MICROSCOPE USES LIGHT TO GIVE UA RESEARCH NEW DIMENSION

FAYETTEVILLE, Ark. - With help from the National Science Foundation, University of Arkansas researcher Peter Ungar has acquired a powerful white light scanning confocal microscope that will add new dimension to research projects across campus.

Though compact enough to fit on a small desk, the new instrument offers big advantages over other microscopes. It enables researchers to examine materials at a vertical resolution much higher than previously possible - recording measurements every five nanometers at its highest setting. Additionally, the white light microscope produces three-dimensional images of objects and materials, offering information about the depth of specific features that researchers could only guess at before.

"The difference between two-dimensional microscopy and three-dimensional is pretty amazing. It’s like the difference between Pac-Man and the video games you see out there today," said Ungar, associate professor of anthropology. "Both in the information it stores and the information we can glean from what we see, this instrument is a whole level beyond scanning electron microscopes."

As principal investigator on the grant proposal, Ungar received $218,571 from the NSF and additional funds of $98,674 from the U of A to purchase the microscope. The instrument primarily will be used to facilitate Ungar’s investigation of microscopic wear on the teeth of primates and human ancestors.

But part of the incentive to acquire the white light microscope was the instrument’s versatility. Ungar points out that the microscope will play a role in numerous faculty and student research initiatives in disciplines across the University.

"It has uses for biosensor development, microelectronics, plant pathology. Highlighting the multiple applications of this microscope on campus was a big part of the grant proposal and probably contributed to the proposal’s success," Ungar said. "This is brand new technology that has broad theoretical and practical benefits, and we proved to the NSF that our researchers will take advantage of the instrument’s full capabilities."

In addition to Ungar’s work, the grant proposal outlines six research applications for the white light microscope and notes that students in dozens of labs and courses across the University will learn to use the instrument in the course of conducting research.

For example, Ken Korth, assistant professor of plant pathology, will use the microscope to study how calcium oxalate crystal formation in damaged leaves deters insects from feeding on plants. Stephen Batzer, assistant professor of mechanical engineering, intends to use the instrument for refinement of cutting tools and for the development of micro electro-mechanical systems and electronic packaging systems.

John Dixon in geosciences will use the microscope to observe and measure the effects of chemical and biochemical weathering on the landscape. And Jean-Francois Meullenet in food sciences will use it to understand the effects of processing technologies on the qualities of foods.

"One of the primary advantages of using the white light microscope as opposed to a scanning electron microscope is that it will minimize sample preparation," Korth said. "In addition to getting a better image, we’ll be able to look at many more samples in a given amount of time."

Scanning electron microscopy uses a charged stream of electrons to detect the surface features of a sample, so objects must be coated with an electrically conductive material such as gold before being placed in the microscope. But because the UA’s new microscope uses reflected white light rather than electron interactions to create an image, no coating of the sample is required.

According to Ungar, this will make a significant impact on the pace of his own research, for which he examines hundreds of different tooth specimens from numerous species. Ungar relies on epoxy casts to study wear patterns on fragile fossil teeth or on samples from living primates. Because the material used to create these casts is translucent, Ungar had to coat each specimen before inserting it into the scanning electron microscope. Even when using real teeth, the translucence of dental enamel made it necessary to prepare samples before study - a process that sometimes damaged the specimens.

But even more significant than trimming preparation time, the accuracy of the white light microscope will advance Ungar’s research, he said. By studying the wear patterns on a species’ teeth, Ungar can make inferences about the foods that comprised the species’ main diet. And by comparing this evidence across different species, Ungar hopes to gain information about the way that diet developed and changed throughout the process of human evolution.

In pursuing this research, Ungar must discern, quantify and measure the microscopic scratches and pits that etch the enamel surface of each tooth. Scanning electron microscopy made such features visible, but the image it produced presented scratches and pits qualitatively - as areas of visual contrast against the uniform field of the tooth surface.

"The problem then is that you have to count and measure those features by hand, which introduces a high likelihood of human error. That’s a very subjective process, and you’re going to get variability between the measurements of any two researchers," Ungar said. "We needed an objective, automated, repeatable way to quantify wear on teeth."

Ungar, himself, had attempted to solve this problem by developing MicroWare - a software system that automatically quantified scratches and pits on a tooth surface. But measuring the features still had to be conducted by hand. With the white light scanning confocal microscope, both problems are solved, according to Ungar.

Rather than creating an image that represents the visual surface of a sample - the way scanning electron microscopes do - the white light microscope constructs an image based on measurements of that surface. It collects and presents information quantitatively. Therefore, length, width and even depth information about specific features is automatically and objectively recorded by the instrument.

"With an objective, reliable way to quantify dental wear, we can start looking at the big picture. We’ll no longer be scrutinizing every pin-prick-sized surface of tooth," Ungar said. "We can look at the whole surface and start figuring out what that tells us about the interaction between food and teeth."