Abstract
Dielectric elastomer actuators (DEAs) have shown great potential in the field of robotics, energy harvesting, or haptics for wearables. However, existing DEA materials typically require prestretching and exhibit time-dependent deformations due to their inherent viscoelastic properties. In this work, we address these issues by designing and synthesizing a polyurethane acrylate (PUA) DEA copolymerized with a polar crosslinker, polyethylene glycol diacrylate (PEGDA), to reduce viscoelastic effects through chemical crosslinking. We realized a buckling-mode actuator that displays out-of-plane deformations triggered by an electric field without the need for prestretching. Copolymerization with PEGDA showed improved dynamic response actuation performances compared to pristine PUA, wherein the former reached 90% of its maximum actuation in <1 s. In addition, precise and stable actuation was achieved, reducing viscoelastic drifts to a negligible amount. Despite the higher elastic modulus of the DEA incurred by the chemical crosslinks, the polar groups present in the PEGDA comonomer effectively increased the dielectric constant. As such, a higher area strain was achieved in comparison to that exhibited by low viscoelastic elastomers such as silicone. By eliminating the need for prestretching, rigid components can be avoided, thereby enabling greater prospects for the integration of fast response and stable DEAs into soft bodies.
Highlights
Dielectric elastomers (DEs) are a class of smart materials that have the ability to convert mechanical energy into electrical energy and vice versa[1,2]
Synthesis of polyurethane acrylate (PUA)–polyethylene glycol diacrylate (PEGDA) copolymer films CN9021 was mixed with different concentrations of PEGDA (5, 10, and 15 wt%), and 1 wt% of AIBN was added to the mixture and mixed thoroughly
Pristine CN9021 films were denoted as PUA, whereas copolymer films were denoted as PUA–PEGDA-X, with X representing the weight percent of PEGDA
Summary
Dielectric elastomers (DEs) are a class of smart materials that have the ability to convert mechanical energy into electrical energy and vice versa[1,2]. The basic structure of a dielectric elastomer actuator (DEA) device is composed of a DE film sandwiched between two compliant conductive electrodes. When a DEA is subjected to a voltage, opposite charges accumulate at the two electrodes, leading to compression of the DE film due to the Maxwell pressure P. As a result of this compressive force, the thickness of the DE film is reduced while the area expands. The Maxwell pressure P generated is expressed in Eq 1, where ε0 is the vacuum permittivity, ε is the dielectric constant, V is the voltage applied across the dielectric and z is the thickness of the dielectric material. At strains
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