High-Resolution Imaging without the Need for
Environmental Isolation
by Joseph Fillion, Product Marketing Manager, FEI
Figure 1. SEM micrograph of a dog hair.
The rapidly accelerating pace of development in micro- and nanotechnologies has created growing demand for imaging capability beyond the 10003 magnification available from a typical light microscope (LM). Scanning electron microscopes (SEM) can generate useable information at magnifications higher than 100,0003, but they are typically slower, harder to use, and more expensive than LM. Now, a benchtop imaging system (Phenom™, FEI Company) combines the power of SEM with the speed and convenience of LM, delivering crisp, clear images at magnifications up to 20,0003 with about as much effort as a point-and-shoot camera.
The new instrument has been accepted in forensic applications where it can quickly acquire detailed images of almost any sample without preparation procedures that could negate the value of the evidence. More subtle, but perhaps ultimately much more important, the Phenom transforms the nature of SEM analysis, allowing investigators and technicians to examine and interact with the sample immediately without the delays inherent in evaluating evidence in a traditional SEM. This is particularly valuable in forensic applications where the course of the investigation is unpredictable and must be directed by discoveries made as it unfolds.
The new system departs from conventional SEM design in a number of fundamental aspects. Its miniaturized electron column is practically immune to mechanical and acoustical interference, permitting high-resolution imaging with no need for special facilities or environmental isolation. The touch-screen control interface and automated navigation capability permit simple, intuitive operation with little or no training. An innovative vacuum system achieves low-vacuum imaging conditions within seconds and eliminates most sample constraints and preparation requirements. Finally, and not insignificantly, the system’s cost of ownership is a fraction of that of a conventional SEM.
Forensic Applications
Figure 2. SEM micrograph of fibers cut with a knife.
Hair analysis can be used
to associate people with each other, or with a particular event or location, such as a crime scene. Microscopic examination of the hair can reveal the type of animal from which it came. For human hair, analysis can reveal race, the location on the body, and in some cases the specific individual from which the hair originated. The morphology of the cuticle, which comprises many layers of overlapping scales, is among the primary characteristics evaluated. The size, shape and overlapping pattern of the scales in this micrograph (Figure 1) indicate that the hair came from a dog.
Tool marks can also tie an individual to a crime scene. The fibers in Figure 2 were cut with a knife. Microscopic irregularities in the cutting edge can be matched to the tool marks to identify the specific tool used to make the cut. The score marks made on a bullet by the rifling in a gun barrel and the impression made on a shell casing by the firing pin are also examples of tool marks used in forensic analysis.
SEM analysis can reveal many of the circumstances that existed at the time an incident occurred. Figure 3 shows the filament of an automotive lamp. The presence of glass residue on the filament (bright areas) confirms that it was hot and that the lamp was illuminated at the time it was broken by the impact of the collision.
Paint chips are often found at the scene of hit-and-run incidents and can be used
to identify the automobile involved. The SEM image in Figure 4 clearly shows the multilayered structure of the coating. Contrast among the layers represents differences in their composition (average atomic number).
Figure 3. SEM micrograph of automotive lamp filament.
Figure 4. SEM micrograph of cross section of automotive paint chip.
Conclusion
The development of a practical benchtop SEM is in many ways analogous to the introduction of the desktop computer. Specifically, personal SEM analysis of forensic data reduces the time and complications associated with analysis at a centralized location. In forensics and many other applications, the added value of direct interaction between the investigator and the sample permitted by a “personal” SEM will likely lead to a rapid proliferation of these instruments.
For more information, contact Joseph Fillion, product marketing manager, FEI, at joseph.fillion@fei.com or by phone at 978-465-1861.
AT A GLANCE
• A new benchtop imaging
system combines the power
of SEM with the speed and
convenience of LM
• In forensic applications, it acquires detailed images without preparation procedures that could negate the value of the evidence
• It eliminates the need for special facilities or environmental isolation
• Direct interaction between the investigator and the sample will likely lead to a proliferation of these instruments
ONLINE
For additional information on
the technology discussed in this article, see Laboratory Equipment magazine online at www.LaboratoryEquipment.com or the following Web site:
• www.fei.com Laboratory Equipment Advantage Business Media
