Dynamic thermal sensor - principles in MEMS for fluid characterization
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.
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TL;DR: In this paper, a set of multiple modules may be arranged into an arrangement of modules, which may be coupled together using one or more coupling mechanisms included on each module, and each module within the arrangement may have a form suitable for arrangement of the modules within the regular polyhedral grid.
Abstract: A module may be provided with at least one opening, the opening being an endpoint of a microfluidic channel that passes through at least part of the module. A set of multiple such modules may be arranged into an arrangement of modules, which may be coupled together using one or more coupling mechanisms included on each module. The arrangement of modules may fit within a regular polyhedral grid, and each module within the arrangement of modules may have a form suitable for arrangement of the modules within the regular polyhedral grid. Fluid may then flow through at least a subset of the arrangement of modules via the microfluidic channel of each module of the subset of the arrangement of modules. Some modules may include sensors, actuators, or inner microfluidic channel surface coatings. The arrangement of modules may form a microfluidic circuit that can perform a microfluidic circuit function.
219 citations
TL;DR: In this article, a micro-sensor compatible with Bio-MEMS applications for wide-range thermal flow rate measurements in liquids is introduced, based on the applied materials and geometry, the sensor allows an outstanding resolution at minimum thermal crosstalk, enabling flow rate measurement down to 100 μg/h in water, i.e. 100 nl/h.
Abstract: This paper introduces a micro-sensor compatible with Bio-MEMS applications for wide-range thermal flow rate measurements in liquids. Based on the applied materials and geometry, the sensor allows an outstanding resolution at minimum thermal cross-talk, enabling flow rate measurements down to 100 μg/h in water, i.e. 100 nl/h. Active and passive measuring principles, their respective applications, and the dynamic flow range coverage are presented.
66 citations
TL;DR: In this paper, a micromachined device is applied to characterize the thermal transport properties of various liquids by means of sinusoidal excitation of a heater structure placed on a membrane and recording the resulting temperature at a specified distance using integrated germanium thermistors.
Abstract: Due to unique features like small thermal masses and reduced conductivities, membrane-based micromachined thermal sensors offer features superior to those provided by comparable macroscopic measurement setups. In this contribution a micromachined device is applied to characterize the thermal transport properties of various liquids. By means of sinusoidal excitation of a heater structure placed on a membrane and recording the resulting temperature at a specified distance using integrated germanium thermistors, the liquid's thermal parameters can be determined. A simple two-dimensional (2D) analytical model allows to interpret the amplitude and the phase of the measured sinusoidal temperature variation yielding both, the thermal conductivity and the diffusivity of the liquid.
56 citations
TL;DR: In this paper, an integrated microfluidic thermal sensor that can be used to characterize the thermal properties of nanoliter quantities of fluids and polymer thin films is presented, which consists of a polycrystalline silicon (polysilicon) heater located in close proximity to the hot junctions of p+-poly-silicon/gold microthermopiles fabricated on a thermally isolated membrane.
Abstract: This paper presents an integrated microfluidic thermal sensor that can be used to characterize the thermal properties of nanoliter quantities of fluids and polymer thin films. The device consists of a polycrystalline silicon (polysilicon) heater located in close proximity to the hot junctions of p+-polysilicon/gold microthermopiles fabricated on a thermally isolated membrane. ac calorimetric measurements were performed by introducing a periodic heat signal using the heater and detecting the frequency-dependent thermal signal response in the presence of various fluids and polymers. The thermal conductivity of different fluids and five typical polymers used in microfabrication was measured using this device.
48 citations
TL;DR: This work proposes an innovative mechanism to compensate the errors caused by different types of natural gases on the sensor’s reading, and implements and evaluates the proposed gas metering technique in various Internet of Things systems, including industrial flow metering, gas meetering in smart home, and gas meetingering in low-power wide-area networks.
Abstract: Utilities have traditionally employed or contracted meter readers to collect natural gas usage data, which is expensive and time consuming, and thus necessitates the need of smart natural gas metering. Existing gas metering systems mainly focus on measuring the amount of gas flowing through an microelectro mechanical system (MEMS) thermal gas flow sensor and simply ignore the detailed gas composition. From computational fluid mechanics simulations, however, we discover that gases with different compositions will cause different effects on the reading of an MEMS sensor. Based on a thorough analysis of the working principle of MEMS thermal gas flow sensor, we propose an innovative mechanism to compensate the errors caused by different types of natural gases on the sensor’s reading. The proposed solution first measures the physical property of metered gas to derive the composition correction coefficient that will then be used to correct the meter’s reading errors, considering the relation between the calorific value and physical property of natural gases. In this way, the proposed solution realizes a real-time multicomposition gas metering via thermal gas flow sensors. We implement and evaluate the proposed gas metering technique in various Internet of Things systems, including industrial flow metering, gas metering in smart home, and gas metering in low-power wide-area networks. Experiment results verify the innovative design and confirm that the proposed solution features high sensitivity, high precision, and high range ratio.
45 citations
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01 Jan 1973TL;DR: CRC handbook of chemistry and physics, CRC Handbook of Chemistry and Physics, CRC handbook as discussed by the authors, CRC Handbook for Chemistry and Physiology, CRC Handbook for Physics,
Abstract: CRC handbook of chemistry and physics , CRC handbook of chemistry and physics , کتابخانه مرکزی دانشگاه علوم پزشکی تهران
52,268 citations
TL;DR: In this article, the thermal conductivities of dielectric and conducting thin films of three commercial CMOS processes were determined in the temperature range from 120 to 400 K. The measurements were performed using micromachined heatable test structures containing the layers to be characterized.
Abstract: The thermal conductivities /spl kappa/ of the dielectric and conducting thin films of three commercial CMOS processes were determined in the temperature range from 120 to 400 K. The measurements were performed using micromachined heatable test structures containing the layers to be characterized. The /spl kappa/ values of thermally grown silicon oxides are reduced from bulk fused silica by roughly 20%. The /spl kappa/ of phosphosilicate and borophosphosilicate glasses are 0.94/spl plusmn/0.08 W m/sup -1/ K/sup -1/ and 1.18/spl plusmn/0.06 W m/sup -1/ K/sup -1/, respectively, at 300 K. A plasma-enhanced chemical-vapor-deposition silicon-nitride layer has a thermal conductivity of 2.23/spl plusmn/0.12 W m/sup -1/ K/sup -1/ at 300 K. This value is between published data for atmospheric-pressure CVD and low-pressure CVD nitrides. For the metal layers, we found thermal conductivities between 167 W m/sup -1/ K/sup -1/ and 206 W m/sup -1/ K/sup -1/, respectively, at 300 K, to be compared with 238 W m/sup -1/ K/sup -1/ of bulk aluminum. The temperature-dependent product /spl kappa//spl rho/ of /spl kappa/ with the electrical resistivity /spl rho/ agrees better than 8.2% between 180-400 K with that of pure bulk aluminum. The /spl kappa/ values of the polysilicon layers are between 22.4 W m/sup -1/ K/sup -1/ and 37.3 W m/sup -1/ K/sup -1/ at 300 K. They are reduced from similarly doped bulk silicon by factors of between 2.0-1.3. The observed discrepancies between thin film and bulk data demonstrate the importance of determining the process-dependent thermal conductivities of CMOS thin films.
178 citations
01 Jan 2000
TL;DR: In this paper, the thermal conductivities of dielectric and conducting thin films of three commercial CMOS processes were determined in the temperature range from 120 to 400 K. The measurements were performed using micromachined heatable test structures containing the layers to be characterized.
Abstract: The thermal conductivities κ of the dielectric and conducting thin films of three commercial CMOS processes were determined in the temperature range from 120 to 400 K. The measurements were performed using micromachined heatable test structures containing the layers to be characterized. The κ values of thermally grown silicon oxides are reduced from bulk fused silica by roughly 20%. The κ of phospho silicate and borophospho silicate glasses are 0.94 0.08 Wm K and 1.18 0.06 Wm K , respectively, at 300 K. A plasma-enhanced chemical-vapor-deposition silicon-nitride layer has a thermal conductivity of 2.23 0.12 Wm K at 300 K. This value is between published data for atmospheric-pressure CVD and low-pressure CVD nitrides. For the metal layers, we found thermal conductivities between 167 Wm K and 206 Wm K ,r e- spectively, at 300 K, to be compared with 238 Wm K of bulk aluminum. The temperature-dependent product κρ of κ with the electrical resistivity ρ agrees better than 8.2% between 180-400 K with that of pure bulk aluminum. The κ values of the polysilicon layers are between 22.4 Wm K and 37.3 Wm K at 300 K. They are reduced from similarly doped bulk silicon by factors of between 2.0-1.3. The observed discrepancies between thin film and bulk data demonstrate the importance of determining the process-dependent thermal conductivities of CMOS thin films. (442)
170 citations
25 Jan 1998
TL;DR: In this article, a micromachined thermal accelerometer based on the free-convection heat transfer of a small hot air bubble in a sealed chamber has been developed at Simon Fraser University.
Abstract: A micromachined thermal accelerometer that is simple, reliable, and inexpensive to make has been developed at Simon Fraser University. The operating principle of this accelerometer is based on the free-convection heat transfer of a small hot air bubble in a sealed chamber. An experimental device that requires only four masking steps to fabricate has been built. This device has demonstrated a 0.6 milli-g sensitivity that can theoretically be extended to sub-micro-g level: A 2-axis accelerometer based on the same operating principle has also been fabricated and tested.
133 citations
"Dynamic thermal sensor - principles..." refers background in this paper
...These systems employ a variety of temperature measuring principles and sensor geometries ranging from membranes [2], [3], [10] and bridges [4], [ 12 ], [13] to beams....
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...HERMAL principles have found numerous applications in MEMS covering flow-rate sensors [1]‐[4], thermal conductivity and -capacity based sensors [5]‐[11], accelerometers [ 12 ], and microphones [3], [4], [13]....
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TL;DR: In this article, an air flow measuring range from 0.6 ml/h to at least 150 l/h has been achieved, e.g. with a rectangular flow channel of 0.54 mm 2 cross-sectional area.
Abstract: Micromachined flow sensors based on thin film germanium thermistors offer high flow sensitivities and short response times. Using the controlled overtemperature scheme, the measurable air flow velocity ranges from ±0.01 to ±200 m/s and the response time to large step changes of the air velocity is less than 20 ms. In the constant power mode, a signal rise time of 1.6 ms has been demonstrated by the application of shock waves. An air flow measuring range from 0.6 ml/h to at least 150 l/h has been achieved, e.g. with a rectangular flow channel of 0.54 mm 2 cross-sectional area. Using a lookup table transformation, a linearized output signal can be obtained within 25 μs.
109 citations