Charge-Dependent Flexural Rigidity of a Conductive Polymer Laminate for Bioinspired Non-thermal Compliance Modulation

Material-level stiffness modulation allows for the creation of controllable energy-dissipating structures for auxiliary and training exoskeletons and the manipulation of delicate objects and tissues. These use cases require simple control systems and disfavour thermally driven solutions. Many natural mechanisms that involve stiffness modulation rely on reversible charge-driven modifications of internal constituents, inspiring the development of analogous technologies. This paper investigates flexural rigidity variation in an electronically conducting polymer (PEDOT:PSS) laminate concurrently with bending actuation. The flexural rigidity of the laminate increased by 45% as a result of a low input voltage (1.7 V) application. The addition of an ion-diffusion promoter (polyethylene oxide) amplified the stiffness response with minimal effect on actuation. The rapid response (up to 15 s), non-thermal working mechanism, safe materials, and simple control make this solution an attractive interface to various forms of life.