Microheater

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

Effects of Noncondensable Gas and Subcooling on the Spray Cooling of an Isothermal Surface

Abstract: Spatially resolved heat transfer measurements have been made on a nominally isothermal surface that is spray cooled. The effects of dissolved gas and subcooling were studied. The local measurements were obtained using a microheater array with ninety-six heaters each about 700 microns in size. The heater array consisted of thin-film platinum resistors deposited on a quartz substrate. Electronic feedback circuits were used to keep each of the heaters at a constant temperature and the voltage required to do this was measured. The array was cooled with FC-72 using a spray nozzle from ISR. The heat transfer data was correlated with high-speed images of the flow structure obtained from below. In this paper, heat transfer mechanisms in spray cooling will be discussed, with a particular emphasis on the effects of a non-condensable gas on critical heat flux in comparison to the comparable effects of thermally subcooling the liquid prior to atomization. NOMENCLATURE

Liquid phase transmission electron microscopy with flow and temperature control

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

Design and fabrication of thin-film aluminum microheater and nickel temperature sensor

Abstract: This paper presents development of a thin film aluminum microheater and a nickel temperature sensor for low temperature applications by using Micro-Electro-Mechanical Systems. Both of them are fabricated onto a glass substrate and protected by thin PDMS membrane. The microheater is energized to find sensor characteristic. As linearity and accuracy of nickel sensor give a wide temperature range, its electrical resistance variations are calibrated directly by temperatures of energized microheater. Variations of resistance signal are transformed and fed back to control temperature of microheater in PI closed-loop feedback control. K p and K i values are adjusted to obtain the optimal time response. Experimental testing of controlled temperature ranges from 40°C to 140°C is presented for their integration in stability system.

A Polysilicon Flow Sensor For Gas Flowmeters

Abstract: We have developed a one-wire type thermal flow sensor that has a polysilicon microheater. It has very wide flow measurement range of 0.005-35m/s and very short response time of 0.14ms (90%). The size of the flow sensor chip is 1mm x 1mm x O.3mm. The sensitivity is above 22mV/(m/s)/sup 1/2/ when it is operated by constant resistance mode. Consuming electric power to keep the temperature rise of the microheater 80K in windless air at 22/spl deg/C under atmospheric pressure is about 6mW. As the polysilicon has large resistivity, large output signals can be gotten without amplifiers. It can be applied to household gas flowmeters and other systems.

Thermal Phase Transition of an Aqueous Poly(N-isopropylacrylamide) Solution in a Polymer Microchannel-Microheater Chip

Abstract: Plastic microchannel-microheater chips were fabricated on the basis of imprinting and photolithography/etching techniques. Knowing the temperature-dependent fluorescence lifetime of Rhodamine B in water, the temperature profile of the solution phase in the microchannel in the vicinity of the heater was evaluated by space- and time-resolved fluorescence microspectroscopies. The fabricated chip was then applied to control the thermal phase transition of an aqueous poly(N-isopropylacrylamide) (PNIPAM) solution. PNIPAM particle formation by the phase transition was controlled by both the applied voltage to the heater and the solution-flow rate. The temperature profile showing below or above the phase-transition temperature (i.e., 32 °C) and solution-flow profile in the microchannel were visualized successfully on the basis of the PNIPAM particle formation. The continuous and automated concentration of a hydrophobic solute by the PNIPAM particles produced by the phase transition was also explored under solutio...