By Satish Misra, MD and Cory Schultz
The concept of smartphones as diagnostic tools, through the use of peripheral devices, is certainly not new. Ideas for devices which diagnose cancer and infectious diseases have already moved into the development phase. But two Korean researchers are now making a bold statement – get rid of the peripheral and just use the smartphone.
The two researchers propose that the touchscreen of a smartphone can do a lot more than enable a user to throw angry birds at some pigs. In fact, they point out that the screen is capable of detecting extraordinarily small differences in capacitance and its that capability which can be leveraged to diagnose everything from influenza to salmonella.
Hyun Gyu Park and Byoung Yeon Won at the Korea Advanced Institute for Science and Technology in Daejeon, South Korea believe that a biosample – sputum, saliva, blood, or even urine – could be applied to the screen of a smartphone for analysis. The value of the analysis though hinges on the ability to correlate differences in the capacitance of the sample with something clinically relevant. As Paul Marks of New Scientist explains,
“The idea depends on a method the pair have devised to harness the way a touchscreen senses a fingertip’s ability to store electric charge – known as its capacitance. The capacitive sensitivity of touchscreens is far higher than what is needed to sense our fingers as we play games or tap out tweets. So the pair began proof-of-concept tests to see if the touchscreens in our pockets could play a role in diagnosing our ailments. First they took three solutions containing differing concentrations of DNA from the bacteria that causes chlamydia and applied droplets from each to an iPhone-sized multitouch display. They found that the output from the screen’s array of crisscrossed touch-sensing electrodes could distinguish between the capacitances caused by each concentration using droplets of only 10 microlitres (Angewandte Chemie International Edition, DOI: 10.1002/anie201105986).”
While current touchscreens are still not able to identify individual pathogens, the touchscreen’s ability to differentiate between concentrations is a crucial first step. There do remain several challenges to overcome. First, there is the issue of interference from ambient moisture, sweat, and even residues on the screen. Additionally, there is likely to be little appetite among patients to apply biosamples to their phone.
Even if the pair could demonstrate diagnostic capability for a single disease, if they pick the right one, the value could be enormous. For example, development of a small film which reacts with components of the influenza virus in ways that generate measurable and specific capacitance changes could enable an entirely new approach to management of this public health threat. Similar tools for malaria, HIV, and other scourges could enable dramatic shifts in how we manage these diseases.