Comparative investigation using GaAs(950nm), GaAIAs (940nm) and InGaAsP (1450nm) sensors for development of non-invasive optical blood glucose measurement system

Previously, many researches had been done on non-invasive using near-infrared sensing. Sia [1] had investigated near-infrared sensing using signal penetrating finger method. However, by using finger penetration, there are no results obtained. He only obtained signal using glucose concentration. Therefore the objectives of this research are to investigate the performance of three different wavelength of sensors; infrared 940nm and 950nm and also near-infrared 1450nm. Sensor that gave the best output had been chosen to design a non-invasive optical blood glucose measurement device. Generally, the overall system consists of three parts including sensor part, signal conditioning circuit, and also numerical display. The initial design tested by considering initial voltage 1.616V to 1.68V which referred to previous research by Sia [1] as the output of the sensor. Then proceed by using test tube which contains various percentage of glucose concentration. The same methods had been used to the human samples fingers instead of test tube. From the experiment, output graph of the 950nm shows more consistent pattern compared to the 940nm. 950nm also has a larger range scale for voltage which from 5.016V to 5.4633V compare to the 940nm voltage range scale which from 5.0327V to 5.4201V. Further test on human finger had been done by using 950nm infrared but the output voltages were too small. The performance of the measurement can be improved by controlling the surrounding condition and fixed the path length between transmitter and receiver. Test using test tube showed that the near infrared and infrared were capable to predict different glucose concentration. By using circuit designed, it can be seen that the voltage reading became higher compared to before meal. Therefore, it can be concluded that the circuit design functions accordingly and also the non-invasive. During human sample test, increment pattern can be seen from fasting to non-fasting condition but the main effect is- all samples have different fingers´ diameter which each of user needs to be calibrated.