Fabrication and Testing of an Osmotic Pressure Sensor for Glucose Sensing Application

This paper presents a chemical reaction-free sensor, based on the osmosis principle, fabricated to measure the change in glucose concentration levels. The sensor consists of a square cavity filled with a known concentration of glucose solution and sealed with a semi-permeable membrane. The volume inside the cavity changes in proportion to the glucose concentration outside the device and introduces the displacement in the silicon (Si) membrane on the top. The main considerations targeted for this sensor are better response time, chemical-free nature, improved lifetime and absence of any mechanical excitations. Moreover, as the size of a system plays a major role, efforts have been taken to reduce the dimension of the presented system. The designed glucose sensor is fabricated by employing a bulk micromachining technology on a SOI (silicon on insulator) substrate. This will allow batch fabrication, as well as the integration of the electronic circuit on the same substrate. The output voltage obtained is varied from −6.7 to 22.7 mV for the corresponding glucose concentrations ranging from 50 to 450 mg/dL, respectively, after a constant osmosis duration of 15 min. The response time obtained for the sensor is 40 min, and it is lesser compared to similar works based on the osmosis principle.