We aim to create programmable materials that can swiftly adapt their structures, and henceforth their functional properties on demand. We combine studies of mechanics involving fundamental deformation mechanisms, microfabrication, and mechanical characterization techniques to merge structural and functional materials through a digitized, perturbative loop.
Programmable shape morphing
Distributed stimuli offer ways to deform local structures at fast speeds. We create a soft material architecture that consists of a mesh of optimized, planar serpentine conductive features. Programmable voltage control of electrical current enables distributed electromagnetic actuation on the surface in a static magnetic field. We found that the serpentine mesh structure exhibits a linear input-output (voltage-displacement) relationship. This unusual linear relationship of large deformation allows a model-driven approach for inverse design to reproduce complex, continuous shape-morphing processes. We also developed automated imaging methods for in-situ 3D shape reconstruction. Provided the digital actuation and in-situ sensing capability, with resolvable errors between the model-driven output and the target, we implemented an experiment-driven optimization strategy that automatically perturbs control voltages and minimizes the error according to a gradient estimation. The resulting metasurface can deform to target shapes without prior knowledge of the underlying physics.
Y. Bai, H. Wang, Y. Xue, Y. Pan, J-T. Kim, Xinchen Ni, T.L. Liu, Y. Yang, M. Han, Y. Huang*, J.A. Rogers*, and Xiaoyue Ni*, A dynamically reprogrammable surface with self-evolving shape morphing, Nature 609 (7928), 701-708 (2022)
Xinchen Ni, H. Luan, J-T. Kim, S.I. Rogge, Y. Bai, J.W. Kwak, S. Liu, D.S. Yang, S. Li, S. Li, Z. Li, Y. Zhang, C. Wu, Xiaoyue Ni*, Y. Huang*, H. Wang, J.A. Rogers, Soft shape-programmable surfaces by fast electromagnetic actuation of liquid metal networks, Nature communications 13 (1), 1-9 (2022)
Programmable thermal expansion
We have demonstrated 2D metamaterials with a widely tunable coefficient of thermal expansion, including the first demonstration of an unusual shear mode of thermal expansion. The work involves a new fabrication strategy that uses precision laser cutting to achieve bi-material serpentine lattices with micrometer-scale feature sizes. The experimental results are supported by the theoretical model and the finite element analysis (FEA) simulations. The work establishes a continuum-mechanics platform based on flexible mechanical metamaterials for advanced strain-field engineering through integrated electrical and optical sources of thermal actuation. Integrated electrical and optical sources of thermal actuation enable fast reversible control of local lattice deformation.
X. Ni, X. Guo, J. Li, Y. Huang, Y. Zhang*, and J.A. Rogers*, "Two-dimensional mechanical metamaterials with widely-tunable unusual modes of thermal expansion", Advanced Materials 31 (48), 1905405 (2019)
X. Guo, X. Ni, J. Li, H. Zhang, F. Zhang, H. Yu, J. Wu, Y. Bai, H. Lei, Y. Huang*, J.A. Rogers*, Y. Zhang*, Designing mechanical metamaterials with kirigami‐inspired, hierarchical constructions for giant positive and negative thermal expansion, Advanced Materials 33 (3), 2004919 (2021)