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Atomic force microscopy colloid-probe measurements with explicit measurement of particle-solid separation.
Spencer C Clark1, John Y Walz, William A Ducker
1Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, USA.
Langmuir : the ACS Journal of Surfaces and Colloids
|August 25, 2004
Summary
Evanescent wave atomic force microscopy (EW-AFM) directly measures particle-surface separation using scattered light intensity. This novel technique enhances surface force measurements and enables new experimental possibilities, like force monitoring at constant separation.
Area of Science:
- Surface science
- Nanotechnology
- Optical physics
Background:
- Atomic force microscopy (AFM) conventionally infers particle-surface separation from surface forces.
- Existing methods like Total Internal Reflection Microscopy (TIRM) have limitations in particle control.
Purpose of the Study:
- To introduce Evanescent Wave Atomic Force Microscopy (EW-AFM) for direct particle-surface separation measurement.
- To demonstrate EW-AFM's advantages over conventional AFM and TIRM.
Main Methods:
- Utilizing evanescent wave scattering generated by total internal reflection at a solid/fluid interface.
- Measuring the intensity of back-scattered light collected from an AFM cantilever-attached particle.
- Adapting TIRM principles by collecting back-scattered light due to AFM obstruction of forward scatter.
Main Results:
- EW-AFM provides direct, unambiguous measurement of separation between a surface and an AFM-bound particle.
- This method removes ambiguity in surface force measurements.
- Enables new measurement modes, such as force monitoring at a constant separation.
Conclusions:
- EW-AFM offers enhanced control over particle position compared to TIRM.
- The technique provides more precise surface force measurements and opens avenues for novel experiments.