Telemetry System for non-invasive measurement of glucose in tear fluid Telemetriesystem zur nicht-invasiven Glukosemessung in der Tränenflüssigkeit

Diabetes is one of the most common diseases worldwide. In order to treat these it is essential to measure glucose concentration in the human body. This can be done via various routes. Non-invasive glucose measurements have several advantages over conventional methods. In this work an enzymatic reaction is used to measure amperometric the glucose level in tear fluid with a miniaturized electrochemical cell. The miniaturized system consists of a coil made of six wires and is about 15 mm long and 1,5 mm in diameter. Three of these wires are used as electrodes. Working and counter electrode are made of stainless steel coated with Ag/AgCl. The reference electrode is made of Pt/Ir. The other three wires of the coil are made of insulated stainless steel. These are used for stability of the coil and as antennas for wireless communication with a reader unit. The processing of the measured data takes place on a CMOS Potentiostat while the transmission is done by a transponder ASIC. Because of the coil shape and the use of a flexible substrate the entire structure is flexible. Thus the system can be optimally adapted to the curvature of the eye during it is placed in the lower eyelid. The transmission of measurement data is achieved by magnetic coupling. Measurements of the glucose concentration in tear fluid show a time delayed correlation to the one in blood an offset of time.