A microtome is a device used to slice samples (either organic or inorganic) into extremely thin strips called "sections", which are then mounted on slides and examined with a microscope. Microtomes are most commonly used in clinical and research labs. Clinical lab staff use them to section patient samples for biopsies and other diagnostic procedures, while researchers use them to section samples from lab rats, plants, and other organisms for analysis.
There are numerous different types of microtomes, each designed to address unique requirements. Here's a rundown of some of those variations.
By far the most common type, rotary microtomes are used to section paraffin-embedded tissue samples within the range of 0.5µm to 60µm. These machines are quite simple, consisting of just a weighted handwheel, sample chuck, and blade assembly. Microtomy is performed by spinning the handwheel clockwise; with each revolution the sample advances to the blade, has a layer sectioned, and retracts on the upward stroke to prevent it from rubbing against the side of the blade and being damaged.
Many rotary microtomes feature motorized sectioning and foot pedals, which allow the user to simply step on a pedal to initiate automatic sectioning. This saves the user effort and ensures consistent sections.
Want to learn more about rotary microtomes? Here's a video explaining some of their common features.
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Sliding microtomes are one of the most versatile types. While they're often used to section the same type of samples as rotary microtomes, they can also be used to section hard materials like wood with the proper blade. Additionally, sliding microtomes vary greatly in size — many are about the same size as a rotary microtome, but in industrial environments, they can be large enough to section things a few feet wide. Sections are typically between 1µm and 60µm.
As the name implies, the blade of a sliding microtome is mounted on a slide. It moves down the slide to the fixed sample holder, sectioning off a layer with each pass. This simple design lends itself to longevity and ease of maintenance.
It's important to note that some manufacturers use the phrase "sliding" and "sledge" interchangeably.
Saw microtomes are suited for sectioning hard, brittle samples like bone, teeth, and wood. As such, they're used in biological and environmental research labs, as well as in forensic procedures.
With saw microtomes, samples are mounted against a spinning blade recessed within the unit. Some have diamond blades to ensure clean sections for even the hardest samples. As the blade spins, a low-pressure water jet continuously pours water on the edge of the blade to prevent it from overheating.
Saw microtomes produce the thickest sections of any microtome, as they're not designed to slice thinner than 30µm.
Here's a video from Simon Fraser University that shows the entire microtomy process with a Leica SP1600 saw microtome.
Vibrating microtomes are specialized for sectioning soft, fresh samples that aren't embedded in wax so their cell morphology is kept intact. Examples would be brain, nerve, and spinal cord tissue. The vibration allows for the sample to be sectioned with less pressure than it would otherwise require, thus minimizing the chances of fracture.
According to Engineering360, fresh samples sectioned with vibrating microtomes are typically over 30µm thick. Fixed samples are over 10µm thick.
Laser microtomes are the only microtomes that offer non-contact microtomy, which is vital for applications that demand the sample's cell morphology remain unaltered. Additionally, laser microtomy doesn't require any sample prep beforehand; samples can be cut "in their native state". This saves labs precious time and resources.
Because they don't use razor blades, laser microtomes can slice virtually any type of sample from bone to soft tissue.Browse Our Selection of Microtomes
Ultramicrotomes were designed to produce sections for transmission electron microscopy (TEM). In order for TEM to work, sections must be slimmer than 150nm — much thinner than the 30µm sections produced by most other microtomes!
Interested in learning more? Here's a video demonstrating an ultramicrotome.
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