Adhesive Double‐Network Granular Organogel E‐Skin

ABSTRACT Human skin offers multimodal sensing capabilities including tactile, thermal, and chemical detection, a feature that can be partially replicated using ionic hydrogels to create electronic skin (e‐skin). For e‐skin to properly function, it must firmly adhere to substrates. This can be achieved with stiff screws or fastener. However, the mismatch between the stiff screws or fasteners and the soft e‐skin typically compromises the robustness of the structure. Achieving reliable adhesion to the diverse range of soft substrates encountered in soft robotics remains challenging. Typical adhesives are rather soft such that they can adapt their shape to the surface roughness of the substrate. Yet, their softness risks cohesive failures. Here, we present a double‐network granular organogel (DNGOG) that integrates microfragments, which can interact with hydrophobic substrates with a secondary soft polymer network rich in ionic and hydrogen bonds. This architecture combines strong, reversible adhesion to a wide range of hydrophilic and hydrophobic substrates with a stiffness that prevents premature cohesive failures within the adhesive. Thereby, the DNGOG‐based e‐skin can combine an adhesive strength of 1.9 MPa with a tensile strength of 1.0 MPa, overcoming the long‐standing adhesion‐strength compromise of soft adhesives. The ionic conductivity of the DNGOG enables this material to sense multiple stimuli vital to humans such as their pulse, respiration, temperature, and sweat, as well as tactile feedback in soft robotic systems. This multifunctional platform offers a promising route toward next‐generation wearable and robotic e‐skin technologies.