(4g) Templated Crystallization: An Emerging Nanofabrication Strategy for Naturally Derived Biopolymers

My research interests lie at the intersection of materials science, biomacromolecular self-assembly and nanofabrication to engineer a new generation of biopolymer-based materials that can be interfaced with food and plants. In particular, my work is centered around silk fibroin – a naturally occurring structural protein that comes from Bombyx mori silkworm cocoons, which is biodegradable, non-toxic and edible. Over the years there has been a growing effort to reinvent silk as a technical material for a broad range of areas from drug delivery, regenerative medicine to optoelectronics. My work aims to open up a new opportunity where we develop new nanofabrication strategies to engineer silk into advanced functional materials for sustainable agriculture and enhancement of food safety and security.

In this presentation, we introduce templated crystallization of silk fibroin as a process to nanofabricate hierarchically structured materials up to centimeter scale. The process involves the use of ordered peptide supramolecular assemblies as templates to drive a phase transformation of silk fibroin from unordered to ordered conformations, thereby enabling further assembly of the silk fibroin chains into nanostructured materials (i.e. β-sheeted nanofibrils). Multiple parameters including the relative concentration between silk fibroin and peptide seeds, silk fibroin molecular weight, pH and peptide conformation are investigated to fine tune the assembly kinetics and silk polymorphs. Templated crystallization coupled with various top-down fabrication such as soft lithography and printing enables (i) epitaxial materials growth from the molecular level (i.e. disordered silk fibroin molecules) all the way up to centimeter scale in an exquisite single-pot, bottom-up system; (ii) surface functionalization with topographical control over nanofibrils assembly on pre-deposited peptide seeds; and (iii) three-dimensional manipulation of silk nanofibrils into macroscopic structures with customized shapes and controlled anisotropy. Together, these results pave the way for nanofabrication of a new generation of smart and adaptive materials built from the bottom up.