Researchers suggest that smartphone touchscreens can be used as a substance sensor that can effectively sense the presence of different contaminants.
Smartphone touch screens are generally made up of a grid of electrodes. When a finger disrupts the local electric field of these electrodes, the phone interprets the signal. For sensing purposes, the computational power of the smartphone has been earlier used along with the camera. Researchers recently suggested that the smartphone touchscreens could also be used as a powerful sensor, without the need for any modifications.
Researchers from the University of Cambridge have demonstrated how a typical touchscreen could be used to identify common ionic contaminants in soil or drinking water. According to the researchers, the sensitivity of the touchscreen sensors is comparable to that of typical lab-based equipment. The work is reported in the journal Sensors and Actuators B.
“We wanted to know if we could interact with the technology in a different way, 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 initially started with simulations and later, they validated their simulations on a standalone touchscreen. The researchers pipetted different substances onto the screen and measured the change in capacitance using the testing software. Theory explained that the ions in the fluids all interact with the screen’s electric fields differently depending on the concentration of ions and their charge.
“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 is a starting point for broader exploration of the use of touchscreen sensing in mobile technologies and the creation of tools that are accessible to everyone, allowing rapid measurements and communication of data,” said Hall.
The researchers believe that their proof of concept could one day be expanded for a wide range of sensing applications, including for biosensing or medical diagnostics, right from the phone in your pocket.