Big Ideas on a Small Scale

UNM chemical and nuclear engineers help develop unique microfluidic devices

The days of drawing large vials of blood for lab tests may soon be over, thanks to a group of engineers and researchers at UNM's Department of Chemical and Nuclear Engineering. The multidisciplinary team is developing microfluidic devices that require just a few drops to conduct multiple "assays", or tests, to determine whether particular biochemicals are present in a fluid. The devices would test a blood sample for a number of diseases, analyze water for different toxins, or even test air samples for the presence of bacterial spores. But their size is the real surprise - the devices are so small they are measured in microns, a scale where 1,000 microns equal one millimeter.

Gabriel LopezGabriel Lopez, professor of Chemical and Nuclear Engineering, is the lead principal investigator on the project. He says that the devices would have a number of benefits. "Right now, if you need multiple blood tests, they have to take a lot of blood from you and run the tests separately. These microfluidic devices can do multiple analyses all at once. If we can make a small device that uses very small samples to do multiple tests, then they don't have to take as much blood, the analysis can be faster, and less expensive too," explains Lopez.

The minute devices use a screening process developed at UNM. The devices are tiny, glass capillaries or channels molded in silicone rubber and mounted on a glass slide. Each channel is only one or two inches long and just 200 microns wide - about the width of two human hairs. The channels are packed with thousands, and sometimes tens of thousands, of microscopic glass beads. Each bead measures between five and 30 microns in diameter.

Before researchers load the beads into the channels, they coat the beads with receptor proteins that naturally bind with proteins present in specific toxins, bacterium or diseases. Each channel can hold multiple sets of beads coated with different proteins. The sets of coated beads are separated by uncoated spacer beads. Researchers use tubes on either end of the channel to fill the channel with beads and to inject the fluid that will be tested.

The device is then placed on a mounting platform and exposed to a laser. The light "excites" the beads that have bound with a protein in the fluid and they start to "fluoresce", or glow. That fluorescence indicates the presence of a toxin or disease. By measuring the "excited state lifetime" and intensity of the fluorescence, the researchers can measure the level of the toxin in the fluid, and therefore make a diagnosis.

Mission To Miniaturize

The team is working on all aspects of the device in order to refine the analysis process and miniaturize the elements. "We're working on different parts of this technology: putting the beads into the little fluidic systems is one part, doing the detection of the reaction is one part, and developing new ways of detecting reactions from the standpoint of chemistry is another part," says Lopez.

Some researchers are refining the pump system that moves the fluid through the bead-packed channels. "It takes a great deal of pressure to drive the liquid through those tightly-packed beads," explains Lopez. However, the devices' small size and fragile construction cannot withstand too much pressure. To avoid applying pressure, the team has developed an electrosmotic pump, which uses an electric current to move the fluid easily through the beads.

Other team members are constructing a more compact, inexpensive way to detect the change in fluorescence lifetime from the beads - usually a period of just a few nanoseconds. The group had been using a large system that took up an entire corner of the lab and cost more than $120,000. They have managed to shrink most of that capability into an inexpensive, patented system they call CLAOS, or "closed loop auto-oscillating system." CLAOS fits on a small table.

Lopez says the goal for each element is efficiency - in a smaller package. "What we're trying to develop is a system that is more effective and more amenable to miniaturization. The hope is that the different parts of the system will converge in a few years to make a very compact device."

A Successful Collaboration

The process depends on teamwork. The research group includes about 15 researchers from Chemical and Nuclear Engineering, Chemistry, UNM School of Medicine, and the Center for High Technology Materials. A co-principal investigator from each area is assigned to the project. "What's important is that we have a research program that is working on many different aspects of this technology and it's bringing together a very wide group of people from a variety of departments. The combination of our team's expertise is unique," says Lopez. The group is also working with local businesses that are commercializing sensor technologies.

"The work that Professor Lopez and his collaborators are carrying out is a prime example of the exciting outcomes from combining the School of Engineering’s work in micro/nano technology with cutting-edge research going on in UNM's School of Medicine. It is enabled by the very effective collaboration among engineering, medicine, and the Center for High Technology Materials. Perhaps most importantly, the group is clearly focused on promoting commercial development of their work," says Joseph L. Cecchi, dean of the School of Engineering.

The five-year research project is funded by a $2 million grant from the National Science Foundation. Lopez says the competition for the grant dollars was extremely intense and UNM's study was one of the largest funded by the organization.

So, what's the big picture for these small devices? Lopez explains, "It might really have an impact on diagnostic capabilities in medical situations by making these tests smaller, cheaper and faster. And then those devices might find applications in science - allowing biologists to determine how biological systems work."

Research Team Receives Keck Grant

In July, a multidisciplinary team of researchers from UNM received a $500,000 grant from the W.M. Keck Foundation of Los Angeles. The foundation focuses on the areas of medical research, science and engineering. The grant will fund a laboratory and research program to explore complex fluid dynamics at nanoscale dimensions. Ultimately, the research could have pharmaceutical, environmental and diagnostic applications. Gabriel Lopez, professor of Chemical Engineering and Chemistry, led the team that won the grant.

Most of the $500,000 grant will go towards a confocal scanning laser microscope for the UNM Keck Nanofluidics Laboratory. Having the microscope will also create opportunities for research collaborations with Los Alamos National Laboratories, the National Science Foundation and other agencies.

"The Keck Foundation grant will help foster collaborative research between the School of Engineering and the School of Medicine, which is investigating the transport of complex fluids in nano-scale channels. Beyond the support itself, this award clearly recognizes the exciting potential of the work of Professor Lopez and his team."

Joseph L. Cecchi
Dean and Professor
School of Engineering