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

Mitotic entry in the presence of DNA damage is a widespread property of aneuploidy in yeast

Genetic instability is a hallmark of aneuploidy in budding and fission yeast. All aneuploid yeast strains analyzed to date harbor elevated levels of Rad52-GFP foci, a sign of DNA damage. Here we investigate how continuously elevated levels of DNA damage affect aneuploid cells. We show that Rad52-GFP foci form during S phase, consistent with the observation that DNA replication initiation and elongation are impaired in some aneuploid yeast strains. We furthermore find that although DNA damage is low in aneuploid cells, it nevertheless has dramatic consequences. Many aneuploid yeast strains adapt to DNA damage and undergo mitosis despite the presence of unrepaired DNA leading to cell death. Wild-type cells exposed to low levels of DNA damage exhibit a similar phenotype, indicating that adaptation to low levels of unrepaired DNA is a general property of the cell's response to DNA damage. Our results indicate that by causing low levels of DNA damage, whole-chromosome aneuploidies lead to DNA breaks that persist into mitosis. Such breaks provide the substrate for translocations and deletions that are a hallmark of cancer

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

Phonon Transport Across a Vacuum Gap

Phonon transport across a silicon/vacuum-gap/silicon structure is modeled using lattice dynamics calculations and Landauer theory. The phonons transmit thermal energy across the vacuum gap via atomic interactions between the leads. Because the incident phonons do not encounter a classically impenetrable potential barrier, this mechanism is not a tunneling phenomenon. While some incident phonons transmit across the vacuum gap and remain in their original mode, many are annihilated and excite different modes. We show that the heat flux due to phonon transport can be 4 orders of magnitude larger than that due to photon transport predicted from near-field radiation theory

Topological signature of deterministic chaos in short nonstationary signals from an optical parametric oscillator

Although deterministic chaos has been predicted to occur in the triply resonant optical parametric oscillator (TROPO) fifteen years ago, experimental evidence of chaotic behavior in this system has been lacking so far, in marked contrast with most nonlinear systems, where chaos has been actively tracked and found. This situation is probably linked to the high sensitivity of the TROPO to perturbations, which adversely affects stationary operation at high power. We report the experimental observation in this system of a burst of irregular behavior of duration 80 microseconds. Although the system is highly nonstationary over this time interval, a topological analysis allows us to extract a clearcut signature of deterministic chaos from a time series segment of only 9 base cycles (3 microseconds). This result suggests that nonstationarity is not necessarily an obstacle to the characterization of chaos

Are transnational tobacco companies' market access strategies linked to economic development models? A case study of South Korea.

Transnational tobacco companies (TTCs) have used varied strategies to access previously closed markets. Using TTCs' efforts to enter the South Korean market from the late 1980s as a case study, this article asks whether there are common patterns in these strategies that relate to the broader economic development models adopted by targeted countries. An analytical review of the existing literature on TTCs' efforts to access emerging markets was conducted to develop hypotheses relating TTCs' strategies to countries' economic development models. A case study of Korea was then undertaken based on analysis of internal tobacco industry documents. Findings were consistent with the hypothesis that TTCs' strategies in Korea were linked to Korea's export-oriented economic development model and its hostile attitude towards foreign investment. A fuller understanding of TTCs' strategies for expansion globally can be derived by locating them within the economic development models of specific countries or regions. Of foremost importance is the need for governments to carefully balance economic and public health policies when considering liberalisation

Violation of the string hypothesis and Heisenberg XXZ spin chain

In this paper we count the numbers of real and complex solutions to Bethe constraints in the two particle sector of the XXZ model. We find exact number of exceptions to the string conjecture and total number of solutions which is required for completeness.Comment: 15 pages, 7 Postscript figure