Advances in microfluidics and lab on a chip technologies

pre-printAdvances in molecular biology are enabling rapid and efficient analyses for effective intervention in domains like biology research, infectious disease management, food safety and bio-defense. The emergence of microfluidics and nanotechnologies has enabled both new capabilities and instrument sizes practical for point-of-care (POC). They have also introduced new functionality, enhanced the sensitivity, and reduced the time and cost involved in conventional molecular diagnostic techniques. This chapter reviews the application of microfluidics for molecular diagnostics methods like nucleic acid amplification, next generation sequencing, high resolution melting analysis, cytogenetics, protein detection and analysis, and cell sorting. We also review microfluidic sample preparation platforms applied to molecular diagnostics and targeted to sample-in, answer-out capabilities

Doctor of Philosophy

dissertationLiposomes are small vesicles filled with an aqueous solvent, bounded by a fluid shell that is comprised of a lipid bilayer. The bilayer may contain a single lipid species or a complex mixture that approximates the lipid content of a specific cellular membrane. This research developed a microfluidic and a biological framework for creating and probing the functionality of synthetic vesicles. To study vesicles that either approximated the size of cells or endosomal compartments, a microfluidic device was developed capable of creating nano- or microscale vesicles. This was the first demonstration of a microfluidic strategy able to access both size ranges. This technique enabled the discovery of novel functionality of several ESCRT-III (Endosomal Sorting Complex Required for Transport) proteins while also enabling the first in-depth electron microscopy analysis of liposomes created by a microfluidic platform. To encourage adoption of the microfluidic technique developed in this work, a three-dimensional (3D) printed framework was developed for manufacturing leak-free, transparent microfluidic devices. The methodology developed in this section led to the creation of the smallest ever FDM (Fused Deposition Modeling) 3D printed microfluidic channels (400 μm x 400 μm), demonstrating leak-free operation up to ~5MPa. To increase heat resistance of these devices, an annealing technique was developed for PLA (Poly(lactic Acid)). This was used to demonstrate the first DNA melting analysis on a 3D printed microfluidic device capable of withstanding temperatures up to 100ºC. iv A new method was developed for the 3D printing of 200 μm x 200 μm channels, the smallest to date using an FDM style printer. In conjunction with this method, a technique was developed for direct integration of a polycarbonate membrane into a 3D printed device. The entirely 3D printed protocol was used to demonstrate continuous formation of vesicles. This was the first demonstration of vesicles synthesized using a 3D printed platform. This technique enabled encapsulation of high ionic strength solutions in cell-sized vesicles (~5 μm), created in a low viscosity fluid

Modeling Tools for Micro-scale Stress Analysis of Nano-engineered Fiber-reinforced Composites

Possessing excellent stiffness and strength, carbon fiber reinforced polymers (CFRPs), however, have a limited toughness. The first damage in CFRPs usually occurs in transverse plies where stiff carbon fibers are microscopic stress concentrators in the matrix. The toughness of CFRPs can be enhanced by adding carbon nanotubes (CNTs) – nano-reinforcements of a high aspect ratio and exceptional stiffness – into the polymer. CNTs are believed to redistribute matrix stresses by lowering the matrix stress concentration scale from micro-level – around carbon fibers – to nano-level – around CNT tips – thereby hindering damage onset. The aim of this work was to understand the effect of CNTs on the stress distribution in CFRPs using a numerical approach. A novel finite element model was developed that represents thousands of individual CNTs with a “true-to-life” morphology in a composite with microscopic fibers in a single simulation. A numerically efficient “embedded elements” method was verified against analytical and numerical solutions. The developed model captured the matrix stresses between individual CNTs, thereby allowing the microscopic matrix stresses within the CNT-rich matrix regions to be captured as well. The discovered heterogeneity of the matrix stress fields in nano-engineered fiber reinforced composites with CNTs (nFRCs) was found to be strongly affected by the length, position, orientation, waviness and concentration of the CNTs. CNT agglomerates were shown to behave as stiff microscopic particles and to exacerbate the existent stress concentrations. CNTs introduced at fiber surfaces by fiber grafting or sizing/coating with CNTs were found to increase stresses in resin-rich zones between the fibers. CNTs grown on fibers were also shown to effectively suppress stress concentrations in the matrix close to the fiber surface. The conventional CNT configurations in FRCs were shown to be suboptimal for the purpose of suppressing microscopic stress concentrations: this was at the cost of stress magnification in other matrix regions. To address this issue, a novel concept of intelligent hierarchical nFRCs was proposed and modeled. Combining precise localization and orientation of CNTs, a complete elimination of microscopic inter-fiber stress concentrations was achieved by aligned CNT “bridges” constructed interdependently with the fiber positions in FRC. The modeling results presented in this thesis are the first step towards practical realizations of such hierarchical structures. Designed to suppress micro-scale stress concentrations in the material, the intelligent CNT networks are, hence, designed to postpone the damage onset in the fiber composites.status: publishe

POLARIZATION ECHO IN PIEZO-POWDERS AND FERROELECTRIC MONOCRYSTALS IN TEMPERATURE FIELD OF STRUCTURAL PHASE TRANSITIONS

Two new phenomena have been discovered: unigue long-living stimulated polarization echo (PE) in the piezo-electric powders the phase memory of which is kept during several dozens of days in the wide temperature interval including room temperature; PE signal which is observed only in the temperature field of the structural phase transitions in the ferroelectric monocrystals (for example, in potassium dihydrophosphate crystals from -143 to -163 degrees C) along polar axis of the monocrystal where the anomal non-linear properties are displayed. The echo is formed in the piezo-powders if the basic frequency of the RF-pulses and echo signal coincides. But in monocrystal the echo is formed on the summary or difference basic frequencies of RF-pulses, in this case the presence of the constant electric field in obligatory. The original pulse band-pass plant in the bandwidth up to 100 MHz has been developed and created. A large number of the effects has been discovered: strong switching of the long-living echo signal phase at certain values of the RF field amplitude; minimum of the sound absorption in field of the phase transition (acoustic "clarity"), the minimum depth is increased with growth of the sonic wave amplitude; anomal closing-down signal at excitation with three RF-pulses; generation of the sonic modes on the harmonics and subharmonics in the interval of one grad.; compression of the echo signal by an intrapulse frequency modulationAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

Study on flows of helium antiprotons, electrons, deuterons and isotopes and nuclei of oxygen to iron in primary space radiation on high-altitude automatic aerostats

Available from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

Modelling evidence of stress concentration mitigation at the micro-scale in polymer composites by the addition of carbon nanotubes

A versatile two-scale model was developed to investigate the use of carbon nanotubes for re-distribution and, eventually, suppression of stress concentrations on the micro-level in fiber-reinforced composites. With this model a variety of CNT assemblies could be generated including CNTs dispersed in the matrix, grown on fibers or spatially organized in a network. The presence of CNTs in a composite was found to induce strong heterogeneity in stress fields. CNTs grown on fibers were shown to suppress stress concentrations at the fiber/matrix interface but to increase stresses in resin rich zones between the forests. Agglomerated CNTs were found to behave as stiff microscopic particles leading to additional stress magnification. A promising way to suppress stress concentrations without affecting stresses in the rest of the matrix was to position CNTs in a network that is interdependent with fiber positions.publisher: Elsevier articletitle: Modelling evidence of stress concentration mitigation at the micro-scale in polymer composites by the addition of carbon nanotubes journaltitle: Carbon articlelink: http://dx.doi.org/10.1016/j.carbon.2014.10.061 content_type: article copyright: Copyright © 2014 Elsevier Ltd. All rights reserved.status: publishe

A Tunable Microfluidic Device Enables Cargo Encapsulation by Cell‐ or Organelle‐Sized Lipid Vesicles Comprising Asymmetric Lipid Bilayers

Cellular membranes play host to a wide variety of morphologically and chemically complex processes. Although model membranes, like liposomes, are already widely used to reconstitute and study these processes, better tools are needed for making model bilayers that faithfully mimic cellular membranes. Existing methods for fabricating cell-sized (μm) or organelle-sized (tens to hundreds of nanometers) lipid vesicles have distinctly different requirements. Of particular note for biology, it remains challenging for any technique to efficiently encapsulate fragile cargo molecules or to generate liposomes with stable, asymmetric lipid leaflets within the bilayer. Here a tunable microfluidic device and protocol for fabricating liposomes with desired diameters ranging from ≈10 μm to ≈100 nm are described. Lipid vesicle size is templated by the simple inclusion of a polycarbonate filter within the microfluidic system and tuned with flow rate. It is shown that the vesicles made with this device are stable, unilamellar, lipid asymmetric, and capable of supporting transmembrane protein assembly, peripheral membrane protein binding, as well as soluble cargo encapsulation (including designer nanocages for biotechnology applications). These fabricated vesicles provide a new platform for studying the biophysically rich processes found within lipid-lipid and lipid-protein systems typically associated with cellular membranes

Diffusion of magnesium in LED structures with InGaN/GaN quantum wells at true growth temperatures 860-980°C of p-GaN

The results of an investigation of Mg diffusion in blue LED structures with InGaN/GaN quantum wells are presented for various growth temperatures of the p-GaN layer. The values of the diffusion coefficient estimated for true growth temperatures of 860, 910, and 980°C were 7.5·10–17, 2.8·10–16, and 1.2·10–15 cm2/s, respectively. The temperature values given in the work were measured on the surface of the growing layer in situ using a pyrometer. The calculated activation energy for the temperature dependence of the diffusion coefficient was 2.8 eV