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Transparent biosensors

In Italian there is a saying: "the eyes are the mirror of the soul". And it is not just in Italian. 

The eyes are the mirror of the soul and reflect everything that seems to be hidden; and like a mirror, they also reflect the person looking into them.” (quote Paulo Coelho, Manuscript found in Accra).

Literature aside, our eyes can indeed reveal quite a bit about our health. The retinal blood vessels provide tell tale signs of a variety of diseases. Tears carry with them molecules that mirror the ones in the blood, like glucose.
Researchers at the Oregon State University have worked on creating contact lenses with sensors that can detect the presence of glucose in the tears. The problem, of course is that these sensors have to be transparent to light. It turns out that the material used in displays, indium gallium zinc oxide (IGZO), that is transparent, can also be used to create sensors. The sensor is made by placing an enzyme, glucose oxidase, in contact with a field effect transistor made with IGZO. When glucose enters in contact with the enzyme the ph of the solution changes and this affect the conductivity of the transistor providing a sign of the presence of glucose. Note that the concentration of glucose in tears is way lower than the one in blood, so the sensors in the contact lenses need to be much more sensitive than the ones used to detect glucose in blood.
The sensor developed indeed has been proven to work nicely. Interestingly, the way the sensor is made opens the door to sensing many other types of molecule, one needs to couple the transistor with the appropriate enzyme. The team has already experimented with different types of sensors, like one placed on a catheter to detect uric acid.  
According to the researchers it would be possible to include 2,000 different sensors in a patch of just one square mm on a contact lens, transforming it into a full lab on our eyes!  However, it will take over one year to have a safe contact lenses prototype that can be tested on animals, and several more before we car wear those contact lenses.

About Roberto Saracco

Roberto Saracco fell in love with technology and its implications long time ago. His background is in math and computer science. Until April 2017 he led the EIT Digital Italian Node and then was head of the Industrial Doctoral School of EIT Digital up to September 2018. Previously, up to December 2011 he was the Director of the Telecom Italia Future Centre in Venice, looking at the interplay of technology evolution, economics and society. At the turn of the century he led a World Bank-Infodev project to stimulate entrepreneurship in Latin America. He is a senior member of IEEE where he leads the Industry Advisory Board within the Future Directions Committee and co-chairs the Digital Reality Initiative. He teaches a Master course on Technology Forecasting and Market impact at the University of Trento. He has published over 100 papers in journals and magazines and 14 books.