Use of atomic force microscope to measure friction in silicon nitride granules

2003 ◽  
Vol 58 (5) ◽  
pp. 35
Author(s):  
Jean-Paul Revel

The last few years have been marked by a series of remarkable developments in microscopy. Perhaps the most amazing of these is the growth of microscopies which use devices where the place of the lens has been taken by probes, which record information about the sample and display it in a spatial from the point of view of the context. From the point of view of the biologist one of the most promising of these microscopies without lenses is the scanned force microscope, aka atomic force microscope.This instrument was invented by Binnig, Quate and Gerber and is a close relative of the scanning tunneling microscope. Today's AFMs consist of a cantilever which bears a sharp point at its end. Often this is a silicon nitride pyramid, but there are many variations, the object of which is to make the tip sharper. A laser beam is directed at the back of the cantilever and is reflected into a split, or quadrant photodiode.


2006 ◽  
Vol 512 ◽  
pp. 395-398
Author(s):  
Nobumitsu Hirai ◽  
Tatsuya Tooyama ◽  
Toshihiro Tanaka

Potential dependence of the friction force between an atomically-flat terrace of Au(100) single crystal and a tip attached to a silicon nitride cantilever of electrochemical atomic force microscope (EC-AFM) have been investigated qualitatively in 0.05 M H2SO4 aqueous solution. It is found that the friction force gains when the potential increases in the potential range between −400 mV and 400 mV vs Hg/Hg2SO4 electrode.


2000 ◽  
Vol 8 (9) ◽  
pp. 3-7
Author(s):  
Stephen W. Carmichael ◽  
Julio M. Fernandez

The atomic force microscope (AFM) is well known for its outstanding spatial resolution, but it is becoming increasingly useful as the instrument for force spectroscopy. In the force spectroscopy mode, the AFM can measure tiny tension forces, in the piconewton (pN) range. Daniel Müller, Wolfgang Baurmeister, and Andreas Engel have used the AFM in both the imaging and force spectroscopy modes to pull proteins out of membranes in a controlled fashion.Müller et al. used Deinococcus radiodurans, a bacterium best known for its high resistance to radiation (as its Genus name implies), as their test subject. They extracted a highly regular membrane from the bacterium, the hexagonally packed intermediate (HPl) layer. They mounted the HPI on mica, so that the hydrophilic outer surface of the HPI adsorbed strongly to the mica, exposing the hydrophobic inner surface to the silicon nitride AFM stylus.


2001 ◽  
Vol 89 (4) ◽  
pp. 2465-2472 ◽  
Author(s):  
F. S.-S. Chien ◽  
Y. C. Chou ◽  
T. T. Chen ◽  
W.-F. Hsieh ◽  
T.-S. Chao ◽  
...  

Author(s):  
Kathleen M. Marr ◽  
Mary K. Lyon

Photosystem II (PSII) is different from all other reaction centers in that it splits water to evolve oxygen and hydrogen ions. This unique ability to evolve oxygen is partly due to three oxygen evolving polypeptides (OEPs) associated with the PSII complex. Freeze etching on grana derived insideout membranes revealed that the OEPs contribute to the observed tetrameric nature of the PSIl particle; when the OEPs are removed, a distinct dimer emerges. Thus, the surface of the PSII complex changes dramatically upon removal of these polypeptides. The atomic force microscope (AFM) is ideal for examining surface topography. The instrument provides a topographical view of individual PSII complexes, giving relatively high resolution three-dimensional information without image averaging techniques. In addition, the use of a fluid cell allows a biologically active sample to be maintained under fully hydrated and physiologically buffered conditions. The OEPs associated with PSII may be sequentially removed, thereby changing the surface of the complex by one polypeptide at a time.


Author(s):  
S.A.C. Gould ◽  
B. Drake ◽  
C.B. Prater ◽  
A.L. Weisenhorn ◽  
S.M. Lindsay ◽  
...  

The atomic force microscope (AFM) is an instrument that can be used to image many samples of interest in biology and medicine. Images of polymerized amino acids, polyalanine and polyphenylalanine demonstrate the potential of the AFM for revealing the structure of molecules. Images of the protein fibrinogen which agree with TEM images demonstrate that the AFM can provide topographical data on larger molecules. Finally, images of DNA suggest the AFM may soon provide an easier and faster technique for DNA sequencing.The AFM consists of a microfabricated SiO2 triangular shaped cantilever with a diamond tip affixed at the elbow to act as a probe. The sample is mounted on a electronically driven piezoelectric crystal. It is then placed in contact with the tip and scanned. The topography of the surface causes minute deflections in the 100 μm long cantilever which are detected using an optical lever.


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