Fast response of actuators with self assembly nanoparticle electrodes and ionic liquids

In ionomeric polymers, the accumulation or depletion of excess charges (ions) at the electrodes under an applied voltage will generate strain in these regions. This can be made use of for electromechanical transduction devices such as actuators and sensors[1]. Figure 1 illustrates schematically an ionomeric polymer bending actuator in which the accumulation and depletion of cations at the cathode and anode, respectively, create bending of the ionomeric polymer sheet under an applied voltage. In order to increase the charge density and population at the electrodes so that a large strain and high force output can be realized, various ionomeric polymer/conductive network composites (CNC) electrodes (analogous to the porous electrodes in the supercapacitors) have been developed to form ionomeric polymer/CNC actuators (IPCNC) in the past 15 years[2–3]. A schematic of a typical bending actuator thus developed is shown in Figure 2, which in general has a three layer structure, i.e., two porous electrode layers in the form of the conductive network/ionomer composite separated by a neat ionomer layer. IPCNC actuators are attractive because it can be operated under a few volts. On the other hand, IPCNC actuators suffer a low actuation speed which is often in tens of seconds range, low efficiency (<3 %), and low elastic energy density, all of which should be improved in order to meet the demands of a broad range of polymer electromechanical applications.