Mechanical systems such as engines and motors rely on two principal types of motions of stiff components: linear motion, which involves an object moving from one point to another in a straight line, and rotational motion, which involves an object rotating on an axis.

An initially flat, thin, circular sheet of elastomer with embedded electrodes morphs into a saddle shape. (Image: Clarke Lab/Harvard SEAS)

Nature has developed more sophisticated forms of movement, or actuation, that can perform complex functions more directly and with soft components. For example, our eyes can change focal point by simply contracting soft muscles to change the shape of the cornea. In contrast, cameras focus by moving solid lenses along a line, either manually or by an autofocus.

Researchers have developed a method to change the shape of a flat sheet of elastomer using actuation that is fast, reversible, controllable by an applied voltage, and reconfigurable to different shapes. This could be a step towards a soft, shape-shifting material that changes shape according to electrical control signals from a computer. The devices have a simple but integrated three-dimensional architecture of electrical conductors and dielectrics and demonstrate the elements of programmablereconfiguration to create large and reversible shape changes.

The reconfigurable elastomer sheet is made up of multiple layers. Carbon nano-tube-based electrodes of different shapes are incorporated between each layer. When a voltage is applied to these electrodes, a spatially varying electric field is created inside the elastomer sheet that produces uneven changes in the material geometry, allowing it to morph into a controllable three-dimensional shape. Different sets of electrodes can be switched on independently, enabling different shapes based on which sets of electrodes are on and which ones are off.

The shape-morphing actuations have a power density similar to that of natural muscles; a capability that could transform the way mechanical devices work. Current devices could make use of more sophisticated deformations to function more efficiently such as optical mirrors and lenses. This actuation method opens the door to novel devices that may have been deemed too complicated to pursue due to the complex deformations required such as a shape-morphing airfoil.

Researchers also predicted the actuation shapes, given the design of the electrode arrangement and applied voltage.

For more information, contact Caroline Perry, Harvard Office of Technology Development, at This email address is being protected from spambots. You need JavaScript enabled to view it.; 617495-4157.

Motion Design Magazine

This article first appeared in the April, 2019 issue of Motion Design Magazine.

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