Naturally occurring biopolymers are promising building blocks for a new generation of multifunctional materials that can work at the biotic-abiotic interface and better interact with the environment. Particularly, silk fibroin – a structural protein extracted from <i>Bombyx mori</i> silkworm cocoons, has attracted a lot of attention in the recent decades due to its potential use as a technical material in drug delivery, regenerative medicine, food coating, printable sensors and optoelectronics etc. As more manufacturing methodologies with silk fibroin are being developed, a key question yet to be answered is how to endow silk fibroin-based bulk materials with complex nanoscale features. Unlike most of the current nanofabrication strategies that mainly focused on manipulation of nanostructures from the top-down perspective, we choose to approach this question by designing specific folding and assembly pathways of silk fibroin that results in highly ordered β-sheeted nanofibrils. Atomic force microscopy (AFM) in combination with a set of correlative optical, spectroscopy and X-ray scattering techniques are employed to probe the detailed mechanism of nanofibrils formation, from the driving forces for disorder-to-order transition to sequence-structure-property relationships across scales. In particular, high resolution nanomechanical data of silk fibroin at single fibril level in both dried and hydrated states are acquired by using AFM-based bimodal force microscopy and fast force mapping. Factors including silk fibroin molecular weight and crystallinity are found to directly correlate with the nanomechanical properties.

Template-directed growth of silk nanofibrils: From assembly dynamics to nanomechanics

ACS Fall 2021

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