A Contamination-Detection Touchscreen
Researchers have shown how a touchscreen could be used as a sensor to detect soil or water contamination by dropping samples on the display.
For the first time, researchers at the University of Cambridge unveiled that an ordinary touchscreen can identify specific contaminations in soil or drinking water. This process occurs after placing liquid samples on top of the screen. More impressively, the touchscreen’s sensor sensitivity is similar to typical lab-based equipment, allowing it to be utilized in a low-resource setting. The team says that this technology could have biosensing or medical diagnostic applications.
Other teams attempted to take advantage of a smartphone’s computational power for sensing applications. However, these relied on the camera or peripheral devices or needed significant screen modifications. “We wanted to know if we could interact with the technology differently, without having to fundamentally change the screen,” said Dr. Ronan Daly from Cambridge’s Institute of Manufacturing, who co-led the research. “Instead of interpreting a signal from your finger, what if we could get a touchscreen to read electrolytes since these ions also interact with the electric fields?”
The researchers ran computer simulations and validated them with a stripped-down, standalone touchscreen. Then, they pipetted various liquids onto the screen to take measurements of capacitance changes and documented each droplet’s measurement using the touchscreen testing software. Depending on the ions’ concentration and their charge, ions in the fluids interacted with the screen’s electric fields differently.
“Our simulations showed where the electric field interacts with the fluid droplet. In our experiments, we then found a linear trend for a range of electrolytes measured on the touchscreen,” said first author Sebastian Horstmann, a Ph.D. candidate at IfM. “The sensor saturates at an anion concentration of around 500 micromolar, which can be correlated to the conductivity measured alongside. This detection window is ideal to sense ionic contamination in drinking water.”
This technology could detect a common contaminant: arsenic contamination in drinking water. This is usually screened by water systems and filtered out before reaching the tap. Some countries don’t have water treatment plants, which is a huge problem.
The team also says that a smartphone and tablets’ electrode design can undergo modifications to increase sensitivity on a screen’s certain area. Then, the phone’s software communicates with that part to distribute the best electric field and increase its sensitivity for the intended ion.
With its ion detection capabilities, the researchers wants to continue developing the technology so that it can detect various molecules. Doing so would pave the way toward potential health applications. “For example, if we could get the sensitivity to a point where the touchscreen could detect heavy metals, it could be used to test for things like lead in drinking water. We also hope in the future to deliver sensors for home health monitoring,” said Daly.