Structural Origins of Silk Piezoelectricity

Citations Over TimeTop 25% of 2011 papers

Abstract

Uniaxially oriented, piezoelectric silk films were prepared by a two-step method that involved: (1) air drying aqueous, regenerated silk fibroin solutions into films, and (2) drawing the silk films to a desired draw ratio. The utility of two different drawing techniques, zone drawing and water immersion drawing were investigated for processing the silk for piezoelectric studies. Silk films zone drawn to a ratio of λ= 2.7 displayed relatively high dynamic shear piezoelectric coefficients of d(14) = -1.5 pC/N, corresponding to over two orders of magnitude increase in d(14) due to film drawing. A strong correlation was observed between the increase in the silk II, β-sheet content with increasing draw ratio measured by FTIR spectroscopy (C(β)∝ e(2.5) (λ)), the concomitant increasing degree of orientation of β-sheet crystals detected via WAXD (FWHM = 0.22° for λ= 2.7), and the improvement in silk piezoelectricity (d(14)∝ e(2.4) (λ)). Water immersion drawing led to a predominantly silk I structure with a low degree of orientation (FWHM = 75°) and a much weaker piezoelectric response compared to zone drawing. Similarly, increasing the β-sheet crystallinity without inducing crystal alignment, e.g. by methanol treatment, did not result in a significant enhancement of silk piezoelectricity. Overall, a combination of a high degree of silk II, β-sheet crystallinity and crystalline orientation are prerequisites for a strong piezoelectric effect in silk. Further understanding of the structural origins of silk piezoelectricity will provide important options for future biotechnological and biomedical applications of this protein.

Related Papers

• → Raman spectroscopic characterization of Bombyx mori silk fibroin: Raman spectrum of Silk I(2001)156 cited
• → Tuning the structure and performance of silk biomaterials by combining mulberry and non-mulberry silk fibroin(2017)37 cited
• → Molecular Dynamics Simulation of Conformational Change of Poly(Ala-Gly) from Silk I to Silk ΙΙ in Relation to Fiber Formation Mechanism of Bombyx mori Silk Fibroin(2003)52 cited
• → Design, Expression and Solid-State NMR Characterization of Silk-Like Materials Constructed from Sequences of Spider Silk, Samia cynthia ricini and Bombyx mori Silk Fibroins(2005)31 cited
• Biological and physical aspects(2000)