Over the years I have published a few case studies, mostly in ASM International publications. Probably the one that has generated the most sustained interest is the one on how to teach yourself to do fracture analysis using fractures of carrots, chocolate, apples, and lollipops. Using a scanning electron microscope (SEM), we take such fun to a new level. Rather than just using our eyes, we can expand the range of sizes of details that we can view. In metals and plastics, there are types of features that are visible only with the enhanced magnification available using the SEM, that provide information on how the materials were processed during the manufacturing operation. I won't get into those types of "micro-fractographic" features in this article. We will look at the same type of "macro-scale" features that we can see with the carrots and chocolate, but on very small things, that we could not otherwise see.
To get specific, let's take a look at a Japanese beetle. Please note that although I have been known to squash live specimens found attacking my young fruit trees and roses, no beetles were killed to perform the SEM research! After the building which used to house the laboratory had a fire in 2007, I found a few (obviously long dead) desiccated beetle carcasses in an empty beaker in my window. This was great practice for me to learn to use my newly acquired SEM.
Note that a hair, perhaps somewhat similar to the one from the chest, pokes out of the center of the pore. The pore is surrounded by a different type of flattened protruding features. These "flat" hairs cover large areas of the lower abdomen of the beetle.
As my machine shop's employee noted, with these techniques, we can see the hair in a beetle's nose!
One more useful feature available on many scanning electron microscopes is an EDS microchemical analyzer. This is an instrument that can determine the atomic elements present in very small things. A portion of the beetle's face was analyzed, and the result is shown below. Please note that except in some specialized SEM's, the specimen must be electrically conductive. Most previously living things don't fall into this category. So in order to render the specimen electrically conductive, I sputter coated a thin layer of palladium (Pd) onto the beetle. We can see that the beetle skin is made of mostly carbon and oxygen.
This is not a surprise. Most life forms are heavy on CARBOHYDRATES. We can't see (detect) hydrogen with the EDS method. But we see the carbon and oxygen that are major elements of life. We can also see a small amount of nitrogen, a type of atom found in PROTEINS. Chlorine (Cl) is a part of salt, so that trace amount is also not a surprise. Neither is the palladium I just said I put on intentionally to be able to analyze the beetle at all. I am still not sure why a beetle would have any aluminum in it. While the beetle looks shiny and metallic, it looks more coppery than aluminum. However, I suspect that the colors we see are a result of other causes than metallic elements. In any case, I have not had a chance to analyze the coppery wings! The aluminum might also not really be there. The EDS method has its limitations. In this case, in small amounts, aluminum and bromine are difficult or impossible to distinguish. The aluminum might be bromine! We will leave these mysteries for someone else or some other time!