Multiscale modelling of human hair

Area of Science:

• Multiscale modeling
• Materials science
• Biophysics

Background:

• Human hair fibers exhibit complex mechanical properties.
• Understanding these properties is crucial for applications in cosmetics and materials.

Purpose of the Study:

• To develop a multiscale modeling approach for human hair fiber mechanics.
• To investigate the relationship between protein unfolding, temperature, and hair yield stress.
• To simulate the mechanical behavior of hair macrofibrils.

Main Methods:

• Molecular dynamics simulations of protein unfolding.
• Statistical mechanical modeling based on folded/unfolded states.
• Particle-based mesoscale simulations of hair macrofibrils.
• Experimental validation through tensile testing of hair fibers at elevated temperatures.

Main Results:

• Unfolding force of coiled coil proteins is approximately 1 nN.
• A statistical mechanical model predicts a linear decrease in yield stress with increasing temperature.
• Experimental results confirm the model's prediction of temperature-dependent yield stress.
• Simulations of macrofibrils show thermal properties consistent with the two-state model.

Conclusions:

• The multiscale modeling approach accurately captures human hair mechanics.
• Temperature significantly influences hair fiber yield stress due to protein unfolding.
• The study provides insights into the composite structure and mechanical behavior of hair at different scales.