Showing papers on "Microheater published in 2020"
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TL;DR: This work indicates the feasibility of optimizing the gas-sensing performance of sensors by combining rational material hybridization, 3D structural engineering with temperature modulation, and employed integrated microheaters to effectively suppress the response to humidity, with nearly unimpaired response to NO2, which boosted the selectivity.
Abstract: A facile, one-step hydrothermal route was exploited to prepare SnO2-decorated reduced graphene oxide hydrogel (SnO2/RGOH) with three-dimensional (3D) porous structures for NO2 gas detection. Various material characterizations demonstrate the effective deoxygenation of graphene oxide and in situ growth of rutile SnO2 nanoparticles (NPs) on 3D RGOH. Compared with the pristine RGOH, the SnO2/RGOH displayed much lower limit of detection (LOD) and an order of magnitude higher sensitivity, revealing the distinct impact of SnO2 NPs in improving the NO2-sensing properties. An exceptional low theoretical LOD of 2.8 ppb was obtained at room temperature. The p-n heterojunction formed at the interface between RGOH and SnO2 facilitates the charge transfer, improving both the sensitivity in NO2 detection and the conductivity of hybrid material. Considering that existing SnO2/RGO-based NO2 sensors suffer from great vulnerability to humidity, here we employed integrated microheaters to effectively suppress the response to humidity, with nearly unimpaired response to NO2, which boosted the selectivity. Notably, a flexible NO2 sensor was constructed on a liquid crystal polymer substrate with endurance to mechanical deformation. This work indicates the feasibility of optimizing the gas-sensing performance of sensors by combining rational material hybridization, 3D structural engineering with temperature modulation.
62 citations
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TL;DR: In this paper, a flexible and noninvasive approach for efficient continuous micromixing and microreaction based on direct current-induced thermal buoyancy convection in a single microfluidic unit is presented.
Abstract: We present a flexible and noninvasive approach for efficient continuous micromixing and microreaction based on direct current-induced thermal buoyancy convection in a single microfluidic unit. Theoretically, microfluids in this microsystem are unevenly heated by powering the asymmetrically arranged microheater. The thermal buoyancy convection is then formed to induce microvortices that cause effective fluidic interface disturbance, thereby promoting the diffusion and convective mass transfer. The temperature distribution and the convection flow in the microchip are first characterized and studied, which can be flexibly adjusted by changing the DC voltage. Then the mixing performance of the presented method is validated by joint numerical and experimental analyses. Specifically, at U = 7 V, the mixing efficiencies are higher than 90% as the flow rate is lower than Qv= 600 nL/s. So high-quality chemical or biochemical reactions needing both suitable heating and efficient mixing can be achieved using this method. Finally, as one example, we use this method to synthesize nano-sized cuprous oxide (Cu2O) particles by effectively mixing the Benedict’s solution and glucose buffer. Remarkably, the particle size can be tuned by changing the voltage and the concentration of Benedict’s solution. Therefore, this micromixer can be attractive for diverse applications needing homogeneous sample mixtures.
46 citations
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TL;DR: A chemiresistive gas sensor based on three-dimensional Ag modified reduced graphene oxide (3D Ag-rGO) aerogel shows a remarkable fast response for 50 ppb NO2 and a low limit of detection (LOD) of 6.9 ppb, demonstrating a greatly improved selectivity toward NO2.
Abstract: A chemiresistive gas sensor based on a three-dimensional Ag-modified reduced graphene oxide (3D Ag-rGO) aerogel is reported. We improve the graphene-based sensor performance by optimization of operating temperature, chemical modification, and new design of the material geometrical structure. The self-assembly and Ag nanoparticle (NP) decoration of the Ag-rGO aerogel are realized by a facile, one-step hydrothermal method. An integrated low-power microheater fabricated on a micromachined SiO2 membrane is employed to enhance the performance of the sensor with a fast response to NO2 and a shortened recovery time. The 3D Ag-rGO-based sensor at a temperature of 133 °C exhibits the highest response. At the same time, the response to other gases is suppressed while the response of the Ag-rGO sensor toward ammonia at 133 °C is reduced to half of the value at room temperature, demonstrating a greatly improved selectivity toward NO2. Additionally, the sensor exhibits a remarkably fast response to 50 ppb NO2 and a low limit of detection of 6.9 ppb.
43 citations
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TL;DR: This work provides a strategy for electro-thermal-optical devices to be used as sensors, emitters, and switches in the IR wavelength range by tailoring the suitable metamaterial pattern.
Abstract: We present an on-chip tunable infrared (IR) metamaterial emitter for gas sensing applications. The proposed emitter exhibits high electrical-thermal-optical efficiency, which can be realized by the integration of microelectromechanical system (MEMS) microheaters and IR metamaterials. According to the blackbody radiation law, high-efficiency IR radiation can be generated by driving a Direct Current (DC) bias voltage on a microheater. The MEMS microheater has a Peano-shaped microstructure, which exhibits great heating uniformity and high energy conversion efficiency. The implantation of a top metamaterial layer can narrow the bandwidth of the radiation spectrum from the microheater to perform wavelength-selective and narrow-band IR emission. A linear relationship between emission wavelengths and deformation ratios provides an effective approach to meet the requirement at different IR wavelengths by tailoring the suitable metamaterial pattern. The maximum radiated power of the proposed IR emitter is 85.0 µW. Furthermore, a tunable emission is achieved at a wavelength around 2.44 µm with a full-width at half-maximum of 0.38 µm, which is suitable for high-sensitivity gas sensing applications. This work provides a strategy for electro-thermal-optical devices to be used as sensors, emitters, and switches in the IR wavelength range.
42 citations
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TL;DR: The potential of this strain engineering platform to fabricate a strain-actuated optical modulator with single-layer MoS2 is illustrated and the compact geometry results in a negligible spatial drift, which facilitates their integration in optical spectroscopy measurements.
Abstract: We present microfabricated thermal actuators to engineer the biaxial strain in two-dimensional (2D) materials. These actuators are based on microheater circuits patterned onto the surface of a poly...
32 citations
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TL;DR: The obtained results demonstrate the potential of using ITO as an ultra-low loss microheater for high performance silicon thermo-optic tuning and open an alternative way for enabling the large-scale integration of phase shifters required in emerging integrated photonic applications.
Abstract: Typically, materials with large optical losses such as metals are used as microheaters for silicon based thermo-optic phase shifters. Consequently, the heater must be placed far from the waveguide, which could come at the expense of the phase shifter performance. Reducing the gap between the waveguide and the heater allows reducing the power consumption or increasing the switching speed. In this work, we propose an ultra-low loss microheater for thermo-optic tuning by using a CMOS-compatible transparent conducting oxide such as indium tin oxide (ITO) with the aim of drastically reducing the gap. Using finite element method simulations, ITO and Ti based heaters are compared for different cladding configurations and TE and TM polarizations. Furthermore, the proposed ITO based microheaters have also been fabricated using the optimum gap and cladding configuration. Experimental results show power consumption to achieve a π phase shift of 10 mW and switching time of a few microseconds for a 50 µm long ITO heater. The obtained results demonstrate the potential of using ITO as an ultra-low loss microheater for high performance silicon thermo-optic tuning and open an alternative way for enabling the large-scale integration of phase shifters required in emerging integrated photonic applications.
29 citations
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TL;DR: Without expensive masks and complex operation processes, programmable liquid-metal-repellent patterns were easily obtained by femtosecond laser selectively treating the PDMS surface, enabling EGaIn to be patterned on the textured surface.
29 citations
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TL;DR: This study showcases the possibility of forming a whole new class of miniaturized reconfigurable integrated nanophotonics using beyond-binary reconfiguration of optical functionalities in hybrid PCM-photonic devices.
Abstract: Inducing a large refractive-index change is the holy grail of reconfigurable photonic structures, a goal that has long been the driving force behind the discovery of new optical material platforms. Recently, the unprecedentedly large refractive-index contrast between the amorphous and crystalline states of Ge-Sb-Te (GST)-based phase-change materials (PCMs) has attracted tremendous attention for reconfigurable integrated nanophotonics. Here, we introduce a microheater platform that employs optically transparent and electrically conductive indium-tin-oxide (ITO) bridges for the fast and reversible electrical switching of the GST phase between crystalline and amorphous states. By the proper assignment of electrical pulses applied to the ITO microheater, we show that our platform allows for the registration of virtually any intermediate crystalline state into the GST film integrated on the top of the designed microheaters. More importantly, we demonstrate the full reversibility of the GST phase between amorphous and crystalline states. To show the feasibility of using this hybrid GST/ITO platform for miniaturized integrated nanophotonic structures, we integrate our designed microheaters into the arms of a Mach-Zehnder interferometer to realize electrically reconfigurable optical phase shifters with orders of magnitude smaller footprints compared to existing integrated photonic architectures. We show that the phase of optical signals can be gradually shifted in multiple intermediate states using a structure that can potentially be smaller than a single wavelength. We believe that our study showcases the possibility of forming a whole new class of miniaturized reconfigurable integrated nanophotonics using beyond-binary reconfiguration of optical functionalities in hybrid PCM-photonic devices.
28 citations
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TL;DR: The Stream Liquid Heating Holder as discussed by the authors is a complete system for liquid phase experiments at elevated temperature inside the transmission electron microscope, which features a unique on-chip flow channel combined with a microheater, enabling direct flow over the imaging area and rapid replenishment of the solution inside the nanocell with simultaneous heating to more than 100 °C.
Abstract: Liquid phase transmission electron microscopy has become a powerful tool for imaging the structure and dynamics of materials in solution Direct observation of material formation, modification and operation has provided unique insights into the chemistry that governs the structure–property relationships of materials with myriad applications including optical, magnetic and electronic materials However, full control over the reaction environment inside the microscope, especially the solution temperature and concentration of reactants, remains challenging and has limited the application of this high-resolution methodology Here we present the ‘Stream Liquid Heating Holder’, a complete system for liquid phase experiments at elevated temperature inside the transmission electron microscope This system features a unique on-chip flow channel combined with a microheater The channel enables direct flow over the imaging area and rapid replenishment of the solution inside the Nano-cell with simultaneous heating to more than 100 °C The capabilities of the system are demonstrated by studying the liquid flow dynamics and comparing the temperature dependent etching kinetics of silica nanoparticles by in situ liquid phase electron microscopy to in-flask experiments
26 citations
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23 citations
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TL;DR: In this paper, a high performance coplanar MEMS microheater based gas sensor, in respect of its portability and power consumption, with enhanced response, has been designed, fabricated and characterized.
Abstract: A high performance coplanar MEMS microheater based gas sensor, in respect of its portability and power consumption, with enhanced response, has been designed, fabricated and characterized. Pt microheater, along with interdigitated electrodes (IDE) and Methane sensing layer were deposited on micro machined silicon substrates. Performance of the microheater was analyzed in terms of power consumption and heat distribution uniformity. Existence of a leakage voltage was detected which was found to reduce the overall sensor performance. Source of this leakage voltage was theoretically and experimentally investigated. To reduce the effect of such leakage voltage on sensor performance, a low drift OPAmp based high gain cancellation circuit was subsequently designed, implemented and an enhanced response of about 70% was observed as against 40% for uncompensated coplanar sensors. An exhaustive sensor characterization study was carried out for different concentrations of methane and performance was analyzed in terms of sensitivity, response, recovery time etc. A sensitivity of about 73% was observed for 5000ppm methane concentration with a moderate response (110 sec) and good recovery (30 sec) time.
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TL;DR: In this article, a tin oxide gas sensor was demonstrated to operate at temperatures as high as 850°C, sufficient for spontaneous pyrolysis of the methane molecule, and the response and recovery times were both ~10 s.
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TL;DR: A Three-Dimensional Finite Element Model (3DFEM) that includes the details of the heat transfer between the sample and the probe in the diffusive and transition heat conduction regimes was found to accurately simulate the temperature profiles measured using a Wollaston thermal probe setup.
Abstract: Temperature measurement using Scanning Thermal Microscopy (SThM) usually involves heat transfer across the mechanical contact and liquid meniscus between the thermometer probe and the sample. Variations in contact conditions due to capillary effects at sample-probe contact and wear and tear of the probe and sample interfere with the accurate determination of the sample surface temperature. This paper presents a method for quantitative temperature sensing using SThM in noncontact mode. In this technique, the thermal probe is scanned above the sample at a distance comparable with the mean free path of ambient gas molecules. A Three-Dimensional Finite Element Model (3DFEM) that includes the details of the heat transfer between the sample and the probe in the diffusive and transition heat conduction regimes was found to accurately simulate the temperature profiles measured using a Wollaston thermal probe setup. In order to simplify the data reduction for the local sample temperature, analytical models were developed for noncontact measurements using Wollaston probes. Two calibration strategies (active calibration and passive calibration) for the sample-probe thermal exchange parameters are presented. Both calibration methods use sample-probe thermal exchange resistance correlations developed using the 3DFEM to accurately capture effects due to sample-probe gap geometry and the thermal exchange radii in the diffusive and transition regimes. The analytical data reduction methods were validated by experiments and 3DFEM simulations using microscale heaters deposited on glass and on dielectric films on silicon substrates. Experimental and predicted temperature profiles were independent of the probe-sample clearance in the range of 100–200 nm, where the sample-probe thermal exchange resistance is practically constant. The difference between the SThM determined and actual average microheater temperature rise was between 0.1% and 0.5% when using active calibration on samples with known thermal properties and between ∼1.6% and 3.5% when using passive calibration, which yields robust sample-probe thermal exchange parameters that can be used also on samples with unknown thermal properties.
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TL;DR: A novel manipulation platform is proposed that combines microheaters and an area cooling system to produce enough force to steer sedimentary particles or cells and to limit the thermal diffusion and has a high potential to become a powerful tool for biology research.
Abstract: Contactless particle manipulation based on a thermal field has shown great potential for biological, medical, and materials science applications. However, thermal diffusion from a high-temperature area causes thermal damage to bio-samples. Besides, the permanent bonding of a sample chamber onto microheater substrates requires that the thermal field devices be non-disposable. These limitations impede use of the thermal manipulation approach. Here, a novel manipulation platform is proposed that combines microheaters and an area cooling system to produce enough force to steer sedimentary particles or cells and to limit the thermal diffusion. It uses the one-time fabricated motherboard and an exchangeable sample chamber that provides disposable use. Sedimentary objects can be steered to the bottom center of the thermal field by combined thermal convection and thermophoresis. Single particle or cell manipulation is realized by applying multiple microheaters in the platform. Results of a cell viability test confirmed the method's compatibility in biology fields. With its advantages of biocompatibility for live cells, operability for different sizes of particles and flexibility of platform fabrication, this novel manipulation platform has a high potential to become a powerful tool for biology research.
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TL;DR: Capable of detecting fluorescence in the DNA and temperature simultaneously and being imaged in a customized assembly, this microchip can be used to screen for mutations in a variety of DNA samples in disease diagnosis and prognosis.
Abstract: A microfluidic chip integrated with a microheater and a luminescent temperature sensor for rapid, spatial melting curve analysis was developed and applied for the screening of a breast cancer gene fragment. The method could detect genetic differences in around 3 minutes total for the whole procedure, which is much faster than established procedures. A microfabrication technique was developed to allow for bonding of a temperature sensing thin film and a Pt microheater with PDMS and the chips could be employed to generate and measure thermal gradients and the fluorescence intensity of stained DNA through multispectral optical imaging. The sensing layer consisting of poly(styrene-co-acrylonitrile) and a tris(1,10-phenanthroline)ruthenium(ii) temperature probe was generated by blade coating on a glass substrate with an attached Pt microheater. Calibration of the temperature between 20 and 90 °C yielded an overall resolution of around 0.13 K. The chip was employed for the screening of the BRCA 2 breast cancer gene; BRCA2 exon 5 was differentiated by its mutant rs80359463 by a 1.1 K difference in melting temperature and two fragments of BRCA2 exon 11 were differentiated by their mutants rs276174826 and rs876660311 by 0.7 K and 2.0 K, respectively. The standard deviations were between 0.1 and 0.5 K. Capable of detecting fluorescence in the DNA and temperature simultaneously and being imaged in a customized assembly, this microchip can be used to screen for mutations in a variety of DNA samples in disease diagnosis and prognosis.
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TL;DR: Laser-deposited carbon aerogel is a low-density porous network of carbon clusters synthesized using a laser process that is sensitive to NO2 compared to ammonia and other volatile organic compounds and is able to detect ultra-low concentrations down to at least 10 parts-per-billion.
Abstract: Laser-deposited carbon aerogel is a low-density porous network of carbon clusters synthesized using a laser process. A one-step synthesis, involving deposition and annealing, results in the formation of a thin porous conductive film which can be applied as a chemiresistor. This material is sensitive to NO2 compared to ammonia and other volatile organic compounds and is able to detect ultra-low concentrations down to at least 10 parts-per-billion. The sensing mechanism, based on the solubility of NO2 in the water layer adsorbed on the aerogel, increases the usability of the sensor in practically-relevant ambient environments. A heating step, achieved in tandem with a microheater, allows the recovery to the baseline making it operable in real world environments. The operability at room temperature, its low cost and scalable production makes it promising for Internet-of-Things air quality monitoring.
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TL;DR: In this paper, an ultrafast direct laser patterning technique was used to fabricate a low-cost microsensor and its application for formaldehyde detection was reported, where the patterns of microheater and interdigitated electrodes (IDEs) were realized using laser micromachining techniques by ablation of gold thin film on alumina substrate.
Abstract: Here, an ultrafast direct laser patterning technique to fabricate a low-cost microsensor and its application for formaldehyde detection are reported. The patterns of microheater and interdigitated electrodes (IDEs) were realized using laser micromachining techniques by ablation of gold thin film on alumina substrate. The thin film of gold microheater showed good stability up to 300 °C with a fast response time of 80 s and temperature coefficient of resistance (TCR) was calculated as $1.37\times 10^{-{3}}/^{\circ }\text{C}$ . Moreover, gold microheater exhibited long-term reliability under self-heating mode with a negligible resistance drift $^{-{1}}$ ) to formaldehyde even to detect sub-ppm concentrations with fast response (32 s) and recovery kinetics (72 s). Moreover, the microsensor was also used on-site rapid screening for the detection and quantification of formaldehyde concentration in formalin-treated fish sample.
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TL;DR: An approach for the realization of coupled-mode induced transparency (CMIT) in a hybrid polydimethylsiloxane (PDMS)-coated silica microbubble resonator, with an Au microwire inserted in the hollow channel is demonstrated.
Abstract: We demonstrate an approach for the realization of coupled-mode induced transparency (CMIT) in a hybrid polydimethylsiloxane (PDMS)-coated silica microbubble resonator, with an Au microwire inserted in the hollow channel. Owing to the large negative thermo-optics coefficient of PDMS, different radial order modes with opposite thermal sensitivities can coexist in this hybrid microcavity. By applying a current through the Au microwire, which acts as a microheater, the generated Ohmic heating could thermally tune the resonance frequencies and the frequency detuning of the coupled mode to achieve controllable CMIT. This platform offers an efficient and convenient way to obtain controllable CMIT for applications, such as label-free biosensing and quantum information processing.
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TL;DR: Unlike most of the current flow meter products based on the thermal sensing principle that only offer the calorimetric mass flow rates, this flow meter can measure not only the mass flow rate but also the flow media properties.
Abstract: The design, fabrication, operation, calibration, and performance of a microfluidic flow meter utilizing a micromachined (MEMS) thermal time-of-flight sensing chip are presented. The MEMS sensing chip integrates multiple sensing elements (thermistors) on a silicon substrate. This sensing chip works on the principle of thermal excitation with a modulated power source from the microheater while the responses of the sensing elements at both upstream and downstream of the modulated thermal source are processed for both the time differences and the amplitudes of the heat transfer in the microfluidic flow. Unlike most of the current flow meter products based on the thermal sensing principle that only offer the calorimetric mass flow rates, this flow meter can measure not only the mass flow rate but also the flow media properties. Experimental results for water and isopropyl alcohol are discussed, which demonstrate the capability and performance of the novel microfluidic flow meter.
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TL;DR: The novel liquid metal-based microheater with parallel ventilating side-channels is believed to be widely applicable to soft micro-electro-mechanical system(MEMS) heating devices.
Abstract: Gallium-based liquid metal can be used as a material for microheaters because it can be easily filled into microchannels and electrified to generate Joule heat, but the liquid metal-based microheater will suffer breakage induced by voids forming within the liquid metal when the temperature normally gets higher than 100 °C. To resolve this problem, a novel liquid metal-based microheater with parallel ventilating side-channels is presented. It consists of a liquid-metal heating channel and two parallel ventilating side-channels. The heating channel is connected with the side-channels by small gaps between polydimethylsiloxane (PDMS) posts. Experimental results show that this novel microheater can be heated up to 200 °C without damage. To explain its excellent performance, an experiment is performed to discover the development of the voids within the liquid-metal heating channel, and two reasons are put forward in this work on the basis of the experiment. Afterward pressing and bending tests are conducted to explore the mechanical stability of the novel microheaters. Finally, the microheaters are applied to warm water to show their good flexibility on non-flat surfaces. In consequence, the novel liquid metal-based microheater is believed to be widely applicable to soft micro-electro-mechanical system(MEMS) heating devices.
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TL;DR: In this article, the authors investigate the heat transfer across a closing nanoscale gap between an operational microelectronic device and a static substrate in ambient conditions and find that their thermal conductivity plays an essential role.
Abstract: We investigate the heat transfer across a closing nanoscale gap between an operational microelectronic device and a static substrate in ambient conditions. The device contains an embedded microheater and a nanoscale metal wire that works as a thermometer. The heater causes a microscale protrusion by thermal expansion such that its surface approaches the substrate until contact occurs. Meanwhile, the metal wire located near the center of the protrusion surface measures the temperature of the protrusion, which is dependent on the size of the gap, the substrate material, and the ambient conditions. We study the nanoscale heat transfer using three different substrates and find that their thermal conductivity plays an essential role. Finally, the experiments are conducted under different relative humidity (RH) conditions. The results show that the ambient humidity can also affect the nanoscale heat transfer when RH > 75%.
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TL;DR: In this article, a direct laser ablation technique was used to replace the conventional lithography and etching processes to form functional silicon carbide (SiC) devices from 3C−SiC•onglass wafers.
Abstract: Silicon carbide (SiC)‐based microsystems are promising alternatives for silicon‐based counterparts in a wide range of applications aiming at conditions of high temperature, high corrosion, and extreme vibration/shock. However, its high resistance to chemical substances makes the fabrication of SiC particularly challenging and less cost‐effective. To date, most SiC micromachining processes require time‐consuming and high‐cost SiC dry‐etching steps followed by metal wet etching, which slows down the prototyping and characterization process of SiC devices. This work presents a lithography and etching‐free microfabrication for 3C‐SiC on insulator‐based microelectromechanical systems (MEMS) devices. In particular, a direct laser ablation technique to replace the conventional lithography and etching processes to form functional SiC devices from 3C‐SiC‐on‐glass wafers is used. Utilizing a single line‐cutting mode, both metal contact shapes and SiC microstructures can be patterned simultaneously with a remarkably fast speed of over 20 cm s−1. As a proof of concept, several SiC microdevices, including temperature sensors, strain sensors, and microheaters, are demonstrated, showing the potential of the proposed technique for rapid and reliable prototyping of SiC‐based MEMS.
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01 Mar 2020-Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems
TL;DR: In this paper, the design and fabrication of nichrome-based coplanar microheater for LPG sensing applications is presented, which is fabricated using photolithography process.
Abstract: The design and fabrication of nichrome based coplanar microheater for LPG sensing applications is presented in this work. Nichrome based coplanar microheater is fabricated using photolithography process. The surface morphology of DC sputtered nichrome is characterized using scanning electron microscope. Electrothermal behaviour of the fabricated microheater is characterized by varying the applied current while the thermal distribution pattern over the active heating area is recorded using thermal imaging camera. The silicon thickness under microheater active area is varied by silicon etching with different time duration in TMAH solution. Silicon thickness effect on maximum temperature of microheater is also investigated experimentally. The tin oxide (SnO2) thin film as LPG sensor is deposited on fabricated coplanar heating platform and it is tested with different amount of LPG concentration.
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TL;DR: In this article, a high temperature-sensitive long-period fiber grating (LPFG) sensor fabricated by the local fictive temperature modification is proposed and demonstrated, and the results demonstrate that the LPFG temperature sensors with 600μm grating period and 32 period numbers offer the average sensitivity of 0.084nm/C in the temperature range of room temperature (RM) to 875°C.
Abstract: A high temperature-sensitive long-period fiber grating (LPFG) sensor fabricated by the local fictive temperature modification is proposed and demonstrated. High-frequency CO2 laser pulses scan standard single-mode fiber (SMF), and the modification zones extended to the core of SMF. Experimental results demonstrate that the LPFG temperature sensors with 600 μm grating period and 32 period numbers offer the average sensitivity of 0.084 nm/C in the temperature range of room temperature (RM) to 875°C. The LPFGs fabricated here show exponential change in terms of the spectral wavelength shift versus changes in temperature. In addition, the maximum temperature sensitivity of 0.37 nm/C is achieved by employing long-period microfiber grating (LPMFG), fabricated by the microheater brushing technique and the local fictive temperature modification. LPMFG sensor exhibits better temperature characteristics due to a thinner diameter.
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TL;DR: In this paper, an optical fiber sensor is proposed for measurement of the boiling point and boiling range of liquids, which provides opportunity for on-line and in-situ chemical characterization of various liquids.
Abstract: In this paper, an optical fiber sensor is proposed for measurement of the boiling point and boiling range of liquids. Since boiling point and/or boiling range of liquids correlate directly to chemical composition of liquids, the proposed sensor provides opportunity for on-line and in-situ chemical characterization of various liquids. The proposed sensor is manufactured on the tip of a standard optical fiber, and consists of a Fabry-Perot temperature sensor and short section Vanadium doped fiber, which serves as a microheater. The latter is cyclical and rapidly heated by application of high-power fiber-coupled laser diode, while the Fabry-Perot temperature sensor is used to detect appearance of boiling process and to measure the absolute temperature. The proposed sensor is less than 1 mm long and allows for characterizing samples in quantities of 140 nL in as short time as ten seconds. All-silica/all-fiber design of the sensor provides high chemical inertness, dielectric design and possibility for remote operation. Two sensor types are proposed; the first is intended for measurement of very small samples (140nL). This measurement takes only about 10 seconds. The second sensor type is suitable for online monitoring of binary or multicomponent mixtures, and provides accurate boiling range data of a given mixture.
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TL;DR: An innovative idea to make microfluidic devices with integrated silicon sidewall electrodes, and their use as microheaters is reported, and this is achieved by modifying the original Surface Channel Technology with optimized mask designs.
Abstract: Surface Channel Technology is known as the fabrication platform to make free-hanging microchannels for various microfluidic sensors and actuators. In this technology, thin film metal electrodes, such as platinum or gold, are often used for electrical sensing and actuation purposes. As a result that they are located at the top surface of the microfluidic channels, only topside sensing and actuation is possible. Moreover, in microreactor applications, high temperature degradation of thin film metal layers limits their performance as robust microheaters. In this paper, we report on an innovative idea to make microfluidic devices with integrated silicon sidewall electrodes, and we demonstrate their use as microheaters. This is achieved by modifying the original Surface Channel Technology with optimized mask designs. The modified technology allows to embed heavily-doped bulk silicon electrodes in between the sidewalls of two adjacent free-hanging microfluidic channels. The bulk silicon electrodes have the same electrical properties as the extrinsic silicon substrate. Their cross-sectional geometry and overall dimensions can be designed by optimizing the mask design, hence the resulting resistance of each silicon electrode can be customized. Furthermore, each silicon electrode can be electrically insulated from the silicon substrate. They can be designed with large cross-sectional areas and allow for high power dissipation when used as microheater. A demonstrator device is presented which reached 119.4 ∘ C at a power of 206.9 m W , limited by thermal conduction through the surrounding air. Other potential applications are sensors using the silicon sidewall electrodes as resistive or capacitive readout.
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TL;DR: The experimental results show that the sensitivity of the thermo-optic tuning is 34.231 W/RIU (refractive index units), and the measurement range is 4.325 × 10−3 RIU, almost eight times larger than that of the cascaded double micro-ring resonator without thermo -optic tuned for the intensity interrogation.
Abstract: In this paper, a thermo-optic tuning optical waveguide sensor system based on a cascaded double micro-ring resonator is investigated. The system consists of a micro-ring resonator with the microheater as a reference ring and a micro-ring resonator with removing the upper cladding layers as a sensing ring, combined with a microfluidic control. The refractive index change of the sample is measured by the electric power change of the microheater. The experimental results show that the sensitivity of the thermo-optic tuning is 34.231 W/RIU (refractive index units), and the measurement range is 4.325 × 10-3 RIU, almost eight times larger than that of the cascaded double micro-ring resonator without thermo-optic tuning for the intensity interrogation.
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25 Feb 2020
TL;DR: In this article, the authors exploited a new water-immersion FLM process to integrate high-quality singlemode waveguides (0.29 dB/cm propagation losses and 0.27 dB/facet coupling losses at 1550 nm) with two different types of thermally insulating microstructures: trenches on the sides of the heated photon path and a bridge waveguide, a structure in which the ablation is performed also under the optical path.
Abstract: Femtosecond laser micromachining (FLM) is a powerful technique that allows for rapid and cost-effective fabrication of photonic integrated circuits (PICs), even when a complex 3D waveguide geometry is required. Among the features of these devices, it is worth mentioning the possibility to dynamically reconfigure the circuit by thermal phase shifting. However, an integrated microheater dissipates more than 500 mW to induce a 2π phase shift in FLM devices operating at telecom wavelength (i.e. 1550 nm) and induces significant thermal crosstalk to adjacent devices. These issues prevent the integration of more than a few microheaters on the same chip. In order to cope with this, we exploited a new water-immersion FLM process to integrate high-quality single-mode waveguides (0.29 dB/cm propagation losses and 0.27 dB/facet coupling losses at 1550 nm) with two different types of thermally insulating microstructures: trenches on the sides of the heated photon path and a bridge waveguide, a structure in which the ablation is performed also under the optical path. Both the strategies are employed for the fabrication of compact reconfigurable Mach-Zehnder interferometers having inter-waveguide pitch down to 80 μm. Interferometers featuring insulating trenches show a reconfiguration period down to 57 mW, whilst bridge waveguides result in a further improvement, with a 2π phase shift that can be induced with an electrical power as low as 37 mW. Both structures reduce thermal crosstalk from more than 50% down to 3:5% on the nearest device.
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TL;DR: In this article, a photolithographic approach to pattern gold and copper-coated surfaces is presented, where the metal is selectively etched by light triggered local release of cyanide from a potassium ferrocya.
Abstract: A one-step photolithographic approach to pattern gold- and copper-coated surfaces is presented. The metal is selectively etched by light triggered local release of cyanide from a potassium ferrocya...