Showing papers on "Microheater published in 2010"

Wavelength-tunable silicon microring modulator.

Abstract: We present a wavelength-tunable, compact, high speed and low power silicon microring modulator. With a ring radius of 5 microm, we demonstrate a modulator with a high speed of 12.5 Gbps and a driving voltage of 3 V to achieve approximately 6 dB extinction ratio in high speed measurement. More importantly, tunability of the resonant wavelength is accomplished by means of a microheater on top of the ring, with an efficiency of 2.4 mW/nm (2.4 mW is needed to tune the resonant wavelength by 1 nm). This device aims to solve the narrow bandwidth problem of silicon microcavity modulators and increase the data bandwidth in optical interconnect systems.

Optimization of metallic microheaters for high-speed reconfigurable silicon photonics

Abstract: The strong thermooptic effect in silicon enables low-power and low-loss reconfiguration of large-scale silicon photonics. Thermal reconfiguration through the integration of metallic microheaters has been one of the more widely used reconfiguration techniques in silicon photonics. In this paper, structural and material optimizations are carried out through heat transport modeling to improve the reconfiguration speed of such devices, and the results are experimentally verified. Around 4 µs reconfiguration time are shown for the optimized structures. Moreover, sub-microsecond reconfiguration time is experimentally demonstrated through the pulsed excitation of the microheaters. The limitation of this pulsed excitation scheme is also discussed through an accurate system-level model developed for the microheater response.

A MEMS Reactor for Atomic-Scale Microscopy of Nanomaterials Under Industrially Relevant Conditions

Abstract: We present a microelectromechanical systems (MEMS) nanoreactor that enables high-resolution transmission electron microscopy (TEM) (HRTEM) of nanostructured materials with atomic-scale resolution during exposure to reactive gases at 1 atm of pressure. This pressure exceeds that of existing HRTEM systems by a factor of 100, thereby entering a pressure range that is relevant to industrial purposes. The nanoreactor integrates a shallow flow channel (35 ?m high) with a microheater and with an array of electron transparent windows of silicon nitride. The windows are only 10 nm thick but are mechanically robust. The heater has the geometry of a microhotplate and is made of Pt embedded in a silicon nitride membrane. To interface the nanoreactor, a dedicated TEM specimen holder has been developed. The performance is demonstrated by the live formation of Cu nanoparticles in a catalyst for the production of methanol. At 120 kPa and for temperatures of up to 500°C , the formation of these nanoparticles can be observed clearly and with an exceptionally low thermal drift. HRTEM images of the nanoparticles show atomic lattice fringes with spacings down to 0.18 nm.

Local and CMOS-compatible synthesis of CuO nanowires on a suspended microheater on a silicon substrate.

Abstract: This paper presents the synthesis of CuO nanowires using a localized thermal heating method in ambient air. It employs local heat sources defined in micro-resistive heaters fabricated by a standard polysilicon-based surface micromachining process instead of a global furnace heating. Since the synthesis is performed globally at room temperature, the presented process is compatible with standard CMOS. The synthesized CuO nanowires are characterized by scanning electron microscopy, transmission electron microscopy and high resolution transmission electron microscopy. It is found that this approach provides a simple method to locally synthesize suspended CuO nanowires on polysilicon microbridges on silicon substrates, thus allowing for integration of CuO nanowires into silicon-based devices. It provides a significant step towards the process integration of CuO nanowires with MEMS to realize functional devices.

Fabrication and integration of metal oxide nanowire sensors using dielectrophoretic assembly and improved post-assembly processing

Abstract: We report the fabrication and integration of metal oxide nanowire sensors using dielectrophoretic assembly and a novel bonding process. Metal oxide nanowires were successfully prepared by a two-step thermal oxidation process from their corresponding metal nanowires (indium, tin, and indium–tin) that have been synthesized by electroplating in nanoporous templates. Before oxidation, dielectrophoretic (DEP) assembly and a novel post-assembly bonding process were applied to integrate high-density nanowire arrays on interdigitated microelectrodes. Scanning electron microscopy (SEM) images and energy dispersive X-ray spectroscopy (EDS) elemental analysis provide morphological and compositional informations of the metal and metal oxide nanowires. Electrical measurements of the nanowire arrays show how the resistance changed after each process, which demonstrates that the post-assembly bonding is an important and effective step in reducing contact resistance between the nanowires and interdigitated microelectrodes. Metal oxide nanowire sensor chips were fabricated using microelectrodes embedded with a microheater for temperature control. The performance of these metal oxide nanowire sensors was investigated towards common volatile organic compounds, including methanol, ethanol, isopropanol, acetone, chloroform, and benzene, and the sensors showed high sensitivity, fast response, and good repeatability. The assembly and improved post-assembly bonding processes developed in this research provide a new platform for nanowire-based sensor integration.

Application of indium tin oxide (ITO)-based microheater chip with uniform thermal distribution for perfusion cell culture outside a cell incubator

Abstract: This study reports a transparent indium tin oxide (ITO)-based microheater chip and its applicability for perfusion cell culture outside a cell incubator. The attempt of the proposed ITO microheater is to take the role of conventional bulky incubator for cell culture in order to improve integratability with the experimental setup for continuous/perfusion cell culture, to facilitate microscopic observation or other online monitoring activities during cell culture, or even to provide portability of cell culture operation. In this work, numerical simulation and experimental evaluation have been conducted to justify that the presented device is capable of providing a spatially uniform thermal environment and precise temperature control with a mild deviation of ±0.2°C, which is suitable for a general cell culture practice. Besides, to testify that the thermal environment generated by the presented device is well compatible with conventional cell incubator, chondrocyte perfusion culture was carried out. Results demonstrated that the physiology of the cultured chondrocytes on the developed ITO microheater chip was consistent with that of an incubator. All these not only demonstrate the feasibility of using the presented ITO microheater as a thermal control system for cell culture outside a cell incubator but also reveal its potential for other applications in which excellent thermal control is required.

Tuning of resonance-spacing in a traveling-wave resonator device

Abstract: In this work a traveling-wave resonator device is proposed and experimentally demonstrated in silicon-on-insulator platform in which the spacing between its adjacent resonance modes can be tuned. This is achieved through the tuning of mutual coupling of two strongly coupled resonators. By incorporating metallic microheaters, tuning of the resonance-spacing in a range of 20% of the free-spectral-range (0.4nm) is experimentally demonstrated with 27mW power dissipation in the microheater. To the best of our knowledge this is the first demonstration of the tuning of resonance-spacing in an integrated traveling-wave-resonator. It is also numerically shown that these modes exhibit high field-enhancements which makes this device extremely useful for nonlinear optics and sensing applications.

Seed bubbles trigger boiling heat transfer in silicon microchannels

Abstract: The smooth channel surface of microsystems delays boiling incipience in heated microchannels. In this paper, we use seed bubbles to trigger boiling heat transfer and control thermal non-equilibrium of liquid and vapor phases in parallel microchannels. The test section consisted of a top glass cover and a silicon substrate. Microheater array was integrated at the top glass cover surface and driven by a pulse voltage signal to generate seed bubbles in time sequence. Each microheater corresponds to a specific microchannel and is located in the microchannel upstream. Five triangular microchannels with a hydraulic diameter of 100 mu m and a length of 12.0 mm were etched in the silicon substrate. A thin platinum film was deposited at the back surface of silicon chip with an effective heating area of 4,500 x 1,366 mu m, acting as the main heater for the heat transfer system. Acetone liquid was used. With the data range reported here, boiling incipience was not initiated if wall superheats are smaller than 15A degrees C without seed bubbles assisted. Injection seed bubbles triggers boiling incipience and controls thermal non-equilibrium between liquid and vapor phases successfully. Four modes of flow and heat transfer are identified. Modes 1, 2, and 4 are the stable ones without apparent oscillations of pressure drops and heating surface temperatures, and mode 3 displays flow instabilities with apparent amplitudes and long periods of these parameters. The four modes are divided based on the four types of flow patterns observed in microchannels. Seed bubble frequency is a key factor to influence the heat transfer. The higher the seed bubble frequency, the more decreased non-equilibrium between two phases and heating surface temperatures are. The seed bubble frequency can reach a saturation value, at which heat transfer enhancement attains the maximum degree, inferring that a complete thermal equilibrium of two phases is approached. The saturation frequency is about a couple of thousand Hertz in this study.

Design, Electro-Thermal simulation and geometrical optimization of double spiral shaped microheater on a suspended membrane for gas sensing

Abstract: This paper is mainly focused on the optimization of the micromachined heater for gas sensing applications designed to withstand high-temperature. Different microheater geometries and dimensions have been investigated regarding their power consumption, temperature distribution over the sensing area and robustness when annealed at high temperature. The designed microheater withstood annealing temperatures of up to 700°C and moreover robustness of the silicon nitride membrane allowed the sensing area to be heated up to a high temperature 400–700°C.

Microheater based on magnetic nanoparticle embedded PDMS.

Abstract: A microheater was established by embedding magnetic nanoparticles into PDMS (MNP-PDMS). MNP-PDMS generated heat under an AC magnetic field and the temperature was controlled by varying the magnetic particle content and the magnetic field intensity. In this study, the MNP-PDMS chip was demonstrated to amplify the target DNA (732 bp) with > 90% efficiency compared to the conventional PCR thermocycler, and exhibited good performance in regards to temperature control. This system holds great promise for reliably controlling the temperature of thermal processes on an integrated microchip platform for biochemical applications.

Thermal Conductivity Measurements on Challenging Samples by the 3 Omega Method

Abstract: The 3 omega method is the best established method for measuring the thermal properties of thin films (>100 nm) and nanowires. Theoretically, the method could be applied to many more types of samples, leading to new knowledge, but to date little effort has been made to extend its applicability. An enabling set of technologies has been tested at the Fraunhofer-IPM. The technologies developed encompass a new design of microheater, the measurement of bulk samples with a prefabricated microheater on adhesive tapes and polymer sheets, the measurement of tiny bulk samples glued to the underside of polymer sheets, a fully automated experimental setup, and a new numerical tool adapted to the new type of heater. The new design of microheater and software were validated using float glass as a reference material. A microheater on adhesive tape was used to measure accurately the thermal properties of sintered thermoelectric materials. The thermal conductivity of a very small melt-spun nanocomposite sample glued to the underside of a Kapton™ sheet was measured. The potential of the new design of microheater to measure very thin (~nm) films is discussed.

A micromachined preconcentrator for ethylene monitoring system

Abstract: The key component to enhance the sensitivity of the gas analysis system is the preconcentrator which accumulates, concentrates and releases the concentrated analyte upon applying a heating pulse. With increasingly strict regulations on the quality of fruits delivered to the consumer, maturity and ripening levels of fruits require very close monitoring of ethylene concentration. This paper focuses on the design, fabrication and characterization of a micromachined preconcentrator with an application emphasis on the monitoring of ethylene concentration. The device consists of 16 silicon microchannels loaded with carboxen 1000 adsorbent, a platinum microheater to heat the adsorbent to the desired operating temperature, and inlet/outlet fluidic ports. Thick silicon microchannels were etched using a DRIE process. Only clean air was used as a carrier and desorption gas. The enhancement of 100 ppb ethylene concentration was demonstrated. Various desorption flow rates as well as accumulation periods were tested.

Microboiling Measurements of Thermal-Inkjet Heaters

Abstract: Microboiling occurs when a microheater covered by liquid is operated with microseconds pulse. As a result of the high heat flux, a vapor bubble is built up above the heater. This phenomenon is used for thermal inkjet as well as other applications. In this experimental study, the bubbles are traced and photographed. The evolution of the bubbles is shown from the first nucleation, through maximal volume of the bubble, until the final collapse of the bubble, together with parametric measurements. At the end of the heater lifetime, the heater cracking process is shown frame after frame, supported with simulations.

ZnO nanostructures with controlled morphologies on a glass substrate

Abstract: We report morphology-controlled selective growth of ZnO nanostructures on glass substrates by using catalyst-free metal-organic chemical vapor deposition For the morphology-controlled selective growth, a microheating method using a series of microheaters was developed, which provided well-controlled local heating based on the microheater geometry and spatial arrangement ZnO nanostructure morphology depended on the local growth temperature, so various nanostructure morphologies were obtained selectively at specific positions on glass substrates by using local microheating The monolithic integration of nanostructures with different morphologies will have great potential for applications in multifunctional devices

Explosive vaporization of a water layer on a flat microheater

Abstract: Explosion vaporization of a water layer of different thickness, induced by pulse heating in an inhomogeneous temperature field on the surface of a flat microheater coated with a submicron silicon-carbide layer, is experimentally studied. An optical method is used for recording the vaporization time history and dynamics of the steam blanket. Pulsed laser irradiation is applied for high-time-resolution photography of the vaporization process. The dynamics of filling the heater surface with the vapor phase and the lifetime of the main vapor bubble and the satellite bubble are estimated. Dependences of the vaporization temperature on the heater temperature growth are obtained. The initial temperature is 30°C; the temperature growth rate on the heater surfaces is about 180 MK/s.

Thermo-mechanical characterization of surface-micromachined microheaters using in-line digital holography

Abstract: This paper describes the application of lensless in-line digital holographic microscopy (DHM) to carry out thermo-mechanical characterization of microheaters fabricated through PolyMUMPs three-layer polysilicon surface micromachining process and subjected to a high thermal load. The mechanical deformation of the microheaters on the electrothermal excitation due to thermal stress is analyzed. The numerically reconstructed holographic images of the microheaters clearly indicate the regions under high stress. A double-exposure method has been used to obtain the quantitative measurements of the deformations, from the phase analysis of the hologram fringes. The measured deformations correlate well with the theoretical values predicted by a thermo-mechanical analytical model. The results show that lensless in-line DHM with Fourier analysis is an effective method for evaluating the thermo-mechanical characteristics of MEMS components.

Electro thermal analysis and fabrication of low cost microheater using a nickel alloy for low temperature MEMS based gas sensor application

Abstract: A stable and low power heating characteristics of a microheater are very important for the gas sensor platform In this paper, we present a complete electrothermal and coplanar structure of a microheater for MEMS based gas sensor platform using a low cost nickel alloy Dilver PI (alloy of Ni, Co, Fe) having high resistivity 49∗10–8Ωm and high yield stress 680MPa with low thermal conductivity 175W/m/°C A comparative study has also been made with six different types of heater structures Thermal electrical analysis was done using finite element modeling of Intellisuite 82 Microheater device of size 5mm × 5mm with a 50μ thick membrane of size 2mm∗2mm are fabricated using a single lithographic mask The maximum temperature of 200 °C with a distribution of ± (2–3) % over the entire microheater membrane region has been achieved with 5V excitation The power consumption 146 mW has been achieved

Tunable high speed silicon microring modulator

Abstract: We present a 12.5 Gbps silicon micro-ring modulator achieved by carrier depletion in a lateral pn diode. Tunability of the resonant wavelength is accomplished by means of a microheater, with an efficiency of 2.36 mW/nm.

Platinum microheater integrated silicon optical bench assembly for endoscopic optical coherence tomography

Abstract: A novel platinum microheater and comb isolator integrated silicon optical bench (SiOB) assembly method has been successfully demonstrated to provide electrical connection and high precision alignment for a two-axis gimbal-less micromirror. Localized heating and wetting of plastic core micro solder balls is achieved by the integrated platinum heater, and the maximum measured temperature of the platinum heater is about 250 °C. In addition, assembly procedures are significantly simplified by involving a comb isolator made by deep reactive ion etching (DRIE) in comparison with our previously reported design. DRIE is also applied to form a 45° trench on the lower silicon substrate with a nearly vertical sidewall for the micromirror. Hence, the overall dimensions of the SiOB assembly can be reduced further to meet the requirements of endoscopic optical coherence tomography (EOCT) for miniaturization.

Deposition and characterization of nichrome thin film over PDMS elastomer

Abstract: Nichrome (Ni - Cr 80/20 wt %) is one of the most widely used thin film material for the development of micro heaters in various applications Present paper discusses the optimized sputtering conditions required for successful deposition of nichrome thin film and fabrication of microheaters over a biocompatible polymer PDMS, for biomedical application Various sputtering conditions like the base vacuum, working pressure, sputtering power and time were standardized to obtain crack free nichrome thin film deposition over PDMS and glass surface Microheaters were fabricated using the conventional photolithography technique and the resulting structures were used to measure temperature coefficient of resistance (TCR) of nichrome Measured sheet resistance and TCR of the crack free deposited nichrome thin film over PDMS surface were 362 Ω/ and 713 ppm/°C respectively

Novel micro-heater structure for low-power and fast photonic reconfiguration

Abstract: A novel microheater structure integrated over small microdisks in silicon-on-insulator is proposed with less than 100 nanosecond reconfiguration time using pulsed-excitation. Power consumption of the devices are shown to be 40% less than conventional microheaters.

Adjustable‐Stiffness Films via Integrated Thermal Modulation

Abstract: We present a new strategy for fabricating thermally responsive adjustable stiffness materials. A microfabricated heater embedded within a composite film is used to modulate the temperature of a low melting point polymer. Currents ranging from 0 to 200 mA were applied to the microheater and modulated material stiffness ≈100-fold between 1.03 GPa and 10.9 MPa. The outside temperature of the composite ranged from 23 to 45.5 °C over this range of currents, suggesting its possible use in biomedical applications. The softened composite was bent into arbitrary shapes and allowed to restiffen, highlighting the reconfigurable nature of the material.

Characterization of the thermal transients of an Ultra Low Power micromachined sensor

Abstract: This paper describes an embedded system for the simultaneous dynamic control and thermal characterization of the heating phase of an Ultra Low Power (ULP) micromachined sensor, featuring thermal characteristics quite similar to those of innovative ULP semiconducting metal oxide (MOX) sensors. A Pulse Width Modulated (PWM) powering system has been realized using a microcontroller featuring an ARM7 core to characterize the thermal behavior of a device formed by a Pt microheater and a Pt temperature sensor, over an insulating membrane. Two operating modes, namely constant target heater resistance and constant heating power, were implemented. The aim was to analyze the relation between heating period and operating temperature, to observe the thermal time constants of the device and the total thermal conductance. Repeatability of experimental results was assessed by guaranteeing the standard deviation of the controlled temperature was within ±5.5°C in worst case conditions. Experimental results show quantitatively a unique time constant τ both for the heater and the T-sensor, that changes dependently on the temperature rise ΔT between the ambient and the operating temperature in a range from 2 ms to 2.4 ms. The dependence of the operating temperature of such ULP micromachined systems on the frequency and duty cycle of the PWM signal was also characterized and guidelines for minimizing the temperature ripple were defined. Finally, we observed that in the chosen operating temperature range the thermal conductance is a linear function of the heating power.

Microheater and method for fabrication of microheater

Abstract: PURPOSE: A micro heater and a manufacturing method thereof are provided to form a desired shape of platinum pattern by removing photoresist through a lift-off process after deposition of a platinum film. CONSTITUTION: A manufacturing method of a micro heater comprises steps of: growing a poly-crystal 3C-SiC film on a substrate, depositing an aluminum nitride film on the poly-crystal 3C-SiC film, and forming a pattern on the aluminum nitride film. The pattern forming step includes depositing a platinum film on the aluminum nitride film with a sputtering method, and forming a platinum pattern on the platinum film with a lift-off process.

Formation and observation of thermal bubble from multilayer heating material

Abstract: The target of this research is to design and fabricate the micro-heater and its electrodes in order to study the thermal bubble behavior. In fabrication of micro-heater, this research focus on the design of multilayer micro-heater and the selection of materials further. For the multilayer materials, we choose Ti/Al/Ta (15/25/200 nm/nm/nm) to be the material to replace the conventional polysilicon, Ta or expensive Pt heaters for improving the heat-resistant ability of Pt, poor adhesion of Ta and high electrical resistance of polysilicon. Then, the bubble sizes between frequencies and voltages were discussed in the multilayer heating materials. The multilayer micro-heater in this research can generate good bubbles at low frequencies operation. It has the advantages of low electrical resistance, the good thermal resistance, and the good heat dissipation to contribute to improve the poor heat dissipation and strength of the Pt micro-heater in order to increase the life of the heater.

Design and Simulation of MEMS Microhotplate for Gas Sensor Applications

Abstract: There is growing demand for the metal oxide based gas sensor for it vast application in various fields. Traditional gas sensors, based on ceramic platform consume more power and have less sensitivity. MEMS based gas sensors on the other hand offer superior performance to conventional ceramic gas sensors owing to their low power consumption, faster response and compatibility to CMOS circuits. Micro electromechanical systems (MEMS) based integrated gas sensors present several advantages for these applications such as ease of array fabrication, small size, and unique thermal manipulation capabilities. MEMS based gas sensors; which are usually produced using a standard CMOS (Complimentary Metal Oxide Semiconductor) process, have the additional advantages of being readily realized by commercial foundries and amenable to the inclusion of on-chip electronics. In this work the design and simulation of a microheater on glass substrate for MEMS based gas sensor has been performed. Electro-Thermo-Mechanical analysis was done to review the temperature and stress distribution over the microheater. Stress analysis revealed stress at the corners of the microheater. Computer simulation has been widely used for MEMS device design. The main advantage of computer simulation is to provide design optimization by varying geometry, layer dimension, and materials of the device without actual fabrication. This systematic approach can save time and cost of device fabrication and experiment. In this work, a new model of gas sensor is simulated in COVENTORWARE software. The solver is used to analyze the electrical current flow, voltage and heat and stress distribution in the device. The result is used to predict the temperature and stress as a function of the applied voltage across heating layer. Using the displacement results is used in the mechanical analysis to predict the mechanical behaviour of the microheater. The optimization is performed mainly with respect to power consumption , temperature distribution and stress distribution.