A novel AFM based method for force measurements between individual hair strands

Area of Science:

• Biophysics
• Materials Science
• Tribology

Background:

• Understanding interactions between natural fibers like hair is crucial for various applications and fundamental science.
• Existing methods lack precision for analyzing individual fiber-to-fiber forces and surface interactions.

Purpose of the Study:

• To introduce a novel Atomic Force Microscopy (AFM)-based method for precise force measurements between individual hair strands.
• To investigate the influence of environmental factors (humidity, aqueous solutions) on hair fiber interactions.
• To characterize the anisotropic frictional properties of human hair.

Main Methods:

• Laser-cutting hair fragments to preserve surface chemistry.
• Immobilizing hair fragments onto AFM cantilevers for controlled measurements.
• Utilizing a crossed-cylinder geometry for force-distance and friction analysis.
• Conducting experiments in controlled humidity air and aqueous environments.

Main Results:

• Demonstrated the feasibility of measuring both adhesion forces and friction between individual hair strands.
• Observed significant differences in interaction forces between air and aqueous environments, highlighting the role of capillary forces.
• Characterized anisotropic friction, correlating it with the hair cuticle's micro-structure.
• Successfully extended the methodology to human hair, with potential for other natural fibers.

Conclusions:

• The developed AFM method provides a precise tool for quantifying inter-fiber forces in biological materials.
• Capillary interactions play a dominant role in hair fiber adhesion in ambient air.
• Hair's surface topography significantly influences its frictional behavior.
• This approach offers a versatile platform for studying a wide range of natural fibers.