Topic
Microheater
About: Microheater is a research topic. Over the lifetime, 814 publications have been published within this topic receiving 12478 citations.
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TL;DR: A microheater structure and its integration on a silicon microprobe, which can be used to heat local areas of tissue or to measure local tissue temperature with an accuracy of <0.3/spl deg/C, is described.
Abstract: This paper describes a microheater structure and its integration on a silicon microprobe. The 30-/spl mu/m-diameter microstructure can be used to heat local areas of tissue or to measure local tissue temperature with an accuracy of <0.3/spl deg/C. The polysilicon microheater is suspended on a dielectric membrane to reduce undesired heat conduction to the probe substrate. The heating efficiency is 4.4/spl deg/C/mW in still water and 2.2/spl deg/C/mW in guinea pig cortex. Six milliwatts applied for 2 min in cortex produces a temperature of 50/spl deg/C, creating a well-defined 50-/spl mu/m-wide lesion for determining probe position histologically. Fabrication of the heaters requires no additional masking or processing steps in addition to those normally used for recording or stimulating probes.
24 citations
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TL;DR: In this paper, the authors used seed bubbles to trigger boiling heat transfer and control thermal non-equilibrium of liquid and vapor phases in parallel microchannels, and identified four modes of flow and heat transfer.
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.
24 citations
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TL;DR: In this paper, the authors reported an intriguing boiling regime occurring for small heaters embedded on the boundary in sub-cooled water, where a single bubble oscillates continuously and repeatably at several $100\,$kHz.
Abstract: We report about an intriguing boiling regime occurring for small heaters embedded on the boundary in subcooled water. The microheater is realized by focusing a continuous wave laser beam to about $10\,\mu$m in diameter onto a 165\,nm-thick layer of gold, which is submerged in water. After an initial vaporous explosion a single bubble oscillates continuously and repeatably at several $100\,$kHz. The microbubble's oscillations are accompanied with bubble pinch-off leading to a stream of gaseous bubbles into the subcooled water. The self-driven bubble oscillation is explained with a thermally kicked oscillator caused by the non-spherical collapses and by surface pinning. Additionally, Marangoni stresses induce a recirculating streaming flow which transports cold liquid towards the microheater reducing diffusion of heat along the substrate and therefore stabilizing the phenomenon to many million cycles. We speculate that this oscillate boiling regime may allow to overcome the heat transfer thresholds observed during the nucleate boiling crisis and offers a new pathway for heat transfer under microgravity conditions.
24 citations
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23 Dec 2010TL;DR: In this paper, a 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.
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.
24 citations
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06 Apr 2006
TL;DR: An electrothermal actuated refreshable Braille cell, display systems using the cells, and methods for actuating the refreshable cells/displays were described in this paper. But the authors did not specify how to operate the microheater.
Abstract: An electrothermal actuated refreshable Braille cells, display systems using the cells, and methods for actuating refreshable Braille cells/displays. One method according to the invention comprises at least the following steps: a) providing power to a microheater within a cylinder, wherein the cylinder has a membrane at a first end and a microheater at a second end, and fluid in between; b) heating the fluid with the microheater, thereby causing it to expand; and c) allowing the membrane at the first end to bulge out, thereby forming a dot .
24 citations