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Atomic force microscopy (AFM) for food analysis

Identification

Key words Atomic force microscopy (AFM), MFP 3D, microscopical technique, nanoscale imaging, surface imaging, topography, surface potential imaging, adhesion forces, force distance curves, force spectroscopy, lithography, scanning probe microscopy
Latest version 2012/07/17
Completed by DIL

How does it work?

Primary objective Analytical tool for determining surface properties (like topography and adhesion forces), surface potential imaging, force spectroscopy, lithography and/or phase imaging
Working principle Atomic force microscopy (AFM) is a technique based on the measurement of interactions between a sharp tip and the surface being characterized [1]. The tip is moved across the surface from certain distances, or directly in contact with it, depending on what surface properties that are being determined. The surface remains intact and will not be damaged.


Atomic force.jpg

The surface is scanned with a mechanical probe called cantilever. The cantilever’s deflection is detected by a focused and reflected light beam which hits a photodiode acting as a position sensitive detector (PSD). This signal is transferred to a computer and converted into a height image. Piezoelectric elements facilitate tiny but accurate and precise movements for scanning, which results in topographic images in the range of up to a few tenths of a nanometer.

Images
Additional effects Besides visualizing surface topography (2D and 3D) and in contrast to other microscopically techniques, AFM offers the opportunity of measurements concerning surface polarity or adhesion forces of a surface [2,3]. Furthermore, molecular size, firmness as well as intermolecular interactions of polysaccharides for gelation, swelling or stabilization can be determined in special scanning modes [4,5].
Important process parameters force spectroscopy, lithography, phase imaging
Important product parameters Surface topography, adhesions forces, surface potential imaging

What can it be used for?

Products Surfaces of solid parts and solid parts in liquids; solid-liquid, liquid-liquid or solid-gaseous interfaces e.g. example starch granules, ice crystals in ethanol, oil droplets in water (emulsions), bacteria and spores.
Operations Surface imaging

Nanoscale-imaging

Solutions for short comings Analysis of microscopical food structure at the nanometer scale before, after and during food processing to improve e.g. textural properties or to get information on surface topography

What can it NOT be used for?

Products Gases
Operations Measurement temperatures below -50°C and higher than 130°C are not possible, because of the limitation of the system.
Other limitations In some cases high temperatures in the sample holder, electric discharges by laboratory staff can damage very sharp and small expensive tip during preparation for measurements
Risks or hazards Eventual use of harmful solvents

Implementation

Maturity This method is commercially available and already used in research as an analytical tool, also in food research [6].
Modularity /Implementation Off line analytical method
Consumer aspects Not applicable
Legal aspects No legislation available
Environmental aspects In some cases, harmful solvents can be used

Further Information

Institutes DIL, IFR, INRA, Unilever
Companies Agilent Technologies, JPK Instruments
References 1. Binnig, G.; Quate, C.F.; Gerber, Ch. (1986), Atomic Force Microscope Physical Review Letters (56) 930-933

2. Eaton, P.; West, P., Atomic Force Microscopy, Oxford University Press, Oxford 2010 3. Berger, R.; Butt, H.-J.; Retschke, M. B.; Weber, S. A.L. (2009), Electrical Modes in Scanning Probe Microscopy, Macromolecular Rapid Communications 30 (14) 1167-1178. 4. Liu, P.; Chen, L.; Corrigan, P.A.; Yu, L.; Liu, Z. (2008), Application of Atomic Force Microscopy on Studying Micro- and Nano-Structures of Starch, International Journal of Food Engineering 4 (7) 5. Shimoni, E. (2008), Using AFM to explore food nanostructure, Current Opinion in Colloid and Interface Science 13 368-374. 6. Yang, H.; Wang, Y.; Lai, S.; An, H.; Li; Y.; Chen, ; Y.; Chen, ; Chen, F. (2007), Application of Atomic Force Microscopy as a Nanotechnology Tool in Food Science, Journal of Food Science 72 (4) R65-R75.

force spectroscopy, lithography, phase imaging Surface topography, adhesions forces, surface potential imaging Analytical instruments 2.1.1 physical other nanotechnology Science direct, PubMed, Wiley Search terms: AFM, atomic force microscopy, starch, food, surface imaging WikiSysop :Template:Review document :Template:Review status



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Created by Claudia Siemer on 17 July 2012, at 13:36