Browsing by Subject "microfluidics"

Now showing 1 - 7 of 7
  • Thumbnail Image
    Item
    3D Printing Of Large-Scale Integrated Microfluidic Devices
    (2024) Kaarthik, Saravanan Sujit
    The ability to manufacture large-scale integrated microfluidic devices (mLSI) in an automated fashion with high throughput could impact numerous areas, including single-cell assays, drug discovery, and multi-sample analysis of human fluids. Conventional microfluidics fabrication is labor-intensive and requires the use of specialized facilities. Our group previously pioneered a method to 3D print microfluidic channels and valves by extruding silicone filaments in angular stacks. This technique faced limitations in scaling due to slow printing speed (1 mm/s) and inability to generate multiplexed flows. Here, we present an approach to 3D print mLSI devices that introduces an innovative method to reinforce channels locally and reduce the printing time 20-fold by doubling the extrusion diameter of the filaments. This allows for the incorporation of a Boolean design strategy that requires specific valves to remain open when actuated. This work paves the way for point-of-need mLSI production for medical diagnostics and disease detection.
  • Thumbnail Image
    Item
    Capillary Flow and Evaporation in Open Microchannels
    (2021-05) Kolliopoulos, Panayiotis
    Capillary flow is the spontaneous wicking of liquids in narrow spaces without the assistance of external forces. Examples of capillary flow can be found in numerous applications ranging from lab-on-a-chip devices to printed electronics manufacturing. Open rectangular microchannels often appear in these applications, with the lack of top resulting in a complex free-surface morphology and evaporation. While prior work has demonstrated that evaporation hinders capillary flow, the underlying fundamentals that are vital to the design and optimization of applications such as printed electronics manufacturing are still lacking. In this thesis we investigate the fundamentals of capillary flow and evaporation in open microchannels using theory and experiment. We initially consider flow of nonvolatile liquids to elucidate the capillary-flow dynamics. We develop a novel self-similar lubrication-theory-based (LTB) model accounting for the complex free-surface morphology and compare model predictions to those from the widely used modified Lucas-Washburn (MLW) model, as well as experimental observations over a wide range of channel aspect ratios and equilibrium contact angles. We identify the limitations of the MLW and LTB models and demonstrate the importance of accounting for the effects of the complex free-surface morphology on capillary flow. We also show that the LTB model accurately captures the dynamics of fingers that extend ahead of the front meniscus which are not accounted for by the MLW model. Capillary flow of evaporating liquid solutions are examined using two theoretical models. We first develop a Lucas-Washburn-type one-dimensional (1D) model, which accounts for concentration-dependent viscosity and uniform evaporation. The second model is a lubrication-theory-based model, which accounts for the complex free-surface morphology, non-uniform solvent evaporation, Marangoni flows due to gradients in solute concentration and temperature, and finite-size reservoir effects. Both models are compared to prior capillary-flow experiments of aqueous poly(vinyl alcohol) solutions in the presence of evaporation. While the 1D model qualitatively captures evaporation effects on the flow dynamics, it underestimates their magnitude. The lubrication-theory-based model predictions are in good agreement with experimental observations, and predicted evaporation rates are comparable with experimental estimates. Numerical results also reveal significant qualitative differences in capillary flow of evaporating pure solvents and liquid solutions. Additionally, Marangoni flows are found to promote more uniform solute deposition patterns after solvent evaporation. Ultimately, these findings advance the fundamental physical understanding of capillary flow with evaporation and provide guidelines for the design and optimization of numerous applications.
  • Thumbnail Image
    Item
    Data for "3D Printing-Enabled DNA Extraction for Long-Read Genomics" published as ACS Omega 2020, 5, 20817-20824
    (2020-08-31) Agrawal, Paridhi; Reifenberger, Jeffrey G; Dorfman, Kevin D; agraw135@umn.edu; Agrawal, Paridhi; University of Minnesota Dorfman Lab
    The deposited data files have DNA size measurement critical to demonstrating long DNA extraction in the microfluidic device, and DNA concentration measurement to show the yield of the platform.
  • Thumbnail Image
    Item
    Data supporting 'Subdiffusion of loci and cytoplasmic particles are different in compressed E. coli cells'
    (2018-05-15) Yu, Shi; Sheats, Julian; Cicuta, Pietro; Sclavi, Bianca; Cosentino Lagomarsino, Marco; Dorfman, Kevin D; dorfman@umn.edu; Dorfman, Kevin D
    The complex physical nature of the bacterial intracellular environment remains largely unknown, and has relevance for key biochemical and biological processes of the cell. While recent work has addressed the role of non-equilibrium drives and crowding, the consequences of mechanical perturbations are relatively less explored.We have used a microfabricated valve system to track both fluorescently labeled chromosomal loci and cytoplasmic particles in E.~coli cells shortly after the application of a compressive force on time scales that are too sudden to allow for biochemical response from the cell. While cytoplasmic diffusion is slowed down significantly under compression, the mobility of DNA loci is much less affected. These results suggest that the dynamics of the bacterial chromosome are decoupled from the viscoelastic environment of the cytoplasm under such short time scales, and that DNA elasticity and nucleoid organization play a more important role in loci subdiffusion than cytoplasmic viscoelasticity.
  • Thumbnail Image
    Item
    The Effects of Therapeutic Strategies in Restoring Sickle Cell Disease Blood Rheology
    (2022-04) Hansen, Scott
    Sickle cell disease is a hereditary disease of the hemoglobin with devastating acute and chronic complications. The pathological polymerization of sickle hemoglobin during hypoxia reduces red blood cell deformability and increases blood viscosity. These biophysical changes to the red blood cells and whole blood rheology can obstruct blood flow and contribute to vaso-occlusion in the microcirculation. Though the genetic and molecular basis for the disease has been understood for decades, limited treatment options are available to those who suffer from this disease. Microfluidic platforms provide a physiologically relevant pre-clinical model to assess the response of sickle cell blood rheology to therapeutic strategies in vitro. This work focuses on the roles of affinity modifying compounds and high expression of fetal hemoglobin in inhibiting sickle hemoglobin polymerization and restoring healthy blood rheology. Isolating the biophysical effects of these therapeutic strategies on blood flow provides a better understanding of their mechanisms of action that may be of clinical significance. Microfluidic studies of sickle cell disease blood flow may help accelerate drug development and improve patient outcomes.
  • Thumbnail Image
    Item
    Microfluidic Dna Sample Preparation For Long-Read Genomics
    (2020-05) Agrawal, Paridhi
    With the commercialization of genomics technologies, DNA sequencing has become an affordable and accessible tool for innumerable biological advancements. The fast speed, low cost, automated measurement and high throughput nature of these sophistically engineered miniaturized systems is made possible by the rapid advancement in microfluidics. Owing to superior fabrication capabilities and adequate handling of complex samples, microfluidic systems have shown promise for varied biological applications. While measurements are performed at the micro scale in all genomics systems, DNA extraction and pre-processing are done externally, resulting in a wide mismatch between the amount of sample prepared and the amount utilized. This work focuses on using microfluidics as a tool to assist, and hopefully improve, genomics methods. Long-read genomics technologies are capable of obtaining long-range information from DNA molecules about repetitive and complex regions of the genome. Optimal application of these technologies requires shear-free methods for extracting long DNA from cells. These sample preparation tools should be facile, inexpensive, universal and amenable to automation. In addition to providing all these capabilities, microfluidics can not only expedite sample preparation, but also offer the opportunity for direct upstream integration to eliminate DNA fragmentation and loss during transfer to the genomic device. The work outlined here presents a microfluidic platform for long DNA sample preparation. In the 3D cell culture-inspired proof-of-principle poly(dimethylsiloxane) device, gel-based high molecular weight DNA extraction and continuous flow purification is followed by electrophoretic extraction of the long DNA from the miniaturized gel. The device successfully demonstrated extraction of DNA as long as 4 megabase pairs from cells, but the 10 ng DNA yield was insufficient for some genomics experiments. A scaling up of the device design, realized by 3D printing, resulted in a high-yield next-generation device which completely eliminates cleanroom fabrication, making the method accessible to users outside the microfluidics community. The 100 ng DNA extracted from the next-generation device were used for size analysis in commercial genome mapping nanochannels. Along with competitive yield and DNA sizes, the miniaturized format reduces the standard day-long DNA extraction process to a few hours, making it a promising prototype platform for routine long DNA sample preparation. The generic device design and straightforward protocol provide integration and automation capabilities to the platform presented, which are absent in existing alternatives to the plug lysis method. Future avenues of development and application are hypothesized to fully realize the potential of the sample preparation platform. The continued engineering and genomics upgrades justify the proposed strategies.
  • Thumbnail Image
    Item
    Nanogap for wireless fluidics and dielectric manipulations
    (2020-12) Ertsgaard, Christopher
    An inevitable response to the SARS-CoV-2 pandemic and the threat of similar future global calamities is an advancement in public health protocols--including testing and early diagnostics. This technology will require rapid detection of low-concentration material and should exist within a simple framework that is portable and cheap to manufacture. Nanotechnology can enhance detection sensitivity by focusing the sensing volumes of measurement signals to the size of the analyte. However, adequate transport of the analytes to these small volumes is often not addressed and can greatly limit detection. Diffusion transport, being the state-of-the-art, is not rapid and results in random analyte placement. In this work, nanostructures are engineered to serve a dual role to expedite analyte transport and support biosensing. Specifically, nanogap electrodes, surface-tension-mitigating geometry, and resonant circuitry are combined to rapidly focus biological particles and the liquid medium itself to the most sensitive regions for fluorescent imaging, vibrational spectroscopy, and impedance-based sensing. Additionally, these structures can facilitate practical actions such as filtering, mixing, and chemical labeling, and be powered using a sub-5 volt, wireless, radio-frequency signal (with a smartphone demonstration included). This design offers a simple approach for analyte transport to complement the advantages of sensitive nanotechnology while being portable, easily manufacturable, and as accessible as one's front pocket.