Development of Wearable Medical Device for Bio-MEMS

Biomedical Micro Electro Mechanical Systems (Bio-MEMS) have been applied to the development of a variety of health care related products including health Monitoring Systems (HMS) and Drug Delivery Systems (DDS). We focus on research to develop the new type compact medical device used for blood sugar control. The new type compact medical device comprises (1) a micropump system to extract blood using a pressure change occurred by electrolysis, (2) a platinum (Pt) electrode as a blood sugar sensor immobilized Glucose Oxidase (GOx) and attached to the gate electrode of Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) to detect the amount of glucose in extracted blood, and (3) a micropump system to inject insulin using a pressure change occurred by electrolysis. GOx was immobilized on a self assemble spacer combined with a Pt electrode by the cross-link method using BSA as an additional bonding material. The device can extract blood in a few microliter through a painless microneedle with the micropump, which used the pressure change occurred by electrolysis. The liquid extraction ability of the micropump system through a microneedle, which is 3.8 mm in length and 100 μm in internal diameter, was measured. The wearable medical device with using the micropump controlled by electrolysis could extract human blood at the speed of 0.15 μl/sec. If the wearable medical device extracts human blood for 6 seconds, it is enough human blood volume to measure a glucose level, compared to the amount of commercial based glucose level monitor. The electrode embedded in the blood extraction device chamber could detect electrons generated by the hydrolysis of hydrogen peroxide produced by the reaction between GOx and glucose in extracted blood of a few microliter, using the constant electric current measurement system of the MOSFET type hybrid glucose sensor. The output voltage for the glucose diluted in the chamber was increased lineally with increase of the glucose concentration. The compact medical device with the air bubble that occurred by electrolysis could inject insulin at the speed of 6.15μl/sec.