Machining Complex Three-Dimensional Nanostructures With an Atomic Force Microscope Through the Frequency Control of the Tip Reciprocating Motions

Author(s):  
Yanquan Geng ◽  
Yongda Yan ◽  
Emmanuel Brousseau ◽  
Xing Cui ◽  
Bowen Yu ◽  
...  

A novel method relying on atomic force microscope (AFM) tip based nanomachining is presented to enable the fabrication of microchannels that exhibit complex three-dimensional (3D) nanoscale floor surface geometries. To achieve this, reciprocating lateral displacements of the tip of an AFM probe are generated, while a high-precision stage is also actuated to move in a direction perpendicular to such tip motions. The width and length of microchannels machined in this way are determined by the amplitude of the tip motion and the stage displacement, respectively. Thus, the processing feed can be changed during the process as it is defined by the combined control of the frequency of the tip reciprocating motions and the stage speed. By employing the built-in force feedback loop of conventional AFM systems during such operations, the variation of the feed leads to different machined depths. Thus, this results in the capability to generate complex 3D nanostructures, even for a given normal load, which is set by the AFM user prior to the start of the process. In this paper, the fabrication of different microchannels with floor surfaces following half triangular, triangular, sinusoidal, and top-hat waveforms is demonstrated. It is anticipated that this method could be employed to fabricate complex nanostructures more readily compared to traditional vacuum-based lithography processes.

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.


2007 ◽  
Vol 121-123 ◽  
pp. 739-742 ◽  
Author(s):  
H.M. Chi ◽  
Z.D. Xiao ◽  
Xin Xing Xiao

Weng`an fauna in Guizhou, China provides a unique window for the evolution of the early life especially since the animal embryos and sponge is found there. Phosphatization makes the fossils preserve in details including cells and subcellular structure. Here we use atomic force microscope observing the surface of some three dimensional preserved embryo fossils and the ultra membrane-like structure is found under atomic force microscope (AFM) while such structure can`t be found under scanning electron microscope (SEM). The membrane-like structure is approximately 10nm in thickness which maybe one part of the fossil embryos or belong to another nano scale microfossils. Therefore, AFM provides a new method for the study of the ultra structure of the microfossils from Weng`an fauna.


1994 ◽  
Vol 332 ◽  
Author(s):  
R. Giles ◽  
S. Manne ◽  
C.M. Zaremba ◽  
A. Belcher ◽  
S. Mann ◽  
...  

ABSTRACTAfter describing some recent developments in atomic force microscopy (AFM), a specific application to the study of shell ultrastructure is examined in detail. By embedding bleached nacreous tablets in epoxy and imaging them with the atomic force microscope (AFM) during in situ dissolution, it was possible to visualize the topography of both the top faces of the tablets and the impressions in epoxy made by the bottom faces of the tablets. This epoxy imprint reproduced tablet features down to the 10 nm scale. Using this technique it should be possible to measure correspondence between topographic features on the proximal and distal faces of tablets, which is necessary to form a three-dimensional picture of the nacreous region. In addition to these dissolution experiments, growth experiments (in modified sea water) on bleached, embedded tablets indicated that aragonite grows on a tablet as asperities oriented along the c axis, normal to the tablet surface. No change was seen on the surface of the epoxy, which confirmed that the crystals were growing on the tablet surface, not spontaneously nucleating out of solution.


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