To enable dynamic interaction with materials, we aim to create closed-loop programmable matter that can swiftly adapt their microstructures, and henceforth their functional properties on demand. We combine studies of micro/nanomechanics involving fundamental deformation mechanisms, microfabrication, and mechanical characterization techniques to merge structural and functional materials through a digitized, perturbative loop.
Structure: The basis of programmable matter is a highly adaptive structure that allows reconfiguration of properties. The emerging mechanical metamaterials offer some tunability of, e.g., stiffness, Poisson’s ratio, and coefficient of thermal expansion. However, the available routes to access desired mechanical properties of architected materials are mostly periodic, manual, and passive designs, and rely on intensive simulations and bug-fixing tests. We pursue to understand spontaneous, complex microstructures in deforming materials to create novel disordered artificial materials.
Process: We explore ways to integrate precise actuation and control to the architected materials for dynamic structural reconfiguration. We have demonstrated a fabrication strategy that uses precision laser cutting to achieve bimaterial serpentine lattices with micrometer-scale feature sizes. Integrated electrical and optical sources of thermal actuation enable fast reversible control of local lattice deformation.
Properties: An important missing piece of the current development of intelligent materials is self-diagnosis. We study novel non-destructive testing methodologies to monitor the mechanical properties of materials. We are especially interested in developing precision measurement methods to resolve failure-precursor micro-deformation. An in-depth understanding of their underlying mechanisms will allow us to predict for catastrophic failure within the reversible deformation regime.
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. Ni*, H. Zhang, D.B. Liarte, L.W. McFaul, K.A. Dahmen, J.P. Sethna, and J.R. Greer, "Yield precursor dislocation avalanches in small crystals: the irreversibility transition", Physical Review Letters 123 (3), 035501 (2019)
X. Ni*, S. Papanikolaou, G. Vajente, R.X. Adhikari, and J.R. Greer, "Probing microplasticity in small-scale fcc crystals via dynamic mechanical analysis", Physical Review Letters 118, (15), 155501 (2017)
J.P. Sethna*, M.K. Bierbaum, K.A. Dahmen, C.P. Goodrich, J.R. Greer, L.X. Hayden, J.P. Kent-Dobias, E.D. Lee, D.B. Liarte, X. Ni, K.N. Quinn, A. Raju, D.Z. Rocklin, A. Shekhawat, and S. Zapperi, "Deformation of crystals: Connections with statistical physics", Annual Review of Materials Research 47 (1) (2017)
X. Ni, J.R. Greer, K. Bhattacharya, R.D. James, and X. Chen*, "Exceptional resilience of small-scale Au30Cu25Zn45 under cyclic stress-induced phase transformation", Nano Letters 16 (12), 7621 (2016)