Showing papers on "Microheater published in 2005"

A MEMS microvalve with PDMS diaphragm and two-chamber configuration of thermo-pneumatic actuator for integrated blood test system on silicon

Abstract: In this paper, a thermo-pneumatic in-channel microvalve applicable to integrated blood test system is presented. Thermo-pneumatic actuator separated in drive chamber part and thermal expansion chamber part (two-chamber configuration) is newly proposed for the purpose to reduce direct heat transfer from microheater to flow channel. Polydimethylsiloxane (PDMS) is employed as the diaphragm material for a long stroke actuation in microvalve operation and high sealing performance of liquid. It is also used as adhesive layer between glass and silicon in the structure. The microvalve with the proposed structure was fabricated. Both static and dynamic flow control characteristics were evaluated with a liquid sample (DI water) and a gas sample (N 2 ), respectively. A high ON/OFF ratio of liquid sample was obtained thanks to the soft PDMS diaphragm. Liquid sealing performance in the closed state was high enough for our application (

Temperature alternation by an on-chip microheater to reveal enzymatic activity of beta-galactosidase at high temperatures.

Abstract: A method to measure enzymatic activity at high temperatures by rapid temperature alternation of a microreactor with a microheater is proposed. On-chip microreactor and microheater were integrated on a glass plate by MEMS technology; this microheater can control the temperature of the microreactor with a response speed of 34.2 and 31.5 K/s for temperature rise and fall, respectively, with an accuracy of 3 degrees C. The enzyme, beta-galactosidase, was revealed to survive short exposure (4-s pulses) to temperatures above that which would "normally" denature them. Its activity at 60 degrees C was revealed to be approximately 4 times greater than that at room temperature. This method not only gives new kinetic information in biochemistry but also enables application in highly sensitive biosensors.

Silicon MEMS vaporizing liquid microthruster with internal microheater

Abstract: This paper reports a silicon MEMS vaporizing liquid microthruster (VLM) with an internal p-diffused microheater. The device fabrication and testing have been briefly described. The VLM consisting of two micromachined, bonded silicon chips produces thrusts in the range of 5 µN to 120 µN with a heater power of 1 W to 2.4 W at a water flow rate of 1.6 µl s−1 using an exit nozzle of throat size 30 µm × 30 µm. A maximum thrust of 120 µN was produced with a heater power of 2 W at a water flow rate of 0.7 µl s−1 with exit nozzle of throat size 50 µm × 50 µm. The measurement has been carried out using a sensitive cantilever and a laser based lamp-and-scale arrangement. The internal microheater is expected to yield a higher efficiency compared with the external microheater.

Integrated and microheater embedded gas sensor array based on the polymer composites dispensed in micromachined wells

Abstract: This paper reports a new fabrication method and a performance of miniaturized and temperature-controllable gas sensor array constructed on 5 in. double side polished (1 0 0) silicon wafer. The films of polymer-carbon black composite were used as gas sensors. Both silicon process and bulk micromachining technology were employed to fabricate sensor array equipped with an interdigitated electrode pair, microheater, and micromachined well of an area of 2 mm ×2 mm. During dispensing a polymer composite–solvent solution on the electrode, micromachined well helped the sensor film be placed in a constrained area and be formed reproducibly from a constant volume of the polymer composite–solvent solution. The dimension of a sensor array chip consisting of 16 separate sensors is 30 mm ×14 mm. The sensors of polymer-carbon black composite responded diversely when they were dispensed in micromachined wells and exposed to various chemical vapors. Principal component analysis (PCA) clearly demonstrated that the gas sensor array could identify various chemical vapors. Pt microheater consumed 7 mW to heat sensor film at the operating temperature of 40 °C, and temperature reached a steady maximum value promptly because of its small heat capacity and effective thermal isolation. The electrical resistance of polymer composite sensor and the partition coefficients for sensor–vapor interactions showed to be considerably affected by the substrate temperature.

Nanosecond imaging of microboiling behavior on pulsed-heated au films modified with hydrophilic and hydrophobic self-assembled monolayers.

Abstract: Fast transient microboiling has been characterized on modified gold microheaters using a novel laser strobe microscopy technique. Microheater surfaces of different hydrophobicity were prepared using self-assembled monolayers of hexadecane thiol (hydrophobic) and 16-mercaptohexadecanol (hydrophilic) as well as the naturally hydrophilic bare gold surface. The microheater was immersed in a pool of water, and a 5-micros voltage pulse to the heater was applied, causing superheating of the water and nucleation of a vapor bubble on the heater surface. Light from a pulsed Nd:Yag laser was configured to illuminate and image the sample through a microscope assembly. The timing of the short duration (7.5 ns) laser flash was varied with respect to the voltage pulse applied to the heater to create a series of images illuminated by the flash of the laser. These images were correlated with the transient resistance change of the heater both during and after the voltage pulse. It was found that hydrophobic surfaces produced a bubble that nucleated at an earlier time, grew more slowly to a smaller maximum size, and collapsed more rapidly than bubbles formed on hydrophilic surfaces.

Localized and CMOS compatible growth of carbon nanotubes on a 3 /spl times/ 3 /spl mu/m/sup 2/ microheater spot

Abstract: We present the synthesis of carbon nanotubes utilizing a localized chemical vapor deposition method. The modified method relies on the usage of local heat sources defined in microscale resistive heaters through a standard polysilicon based surface micromachining process instead of a global reaction furnace heating. The presented method provides a remedy to amorphous carbon contamination of the exposed chip and most importantly a significant step towards the process integration of nanotubes into functional devices. Since the synthesis is carried out globally at room temperature, the suggested process is compatible with standard CMOS technology. The presented fabrication method is batch-fabrication and thus complementary to discrete fabrication techniques and serves to build devices to evaluate the electromechanical properties of carbon nanotubes.

A four-bit digital microinjector using microheater array for adjusting the ejected droplet volume

Abstract: In this paper, we present the design, fabrication, and experimental results of 4-bit digital microinjectors, whose ejected droplet volumes are adjusted by the digital operation of a 4-bit microheater array. We design the reference microinjectors as well as its comparative test structures. In the fabrication process, we use a five-mask micromachining process and the total chip size of the fabricated microinjector is 7640 /spl mu/m/spl times/5260 /spl mu/m. We observe the microbubble generation and collapse on the microheater array. The microbubbles initiate and grow individually on top of each operating microheater, however the microbubbles merge together before collapse. We measure the ejected droplet volumes and velocities, which are adjusted from 12.1 /spl ap/ 55.6 pl and 2.3 /spl ap/ 15.7m/s, respectively, depending on the 15 possible combinations of 4-bit microheater array. We also experimentally characterize the effect of geometric variation including the microheater size, intermicroheater gap, microchannel width and sequential operation of microheater array on the ejected droplet volume and velocity. Thus, the present microinjector has a potential for application to the high-resolution inkjet printers with multiple gray levels or high-precision fluid injectors with variable volume control.

SOI-CMOS compatible low-power gas sensor using sputtered and drop-coated metal-oxide active layers

Abstract: In this paper, a Silicon-On-Insulator (SOI) solid-state gas-sensor with an original design of a polysilicon loop-shaped microheater fabricated on a thin-stacked dielectric membrane is presented. The microheater ensures high thermal uniformity and very low power consumption (25 mW for heating at 400°C). Sensitive films are based on tin and tungsten oxides deposited either by RF sputtering or drop coating methods. The fabricated sensors are tested to a wide variety of contaminant species and promising results are obtained. The use of completely CMOS compatible TMAH-based bulk micro-machining techniques during the fabrication process, allows easy smart gas sensor integration in SOI-CMOS technology. This makes SOI-based gas-sensing devices particularly attractive for use in handheld battery-operated gas monitors.

Genotyping by dynamic heating of monolayered beads on a microheater surface

Abstract: This paper presents SNP scoring by DASH technology by employing dynamic heating of beads immobilized on a chip with integrated heater and sensor The microfabricated chip designed for open-surface DNA analysis allows fast, well controllable temperature ramping and homogeneous temperature distribution over the entire heater area Beads containing DNA duplexes are immobilized on the surface of the chip by microcontact printing using a PDMS stamp All three possible variants of a SNP site of an oligonucleotide were accurately scored using the bead-based DASH approach Using the chip, the total analysis time could easily be reduced by a factor 2 compared with the current DASH assay

Micro Thermoelectric Type Gas Sensor

Abstract: The present invention provides a micro thermoelectric gas sensor having a thermoelectric conversion section, a microheater, a catalyst layer formed on the microheater and to be heated by the microheater, which acts as a catalyst for catalytic combustion of a combustible gas, and a sensor detection section with an electrode pattern therefore formed on a membrane of a predetermined thickness, and a method for forming a micropattern of a functional material of a catalyst or resistor in a predetermined position on a substrate in a state in which the microstructure of the functional material remains controlled.

Microheater and Process For Producing the Same

Abstract: To provide a microheater which gives a desired temperature and starts an exothermic reaction upon immediate contact with air and in which plural microheaters can be chained or incorporated in a packaging material. A microheater having a heat generating composition molded body made of a moldable heat generating composition containing surplus water as a connecting substance accommodated in an air-permeable accommodating bag, which is characterized in that the accommodating bag is made of a heat seal layer-containing substrate and a covering material and has an exothermic part as formed by laminating a heat generating composition molded body as molded on the substrate which is substantially planar and does not have a pocket, an accommodating division and an accommodating section, covering by the covering material and heat sealing the periphery of the heat generating composition molded body; that the moldable heat generating composition contains, as essential components, an iron powder, a carbon component, a reaction accelerator and water, has a content of water in the moldable heat generating composition of from 1 to 60%, does not contain a flocculant aid, a flocculant, an agglomeration aid, a dry binder, a dry binding agent, a dry binding material, a sticky raw material, a thickener and an excipient, contains surplus water so as to have a water mobility value of from 0.01 to 20, with the water in the heat generating composition not functioning as a barrier layer, and is capable of causing an exothermic reaction upon contact with air; that a volume of the heat generating composition molded body is from 0.1 to 30 cm 3 , and a ratio of a capacity of the exothermic part to the volume of the heat generating composition molded body is from 0.6 to 1.0; and that a maximum height of the exothermic part is from 0.1 to 10 mm.

Thermocapillary effects on low-g Pool Boiling from microheater arrays of various aspect ratio

Abstract: Pool boiling heat transfer measurements from heaters of varying aspect ratio were obtained in low-g (0.01 g ± 0.025 g) and high-g (1.7 g ± 0.5 g) using the KC-135 aircraft. The heater aspect ratio was varied by selectively powering 2×2, 2×4, 2×6, 2×8, and 2×10 arrays of heaters in a 10×10 heater array containing individual heaters 700×700 μm2 in size. Control circuitry was used to maintain a nominally isothermal boundary condition on the heater surface while the power dissipated by the heater was measured. Steady-state boiling data in low-g and high-g were obtained using FC-72 as the working fluid at two bulk fluid temperatures. At high wall superheats, boiling performance appears to decrease with an increase in aspect ratio. Strong thermocapillary convection was observed for a negligible gas concentration in the liquid. CHF was not observed for the heater used in this study indicating that CHF in low-g may be highly dependent on the surface characteristics of the heater in addition to the heater size.

Thermoelectric gas sensor made into microelement

Abstract: PROBLEM TO BE SOLVED: To provide a thermoelectric gas sensor, made into a microelement, particularly an inexpensive contact combustion type micro gas sensor, capable of identifying the gas kind from a combustible mixed gas, using a simple structure. SOLUTION: This micro thermoelectric gas sensor comprises a thermoelectric conversion part, a microheater, a catalyst layer formed on the microheater and heated by the microheater, the catalyst layer working as a catalyst catalytically burning a combustible gas, and a sensor part including an electrode pattern therefor, which are formed on the membrane of a predetermined thickness. According to this, power consumption can be reduced, and high sensitivity concentration measurement and high-speed response can be attained. COPYRIGHT: (C)2006,JPO&NCIPI

Microfluidic detection and analysis by integration of evanescent wave sensing with thermocapillary actuation

Abstract: An integrated system capable of microfluidic actuation, detection and sensing is described which combines evanescent wave sensing with thermocapillary manipulation. Liquid droplets or streams transported across the beam path of a planar thin film waveguide, which encapsulates the microheater array, induce attenuation of the propagating waveguide modes. The attenuated signal is used to monitor droplet location, dye concentration in aqueous solutions and reaction kinetics for enzymatic hydrolysis of the sugar X-galactose by beta-galactosidase.

Nucleate Pool Boiling Characteristics From a Horizontal Microheater Array

Abstract: Title of Document: NUCLEATE POOL BOILING CHARACTERISTICS FROM A HORIZONTAL MICROHEATER ARRAY Christopher Henry, Ph.D., 2005 Directed By: Associate Professor, Jungho Kim, Department of Mechanical Engineering Pool boiling heat transfer measurements from different heater sizes and shapes were obtained in low-g (0.01 g) and high-g (1.7 g) aboard the NASA operated KC-135 aircraft. Boiling on 4 square heater arrays of different size (0.65 mm, 2.62 mm, 7.29 mm, 49 mm) was investigated. The heater arrays consist of 96 independent square heaters that were maintained at an isothermal boundary condition using control circuitry. A fractional factorial experimental method was designed to investigate the effects of bulk liquid subcooling, wall superheat, gravitational level, heater size and aspect ratio, and dissolved gas concentration on pool boiling behavior. In high-g, pool boiling behavior was found to be consistent with classical models for nucleate pool boiling in 1-g. For heater sizes larger than the isolated bubble departure diameter predicted from the Fritz correlation, the transport process was dominated by the ebullition cycle and the primary mechanisms for heat transfer were transient conduction and microconvection to the rewetting liquid in addition to latent heat transfer. For heater sizes smaller than this value, the boiling process is dominated by surface tension effects which can cause the formation of a single primary bubble that does not depart the heater surface and a strong reduction in heat transfer. In low-g, pool boiling performance is always dominated by surface tension effects and two mechanisms were identified to dominate heat and mass transport: 1) satellite bubble coalescence with the primary bubble which tends to occur at lower wall superheats and 2) thermocapillary convection at higher wall superheats and higher bulk subcoolings. Satellite bubble coalescence was identified to be the CHF mechanism under certain conditions. Thermocapillary convection caused a dramatic enhancement in heat transfer at higher subcoolings and is modeled analytically. Lastly, lower dissolved gas concentrations were found to enhance the heat transfer in low-g. At higher dissolved gas concentrations, bubbles grow larger and dryout a larger portion of the heater surface. NUCLEATE POOL BOILING CHARACTERISTICS FROM A HORIZONTAL MICROHEATER ARRAY By Christopher Douglas Henry Thesis or Dissertation submitted to the Faculty of the Graduate School of the University of Maryland, College Park, in partial fulfillment of the requirements for the degree of Doctor of Philosophy 2005 Advisory Committee: Associate Professor Jungho Kim, Chair Professor Marino Di Marzo Professor James Duncan Associate Professor Greg Jackson Associate Professor Gary Pertmer © Copyright by Christopher Douglas Henry 2005

Technological processes for microheater and micro-hot-plate in the implementation of a MEM gas sensor

Abstract: In this work a microsystem fabrication process for a microheater (MH) and a microhotplate (MHP), as well as their electrical behavior, are reported. This microstructure consists of a SiO/sub 2/ membrane supported by four cross shaped beams, and two layers of polysilicon (poly1 and poly2); poly1 forms the microheater and the poly2 layer works as a micro hot plate (MHP), whose function is to achieve a homogeneous temperature distribution all over the microsystem. Both poly1 and poly2 are separated by a SiO/sub 2/ layer, isolating them electrically, and were patterned by lift off process. The microstructure or membrane is located over a micropit (IMP) that was made by etching the Si substrate with KOH for seven hours; a Si/sub 3/N/sub 4/ sacrifice layer was used for this purpose. Electrical contact for the layers was made evaporating aluminum and patterned by lift off also. Electrical measurements were made by applying a ramp from -1.5 V through 1.5 V and measuring the current through poly1 and poly2, with temperature as a parameter, changing temperature with 25 /spl deg/C steps, from room temperature up to 300/spl deg/C, heating and cooling. The temperature coefficient of resistance (TCR) for poly1 and poly2 was calculated.

MEMS Based High Dose Radiation Resistant SOI Pressure Sensor for Aerospace Applications

Abstract: Transducers used in nuclear propulsion systems and space applications must withstand high-dose radiation environments along with high temperature operation. However, performance characteristics of various conventional silicon sensors are degraded at high temperature environments, and also show substantial radiation damage due to ionization in silicon. In this paper, a MEMS based high-dose radiation resistant SOI pressure sensor with integrated microheaters to maintain constant temperature for artificial satellites is developed, and its suitability for operation under high-dose radiation environment is reported. The developed sensor has inbuilt microheater arrangement for constant temperature operation. SOI pressure sensors were subjected to a radiation dosage level up to 100 krad, and performance characteristics such as linearity, offset and sensitivity were evaluated.

Thermal conductivity measuring method and device, and gas component ratio measuring device

Abstract: According to power Ph applied to a microheater provided in atmosphere gas while supported in the air, and the heater temperature Th and the ambient temperature To at that time, radiation coefficient C[=Ph/(Th-To)] of heat from the microheater is calculated. Based on the proportional relationship [C=K·λo] between the thermal conductivity λo of the atmosphere gas and the heat radiation coefficient C at its reference temperature, thermal conductivity λo of the atmosphere gas at the reference temperature is determined from the heat radiation coefficient C thus calculated.

Study of the Temperature Field in Microchannels of a PDMS Chip With Embedded Local Heater Using Temperature-Dependent Fluorescent Dye

Abstract: This paper presents a simple microheater design for microfluidic devices by embedding resistance wire into a PDMS chip, and the results of an experimental study of the thermal response of liquid samples in the PDMS chip with the embedded local heater. Temperature-dependent fluorescent dye was used to measure the temperature distribution within a microchannel heated by the local heater. Two heater configurations were built, tested, and compared with numerical simulation. Through comparing the performance of these two configurations, heating and cooling rates and uniformity of the temperature field were evaluated. Additionally, thermal cycling at two different temperature levels was achieved by controlling the power of the local heater.Copyright © 2005 by ASME

Method for manufacturing microfluid flow control chip and method for controlling microfluid width in a microchannel using air boundaries

Abstract: To provide a microfluid flow control chip capable of controlling width of microfluid in microchannel using air boundaries, a microfluid width control method capable of controlling width of microfluid in microchannel using air boundaries, and a method for applying microfluid into coefficient or alignment of cells by controlling width of microfluid. The method for manufacturing microfluid flow control chip comprises a process of depositing an aluminum layer on a silicon substrate(2); a process of fabricating a microheater(6) by patterning the aluminum layer; a process of a SOG coating layer(8) for electrically insulating the fabricated microheater; a process of patterning the SOG coating layer; a process of forming a photoresist coating layer on the silicon substrate to fabricate a mold for microchannel(12); a process of patterning the photoresist coating layer; a process of forming a microchannel in PDMS(polydimethyl siloxane)(16) to fabricate the microchannel by the fabricated mold; a process of stripping the fabricated PDMS from the mold; and a process of forming the microchannel between the PDMS and the silicon substrate by bonding the PDMS and the silicon substrate to each other. The method for controlling microfluid width in microchannel using air boundaries(14) comprises the processes of: generating air by heating water by a microheater in microchannel of the fabricated microfluid flow control chip; producing air boundaries by the generated air; and controlling width of microfluid by controlling pressure in the air boundaries.

Method and apparatus to manufacture optical fiber coupler

Abstract: PROBLEM TO BE SOLVED: To obtain a method and an apparatus to manufacture a highly precise optical fiber coupler in which three or more optical fibers, which are arranged close to each other in a parallel manner, are fusion processed by uniformly heating them with a microheater so as to put them in a stretched state with no irregularity. SOLUTION: The manufacturing method consists of a setting process in which at least three or more optical fibers whose cover is removed are inserted into a heater from the opening section of the microheater and are arranged in a parallel manner in a direction orthogonal or approximately orthogonal to the opening section and a heating and fusing process in which the microheater is moved back and forth in the axial center direction of the optical fibers whose number is equal to or greater than three with a prescribed width size after the setting process so as to heat and to fuse the optical fibers and to stretch the optical fibers in the axial center direction. COPYRIGHT: (C)2005,JPO&NCIPI

Selective local synthesis of nanowires on a microreactor chip

Abstract: This work presents a novel synthesis process for selectively locally growing nanowires on a microreactor chip fabricating by MEMS process. Carbon nanotubes (CNT) are synthesized using a chemical vapor deposition (CVD) technique by controlling the temperature of the microheaters in the microchamber of the device. The diameter of the synthesized CNT is about 15 nm, and the length is about 100-200 nm. The design and modeling of the microheater/reactor chip is discussed. The fabrication process and the packaging of the device, which include catalyst patterning with the fabrication of microheater and anodic bonding process, are presented. Finally, the process parameters, such as the heating voltages, synthesis times and the flow-rates of chemicals, are discussed.

Microfluidic device with integrated temperature control unit for hydrogel actuation

Abstract: A microfluidic device, with a temperature control unit to study the behaviour of temperature sensitive hydrogel, has been designed, simulated and fabricated. The system consists of a PDMS (polydimethylsiloxane) microchannel sealed on a Pyrex substrate with microfabricated titanium electrodes for heating and sensing elements. A thermal insulating layer in-between the electrodes and the substrate was found to increase the heat transfer to the fluid and decrease the lateral heat propagation. The temperature profile and the heat distribution in the system were investigated using the commercial software package CFD-ACE+. The device was electrically and thermally characterised. Such a system, biocompatible and re-usable, could be a potential candidate for biomedical applications such as DNA amplification and protein synthesis.

Thermal modeling of a microheater in a microchannel chip

Abstract: Integration of microheaters in microfluidic systems has a wide range of applications such as sensing, actuating and biomedical devices. This study focused on the investigation of the thermal performance of a nickel microheater fabricated on a printed circuit board using a LIGA process. Both experimental and computational methods were used in conjunction with preliminary theoretical analysis. The microheater was tested both in air and water. The temperature distributions of the microheater were measured by an advanced thermography system. The numerical study was carried out using the multiphysics CFD package CFD-Ace+. The temperature of the microheater increased approximately linearly with the input power for the experimental conditions. The microheater heated up exponentially at the start of power supply. At a supply of 120mA electrical current, the microheater could heat up at a rate of around 90°C/s. During the cooling stage, the rate was much higher and could reach 800°C/s. When placed in the microchannel with air flow, the heater could heat the flow effectively without causing significant increase in the chip temperature. The CFD results were validated by comparing temperature distributions on the chip surface and on the heater surface. The validated CFD results allowed more detailed investigations of thermal and fluid flow within the microchannel and the whole chip.

An innovative all-polymeric drug-supply device

Abstract: In this paper, we report an innovative all-polymeric drug-supply device. The micro outlet of the device was ablated through a polymethyl methacrylate (PMMA) layer using a microheater. The size of the ablated micropore was mainly related to the heater temperature profile, and the molten PMMA took the gold heater lines away from the pore area, avoiding possible block of the gold lines to the flow out of the pore. Simulation was conducted to find the temperature profile on the surface of the microheater, and experimental results have a good match with simulation results.