ultra microtome


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ULTRAMICROTOME Submitted by M.Sakthivel(Bsa-09-841)

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ULTRA MICROTOME Ultra microtome is a mechanical instrument used for cutting biological specimens into transparent thin films for microscopic examinations. They may be steel, glass or diamond blades depending upon the required thickness to be cut. Steel blades are used for animal and plant samples, whereas diamond is used for hard substances.




HISTORY One of the first devices for the preparation of such cuts was invented in 1770 by George Adams, Jr. (1750–1795) and further developed by Alexander Cummings. The device was hand operated, and the sample held in a cylinder and sections created from the top of the sample using a hand crank microtome drawn by Cummings in 1770

Types of microtome:

Types of microtome Sled microtome Rotary microtome Cryomicrotome Ultramicrotome Vibrating microtome Saw microtome Laser microtome

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Type of Microtome Type of Sample Sample Cut Thickness Application Saw microtome Hard and brittle material > 30µm. Samples such as bone and teeth Sled microtome Embedded samples 1 – 60µm Samples sliced at an angle Rotary microtome Embedded samples 0.5 µm - 60 µm Thin samples. Manual control Vibrating microtome Difficult/soft, Fresh/fixed samples Fixed >10 µm Fresh > 30 µm Less pressure and sample disruption Laser microtome All samples >1 µm No sample contact and no sample prep Cryomicrotomes Frozen samples Very specific thickness Ultramicrotomes TEM 40-100nm SBFSEM 30-50nm Extremely thin cuts for analysis with specialty microscopes

Sectioning :

Sectioning Prior to cutting by microtomy , biological materials are usually placed in a more rigid fixative, in a process known as embedding . This is achieved by the inflow of a liquid substance around the sample, such as paraffin (wax) or epoxy , which is placed in a mould and later hardened to produce a "block" which is readily cut.


Contd…. The declination is the angle of contact between the sample vertical and knife blade. If the knife blade is at right angles (declination=90) the cut is made directly using a pressure based mode, and the forces are therefore proportionally larger. If the angle is too large, the sample can crumple and the knife can induce periodic thickness variations in the cut. By further increasing the angle such that it is too large one can damage the knife blade itself.



Diamond Knives for Ultramicrotomy :

Diamond Knives for Ultramicrotomy Features: Edge Radius - 2nm 45° C utting angle 35° and 55° angles optional Clearance angle - 0° Virtually unlimited resharpening



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New Diamond Knives Exchange or Resharpen Catalog Number Edge Length Price Catalog Number Edge Length Price 22500 1.5mm $1,625.00 22500E 1.5mm $995.00 22505 2.0mm $1,950.00 22505E 2.0mm $1,195.00 22510 2.5mm $2,190.00 22510E 2.5mm $1,375.00 22515 2.8mm $2,375.00 22515E 2.8mm $1,425.00 22520 3.0mm $2,415.00 22520E 3.0mm $1,475.00 22525 3.5mm $2,670.00 22525E 3.5mm $1,620.00 22530 4.0mm $2,900.00 22530E 4.0mm $1,700.00 22532 4.5mm $3,050.00 22532E 4.5mm $1,820.00 22534 5.0mm $3,330.00 22534E 5.0mm $1,885.00 22536 5.5mm $3,550.00 22536E 5.5mm $1,995.00 22570 5.6mm $3,595.00 22570E 5.6mm $2,025.00 22571 5.8mm $3,750.00 22571E 5.8mm $2,140.00 22572 6.0mm $3,775.00 22572E 6.0mm $2,195.00 22573 6.5mm $3,995.00 22573E 6.5mm $2,250.00 22574 7.0mm $4,250.00 22574E 7.0mm $2,475.00


Procedure It consists in a support carrying the knife and a sample holder installed on a vibration proof platform. Both knife and sample have adjustable orientations. The knife is cut from glass or diamond with a 35-45° angle. The sample is mounted on a vertically moving arm moving regularly against the knife edge. The device is equipped with a micro- to nanometer scale movement system controlling object position. All operations are controlled under the binocular

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The Leica Ultracut UCT ultramicrotome with a cryo-attachment is designed to meet the precise requirements of sample preparation for electron microscopy.


RECENT DEVELOPMENT The recent development is the use of laser microtome .It has the capacity to cut in few seconds. No sample preparation is required . Slice thickness is 10-100nm .

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Variants Using a vibrating knife improves the results when dealing with soft materials. Risks Cutting risks when handling knives and razor blades .

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Applications : 1.Traditional histology 2.Cryo section 3.Electron microscopy 4.Botanical microtomy

Advantages :

Advantages This is the only technique yielding directly 30 nm sections of constant thickness. It can be applied to a precise zone of the sample, selected with the optical microscope. Observing the slide successively using optical and electron microscopes enables to follow the same selected area over the whole magnification range. All sample orientations can be chosen.

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The preparation is relatively fast for a trained operator. It consists in successive sections of the same specimen and provides large observation areas. It gives access to structural and chemical information within a volume (access to 3-D reconstruction) and can be exploited for statistical purposes.


Drawbacks This technique may introduce compressions in the material, tearing off of the hardest zones and tears along two zones differing in hardness. Metal samples may suffer strain hardening. It cannot be applied to very heterogeneous, very hard, very soft and very fragile samples.

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Conclusion This technique is the best choice for biological materials and polymers, whether in bulk or in fine particle form. Ultra thin sections of constant thickness (30-50 nm) may be directly obtained, without the drawback. Compared to tripod polishing and to ion beam thinning, it has the distinctive advantage of providing wide observation zones (up to the millimeter) while maintaining a constant thickness.



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