Direct Measurement of Extension and Force in Conductive Polymer Gel Actuators

Abstract

The synthesis of a polythiophene-based conductive polymer gel is described. Preliminary measurements of the electrochemically driven extension and force response of this gel are reported when driven under the action of an applied square-wave potential. Over each square wave interval (i.e., one oxidation pulse followed by one reduction pulse), the axial change in dimension was found to be approximately 2%. Some hysteresis was noted in that the cylindrical specimens did not return to their original axial dimension. The axial pressure generated by the expansion of the gel against a fixed surface was also measured and found to be on the order of 15 kPa -4 -

Conjugated Polymer Actuators for Biomedical Applications

“…These devices can exert greater actuation stresses, as well as yield direct measurements of actuator metrics such as stress and strain, and are thus particularly useful. Free standing or clamped samples, first used by Francois et al [26] and Yoshino et al, [197] have been investigated by De Rossi and co-workers, [41,42,128,132,134,139,188,191] Bay and co-workers, [34,40,177] Kaneto and co-workers, [29,30,88,119,184±186] Wallace and co-workers, [94,141,145,160] and others [35,55,90,147] to study actuation and to characterize performance. Expansion in the direction of film thickness has also been reported, [36,151,175,228] but not yet much exploited in devices.…”

“…This means that if charge (or current) is used to control the actuator, there is no hysteresis. [29,35,121] Although the solvent does not appear in the above equations, the ions are solvated [106,111±113,116,122±126] (except in ionic liquids), and, in aqueous electrolytes particularly, this water transport accounts for much, if not most, of the strain. Solvent transport can also occur independently of ion transport, [127] owing to, for example, osmotic pressure.…”

Force generation from polypyrrole actuators

“…Forces in the range of 100 mN -300mN have been reported for polypyrrole films under isometric conditions [10][11][12] . Polythiophene gel samples have been shown to produce approximately 70 mN force in compression [13] .…”

Bioinspired Design of Dynamic Materials

“…Examples include pH-responsive, [6,7] temperatureresponsive, [8][9][10] electroresponsive, [11][12][13][14] and photoresponsive hydrogels. [15,16] pH-responsive and temperature-responsive hydrogels have been particularly prevalent in the biomaterials science literature, with initial examples extending back to the 1980s.…”