In 1975 a Stanford University researcher devised the first “lab on a chip,” essentially a series of incredibly tiny tubes etched in silicon and “seeded” with certain molecules that chemically react with the fluid being analyzed. In effect, the chip brings a super-miniature lab to the sample, rather than the sample to the lab. The result is a tremendous savings in time, expense and complexity.
Since that first effort, which placed a gas chromatograph on a silicon chip, the technology has expanded. It has been used for a variety of chemical operations, from analyzing gene expression in cells to performing environmental monitoring and medical diagnostic tests.
The complexity of tests, however, has been limited by the fact that current technology channels fluid in only two dimensions. But now Paul Bohn, Notre Dame’s Schmitt professor of chemical and biomolecular engineering, and his colleagues have found a way to extend the technique vertically. That opens the door to vastly more complicated and useful chemical processes.
The key to Bohn’s advance is NCAM or nanocapillary array membrane. Essentially an NCAM is a sheet of tiny pores or vertical tubes—10,000 times smaller than the width of a human hair—that the ND researcher uses to transfer minute amounts of liquid from one layer of a chip to another.
“We can take little electrodes and put them into each one of the holes and control flow of the liquid by regulating the electric potential,” Bohn explains. “That means we can run things up and down, over and across. And that is very valuable because, for instance, we can do a chemical separation in one channel, collect the product and move it up into another area of the chip for some reaction chemistry and then move it to another area for another operation. So it’s now possible to do a multiprocess, multistep chemical test.”