We present here printable high-performance
polymer actuators comprising ionic liquid (IL), soluble
polyimide, and ubiquitous carbon materials. Polymer electrolytes with high ionic conductivity and reliable mechanical
strength are required for high-performance polymer actuators.
The developed polymer electrolytes comprised a soluble
sulfonated polyimide (SPI) and IL, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C2mim][NTf2]),
and they exhibited acceptable ionic conductivity up to 1 ×
10?3 S cm?1 and favorable mechanical properties (elastic
modulus >1 × 107 Pa). Polymer actuators based on SPI/
[C2mim][NTf2] electrolytes were prepared using inexpensive
activated carbon (AC) together with highly electronconducting carbon such as acetylene black (AB), vapor grown carbon fiber (VGCF), and Ketjen black (KB). The resulting
polymer actuators have a trilaminar electric double-layer capacitor structure, consisting of a polymer electrolyte layer sandwiched
between carbon electrode layers. Displacement, response speed, and durability of the actuators depended on the combination of
carbons. Especially the actuators with mixed AC/KB carbon electrodes exhibited relatively large displacement and high-speed
response, and they kept 80% of the initial displacement even after more than 5000 cycles. The generated force of the actuators
correlated with the elastic modulus of SPI/[C2mim][NTf2] electrolytes. The displacement of the actuators was proportional to
the accumulated electric charge in the electrodes, regardless of carbon materials, and agreed well with the previously proposed
displacement model.