Shape-Morphing Dielectric Elastomer Devices
Date
May 16, 2022
Author(s)
Hajiesmaili, Ehsan
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Citation
Hajiesmaili, Ehsan. 2022. Shape-Morphing Dielectric Elastomer Devices. Doctoral dissertation, Harvard University Graduate School of Arts and Sciences.
Abstract
Dielectric elastomer actuators (DEAs) provide fast and reversible actuations with power and energy densities that are akin to natural muscles and high energy efficiencies compared to other soft actuators. Their actuation modes, however, have been limited to linear and bending, limiting their applications to devices with simple modes of deformations. This thesis presents methods for creating shape-morphing dielectric elastomer actuators and devices to produce complex out-of-plane deformations for applications such as biomimicry of swimming and flying locomotion and haptic displays.
Morphing a flat sheet into a three-dimensional shape requires spatial distribution of the deformation, varying along the surface of the sheet. Two shape-morphing mechanisms for dielectric elastomer actuators are introduced in this thesis: one is based on creating spatially varying internal electric fields determined by the overlapping of adjacent electrodes in a multilayer DEA, and the other is based on creating spatially distributed anisotropic actuations whose local actuation directions are determined by patterns of incorporated stiff rings. Morphing into simple shapes such as cones, hemispherical caps and saddles are demonstrated.
To produce more complex target shapes, solution to the inverse problem of design is required to determine the design of the actuators that morph into desired target shapes when actuated. The two shape-morphing methods based on the design of the electrodes and patterned stiff rings are combined to enable local control of both actuation magnitudes and directions, resulting in a simple analytical solution to the inverse problem. Morphing into complex target shapes such as a human face is demonstrated.
To create shape-morphing DEAs that can be reprogrammed to morph into a variety of shapes on demand, arrays of DEAs are created and addressed using projected lights. This is enabled by integrating percolating networks of semiconducting nanoparticles into the design of the electrodes, and further opens the design space for DEA-based devices. Example of a wearable haptic device is demonstrated and methods for localization of optical addressing and mechanical actuations are presented.
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