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Some of the greatest challenges of modern society are related to energy consumption, dissipation, and waste. Among these, present and future technologies based on nanoscale materials and devices hold great potential for improved energy conservation, conversion, or harvesting. A prominent example is that of integrated electronics, where power dissipation issues have recently become one of its greatest challenges. Power dissipation limits the performance of electronics from handheld devices (~10^–3 W) to massive data centres (~10⁹ W), all primarily based on silicon micro/nanotechnology.

Importantly, the figures for data centre energy consumption have doubled in five recent years, with waste heat requiring drastic cooling solutions. Such challenges are also evident at the individual micro-processor (CPU) level, where the race to increase operating frequency beyond a few GHz recently stopped when typical dissipated power reached 100 W/cm² (see figure below). Such electronic power and thermal challenges have negative impacts in areas from massive database servers to new applications like wearable devices, medical instrumentation, or portable electronics. In the latter situations, there is a basic trade-off between the available functionality and the need to carry heavy batteries to power it.

Despite tremendous progress over the past three decades, modern silicon transistors are still over three orders of magnitude (>1000×) more energy inefficient than fundamental physical limits. These limits have been estimated as approximately 3kBT ≈ 10^–20 J at room temperature for a binary switch with a single electron and energy level separation kBT, where kB is the Boltzmann constant and T is the absolute temperature. In the average modern microprocessor, the dissipated power is due, in approximately equal parts, to both leakage (or sleep) power and active (dynamic) switching power.

Power dissipation is compounded at the system level, where each CPU Watt demands approximately 1.5× more for the supply, PC board, and case cooling. Such power misuse is even more evident in systems built on otherwise power-efficient processors, e.g., in the case of the Intel Atom N270 (2.5 W power use) which is typically paired up with the Intel 945GSE chipset (11.8 W power use). At the other extreme, data centres require 50%–100% additional energy for cooling, which is now the most important factor limiting their performance, not the hardware itself.

Such energy challenges for the electronics infrastructure stem not only from the power supply side which calls for new energy sources, efficient batteries, or thermoelectrics, but also from the demand side, i.e., the need for more energy-efficient computing devices. Breakthroughs in our understanding and improvement of energy efficiency in nanoelectronics will have a global effect, impacting our energy supplies, budgets, and the environment.

On a broader scale, just over half the man-made energy in the world is wasted as heat (10¹³ W), from power plants and factories to car engines and the power bricks on our laptops. Efficiently reclaiming even a small percentage of such wasted heat would itself nearly satisfy the electricity needs of our planet. The fundamental issues at hand are, in fact, a two-sided problem: on one side, there is a significant need for low-energy computing devices, which is perhaps the biggest challenge in micro/nanoelectronics today. On the other side there is the challenge of waste heat dissipation, guiding, or conversion into useful electricity. On a large scale, a transistor twice as energy-efficient could lower power use by a significant percentage of the planet power budget. Such progress is crucial to maintaining progress in a post-CMOS world, and has great environmental implications as well.

Original article: Eric Pop, Energy Dissipation and Transport in Nanoscale Devices

Scientists at the University of Rochester have created a way to change the properties of almost any metal to render it, literally, black. The process, using an incredibly intense burst of laser light, holds the promise of making everything from fuel cells to a space telescope’s detectors more efficient.

“We’ve been surprised by the number of possible applications for this,” says Chunlei Guo, assistant professor of optics at the University of Rochester. “We wanted to see what would happen to a metal’s properties under different laser conditions and we stumbled on this way to completely alter the reflective properties of metals.”

The key to creating black metal is an ultra-brief, ultra-intense beam of light called a femtosecond laser pulse. The laser burst lasts only a few quadrillionths of a second (a femtosecond is to a second what a second is to about 32 million years).

During its brief burst, the laser unleashes as much power as the entire grid of North America onto a spot the size of a needle point. That intense blast forces the surface of the metal to form nanostructures: pits, globules, and strands. All of these nanostructures dramatically increase the area of the surface and help capture radiation.

Guo’s research team has tested the absorption capabilities for the black metal and confirmed that it can absorb virtually all the light that fall on it, making it pitch black. Regular metals absorb only a few percent of visible light.

The huge increase in light absorption enabled by Guo’s femtosecond laser processing means nearly any metal becomes extremely useful anytime radiation gathering is needed. For instance, detectors of all kinds, from space probes to light meters, could capture far more data than an ordinary metal-based detector could.

And turning a metal black without paint, scoring, or burning could easily lead to everyday uses such as replacing black paint on automobile trim.

Guo is also quick to point out that the nanostructures’ remarkable increase in a metal’s surface area is a perfect way to catalyze chemical reactions. Along with one of his research group members, postdoctoral student Anatoliy Vorobyev, he hopes to learn how the metal can help derive more energy from fuel cell reactions.

The new process has worked on every metal Guo has tried, and since it’s a property of the metal itself, there’s no worry of the black wearing off.

Currently, the process is slow. To alter a strip of metal the size of your little finger easily takes 30 minutes or more, but Guo is looking at how different burst lengths, different wavelengths, and different intensities affect metal’s properties. Fortunately, despite the incredible intensity involved, the femtosecond laser can be powered by a simple wall outlet, meaning that when the process is refined, implementing it should be relatively simple.

Original story on University of Rochester website