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Fabrication and Deformation of Three-Dimensional Hierarchical Ceramic Nano-Lattices

Lucas Meza (Caltech), Dongchan Jang (California Institute of Technology), Frank Greer (), Julia Greer (Caltech)

Materials Design and Biomimetic Material Concepts

Tue 10:45 - 12:15

CIT 227

Fabrication of lightweight, mechanically-robust materials has been a long sought after engineering pursuit. Many siliceous skeleton species, e.g. diatoms, sea sponges and radiolarians, consist of hierarchically arranged open-cell ceramic lattices, whose periodicity and open structure have been linked to a combination of high strength and light weight. To discern how the individual features contribute to the overall strength and deformation of these complex biomaterials, it is important to create and to test simple model systems at each fundamental level of hierarchy. We report the fabrication and mechanical deformation of periodically arranged hollow titanium nitride nanolattices with levels of hierarchy at each length scale similar to those in many siliceous skeletal species. The structures were made using a multi-step negative pattern process involving two-photon lithography, direct laser writing, atomic layer deposition, and O2 plasma etching. The characteristic dimensions of these 3D nanolattices range from tens of nanometers (wall thickness) to microns (tube diameter) to tens of microns (unit cell) to over 100 Ám in their entirety. In-situ nano-mechanical experiments and finite element analysis of the compression of a single unit cell revealed remarkably high tensile strengths of 1.75 GPa, which correlates with an elastic limit of 1.7%, in the constituent solid. Structures showed no evidence of failure after 30 cycles of loading to an effective tensile strain of 1.6%. The amplified strength and damage tolerance exhibited by these nanolattices illustrates the role of each length scale in driving the bulk properties of bio-ceramics.