Microrheology of non mulberry silk varieties by optical tweezer and video microscopy based techniques

TL;DR

This study compares the microrheological properties of various Indian silk fibroin solutions using optical tweezers and video microscopy, revealing correlations between microstructure and viscoelastic behavior.

Contribution

It introduces a combined optical tweezer and video microscopy approach to measure viscoelastic moduli of different silk fibroin solutions at varying concentrations.

Findings

Tasar silk fibroin shows measurable viscoelastic moduli with optical tweezers.

Higher concentration solutions of Eri and Muga silk require video microscopy for analysis.

Microstructure correlates with microrheological parameters across silk varieties.

Abstract

We have carried out a comparative study of the microrheological properties of silk fibroin solutions formed from a variety of silks indigenous to the Indian subcontinent. We present the measured viscoelastic moduli of Tasar silk fibroin solution using both a single and dual optical tweezer at 0.16% and 0.25% (w/v). The bandwidth of the measurements carried out using optical tweezers is extended down to the lower frequency regime by a video microscopy measurement. Further, we have measured the viscoelastic moduli of Eri and Muga varieties of silk fibroin solutions at a higher concentration (1.00% w/v) limiting the tool of measurement to video microscopy, as the reduced optical transparencies of these solutions at higher concentration preclude an optical tweezer based investigation. The choice of a higher concentration of fibroin solution of the latter silk varieties is so as to enable a comparison of the shear moduli obtained from optical methods with their corresponding fibre stiffness obtained from wide angle X-ray scattering data. We report a correlation between the microstructure and microrheological parameters of these silk varieties for the concentration of fibroin solutions studied.