Development of non-invasive optical transcutaneous pCO2 gas sensor and analytic equipment

In this paper, we studied the development of an optical transcutancous pCO(2) gas sensor and analyzer using a non-invasive method. The basic principle of the pCO(2) measurement adapted Beer-Lambert's law and the embodied system using the NDIR (Non Dispersive Infrared) method. The CO(2) gas reacted with a 4.3 gm wavelength, so we selected this wavelength by an optical filter, and used energy decrease by molecule oscillations. We measured the CO(2) concentration using the MFC (Mass Flow Controller) in basic steps instead of the pCO(2) gas that can collect by inflicting heat on the outer skin. This measuring system consisted of an IR lamp, an optical filter, an optical reaction chamber, a pyroelectric sensor and a signal process part. We minimized the size of optical reaction chamber which took up the smallest volume, in order to make the portable sensor. We made an optical reaction chamber with a Si wafer using MEMS technology and it was shortened to I mm. We carried out an experiment in photoreaction length's variation from I mm to 10 mm. And we confirmed the linear graph that variation of CO(2) concentration from 1,000 ppm (parts per million) to 100,000 ppm at 1 mm photoreaction length. The response time of this system was within 2 seconds, which is fairly fast.