Design of large-span stick-slip freely switchable hydrogels via dynamic multiscale contact synergy

Abstract

Solid matter that can rapidly and reversibly switch between adhesive and non-adhesive states is desired in many technological domains including climbing robotics, actuators, wound dressings, and bioelectronics due to the ability for on-demand attachment and detachment. For most types of smart adhesive materials, however, reversible switching occurs only at narrow scales (nanoscale or microscale), which limits the realization of interchangeable surfaces with distinct adhesive states. Here, we report the design of a switchable adhesive hydrogel via dynamic multiscale contact synergy, termed as DMCS-hydrogel. The hydrogel rapidly switches between slippery (friction ~0.04 N/cm2) and sticky (adhesion ~3 N/cm2) states in the solid-solid contact process, exhibits large span, is switchable and dynamic, and features rapid adhesive switching. The design strategy of this material has wide applications ranging from programmable adhesive materials to intelligent devices.

Self-Adhesive, Strong Antifouling, and Mechanically Reinforced Methacrylate Hyaluronic Acid Cross-Linked Carboxybetaine Zwitterionic Hydrogels

“…Based on the difference of hydrophobicity of diverse HA-CB hydrogel surfaces and the fact that the adhesive mechanism of HA-CB hydrogels was similar to the SB zwitterionic adhesive hydrogel, the dipole–dipole interactions between positively charged quaternary ammonium and negatively charged carboxylic acid groups on CB zwitterionic groups and the polar groups on glass substrate surface were the inducement conditions of the adhesive behavior. The surface with a low water contact angle presented a moist microenvironment; water molecules could shield the adhesive group from the physical interaction with the substrates. , Because zwitterionic groups preferentially bound to water molecules to lose the dipole–dipole interaction with the substrate, the improved hydrophobicity of the hydrogel surface weakened the barrier effect of the water molecules and thus enhanced adhesive strength. In addition, the HA-CB 20.0 hydrogel was adhesive to skin, glass, stainless steel, rubber, and plastic, exhibiting certain universality.…”

“…The surface with a low water contact angle presented a moist microenvironment; water molecules could shield the adhesive group from the physical interaction with the substrates. 24,25 Because zwitterionic groups preferentially bound to water molecules to lose the dipole−dipole interaction with the substrate, the improved hydrophobicity of the hydrogel surface weakened the barrier effect of the water molecules and thus enhanced adhesive strength. In addition, the HA-CB 20.0 hydrogel was adhesive to skin, glass, stainless steel, rubber, and plastic, exhibiting certain universality.…”

Optically Controlled Solid-to-Liquid Phase Transition Materials Based on Azo Compounds

“…Once the bonding is complete, the debonding will be difficult without damaging the surface of objects, and the adhesives cannot be used twice (irreversible). To achieve reversible adhesion, some switchable adhesives that respond to light, temperature, or a magnetic field have been developed. − The greatest advantage of photoswitchable adhesives lies in the spatiotemporal resolution of light, enabling changes in the local adhesive force on demand. Ordinary non-OPTM azo materials can achieve photoswitchable viscosity by photosoftening and hardening, , while the greater advantage of photoliquefiable azo materials is that they are easy to remove, to achieve recycling …”

Recent advances in adhesive materials used in the biomedical field: adhesive properties, mechanism, and applications

“…Excellent adhesive performance is required in the field of intelligent devices. 42,197 Hydrogels are materials that contain a lot of water, which can provide a transport pathway for conductive ions, and are promising candidates for the manufacture of artificial skin and strain sensors. Most elastomers, which consist of semiconductors and metals, detach from each other under large strain, resulting in the breakdown of the conductive network and loss of conductive stability and sensing properties.…”