Microtome Machine Basics: Components, Uses, and Operating Principles

There is no laboratory involved in histo- or pathology research that could operate effectively without a microtome machine. A reliable and precise cutting device, a microtome machine, converts biological samples into sections of appropriate thickness for subsequent microscopic analysis. Whether a sample is made of paraffin, frozen material, or metal, there is always a perfect microtome machine designed to deal with such samples.

A basic understanding of the operation principles of a microtome machine is necessary both for selecting the optimal device and achieving desirable results. This article explains what a microtome machine is, what functions it serves, what key elements it consists of, and what microtome machine features are important to consider when purchasing.

Definition of a Microtome Machine

A microtome machine is a high-precision apparatus for making thin slices (sections) from a sample, ranging from one to sixty micrometers thick. A microtome machine produces slices that allow studying the composition of materials using an electron or optical microscope.

Therefore, the key qualities a good microtome machine must possess are precision (i.e., the ability to make uniformly thin slices) and stability (i.e., resistance to deviations in cutting). The use of the latest innovations is another essential characteristic of a modern microtome machine.

Laboratories engaged in histo-pathology studies cannot manage without this sophisticated cutting device, which can perform its tasks with high efficiency and precision for several decades.

Key Parts of a Microtome Machine

Each microtome machine is composed of similar parts. Knowing the function performed by a certain component will help users maintain their machines properly, thus prolonging their operational life significantly.

The Specimen Holder (Chuck)

A specimen holder is the element that securely holds the sample during the process of cutting. The majority of histology laboratories use microtome machines intended for working with paraffin tissue samples. The orientation of the specimen holder defines the cutting plane and the angle of slicing the sample.

Blade and Blade Holder

Blades are the key parts of any microtome machine, as they actually make the sections from a sample. Steel blades are used in the vast majority of histology labs. Depending on the specific application, the angle of the blade installation differs but normally varies between three and ten degrees. An improperly installed blade will make irregular sections.

Advance Mechanism

An advanced mechanism is responsible for moving the sample by the predefined distance. In a motorized machine, this mechanism is based on a stepper motor; in the rotary device, the advance is ensured by means of a micrometer screw. Irrespective of the type, this microtome machine part plays a crucial role: any deviation of the advance leads to irregular sections.

Handwheel and Drive System

In the case of rotary microtome machines, the drive system is a handwheel that moves the sample holder vertically during cutting. One full rotation of this wheel produces one slice from a sample. Motorized microtome machines substitute the handwheel for a drive motor.

Base and Cutting Stage

The cutting stage holds the blade assembly while the base provides the required stability. For the purpose of vibration reduction, the cutting surface is made of heavy cast-iron or steel. The cutting stage also accommodates a waste container that captures trimming pieces of the specimen.

Types of Microtome Machines and Their Features

Microtome machines are subdivided into a few types differing by the movement pattern of the knife and the sample.

Rotary Microtome Machine

The most common microtome machine type is a rotary microtome machine, where the sample moves vertically while the knife stays fixed. Rotary units are mainly used for making serial sections of paraffin-embedded biological tissues.

Sliding Microtome Machine

Another microtome machine variant involves the lateral motion of the knife across the stationary sample. Such units are preferred for making sections from hard samples, such as wood, tissue embedded in celloidin, etc.

Cryostat Microtome Machine

This microtome machine type involves placing the apparatus in a low-temperature chamber and carrying out rapid slicing of frozen samples. The temperature inside cryostats varies between minus twenty and minus thirty degrees Celsius.

Vibrating Microtome Machine

Vibrating microtomes, or simply vibratomes, provide an opportunity to make sections from unfixed samples by applying an oscillatory knife. Vibrating microtome machines are widely used in the sphere of neuroscience.

Ultramicrotome

An ultramicrotome is capable of producing ultra-thin sections of up to fifty nanometers. This microtome machine type applies diamond or glass knives.

Main Functions of a Microtome Machine

Microtome machines are versatile cutting devices that are successfully employed by numerous industries, including pharmaceutical research facilities, industrial companies, etc.

Histology and Pathology Laboratory

The largest single group of consumers of microtome machines is pathology labs, which routinely make numerous sections from tissue samples for further staining and examination. The accuracy of the result produced by a microtome machine has a direct impact on patients' health.

Biological Research Laboratory

The main objective of biological researchers, whether working in academic settings or in the industry (for example, drug manufacturing companies), is to develop new knowledge about various biological processes. Therefore, any microtome machine is a tool of vital importance for histo-biological research.

Industrial Laboratory

Aside from biological applications, a microtome machine is indispensable in analyzing the structure of industrial materials. Polymer samples, rubber, paper products, or even soft metals are sectioned by using this tool.

The key to getting good results is knowing the operating principles of the apparatus.

Sample Preparation and Embedding

Before starting the cutting procedure, it is vital to prepare the sample and embed it into a suitable medium. Paraffin is used for embedding the soft biological samples, whereas hard or delicate ones are placed in resin or frozen media.

Section Thickness Control

The operator specifies the required thickness of sections with the help of the advanced mechanism. Typically, sections from paraffin tissue blocks range in thickness from three to five micrometers; special types of staining may involve six to eight micrometers.

Blade Angle and Cutting Process

To make even sections, it is vital to install the blade at the correct angle. Otherwise, it would result in either compressed sections or the inability of the knife to touch the sample surface, thus creating an even section. The blade angle is adjusted with the help of a microtome machine blade holder.

Ribbons and Section Transfer

If all the parameters are adjusted appropriately, it results in the formation of ribbons, consisting of multiple sections. They are then carefully transferred to a water bath using a brush and finally mounted on slides for examination under a microscope.

How to Maintain a Microtome Machine

Proper maintenance of a microtome machine ensures prolonged life and a high performance level.

Blades

Keeping blades razor-sharp is extremely important when it comes to producing quality sections. Disposable blades should be changed regularly; reusable blades require regular cleaning and should be stored in special boxes.

Calibration and Adjustment

Microtome machines are calibrated from time to time to ensure their performance quality, especially when it comes to the accuracy of cutting. Technicians should verify the thickness, adjusting the advance system accordingly; blade angle setting is subject to periodic adjustment, too.

Cleaning

Regular cleaning of the working surfaces, especially after each working shift, is vital in preventing the accumulation of paraffin shavings on a microtome machine.

Buying a Microtome Machine

Choosing the optimal microtome machine requires considering multiple aspects, such as the budget, expected workload, and the particular type of biological material used. There is an extensive array of used, certified, and refurbished microtome machines sold online nowadays, and buying one of them is a much cheaper option than acquiring a new apparatus.

In this regard, Machinery Masters will assist you in buying the best microtome machine for your needs.