Electro-Mechanically Responsive Ionoelastomer Heterojunctions

Ionoelastomers, consisting of low glass-transition polyelectrolyte networks, represent soft and stretchable ionic analogs of electronic semiconductors. We have recently studied two different types of electro-mechanical responses of heterojunctions formed by contacting ionoelastomer layers of opposite polarity, both with potential applicability in soft robotic contexts. In the first case, we demonstrated that such junctions provide reversibly switchable electro-adhesion. Thanks to the nanometer-scale thickness of the ionic double layer, large Maxwell stresses and corresponding enhancements in adhesion can be generated using applied potentials of only 1 – 3 V, in contrast to the kV levels generally required for established dielectric electro-adhesives. This leads to superior performance in terms of adhesive force per electrostatic energy, as well as damage resistance. In the second case, we found that mechanical deformation of a bilayer sample provides transient electrical signals associated with rearrangement of polymer strands and counterions within the ionic double layer. This effect provides a new mechanism for electrical strain sensing and energy harvesting.