Micro system for injection of insulin and monitoring of glucose concentration

To minimize the burden for diabetes care, a micro insulin injection system was developed based on an electrochemical principle. Major components of the device were a thin-film two-electrode system incorporated in a closed compartment, a silicone rubber diaphragm to separate an electrolyte solution from an insulin solution, and a reservoir for insulin. A micro needle was attached to the outlet. Hydrogen bubbles were grown on a platinum working electrode. Accompanying this change, the diaphragm was deformed and a pressure was exerted to the insulin solution in the reservoir on the other side of the diaphragm. The injection was smooth without ripples and the injection rate could be controlled by electrode potential. When the insulin solution was injected into an anesthetized rat, the decrease in the plasma glucose level (PGL) was observed depending on the dose of insulin. No substantial difference was observed compared with the case of manual injection of insulin. A glucose sensor was also developed to monitor the glucose level