Multiscale rheology from bulk to nano using a quartz tuning fork-atomic force microscope

Area of Science:

• Materials Science
• Physical Chemistry
• Nanotechnology

Background:

• Rheological properties differ significantly at the nanoscale compared to bulk.
• A unified experimental approach is needed to understand rheology across multiple scales.

Purpose of the Study:

• To develop a single experimental platform for multiscale rheology measurements.
• To investigate rheological behavior from the nanoscale to the bulk scale.

Main Methods:

• Utilized a quartz tuning fork (QTF) force sensor integrated with an atomic force microscope.
• Employed microscale and nanoscale shear probes for tip-substrate rheological measurements with sub-nanometer resolution.
• Calibrated the system using silicone oils of varying viscosities (5–10,000 cSt).

Main Results:

• Successfully derived bulk rheological moduli for silicone oils.
• Observed an increased modulus in the tribo-nanorheology regime (<50 nm from surface).
• Confirmed this increase is attributed to the formation of layered silicone oil polymer structures.

Conclusions:

• The developed QTF-based AFM provides a robust platform for multiscale rheology.
• Demonstrated a transition in rheological behavior near surfaces due to structural changes.
• Offers a comprehensive understanding of complex fluid tribo-rheology across scales.