Electro-mechanical transduction of ionoelastomer junctions

Ionoelastomers are an emerging class of ion conducting materials wherein one of the ionic moieties of an ionic liquid pair is covalently attached to a polymer backbone, leading to solid-state electrolytes that selectively conduct ions of one charge. Herein, two oppositely charged ionoelastomers were prepared based on 1-ethyl-3-methyl imidazolium (3-sulfopropyl) acrylate (ES) and (1–(2–acryloyloxy–ethyl)–3–buthyl–imidazolium bis(trifluoromethane) sulfonimides (AT). At the interface of ES/AT, an ‘ionic double layer’ (IDL) is formed due to diffusion of mobile ions away from the interfacial region, resulting in a build-up of excess fixed charges with a capacitance of ~ 1 mF/cm². Thanks to the highly elastic properties of ILEs, along with stretchable electrodes based on embedded carbon nanotubes or graphene, ILE diodes can be repeatedly deformed to large strains (~ 100%) without failure. Remarkably, we have found that uniaxial stretching of an ILE diode produces a spike in the open circuit voltage, or correspondingly a current when the system is connected to an electrical load. This effect can be used for strain sensing or energy harvesting, especially for ambient mechanical energy sources with relatively low frequency and large strain.