Development of a Pneumatically Controllable Microdroplet Generator with Electrical Sensing

Microfluidic droplet generation is popular in lab-on-a-chip based biochemical analysis because it can provide precise and high throughput fluids in the form of small droplets. This thesis presents a T-junction microdroplet generator with pneumatic actuation for regulating droplet size and a capacitance-based sensor with real-time sensing capability for characterizing droplet composition and size. The multi-layer device developed in this thesis is compatible with rapid manufacturing using a desktop-based laser cutter to fabricate the fluidic and pneumatic layers. A finite element based numerical model was developed to predict the best operating and geometric parameters for droplet generation. It was revealed that the model could generate monodisperse droplets with a capillary number of 0.0007 for an aspect ratio of 1.11:1 and that the electrode width to droplet size ratio of 1:0.95 was the best size for sensing droplet movement. The results with pneumatic control showed working pneumatic pressure of up to 0.4 MPa is achievable, resulting in a 38% reduction in droplet size compared to a reference droplet. The continuous fluid used in the model was 0.1 ml/min, whereas the conventional method was 0.19 ml/min, resulting in a 38 percent reduction in droplet size. The droplet size decreased by 9.7 percent as the pressure inside the pneumatic chamber is increased by 0.1 MPa. As a result of this reduction, the capacitance value sensed decreases by 4.7 percent when a droplet (dispersed material) is fully positioned between electrodes, whereas it increases by 2.0 percent when only continuous fluid is present. Similarly, in material characterization, when the dispersed material was changed, the variation in capacitance for a droplet movement was observed to change. The multi-layer droplet generation, with simple and simultaneous sensing as well as regulation capability presented in this thesis, can be useful for the development of precision droplet generators with closed-loop control

Development of a Novel Microwave Sensing System for Lab on a Chip Applications

Microwave technology presents tremendous potential as a remote-sensing technology for a wide range of applications spanning from life science research to food industries, pharmaceutical research, and new material discoveries. Integration of microwave sensing with microfluidics for sample processing makes it an ideal choice for point of care applications highly demanded in resourcelimited areas. The vast majority of the existing microwave sensors are manufactured using sophisticated soft lithography technology which has largely limited its development and applications. There is a large demand for developing new fabrication approaches for the feasibility of mass production at a reasonable cost. In this thesis, a new, yet simple method is developed to fabricate split ring resonator (SRR) based microwave sensors. A simple RLC model is used to characterize the resonant frequency of the SRR, and the equations for calculating the RLC’s resonant frequency is modified to predict the SRR’s resonant frequency base on its geometry. The design is also validated by comparing the simulation results obtained using the commercial software HFSS, and measurements from a real SRR developed sensor. The double ring structure was fabricated onto a printed circuit board by using the industrial photolithograph method. Coating with PDMS and epoxy layer as the passivation layer was tested and compared. Two testing approaches using the SRR sensor developed in this thesis are implemented in this thesis. Their performance for real-time sensing is characterized by applying it to differentiate chemical diary samples and other chemical solutions. In the dipping mode, the sensor is dipped in the material under test (MUT), and in the microfluidic channel mode, the sensor is integrated with a microchannel. The MUT is characterized by analyzing the spectrum data of the reflection coefficient as the function of frequencies. Experimental results indicate that this sensor is capable of differentiating various liquid samples such as DI water, ethanol, isopropanol, oil and salt solutions. Linear relationships between the resonant frequency and the concentrations of chemical composites are also observed in ethanol solutions (0-90%), and salt solutions (NaCl). This sensor is also used to differentiate various milk samples and milk dilutions and it is capable of distinguishing milks with different fat percentages and protein contents. A fully customized vector network analyzer (VNA) is also developed. The circuit structure is designed by referring the existing customized VNAs that were implemented in previous work by iv other lab colleagues. Modifications are made including replacement of the microwave source, using Arduino platform to perform controlling and data acquisition, addition of a harmonic filtering device, and development of a calibration algorithm. The device is validated by comparing its measuring result with a commercial VNA. The customized VNA is able to output a similar spectrum pattern as the commercial VNA, but with slightly shift of the peak frequency

Development of a compact wireless SAW Pirani vacuum microsensor with extended range and sensitivity

Vakuumsensoren haben nach wie vor einen begrenzten Messbereich und erfordern eine aufwendige Verkabelung sowie eine komplexe Integration in Vakuumkammern. Ein kompakter Sensor, der in der Lage ist, den Erfassungsbereich zwischen Hochvakuum und Atmosphärendruck zu erweitern und dabei drahtlos zu arbeiten, ist äußerst wünschenswert. Der Schwerpunkt dieser Arbeit liegt auf dem Entwurf, der Simulation, der Herstellung und der experimentellen Validierung eines drahtlosen kompakten Vakuum-Mikrosensors mit erweiterter Reichweite und Empfindlichkeit. Zunächst wurde ein neuer Sensor unter Verwendung vorhandener und neu entwickelter Komponenten entworfen. Zweitens wurden die Sensorkomponenten simuliert, um ihre Parameter zu optimieren. Drittens wurde ein Prototyp unter Verwendung der verfügbaren Mikrobearbeitungs- und Halbleitertechnologien hergestellt und montiert. Viertens wurde der Prototyp unter Umgebungs- und Vakuumbedingungen charakterisiert, um seine Leistungen zu validieren. Für das Wandlerprinzip wurden zwei Techniken kombiniert, nämlich Pirani-Sensorik und akustische Oberflächenwellen. Das Design der Sensorkomponenten bestand aus vier Einheiten: Sensoreinheit, Heizeinheit, Abfrageeinheit und Gehäuse. Alle Einheiten wurden in einen kompakten Würfel eingebaut. Einige Komponenten wurden neu entwickelt, während andere gekauft, modifiziert und dann miteinander verbunden wurden. Die Sensoreinheit besteht aus einem neuen Chip mit verbesserter Sensorleistung dank eines optimierten Verhältnisses von Oberfläche zu Volumen. Die Heizeinheit wurde aus zwei induktiv gekoppelten Spulen und der zugehörigen Konditionierungselektronik zusammengesetzt. Die Abfrageeinheit wurde mit einer Mikro-Patch-Antenne hergestellt. Ein würfelförmiges Polymergehäuse wurde entwickelt, um alle Komponenten in einer Vakuumkammer unterzubringen. Zweitens wurde die Simulation des Verhaltens der Sensorkomponenten behandelt. Die für die Druckmessung verantwortliche Wärmeübertragung des Sensorchips wurde vom Hochvakuum bis zum Atmosphärendruck untersucht, um seine Abmessungen zu optimieren. Die Verwendung eines hängenden Lithium-Niobat-Chips mit Y-Z-Schnitt und einem TCF von 94 ppm/K führte zu einer verbesserten Leistung in einem Messbereich zwischen \num{d-4}~Pa und \num{e5}~Pa. Die elektronische Kopplung der Heizspulen wurde ebenfalls simuliert, um die Leistungsübertragung und den Kopplungsabstand zu optimieren. Der dritte Teil betrifft die Herstellungs- und Montageschritte des Prototyps unter Verwendung der verfügbaren Halbleitertechnologien und -ausrüstung. Ein SAW Chip wurde mit einer 100~nm dicken Goldschicht an der Unterseite gesputtert, um den Heizwiderstand zu bilden, und mit Hilfe von Drahtbonding elektrisch mit dem Rest des Sensors verbunden. Es wurde eine Leiterplatte vorbereitet, die die Heiz- und Sensoreinheit enthält. Ein kubisches Gehäusewurde aus PTFE hergestellt. Viertens wurden die Sensorkomponenten zunächst separat charakterisiert, um ihre Leistungen zu überprüfen, und dann zusammen unter Umgebungsbedingungen. Später wurde der Sensor im Vakuum integriert, und es wurde ein druckabhängiges Verhalten des Sensorchips beobachtet. Die Relevanz eines drahtlosen Übertragungsverfahrens wurde den herkömmlichen drahtgebundenen Methoden gegenübergestellt. Die Ergebnisse der experimentellen Arbeiten außerhalb und innerhalb des Vakuums zeigten die Machbarkeit und Relevanz des neuen Konzepts

Development of the integration of microwave technology with microfluidic systems for sensing and heating

Microfluidics-based Lab-on-a-Chip platforms have drawn ever-increasing attention from both academy and industry due to their advantages for dealing with small volume of fluids and for integrating multiple processes into one platform. These advantages are the direct benefits of miniaturization which also brings challenges, especially in sensing and heating. The challenges are augmented in the context of droplet microfluidics because of their fast motion, curved interface and reduced volume (i.e. pico- to nano-liter). Droplet microfluidics utilizes water-in-oil or oil-in-water droplets that can be generated in microchannel networks at kHz rates as mobilized test tubes. It presents tremendous potential to serve as a tool for high throughput analysis that are in high demand in many areas such as material synthesis, life science research, pharmaceutical industry and environmental monitoring. Many applications require temperature control and both fundamental and applied research need droplet sensing to assist in understanding droplet motion and developing techniques for manipulating droplets. Microwave sensing offers unique advantages by differentiating materials based on their electrical properties at high speeds. Moreover, it enables simultaneous heating of individual droplets. Previous studies demonstrated the potential of microwave resonator for point of care (POC) applications and for simultaneous sensing and heating. However, neither of them has yet be fully realized. In addition to the technical challenges such as the use of bulky and expensive vector network analyzer (VNA) for sensing that limits the potential for POC applications, fundamental understanding of microwave heating and its coupling with droplet microfluidics is lacking. This thesis is designed to fill the gap with the ultimate goal of enhancing droplet microfluidics as an enabling tool for a wide range of applications by realizing the full potential of microwave sensing and heating. With the goal of maximizing the capacity of droplet microfluidics serving as an enabling tool for many applications, this thesis focuses on exploring microwave sensing and heating for droplet microfluidics. The thesis started with the investigation of the coupling between microwave heating and droplet motion to shine light on the mechanism of microwave heating induced droplet mixing. Followed the improved understanding of microwave heating, on-demand droplet generation via microwave heating was explored and demonstrated. To realize simultaneous sensing and heating which is powerful for droplet microfluidics, two resonators need to be considered and the primary concern for two resonators in a single microfluidic chip is the crosstalk between the two resonators. The third chapter was designed to investigate the fundamental challenges of integrating two resonators within a typical microfluidic device footprint. Finally, a POC application of microwave sensing is demonstrated for real time detecting lead in drinking water system which has been one of the crisis raised recently

Surface and Structural Engineering of Ionovoltaic Device for Energy Harvesting and Sensing Applications

학위논문 (박사)-- 서울대학교 대학원 : 융합과학기술대학원 융합과학부(나노융합전공), 2019. 2. 김연상.최근 Ionovoltaic 변환기라 명명된, 액체와 고체 표면의 접촉에서 전기가 발생하는 현상을 이용한 전기 변환 장치에 관한 연구가 많은 관심을 받고 있다. 신재생 친환경 에너지 발전 장치에 관한 필요성이 커지고 수용액 기반에서 능동적으로 작동 할 수 있는 다양한 센서에 관한 요구가 꾸준히 증가하는 가운데, ionovoltaic 소자는 이러한 요구를 충족 시킬 수 있는 능동형 장치로서 주목받고 있다. 하지만 ionovoltaic 소자를 에너지 발전 소자와 능동적 센서로 실질적 활용과 적용을 하기에는 출력 에너지 밀도가 낮고, 공정이 복잡하다. 더욱이 충분히 밝혀지지 않은 소자의 구동 원리와 소자의 획일적인 재료 및 구조 연구는 소자의 다양한 활용 발전을 가로막고 있다. 여기, 이 학위 연구는 ionovoltaic 장치의 (i) 표면 개질과 (ii) 구조 공정 개선, 두 가지 연구를 통해 계면에서의 이온거동에 의한 전기 발생 현상을 보다 명확히 밝히며 이를 통해 센서와 에너지 수확장치로서의 폭 넓은 활용을 다룬다. 첫째, 기존에 사용되었던 불소 기반의 획일적인 소수성 표면 물질을 벗어나 표면 개질을 통한 새로운 전기적 특성을 갖는 소수성 표면 공정을 ionovoltaic 전환 소자에 적용하여 액체와 고체 계면에서의 이온 거동을 이용한 다양한 센싱 어플리케이션에 적용하였다. 음의 표면전위를 갖는 소수성 표면의 변환기와 양의 표면전위를 갖는 소수성 표면의 변환기를 개발하여 비교 분석 하였으며 이온 거동에 의한 전기신호 반전 효과를 처음으로 확인 하였다. 뿐만 아니라, 산, 염기에 민감한 표면 특성을 활용하여 pH 센서 및 요소(urea) 센서로서 활용성을 검증하였다. 둘째, 기존에 사용되었던 2 전극 시스템의 획일적인 소자의 구조를 탈피하고 새로운 형태의 소자 구조 공정을 통해 액체와 고체 표면의 접촉이 전기신호로 변환되는 원리 파악과 센싱 및 에너지 수확장치로서의 적용 가능성을 제시하였다. 소자의 전체적인 구조 공정과 전극 연구를 통해서 전기 신호의 발생 지속시간을 조절 할 수 있었으며 에너지밀도를 높일 수 있었다. 뿐만 아니라 투명하면서도 전기를 발생시킬 수 있는 고저항 ITO 전극 개발을 통해 건물이나 자동차의 외관 및 창문에 활용 될 수 있는 에너지 수확장치를 개발하여 ionovoltaic 장치의 폭넓은 활용가능성을 제시하였다.Recently, there has been a lot of interest in the research on the transducers using the phenomenon of electricity generation in the contact between the liquid and solid surface. In particular, transducers using EDL (electrical double layer) modulations, which named as ionovoltaic transducers are attracting attention because of their advantages in eco-friendly, simple drive systems and self-powered characteristics. With the growing need for renewable and eco-friendly energy generation devices and the increasing demand for a variety of sensors that can actively operate on an aqueous solution basis, the ionovoltaic devices can be utilized as a great candidate to solve these demands. However, the output energy density is low and the fabrication process is complicated to make practical use of the ionovoltaic device as the energy generating device and the active sensors. Moreover, the driving principle of the device which is not sufficiently clarified and the similar materials and structures research of the device are obstructing the various utilization development of the device. In this thesis clarifies the generation of electricity by the ionic behavior at the interface through two issues: (i) surface modification of ionovoltaic device and (ii) improvement of ionovoltaic device performance through the structural engineering. In addition, this study covers a wide range of applications as sensors and energy harvesting devices. First, applying a hydrophobic surface modification with novel electrical properties to the ionovoltaic device by engineering the hydrophobic layer, and applying it to various sensing applications using ionic behaviors at the solid-liquid interface. The ionovoltaic transducers with a negative / a positive surface potentials were developed and compared, and the effect of reversing the electrical signal by ionic behavior was confirmed for the first time. In addition, the modified ionovoltaic transducer has proven its applicability as a pH sensor and urea (bio)sensor by utilizing a pH-sensitive surface. Secondly, we identified the principle that the contact between the liquid and the solid surface is converted into the electric signal through the new type of device through the structural engineering and to apply it as the sensing and energy harvesting device. In addition, through electrode studies, we have understood the conduction mechanism and investigated the effect of resistance on ionovoltaic device performance. Through the whole structural engineering of the ionovoltaic device and the electrode modification, it was possible to control the generation time of the electric signal and to increase the energy density. Moreover, we have developed an energy harvester that can be used for the exterior and windows of buildings or automobiles through the development of high-resistance ITO mono- electrodes using the sputtering system, suggesting wide application possibilities of ionovoltaic devices.List of figures 9 Chapter 1 Introduction 16 1.1 Overview 16 1.2 Reference 19 Chapter 2 Fundamental and Literature Review 20 2.1 Working mechanism of ionovoltaic device 20 2.2 Components of ionovoltaic device 23 2.2.1. Surface of ionovoltaic devices 26 2.2.2. Structure of Ionovoltaic devices 29 2.4 References 31 Chapter 3 Surface Modification of Ionovoltaic Device and Applications 32 3.1 Introduction 32 3.2 Fabrication of pH-sensitive surface 34 3.3 Device performances and working mechanism 37 3.4 Application of ionovoltaic device as a pH sensor 48 3.4.1 pH sensing device performance and working principle 48 3.5 Application of ionovoltaic device as a urea detector 54 3.5.1 Fabrication method 55 3.5.2 Device performance and working mechanism 58 3.5.3 Possibility of ionovoltaic urea detector as a biosensor 72 3.6 Conclusion 74 3.6 Experimental details 76 3.7. Reference 79 Chapter 4 Structural Engineering of Ionovoltaic Device and Applications 85 4.1 Introduction 85 4.2 Fluidic ionovoltaic device 85 4.2.1 Fabrication method and device performance 87 4.2.2 Application of ionovoltaic device as an air-slug sensor 96 4.3 ITO mono-electrode based ionovoltaic device 100 4.3.1 Fabrication of ITO mono-electrode and ionovoltaic device 103 4.3.2 Influence of sputtering parameters on a characteristics of ITO mono-electrode based ionovoltaic device. 106 4.3.3 Application and advantages of ITO based ionovoltaic device 116 4.4 Conclusion 118 4.5 Experimental details 119 4.6 References 122 Chapter. 5 Conclusion 129 List of publications 132 요 약 (국문초록) 134Docto

Development of Microwave/Droplet-Microfluidics Integrated Heating and Sensing Platforms for Biomedical and Pharmaceutical Lab-on-a-Chip Applications

Interest in Lab-on-a-chip and droplet-based microfluidics has grown recently because of their promise to facilitate a broad range of scientific research and biological/chemical processes such as cell analysis, DNA hybridization, drug screening and diagnostics. Major advantages of droplet-based microfluidics versus traditional bioassays include its capability to provide highly monodispersed, well-isolated environment for reactions with magnitude higher throughput (i.e. kHz) than traditional high throughput systems, as well as its low reagent consumption and elimination of cross contamination. Major functions required for deploying droplet microfluidics include droplet generation, merging, sorting, splitting, trapping, sensing, heating and storing, among which sensing and heating of individual droplets remain great challenges and demand for new technology. This thesis focuses on developing novel microwave technology that can be integrated with droplet-based microfluidic platforms to address these challenges. This thesis is structured to consider both fundamentals and applications of microwave sensing and heating of individual droplets very broadly. It starts with developing a label-free, sensitive, inexpensive and portable microwave system that can be integrated with microfluidic platforms for detection and content sensing of individual droplets for high-throughput applications. This is, indeed, important since most droplet-based microfluidic studies rely on optical imaging, which usually requires expensive and bulky systems, the use of fluorescent dyes and exhaustive post-imaging analysis. Although electrical detection systems can be made inexpensive, label-free and portable, most of them usually work at low frequencies, which limits their applications to fast moving droplets. The developed microwave circuitry is inexpensive due to the use of off-the-shelf components, and is compact and capable of detecting droplet presence at kHz rates and droplet content sensing of biological materials such as penicillin antibiotic, fetal bovine serum solutions and variations in a drug compound concentration (e.g., for Alzheimer’s Disease). Subsequently, a numerical model is developed based on which parametrical analysis is performed in order to understand better the sensing and heating performance of the integrated platform. Specifically, the microwave resonator structure, which operates at GHz frequency affecting sensing performance significantly, and the dielectric properties of the microfluidic chip components that highly influence the internal electromagnetic field and energy dissipation, are studied systematically for their effects on sensing and heating efficiency. The results provide important findings and understanding on the integrated device operation and optimization strategies. Next, driven by the need for on-demand, rapid mixing inside droplets in many applications such as biochemical assays and material synthesis, a microwave-based microfluidic mixer is developed. Rapid mixing in droplets can be achieved within each half of the droplet, but not the entire droplet. Cross-center mixing is still dominated by diffusion. In this project, the microwave mixer, which works essentially as a resonator, accumulates an intensive, nonuniform electromagnetic field into a spiral capacitive gap (around 200 μm) over which a microchannel is aligned. As droplets pass by the gap region, they receive spatially non-uniform energy and thus have non-uniform temperature distribution, which induces non-uniform Marangoni stresses on the interface and thus three-dimensional (3D) chaotic motion inside the droplet. The 3D chaotic motion inside the droplet enables fast mixing within the entire droplet. The mixing efficiency is evaluated by varying the applied power, droplet length and fluid viscosity. In spite of various existing thermometry methods for microfluidic applications, it remains challenging to measure the temperature of individual fast moving droplets because they do not allow sufficient exposure time demanded by both fluorescence based techniques and resistance temperature detectors. A microwave thermometry method is thus developed here, which relies on correlating fluid temperature with the resonance frequency and the reflection coefficient of the microwave sensor, based on the fact that liquid permittivity is a function of temperature. It is demonstrated that the sensor can detect the temperature of individual droplets with ±1.2 °C accuracy. At the final part of the thesis, I extend my platform technology further to applications such as disease diagnosis and drug delivery. First, I develop a microfluidic chip for controlled synthesis of poly (acrylamide-co-sodium acrylate) copolymer hydrogel microparticles whose structure varies with temperature, chemical composition and pH values. This project investigates the effects of monomer compositions and cross-linker concentrations on the swelling ratio. The results are validated through the Fourier transform infrared spectra (FTIR), SEM and swelling test. Second, a preliminary study on DNA hybridization detection through microwave sensors for disease diagnosis is conducted. Gold sensors and biological protocols of DNA hybridization event are explored. The event of DNA hybridization with the immobilized thiol-modified ss-DNA oligos and complimentary DNA (c-DNA) are monitored. The results are promising, and suggests that microwave integrated Lab-on-a-chip platforms can perform disease diagnosis studies

Novel miniaturised and highly versatile biomechatronic platforms for the characterisation of melanoma cancer cells

There has been an increasing demand to acquire highly sensitive devices that are able to detect and characterize cancer at a single cell level. Despite the moderate progress in this field, the majority of approaches failed to reach cell characterization with optimal sensitivity and specificity. Accordingly, in this study highly sensitive, miniaturized-biomechatronic platforms have been modeled, designed, optimized, microfabricated, and characterized, which can be used to detect and differentiate various stages of melanoma cancer cells. The melanoma cell has been chosen as a legitimate cancer model, where electrophysiological and analytical expression of cell-membrane potential have been derived, and cellular contractile force has been obtained through a correlation with micromechanical deflections of a miniaturized cantilever beam. The main objectives of this study are in fourfold: (1) to quantify cell-membrane potential, (2) correlate cellular biophysics to respective contractile force of a cell in association with various stages of the melanoma disease, (3) examine the morphology of each stage of melanoma, and (4) arrive at a relation that would interrelate stage of the disease, cellular contractile force, and cellular electrophysiology based on conducted in vitro experimental findings. Various well-characterized melanoma cancer cell lines, with varying degrees of genetic complexities have been utilized. In this study, two-miniaturized-versatile-biomechatronic platforms have been developed to extract the electrophysiology of cells, and cellular mechanics (mechanobiology). The former platform consists of a microfluidic module, and stimulating and recording array of electrodes patterned on a glass substrate, forming multi-electrode arrays (MEAs), whereas the latter system consists of a microcantilever-based biosensor with an embedded Wheatstone bridge, and a microfluidic module. Furthermore, in support of this work main objectives, dedicated microelectronics together with customized software have been attained to functionalize, and empower the two-biomechatronic platforms. The bio-mechatronic system performance has been tested throughout a sufficient number of in vitro experiments.Open Acces

Biosensors for Diagnosis and Monitoring

Biosensor technologies have received a great amount of interest in recent decades, and this has especially been the case in recent years due to the health alert caused by the COVID-19 pandemic. The sensor platform market has grown in recent decades, and the COVID-19 outbreak has led to an increase in the demand for home diagnostics and point-of-care systems. With the evolution of biosensor technology towards portable platforms with a lower cost on-site analysis and a rapid selective and sensitive response, a larger market has opened up for this technology. The evolution of biosensor systems has the opportunity to change classic analysis towards real-time and in situ detection systems, with platforms such as point-of-care and wearables as well as implantable sensors to decentralize chemical and biological analysis, thus reducing industrial and medical costs. This book is dedicated to all the research related to biosensor technologies. Reviews, perspective articles, and research articles in different biosensing areas such as wearable sensors, point-of-care platforms, and pathogen detection for biomedical applications as well as environmental monitoring will introduce the reader to these relevant topics. This book is aimed at scientists and professionals working in the field of biosensors and also provides essential knowledge for students who want to enter the field

Microfabricated Optofluidic Ring Resonators for Sensitive, High-Speed Detection of Volatile Organic Compounds

The development of microfabricated sensors and sensor arrays for volatile organic compounds (VOC) and their evaluation as detectors in micro-scale gas chromatographic (μGC) instrumentation are described. Initial efforts explored the discrimination of VOCs with arrays of chemiresistors (CR) employing interface layers of thiolate-monolayer-protected gold nanoparticles (MPNs) or tin-oxide nanowires (NWs). The response diversity of several possible MPN-CR arrays was found to exceed that of the NW-CR array, and was not enhanced by combining the former with the latter. The next study demonstrated that the response diversity of MPN-CR arrays could be enhanced moderately by combining them with arrays of mass-sensitive MPN-coated thickness-shear-mode resonators. However, the analysis of binary VOC mixtures was not satisfactory even with the best of these multi-transducer arrays. A new type of optical vapor sensor was then created: the microfabricated optofluidic ring resonator (μOFRR). This sensor combines vapor sensing and fluidic transport functions in a monolithic microstructure comprising a hollow, vertical SiOx cylinder (250 μm i.d.) with a central quasi-toroidal mode-confinement section, grown and partially released from a Si substrate. It also integrates fluidic-interconnection and fiber-optic probe alignment features. High-Q whispering gallery modes (WGM) generated with a tunable near-IR laser exhibited shifts in resonant wavelength, λWGM, from polymer swelling and refractive index changes as vapors reversibly partitioned into the thin sorptive-polymer film lining the cylinder. Remarkably high sensitivity and rapid responses were obtained with this μOFRR sensor installed downstream from a single μGC separation column and a two-dimensional μGC subsystem. Since MPN films exhibit localized surface plasmon resonance (LSPR) they also have the potential to serve as interface layers in optical sensor arrays. Indeed, it was shown that VOC discrimination was possible by probing an MPN film at just two wavelengths flanking its LSPR absorbance maximum in a custom-built reflectance measurement system. In a first attempt to adapt multi-wavelength plasmonic sensing to the μOFRR platform, measured shifts in λWGM from an MPN coated μOFRR sensor were shown to be proportional to concentration for several VOCs. Results suggest that arrays of MPN-coated μOFRR sensors show great promise as detectors in single- and multi-dimensional μGC systems.PHDApplied PhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111492/1/keesc_1.pd