By Emmanuel Ageta
As early as 1930s developed countries had started using some microbeam analysis technology, not until early 1990s that the need for standardization and Metrology became necessary, as of now eighteen standards under a Technical Committee (TC) of International Organization for Standardization ( ISO/TC 202 Microbeam analysis), have been developed to cover terminologies, guidelines, methods for determination of different quantities and calibration of image magnification by using reference materials with periodic structures.
A microbeam is a narrow beam of radiation, of micrometer or sub-micrometer dimensions. Together with integrated imaging techniques, microbeams allow precisely defined quantities of damage to be introduced at precisely defined locations. Thus, the microbeam is a tool for investigators to study intra- and inter-cellular mechanisms of damage signal transduction, Scientific and routine research is possible.
However, microbeam input beam may comprise light (including laser beams), X-rays and other electro-magnetic waves, electron, protons or ions, the output signal include light, X-rays, electron and ions. The scope of the TC is standardization in the field of microbeam analysis (measurement, parameters, methods and reference materials) which uses electrons as an incident beam and electrons and photons as the detection signal.
The purpose is to analyze the compositional and structural characteristics of solid materials. The volume of analysis will generally involve a depth up to 10 micrometers and a surface area less than 100 square micrometers. Given a wide range of applications of equipment that uses microbeam analysis, such as an electron microscope are used to investigate the ultrastructure of a wide range of biological and inorganic specimens including microorganisms, cells, large molecules, biopsy samples, metals, and crystals.
Industrially, electron microscopes are often used for quality control and failure analysis. Modern electron microscopes produce electron micrographs using specialized digital cameras and frame grabbers to capture the image. Under microbeam analysis technology, several detectors with Ultra-high Resolution like Scanning Electron Microscope will be discussed later in this article.
However there are some key terms that need to be differentiated for clear understanding of this subject. Notably; Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye, the branches include; optical, electron and scanning probe microscopy whereas Microanalysis is that analysis of spot size ranges from about 100 micrometre to 100 nanometre this allows analysis at atomic or molecular resolution which form part of nanotechnology or nanoanalysis.
Microscopy and Microanalysis has a peer-reviewed scientific journal that covers original research in the fields of microscopy, imaging, and compositional analysis, including electron microscopy, fluorescence microscopy, atomic force microscopy, and live-cell imaging. Difference between Spectroscopy and Spectrometry; Spectroscopy is the study of the interaction between matter and radiated energy. This can be interpreted as the science of studying the interactions of matter and radiation. In order to understand spectroscopy, one must first understand spectrum. The visible light is a form of electromagnetic waves.
There are other forms of EM waves such as X-Rays, Microwaves, Radio waves, Infrared and Ultraviolet rays. The energy of these waves is dependent on the wavelength or the frequency of the wave. High frequency waves have high amounts of energies, and low frequency waves have low amounts of energies, whereas Spectrometry is the method used for the study of certain spectrums. Ion-mobility spectrometry, mass spectrometry, Rutherford backscattering spectrometry, and neutron triple axis spectrometry are the main forms of spectrometry.
Spectrometers are the instruments used in spectrometry. The operation of each type of instrument depends on the form of spectrometry used in the instrument. The term spectroscopy is normally reserved for measurements of the electromagnetic spectrum. Words ending in -scopy mean “looking at” whereas words in -metry mean “measurement of”.
It became known that for laboratories operating under accreditation scheme, the operator of technology of microbeam analysis equipment like Microscope/microprobe must have available internal, national or international standards which should be applicable to any quantitative analysis. Therefore, the requirements, specification, guidelines or characteristics of methods, instruments or samples are provided with the final goal that these can be used consistently. This will ensure that microbeam analysis results are reliable and meet international quality management requirements.
The 25th Plenary meeting of this ISO/TC 202 Microbeam analysis was hosted by UNBS at Hotel Africana from 19th to 21st September, 2018 in Kampala, Uganda
The TC has been conducting its business plan developed since 2005 under four areas; Terminology, Electron probe microanalysis (EPM), Analytical electron microscopy (AEM), and Scanning electron microscopy (SEM). The overall management of the TC sub-committees is under ISO/TC 202 Microbeam analysis.
There is close collaboration of this TC with ISO / TC 201 Surface chemical analysis and, its scope covers standardization in the field of surface chemical analysis. Surface chemical analysis includes analytical techniques in which beams of electrons, ions, neutral atoms or molecules, or photons are incident on the specimen material and scattered or emitted electrons, ions, neutral atoms or molecules, or photons are detected.
It also includes techniques in which probes are scanned over the surface and surface-related signals are detected which excludes Scanning electron microscopy which is within the scope of ISO/TC 202 Microbeam analysis.
There is also a closed collaboration with ISO/TC 229 Nanotechnologies, the scope of this TC covers; Standardization in the field of nanotechnologies that includes either or both of the following: Control of matter and processes at the nanoscale, typically, but not exclusively, below 100 nanometres, also utilizes properties of nanoscale materials that differ from the properties of individual atoms, molecules, and bulk matter, to create improved materials, devices, and systems that exploit these new properties.
Standards developed covers: terminology and nomenclature; metrology and instrumentation, including specifications for reference materials; test methodologies; modelling and simulations; and science-based health, safety, and environmental practices.
Equipment that uses microbeam analysis technology have a wide applications in nanotechnology to carry out analysis in the structural composition of Nanoparticles / Magnetic Nanostructures, Nanobelts, Nanolubricant, Nanocrystals & Nanopowders, NanoFillers / NanoAdditives, Dispersions, Nanorods, Nanosponge Abrasives, Nano Tubes, Nanowires, Quantum Dots / Nano Dots, Reactive.
Scanning Electron Microscopes (SEM) and Ion Microscopes deliver high resolution surface information and superior materials contrast. They are widely used in electron microscopy sciences and application fields such as nanotechnology, materials analysis, semiconductor failure analysis, life sciences, quality assurance and Scientific and research development. Scanning Electron Microscopes (SEMs) and Transmission Electron Microscopes (TEMs) can be fitted with a range of detectors (e.g. EDS, EDX, ED, etc.), that can give information about chemical composition and structure. TEM ranges of analysis is from 0.1 nm to 100 nm and SEM ranges of analysis is from 1 mm to 100 nm.
An Ultra high Scanning Transmission Electron Microscopes (STEM) resolution specification of 0.34 nm, enabling the observation of graphite lattice fringes for example in a carbon nanotube; Carbon nanotubes are very thin, hollow cylinders made of carbon atoms. They are about 10,000 times thinner than a human hair. Carbon nanotubes are produced using various thermal processes to strip carbon atoms from carbon-bearing materials and use them to form cylindrical carbon structure that has hexagonal graphite molecules attached at the edges.
The elasticity modulus of multiwall nanotubes (MWNTs) is analyzed with transmission electron microscopes (TEM). As a result of the strength of the atomic bonds in carbon nanotubes, they not only can withstand high temperatures but also have been shown to be very good thermal conductors. They can withstand up to 750°C at normal and 2,800°C in vacuum atmospheric pressures. The temperature of the tubes and the outside environment can affect the thermal conductivity of carbon nanotubes.
Some of the major physical properties of carbon nanotubes are summarized below;
There are several techniques that have been developed for fabricating CNT structures which mainly involve gas phase processes.
The properties of nanotubes are certainly amazing; many studies have suggested potential applications of CNTs and have shown innumerable applications that could be promising when these newly determined materials are combined with typical products. Applications for nanotubes encompass many fields and disciplines such as medicine, nanotechnology, manufacturing, construction, electronics, and so on. Studies have shown that water-soluble CNTs are biocompatible with the body fluids and do not have any toxic side effects or mortality. A lot of studies have been done to address the barriers in CNT.
Nanomaterials show probability and promise in regenerative medicine because of their attractive chemical and physical properties. Generally, reject implants with the post administration pain, and to avoid this rejection, attachment of nanotubes with proteins and amino acids has been promising. Carbon nanotube, both single and multi-WNT, can be employed as implants in the form of artificial joints and other implants without host rejection response. Moreover, because of unique properties such as high tensile strength, CNTs can act as bone substitutes and implants if filled with calcium and shaped/arranged in the bone structure.
The aim of tissue engineering is to substitute damaged or diseased tissue with biologic alternates that can repair and preserve normal and original function. Major advances in the areas of material science and engineering have supported in the promising progress of tissue regenerative medicine and engineering. Carbon nanotubes can be used for tissue engineering in four areas: sensing cellular behavior, cell tracking and labeling, enhancing tissue matrices, and augmenting cellular behavior.
Cell tracking and labeling is the ability to track implanted cells and to observe the improvement of tissue formation in vivo and noninvasively. Sensing cellular behavior, enhancing tissue matrices, and augmenting cellular behavior have not been explain here in details.
Cancer cell identification
Nanodevices are being created that have a potential to develop cancer treatment, detection, and diagnosis. Nanostructures can be so small (less than 100 nm) that the body possibly will clear them too quickly for them to be efficient in imaging or detection and they can enter cells and the organelles inside them to interact with DNA and proteins.
Since a large amount of cancers are asymptomatic throughout their early stage and distinct morphologic modifications are absent in the majority of neoplastic disorders in early stage, consequently traditional clinical cancer imaging methods, for example, X-ray, CT, and MRI, do not acquire adequate spatial resolution for detection of the disease in early stage. Many important tumor markers have been extensively applied and used in the diagnosis of hepatocellular carcinoma, colorectal cancer, pancreatic cancer, prostate cancers, epithelial ovarian tumor such as carbohydrate antigen have been handled using this technology.
Others microbeam applications;
Gasification is a technology that converts carbon-containing materials, including coal, waste and biomass into synthetic gas which in turn can be used to produce electricity and other valuable products, such as chemicals, fuels and fertilizers.
Microbeam provides advanced analysis and services applicable to electrostatic precipitators to address the challenge of poor particle collection due to changes in fuel characteristics. Electrostatic precipitators is not covered here in details.
Microbeam identifies the problem through advanced fuel analysis, which provides the size and composition distribution of the particles. Based on this information, we can determine the resistivity and cohesivity of the ash and identify steps toward achieving more efficient particle collection.
Besides the above mentioned benefits of microbeam technologies, microbeam advanced analysis are applicable in the following areas; combustion, Scanning Electron Microscopes (SEMs) Morphological Analysis to fully characterize materials, Viscosity Measurement – T250 (Viscosity of slags can be measured in either oxidizing or reducing environments using the crucible method of T250 measurement test. T250 is the temperature at a viscosity of 250 poise), Sintering Testing as a function of temperature under selected atmospheres and pressures, etc
Microbeam uses a variety of different technologies for conducting analysis and testing for samples by using computer-controlled scanning electron microscopy (CCSEM) to determine the size, composition, abundance, and association of mineral grains in prepared coal, biomass, and petroleum-coke samples. With this information, we can assess the behavior of the mineral grains during combustion or gasification. CCSEM analysis can also help us predict impacts of fuel properties on wear of system components, slag flow, fouling of heat exchangers, fine-particle collection, and ash handling. These technologies are not been described in this article.
With automated computer-controlled scanning electron microscopy (CCSEM), Microbeam analysis equipment analyzes fuel sample cross-sections utilizing backscattered electron imaging (BEI) combined with automated particle recognition and chemical analysis. This method allows us to determine the composition, size, and abundance of mineral types in fuel. So many details of Microbeam’s advanced analysis and services have not been exhausted here.
Other X-Ray Methods of analysis are not discussed here:
An X-ray microscope uses electromagnetic radiation in the soft X-ray band to produce magnified images of objects. Since X-rays penetrate most objects, there is no need to specially prepare them for X-ray microscopy observations. The resolution of X-ray microscopy lies between that of the optical microscope and the electron microscope . It has an advantage over conventional electron microscopy in that it can view biological samples in their natural state. Electron microscopy is widely used to obtain images with nanometer to sub-Angstrom level resolution but the relatively thick living cell cannot be observed as the sample has to be chemically fixed, dehydrated, embedded in resin, and then sliced ultra-thin. By analyzing the internal reflections of a diffraction pattern (usually with a computer program), the three-dimensional structure of a crystal can be determined down to the placement of individual atoms within its molecules. The best technique to use will depend on the required spartial resolution and depth resolution, either by quantitative or qualitative chemical analysis and the most common type of X-rays analysis is the Energy Dispersive X-ray Spectroscopy.
Focused Ion Beam Scanning Electron Microscopes
FIB-SEMs you combine the imaging and analytical performance of the GEMINI column with the ability of a next-generation FIB for material processing and sample preparation on a nanoscopic scale. Use the modular platform concept and the open and easily extendable software architecture of this 3D nano-workstation for high throughput nanotomography and nanofabrication of even your most demanding, charging or magnetic samples
Scanning Electron Microscopes
Scanning Electron Microscopes (SEM) by Carl Zeiss deliver high resolution surface information and superior materials contrast. They are widely used in electron microscopy sciences and application fields such as nanotechnology, materials analysis, semiconductor failure analysis, life sciences and quality assurance
The writer is a Metrologist at the Uganda National Bureau of Standards (UNBS).