Microtome: Laboratory Instrument

Study Notes

A microtome is a device used to cut extremely thin slices of material, known as sections, which is important in science.
Microtomes are used in microscopy, allowing for the preparation of samples for observation under transmitted light or electron radiation.

Microtomes use steel, glass, or diamond blades, depending on the specimen being sliced and the desired thickness of the sections being cut.
Steel blades are used for preparing sections of animal or plant tissues for light microscopy histology.
Glass knives are used to slice sections for light microscopy and to slice very thin sections for electron microscopy.
Diamond knives are used to slice hard materials such as bone, teeth, and plant matter for both light microscopy and electron microscopy.

Microtomy is used to prepare thin sections for materials such as bones, minerals, and teeth.
Microtome sections can be made thin enough to section a human hair across its breadth, with section thickness between 50 nm and 100 μm.

The earliest form of microtomy was the freehand sectioning of fresh or fixed material using a sharp razor.
With practice, the section produced could be quite thin and translucent.

Typical applications are for the preparation of large samples, such as those embedded in paraffin for biological preparations.
Typical cut thickness achievable on a sledge microtome is between 1 and 60 μm.

Typical cut thickness for a rotary microtome is between 1 and 60 μm.
For hard materials, such as a sample embedded in a synthetic resin, this design of microtome can allow good "semi-thin" sections with a thickness of as low as 0.5 μm.

For the cutting of frozen samples, many rotary microtomes can be adapted to cut in a liquid-nitrogen chamber, in a so-called cryomicrotome setup.
The reduced temperature allows the hardness of the sample to be increased, which allows the preparation of semi-thin samples.

Allows the preparation of extremely thin sections.
Typical thickness of these cuts is between 40 and 100 nm for transmission electron microscopy.
Diamond knives and glass knives are used with ultramicrotomes.
Sections are floated on top of a liquid as they are cut and are carefully picked up onto grids suitable for TEM specimen viewing.

Operates by cutting using a vibrating blade, allowing the resultant cut to be made with less pressure than would be required for a stationary blade.
Usually used for difficult biological samples.
Cut thickness is usually around 30–500 μm for live tissue and 10–500 μm for fixed tissue.

Especially for hard materials such as teeth or bones.
The microtome of this type has a recessed rotating saw, which slices through the sample.
Minimal cut thickness is approximately 30 μm and can be made for comparatively large samples.

Contact-free slicing.
Prior preparation of sample not required.
Can also be used for very hard materials, such as bones or teeth, as well as some ceramics.
Thickness: 10-100 μm.