Shape-Shifting Lattices
via Multimaterial 4D Printing

(top) Predictive design method used to guide multimaterial 4D printing (bottom left) Transformed 3D shape of a human face (Gauss) and (bottom right) Image of lattice with bilayer ribs composed of four different materials of varying stiffness and thermal expansion behavior.

Boley, J.W., W.M. van Rees, C. Lissandrello, M.N. Horenstein, R.I. Truby, A. Kotikian, J.A. Lewis, and L. Mahadevan, "Shape-shifting structured lattices via multimaterial 4D printing," PNAS 116 (42), 20856-20862 (2019).

A team at the Harvard MRSEC led by Mahadevan and Lewis has created shape-shifting lattices by combining predictive design and multimaterial 4D printing. Inks composed of elastomeric matrices with tunable cross-link density and anisotropic fillers that enable precise control of their elastic modulus (E) and coefficient of thermal expansion (α) are printed in the form of lattices with curved bilayer ribs, whose composition geometry is locally programmed to achieve control over the metric tensor. By patterning bilayer ribs composed of four materials, the team can encode a wide range of 3-dimensional (3D) shape changes in response to temperature. As an exemplar, they designed and printed multimaterial planar lattices that morph into a human face (Gauss) that is geometric complex (see figure).