Capabilities
There is a wide range of experiments that can be done by Atomic Force Microscopy (AFM). Below is a very brief look at the AFM instruments available along with the capabilities of those instruments:
Topography
One of the best features of the AFM is the ability to map nanoscale topographical features. Unlike some other microscopes, the AFM can be operated in air, liquid and at a range of temperatures.
High resolution imaging
Tapping mode image of diphenylalanine peptide nanofiber on mica, courtesy of R Creasey
Using an extremely sharp tip, the AFM can map surfaces at extremely high resolution, even down to individual molecules. These experiments require specific sample preparation and a lot of time to optimise parameters for imaging.
Liquid and humid environments
The AFM can be operated in a range of environments, although it is most commonly used in ambient conditions. Imaging in aqueous environments such as physiological buffer is easily achieved on most systems, while some systems are contained within chambers for achieving controlled humity.
Temperature control
A stage heater can be used for in-situ heating experiments on multiple systems. The system contained within a chamber can be used for very precise temperature control.
High-speed imaging & large data sets
Using an automated stage movements and ScanAsyst imaging, vast numbers of images can be collected without intensive labour input. In this way the AFM can become high-throughput for many samples or across a large area.
Properties
In addition to the excellent imaging capabilities here at the MTF division, many other surface properties can be investigated by AFM. All of these properties can be measured under a range of environments, similar to the imaging capabilities.
Chemical/mechanical properties
Graph of 2 force-distance curves, showing the deflection versus the displacement of the cantilever, courtesy of R Creasey
(A) As the tip approaches a surface, long-range forces cause deflection of the cantilever, giving rise to information about the electrostatic and solvation properties affecting the material.
(B) Then, after contact is made, the nanoscale stiffness of the surface can be determined by fitting a model to the indentation portion of a force-distance curve. A wide range of materials have been investigated this way, from soft hydrogels (~1 MPa) to peptide nanotubes (~20 GPa).
(A), (C) Finally, as the tip is retracted from the surface, the force of adhesion between tip and sample can be measured directly. In the top curve shown above, there is no adhesion between the tip and the sample. As the tip material can be altered or functionalised, this adhesion can give rise to specific chemical information about the surface. For example in the bottom curve, an antibody has been covalently attached to the probe via a PEG linker and a specific protein interaction gives rise to the adhesion event (C).
In addition to collecting these properties at specific locations, the AFM can be programmed to collect force-distance curves across a defined area' this allows for mapping of properties (force-volume imaging).
Conductive/magnetic properties
The conductivity and local electronic properties of a surface can be investigated by using a conductive probe. Nanoscale I-V curves may reveal the density of states for individual molecules, or the conductivity of a sample can be mapped while imaging the topography. Similarly, a magnetized probe can be used for mapping the magnetic properties of a surface.
Nano- and micro-thermal analyses
The AFM probe can be heated in order to affect a highly localised area at the surface. By measuring the cantilever deflection, the thermal transition properties can be determined similarly to a DSC. Alternatively, the heated probe can be used to perform thermal lithography. In addition, a specialised thermometer-probe can be used to map the temperature of a surface at the micron level.]
ScanAsyst/PeakForce Quantitative Nanomechanical Mapping (QNM)
The PeakForce tapping mode of ScanAsyst™ provides a direct force control with minimum peak force down to less than 100pN, a level never achieved by previous AFM modes. Together with an automatic and dynamic parameter adjustment, SPMs have made high-resolution imaging of delicate samples in both air and liquid environments achievable without a deep understanding of AFM technology.
Furthermore, simultaneous high-resolution and well-defined force mapping can be obtained by PeakForce™ QNM™
Viscoelastic mapping
The Loss Tangent imaging mode of the MFP3D allows qualitative mapping of viscoelastic properties of a surface without any cantilever calibration
Back to our Expertise and Equipment