Microheater Device Research Articles

Enhanced ozone gas detection with Sb doped ZnO nanorods synthesized on MEMS microheater

Metal oxide semiconductors infused with noble metals or metalloids are studied and employed in semiconductor sensors applications to a greater extent. In this study, antimony (Sb) is doped with ZnO in 4 different concentrations to compare the optimal parameters in gas sensing properties. Sb/ZnO nanostructure is synthesized by hydrothermal process and deposited on MEMS (Micro electro mechanical system) microheater device. The morphology of the nanostructure is analyzed for planar structure, oxidation states and the presence of Sb/ZnO is successfully verified. Ozone is a powerful oxidizing gas which is a health hazard in public places, so low concentrations of ozone is tested with Sb/ZnO sensor at various parameters. Since Sb acts as catalyst to promote the gas sensing properties, the sensor responses have been enhanced compared to pure ZnO sensor. Sensor performed its best at 200 °C and has the lowest detection gas concentration of 10 ppb. Sb/ZnO showed good selectivity over ozone gas.

Electrically Tunable Steganographic Nano-Optical Coatings.

Thin film coatings with tunable colors have a broad range of applications, from solid-state reflective displays to steganography. Here, we propose a novel approach to chalcogenide phase change material (PCM)-incorporated steganographic nano-optical coatings (SNOC) as thin film color reflectors for optical steganography. The proposed SNOC design combines a broad-band and a narrow-band absorber made up of PCMs to achieve tunable optical Fano resonance in the visible wavelength, which is a scalable platform for accessing the full-color range. We demonstrate that the line width of the Fano resonance can be dynamically tuned by switching the structural phase of PCM from amorphous to crystalline, which is crucial for obtaining high-purity colors. For steganography applications, the cavity layer of SNOC is divided into an ultralow loss PCM and a high index dielectric material with identical optical thickness. We show that electrically tunable color pixels can be fabricated using the SNOC on a microheater device.

Double-Layered NiO/SnO2 Sensor for Improved SO2 Gas Sensing with MEMS Microheater Device

Micro Electro mechanical systems (MEMS) sensor is fabricated for testing low concentration gas sensing of sulphur dioxide (SO2) with sensing layers of single layer tin oxide (SnO2) and double layered heterojunction structure of nickel oxide and tin oxide (NiO/SnO2). NiO and SnO2 structures are deposited with RF sputtering and the elemental composition were identified with structural properties such as X-ray diffraction (XRD), Scanning electron microscope (SEM) and Energy Dispersive X-ray Analysis (EDX) analysis. Sensing results proved that NiO/SnO2 double layered sensor had better sensing characteristics than single layered SnO2 sensor due to the formation of p-n junctions. At 400 ppb of SO2 gas concentration, NiO/SnO2 sensor has maximum sensing response of 20% is recorded and at 2000 ppb, 30% sensing response is recoded. The optimal temperature of the sensor is 250 °C (∼63 mW). Selectivity of the sensor is tested with 5 different gases such as VOC, pyruvate, CO, NH3, SO2 and the sensor has high and better response with SO2 gas.

Ultra-low power MEMS micro-heater device

In this paper, we propose a simple design for the heating device with ultra-low power consumption. The device is composed of a micro heater made of Nichrome (20/80) alloy, designed in simple meander shape covering the total surface of S = (1.25 × 104) × (102) µm2. Deposited in thin films with a thickness of 1 µm on square silicon membrane of 14 × 102 µm side and 10 µm of thickness. We used the COMSOL Multiphysics 4.3 a tool for simulation. We achieved a maximum temperature of 900 K by applying 1.5 V of voltage. For gas sensing, the temperature of 707 K is generated at 1.25 V of voltage while the power consumption is 1.25 µW. The maximum relative stress is 3.5 109 N/m2 at 1.5 V. However, at 1.25 V we have less stress of 109 N/m2 and 9.107 × 10− 3 N/m2 for the interface thermo-mechanical strain resulting in good reliability for the device. Finally, the total displacement for the membrane is 50 µm as a maximum when 1.5 V is applied and 35 µm at 1.25 V. this device is perfectly adapted for mobile application as gas sensing and IoT systems.

Development of a high throughput micro-heater array with controllable temperature for each heating unit

In this paper, we propose a high throughput micro-heater array in which the temperature of each heating unit can be controlled separately and independently. First, a micro-heater with 3-layer structure is designed and the optimization is made to simplify the wire connection within the micro-heater array to compact the device size. For the device fabrication, the 3 × 3 micro-heater array is fabricated using MEMS fabrication technology. Furthermore, a novel two-state method is developed to control the heating pattern of the device with outstanding advantages. With this method, heating units in the array can be selectively heated and each unit can be well-controlled simultaneously under different temperatures. Measurement results demonstrate the good performance of the micro-heater unit and functionality of the micro-heater array device, which can be applied to versatile fields with a promising future.

Development of a Novel 2-Dimensional Micro-Heater Array Device with Regional Selective Heating

<p class="1Body">This paper reports the development of a micro-heater array device that can be selectively heated at an arbitrary location. To confirm the heating characteristics of this micro-heater array device, heating experiments using a thermo-responsive gel were conducted. Since a micro-heater can supply heat with a rapid-response on a micro-scale, various applications have been studied. Based on these characteristics, micro-heaters have often been used in recent research applications involving biological cells. To expand the versatility of the micro-heater, the development of micro-heater array systems that can supply heat selectively at an arbitrary location is required. In this work, to support micro-heater applications in the field of biochemistry, the design and materials of a micro-heater array device were optimized and a fabrication process was established. Furthermore, the usefulness of this device was verified using a thermo-responsive gel, and control of the temperature distribution on a glass substrate was successfully demonstrated. This micro-heater array device can be heated with regional selectivity, and each region can be controlled to an arbitrary temperature, so the device is also capable of generating temperature gradients.<strong></strong></p>

Direct Laser Patterning of a Gas Sensor on Flexible Substrate

Flexible gas sensor fabricated by direct laser patterning and its gas sensing properties towards ozone and ammonia are reported. The flexible platform consists in Ti/Pt interdigited electrodes for gas detection and a microheater device. The platform validation has been realized by thermal simulation and its electrical properties have been also studied. The gas sensing properties were investigated using a commercial ink of ZnO nanoparticles at several concentrations and temperatures. The sensor presents excellent responses toward ammonia and ozone at 300 °C and 200 C° respectively, with good reproducibility, and fast response and recovery time in a wide range of concentrations.

Developing heatable microfluidic chip to generate gelatin emulsions and microcapsules

The heatable microfluidic chip developed herein successfully integrates a microheater and flow-focusing device to generate uniform-sized gelatin emulsions under various flow rate ratios (sample phase/oil phase, Q s/Q o) and driven voltages. The gelatin emulsions can be applied to encapsulate vitamin C for drug release. Our goal is to create the thermal conditions for thermo-sensitive hydrogel materials in the microfluidic chip and generate continuous and uniform emulsions under any external environment. The gelatin emulsion sizes have a coefficient of variation of <5 % and can be precisely controlled by altering the flow rate ratio (Q s/Q o) and driven voltage. The gelatin emulsion diameters range from 45 to 120 μm. Moreover, various sizes of these gelatin microcapsules containing vitamin C were used for drug release. The developed microfluidic chip has the advantages of a heatable platform in the fluid device, active control over the emulsion diameter, the generation of uniform-sized emulsions, and simplicity. This new approach for gelatin microcapsules will provide many potential applications in drug delivery and pharmaceuticals.

Temperature Control of Microheaters for Localized Carbon Nanotube Synthesis

The temperatures of microheater devices for the localized growth of carbon nanotubes (CNTs) were brought under control to a great extent by providing the appropriate electric load (direct current or voltage) to the microheater circuit. The electrical-thermal coupled field simulations show that high temperatures only appear in very local areas under certain electric load. The infrared image of the produced microheater device agrees well with the simulation results. By applying the selected current to the fabricated microheater device and providing the mixed reaction gases, long, dense, and vertically well aligned CNT bundles were successfully grown very locally on the substrate. The control of temperatures paves the way to the localized growth of CNTs with good compatibility with CMOS process, and thus facilitating the direct integration of CNTs into future micro/nano electronics as interconnects. What's more, the method will also excite more in depth investigations on the applications of microheaters in many other fields.

Electrophoretic deposition of amphiphilic diacetylene supramolecules: polymerization, selective immobilization, pattern transfer and sensor applications

We describe the results of electrophoretic deposition characteristics of a conjugated polymer, polydiacetylene (PDA), that reveal film forming behavior, polymerization effects, pattern transfer capabilities, and fluorescence based thermo/mechano-responsive features of the deposited layer. The electric field applied in a two electrode system promotes the oriented motion of diacetylene (DA) supramolecules in aqueous solution in a direction that is determined by the charge polarities of tailorable pendant groups on the DA monomers. Through this mechanism, electrophoretic deposition of DA supramolecules on a conductive layer takes place to yield vesicular clustered aggregates with continuous leaf-like morphologies. In addition, unusual conformational changes of the DA monomers during the deposition result in the formation of polymerized blue colored PDAs on the working electrode. Based on these properties, selective deposition of the supramolecules on pre-patterned templates and consequent pattern transfer to a flexible substrate can be utilized to fabricate PDA-based microarray sensors. The chromatic change of the vesicles induced by an applied mechanical stress during pattern transfer is found to be dependent on the side groups of the DA monomers. Owing to inherent non-fluorescence to fluorescence transition features of PDA supramolecules occurring as a response to thermal perturbations, electrophoretically deposited PDA vesicles are employed to monitor the temperature of a heat dispensing micro-heater device.

Theoretical and experimental investigation of spatial temperature gradient effects on cells using a microfabricated microheater platform

While the cellular interaction with the chemical microenvironment has been studied in detail in the past, the effect of thermal signals and gradients on cells is not well understood. While almost all biological macrosystems exhibit temperature sensitivity, this has not been studied much at the cellular level. The capability of precise control of temperature and heat flux at the scale of a few microns using microfabricated structures makes microelectromechanical systems (MEMS) ideal for investigating these effects. This work describes a MEMS-based microheater platform capable of subjecting surface-adhered cells to microscale temperature gradients. This microdevice comprises a free-standing thin film based microheater platform. The design and microfabrication of this microdevice are described. A thermal conduction model is developed in order to thermally characterize the microheater platform. Protocols for culturing cells on the microheater platform are developed, making it possible to adhere cells on the microheater surface and subject them to a desired spatial temperature gradient. Experiments demonstrating the spatial control of cell viability using the microheater device are described. This is followed by experiments that explore the possibility of cellular growth in response to thermal gradients, similar to chemotaxis. Thermotactic effect is well known at the organismal level. However, cells used in this work did not exhibit any thermotactic effect. A theoretical model for predicting cell response to a spatial temperature gradient in its microenvironment is proposed. The model is based on the effect of the temperature gradient on the chemical sensory process of the cell. The model predicts that in addition to the thermal gradient, the thermotactic effect also depends on a number of other parameters that have not been well characterized in the past. The microheater platform described in this work offers a fundamental new experimental tool with which to explore the interaction of cellular systems with their thermal microenvironment. The theoretical model of thermotaxis developed here furthers the understanding of the function of a cell as a thermal and chemical sensor.

Desenvolvimento de um micro-aquecedor para sistemas de análise química em fluxo: determinação espectrofotométrica de manganês em plantas

In this work a micro-heater device to be used as an integral part of the flow analysis manifold is described. The usefulness of the device was demonstrated using it in the development of a multicommutated flow analysis procedure for the spectrophotometric determination of manganese in plant digest. The method was based on the manganese oxidation by periodate in phosphoric acid medium to form the permanganate anion. The reaction development is dependent on the temperature and it was observed that at 25 °C a time interval of ca. 15 min was necessary for the reaction to attain equilibrium. Setting the temperature to 70 oC, this time interval could be decreased to ca. 30 s. This condition was easily attained employing the proposed micro-heater device coupled to the manifold. The procedure was applied to manganese determination in soybean digests and results compared with those obtained by inductively coupled argon plasma optical emission spectrometry (ICP-OES). No significant difference at 90% confidence level was observed. A linear response for sample concentrations ranging from 5.0 to 30.00 mg L-1 Mn2+; a relative standard deviation of 1.3% (n = 6) for a typical sample containing 6.3 mg L-1 Mn2+; a sampling rate of 22 determinations per hour; a low reagent consumption, of 12.0 mg NaIO4 per determination; and a detection limit of 1.2 mg L-1 were achieved.