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Atomic Force Microscope (AFM) – Definition, Principle, Application

The AFM, also known as the atomic force microscope (AFM) is a sort scanner probe. Its principal functions include measuring characteristics like...

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This article writter by MN Editors on November 26, 2021

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Atomic Force Microscope (AFM) - Definition, Principle, Application
Atomic Force Microscope (AFM) - Definition, Principle, Application

Definition of Atomic Force Microscope (AFM)

The AFM, also known as the atomic force microscope (AFM) is a sort scanner probe. Its principal functions include measuring characteristics like height, magnetism and friction.

Resolution is determined in millimeter. It is more precise and efficient than the optical Diffraction Limit. The probe used for measuring and collecting information that involves contact with the surface which has the probe. A picture is formed when the scanning probe microscope scans the probe over a specific area of the sample, analyzing its local properties simultaneously. Additionally, they contain piezoelectric components they are charged with electricity that are accumulated in certain solid materials, such as DNA biomolecules, crystals and others, to permit tiny, precise and precise movements in the scanning process based on an electrical command.

The Atomic Force Microscope was invented in 1982 by scientists at IBM immediately following having invented the Scanning tunneling Microscope in 1980 by Gerd Binnig and Heinrich Rohler by IBM Research in Zurich. This is the time when Binnig developed the Atomic Force Microscope, and it was first utilized for experiments in 1986. It was placed up for sale commercially in 1989.

Working principle of the Atomic Force Microscope

Atomic Force Microscope works on the idea of measuring intermolecular force and observing atoms using areas that have been probed of the specimen at nanoscale. Its function is supported by three major operating principles which are the ability to detect surfaces, surface sensing and Imaging.

AFM is also known as an Atomic Force Microscope (AFM) uses surface sensing to detect the presence of the cantilever (an element comprised of a rigid block that resembles plate or beam which is attached to the support’s end and protrudes from it to form a perpendicularly straight connection, which is vertical as the wall). The cantilever features sharp tips that scan across the sample’s surface by creating an attraction force between the tip and the surface when it is drawn closer to the sample’s surface. If it draws extremely close to the surfaces of the specimen, an inverse force slowly takes control, causing the cantilever to turn away towards the surface.

In the course of deflecting the cantilever from its surface of the sample there is a change in the direction of reflection the beam. A laser beam is able to detect the aversion by reflecting off a beam that is reflected off on the surface flat of the. Utilizing a positive-sensitive photo-diode (PSPDis a part which is based on Silicon PIN Diode Technology that can be used to determine the location of the integral focal point of the light signal that is coming in) It monitors the deflection changes and changes in the direction of the beam that is reflected, and then records the changes.

An Atomic Force Microscope (AFM) captures the image of the topography of the specimen by force, by scanning the cantilever across the area of significance. Based on the degree of elevation or deep the topography of the specimen is it will determine how the beam is deflected which is tracked by the positive-sensitive photo-diode (PSDP). The microscope is equipped with an electronic feedback loop that regulates its length. cantilever’s tip, which is just above the surface of the sample so it will keep the position of the laser, thereby generating an accurate surface map. the image.

Parts of the Atomic Force Microscope

Atomic Force Microscopes are equipped with a variety of methods for measuring forces, including van der Waals thermal, as well as magnetic forces. the interactions performed by the AFM It is equipped with the following components that aid in the control of its functions.

  • Modified tips that are used to determine the surface of the sample and to undergo deflections
  • Software adjustments are used to create images of the samples.
  • Feedback loop control – Feedback loop control is the process of controlling the force interactions and tips’ positions by through an optical deflector. the laser’s reflection is onto the back of cantilever as well as the tip, and when the tip is in contact with the surface of the sample the position of the laser on the photodetector is utilized to control the feedback loop, keeping track of an area of the specimen as well as measuring.
  • Deflection –  Atomic Force Microscope is built using an optical beam deflection system. The laser beam is reflected off the side of the AFM lever to the detector. They are constructed of silicon compounds, with the radius of 10nm.
  • Force measurement – how the AFM operates and relies heavily on the interactions between forces that contribute to the images produced. Forces are measured using calculations of the lever’s deflection after its stiffness is determined. This calculation is defined in Hooke’s law. The law is described in the following manner:

F= -kz where F determines the strength and K is its stiffness, and Z is the distance at which the lever is bent.

An AFM generates images by scanning a small cantilever over the surface of a sample. The sharp tip on the end of the cantilever contacts the surface, bending the cantilever and changing the amount of laser light reflected into the photodiode. The height of the cantilever is then adjusted to restore the response signal resulting in the measured cantilever height tracing the surface. | Image Source: https://en.wikipedia.org/wiki/Atomic_force_microscopy#/media/File:Atomic_force_microscope_block_diagram.svg

Applications of the Atomic Force Microscope

This type of microscope has been utilized in many fields of natural science like solid-state physics molecular engineering, semiconductor studies and polymer chemistry, as well as molecular biology, surface chemistry and cell biology, medicine and physical science.

A few of these applications comprise:

  • The process of identifying atoms in samples
  • Evaluation of the force interactions between atoms
  • Investigating the physical properties that change of the atoms
  • Investigating the mechanical and structural features of protein complexes as well as assembly, like microtubules.
  • It is used to distinguish cancerous cells from normal cells.
  • Comparing and separating neighbouring cells, their cell wall shape and rigidity.

Advantages of the Atomic Force Microscope

  • Simple to prepare samples to be observed
  • It is used in vacuums, air, as well as liquids.
  • The measurement of sample sizes is precise
  • It features a 3D-image
  • It is a method to study nonliving and living elements
  • It is a method to measure the roughness of surfaces.
  • It is utilized in environments that are dynamic.

Disadvantages of the Atomic Force Microscope

  • It can scan a single nano-sized image at approximately 150x150nm.
  • They have a short scanning speed, which can result in thermal drift to the sample.
  • The tip as well as the sample could be damaged in the process of detection.
  • It is limited in magnification, and a vertical range.
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Microbiology Notes is an educational niche blog related to microbiology (bacteriology, virology, parasitology, mycology, immunology, molecular biology, biochemistry, etc.) and different branches of biology.

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