Analysis of Roger Leir's SampleDigital Instruments
Optical images: Optical microscopy was used to look at the sample in the serum, in pure water and in air. No difference was detected when the sample was in the serum or in water. We could clearly see that the sample is constituted with a hard core enveloped in a soft envelope (or "membrane") (IMAGE 1, IMAGE 2). The membrane had a white/yellow color. It could be cut with a scalpel. When we removed a piece of this membrane and let it dry in air, some of it (corresponding to a white fibrous area, image 3) would cast very fast and turn into a hard material, looking like a resin (image 4). Other part of the "membrane" would stay soft in air (image 5). We also noticed at the surface of the envelope some "bubbles" of about 0.5 mm in diameter (IMAGE 7). These bubbles looked like oil drops or frog eggs! These bubbles were attached to each other. By touching the envelope with the scalpel (IMAGE 8) some of the bubbles could be detached and could be seen floating in the serum (image 10). Atomic force microscopy (AFM) images of the membrane: We tried to look at the sample under water. We used the tapping mode technique and the contact mode technique as well. In these conditions, the sample was very difficult to image (image 11). We think that the sample is too soft in water and the AFM probe cannot track the sample surface in an adequate way. Although image 11 shows some stripes at the sample surface, it is difficult to conclude that these structures correspond exactly to the real topography surface. We have been able to make a section of the external part of the sample (the "membrane") using a diamond microtome blade. The sectioning procedure may leave artifacts as described in the text below. The section was first observed by optical microscopy with polarized light (IMAGE 12), and we could see some viscous liquid leaking out from certain areas on the sample. This liquid had the same appearance as oil. We have scanned the section with an AFM in air, in tapping mode. The topography images (IMAGE 14 through 19) show an irregular surface with prominent features (from about 6 nm up to about 250 nm in height) of very different sizes (50 nm up to 500 nm), and crevasses, about 180 nm in depth (images 20, 20'and 21). The image 14 shows some very flat areas as imaged, which could correspond to the areas where the viscous liquid is rising from the surface. Image 15 is a tapping mode and phase image in which some organized structure is evident. The rows running from upper-right to lower-left could be due to the microtome cutting direction. However, the sample appears to present some circular features of regular size and spacing. Image 19 is comprised of magnified data from the upper left corner of image 15 where the structure is most evident. Image 19 is displayed in a blue color table to emphasize the contrast. Also visible in Image 15 is a layered structure, which appears on the left of the image. The layers seem to curve around a crevasse. The phase mode image data (the right image in most scans) can provide information about micro mechanical properties of the sample surface (adhesion, hardness, and elasticity...) and detect different components in a material. The phase images show that the sample is constituted of a non-uniform material, i.e. presumably with multiple components (at least 2) (images 14 to 18). These components seem to have different mechanical properties. These components are not uniformly regular, as would be the case in uniform tissues. Conclusions on the membrane AFM data:
AFM Data on the hard sample core: The surface of the core piece is very rough and therefore difficult to image. Polishing with diamond paper created a small flat in order to permit imaging of the magnetic properties. The polishing process confirmed the hardness and the crystalline or poly crystalline structure of the core. Since there are many magnetic materials we can not tell the chemical composition of the core. We can define that the core is covered with a resin-like casing and that the inner portion is harder and polishes like a crystal or metal. Further tests other than AFM may be possible to determine conclusively the material and composition. Using an AFM tip coated with magnetic material (Cobalt/Chromium) it is possible to measure magnetic domain structures by measuring the phase or frequency shift of an oscillating cantilever in response to changes in the magnetic polarization while scanning the surface. The last IMAGE 22 in the series is such an image. The magnetic force image shows randomly distributed domains across a 10um area. The sample's hard inner core was found to be ferro-magnetic. It is randomly polarized with domains on a 50-100nm length scale. The height image shows the scratches due to the 1um diamond polishing paper. The right phase image is the phase response of the oscillating cantilever over the sample due to the magnetic fields. The domains of up and down polarization are shown as bright and dark regions in the image. This data is consistent with a piece of ferromagnetic material that has not been magnetized. Signed, Andy Erickson & Irene Revenko |
April 6th, 2000
No distinct structured could be identified. The images show an irregular
surface with flat or rough areas as defined by the microtome cut and the
structure of the sample. The sample is made with multiple components of
varying hardness. When the tissue is cut, a viscous liquid like oil exudes
from the surface. Since no AFM studies have been previously performed on
animal tissue in these conditions (non-fixed tissue, in liquid), it is
impossible to compare this sample's structure.
