Reversible adhesive hydrogel with enhanced sampling efficiency boosted by hydrogen bond and van der Waals force for visualized detection

It is extremely attractive to introduce reversible adhesive hydrogel into the field of sampling wipe for enhancing the sampling efficiency, which facilitates the development of understanding in fundamental science and technology innovation including interfacial interaction, flexible sensor, visualized detection and so forth. Here, a polyacrylic acid/polyvinyl alcohol-borax (PAA/PVA-B) hydrogel is proposed by introducing double-network microstructure for enhancing cohesive strength, and numerous carboxyl, hydroxyl groups as well as borax for facilitating the hydrogen and dynamic borate bond formation, ensuring its reversible adhesive capability. Benefitting from the noncovalent and dynamic covalent bonds, excellent reversible adhesion to diverse surfaces for 50 cycles without apparently decreasing the adhesive force, and high transfer efficiency of stamp patterns (about 99.8%) are successfully achieved. More importantly, efficient wipe sampling in various scenarios by the PAA/PVA-B hydrogel toward the microparticulates of three representative explosives, including military explosive of 2,4,6-trinitrotoluene (TNT, 0.6 µg) and 2,4-dinitrotoluene (DNT, 1.2 µg), improvised explosive of sulfur (S, 16 µg) could be consolidated owing to the hydrogen bonds and van der Waals force. Inspired by on-site visualization of microgramme-level explosives with this PAA/PVA-B hydrogel-based colorimetric sensor, it is expected that the present strategy could not only deepen the insights of interfacial interaction but also stretch the field of both hydrogel and sampling method to new level.