The NanoBeamBalance: a passive, tensile-test device for the atomic force microscope

Area of Science:

• Biophysics
• Materials Science
• Nanotechnology

Background:

• Atomic Force Microscopy (AFM) is a powerful tool for nanoscale force measurements.
• Current AFM methods face challenges in sample preparation and manipulation for certain measurements.
• Developing novel accessories can enhance AFM capabilities for specific applications.

Purpose of the Study:

• To introduce an innovative add-on device for AFM that expands force measurement capabilities.
• To demonstrate a new method for tensile measurements of microscopic samples.
• To investigate the mechanical properties of collagen fibers under varying conditions.

Main Methods:

• A passive add-on mechanism was designed to translate vertical AFM tip motion into horizontal sample support pad motion.
• The device was tested using collagen fibers (a few μm in diameter) from rat tail tendon.
• Tensile measurements were performed in the longitudinal direction on hydrated and dried samples, with and without glutaraldehyde cross-linking.

Main Results:

• The add-on device facilitates easier deposition of microscopic samples from suspension onto flat surfaces.
• Tensile measurements on collagen fibers showed a five-fold decrease in stiffness upon rehydration from a dried state.
• Slow cross-linking with glutaraldehyde led to a gradual increase in the stiffness of rehydrated collagen fibers.

Conclusions:

• The developed AFM add-on device offers a significant improvement for force measurements, particularly tensile testing of microscale samples.
• Hydration state dramatically affects the mechanical properties of collagen fibers, with rehydration leading to reduced stiffness.
• Glutaraldehyde cross-linking can modulate and restore the tensile stiffness of collagen fibers, offering insights into biomaterial modification.