| abstract |
(57) Abstract: A housing (41) having a lower surface (51) for attachment to a subject's skin, and a reservoir (42) and gas generation in the housing separated by a displaceable membrane (45). A liquid dosing device comprising a chamber (43). The gas generated by the electrolysis cell (44) under the control of the microprocessor (46) causes the gas generating chamber (43) to expand and the reservoir (42) to contract, thereby providing a liquid drug such as insulin for example. Is released from the reservoir via a hollow dosing needle (49) extending from the lower surface (51). Both the dosing needle (49) and the sensor needle (48) protrude from the lower surface a sufficient distance to penetrate from the epidermis into the dermis when the housing is pressed against the skin. The sensor needle (48) has an enzyme coating for detecting an analyte, such as glucose, in the subject's plasma. The dosing needle (49) is made of platinum-iridium, and the current passes between the needle (48, 49) and the potentiostat circuit (47) depending on the amount of glucose detected. A reference electrode (silver / silver chloride) (50) in contact with the subject's skin increases the accuracy of the glucose measurement. The current through the potentiostat circuit (47) is measured by a voltmeter (53), and the signal from the voltmeter (53) is amplified and transmitted to a microprocessor (46), which processes the subject's plasma. The appropriate rate of drug administration is determined based on the level of analyte detected in the drug. |