Seminar | March 17 | 2-3 p.m. | 390 Hearst Memorial Mining Building
Prof. Xun Wendy Gu, Stanford University, Mechanical Engineering
Many nanomaterials (e.g. graphene, metallic nanowires, and ceramic nanospheres) exhibit extraordinary strength, ductility and flaw tolerance. These nanoscale size effects can be transmitted to the bulk by arranging nanostructures in 3D hierarchical architectures with optimized structural topologies, but these nano-architected structures are challenging to construct using conventional manufacturing techniques.
We present the use of two-photon lithography to fabricate 3D copper lattices made up of micron-sized beams connected at solid nodes in the octet geometry. Mechanical testing reveals that the porous Cu lattice has higher strength than monolithic copper with the same volume and microstructure. This counterintuitive behavior results from size-dependent strength enhancement within lattice beams coupled to the strong and lightweight structural geometry.
We also explore the use of self-assembly to form mechanically robust nanocomposites from solution-processed nanoscale building blocks. Polystyrene grafted Au nanoparticles are self-assembled at a fluid interface to form ordered, superlattice thin films with sub-10 nm features. The mechanical behavior of superlattice thin films depends critically on polystyrene molecular weight and grafting density, and the degree of lattice disorder.
Xun Wendy Gu did her PhD at CalTech, is completing a postdoc in the Alivisatos lab here at UCB Chem (Go Bears!), and starting as an assistant professor of Mechanical Engineering at Stanford this summer.