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Detailed Explanation Of Centrifuge Fixed-Angle Rotor and Swing-Bucket Rotor

   |  May 16, 2023

In the following article, we will have a detailed description of two types of rotors for microcentrifuge: centrifuge fixed-angle rotor and swing-bucket rotor.

What is an Angle Head?

Angle head is the short form of the centrifuge fixed-angle rotor. The fixed angle θ between the centrifuge tube with solution sample and the rotary shaft is formed during the manufacture of the centrifuge rotor, usually 14°~40°. The position of the tube is fixed during centrifugation. When reorientation begins, the angle between the tube and the rotary shaft becomes smaller whereas the degree of reorientation becomes higher, increasing the efficiency of centrifugation. 

Features of Fixed-Angle Rotor

The fixed-angle rotor has a low center of gravity. It’s suitable for high-speed separation due to low resistance and stable spinning. 

It’s not suitable for large-volume separation. As particles are directed by the centrifugal force to hit the tube and slide along the tube wall to the tube bottom to form sediment, particles deposit on the other side of the tube and give rise to Coandă Effect, undermining the separation results. 

Mechanism of a Fixed Angle Rotor

a. Prepare the density gradient and add the sample on top of it, then insert the centrifuge tube into the rotor; b. When centrifugation accelerates, the gradient and sample layers undergo reorientation (radial direction); c. Sedimentation forms different layers; d. When the centrifuge rotor is in a static state, reorientation begins again (becoming a vertical gradient). 

Air-tight Angle Rotor & Non-airtight Angle Rotor

An air-tight angled rotor is made of metal. It should be tightened before centrifugation so as to prevent aerosol leakage from biohazardous samples (infectious microorganisms, radiation samples, viruses, etc.).

An air-tight angle rotor

A non-airtight fixed-angle rotor is made of plastic. It works immediately after installation. 

Explanation Of Centrifuge Rotor

What is a Swing-Bucket Rotor?

Horizontal rotor, also known as the swing-out head rotor, holds the centrifuge tube in a bucket which axisymmetrically hangs on the rotor. When the rotor spins, the bucket is swung from a vertical position to a parallel position due to centrifugal force, hence it is also known as a swing-out rotor and swing-bucket rotor, etc.

Mechanism Of The Horizontal Rotor

When the horizontal rotor is static, the microcentrifuge tube centerline in the rotor head is parallel to the rotating shaft. When the spinning accelerates, the centerline of the centrifuge tube gradually changes from parallel to nearly perpendicular to the rotation shaft. When the horizontal roto slows down, the centerline of the centrifuge tube gradually returns to a parallel position. 

Features of A Horizontal Rotor 

Horizontal rotor can handle the separation of large-volume samples. It is also versatile that can adapt to different applications. 

Horizontal rotor separation has a greater center of gravity. It induces more resistance and produces Coandă Effect that renders it unsuitable for high-speed separation. 

The Strengths and Weaknesses of Fixed Angle Rotor and Horizontal Rotor 

Centrifuge RotorStrength:Weakness:
Fixed-Angle Rotor-centrifugal tube and rotary shaft are pre-assembled-can withstand great centrifugal force -high rotor speed-centrifugal tube is slanted at a fixed angle, particles end up at the outer bottom wall of the tube, as a result, it has limited capacity
Horizontal Rotor-large capacity-can adapt to a wide variety of applications-easy for sample separation-rotor speed not too fast

Read more: Choose the Right Microcentrifuge Rotor for your experiment

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