Liquid contact resonance AFM: analytical models, experiments, and limitations.

Area of Science:

• Surface science
• Scanning probe microscopy
• Nanomechanics

Background:

• Contact resonance Atomic Force Microscopy (CR-AFM) is a powerful technique for mapping surface topography and stiffness.
• Previous applications were limited to non-liquid environments due to analytical and experimental challenges like viscous damping and fluid loading.
• These challenges hindered the widespread use of CR-AFM in biologically relevant liquid media.

Purpose of the Study:

• To develop an analytical framework for CR-AFM in liquid.
• To demonstrate direct excitation of CR-AFM resonances using magnetic actuation.
• To enable quantitative stiffness imaging in liquid environments.

Main Methods:

• Development of a novel analytical approach to model contact resonances in liquid.
• Implementation of direct cantilever actuation via magnetic fields and particles.
• Utilizing soft cantilevers and low contact forces for imaging.

Main Results:

• Successfully adapted CR-AFM for operation in liquid environments.
• Demonstrated quantitative stiffness imaging across a range of surface stiffness values.
• Overcame limitations of viscous damping and fluid loading effects.

Conclusions:

• CR-AFM can now be effectively utilized in liquid for concurrent topography and stiffness mapping.
• The developed analytical approach and magnetic actuation method are key to this advancement.
• This opens new avenues for nanoscale mechanical characterization in fluidic systems.