Trends in Microanalytical Sample Prep
His expertise is in failure analysis, material analysis, and microanalysis of small particles and contaminants using polarized light microscopy, infrared microspectroscopy, Raman spectroscopy, and scanning electron microscopy with energy dispersive X-ray spectrometry. Rich enjoys helping clients solve challenging issues with his microanalytical expertise. His nickname is the “Particle Detective.” Rich developed his expertise in particle characterization over a 30-year career analyzing a variety of materials, including fibers, glass, paints, metals, polymers, nanoparticles, and others. He has published his microanalytical work and interesting case studies in numerous peer-reviewed journals and book chapters.
Q: What sort of work does MVA Scientific Consultants do?
A: We’re a full-service analytical microscopy laboratory. We offer customized contract testing, investigative analysis, particle sizing, and consulting services to help all types of industries solve problems. We do that with our microscopes—we have scanning electron microscopes, transmission electron microscopes, polarized light microscopes, and interference microscopes for surface roughness, just to name a few. We have 21 staff members, though that number varies with interns coming in and out.
Q: What kind of sample prep does your work involve?
A: The work we do for the most part is nonstandard, so the sample prep really depends on what type of particle sample we get. Sometimes they can be multiple particles agglomerated together, or it could be a large piece of material that needs to be cut up or sectioned so that we look at particles that are either inside of it or adhering to it. Particle prep is done manually and it’s a very time-intensive and skill-oriented type of work for us.
Q: How long does that sample prep take?
A: It varies. Sometimes [we’re working with] a single particle, a particle being usually less than a millimeter, or we have visible and sub-visible [particles] that are 100 micrometers and smaller. It could be a single particle or just a couple of particles that have to be taken through three or four different microscopy labs. We’ll use a number of different analytical techniques, like FTIR microscopy or Raman microscopy, SEM, and polarized light microscopy on the same particle or on sub-samples of particles from the same sample. So it could take an hour or it could take several days. We had one sample where the prep, since it was a total unknown, took us several days to actually separate it from the substrate of interest. That was a fun one.
Q: What main trends or changes have you seen in sample prep over the years?
A: What we’re seeing is that in some of the tools that we use to prep, like ion mill cross-section polishing, equipment is getting better and more precise. So even though the person who’s actually doing the sample prep has to spend some time learning the technique, they have better tools. We have better ways of cutting and polishing samples to get them ready for analysis. The sample prep tools are becoming much more reliable, too, so it saves us time in the long run. The tools we use to do the actual analysis are also getting better. So if we have a technique that can analyze a surface that needs very little sample prep other than putting it under the microscope, that’s a nice technique for us because we can do a lot of analyses on a particular area very, very quickly. That saves us time, saves the customer time, and eventually saves everyone money.
Q: What process do you go through in your sample prep?
A: The first thing that we do is look at the sample and make some determination as to what we have. So if we have, say, a collection of black particles, some of them could be elastomeric (rubber) and some of them could be plastic, which means they basically deform when you press on them and they don’t spring back, so immediately we’ve got two different types of material we have to deal with. Some could be glassy, some could be mineral, and some could be metallic. Each one of these particle types would go through a microscopy laboratory in a different order, or subsamples would go to different microscopes simultaneously so that we get the most information out in the least amount of time. Not that we do things so quickly that we don’t do good work—everything we do, we study.
Q: How do you handle that challenge of moving quickly while avoiding mistakes?
A: We try to minimize sample handling time so that we can do either multiple techniques simultaneously if the sample’s big enough or we can hand-carry it from one laboratory to the next so the people involved in the analysis can communicate at that point and say, “This black particle is what I need analyzed. Never mind the other two.” They have a system set up so that we don’t waste any time thinking about, “Was that the one I was supposed to do?” We really have to have that communication going among all the staff to make sure that we do the right material— that gives us the opportunity to provide a timely analysis—and also perform reliable work. Once [samples] go through different microscopy techniques or different microscopes, different analyses, all those tests should correlate. For example, if the FTIR microscope finds a nylon material and there’s an indication that there’s clay filler, then polarized light microscopy should have seen the polymer—the nylon—and if it’s transparent, they should have seen that there was some type of filler in it. So we have to communicate at that level, too, once the process is done to make sure that everyone’s on the same page for quality analysis. If we do see a difference, we back up and try to determine if we need more testing. That’s the most important part of our work, maintaining communication so that we don’t lose any time.
Q: What are some of the most interesting or strange samples you’ve worked with?
A: We’ve done such a variety of things that it’s really hard to pick the most interesting. Offhand, just about everything we look at is new to us. A lot of times we look at new materials that have just been produced by a new process and sometimes we’re either the first to see them microscopically or we’re one of the first groups of people to see them microscopically. One example of an interesting project we did is examining portable airfields. The military can place a portable airfield in just about any location in the world if they have enough of these mats and enough Marines to put it in place. What was happening is that when the mats were being refurbished, they were popping, or setting off a small discharge when workers arc-welded them. So we were looking for things like jet fuel contamination, and it turned out to be just the fact that these sealed aluminum pieces had been in service for 20 to 30 years. When they did the original work, they sealed up enough material inside to cause a little bit of corrosion and it built up hydrogen over time. So when they were opened and they struck an arc, they [had] a little bit of hydrogen to burn, which was enough to frighten the people doing the welding. It’s mostly the investigative part that makes our work interesting—what are these particles and where do they come from, and why are they in my product?
Q: What changes do you expect to see in the future for your lab, in terms of sample prep?
A: On the sample prep side, I hope to see the trend toward better tools increase. It’s still going to be a very tedious, manual sample prep, but I’m hoping at some point we’ll be able to come up with instrumentation that can do more with less sample prep and help get things through the laboratory faster without compromising any of the analytical abilities that we have or any of the time that we spend on samples.
Q: What key advice would you have for labs that are just getting into sample prep for analytical microscopy?
A: Be prepared to work. This is highly skilled work that takes a good amount of experience and time. In my professional dealings, there’s some apprehension when looking at a new sample. You don’t know where to start. You don’t know if you’re going in the right direction. In this industry, you can’t be afraid to fail. You have to come up with a protocol, stick to it, follow it to its end point, and then see if you need to do more work. You just can’t be afraid to work because it’s very time-consuming and very challenging.