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Showing papers on "Microfluidics published in 2001"


Journal ArticleDOI
TL;DR: In this article, the authors present new fabrication challenges and finding new applications in biology, chemistry, and materials science for handling nanoliter quantities of fluids, which is a new fabrication challenge.
Abstract: Devices for handling nanoliter quantities of fluids are creating new fabrication challenges and finding new applications in biology, chemistry, and materials science.

646 citations


Journal ArticleDOI
TL;DR: This device demonstrates the most sensitive PCR possible in a microfabricated device and will also facilitate single-cell and single-molecule studies to expose the genetic variation underlying ensemble sequence and expression averages.
Abstract: Stochastic PCR amplification of single DNA template molecules followed by capillary electrophoretic (CE) analysis of the products is demonstrated in an integrated microfluidic device. The microdevice consists of submicroliter PCR chambers etched into a glass substrate that are directly connected to a microfabricated CE system. Valves and hydrophobic vents provide controlled and sensorless loading of the 280-nL PCR chambers; the low volume reactor, the low thermal mass, and the use of thin-film heaters permit cycle times as fast as 30 s. The amplified product, labeled with an intercalating fluorescent dye, is directly injected into the gel-filled capillary channel for electrophoretic analysis. Repetitive PCR analyses at the single DNA template molecule level exhibit quantized product peak areas; a histogram of the normalized peak areas reveals clusters of events caused by 0, 1, 2, and 3 viable template copies in the reactor and these event clusters are shown to fit a Poisson distribution. This device demon...

613 citations



Journal ArticleDOI
TL;DR: In this paper, a micro-capillary electrophoresis (μ-CE) device for DNA separation and detection on polymethylmethacrylate (PMMA) substrates using novel microfabrication methods is described.
Abstract: Design and fabrication of microfluidic devices on polymethylmethacrylate (PMMA) substrates for analytical chemistry and biomedical-related applications using novel microfabrication methods are described. The image of microstructures is transferred from quartz master templates possessing the inverse image of the devices to plastic plates by using hot embossing methods. The microchannels on quartz master templates are formed by the combination of metal etch mask and wet chemical etching of a photomask blank. The micromachined quartz templates can be used repeatedly to replicate cheap and disposable plastic devices. The reproducibility of the hot embossing method is evaluated using 10 channels on different PMMA plastics. The relative standard deviation of the channel profile on the plastic chips is less than 1%. In this study, the PMMA microfluidic chips have been demonstrated as a microcapillary electrophoresis (μ-CE) device for DNA separation and detection. The capability of the fabricated chip for electrophoretic injection and separation is characterized via the analysis of DNA fragments ∅X-174-RF Hae III digest. Experimental results indicate that all of the 11 DNA fragments of the size marker could be identified in less than 2 min with relative standard deviations less than 0.4 and 8% for migration time and peak area, respectively. Moreover, with the use of a near-infrared (IR) dye, fluorescence signals of the higher molecular weight fragments (>603 bp in length) could be detected at total DNA concentrations as low as 0.1 μg/ml. In addition to DNA fragments ∅X-174-RF Hae III digest, DNA sizing of hepatitis C viral (HCV) amplicon is also achieved using microchip electrophoresis on PMMA substrates.

295 citations


Journal ArticleDOI
TL;DR: In this paper, the design of a polymer-based microfluidic compact disk (CD) platform is presented for flow sequencing, cascade micro-mixing, and capillary metering by balancing the centrifugal force and the capillary force.
Abstract: In this paper, the design of a polymer based microfluidic compact disk (CD) platform is presented. Several microfluidic functions such as flow sequencing, cascade micro-mixing, and capillary metering can be integrated into the CD by balancing the centrifugal force and the capillary force. These functions are demonstrated experimentally. For flow sequencing, a two-point calibration design is used as an example to show how the release and flow of fluids can be precisely controlled by the rotation speed of the CD. For cascade micro-mixing, a typical application is reconstituting lyophilized protein. A simple metering technique based on bubble snap-off in the two-phase flow is also described.

232 citations


Journal ArticleDOI
TL;DR: The results show that the valve-less micropump successfully pumps fluids within the viscosity range 0.001–0.9 Ns/m2 and is self-priming and insensitive to particles and bubbles present in the pumped media.
Abstract: The suitability of valve-less micropumps in biochemistry is shown. Fluids encountered in various biochemical methods that are problematic for other micropumps have been pumped with good performance. The micropump is self-priming and insensitive to particles and bubbles present in the pumped media. The results show that the valve-less micropump successfully pumps fluids within the viscosity range 0.001–0.9 Ns/m2. The micropump is not sensitive to the density, ionic strength or pH of the pumped media. Effective pumping of solutions containing beads of different sizes was also demonstrated. Living cells were pumped without inducing cell damage and no cell adhesion within the pump chamber was found.

211 citations


Journal ArticleDOI
TL;DR: A 2-D DNA array is used to detect a 20-fmol sample of in vitro transcribed RNA from the uidA gene of a transgenic Arabidopsis thaliana plant and it is shown that this array fabrication method can be used for fluorescence measurements on chemically modified gold surfaces.
Abstract: Microfluidic channels fabricated from poly(dimethylsiloxane) (PDMS) are employed in surface plasmon resonance imaging experiments for the detection of DNA and RNA adsorption onto chemically modified gold surfaces. The PDMS microchannels are used to (i) fabricate “1-D” single-stranded DNA (ssDNA) line arrays that are used in SPR imaging experiments of oligonucleotide hybridization adsorption and (ii) create “2-D” DNA hybridization arrays in which a second set of PDMS microchannels are placed perpendicular to a 1-D line array in order to deliver target oligonucleotide solutions. In the 1-D line array experiments, the total sample volume is 500 μL; in the 2-D DNA array experiments, this volume is reduced to 1 μL. As a demonstration of the utility of these microfluidic arrays, a 2-D DNA array is used to detect a 20-fmol sample of in vitro transcribed RNA from the uidA gene of a transgenic Arabidopsis thaliana plant. It is also shown that this array fabrication method can be used for fluorescence measurements ...

184 citations


Proceedings ArticleDOI
TL;DR: In addition to bioactive fluid dispensing, ink-jet based microdispensing allows integration of features (electronic, photonic, sensing, structural, etc.) that are not possible, or very difficult, with traditional photolithographic-based MEMS fabrication methods as mentioned in this paper.
Abstract: Applications of microfluidics and MEMS (micro-electromechanical systems) technology are emerging in many areas of biological and life sciences. Non-contact microdispensing systems for accurate, high-throughput deposition of bioactive fluids can be an enabling technology for these applications. In addition to bioactive fluid dispensing, ink-jet based microdispensing allows integration of features (electronic, photonic, sensing, structural, etc.) that are not possible, or very difficult, with traditional photolithographic-based MEMS fabrication methods.Our single fluid and mutlifluid (MatrixJetT) piezoelectric microdispensers have been used for spot synthesis of peptides, production of microspheres to deliver drugs/biological materials, microprinting of biodegradable polymers for cell proliferation in tissue engineering requirements, and spot deposition for DNA, diagnostic immunoassay, antibody and protein arrays. We have created optical elements, sensors, and electrical interconnects by microdeposition of polymers and metal alloys. We have also demonstrated the integration of a reverse phase microcolumn within a piezoelectric dispenser for use in the fractionation of peptides for mass spectrometer analysis.

151 citations


Journal ArticleDOI
TL;DR: In this article, the fabrication and characterization of a microfluidic device for capillary electrophoresis applications is presented, which consists of a glass chip which contains a single separation channel as well as an integrated conductivity detection cell.
Abstract: The fabrication and characterization of a microfluidic device for capillary electrophoresis applications is presented. The device consists of a glass chip which contains a single separation channel as well as an integrated conductivity detection cell. In contrast to most microfluidic glass devices the channels are not wet etched in HF but machined by the newly developed micro powder-blasting technique which allows the creation of microstructures below 100 µm, and additionally makes parallel hole machining at very low costs outside the cleanroom environment possible [1, 2]. The integration of the conductivity detector was achieved by leading two thin-film metal electrodes inside the separation channel. For rapid sample injection the chip is mounted inside an autosampler-based capillary electrophoresis platform. The detection electrodes for conductivity detection are read out by lock-in amplifier electronics. First measurements show the successful separation of various ions in the sub-millimeter range.

118 citations


Journal ArticleDOI
TL;DR: The integrated circuit (IC) biochip and the immunoassay is evaluated for assays performed both by conventional laboratory means followed by detection with the IC biochip, and through the use of the microfluidics system for on-chip detection.
Abstract: This work demonstrates the detection of E. coli using a 2-dimensional photosensor array biochip which is efficiently equipped with a microfluidics sample/reagent delivery system for on-chip monitoring of bioassays. The biochip features a 4 x 4 array of independently operating photodiodes that are integrated along with amplifiers, discriminators and logic circuitry on a single platform. The microfluidics system includes a single 0.4 mL reaction chamber which houses a sampling platform that selectively captures detection probes from a sample through the use of immobilized bioreceptors. The independently operating photodiodes allow simultaneous monitoring of multiple samples. In this study the sampling platform is a cellulosic membrane that is exposed to E. coli organisms and subsequently analyzed using a sandwich immunoassay involving a Cy5-labeled antibody probe. The combined effectiveness of the integrated circuit (IC) biochip and the immunoassay is evaluated for assays performed both by conventional laboratory means followed by detection with the IC biochip, and through the use of the microfluidics system for on-chip detection. Highlights of the studies show that the biochip has a linear dynamic range of three orders of magnitude observed for conventional assays, and can detect 20 E. coli organisms. Selective detection of E. coli in a complex medium, milk diluent, is also reported for both off-chip and on-chip assays.

91 citations


Journal ArticleDOI
TL;DR: An organic feedback scheme that merges microfluidics and responsive materials to address several limitations of current microfluidity systems is presented and feedback control of the output pH in a completely organic system is demonstrated.
Abstract: In this paper we present an organic feedback scheme that merges microfluidics and responsive materials to address several limitations of current microfluidic systems. By using in situ fabrication and by taking advantage of microscale phenomena (e.g., laminar flow, short diffusion times), we have demonstrated feedback control of the output pH in a completely organic system. The system autonomously regulates an output stream at pH 7 under a range of input flow conditions. A single responsive hydrogel component performs the functionality of traditional feedback system components. Vertically stacked laminar flow is used to improve the time response of the hydrogel actuator. A star shaped orifice is utilized to improve the flow characteristics of the membrane/orifice valve. By changing the chemistry of the hydrogel component, the system can be altered to regulate flow based on hydrogels sensitive to temperature, light, biological/molecular, and others.

Journal ArticleDOI
TL;DR: Innovative techniques for manipulating fluids and samples in microdevices are opening new frontiers as discussed by the authors, and they have been shown to be useful in a variety of applications, such as medical applications.
Abstract: Innovative techniques for manipulating fluids and samples in microdevices are opening new frontiers.

Proceedings ArticleDOI
01 Jan 2001
TL;DR: In this paper, two types of electrowetting principles -regular electrowetting (EW) and electrowets on dielectric (EWOD) are applied for microactuation and correspondingly designed test devices for addressable micro liquid handling.
Abstract: This paper presents two types of electrowetting principles - regular electrowetting (EW) and electrowetting on dielectric (EWOD), applied for microactuation and correspondingly designed test devices for addressable micro liquid handling. The devices demonstrated sequential microactuation of liquid on electrodes with (EWOD) or without (EW) hydrophobic coating on them.

Proceedings ArticleDOI
24 Aug 2001
TL;DR: In this paper, a liquid droplet mixer is proposed to enable mixing of the samples and reagents for chemical and biological analysis in micro total analysis systems (/spl mu/TAS).
Abstract: We present a liquid droplet mixer to enable mixing of the samples and reagents for chemical and biological analysis in micro total analysis systems (/spl mu/TAS). The droplets in the mixer are actuated based on electrowetting phenomenon. The actuator comprises of two parallel glass plates between which the droplet is actuated on a planar array of electrodes. Mixing of liquid channels in microfluidic systems has been demonstrated for continuous flow systems where the mixing is diffusion-limited due to the laminar flow of liquids, requiring very long, thin channels. In the present paper, mixing is performed on discrete droplets of liquid. When two droplets are brought together, depending on the velocity of the moving droplets, surface tension, viscosity, electrode activation, and volume among other factors, turbulence is created which aids in mixing. The mixing is not limited by diffusion and enhanced by transport. The mixing experiments are performed between fluorescein and plain water droplets whose individual volume is 1.75 /spl mu/l. Mixing is visualized with a 2-CCD camera setup to observe both the top and side views, with appropriate filters to capture fluorescence. We observed that it takes about 60 seconds for two droplets of 1.75 /spl mu/l each to mix when their surface tensions are different and it takes about 90 seconds when the two droplets have similar surface tensions. The present mixer stands apart from any current conventional micromixers in that the mixing times occupies much lesser area, mixing does not need any specific architecture on the chip and can be performed on any transport electrodes dynamically assigned to mixing.

Journal ArticleDOI
TL;DR: In the new configuration, biosensor experiments can be conducted without the usual constraints in the surface contact time that are correlated with sample volume and mass transport rate, which can translate to improved detection limits for slow reactions and can facilitate kinetic and thermodynamic binding studies.
Abstract: The efficient delivery of sample to surface-immobilized sites is a key element in biosensing. For a surface plasmon resonance (SPR) biosensor, this has been addressed by constant flow through a mic...

Patent
02 Nov 2001
TL;DR: In this article, a method and device for routing, mixing, or reacting droplets or liquid microstreams along the surface of a flat substrate is presented, which can be used for microfluidic applications or as a surface reactor or biosensor, among other applications.
Abstract: The invention is directed to a method and device for routing, mixing, or reacting droplets or liquid microstreams along the surface of a flat substrate. The flow of liquid microstreams or microdroplets along designated pathways is confined by chemical surface patterning. Individually addressable heating elements, which are embedded in the substrate, can be used to generate flow via thermocapillary effects or to trigger or quench chemical reactions. The open architecture allows the liquid to remain in constant contact with the ambient atmosphere. The device can be used for microfluidic applications or as a surface reactor or biosensor, among other applications.

Journal ArticleDOI
TL;DR: The design and manufacture of self-contained microfluidic cartridges for the extraction of small molecules from a mixture of small and large molecules by diffusion is demonstrated and computational fluid dynamics models are shown that demonstrate the tuning of various micro fluidic parameters to optimize separation performance.
Abstract: Microfluidic structures for the generation of laminar fluid diffusion interfaces (LFDIs) for sample preparation and analysis are discussed. Experimental data and the results of fluid modeling are shown. LFDIs are generated when two or more streams flow in parallel in a single microfluidic structure without any mixing of the fluids other than by diffusion of particles across the diffusion interface. It has been shown that such structures can be used for diffusion-based separation and detection applications. The method has been applied to DNA desalting, the extraction of small proteins from whole blood samples, and the detection of various constituents in whole blood, among other examples. In this paper the design and manufacture of self-contained microfluidic cartridges for the extraction of small molecules from a mixture of small and large molecules by diffusion is demonstrated. The cards are operated without any external instrumentation, and use hydrostatic pressure as the driving force. The performance of the cartridges is illustrated by separating fluorescein from a mixture of fluorescein and dextran of molecular weight 2×106. In a single pass, 98.6% of dextran was retained in the product whereas 43.1% of fluorescein was removed. The method is adjustable for different separation requirements, and computational fluid dynamics (CFD) models are shown that demonstrate the tuning of various microfluidic parameters to optimize separation performance. Other applications of LFDIs for establishment of stable concentration gradients, and the exposure of chemical constituents or biological particles to these concentration gradients are shown qualitatively. Microfluidic chips have been designed for high-throughput screening applications that enable the uniform and controlled exposure of cells to lysing agents, thus enabling the differentiation of cells by their sensitivity to specific agents in an on-chip cytometer coupled directly to the lysing structure.

Proceedings ArticleDOI
21 Jan 2001
TL;DR: In the case of micro/nano engineering system, we are in the transition regime between continuum and molecule dominated conditions as discussed by the authors. And this feature brings us the challenges when exploring the science and developing the technology in micro/nanano fluidics.
Abstract: Microfluidics is a collection of processes for moving bulk fluid mass or controlling the paths of selected embedded particles, cells or molecules, in flows. Length scale matching between the flow and the device is the key for efficient momentum and energy transfers of the desired fluid motions. MEMS enable us to handle minute amounts of fluid in the nano or pico liter range. With properly designed microfluidic devices, molecules can be directly manipulated by the flow patterns inside the device, which provides a pathway to exploit the nano world. Obviously, understanding of the molecular effects on flows becomes a crucial issue. In traditional fluid dynamics, the flow length scale is much larger than the molecular length scale. Continuum is the most common hypothesis for flow researches. In the case of micro/nano engineering system, we are in the transition regime between continuum and molecule dominated conditions. This feature brings us the challenges when exploring the science and developing the technology in micro/nano fluidics.

Journal ArticleDOI
TL;DR: Design, fabrication, and testing of plastic microfluidic devices for on-chip genetic sample preparation and a path to further individual component integration are described.
Abstract: Microfluidics technology shows excellent potential for applications in biotechnology, chemical sensing, and drug delivery The use of microfluidics results in cycle time reduction, reagent cost and labor intensity savings due to the benefits of miniaturization, and functional integration As a result, miniature DNA sample preparation and analytical devices may potentially become part of a point-of-care systems for rapid medical diagnoses Similar diagnostic devices will benefit veterinary and food safety applications In this paper, we discuss design, fabrication, and testing of plastic microfluidic devices for on-chip genetic sample preparation These fabrication methods are being used to produce components of a complete genetic sample preparation micro-system The detailed discussion on the development of micro-PCR (polymerase chain reaction) devices and bio-channel hybridization arrays is given We also describe a path to further individual component integration

Journal ArticleDOI
TL;DR: A PEEK interface for use in microfluidic applications is designed, fabricated and tested, which provides for the facile, non-permanent coupling of standard capillary tubing to silicon/glass micromixer chips.
Abstract: A PEEK interface for use in microfluidic applications is designed, fabricated and tested. The interface allows for the facile, non-permanent coupling of standard capillary tubing to silicon/glass micromixer chips. Importantly, the interface provides for a secure connection between capillary lines and chip reservoirs without the need for any adhesive materials. Furthermore, when used in conjunction with silicon/glass micromixer chips fluidic transport is stable over a wide range of volumetric flow rates (1–1500 μL min−1), and the entire construct can be rapidly assembled and disassembled at any time during the course of experimentation.

Journal ArticleDOI
13 Dec 2001-Talanta
TL;DR: Photolithographic techniques were used to derivatize micron-sized, spatially segregated DNA recognition elements in Polydimethylsiloxane (PDMS) microfluidic structures to create a prototype microfluidity sensor device that was used to separate and identify synthetic DNA targets that were fluorescently-labeled.

Proceedings ArticleDOI
01 Dec 2001
Abstract: This paper deals with the physical analysis and the experimental verification of splitting a droplet in an open microchannel (i.e., in a gap between two plates) by electrowetting forces. We discovered there exist criteria beyond which the droplet simply cannot be split by controlling the electrowetting. Based on the criteria, we fabricated the testing devices where an electrowetting principle was used to split a liquid droplet and made the experimental verification for the criteria. The channel gap size, the droplet size, and the contact angle change by electrowetting are important parameters in splitting a droplet. The small channel gap enhances the necking of the droplet, helping the splitting process. Higher applied voltage induces larger change in contact angle and consequently enhances the splitting process as well. Most importantly, the droplet cannot be split if the channel gap is too large for the given droplet size and EWOD mechanism.


Patent
14 Dec 2001
TL;DR: In this article, a microchannel array structure embedded in a silicon substrate and a fabrication method thereof is described, which is formed deep inside the substrate and has high-density microscopic micro-channels.
Abstract: The present invention is disclosed a microchannel array structure embedded in a silicon substrate and a fabrication method thereof. The microchannel array structure of the present invention is formed deep inside the substrate and has high-density microscopic micro-channels. Besides, going through surface micromachining, physical and chemical properties of the silicon substrate are hardly influenced by the fabrication procedures. With microchannels buried in the substrate, the top of a microchannel array structure becomes flat, minimizing the effect of step height. That way, additional devices such as passive components, micro sensors, micro actuators and electronic devices can be easily integrated onto the microchannel array structure. The microchannel array structure of the present invention can be employed as a basic fluidic platform for miniaturizing and improving perfomances of electronic device coolers as well as such fluidic micro-electro-mechanical system (MEMS) devices as biochips, microfluidic components and chemical analyzers, lab-on-a-chips, polymerase chain reaction (PCR) amplifiers, micro reactors and drug delivery systems.

Journal ArticleDOI
TL;DR: In this paper, a microfluidic chip capable of continuous sample switching and injection for bio-analytical applications is presented. But the performance of the chip is limited by the fact that it requires a pre-focusing function prior to flow switching, which is crucial for precise sample injection.
Abstract: In this paper, we present an investigation of a microfluidic chip capable of continuous sample switching and injection for bio-analytical applications. The novel device integrates two important microfluidic phenomena, including hydrodynamic focusing and valveless flow switching inside multi-ported microchannels. In this study, a simple theoretical model based on the `flow-rate-ratio' method is first proposed to predict the performance of the device. Based on these data, a pre-focused 1×N flow switch is designed and fabricated using micromachining techniques. A novel micromachining technique is demonstrated which combines quartz template fabrication and replication of microstructures on polymethylmethacrylate (PMMA) substrates for mass production of microfluidic devices. Three-dimensional templates with an inverse image of microfluidic channels are fabricated on quartz substrates and then used to imprint microstructures onto PMMA substrates using hot embossing methods. Finally, the flow switching is verified experimentally with the use of microscopic visualization of water sheath flows and a dye-containing sample flow. The experimental data indicate that the sample flow could be hydrodynamically pre-focused to a narrow stream and then guided into a desired outlet port based on relative sheath and sample flow rates. It also shows that the added `pre-focusing' function prior to the flow switching is crucial for precise sample injection. The microfluidic chip could be applied in the fields of bio/chemical analysis.

Journal ArticleDOI
TL;DR: In this article, a microanalytical system based on a microfluidics/electrochemical detection scheme was developed for on-site environmental characterization and for real-time non-invasive biomonitoring of toxic chemical mixtures.
Abstract: A microanalytical system based on a microfluidics/electrochemical detection scheme was developed. The microfluidic platform was fabricated based on a multi-layer lamination method. Fluidic microchannels were produced by sandwiching laser-machined adhesive-backed polyimide gaskets between layers of the device. Individual components, such as microfabricated piezoelectrically actuated pumps and a microelectrochemical cell were designed and fabricated into plug-in modules which can be readily plugged into (or unplugged from) the microfluidic platform. This allowed rapid change-out and repair of individual components by incorporating “plug and play” concepts now standard in PC's. The detection of lead and chlorophenols were performed with the microanalytical system to demonstrate the capabilities of this new technology for on-site environmental characterization and for real-time non-invasive biomonitoring of toxic chemical mixtures.

Patent
19 Dec 2001
TL;DR: In this article, the combination of the electric and magnetic fields causes the solution to flow through the channel, and the electric field generated by the use of the current carrying species is perpendicular to a magnetic field applied to the channel.
Abstract: Microfluidic channels utilizing magnetohydrodynamics are used to pump very small volumes of solution. The channels have electrodes along the walls of the channel and a current carrying species within the solution carries the current through the solution. The electric field generated by the use of the current carrying species is perpendicular to a magnetic field applied to the channel. The combination of the electric and magnetic fields causes the solution to flow through the channel.

Journal ArticleDOI
TL;DR: One such method, electrocapillarity as utilised by Prins et al., is shown in the picture.
Abstract: The macroscopic manipulation of liquids is a core component to the development of microfluidic devices. Although the Marangoni effect has been described for well over a century, actively tuning such surface tension effects is a more recent achievement. This Highlight compares recently reported electro- and photochemical methods in which this liquid manipulation has occurred. One such method, electrocapillarity as utilised by Prins et al., is shown in the picture.

Journal ArticleDOI
TL;DR: In this article, high-density plasma etching was used to achieve channel depths of 20-50 microns for microfluidics devices, which can reduce the analysis time and significantly reduce the volume requirements of patient blood or other bodily fluid.
Abstract: The move to miniaturization of biomedical systems offers tremendous potential for the improvement of health care, both in terms of reduced analysis time, and in significantly lowering the volume requirements of patient blood, or other bodily fluid. In order to fabricate microchannels for microfluidics, we have investigated two approaches using high-density plasma etching to achieve channel depths of 20–50 microns. The first was plasma etching of tapered silicon masters for hot embossing of plastics to form a capillary electrophoresis device. The second approach was the direct plasma etching of plastic to form a microfluidics device for DNA analysis. In both cases, we report the development of optimized etch conditions using SAS Institute, Inc. design of experiment software.

Journal ArticleDOI
TL;DR: In this article, a micromachined sensor was developed for the measurement of transient thermal signal responses leading to the thermal characterization of fluids at low sample volumes using thin-film technology with its characteristic low masses and high aspect ratios.
Abstract: Using thin-film technology with its characteristic low masses and high aspect ratios a new range of possibilities is made available for the use of dynamic thermal measuring principles. Based on this, a micromachined sensor was developed for the measurement of transient thermal signal responses leading to the thermal characterization of fluids at low sample volumes. The achieved resolution allowed the measurement of thermal parameters of the investigated fluids, i.e., thermal conductivity and specific heat, inside microfluidic systems at a high sensitivity, enabling the detection of inter-fluid boundaries, e.g., as found in micromixers and -reactors, making the sensor a useful tool for micro fluidic system characterization. This is achieved via the measurement of the frequency dependent thermal signal response.