Orientational Mapping Augmented Sub-Wavelength Hyper-Spectral Imaging of Silk

Area of Science:

• Materials Science
• Biophysics
• Spectroscopy

Background:

• Molecular alignment dictates material properties, but direct measurement in complex biomaterials like silk is challenging.
• Understanding silk's unique properties requires linking its molecular alignment to its amorphous-crystalline structure.

Purpose of the Study:

• To develop and demonstrate a high-resolution method for mapping molecular orientation within individual silk fibers.
• To investigate the relationship between molecular alignment and the structural composition of silk.

Main Methods:

• Utilized synchrotron-based, polarization-dependent infrared (IR) absorbance spectroscopy with attenuated total reflection.
• Employed hyper-spectral IR imaging at spatial resolutions of 4.2 μm and 1.9 μm.
• Prepared free-standing longitudinal and lateral micro-slices of silk fibers using microtome for analysis.

Main Results:

• Achieved orientation mapping of the internal silk fiber structure with unprecedented spatial resolution.
• Measured orientational sensitivity of absorbance in the molecular fingerprint region, specifically amide bands of β-sheet polypeptides.
• Demonstrated silk amorphization using ultra-short laser single-pulse exposure.

Conclusions:

• The developed method enables direct measurement of molecular alignment in complex biomaterials like silk fibers.
• Provides insights into the structure-property relationships governing silk's extraordinary characteristics.
• Offers a new approach for material characterization and modification.