What does AFM do?

Atomic force microscopy is a powerful surface analytical technique used in air, liquid or vacuum to generate very high-resolution topographic images of a surface down to molecular/atomic resolution. Depending on the sharpness of the tip it gives spatial resolutions of 1-20 nm. It can record topographic images as well as providing some information on nanoscale chemical, mechanical (modulus, stiffness, viscoelastic, frictional), electrical and magnetic properties.

How does AFM work?

In AFM, a sharp microfabricated tip attached to a cantilever is scanned across a sample. The deflection of this cantilever, caused by the forces developed between the tip and the sample, is monitored using a laser and photodiode and is used to generate an image of the surface.

The AFM can image in a number of ways using either contact mode or an oscillating technique where the tip taps the surface.

The AFM can also be used for force spectroscopy. Here it applies forces as a function of height from 5pN to 50 µN to one spot on a surface to analyse mechanical or in some cases chemical properties at surfaces. It either pushes into the surface to measure nanomechanical properties of a surface such as modulus, stiffness and adhesion or pulls away from the surface to investigate bond rupture and molecular pulling.

What is AFM used for?

• Inorganics, polymers, coatings and bio-samples
• Personal care products - measuring the change in nanoscale mechanical properties (modulus and friction) of hair, teeth and skin
• Investigating the force required to remove nanoparticles from a surface
• The topography and nanomechanical properties of coatings

What are the measurement challenges?

• Calibration, quantification and understanding of AFM modes (including force spectroscopy, multi-frequency modes, frequency modulation mode, lateral force and amplitude modulation mode)
• Obtaining valid additional information from AFM (mechanical, chemical, electrical)
• Imaging soft samples at high resolution whilst minimising damage.

See our AFM research page to find out more.