices, including alternating current electroluminescent devices, electromyography monitoring, and an integrated system for the visualization of electromyography signals during muscle training with an array of alternating current electroluminescent devices. The self-adhesive conductive polymer-based electronics show promising features to further develop wearable and comfortable bioelectronic devices with the physiological electric signals of the human body readable and displayable during daily activities.

Tough hydrogels, polymeric network structures with excellent mechanical properties (such as high stretchability and toughness), are emerging soft materials. Despite their remarkably mechanical features, tough hydrogels exhibit two flaws (freezing around the icing temperatures of water and drying under arid conditions). Inspired by cryoprotectants (CPAs) used in the inhibition of the icing of water in biological samples, a versatile and straightforward method is reported to fabricate extreme anti‐freezing, non‐drying CPA‐based organohydrogels with long‐term stability by partially displacing water molecules within the pre‐fabricated hydrogels. CPA‐based Ca‐alginate/polyacrylamide (PAAm) tough hydrogels were successfully fabricated with glycerol, glycol, and sorbitol. The CPA‐based organohydrogels remain unfrozen and mechanically flexible even up to −70 °C and are stable under ambient conditions or even vacuum.

Shape morphing nanosystems have recently attracted much attention and a number of applications are developed, spanning from autonomous robotics to drug delivery. However, the fabrication of such nanosystems remains at an early stage owing to limited choices of strategies and materials. This work reports a facile method to fabricate liquid metal (LM) nanodroplets by sonication of bulk LM in an aqueous dopamine hydrochloride solution and their application in light‐induced shape morphing at the nanoscale. In this method, dopamine acts as a surfactant, which stabilizes the LM nanodroplets dispersion during the sonication, and results in downsizing of the nanodroplets. Furthermore, by adding 2‐amino‐2‐(hydroxymethyl)‐1,3‐propanediol to the suspension, self‐polymerization of dopamine molecules occurs, resulting in the formation of polydopamine (PDA)‐coated LM nanodroplets. Owing to the high photothermal conversion of the PDA, PDA‐coated LM nanodroplets are transformed from spherical shapes to ellipsoids by NIR laser irradiation. This study paves a simple and reliable pathway for the preparation of functional LM nanodroplets and their application as shape‐morphing nanosystems.

The electric actuation of room-temperature liquid metals, such as Galinstan (gallium−indium−tin), has largely been conducted in alkaline electrolyte. Addition of surface-active anions and a proper acidic pH are expected to influence the interfacial tension of the liquid metal due to a high surface charge density. Hence, it should be possible to actuate liquid metals in such acidic environments. To ascertain this, at first, the dependence of the interfacial tension of Galinstan in NaOH, acidified KI, and acidified NaCl electrolyte on the concentration of the surface-active anions OH − , I − , and Cl − , respectively, were studied. Subsequently, a systematic study of the actuation of Galinstan in acidified KI electrolyte was executed and compared to actuation in alkaline medium. In the presence of HCl and acidified NaCl electrolyte, the interfacial tension of Galinstan is only marginally altered, while acidified KI solution reduced the interfacial tension of Galinstan significantly from 470.8 ± 1.4 (no KI) to 370.6 ± 4.1 mN/m (5 M KI) due to the high surface charge density of the electric double layer. Therefore, in acidified electrolyte in the presence of surface-active anions, the electrically actuated motion of LM can be realized. In particular, the actuation of Galinstan achieves a higher average and maximum speed at lower applied voltage and power consumption for acidified KI electrolyte. The formation of high surface charge density in acidified environments signifies a paradigm shift and opens up new possibilities to tune interfacial tension and controlled LM droplet motion of room-temperature liquid metals.

Nontoxic liquid metals (conductive materials in a liquid state at room temperature) are an emerging class of materials for applications ranging from soft electronics and robotics to medical therapy and energy devices. Their sticky and corrosive properties, however, are becoming more of a critical concern for circuits and devices containing other metals as these are easily destroyed or contaminated by the liquid metals. Herein, a feasible method for fabricating highly conductive graphene‐coated liquid metal (GLM) droplets is reported and their application as nonstick, noncorrosive, movable, soft contacts for electrical circuits is demonstrated. The as‐prepared GLM droplets consist of a liquid‐phase soft core of liquid metal and a slippery outer layer of graphene sheets. These structures address the issue of simultaneous control of the wettability and conductivity of a soft electronic contact by combining extraordinary properties, i.e., nonstick, noncorrosive, yet exhibiting high electronic conductivity while in contact with metal substrates, e.g., Au, Cu, Ag, and Ni. As proof‐of‐concept, the as‐prepared GLM droplets are demonstrated as floating electrodes for movable, recyclable electronic soft contacts in electrical circuits.

Tough protein organohydrogels are fabricated by applying a solvent displacement-induced toughening (SDIT) strategy. By one-step SDIT, relatively weak and brittle protein hydrogels change to protein organohydrogels with remarkably high performance in anti-freezing, non-drying, topological healing, thermal plasticizing, mechanical toughness and stretchability.