Building a better tool

NRRI’s prototype lab improves chemical testing equipment

Steve Kossett was ready for a challenge. So when UMD Civil Engineering Professor Nate Johnson came to NRRI’s rapid prototype center with an idea to improve his research Kossett said, "Let’s give it a try."

Johnson uses voltammetric microelectrodes to measure the chemicals in river bottom sediments. To get accurate water concentration measurements between sediment particles with the least disturbance possible, the electrodes need to be tapered long and thin with an outer tip diameter no bigger than one millimeter.

"And one millimeter is fairly large, actually," said Johnson. "But the smaller it is, the more fragile."

Add to that tiny girth that the tapers are typically made of pulled glass. Rigid, but brittle indeed.

So Johnson’s idea was to make a custom taper at NRRI’s rapid prototyping center out of a less brittle material. Kossett, prototype center director, suggested an epoxy-based material using the laser precision of the stereolithography machine.

Even so, building the thin three-inch long taper with a tiny hole at the end was a challenge and tested the limits of the machine.

"But it worked better than I anticipated," said Kossett.

Johnson and Kossett worked on a half dozen different taper designs and chose a final design that has been working well in the lab.

"We took some samples in the St. Louis River estuary to measure chemicals, dissolved oxygen, iron and sulfide," said Johnson. "And we’ve had great success measuring vertical profiles that show depths at which different chemicals occur."

The custom designed taper and more durable voltammetric electrodes will help the scientists understand how hazardous chemicals move through the environment.

NRRI’s Northern Lights Technology Center has four different technologies for rapid prototyping — stereolithography, selective laser sintering, fused deposition modeling and two 3D printers. Each machine has different capabilities and can use different materials to build limitless items. For more information visit www.nrri.umn.edu/nltc or email Steve Kossett at skossett@nrri.umn.edu.