In this study, an automatic blood vessel searching system (BVSS) is newly developed, which is built in the health
monitoring system (HMS) and the drug delivery system (DDS) to extract the blood, evaluates the blood sugar level and
injects the insulin for the diabetic patients. Main subjects of our BVSS development are 1) a transmittance photo imaging
of the finger by using the LED light as a near-infrared light source with peak wave length of 870 nm, and 2) an image
processing to detect the location of the center of the blood vessel cross section.
The sharp edge focus method was applied in our BVSS to detect the depth of blood vessel. We carried out
experiments by using blood vessel phantoms, which consist of an artificial cylindrical blood vessel and skin tissue,
which are made of the teflon tube and the silicone rubber. The teflon tube has the size of 0.6 mm in diameter and is filled
with the human blood. The experimental results demonstrated that the estimated depth, which is obtained by image
analysis corresponding to given depths, shows a good agreement with the real values, and consequently the availability
of our BVSS is confirmed.
We focus on the research to develop a compact Self Monitoring of Blood Glucose (SMBG). The SMBG consists of (1) a micro electrical pumping system for blood extraction, (2) a painless microneedle as same size as a female mosquito's labium and (3) a biosensor to detect and evaluate an amount of glucose in extracted blood, by using enzyme such as glucose oxidase (GOx). A gold (Au) plate immobilized GOx was used as a biosensor and attached to the gate electrode of MOSFET. GOx was immobilized on a self-assembled spacer combined with an Au electrode by the cross-link method using BSA (bovine serum albumin) as an additional bonding material. The electrode could detect electrons generated by the hydrolysis of hydrogen peroxide produced by the reaction between GOx and glucose using the constant electric current measurement system of the MOSFET type hybrid biosensor system. The system can measure the change of gate voltage. The extracting speed for whole blood using the micro electrical pumping system was about 2 μl/min. The extracted volume was sufficient to determine the glucose level in the blood; it was comparable to the volume extracted in a commercial glucose level monitor. In the functional evaluation of the biosensor system using hydrogen peroxide solution, it is shown that the averaged output voltage increases in alignment to hydrogen peroxide concentration. The linear value was shown with the averaged output voltage in corresponding hydrogen peroxide concentration with the averaged output voltage obtained from the biosensor system by glucose solution concentration. Furthermore, it is confirmed that the averaged output voltage from the biosensor system obtained by whole blood showed the same voltage in corresponding glucose solution concentration. The hybrid biosensor obtained the useful performance for the SMBG.