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Caltech
The Kavli Nanoscience Institute

In the last decade or so it has been ubiquitously demonstrated that at the micro- and nano-scales, sample size dramatically affects material strength and deformation mechanisms. These materials show particular promise for nano-scale devices when coupled with advanced manufacturing techniques that allow complex geometries at the micron and sub-micron scales. Julia R. Greer, Ruben F. and Donna Mettler Professor of Materials Science, Mechanics and Medical Engineering; Fletcher Jones Foundation Director of the Kavli Nanoscience Institute, and her group use transmission electron microscopy in the KNI to characterize these novel nano-architected materials to understand links between processing, microstructures, and mechanical properties that can enable next generation nanotechnologies. They also use many of the deposition and lithography facilities to enable development and investigation of nanoscale architectures in applications from nanophotonics to biomedical devices to extreme mechanics. Together with the KNI's nanofabrication and characterization capabilities, the Greer group is working to push the limits of nano-architected materials.

Advances in nanoscale additive manufacturing developed in the Greer Group have enabled sub-micron resolution oxide and metallic materials which offer high potential in areas of nanotechnology. This unique class of processing opens new questions and opportunities to explore within the nanoarchitected materials space. Characterization of link between microstructure and emergent properties in these systems is singularly enabled through transmission electron microscopy techniques.

Nano-architected materials enable unprecedented combinations of properties, for example damage tolerance, resilience to supersonic impact, and stimulus-induced reconfigurability at extremely low densities [1,2]. A major translational challenge is the lack of fabrication methods capable of producing nano-architected features over large volumes and short throughput times. Current state-of-the-art manufacturing methods, such as two photon lithography and stereolithography, either lack the sufficient resolution to produce nano-scale features or are limited in scaling up the production of nano-architected materials; i.e. a sample with overall dimensions of a few hundred micrometers requires tens of hours to write.

The research groups of Professors Julia Greer and Andrei Faraon, William L. Valentine Professor of Applied Physics and Electrical Engineering, are jointly developing a scalable fabrication platform for nano-architected materials (Fig. 1). By utilizing interference lithography, enabled by optical metasurfaces and laser scanning, researchers can produce nano-architected sheets with overall dimensions of several centimeters and with internal features on the order of a few hundred nanometers (Fig. 2). Such precision in internal architecture is enabled by the ability of the optical metasurfaces to accurately control the spatial polarization and phase of the incoming light in order to generate complex near-field 3D intensity distributions [3]. The sub-wavelength features of optical metasurfaces overcome the challenges of conventional phase masks with limited diffraction efficiencies, which are crucial for producing high contrast structures and for controlling the 3D geometry at the nanoscale.

Initial investigations of the impact behavior of the produced nano-architected sheets [4] highlight their high energy dissipation and potential for ultra-light ballistic armor. These results indicate that interference lithography constitutes a scalable approach for fabricating polymer-based impact resilient nano-architected sheets, hence establishing a viable pathway for real life applications and commercialization of nanolattices.

References:

  1. Meza, L. R., Das, S. & Greer, J. R. Strong, lightweight, and recoverable three-dimensional ceramic nanolattices. Science (80-. ). 345, 1322–1326 (2014) doi: 10.1126/science.1255908.
  2. Portela, C. M., Edwards, W. B., Veysset. D., Sun, Y., Nelson, K., A., Kochmann, D., M. & Greer, J. R. Supersonic impact resilience of nanoarchitected carbon. Nat. Mater. 292, 6294 (2021) doi:10.1038/s41563-021-01033-z
  3. Kamali, S. M., Arbabi, E., Kwon, H. & Faraon, A. Metasurface-generated complex 3-dimensional optical fields for interference lithography. Proc. Natl. Acad. Sci. 116, 21379–21384 (2019) doi: 10.1073/pnas.1908382116.
  4. Kagias, M., Lee, S. Friedman, A., Zheng, T., Faraon, A. & Greer, J. (In preparation)