Making Faces: Universal Inverse Design of Surfaces with Thin Nematic Elastomer Sheets

TL;DR

This paper presents a method to program thin liquid crystal elastomer sheets to morph into arbitrary 3D shapes, including faces, enabling advanced applications in flexible electronics, metamaterials, and medical devices.

Contribution

It introduces an inverse design approach for programming LCE sheets to achieve any desired 3D shape through local molecular orientation control.

Findings

Successfully programmed LCE sheets to form complex shapes like faces.

Developed approximate numerical methods for shape blueprint generation.

Demonstrated precise shape transformation upon thermal activation.

Abstract

Programmable shape-shifting materials can take different physical forms to achieve multifunctionality in a dynamic and controllable manner. Although morphing a shape from 2D to 3D via programmed inhomogeneous local deformations has been demonstrated in various ways, the inverse problem -- programming a sheet to take an arbitrary desired 3D shape -- is much harder yet critical to realize specific functions. Here, we address this inverse problem in thin liquid crystal elastomer (LCE) sheets, where the shape is preprogrammed by precise and local control of the molecular orientation of the liquid crystal monomers. We show how blueprints for arbitrary surface geometries as well as local extrinsic curvatures can be generated using approximate numerical methods. Backed by faithfully alignable and rapidly lockable LCE chemistry, we precisely embed our designs in LCE sheets using advanced top-down microfabrication techniques. We thus successfully produce flat sheets that, upon thermal activation, take an arbitrary desired shape, such as a face. The general design principles presented here for creating an arbitrary 3D shape will allow for exploration of unmet needs in flexible electronics, metamaterials, aerospace and medical devices, and more.