Showing papers on "Fluidics published in 2008"

Digital microfluidic design and optimization of classic and new fluidic functions for lab on a chip systems

Abstract: This paper deals with microfluidic studies for lab-on-a-chip development. The first goal was to develop microsystems immediately usable by biologists for complex protocol integrations. All fluid operations are performed on nano-liter droplet independently handled solely by electrowetting on dielectric (EWOD) actuation. A bottom-up architecture was used for chip design due to the development and validation of elementary fluidic designs, which are then assembled. This approach speeds up development and industrialization while minimizing the effort in designing and simplifying chip-fluidic programming. Dispensing reproducibility for 64 nl droplets obtained a CV below 3% and mixing time was only a few seconds. Ease of the integration was demonstrated by performing on chip serial dilutions of 2.8-folds, four times. The second part of this paper concerns the development of new innovative fluidic functions in order to extend EWOD-actuated digital fluidics’ capabilities. Experiments of particle dispensing by EWOD droplet handling are reported. Finally, work is shown concerning the coupling of EWOD actuation and magnetic fields for magnetic bead manipulation.

Microfluidics for Miniaturized Laboratories on a Chip

Abstract: Microfluidic systems promise solutions for high throughput and highly specific analysis for biology, medicine and chemistry while consuming only tiny amounts of reactants and space. On these lab-on-a-chip platforms often multiple physical effects such as electrokinetic, acoustic or capillary phenomena from various disciplines are exploited to gain the optimal functionality. The fluidics on these small length scales differ significantly from our experience of the macroscopic world. In this Review we survey some of the approaches and techniques to handle minute amounts of fluid volumes in microfluidic systems with special focus on surface acoustic wave driven fluidics, a technique developed in our laboratory. Here, we outline the basics of this technique and demonstrate, for example, how acoustic mixing and fluid actuation is realized. Furthermore we discuss the interplay of different physical effects in microfluidic systems and illustrate their usefulness for several applications.

Green-tape ceramics. New technological approach for integrating electronics and fluidics in microsystems

Abstract: The miniaturization of analytical systems for different applications is currently a very active field of research. The inherent advantages of micro total analysis systems (μTASs) are well known. Although the fluidic platforms and the development of suitable miniaturized detection systems have been studied extensively, the integration in a single substrate of the electronics that is needed to manage the whole system using a single technology is still a sizeable challenge. In this overview, we discuss the role of the low-temperature co-fired ceramics (LTCC) as a potential alternative for miniaturizing analytical systems, since a single technology can easily combine fluidics and electronics to produce a number of novel chemical microanalyzers.

Fluidic connectors and microfluidic systems

Abstract: Fluidic connectors, methods, and devices for performing analyses (e.g., immunoassays) in microfluidic systems are provided. In some embodiments, a fluidic connector having a fluid path is used to connect two independent channels formed in a substrate so as to allow fluid communication between the two independent channels. One or both of the independent channels may be pre-filled with reagents (e.g., antibody solutions, washing buffers and amplification reagents), which can be used to perform the analysis. These reagents may be stored in the channels of the substrate for long periods amounts of time (e.g., 1 year) prior to use.

Miniaturized thermal flow sensor with planar-integrated sensor structures on semicircular surface channels

Abstract: A calorimetric miniaturized flow sensor was realized with a linear sensor response measured for water flow up to flow rates in the order of 300 nl min-1. A versatile technological concept is used to realize a sensor with a thermally isolated freely suspended silicon-rich silicon-nitride microchannel directly below the substrate surface. The microchannel concept allows for the planar integration of sensor structures in close proximity to the fluid, while chemical-resistant fluidic connections can be made directly on top of the microchannel, without introducing large dead-volumes. The realized flow sensor consists of a microchannel with low hydraulic resistance and 4.5 nl total fluid volume. A pressure driven flow setup was used to force water through the microchannel, measuring output sensitivity in the order of 0.2 μV/(nl min-1) for flows up to 300 nl min-1. The measured sensor output is in close agreement with results obtained from both a detailed and an approximate numerical model of the sensor.

Device and methods of detection of airborne agents

Abstract: Provided are methods, devices and systems that utilize free-surface fluidics and SERS for analyte detection with high sensitivity and specificity. The molecules can be airborne agents, including but not limited to explosives, narcotics, hazardous chemicals, or other chemical species. The free-surface fluidic architecture is created using an open microchannel, and exhibits a large surface to volume ratio. The free-surface fluidic interface can filter interferent molecules, while concentrating airborne analyte molecules. The microchannel flow enables controlled aggregation of SERS-active probe particles in the flow, thereby enhancing the detector's sensitivity.

Systems and Methods for Separating Particles and/or Substances from a Sample Fluid

Abstract: Systems and methods for separating particles and/or toxins from a sample fluid. A method according to one embodiment comprises simultaneously passing a sample fluid and a buffer fluid through a chamber such that a fluidic interface is formed between the sample fluid and the buffer fluid as the fluids pass through the chambers the sample fluid having particles of interest therein; applying a force to the fluids for urging the particles of interest to pass through the interface into the buffer fluid; and substantially separating the buffer fluid from the sample fluid.

Optofluidics technology based on colloids and their assemblies

Abstract: Optofluidic technology is believed to provide a breakthrough for the currently underlying problems in microfluidics and photonics/optics by complementary integration of fluidics and photonics. The key aspect of the optofluidics technology is based on the use of fluidics for tuning the optical properties and addressing various functional materials inside of microfluidic channels which have build-in photonic structures. Through the optofluidic integrations, fluidics enhances the controllability and tunability of optical systems. In particular, colloidal dispersion gives novel properties such as photonic band-gaps and enhanced Raman spectrum that conventional optofluidic devices cannot exhibit. In this paper, the state of the art of the colloidal dispersions is reviewed especially for optofluidic applications. From isolated singlet colloidal particles to colloidal clusters, their self-organized assemblies lead to optical manipulation of the photonic/optical properties and responses. Finally, we will discuss the prospects of the integrated optofluidics technology based on colloidal systems.

A microfluidic chip for and a method of handling fluidic droplets

Abstract: A micro fluidic chip ( 100 ) for handling fluidic droplets ( 101 ), the micro fluidic chip ( 100 ) comprising a plurality of electrodes ( 103 ) being arranged in a Back End of the Line portion ( 104 ) of the microfluidic chip ( 100 ), and a control unit ( 106 ) adapted for controlling electric potentials of the plurality of electrodes ( 103 ) to generate electric forces for moving the fluidic droplets ( 101 ) along a predefined trajectory.

Elemental analysis using micro laser-induced breakdown spectroscopy (microLIBS) in a microfluidic platform.

Abstract: We present here a non-labeled, elemental analysis detection technique that is suitable for microfluidic chips, and demonstrate its applicability with the sensitive detection of sodium (Na). Spectroscopy performed on small volumes of liquids can be used to provide a true representation of the composition of the isolated fluid. Performing this using low power instrumentation integrated with a microfluidic platform makes it potentially feasible to develop a portable system. For this we present a simple approach to isolating minute amounts of fluid from bulk fluid within a microfluidic chip. The chip itself contains a patterned thin film resistive element that super-heats the sample in tens of microseconds, creating a micro-bubble that extrudes a micro-droplet from the microchip. For simplicity a non-valved microchip is used here as it is highly compatible to a continuous flow-based fluidic system suitable for continuous sampling of the fluid composition. We believe such a non-labeled detection technique within a microfluidic system has wide applicability in elemental analysis. This is the first demonstration of laser-induced breakdown spectroscopy (LIBS) as a detection technology in conjunction with microfluidics, and represents first steps towards realizing a portable lower power LIBS-based detection system.

Self-sealed circular channels for micro-fluidics

Abstract: The paper elaborates a technique to realize fully circular self-sealed channels with diameter varying from few micrometers to less than 100 nm using standard silicon processes like trench formation, doped silicon oxide filling and thermal cycle for its re-flow. The integration of the channels with the fluidic reservoirs, their packaging with input and output ports for fluids and external electrodes is also presented. Such a chip is used as lateral patch clamp to record the electrical activity of the cells.

Electric field control and analyte transport in Si/SiO2 fluidic nanochannels.

Abstract: This article presents an analysis of the electric field distribution and current transport in fluidic nanochannels fabricated by etching of a silicon chip. The channels were overcoated by a SiO2 layer. The analysis accounts for the current leaks across the SiO2 layer into the channel walls. Suitable voltage biasing of the Si substrate allows eliminating of the leaks or using them to modify the potential distribution of the fluid. Shaping the potential in the fluid can be utilized for solute focusing and separations in fluidic nanochannels.

Particle patterning using fluidics and electric fields

Abstract: Electric-field manipulation of micro-particles in suspension can create patterns via a number of particle forces and fluid flows. These effects are assessed for their suitability for down-scaling to form nano-patterns such as may be incorporated into structured nano-composites. Consideration is given not only to the assembly of field-aligned chains or wires, but also to methods that can give cross-field assembly and even 2-D patterns or crystals. Dielectrophoresis is often the dominant driving force behind particle assembly, but other dipole-dipole interactions and also electrically-driven fluid flows are increasingly recognized as significant or dominant. Orientation of non-spherical particles in frequency-selectable directions is also possible. Estimates for the threshold field strengths required for using these effects to handle nano-particles are considered. Finally the use of media with modified permittivity to increase the field-induced forces or to optimize the selectivity of particle incorporation is discussed.

Computational Fluid Dynamic Modeling of a Fluidic Actuator for Flow Control

Abstract: The development of a computer model demonstrating the switching dynamics of the flow within the actuator body has been accomplished. The model has shown good correlation to experimental data taken in the lab using rapid prototyped test articles and switching control with miniature pneumatic operator valves. The computer model is being used to refine the design of the fluidic body in order to improve the speed of the switching characteristics and determine the optimum location and magnitude of the control force. The momentum-flux ratio between the control jet and the inlet flow has been identified as a controlling parameter in order to produce reliable switching for a bistable nozzle flow. The maximum switching frequency for the conditions and test article considered in this report for one cycle was determined both experimentally and computationally to be 250 Hz.

Self-organized twinning of actuated particles for microfluidic pumping

Abstract: The motion of monodisperse particle ensembles in fluidic channels actuated by axial magnetic or gravitation forces is studied. Interactions between particles, fluid, and nearby walls induce unforeseen self-organization phenomena. Superparamagnetic microparticles aligned on a channel axis successively organize toward a stable polytwin system under constant force conditions. In the absence of repelling particle interactions, full contact twinning is observed for particles driven by gravity. The mechanisms of successive twinning and spacing regulation are explained by a one-dimensional model based on the axis flow profile. Related performance enhancements for particle based microfluidic pumping are discussed.

System, method and apparatus for vectoring nozzle exhaust plume with external actuation

Abstract: A vectoring nozzle with external actuation generates thrust vectoring by applying mechanical or fluidic actuation, or both, on the nozzle deck, external sidewalls, and/or air vehicle aft body to produce changes in the aft body flowfield and/or exhaust plume. An external mechanical sidewall may be integrated into a nozzle deck or side walls without the need for engine bleed to supply fluid injectors. An external fluidic vectoring system uses injectors or plasma devices located aft of the nozzle exit to vector the exhaust plume with no external moving parts. Elements of both mechanical and fluidic systems may be combined for a given application.

Fluidic Interconnects in Integrated Liquid Cooling Systems for 3-D Stacked TSV Modules

Abstract: In this paper, an integrated liquid cooling system for 3D stacked modules with high power dissipation is proposed. The fluidic interconnects in this system are elaborated and the sealing technique for different fluid interfaces is discussed. Meanwhile the pressure drop for each part of the system is analyzed. The optimized fluidic interconnects minimizing the pressure drop has been designed and fabricated, and the compact system is integrated. In line with the fluidic interconnect design and analysis, an experimental setup for hydraulic characterization of the integrated cooling system is established. The pressure drop for different fluidic interconnects in this system have been measured and compared with the analyzed results.

Blood cell counting by means of impedance measurements in a microsystem device

Abstract: This paper presents an innovative, portable and low power blood cell counter, based on micro-electro-mechanical-systems (MEMS) technology. It was realized by designing and developing a custom impedance measurement circuit, which drives an electro-fluidic microsystem, providing a parallel, multi-channel Coulter counter. A method for a reliable, easy, and low-cost interfacing to such kind of micro-devices, allowing both fluidic and electric coupling, is also shown. Preliminary experiments led to promising results: fluidics works properly without leakages or clogging. Electrodes show good stability with current (in terms of adhesion), and measured channel impedances are satisfyingly low (30kΩ for a cubic Coulter orifice, side 10μm). Finally, we present a possible extension of the setup, based on a dual-characteristic, electro-optical counting.

Electrohydrodynamic-mediated dielectrophoretic separation and transport based on asymmetric electrode pairs.

Abstract: This paper presents a system for continuous separation and transport of micron and submicron particles in fluidic environment based on dielectrophoretic fractionation in concert with AC electrothermal (AC ET)-induced fluidic pumping action. In this system, high frequency AC signals are used to energize asymmetric electrode pairs. AC ET-driven fluidic pumping is utilized as an alternative to the commonly used external pressure-driven fluid flow. Distinct collection sites for negative-dielectrophoretic and positive-dielectrophoretic particle populations are identified. The coupling effects of dielectrophoretic force and viscous drag from AC ET fluid flow on particle motions are investigated theoretically and numerically. We demonstrate that these two forces can be efficiently coupled to achieve continuous separation and transport of particle mixture in a fluidic medium when the dielectric properties of the particles and the fluidic environment are different. The combination of dielectrophoretic separation and AC ET pumping function provides a promising approach to further miniaturize and integrate these mechanisms into lab-on-chip devices.

Modelling and robust control of fluidic thrust vectoring and circulation control for unmanned air vehicles

Abstract: This paper presents actuator models for fluidic thrust vectoring and circulation control and they are used in the design of a robust controller for an unmanned air vehicle. The pitching and rolling moments for the aircraft are produced through the use of a co-flow fluidic thrust vectoring arrangement at the wing trailing edges. Experimental results for the co-flow actuators are used to derive mathematical models and their performance is compared with conventional control surfaces. For the controller design, nonlinear dynamic models are approximated by a simplified linear parameter varying (LPV) model. The polytopic nature of the controller is exploited to reformulate the LPV controller design problem into a m-synthesis problem. The LPV controllers exhibit superior stability properties over the entire operating region, when compared to conventional gain-scheduling schemes.

Fabrication of the cyclical fluid channel using the surface acoustic wave actuator and continuous fluid pumping in the cyclical fluid channel

Abstract: A surface acoustic wave (SAW) device has been reported as a micro fluid device such as a pump of a water droplet so far (Renaudin et al. in μTAS, pp 599–601, 2004, 1:551–553, 2005; Sritharan et al. in Appl Phys Lett 88:054102, 2006; Wixforth in Anal Bioanal Chem 379:982–991, 2004; Yamamoto et al. in μTAS, pp 1072–1074, 2005). The SAW device is an interdigital transducer (IDT) fabricated on the piezoelectric substrate only. IDTs are advantageous in terms of integration, miniaturization, free position setting on the substrate and simple fabrication process because of their simple structure. Therefore, the SAW device is easy to apply to integrated chemical system such as lab-on-a-chip. The SAW drives the liquid homogenously by the transmission of surface vibrations of the substrate. Thus, both ends of the channel for pressure loading are not necessary to pump the liquid by using the SAW. The SAW can pump the liquid in both of a closed channel and an opened channel, although continuous flow pumping using an external pump is difficult for no loading pressure in the closed fluid channel. In this paper, we proposed and fabricated the micro fluid devices combined cyclical fluid channel and SAW actuator for liquid pumping. This device is fabricated on a piezoelectric substrate (LiNbO3) with UV photolithography and wet etching. Structure material of cyclical fluid channel is epoxy photoresist SU-8 100. Then, it is demonstrated to continuous flow pumping and reciprocal flow pumping in the channel. As a result of optimization of a SAW pump’s structural parameter, 32.5, 71.3 and 108.0 mm/s are achieved in the 500, 1,000 and 2,000 μm channel width as a maximum flow velocity.

Hydraulic parameter model for design of fluidics downhole boost compressor

Abstract: The theoretical models for hydraulic parameters of fluidics downhole boost compressor were set up with the fluid mechanics network method on the basis of structure and work principle of the first generation of downhole boost compressor.According to the hydraulic models,the flow rate and pressure of the first generation of boost compressor were computed and analyzed.Some innova- tive approaches were presented to resolve the problem existing in the first generation of boost compressor by increasing the flow area of fluidics nozzle to decrease pressure drop and erosion attack,adding a new flow path in order to improve boosting effect of the sec- ond piston bore,connecting a bypass valve in parallel with throttle valve to set a partial flow and regulate pressure drop.The above innovative approaches are the theoretical base of the second generation of boost compressor and have important roles on decreasing the pressure drop and increasing work performance of boost compressor.

Piezoelectric β-PVDF polymer films as fluid acoustic microagitator

Abstract: The main objective of this paper is to describe a fluidic acoustic microagitation system based on a Poly(Vinylidene Fluoride) polymer. This system benefits from the high piezoelectric properties presented by the beta-phase of the polymer (beta-PVDF) converting an electrical signal into acoustics vibrations. These vibrations can be used in microfluid systems to enhance fluids mixture and reaction. Experimental results regarding the influence of the area and thickness of the piezoelectric beta-PVDF polymer on the velocity of reaction of some biological fluids are presented. Moreover, the incorporation of the beta-PVDF underneath microfluidic structures of a lab-on-a-chip with an automatic electronic control is referred.

Fully Integrated Bridge-type Anemometer in LTCC-based Microfluidic Systems

Abstract: A thick film anemometer for in situ control of the flow rate in fluidic systems was designed, manufactured and characterized. The sensor is integrated in a retention modulus consisting of Low Temperature Cofired Ceramics (LTCC). These materials allow the cost-effective realisation of fluidic microsystems with integrated electronics. The challenge of the work is to design an anemometer under the exclusive use of thick film technologies. The necessity to trim resistors causes the external use of relevant pastes. Therefore, the use inside of a closed fluidic system requires the leak of process gases and, at the same time, a maximal heat-insulating of the sensor element from the substrate. Free-standing elements necessitate the control of stress due to shrinking mismatch, TCE mismatch, density gradients and deformation during the lamination. In the presented solution, embossed flue channels prevent blow forming on a free-standing bridge. The anemometer has a linear sensor characteristic for flow rates up to 0.1 ml/min. The layout guarantees that the fluid gets only in contact with the basic ceramic material, which is compatible with a wide range of biological substances. Therefore the sensor is applicable in contact with cell fluids or PCRreagents.

System and apparatus for vectoring nozzle exhaust plume from a nozzle

Abstract: A vectoring nozzle with external actuation generates thrust vectoring by applying mechanical or fluidic actuation, or both, on the nozzle deck, external sidewalls, and/or air vehicle aft body to produce changes in the aft body flowfield and/or exhaust plume. An external mechanical sidewall may be integrated into a nozzle deck or side walls without the need for engine bleed to supply fluid injectors. An external fluidic vectoring system uses injectors or plasma devices located aft of the nozzle exit to vector the exhaust plume with no external moving parts. Elements of both mechanical and fluidic systems may be combined for a given application.

Fluidic device for controlled handling of liquids, and fluidic system with a fluidic device

Abstract: A fluidic device for conveying or determining the quantity of a liquid flowing from a fluidic device inlet (2) to a fluidic device outlet (4) along a fluid path running in a direction of flow (6) has a fluidic element (16) which is movable within the fluid path between a first position to a second position located in the direction of flow (6) downstream of the first position, and a fluidic device housing (8) enclosing the fluid path. The fluidic element (16) has a through flow opening (18) which has a first flow resistance when the fluidic element (16) moves from the first position (22) into the second position (24) and which has a second flow resistance differing from the first flow resistance when the fluidic element (16) moves from the second position (24) into the first position (22). The fluidic element (16) and the fluidic device housing (8) are designed in such a manner that the fluidic element is movable from the second position (24) to the first position (22) by means of a contactless drive.

Microfluidic device and methods for droplet generation and manipulation

Abstract: Methods and microfluidic devices for generating and manipulating sample droplets, wherein the devices comprise, a plurality of fluid channels, at least one of which is a sample channel for carrying a fluidic sample material, that is in fluid communication with the carrier fluid channel via an orifice; and an actuated flow interrupter adapted to force a predetermined amount of the sample fluid from the sample channel through the orifice into the carrier fluid channel.

Numerical Analysis of Elastomeric Fluidic Microvalves

Abstract: We present a finite element model of polydimethylsiloxane (PDMS) fluidic microvalves. A valve is fabricated by assembling two patterned layers in a two-channel crossed architecture. The valve closes as a consequence of the motion of the interlayer membrane. The membrane is deformed by the pressure of the actuation fluid, flowing in one of the two channels. By using a soft rubber material model, we setup a numerical model of the microvalve and validate it against experiments. The numerical model allows to evaluate the mechanical engagement of commonly used microvalve architectures and to analyze the performance of alternative geometries.