In the area of MEMS there exists a tremendous need for communication between the micro-device and the macro world. A standard protocol or at least multiple standards would be of great use. Electrical connections have been standardized for many uses and configurations by the integrated circuit industry. Standardization in the IC industry has created a marketplace for digital devices unprecedented. In addition to the number of "off the shelf" products available, there exists the possibility for consumers to mix and match many devices from many different manufacturers. This research proposes some similar solutions as those for integrated circuits for fluid connections and mechanical configurations that could be used on many different devices. In conjunction with offering the capability to facilitate communication between the micro and macro worlds, the packaging solutions should be easy to fabricate. Many devices are by nature non-standard, unique, designs that make a general solution difficult. At the same time, the micro-devices themselves will inevitably need to evolve some standardization. In BioMEMS devices the packaging issue is concerned with delivering a sample to the device, conducting the sample to the sensor or sensors, and removing the sample. Conducting the sample to the sensor or sensors is usually done with microchannels created by standard MEMS fabrication techniques. Many current designs then utilize conventional machining techniques to create the inlet and outlet for the sample. This work proposes a rapid prototyping method for creating the microchannel and inlet / outlet in simplified steps. The packages developed from this process proved to be an effective solution for many applications.

A continuous flow, passive separation device was designed using an equivalent circuit to create variable flow rates for hydrodynamic focusing to drain channels and collection outlets. By varying the diameter of the sample inlet connection into the reservoir, the particle position was influenced significantly, which enabled desired separations. Additionally it was noted that the relative, horizontal position of the inlet also had a significant influence on particle position within the device. A dimensionless number, the Characteristic Sample Inlet, was developed to relate geometric properties of the inlet reservoir to downstream particle distribution. It was found that a 2:1 ratio between inlet reservoir and sample inlet diameter, and placed at the top of the reservoir yielded the best separation results. Fluid velocity profiles in the reservoir were explored using Comsol Multyphysics. The experimentally observed particle trajectories and COMSOL predictions were in good agreement. Based on Comsol models a dimensionless parameter to relate the unique velocity profiles within the inlet reservoir to downstream separation of particles was also developed. A mixture of 10, 5.5, and 3.0 µm particles were separated to three distinct collection outlets at 73.4%, 64.7%, and 52.8% respectively. Therefore this project shows that passive separations of particles can be achieved simply by alerting the ratio of inlet hole relative to inlet reservoir diameter, and by placing the inlet hole at the top of the reservoir.

The purpose of this thesis project is to demonstrate the ability to utilize electrophoresis in a cellulose paper microfluidic chip to manipulate charged particles. Materials were selected and a manufacturing protocol was created to successfully apply the electric field onto the paper chip. Experiments were performed to characterize the separation rates for charged, colorimetric dye, Orange G in the membrane as a function of an applied electric field, dye concentration, and distance traveled. The experiments confirmed that the electric field can be applied to the chip and particle separation rates were characterized. Next, the determined rates results were used to design a device that used a transverse electric field to the flow direction to separate Orange G into a collection channel. Results showed that electrophoresis can be used to separate the flow of charged particles on a paper microfluidic device. In conclusion, the application of electrophoresis was shown to be successful. An approach to be utilized as a sample treatment to improve the detecting capability of low cost paper devices for a more accurate diagnostic test in the developing world.

Recently there has been an increased focus on the use of microfluidics for the synthesis of different products. One of the products proposed for synthesis is quantum dots. Microfluidics often uses Polydimethylsiloxane for structure in microfluidic chips, but quantum dots use octadecene in several synthesis steps. The purpose of this work was to create a lab setup capable of anodically bonding 4” diameter wafers, and to characterize the bond formed using the Plaza test chip so that microfluidic devices using glass and silicon as substrates could be created. Two stainless steel electrodes placed on top of a hot plate were attached to a high power voltage supply to perform anodic bonding. A Plaza test mask was created and used to pattern P type silicon wafers. The channels etched were between 300 and 500nm deep and ranged between 1000µm and 50µm. These wafers were then anodically bonded to Corning 7740 glass wafers. Bonding stopped once the entire surface of the wafer was bonded, determined by visual inspection. All bonds were formed at 400°C and the bond strength and toughness between wafers bonded at 400V and 700V was compared. A beam model was used to predict the interfacial fracture toughness, and the stress at the bond was calculated with a parallel spring model. By measuring the crack length of the test structures under a light microscope the load conditions of the beam could be found. It was concluded that the electrostatic forces between the wafers give the best indication of what the bond quality will be. This was seen by the large difference in crack length between samples that were bonded using a thick glass wafer (1 mm) and a thin glass wafer (500µm). The observed crack lengths for the thick glass wafers were between 40 and 60µm. Thin glass wafers had a crack length between 20 and 40µm. The fracture toughness was calculated using the beam model approximation. Fracture toughness of the thin glass wafers was 7MPa m1/2, and of the thick glass wafers was 30 MPa m1/2. The fracture toughness of the thick glass wafers agreed with results found through the use of the double cantilever beam samples in literature. The maximum observed interfacial stress was 70 MPa. Finally, to measure the change in the size of the sodium depletion zone formed during bonding, samples were placed under a scanning electron microscope (SEM). Depletion zones were found to be between 1.1 and 1.4µm for thin glass samples that were bonded at 400 and 700 volts. This difference was not found to have a significant effect on the strength or fracture toughness observed. Thicker glass samples could not have their depletion zone measured due to SEM chuck size.

Antibiotic resistant infections are a growing health care concern, with many cases reported annually. Infections can cause irreversible bodily damage or death if they are not diagnosed in a timely matter. To rapidly diagnose antibiotic resistance in infections, it is important to be able to capture and isolate the DNA coding for the resistance genes. This is challenging because bacteria are present in blood in minute concentrations. To enrich the DNA to detectable levels, I modified magnetic microbeads with ssDNA sequences complementary to the target DNA to capture the DNA via hybridization. I compared DNA capture efficiency in three different methods: Co-flow, packed bead bed, and pre-hybridization. The pre-hybridized method worked better than the other two. Since pre-hybridization involved mixing, I chose to study mixing in a microfluidic device. The mixing chamber was a well carved out of PMMA placed between two electromagnets. To test the mixing well, beads and capture DNA were placed in it, and the electromagnets were subjected to different frequencies, including symmetric or asymmetric magnetic fields. For each condition the capture efficiency was determined by measuring the relative fluorescence units (RFU). A 100 Hz asymmetric magnetic field had the best capture efficiency out of all conditions. These results demonstrate a path for enriching low concentrations of DNA to detectable levels, and future work should be done to develop electromagnetic mixing in microfluidic devices.

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No description available.

The growing threat of antimicrobial resistance is among the largest concerns in the world today. One method under development to combat this issue is the encapsulation of microbes in microfluidic droplets for single-cell testing. This method may be able to circumvent the need for a traditional positive cell culture which consumes the majority of the testing time using current diagnostic methods. This dissertation presents a method by which to deterministically encapsulate microbes using an artificial intelligence object detection algorithm and a Droplet-On-Demand microfluidic device. To accomplish this, the Droplet-On-Demand microfluidic device was first developed using a unique 3D-printing manufacturing method. An annular Channel-in-Channel droplet generator was developed which produced droplets within the hydrophobic 3D-printed polymeric microfluidic device. Supporting microfluidic unit operations were also developed including pumps, a 3-way flow-thru valve, and a detection window used for visualizing microfluidic particles. Control software was developed using python which controlled pneumatically-actuated membranes within the microfluidic device, the imaging system, and the object detection algorithm. 20-μm and 2-μm test particles were used as non-biological test particles while red blood cells and fluorescent E.coli baceria were used as biological test particles. All test particles were identified and encapsulated and show the flexibility of the system overall and the ability to identify a variety of particles of interest in microfluidic systems. Growth tests were conducted using E.coli bacteria encapsulated within microfluidic droplets with a fluorescent metabolic indicator. The fluorescence of droplets containing actively growing encapsulated bacteria was quantified using a unique first-principles model paired with an image processing protocol to provide relative concentration data to quantify the growth of the E.coli over time. These growth results indicated that bacterial growth in droplets could be detected and quickly quantified in 4 hours and thus provide practical results to clinicians on the susceptibility of bacteria to an antibiotic. This Droplet-On-Demand technology has the capability of providing clinically applicable data from the most basic and fundamental biological source, an individual cell; and that can be done with low concentrations and on any cell that can be visually identified.

Over the past three decades, the field of tissue engineering has witnessed significant advancements. However, a persistent challenge is the development of an approach to generate rapidly perfused vascular networks at scale to support engineered tissues of appreciable size and able to adapt to changing needs. Current techniques able to create perfusable channels such as 3D printing are resource intensive and have not overcome the inherent tradeoff between vessel resolution and assembly time, limiting their utility and scalability for engineering tissues. Here we present two sacrificial self-assembly techniques that collectively develop microvascular networks and can anastomose to a variety of engineered forms. The first is vasculogenic cellular self-assembly, which leverages the innate ability of endothelial and sacrificial support cells to spontaneously form a capillary network, which we term CAMEO, or Controlled Apoptosis in Multicellular Tissues for Engineered Organogenesis. By varying the removal timing of the support cells, we determine fibroblasts are necessary for the initial vascular morphogenesis in our engineered system, and that this initial support period is sufficient for the endothelial cells to form a perfusable vasculogenic network and enhance the function of primary hepatocyte aggregates. The second is a flexible and scalable technique we term SPAN – Sacrificial Percolation of Anisotropic Networks. It uses microvascular-scale sacrificial fibers that make contacts to span a volume above a percolation density threshold and are then degraded. The resulting interconnected anisotropic voids form a perfusable fluidic network within minutes. We show that SPAN relieves hypoxia compared to bulk gels only, and the resulting voids created by SPAN can be endothelialized in a scalable way. These simple platforms can generate conduits with length scales spanning arterioles to capillaries within constructs. We show that both techniques can be used in combination with common tissue engineering processes, paving the way for rapid assembly of adaptable and perfusable tissues. / 2026-01-17T00:00:00Z

Sepsis is a “life-threatening organ dysfunction caused by a dysregulated host response to infection” that has a widespread impact on human life around the world. It affects more than 1.5 million people, killing at least 250,000 each year in the US alone and affects 90,000 people annually, with estimated mortality rates of up to 30% in Canada. Our understanding of the different biochemical pathways that in the progression of sepsis has improved patient care for sepsis patients. One part of patient care is the use of biomarkers for patient prognosis that draws on the full range of relevant and available information to model the possible outcomes for an individual. Numerous biomarkers have been studied for patient prognosis that includes Procalcitonin (PCT), C-reactive protein (CRP), TNF-α, cfDNA, protein C and PAI 1. Using a panel of multiple biomarkers provided more accuracy in patient prognosis than using individual biomarkers and one such panel that was proposed used cfDNA, protein C, platelet count, creatinine, Glasgow Coma Scale [GCS] score, and lactate. Commercial, low cost POC techniques were available for the measurement of all biomarkers besides cfDNA and protein C. The objective of this doctoral thesis was chosen to develop low cost, microfluidic devices for the measurement of protein C and cfDNA using nonspecific fluorescence dyes that would enable the eventual integration of the systems and improve patient prognosis. The measurement of protein C in plasma required the separation of protein C from interfering proteins in plasma. This was done through the development of a two-stage separation process that included the development of tunable agarose isoelectric gates for separating proteins using their isoelectric point and the miniaturization of immobilized metal affinity chromatography and its extension to Barium for the selective binding of proteins using their chemical affinity. This was performed in a xurographically fabricated chip to reduce costs and enable the use of geometric focusing of the electric field to enable the operation of the device at a lower applied voltage. The challenges faced with cfDNA were different due to the different characteristics of the material and less interference from plasma. The requirement was to measure the total cfDNA content with minimal cost in comparison to currently available techniques. This was achieved through the development of thread microfluidic devices that showed the use of thread for automated aliquoting of samples by controlling length and twists of the thread. Preconcentration and use of external apparatus was avoided by showing that thread could be used to amplify fluorescence response to a range that was sufficient for the measurement of cfDNA in sepsis patients. A portable fluorescence imaging setup was developed for this purpose and was used in demonstration for the measurement of cfDNA in plasma with sufficient resolution. In conclusion, we developed technologies for rapid and low-cost measurement of protein C and cfDNA using xurographic and thread-based microfluidics that may serve as valuable in improving patient prognosis. / Thesis / Doctor of Philosophy (PhD) / Sepsis is a major reason for hospitalization and cause of death in hospitals worldwide. Its treatment is highly time sensitive with each hour of delay in diagnosis causing a significant increase in chances of death. Due to the wide range of symptoms that can be caused by sepsis, its diagnosis uses a scoring method that relies on the expertise of the onsite doctors and nurses increasing their workload. A more objective system for detection requires the measurement of the quantities of different biomarkers in blood. Biomarkers are proteins present in plasma that change in quantity due to the body’s reaction to sepsis. Several of these biomarkers have been identified and studied for their use in both diagnosing the presence of sepsis and in predicting the outcome with the current treatment plan. In this PhD study, we chose two of these biomarkers – circulating free DNA (cfDNA) and protein C and developed low-cost techniques for rapidly measuring their concentration in blood plasma. To do this, we made microfluidic devices with techniques that use low-cost materials such as plastic sheets and threads.The device for the measurement of protein C required separating it from many other proteins in plasma. We showed that a device fabricated from stacked plastic sheets and integrated with agarose gels could be used for the measurement of protein C in plasma with sufficient resolution to help with treating septic patients at a cost of less $5 per device. Similarly, we showed that a device that integrated threads with plastic sheets could be used for measuring the quantity of cfDNA in plasma in a portable format within 15 minutes. Overall, we developed tools for rapid measurement of two biomarkers of sepsis using low cost device that cost under $5 to run and could led to improving the quality of care for sepsis patients.