A Tough and Reusable Ionogel Adhesive for Flexible Strain Sensor

Abstract

Ionogels have gained increasing attention in the field of flexible electronic devices. However, it is a huge challenge to prepare ionogels with high toughness and adhesive property. In this study, we present a straightforward approach to fabricating tough and reusable ionogel adhesives by randomly copolymerizing two monomers with varying solubilities in an ionic liquid solvent. Specifically, acrylamide (AM) and methacryloxyethyltrimethylammonium bis(trifluoromethanesulfonyl)imide ([MATAC][TFSI]) are copolymerized in situ in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]) to form phase-separated ionogels, wherein the hydrogen-bond-rich phases and solvent-rich phases contribute to enhancing toughness. The abundant noncovalent interactions provide the robust internal cohesive force, which provides ionogels a stable adhesion ability during the cyclic adhesion–peeling process. The resulting ionogel adhesive exhibits elevated fracture strength (2.75 MPa), impressive toughness (9.58 MJ/m³), non-disposable adhesiveness (0.692 MPa), and exceptional environmental stability. Moreover, the sensor prepared by ionogel adhesives demonstrates fatigue resistance and a wide detection range, thus holding potential for the development of advanced and sustainable flexible electronic devices.