Researchers Build The World’s Smallest Self-Contained Electrochemical Analyzer

Ingrid Fritsch, associate professor of chemistry, will present the group’s findings today (Oct. 18) at the 1999 joint international meeting of the Electrochemical Society and the Electrochemical Society of Japan in Honolulu.

Scientists use analyzers to examine the glucose content of blood in diabetics and pollution levels of lakes, streams and city water sources. Many of the ones they use today take hours and sometimes days to produce results, and samples must be brought to the laboratory for analysis.

Smaller analytical tools use less power and require fewer materials for building. They may, therefore, be more widely available and more portable than their current, larger predecessors, and may be used in the field or on the human body.

Fritsch and graduate student Walter R. Vandaveer IV analyze microscopically small samples using electrochemistry, in which the current between two electrodes can be used to measure the quantity of a chemical compound.

The wells that contain the samples measure only 10-50 microns in diameter and eight microns deep; to put that in perspective, a human hair has a diameter of 200-300 microns. Fritsch and her colleagues worked with engineers at the university’s High Density Electronics Center to fabricate multiple wells on a surface smaller than a postage stamp. The tiny silicon chips have layers of conductors and insulators that create the electrochemical cell in the tiny well.

"This would be useful if you want to do a study on a single cell or strand of DNA," Fritsch said.

Fritsch already has one researcher in her laboratory looking at microscopic immunoassays — an analysis that can be used to detect antibodies in humans.

At such small sample sizes, Fritsch has found that the issues for detecting compounds change. First, small drops of solution evaporate quickly, so analysis must speed up, or the researchers must find a way to trap the solution indefinitely, Fritsch said.

Second, as the electrodes close in on one another, they begin to affect one another; the current at one electrode may regenerate at the other electrode, amplifying the signal — a phenomenon that could be good or bad.

"What is a disadvantage on one hand can be an advantage on the other," Fritsch said. When detecting tiny quantities of a compound, amplification, which is a possible advantage, can mean the difference between detecting a signal and seeing nothing, she said.

Because electrochemical theory applies to mostly larger quantities of solutions, Fritsch and her colleagues have used computer models to simulate electrochemical responses for different electrode configurations, dimensions, time scales and solutions.

They are using these simulations to better understand the electrochemical phenomena on the small scale.