sc9b05261_si_001.pdf (1.63 MB)
Peeling and Mesoscale Dissociation of Silk Fibers for Hybridization of Electrothermic Fibrous Composites
journal contribution
posted on 2019-12-13, 22:13 authored by Lili Lv, Xiangsheng Han, Xiaochen Wu, Chaoxu LiNatural silk cocoons have fibrillary structure at several
levels
of length scales, which offered mechanical properties superior to
many artificial silk materials. Despite the fact that many solvents
had been endeavored to extract natural nanofibrils for the construction
of functional materials, silk microfibrils have not been produced
in scale thus far. Most reported solvents tended to exfoliate silk
fibers directly into nanofibrils, due to their abilities of silk-dissolution
and/or hydrolysis. In this study we showed that urea could preferentially
peel and dissociate natural silk fibers into silk microfibrils with
the diameter of 102 nm and large aspect ratios, without
giving conspicuous hydrolysis and loss of β-sheets. Having colloidal
stability analogous to individual silk nanofibrils, the resultant
microfibrils could further be engineered into films and composites
through conventional filtration and liquid casting. By reserving the
orienting and nonslipping fibril bundle structures, these mesoscale
building blocks promised mechanical properties for films and composites
superior to those of silk nanofibrils. By hybridizing with Ag nanowires,
electrothermic fibrous composites were produced. Having mechanical
flexibility, folding endurance, and rapid electrothermic response
(e.g., 115 °C within 50 s) under low voltages, these biocompatible
electrothermic pads show applications in wearable and thermotherapy
fields for medical thermotherapy domains.