Dielectric elastomers (DEs) as a kind of electroactive polymers are able to transform electric energy to mechanical energy, which can be used as artificial muscle to fabricate soft actuators and soft robotics. However, fabricating DE actuators with high performance by sub-kV remains challenging. Here, we report a facile method to fabricate functional and ultrathin DE films via physical treatment (prestretch and thermal relaxation) of a thick thermoplastic elastomer film of Poly(styrene-<i>b</i>-butyl acrylate-<i>b</i>-styrene) (SBAS). The pristine SBAS film with designed block weight (15-120-15 kDa) shows sea-island seperated microstructure due to the thermodynamic incompatibility between the blocks of polystyrene (PS) and poly(butyl acrylate). Specifically, the treated SBAS films could not noly modulate the morphology and orientation of PS nanodomains for functional actuation performance, but simutaneouly lower the driving voltage to the level of sub-kV via decreasing the thickness of pristine SBAS film. Under the symmetric prestretch of physical treatment of SBAS film, the PS morphology would changes from sphere to oblate spheroid leading to improve mechanical performance, and the higher specific interface area of PS domains would also enhance the dielectric breakdown strength of SBAS films for higher actuation performance. Besides, under the unsymmetric/uniaxial prestrecth of post-treatment, the PS morphology would changes from sphere to oriented nanorod leading to mechanical anisotropy of SBAS films, which is helpful to fabricating DE actuators with anisotropic actuation for specific compact soft robots, like soft gripper and crawing robots. This facile post-treatment of thermoplastic elastomer for functional and ultrathin DE films shows a promising future for soft actuators.

Fabricating functional dielectric elastomer actuator via physical treatment of thermoplastic elastomer

ACS Spring Meeting 2021

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