MEMS-based thermal management of high heat flux devices edifice: Embedded droplet impingement for integrated cooling of electronics

Increases in microprocessor power dissipation coupled with reductions in feature sizes due to manufacturing process improvements have resulted in continuously increasing heat fluxes. The ever increasing chip-level heat flux has necessitated the development of thermal management devices based on spray and evaporative cooling. This lecture presents a comprehensive review of liquid and evaporative cooling research applied to thermal management of electronics. It also outlines the challenges to practical implementation and future research needs. This presentation also describes the development of EDIFICE: Embedded Droplet Impingement For Integrated Cooling of Electronics. The EDIFICE project seeks to develop an integrated droplet impingement cooling device for removing chip heat fluxes over 100 W/cm2, employing latent heat of vaporization of dielectric fluids. Micro-manufacturing and MEMS (Micro Electro-Mechanical Systems) will be discussed as enabling technologies for innovative cooling schemes recently proposed. Micro-spray nozzles are fabricated to produce 50-100 micron droplets coupled with surface texturing on the backside of the chip to promote droplet spreading and evaporation. A novel feature to enable adaptive on-demand cooling is MEMS sensing (on-chip temperature, remote IR temperature and ultrasonic dielectric film thickness) and MEMS actuation. EDIFICE is integrated within the electronics package and fabricated using advanced micro-manufacturing technologies (e.g., Deep Reactive Ion Etching (DRIE) and CMOS CMU-MEMS). The development of EDIFICE involves modeling, CFD simulations, and physical experimentation on test beds. This lecture will then examine jet impingement cooling of EDIFICE with a dielectric coolant and the influence of fluid properties, micro spray characteristics, and surface evaporation. The development of micro nozzles, micro-structured surface texturing, and system integration of the evaporator will also be discussed

Design of a Low-Cost Infrared Sensor Array Through Thermal System Modeling,”

ABSTRACT The responsivity, sensitivity (signal-to-noise ratio), and cross talk of pyroelectric infrared sensor arrays are directly related to the thermal performance of the interconnect between sensor elements and readout electronics. Conventional low-cost designs, employing a film of sensor material like polyvinylidenefluoride (PDVF) layered on top of a silicon substrate, function by reading the electronic signal generated in the sensor when infrared radiation causes the sensor to heat up proportional to the radiation intensity. However, the change in temperature of the sensor material, and therefore signal generated, is highly dependent on the thermal properties of the interconnect material between the sensor and silicon substrate. A numerical framework for evaluating the effect of thermal conductivity and specific heat on sensor responsivity, sensitivity, and cross talk is developed. This allows us to analyze the relationships between feature size, thermal properties, and system performance. Using this model, a selection of materials from epoxies and other conventional solutions to emerging material systems such as nanoporous silica (aerogel) can be analyzed. Aerogel is most interesting since its thermal properties are 1-3 orders-of-magnitude better than conventional interconnect materials. Recent developments have also shown its compatibility with low-cost microelectronics fabrication and packaging techniques. The numerical model illustrates the potential of highly miniaturized pyroelectric infrared sensor arrays that have comparable performance at dramatically lower fabrication cost compared to conventional infrared sensor array technology

Thermal Conductivity Of Beta-Arsenene Under Biaxial Tensile Strain: A First Principle Study

A first principle study is conducted to explore the phonon thermal transport in a buckled arsenene monolayer (Beta-As) subjected to tensile strain. The results showed that the thermal conductivity first decreases with strains from 0% to 1%, then it increases with strains from 1% to 5%, and finally it decreases with strains from 5% to 9%. The maximum thermal conductivity occurs at strain of 5%, which is 1.45 times higher than that of unstrained arsenene. Phonon properties are investigated to understand the causes of this thermal response to strain

Modeling and simulation of a rollerball microfluidic device

The fluid delivery process through a rollerball device is investigated by means of physical modeling and numerical simulations. The microfluidic device is intended to deliver liquid above a substrate interacting with the surrounding air. While the fluid is delivered, air entrainment occurs through the capillary gap, creating a two-phase liquid-gas mixture whose composition and properties affect significantly the quality of the continuous fluid deposition. For the numerical solution of the 2D two-phase flow governing equations, the finite volumebased finite element method is used with 2nd order time-space schemes for the fully coupled system of equations. The quality of the liquid micro-volume delivery proves to be largely affected by both the speed of the roller and fluid properties. It is found that only under very low speed and some fluid properties, it is possible to guarantee a gas free liquid deposition. Envisioning the potential use of this convenient and popular device in the deployment of microfluid layers or substances at very small quantities with controlled quality, it is apparent the need for handling and channeling out the air entrainment without perturbing the liquid qualit

Multi-objective Optimization of Wind Farm Layouts Under Energy Generation and Noise propagation

Wind farm design deals with the optimal placement of turbines in a wind farm. Past studies have focused on energymaximization, cost-minimization or revenue-maximization objectives. As land is more extensively exploited for onshore wind farms, wind farms are more likely to be in close proximity with human dwellings. Therefore governments, developers, and landowners have to be aware of wind farms’ environmental impacts. After considering land constraints due to environmental features, noise generation remains the main environmental/health concern for wind farm design. Therefore, noise generation is sometimes included in optimization models as a constraint. Here we present continuous-location models for layout optimization that take noise and energy as objective functions, in order to fully characterize the design and performance spaces of the optimal wind farm layout problem. Based on Jensen’s wake model and ISO-9613-2 noise calculations, we used single- and multiobjective genetic algorithms (NSGA-II) to solve the optimization problem. Preliminary results from the biobjective optimization model illustrate the trade-off between energy generation and noise production by identifying several key parts of Pareto frontiers. In addition, comparison of single-objective noise and energy optimization models show that the turbine layouts and the inter-turbine distance distributions are different when considering these objectives individually. The relevance of these results for wind farm layout designers is explored