Microtome and Its Blades in Microscopy

Microtome

• A microtome is a device used to cut extremely thin slices of material, known as sections, which are important in science.
• Microtomes are used in microscopy to prepare samples for observation under transmitted light or electron radiation.
• The device uses steel, glass, or diamond blades, depending on the specimen being sliced and the desired thickness of the sections being cut.

Blades

• Steel blades are used to prepare 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

• 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.

History of Microtomy

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

Types of Microtomes

• Rocking microtome
• Rotary rocking microtome
• Sledge microtome
• Rotary microtome
• Cryomicrotome
• Ultramicrotome
• Vibrating microtome
• Saw microtome
• Laser microtome

Sledge Microtome

• Typical applications for this design of microtome 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.

Rotary Microtome

• 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.

Cryomicrotome

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

Ultramicrotome

• It allows the preparation of extremely thin sections.
• The typical thickness of these cuts is between 40 and 100 nm for transmission electron microscopy.
• Diamond knives (preferably) and glass knives are used with ultramicrotomes.

Vibrating Microtome

• The vibrating microtome 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.
• The vibrating microtome is usually used for difficult biological samples.
• The cut thickness is usually around 30–500 μm for live tissue and 10–500 μm for fixed tissue.

Saw Microtome

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

Laser Microtome

• Contact-free slicing is possible with a laser microtome.
• Prior preparation of the sample is not required.
• It can also be used for very hard materials, such as bones or teeth, as well as some ceramics.
• Thickness: 10-100 μm.