Simple wood makes advanced sensors

The researchers at the Center for Advanced Sensor Technology (CAST) at UMBC, however, have a different adjective they aim for when designing tech: dirt cheap.

Revati Kadolkar in the CAST lab where the team works on inexpensive sensor technology. (Brad Ziegler/UMBC)

For these scientists and engineers, inexpensive doesn't mean low-quality—it means challenging traditional ways of thinking to produce affordable and reliable products that meet vital needs. Toward this end, a CAST research team recently debuted a new environmental sensor made out of simple balsa wood sheets—the kind you could buy at a craft store for a few dollars. The wood was cut and assembled to make a central well to hold samples and channels for the electrochemical components of the sensor to be inserted. The researchers coated the wood to make it waterproof and stuck it together with wood glue. 

Inexpensive and sustainable

Choosing wood served two purposes: making the sensor low-cost and also environmentally friendly. 

"Sustainability was very important to us," says Revati Kadolkar, a Ph.D. student in chemical engineering who is working on the project. Kadolkar is advised by professors Govind Rao, who directs CAST, and Douglas Frey in the department of chemical, biochemical, and environmental engineering (CBEE). "Using wood instead of plastic for the structural skeleton of the sensor was a key step toward that sustainability," she says.

In collaboration with another UMBC team from the Center for Urban Environmental Research and Education led by CBEE professor Claire Welty, the CAST team tested the sensor in the field by measuring nitrate levels in streams in the Gwynns Falls watershed near Baltimore. Nitrate is a pollutant, often linked to agricultural activities, that can cause gut cancer, birth defects and a condition called methemoglobinemia, also known as the blue baby syndrome. Its concentration in tap water in the U.S. is regulated by the Safe Drinking Water Act. The accuracy of the sensor's readings was on par with traditional equipment that cost hundreds of times more money, the researchers say. 

Testing in the lab, the team also found the sensor worked well across a range of conditions, including wide variations in temperature and pH levels, and continued to operate well for more than a year. 

A schematic shows the layers of the wood sensor, with openings for the three electrodes and a microwell. (Image courtesy of Kadolkar)

A more comprehensive view of the world

Driving down the cost of technology should drive up its impact. Cheaper sensors could be deployed in higher numbers, yielding a more comprehensive view of the world and spotting potential problems earlier. 

"Let's say you want to map the whole Chesapeake Bay and know every hour if there is contamination and how it is traveling down the bay," says Venkatesh Srinivasan, a research associate professor at CAST who also worked on the project. "You can get these details more easily if you have lower-cost sensors."

Spreading the benefits of science and technology to resource-limited communities has been a driving force behind CAST research for decades. The team has also developed low-cost infant incubators and a suitcase-sized device to make medicine on-demand. 

For now, the sensor operates by analyzing droplets of water added to its central well. Going forward, the team would like to create a sensor that could be submerged in the water and report continuous measurements.  

They are already working with the Maryland company NanoForge Systems to commercialize the new nitrate sensor. 

"Translating science into innovative products that can help people is what really excites me about this work," Kadolkar says.

Kadolkar shows a sensor the team tested in the field by measuring nitrate levels in Baltimore-area streams. (Photo courtesy of Kadolkar)