UWM Researcher Hopes Sensor is Step Toward Lead Contamination Solution

May 25, 2017

Mechanical engineering researcher Junhong Chen believes his wafer-thin sensor will help detect even trace amounts of lead in water.

PhD candidate Guihau Zhou is one of six students who have dedicated three years helping Chen develop the technology in his lab at the Global Water Center in the Walker's Point neighborhood.

Credit Susan Bence / Milwaukee Public Radio

Zhou demonstrates by extracting a drop of water from a vial and releasing it onto a wafer-thin sensor. I wager it would take 10 sensors to fill the surface of a DIME.

The water contains lead.

Zhou glances at the sensor’s “reaction” on a computer screen. The lead causes a spike on the graph.

Professor Chen says while nobody wants to see lead in water, he’s glad his sensor worked.

“That’s what you typically would hope to see. When you have lead, you would see a change and if you have high concentration you see a larger signal,” Chen says.

Back to that wafer-thin sensor. Its key ingredient is graphene. It’s a single-atom thick sheet of carbon atoms. If you could SEE its structure it looks like a delicate honeycomb.

Right now Chen's team is manually constructing the sensors, as you can see are much smaller than a dime.
Credit Susan Bence / Milwaukee Public Radio

Chen says graphene is sensitive to any change in its environment, for example when lead is introduced.

"The graphene-based material really enables this type of detection, but there’s also gold, silicon wafer that is the substrate we are using. So there are a bunch of other materials inside," Chen says.

Yet he wasn’t thinking about lead when he first started experimenting.

He was working on a way to detect early-stage cancer. That was 2010.

“It worked out really well, so we published the results and we also filed a patent and the patent was recently allowed and in is in the process of being issued,” Chen says.

In addition to his research and teaching, Chen One is leading a National Science Foundation-funded collaborative, called the Water Equipment and Policy Center. It pools the brains of both UW-Milwaukee and Marquette University researchers along local industries, including A.O. Smith.

Chen says they urged him to apply his findings to detecting lead.

“Everybody is saying, if we can detect lead quickly and at low cost everybody is saying there is a lot of market demand,” Chen adds, “That was way before the Flint water crisis.”

The National Science Foundation fueled action with funding.

Credit Susan Bence / Milwaukee Public Radio

Chen says he’s now close to releasing a handheld device. The prototype resembles a garage door opener with a screen.

“You put a drop of water in the cavity here and then turn on the power and it shows you the lead concentration,” Chen explains.

He says the device is easy to use and would could be used at home to test the water coming out of your tap.

“I would collect a small volume of water from my tap and put it into my device and it would show you the concentration of lead. If it’s safe, the green light would turn on. If it’s unsafe, the red light would turn on, and if it’s borderline it would be a yellow light," Chen adds, "In the meantime it should also display the actually concentration of the lead."

Chen says people might eventually be able to install a version of his sensor inside a faucet or water meter. Those chips could relay alerts on your iPhone or computer.

“And we should integrate this technology into this next generation of infrastructure; integrate these sensors into our water distribution pipelines, then we would be able to monitor this water quality continuously in front of a computer for example,” Chen says.

What others would have to determine, is the remedy to lead in the water.

As for Chen, he predicts it will be relatively easy to tweak his technology to pick up other contaminants, such as mercury and bacteria.

He admits this water quality mission could consume the rest of his professional life.

Mechanical engineering researcher Junhong Chen (left) with two members of his team PhD student Guihua Zhou and postdoc Arnab Maity.
Credit Susan Bence / Milwaukee Public Radio