Reliable measurements of interfacial slip by colloid probe atomic force microscopy. I. Mathematical modeling

Area of Science:

• Surface science
• Colloid and surface chemistry
• Nanotechnology

Background:

• Interfacial slip is crucial in fluid dynamics and nanotechnology.
• Colloid probe atomic force microscopy (AFM) is a key technique for measuring interfacial slip.
• Accurate quantification of hydrodynamic forces in AFM experiments is challenging due to various experimental factors.

Purpose of the Study:

• To develop a stable spreadsheet algorithm for calculating hydrodynamic forces in colloid probe AFM.
• To quantify the impact of experimental factors on slip hydrodynamic force and fitted slip length.
• To improve the reliability and accuracy of slip length measurements in AFM studies.

Main Methods:

• Development of a spreadsheet algorithm for hydrodynamic force calculation.
• Quantification of effects from nanoparticle contamination, cantilever bending, microsphere flattening, and large separation calibration.
• Application of the algorithm to fit new experimental data and a developed
• blind test
• protocol.

Main Results:

• Experimental factors significantly affect the fitted slip length, in the order of nanoparticle contamination, cantilever bending, microsphere flattening, and calibration.
• The new algorithm enables reproducible fitting of experimental data.
• A blind test protocol provides reliable estimates of fitting error for slip length (2 nm average systematic error) and spring constant (3% error).

Conclusions:

• The developed algorithm ensures reliable fitting of hydrodynamic theories to experimental data, yielding accurate slip length.
• The exact calculation of drag force may resolve discrepancies in previous reports regarding cantilever dependency of fitted slip length.
• This work enhances the precision and trustworthiness of interfacial slip measurements using AFM.