Iker Boyano

Electrochemistry and conducting polymers: soft, wet, multifunctional and biomimetic materials

Volume, colour or stored charge change in parallel to the counterion content inside polyconjugated materials during reverse electrochemical control in liquid electrolytes (soft and wet materials). Devices like artificial muscles, smart windows working as mimicking skins, electron-ion transducers and others, always mimicking biological functions can be constructed and controlled under the same electrochemical property (multifunctionality). Sensing and actuating properties occur simultaneously, approaching them to intelligent biological materials.

Nucleation, non-stoiquiometry, and tactile muscles with conducting polymers

The formation of nuclei of oxidized and dark material on a film of reduced, compacted and clear material was followed from electrochromic films of different conducting polymers, providing that this type of nucleation is a general fact of those materials, as established by the Electrochemically Stimulated Conformational Relaxation model. When the nucleation is stopped at any intermediate state of the nuclei growth, by switching off the polarization, the reduced and clear regions are oxidized at expenses of the oxidized ones. Any intermediate and uniform colour is attained by switching off the polarization at different times, proving the non-stoichiometric nature of the oxidized material. That means that any intermediate composition can be attained and that infinitesimal changes of the composition are possible. Any property of the material linked to the composition also will change in a continuous and infinitesimal way. Those infinitesimal changes linked to the reverse electrochemical reactions are strongly influenced by any physical or chemical change: here we present a tactile sensing artificial muscle.

Macroscopic devices and complex movements developed with artificial muscles

Conducting polymer-based actuators undergo volumetric changes as they are oxidized or reduced, from which mechanical work can be obtained. Polypyrrole (Ppy)-based actuator devices have attracted recent interest because of their similarities with the natural muscles. However, the operation of these and others actuators has largely been constrained to microscopical world. Macroscopical operation is clearly desirable for many potential applications. We have fabricated a new macroscopical actuator device based on PPy acting in liquid media. Using trilayers (PPy film/adhesive polymer /PPy film), and rigid pieces articulate actuators of 9,5 cm in long have been developed. The position of the trilayers at the device and its design simulate the movement of a finger where the movements of each trilayer are as articulations. These materials present a high degree of mobility, a good energy density, a medium speed of response and low operation voltages; these features are desirable for robotic applications. A simple equation based on electrochemical characterization of trilayer can predict device performance from load conditions. A lineal join for a double articulated (finger-like) device using macroscopical trilayer actuator has been demonstrated.

Theoretical models and electrochemical behavior of polyconjugated materials for EAPAD

The electrochemically stimulated conformational relaxation model (ESCR) allows a good description of the chronoamperometric responses of polyaniline in acetonitrile solutions under relaxation control. Compaction, relaxation and diffusion controlled oxidation with penetration of counterions and increase of volume can be defined theoretically. Those three components include structural (macromolecular) aspects and electrochemical descriptions. The model is self-consistent: the same theoretical equation allows to simulate the influence of the different variables on the experimental results.