A new method of color pixel intensity analysis to obtain an oxygen concentration is presented in this research. Until
recently, color charge coupled devices (CCDs) have rarely been used for oxygen imaging in spite of its usefulness for
analyzing the spectral content of images. The proposed new method involves extracting the red color element to enhance
oxygen-related information and eliminate distorted green color information from the color images of the sensors. A
commercial RedEyeTM oxygen sensor patch was used to verify this method. The linearity and sensitivity of oxygen
detection based on the red intensity analysis was improved to those of spectrometric measurement and total color
intensity analysis. This method also has potential applications in other luminescence sensors and simultaneous structural
and functional imaging of biological systems.
Due to the proper optical property and flexibility in the process development, an epoxy-based, high-aspect ratio
photoresist SU-8 is now attracting attention in optical sensing applications. Manipulation of the surface properties of SU-8 waveguides is critical to attach functional films such as chemically-sensitive layers. We describe a new integration
process to immobilize fluorescence molecules on SU-8 waveguide surface for application to intensity-based optical
chemical sensors. We use two polymers for this application. Spin-on, hydrophobic, photopatternable silicone is a
convenient material to contain fluorophore molecules and to pattern a photolithographically defined thin layer on the
surface of SU-8. We use fumed silica powders as an additive to uniformly disperse the fluorophores in the silicone
precursor. In general, additional processes are not critically required to promote the adhesion between the SU-8 and
silicone. The other material is polyethylene glycol diacrylate (PEGDA). Recently we demonstrated a novel photografting
method to modify the surface of SU-8 using a surface bound initiator to control its wettability. The activated surface is
then coated with a monomer precursor solution. Polymerization follows when the sample is exposed to UV irradiation,
resulting in a grafted PEGDA layer incorporating fluorophores within the hydrogel matrix. Since this method is based
the UV-based photografting reaction, it is possible to grow off photolithographically defined hydrogel patterns on the
waveguide structures. The resulting films will be viable integrated components in optical bioanalytical sensors. This is a
promising technique for integrated chemical sensors both for planar type waveguide and vertical type waveguide
chemical sensors.
We present an intelligent microfluidic system with oxidase enzyme coupled biosensors. Baseline (zero-value) drift and
sensitivity degradation are two common problems related with biosensors. In order to overcome these problems there is a
great need for integrating an on-demand, in situ self-diagnosis and self-calibration unit along with the sensor. Utilizing
the microfluidic technology, we explore the feasibility of implementing this function without any externally coupled
bulky apparatus. A microsystem including a microfluidic channel and calibration electrodes are prepared by
microfabrication techniques. A novel method of using hydrogen and oxygen bubbles generated by electrolysis of water is
used to saturate the solution with these gases in the microfluidic channel where the biosensor is placed. The hydrogen
bubble provides oxygen-depleted microenvironment to conduct a zero-value calibration procedure for the sensor. The
oxygen bubble provides high sensitivity and constant oxygen background environment to allow stable enzyme reactions
that is not limited or perturbed by the fluctuation of background oxygen in sample solutions. Commercial oxygen
sensors and pH sensors are used to confirm whether saturation or depletion of oxygen has occurred with minimum local
pH change near the sensor during the electrolytic bubble generation. The glucose data obtained from the experiments
assure that our proposed method is promising to overcome the above mentioned two problems.
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