Microheater

About: Microheater is a research topic. Over the lifetime, 814 publications have been published within this topic receiving 12478 citations.

A thermal microfluidic actuator based on a novel microheater

Abstract: Microfluidic actuators based on thermally-induced actuation are gaining intense attraction due to their usage in disease diagnosis and drug release-related devices. These devices use a thermally-expandable polymer called Expancel that expands once its temperature exceeds a particular threshold value. Achieving such devices that are cost-effective and consume low input power is crucial for attaining efficacy. Therefore, the need for a low-energy consuming actuator necessitates the improved configurations of microheaters that provide the required heat. We report a novel topology of a copper-based microheater called square-wave meander, exhibiting a 44% higher output temperature, showing high actuation efficiency, as compared to the conventionally used meander design. The reason for increased temperature with low input energy is attributed to increased resistance by a jagged structure while maintaining the same surface area, i.e. without changing the effective thickness of the microheater. Numerical modeling demonstrates the comparison of temperature and electric potential contours for reported and conventionally used microheaters. We reveal the merit of the reported design by comparing the volumetric thermal strains for both designs. We experimentally demonstrate the increased expansion of 25% for the reported design at the same applied current of 200 mA and faster operation time. Later, we show the microfluidic actuator device integrated into the microheater and poly-dimethylsiloxane-Expancel, controlling the operation/actuation of a fluid through a microchannel. This work might improve the performance of the advanced microfluidic-based drug release and other fluid-based applications.

Reduction of thermal emission background in high temperature microheaters

Abstract: High temperature microheaters have been designed and constructed to reduce the background thermal emission radiation produced by the heater. Such heaters allow one to probe luminescence with very low numbers of photons where the background emission would overwhelm the desired signal. Two methods to reduce background emission are described: one with low emission materials and the other with interference coating design. The first uses platforms composed of material that is transparent to mid-infrared light and therefore of low emissivity. Heating elements are embedded in the periphery of the heater. The transparent platform is composed of aluminum oxide, which is largely transparent for wavelengths less than about 8 μm. In the luminescent microscopy used to test the heater, an optical aperture blocks emission from the heating coils while passing light from the heated objects on the transparent center of the microheater. The amount of infrared light transmitted through the aperture was reduced by 90% as the aperture was moved from the highly emissive heater coils at 450 °C to the largely transparent center at the same temperature. The second method uses microheaters with integrated multilayer interference structures designed to limit background emission in the spectral range of the low-light luminescence object being measured. These heaters were composed of aluminum oxide, titanium dioxide, and platinum and were operated over a large range of temperatures, from 50 °C to 600 °C. At 600 °C, they showed a background photon emission only 1/800 that of a comparison heater without the multilayer interference structure. In this structure, the radiation background was sufficiently reduced to easily monitor weak thermoluminescent emission from CaSO4:Ce,Tb microparticles.

A highly sensitive Pt-doped ZnO based Ethanol sensor

Abstract: A chemoresistive sensor for ethanol with Pt-microdots doped zinc oxide (ZnO) thin film as sensing layer has been studied with a coplanar microheater architecture with inter-digitated electrodes (IDE's) ZnO thin films are fabricated using the sol-gel method The doping with platinum is performed by RF Sputtering method The present study suggests the use of a coplanar microheater with IDE's fabricated for the ethanol sensor Further, the effect of doping on sensing properties of the sensor has been studied The sensing response of the sensor with the film thickness of 430 nm at an operating temperature of 180°C comes out to be 110 The prime aim of the study is to present a highly sensitive ethanol sensor having a coplanar architecture of microheater with IDE's in a ZnO based sensor

High-performance gas sensing by chemically modified 3D graphene hydrogel

Abstract: For the first time, we develop a high performance, cost-effective gas sensor by exploiting 3D chemically functionalized reduced graphene oxide hydrogel (FRGOH). The self-assembly and chemical modification of 3D FRGOH are realized using hydroquinone molecules in a simple, one-step hydrothermal synthesis process. Compared with an unmodified RGOH counterpart, the chemically derived FRGOH sensor not only displays twofold higher sensitivity in both nitrogen dioxide and carbon dioxide sensing, but also exhibits significantly faster recovery and lower limit of detection (LOD). Importantly, the integrated microheater is employed not only to significantly improve the selectivity of nitrogen dioxide sensing by elevating substrate temperature, but also to accelerate the response and recovery.