Single Chip Optoelectronic Nose

TITLE: Single Chip Optoelectronic Nose also with Scientific CMOS Imagers

Advisors: Sameer R Sonkusale

Researcher: Yael Zilberman, Yu Chen, Guoqing Fu, Jian Guo (Completed)




The objective of this research is to develop miniaturized (benchtop or chip-scale) optical sensors for detection of volatile organic compounds in both vapor and liquid phase. Measuring dissolved chemicals in aqueous environment is particularly challenging due to issues of long-term reliability from washout of the dyes. In one project, these sensors are expected to detect dissolved CO2, pH and ammonia for gastric cancer; the sensors will be small enough to occupy a tip of tethered endoscopy capsule and will identify regions of the stomach infected with Helicobacter Pylori. In another project, a sensor array was designed to generate a two-dimensional spatiotemporal profile of dissolved oxygen in the environment. This has tremendous applications in tissue engineering and in basic life sciences to monitor viability of cells/tissues based on oxygen consumption in real-time.



Our core principle for detection of diverse dissolved chemicals, is to utilize various indicator dyes as cross-reactive sensors embedded inside ion-exchange resin beads; the range of dyes allow us to cover variety of physical and chemical interactions between the dyes and analytes providing the necessary diversity for target identification through machine learning (similar to the operation of a mammalian olfactory sensing system). The various dyes range from those that respond to Lewis basicity (electron-pair donation, metal-ion ligation), to pH (proton acidity), to Brønsted acidity (hydrogen bonding), to local polarity, and to redox reactions. For readout we employ a unique strategy that of multispectral readout using a fiber coupled spectrometer. We are also developing a suite of CMOS scientific imagers to support the optoelectronic nose development and other optical imaging applications.. The requirements for the custom imagers are low noise, high dynamic range and the ability to extract both intensity and lifetime from the fluorophore. We achieve dynamic range using linear-log hybrid readout circuitry. Lifetime and phase measurements are achieved using circuitry for zero-crossing detection and time to digital conversion to extract fluorescence lifetimes or phase. For multi-spectral response, we employ resonant antenna-coupled photodetectors using metamaterials (results are forthcoming).



We have developed a portable optoelectronic nose for gas sensing for ambient environment using silica beads with indicator dyes loaded at the tip of optical fiber bundle array and imaged using high dynamic range CMOS camera (Analytical Chemistry 2009). Recently, we demonstrated a microfluidic optical sensor array utilizing a novel halochromic dye within resin beads held by ionic interaction thus preventing washout for detection of dissolved ammonia (NH3) and carbon dioxide (CO2) in complex background like saliva (Sensors and Actuators-B: Chemical (2 papers) 2014, Biosensors and Bioelectronics 2014). Role of elevated levels of NH3 and CO2 in saliva has been attributed to infection of H. pylori bacteria that is a risk factor for stomach cancer. Another platform for oxygen sensing was built using dyes that have an oxygen-dependent lifetime (e.g. ruthenium complex dye) and imaged using a custom CMOS fluorometer implemented in a 65nm CMOS process that employed a novel readout circuitry based on Time to Digital Converter (TDC) for sub-ns lifetime measurement. These works have resulted in more than 2 journal publications (IEEE Journal of Solid State Circuits 2012, IEEE Sensors Journal 2012), one invention disclosure and numerous conference presentations (ESSCIRC, ISCAS, Sensors, Biosensors, Hilton Head). We have also designed and fabricated a 120-dB dynamic range linear-log imager in 0.5um digital CMOS process with automatic linear to log switching based on the scene illumination. The imager was used to detect iron oxide nanoparticles in the presence of a strong background excitation (IEEE Sensors Journal 2009). We have also implemented a new class of imager inspired by the frequency selectivity and perfect absorptivity of metamaterial-based antenna elements for terahertz and far infrared detection in CMOS process. We are expecting the results on our chip soon. This will be the first ever demonstration of hyperspectral imager from visible to the far-infrared in a CMOS process.


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