Ex situ synergistic reinforcement of a MOF-based supramolecular polymer enables tough, highly flexible, and responsive artificial epidermis-inspired hydrogels

Abstract

Metal–organic frameworks (MOFs) have numerous applications, such as energy storage, medical delivery, and wastewater remediation. Nevertheless, their applications to conductive hydrogels are restricted due to their limited dispersion, and aggregation within the network leading to limited stretchability, susceptibility to damage during cyclic activities, and reduction in the lifetime of the sensor. To overcome these issues, the selection of a suitable solvent medium, surfactant, and surface chemistry of the polymer chain in the hydrogel network are the primary factors. Herein, we created a flexible and tough, poly(lauryl methacrylate-acrylamide)@cobalt-manganese metal organic framework supramolecular composite hydrogel. Cetyltrimethylammonium bromide (CTAB), a cationic surfactant, and polymer chains facilitated the uniform distribution of the Co-Mn-MOFs. Hydrophobic interaction along with the other supramolecular interactions leads to synergistic reinforcement of the MOFs leading to uniform dispersion of the MOFs. The subsequently produced Co-Mn-MOF-based supramolecular hydrogels display remarkable anti-fatigue resistance, ultra-stretchability (1655%), toughness (447 kJ m⁻³), high conductivity of 0.33 S m⁻¹, and a strain detection range from minute to large (0.5–700%) with a gauge factor of 9.47, and can be sculpted in diverse 3d-like designs. A sensor was developed and utilized to detect various human actions, and varied levels of strain and pressure, and was applied as an artificial epidermis. We believe that this approach has potential for creating wearable strain sensors, artificial skin, and MOF-based smart electronics.