RNA–protein binding kinetics in an automated microfluidic reactor

Microfluidic chips can automate biochemical assays on the nanoliter scale, which is of considerable utility for RNA–protein binding reactions that would otherwise require large quantities of proteins. Unfortunately, complex reactions involving multiple reactants cannot be prepared in current microfluidic mixer designs, nor is investigation of long-time scale reactions possible. Here, a microfluidic ‘Riboreactor’ has been designed and constructed to facilitate the study of kinetics of RNA–protein complex formation over long time scales. With computer automation, the reactor can prepare binding reactions from any combination of eight reagents, and is optimized to monitor long reaction times. By integrating a two-photon microscope into the microfluidic platform, 5-nl reactions can be observed for longer than 1000 s with single-molecule sensitivity and negligible photobleaching. Using the Riboreactor, RNA–protein binding reactions with a fragment of the bacterial 30S ribosome were prepared in a fully automated fashion and binding rates were consistent with rates obtained from conventional assays. The microfluidic chip successfully combines automation, low sample consumption, ultra-sensitive fluorescence detection and a high degree of reproducibility. The chip should be able to probe complex reaction networks describing the assembly of large multicomponent RNPs such as the ribosome

Electrothermal transport in biological systems : an analytical approach for electrokinetically-modulated peristaltic flow

A mathematical model is developed to investigate the combined viscous electro-osmotic flow and heat transfer in a finite length micro-channel with peristaltic wavy walls. The influence of Joule heating is included. The unsteady two-dimensional conservation equations for mass, momentum and energy conservation with viscous dissipation, heat absorption and electro-kinetic body force, are formulated in a Cartesian co-ordinate system. The Joule heating term appears as a quadratic function of axial electrical field in the energy conservation equation. The axial momentum and energy equations are coupled via the thermal buoyancy term. The peristaltic waves propagating along the micro-channel walls are simulated via a time-dependent co-sinusoidal wave function for the transverse vibration of the walls. Both single and train wave propagations are considered. Constant thermo-physical properties are prescribed and a Newtonian viscous model is employed for the fluid. The electrical field terms are rendered into electrical potential terms via the Poisson-Boltzmann equation, Debye length approximation and ionic Nernst Planck equation. The dimensionless emerging linearized electro-thermal boundary value problem is solved using integral methods. A parametric study is conducted to evaluate the impact of isothermal Joule heating term on axial velocity, temperature distribution, pressure difference, volumetric flow rate, skin friction and Nusselt number. The modification in streamline distributions with Joule heating and electro-osmotic velocity is also addressed to elucidate trapping bolus dynamics

ケモメカニカルシステムのための機能性ハイドロゲルアクチュエータの創製

関西大

HIGH PERFORMANCE PIEZOELECTRIC MATERIALS AND DEVICES FOR MULTILAYER LOW TEMPERATURE CO-FIRED CERAMIC BASED MICROFLUIDIC SYSTEMS

The incorporation of active piezoelectric elements and fluidic components into micro-electromechanical systems (MEMS) is of great interest for the development of sensors, actuators, and integrated systems used in microfluidics. Low temperature cofired ceramics (LTCC), widely used as electronic packaging materials, offer the possibility of manufacturing highly integrated microfluidic systems with complex 3-D features and various co-firable functional materials in a multilayer module. It would be desirable to integrate high performance lead zirconate titanate (PZT) based ceramics into LTCC-based MEMS using modern thick film and 3-D packaging technologies. The challenges for fabricating functional LTCC/PZT devices are: 1) formulating piezoelectric compositions which have similar sintering conditions to LTCC materials; 2) reducing elemental inter-diffusion between the LTCC package and PZT materials in co-firing process; and 3) developing active piezoelectric layers with desirable electric properties. The goal of present work was to develop low temperature fired PZT-based materials and compatible processing methods which enable integration of piezoelectric elements with LTCC materials and production of high performance integrated multilayer devices for microfluidics. First, the low temperature sintering behavior of piezoelectric ceramics in the solid solution of Pb(Zr0.53,Ti0.47)O3-Sr(K0.25, Nb0.75)O3 (PZT-SKN) with sintering aids has been investigated. 1 wt% LiBiO2 + 1 wt% CuO fluxed PZT-SKN ceramics sintered at 900oC for 1 h exhibited desirable piezoelectric and dielectric properties with a reduction of sintering temperature by 350oC. Next, the fluxed PZT-SKN tapes were successfully laminated and co-fired with LTCC materials to build the hybrid multilayer structures. HL2000/PZT-SKN multilayer ceramics co-fired at 900oC for 0.5 h exhibited the optimal properties with high field d33 piezoelectric coefficient of 356 pm/V. A potential application of the developed LTCC/PZT-SKN multilayer ceramics as a microbalance was demonstrated. The final research focus was the fabrication of an HL2000/PZT-SKN multilayer piezoelectric micropump and the characterization of pumping performance. The measured maximum flow rate and backpressure were 450 μl/min and 1.4 kPa respectively. Use of different microchannel geometries has been studied to improve the pumping performance. It is believed that the high performance multilayer piezoelectric devices implemented in this work will enable the development of highly integrated LTCC-based microfluidic systems for many future applications

The role of the cytoskeleton in volume regulation and beading transitions in PC12 neurites

We present investigations on volume regulation and beading shape transitions in PC12 neurites conducted using a flow-chamber technique. By disrupting the cell cytoskeleton with specific drugs we investigate the role of its individual components in the volume regulation response. We find that microtubule disruption increases both swelling rate and maximum volume attained, but does not affect the ability of the neurite to recover its initial volume. In addition, investigation of axonal beading --also known as pearling instability-- provides additional clues on the mechanical state of the neurite. We conclude that the initial swelling phase is mechanically slowed down by microtubules, while the volume recovery is driven by passive diffusion of osmolites. Our experiments provide a framework to investigate the role of cytoskeletal mechanics in volume homeostasis

Methods and Implementation of Fluid-Structure Interaction Modeling into an Industry-Accepted Design Tool

Fluid-structure interaction (FSI) modeling is a method by which fluid and solid domains are coupled together to produce a single result that cannot be produced if each physical domain was evaluated individually. The work presented in this dissertation is a demonstration of the methods and implementation of FSI modeling into an industry-appropriate design tool. Through utilizing computationally inexpensive equipment and commercially available software, the studies presented in this work demonstrate the ability for FSI modeling to become a tool used broadly in industry. To demonstrate this capability, the cases studied purposely include substantial complexity to demonstrate the stability techniques required for modeling the inherent instabilities of FSI models that contain three-dimensional geometries, nonlinear materials, thin-walled geometries, steep gradients, and transient behavior. The work also modeled scenarios that predict system failure and optimal design to extend service lifetime, thereby expanding upon current FSI literature. Four independent studies were performed, evaluating three separate modes of failure in FSI models, to demonstrate that FSI modeling is a viable design tool for widespread industry use. The first study validates FSI modeling techniques by comparing the results of a thin-walled FSI geometry model under hydrostatic forces with existing experimental data. The second study explored a parametric study that evaluated the factors influencing an FSI model containing a highly complex thermal-fluid fatigue model. This model involved dynamically changing temperature loads resulting in significant thermal expansion that led to material yielding and dynamic fatigue life. The third study evaluated a thermal-fluid conjugate heat transfer problem. The model was tuned, validated, and optimized for lifetime, and the validation of the system was performed using experimental data. The final study modeled the highly complex fluid and solid phenomena involved in a peristaltic pump where the goal was to demonstrate that the lifetime performance of the tubing could be altered by changing the geometry, material properties, and operating temperature. The model in this final study combined all the methods and techniques from the three earlier studies and applied them to a thin-walled tube geometry with nonlinear and temperature-dependent material properties to create large solid deformation and fluid motion

The Effect of Furnace Temperature and Precursor Concentration Ratio to The Characteristics of Nanocomposite ZnO-Silica

Zinc Oxide is a semiconductor with relatively non-toxic, cheap and abundant properties which can be applied to LEDs. ZnO colloids are unstable due to further chemical reactions and coagulation so the addition of silica is needed to inhibit the growth of ZnO. ZnO was synthesized using sol-gel method by hydrolyze zinc acetate dihydrate in ethanol solution. Silica colloids was prepared by dissolving waterglass in distilled water at a temperature of 60 °C then passed into cation resin that has been activated using 2N HCl for ion exchange with Na+ to H+. In this study, the spray drying method was used to produce ZnO-silica nanocomposite. Morphological characterization of particles formed was analyzed using Scanning Electrostatic Microscope (SEM) (Zeiss Evo MA LS, Cambridge, England). X-Ray Diffraction (XRD) (Cu-Kα 1.54 A0, 40 kV, 30 mA, X’pert Pro, PAN alytical, Netherlands) and Fourier Transform Infrared (FTIR) (Therniscientific Nicolet iS10, US) were used to analyze the crystallinity and group functionalization, respectively. The results show that more particles are formed on 10% concentration volume of ZnO colloids rather than 5%

Design Considerations in the Use of Glauber Salt for Energy Storage

Various design concepts for the utilization of the latent heat of Glauber salt at temperatues between 25 degrees C and 50 degrees C were studied. Consideration was given to system economics and what particular heat storage system if perfected would be most cost effective. The problems of limited crystal size and heat transfer into and out of salt crystals is discussed. Crystal size is affected by the degree of agitation the salt solution experiences during the salt cooling process. Consequently, crystal size was moderated in a favorable way by introducing air bubbles at the bottom of the salt container. As the bubbles rise a mixing action occurs which limits crystal size and helps prohibit the accumulation of an anhydrous sudge that settles out of solution in the freezing-thawing process