Study on the "intelligent mosquito"

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In order to minimize pain accompanying blood sampling, a miniaturized analysis system that imitates a mosquito was developed. The system consisted of a micro glucose sensor, a sampling mechanism, and a microscopic needle. A copolymerized gel composed of poly(N-isopropylacrylamide) and acrylic acid was used to construct a mechanism that withdrew sample solution slowly. A gel of 11mm×11mm×4mm was used and a volume change was caused by changing the temperature, changing the temperature and pH, and using a pH change caused by the enzymatic reaction of glucose oxidase. With the enzyme-loaded gel, the gel shrank most slowly spanning nearly 10h. The volume change of the gel could be converted into a pressure change in a flow channel with the help of a silicone rubber diaphragm. As a result, the mechanism could withdraw an external solution into the flow channel. The glucose sensor consisted of a platinum working electrode covered with a Nafion membrane and a polyHEMA membrane which worked as a perm-selective membrane and a diffusion-limiting membrane, respectively. An enzyme-immobilized layer was formed between the two layers. The linear range of the calibration curve was expanded up to 30mM and the responses to L-ascorbic acid and uric acid could be reduced to about 1% of that to glucose. An external glucose standard solution could be introduced into the system autonomously by switching on the gel volume change. When the glucose concentration of an external solution flowed in a silicone tube was changed arbitrarily and the solution was sampled through the microscopic needle, the glucose concentration could be monitored continuously using an on-chip micro glucose sensor.