La mesure et le contrôle du pouls et du flux sanguin en continu sont d'importants paramètres pour l'évaluation de signes essentiels physiologiques sur la condition de santé d'un individu. Les dispositifs commerciaux existants, ainsi que les méthodes de recherche ou utilisées dans le milieu médical exigent un bon contact électrique ou optique pour obtenir cette mesure en continu. Pendant ces travaux de recherche, une méthode originale non invasive de mesure du rythme cardiaque fondée sur la perturbation localisée d'un champ magnétique au passage du flux sanguin a été développée, permettant l'acquisition des signaux à travers les vêtements, la transpiration, les salissures ou autres polluants dans l'environnement proche du capteur. Cette méthode est appelée la Signature Sanguine par Modulation Magnétique (MMSB) et les mesures ont été accomplies sur de multiples individus. Le système a été modélisé mathématiquement et simulé dans un environnement multiphysique, puis validé par l'utilisation des données expérimentales. Les résultats de mesure, en utilisant la méthode MMSB, pour le pouls et le flux sanguin ont été comparés et se trouvent bien corrélés, avec les résultats obtenus grâce à d'autres instruments. De plus, deux dispositifs ont été développés et sont en cours de commercialisation, pour des applications de vie quotidienne / Continuous pulse rate, blood pressure and blood flow monitoring are important for the assessment of physiological vital signs as these are able to provide continuous feedback on the health condition of an individual. Existing commercial, medical and research methods to continuously acquire such these physiological vital signs require good electrical or optical contact. During this research, a magnetic based sensing method, at room temperature, for blood pulse, flow and pressure is developed to achieve data acquisition through fabric, environmental contaminants and body-fluids. This method is named Modulated Magnetic Signature of Blood (MMSB) and physical measurements were conducted on multiple subjects, mathematically modelled and simulated in a multi-physics environment with verification through use of measurement data. Measurement results, using MMSB, for blood pressure and blood flow were compared, and found to be well correlated, with lifestyle device and medical research instruments respectively. In addition, two devices are developed, and are in the midst of commercialization, to support lifestyle applications

An Active Microscaffold System with Fluid Delivery and Stimulation/Recording Functionalities for Culturing 3-D Neuronal Networks Laura Elizabeth Rowe 215 Pages Directed by Dr. A. Bruno Frazier An active microscaffold system with fluid delivery and electrical stimulation/recording functionalities for 3-D neuronal culture studies is presented. The microscaffolds presented in this dissertation consist of an array of microfabricated towers with integrated microfluidic channels, fluid ports, and electrodes. The microfluidic channels and ports allow for perfusion of nutrients, gas exchange, and biochemical control of the extracellular environment throughout the 3-D culture, while the electrodes allow for active stimulation/recording of the 3-D neuronal network. In essence, the microscaffold serves as an artificial circulatory system to enable 3-D in vitro growth and proliferation of re-aggregate neuronal cell cultures. Increased cell survival on microscaffolds with nutrient perfusion at 14 and 21 days in vitro (DIV) is presented. Additionally, the microtower scaffold is built upon a substrate that is compatible with the Multi Channel Systems preamplifier setup to enable electrical stimulation/recording of the cultured network in a 3-D mutilelectrode array (MEA) environment. Impedance measurements on the functioning microtower electrodes were obtained. The overall goal of this research was to develop a BioMEMS technology to provide neuroscientists with a better investigative tool for studying 3-D in vitro neuronal networks than is currently available.

Détecter un ensemble de marqueurs biologiques dans un sérum de patient ou bien des molécules spécifiques d'un herbicide dans un échantillon prélevé dans l'eau d'une rivière ? Etre capable de transformer une interaction biologique en un signal électrique ou encore déposer des volumes infiniment faibles de molécules biologiques sur une surface solide à des fins de diagnostique ? Passer de la fabrication de microcapteurs inertiels pour la navigation à la conception et au développement de biocapteurs micromécaniques ? Nous démontrons que le fil conducteur permettant de faire le lien entre ces domaines en apparence disjoints est matérialisé par des micro- et nanosystèmes électromécaniques développés au sein du LAAS à partir de la feuille blanche jusqu'à l'intégration du système avec son électronique associée. Quel lendemain pour les bio- microsystèmes électromécaniques ? Faut-il encore miniaturiser ? Est-il pertinent d'entreprendre le contraire ? Comment poursuivre l'aventure transdisciplinaire en étant sûr du fait que la réussite est au bout de la route ? Nous tentons de répondre à l'ensemble de ces questions tout au long de ce manuscrit retraçant l'ensemble de nos travaux de recherche effectués au LAAS et ailleurs depuis l'an 2000.

Attachment of circulating tumor cells in microfluidic devices functionalized with proper antibodies was studied. Under static experimental conditions, microchambers were utilized to study the parameters such as cell suspension concentration, incubation time or ambient temperature that may affect the binding of cell to the functionalized surfaces. Specific capture of cells from suspensions increases exponentially with incubation time and linearly with concentration within the tested range. Functionalizing a surface with counter-receptors enables capture of almost 100% of cells within 15 minutes incubation time at ambient temperature higher than 25°C. Suspending cells with different receptors, changing the counter receptors immobilized on the surface, or incubation the cell suspension at low ambient temperature result in a poor capture ratio. To illustrate the specific binding of target cells, various binary mixtures of target cancer and blood cells were incubated in the microchambers. The microsystem sensitivity, specificity and accuracy were determined as a function of the incubated cell concentrations. In general, the system specificity increases while the sensitivity decreases with increasing cell concentration; the accuracy of the system depends weakly on cell concentration within the tested range. The cell attachment dynamics in shear flow was studied by driving the MDA-MB- 231 or BT-20 cells through microchannels functionalized with EpCAM antibodies. The cell attachment ratio was experimentally determined at different flow rates. A modeling system based on Stokesian as well as cell-adhesive dynamics is adopted to analyze the cell motion. The cell motion is modeled as a rigid sphere, with receptors on its surface, moving under shear flow above a surface immobilized with ligands. The system is described mathematically by the Langevin equation, in which the receptor-ligand bonds are modeled as linear springs. Primarily depending on the applied flow rate, three distinct dynamic states of cell motion have been observed: free motion, rolling adhesion, and firm adhesion. The fraction of cells captured due to firm adhesion, defined as attachment ratio, depends on the applied flow rate with a characteristic value that increases with either cellreceptor or surface-ligand density. Utilizing this characteristic flow rate as a scaling parameter, all measured and calculated attachment ratios for different receptor and ligand densities collapse onto a single exponential curve. Binary mixtures of target MDA-MB-231 cells and non-target BT-20 cells were driven through anti-cadherin-11 functionalized microchannels to study the selective isoaltion of target cells from binary mixtures. The system sensitivity is very high, above 0.95, while the specificity is only moderately high, about 0.85, essentially independent of the relative concentration of the target and non-target cells in the binary mixture. An attachment/detachment flow field pattern is proposed to enhance the system specificity. Utilizing this flow pattern with a 1:1,000 MDA-MB-231:BT-20 binary cell mixture, the microfluidic system specificity increased to about 0.95 while the sensitivity remained above 0.95. In order to obtain high experimental throughput allowing lower relative concentration of target cells, a microchannel array which enables processing samples containing about 510⁵ cells with a minimum target cell concentration ratio of 1/100,000 was designed and fabricated. To demonstrate selective isolation of target cells, binary mixtures of BT-20 cells and MIA PaCa-2 cells were driven through microchannel arrays functionalized with EpCAM antibodies; the EpCAM positive BT-20 cells served as target cells and the EpCAM negative MIA PaCa-2 cells as non-target cells. The relative concentration ratio of target/non-target cells varied from 1:1 to 1:100,000. The sensitivity was close to 1.0 while the specificity was also high, about 0.95. The additional detachment step, with a faster flow rate, enhanced the specificity to about 0.985. Initial results of two sets of experiments are reported as preliminary studies for future work. In the first set of experiments, whole blood samples from healthy donors were spiked with a known number of BT-20 cells at a concentration of 500 CTCs per milliliter blood or 50 CTCs per milliliter blood. After a pretreatment to enrich the CTCs, the samples were driven through microchannel arrays functionalized with anti-EpCAM. For both samples, around 55% of the target CTCs were captured in the microchannel arrays. The second set of experiments was dedicated to characterization of target cells exposed to applied shear stress. BT-20 or MDA-MB-231 cells were driven through microchannels functionalized with EpCAM antibodies to allow target cell attachment; then, a high flow rate was applied to detach the captured cells. The detached cells were collected and cultured in an incubator to test their viability. For both cell lines, the majority of the captured CTCs collected from the microchannels were viable. The images taken after three and seven days of culture demonstrate continuous cell growth and division.

This thesis describes the theoretical modeling of a response of an electrochemical BioMEMS sensor for detecting small amounts of cortisol hormone. The electrochemical sensor utilizes a catalyst enzyme (3a-HSD) to convert cortisone to cortisol and the Square Wave Voltammetry (SWV) as a preferred method to measure the forward and reverse current of the system. The parameters and equations necessary to estimate the Square Wave Voltammetry (SWV) theoretical response are determined and outlined. The response is modeled and the results are compared to the experimental data. Further, the design of the sensor is analyzed and suggestions are made on how to improve the repeatability of the sensor's response. The diffusion coefficients for cortisone and cortisol hormone are calculated to be 2.87*10-10 and 2.84*10-10 square meters per second respectively with 10 percent tolerance. The dimensionless peak current (ψ) for the system is approximately 10 percent lower than the one theoretically postulated by Bard et al. [3]. The surface area of the working electrode of the sensor varies with and is directly proportional to the concentration of the analyte. Theoretical current peaks are hypothesized to be within 10 percent tolerance limits (mainly due to the reason that the surface area of the working electrode is itself a variable).

Compliant microelectrodes have been designed in a microcable geometry that can be used individually or in an array and either as a shank-style electrode or as a string-like electrode that can be threaded around features such as the peripheral nerve. The fabrication process, using spin-cast micromolding (SCuM), is simple and adaptable to different patterns. The microcables were fabricated using polydimethyl siloxane (PDMS) for the insulating substrate and thin-film gold for the conductive element. The thin, metal film and the low tensile modulus of the PDMS substrate created an electrode with a composite tensile modulus lower than other compliant electrodes described in the literature. The gold film increased the composite modulus approximately three-fold compared to the unaltered PDMS. The durability of the electrodes and tolerance for stretch was also tested. The microcables were found to be conductive up to 6% strain and to regain conductivity after release from multiple applications of 200% strain. The tolerance for high-strain shows that the electrodes can be deployed for use and stretched or pulled into place as needed without damaging the conductivity. The microcable electrode recording sites were electrically characterized using frequency-based impedance modeling and were tested for electrophysiological recording using a peripheral nerve preparation. A suitable insertion mechanism was designed to use the microcables as shank-style cortical electrodes. The microcables were coated on one side with fibrin, which, when dry, stiffens the microcables for insertion into cortical tissue. A 28-day implant study testing the inflammatory response to fibrin coated PDMS microcable electrodes showed a positive, but relatively low inflammatory response, as measured by glial fibrillary astrocytic protein (GFAP; indicating activated astrocytes) immediately at the tissue edge of the implant site. The response of the control, silicon shank-style electrodes, was varied, but also trended toward low levels of GFAP expression. The GFAP staining was possibly due to the clearance of the fibrin from the implant site in addition to the presence of the PDMS-based electrode. Implant studies extending beyond 28 days are necessary to determine whether and to what degree the inflammation persists at the implant site of PDMS-based electrodes.

In vertebrate nervous system, formation of myelin sheaths around axons is essential for rapid nerve impulse conduction. However, the signals that regulate myelination in CNS remain largely unknown partially due to the lack of suitable in vitro models for studying localized cellular and molecular basis of axon-glia signals. We utilize microfabrication technologies to develop series of CNS neuron culture microsystems capable of providing localized physical and biochemical manipulation for studying neuron-glia interaction and neural progenitor development. First, a circular neuron-glia co-culture platform with one soma-compartment and one axon/glia compartment has been developed. The device allows physical and fluidic isolation of axons from neuronal somata for studying localized axon-glia interactions under tightly controlled biochemical environment. Oligodendrocyte (OL) progenitor cells co-cultured on isolated axons developed into mature-OLs, demonstrating the capability of the platform. The device has been further developed into higher-throughput devices that contain six or 24 axon/glia compartments while maintaining axon isolation. Increased number of compartments allowed multiple experimental conditions to be performed simultaneously on a single device. The six-compartment device was further developed to guide axonal growth. The guiding feature greatly facilitated the measurement of axon growth/lengths and enabled quantitative analyses of the effects of localized biomolecular treatment on axonal growth and/or regeneration. We found that laminin, collagen and Matri-gel promoted greater axonal growth when applied to somata than to the isolated axons. In contrast, chondroitin sulfate proteoglycan was found to negatively regulate axon growth only when it was applied to isolated axons. Second, a microsystem for culturing neural progenitor cell aggregates under spatially controlled three-dimensional environment was developed for studies into CNS neural development/myelination. Dense axonal layer was formed and differentiated OLs formed myelin sheaths around axons. To the best to our knowledge, this was the first time to have CNS myelin expressed inside a microfluidic device. In addition, promotion of myelin formation by retinoic acid treatment was confirmed using the device. In conclusion, we have developed series of neuron culture platforms capable of providing physical and biochemical manipulation. We expect they will serve as powerful tools for future mechanistic understanding of CNS axon-glia signaling as well as myelination.

<p>Circulating tumor cells (CTCs) have been proved to possess great value and potential in detection, diagnosis, and <a>prognosis</a> of non-haematologic cancers. Their unique characteristics in providing both phenotypic as well as genotypic information make them highly valuable in liquid biopsy assays. A<a>t the same time, though numerous studies and research have been done, identification and enumeration of CTCs is still technically challenging due to their rarity and heterogeneity</a>. The primary goal of the thesis is to develop a CTC detection and isolation system with ultra-high sensitivity and purity, while keeping it fast and scalable. We proposed a microfluidic system that integrates positive immunomagnetic capturing, high-throughput parallel flow and size filtration. In this thesis, two generations of the system have been developed to achieve the goal, and are approved to be able to effectively detect and isolate CTCs from hundreds of breast cancer blood samples in real clinical applications. </p> <p>The first-generation system is based on a sandwich-structured microfluidic chamber, which has a micro-aperture chip as the core to detect and isolate immunomagnetically targeted CTCs. The system achieves high detection yield (>95%) and purity (>99.9998% depletion of leukocytes) by streamlining the workflow and using unprocessed whole blood (without centrifuging), as well as utilizing an advanced surface coating approach to passivate the microchip surface. <a>We first demonstrate experiments for determining the optimal detection parameters. Then we characterize the system by isolating deterministically spiked 1, 10, and 100 single MCF-7 breast cancer cells into tubes of whole blood, and show that >95% of cells were captured. A detection yield of 100% from single cell spiking experiments (n = 6) demonstrates excellent detection capability and repeatability of the system. We finally demonstrate the use of the system for CTC detection in the context of a phase II clinical trial of early-stage triple-negative breast cancer (TNBC) patients. As a part of the trial, 182 blood samples were collected from 124 early-stage TNBC patients at high-risk of relapse. We detected CTCs in 36.3% of patients who had already completed chemotherapy and surgery for curative intent and were thus nominally expected to have very few to zero CTCs. </a>Moreover, increasing CTC count from the same patients shows good correlation with <a></a><a>their clinical course</a>. The ability to detect CTCs’ presence using this first-generation system illustrates its important clinical utility.</p> <p>The second-generation system applies a similar detection strategy but employs an upgraded microchip and device, as well as a further streamlined process flow to achieve an even higher detection efficiency, especially for capturing the target cells with low surface marker expression level. We first did modeling and simulation of the new system to find the optimal magnet configuration and verify the detection sensitivity improvement on the first-generation system. Then we characterized the new system by detecting spiked JEG-3 and JAR cells in both cell culture medium and human blood. The result demonstrates that the detection yield increased by ~20% using the second-generation system under the same experiment condition. Next, we applied the system to a phase I clinical trial for CTC detection from metastatic triple-negative breast cancer (mTNBC) patient blood samples. CTCs of mTNBC are known to with in the low marker expression phenotype, which requires ultra-high detection sensitivity. Our system captured CTCs from 48 out of 102 (47%) blood samples, the positivity rate agrees with the conclusions from other studies and presents the reliability to the system. Finally, we explored a novel 4-marker panel for CTC detection from mTNBC patient blood samples. We conducted paired comparisons using the 4-marker panel versus a single marker for detection. The 4-marker panel yielded more CTCs in 5/8 complete paired assessments, and less CTCs in 1/8. The association missed the significance level only slightly (p = 0.08), and the result strongly illustrates the potential for using the panel to cover the mTNBC cells’ heterogeneity for enhanced CTC detection. Furthermore, the presence of CTCs from blood samples correlates well with the patient’s disease progression.</p> <p>Finally, we demonstrated downstream analysis ability of the CTCs detected by the second-generation system. Captured CTCs can be readily released from our system without any loss or damage to a secondary microchip device to be further isolated as single cells, and picked up individually for downstream analysis like DNA/RNA sequencing or single-cell cultivation. Directions for future work is also discussed. We envision this versatile and efficient system to be highly beneficial in a broad range of clinical and research applications regarding CTCs.</p>

This work presents the modeling, design, and testing of an underwater microactuation system. It is composed of several thermomechanical in-plane microactuators (TIM) integrated with a ratchet system to provide long displacements and high forces to underwater microelectromechanical systems (MEMS). It is capable of actuating a 200µN load 110µm. It is a two-layer silicon MEMS device fabricated with a MEMS fabrication process, PolyMUMPS. This work also shows the development of an elliptic integral model to analyze the compliant fixed-guided beams in the TIM and gives new insight into the buckling behavior, reaction forces, and displacement of the beams. The derivation, verification, and practical use of the model are shown in detail. It compares the reaction force predictions from the elliptic integral model with finite element modeling results over a wide range of non-dimensional displacements and slenderness ratios. The elliptic integral model was used to design a TIM that can operate in an aqueous environment. It was designed to achieve 9µm of displacement to drive a linear ratcheting mechanism. The thermal analysis was done in ANSYS using a 3D conduction model to predict the temperature of the heated beams. The TIM was designed to operate with a peak beam temperature of 100 ° C to prevent damage to the device due to vapor bubble formation. The main actuator showed significant electrolysis due to the high voltages used to drive the system, but otherwise functioned as predicted. Through the development and testing of the actuation system, quantitative voltage limits were discovered for underwater actuation systems under which electrolysis and boiling can be eliminated using alternating current.

This thesis utilizes previously described manufacturing and design techniques for the creation of a PDMS-glass bonded microfluidic device, capable of electrochemical impedance spectroscopy (EIS). EIS has been used across various fields of research for different diagnostic needs. The major aim of this thesis was to capture cancerous and non-cancerous cells between micron sized electrodes within a microfluidic path, and to complete analysis on the measured impedances recorded from the two differing cell types. Two distinct ranges of impedance frequency were analyzed – the α dispersion range, which quantifies the impedance of the membranes of the cells of interest, and the β dispersion range, which quantifies the impedance of the cytosol of the cells of interest. This thesis is unique in the fact that it looks at the cellular impedances of two types of neural cells, which has not been documented previously in literature. The type of cancerous cells analyzed were Neuro-2-A cells, an immortalized line of murine glio/neuroblastoma. The type of non-cancerous cells analyzed were murine primary astrocytes, a mortal line of neurological support cells found throughout the nervous system, and with great abundance in the brain. By using a LabView program coded by a previous Cal Poly student, a sweep scan across a wide frequency range was completed on both cell types, and statistical analysis was completed on target frequencies of interest. A significant difference was found between the two cell lines’ membrane impedances, however no difference was found between the cytoplasm impedances. In total, this thesis aimed to fabricate a reusable microfluidic device capable of EIS for future Cal Poly students, create a protocol suitable for cell culturing and device operation, and to lay a foundation of knowledge for impedance comparisons regarding neural cancerous and non-cancerous cells.