Using Science to Determine Clean Water’s Social Impact

Science usually yields scientific results — statistics, formulas, analysis. But what happens when these results are tested in a different environment? What happens when scientists studying methods to improve the globe’s clean water supply put their findings in a social context? For one thing, new insights arise, demonstrating, with greater importance, that clean water is essential to health.

This doesn’t just cover physical health, either. It mean stronger social communities and schools, stronger government and health care. Clean water touched so many sides of society that not having it seems remarkable. When scientists use the latest technology and apply it to social settings, we see why.

Recently nanotechnology has emerged as the favorite for science’s efforts to clean the world’s water supply. 

The single most important application of nanotechnology could be solving the global shortage of clean water – benefiting people in both industrialized and developing countries significantly.

A new podcast explores how Eric Hoek and his engineering research team at the University of California at Los Angeles, developed a new membrane using nanoparticles that promises to dramatically reduce the cost and energy needed to desalinate seawater and clean wastewater. In the near term, these membranes could work in municipal desalination plants in water-thirsty areas, such as those planned for the California coastline. In the future, this groundbreaking technology can be adapted to meet the clean water needs of poor countries and people who rely on low cost, decentralized water treatment systems.

Once these technologies are implemented, social groups high and low will enjoy an improved life. Culture and science go hand in hand not just because one makes the other better, but because they both thrive off of each other. They work like two neighbors building a fence — together, sharing resources, anything can be achieved. Through the advancements of science and the strength of social settings, clean water can be achieved — and in our lifetime.

Nanowires key to future transistors, electronics

A new generation of ultrasmall transistors and more powerful computer chips using tiny structures called semiconducting nanowires are closer to reality after a key discovery by researchers at IBM, Purdue University and the University of California at Los Angeles.

The researchers have learned how to create nanowires with layers of different materials that are sharply defined at the atomic level, which is a critical requirement for making efficient transistors out of the structures.

“Having sharply defined layers of materials enables you to improve and control the flow of electrons and to switch this flow on and off,” said Eric Stach, an associate professor of materials engineering at Purdue.

Electronic devices are often made of “heterostructures,” meaning they contain sharply defined layers of different semiconducting materials, such as silicon and germanium. Until now, however, researchers have been unable to produce nanowires with sharply defined silicon and germanium layers. Instead, this transition from one layer to the next has been too gradual for the devices to perform optimally as transistors.

The new findings point to a method for creating nanowire transistors.

The findings are detailed in a research paper appearing Friday (Nov. 27) in the journal Science. The paper was written by Purdue postdoctoral researcher Cheng-Yen Wen, Stach, IBM materials scientists Frances Ross, Jerry Tersoff and Mark Reuter at the Thomas J. Watson Research Center in Yorktown Heights, N.Y, and Suneel Kodambaka, an assistant professor at UCLA’s Department of Materials Science and Engineering.

Whereas conventional transistors are made on flat, horizontal pieces of silicon, the silicon nanowires are “grown” vertically. Because of this vertical structure, they have a smaller footprint, which could make it possible to fit more transistors on an integrated circuit, or chip, Stach said.

“But first we need to learn how to manufacture nanowires to exacting standards before industry can start using them to produce transistors,” he said.

Nanowires might enable engineers to solve a problem threatening to derail the electronics industry. New technologies will be needed for industry to maintain Moore’s law, an unofficial rule stating that the number of transistors on a computer chip doubles about every 18 months, resulting in rapid progress in computers and telecommunications. Doubling the number of devices that can fit on a computer chip translates into a similar increase in performance. However, it is becoming increasingly difficult to continue shrinking electronic devices made of conventional silicon-based semiconductors.

“In something like five to, at most, 10 years, silicon transistor dimensions will have been scaled to their limit,” Stach said.

Transistors made of nanowires represent one potential way to continue the tradition of Moore’s law.

The researchers used an instrument called a transmission electron microscope to observe the nanowire formation. Tiny particles of a gold-aluminum alloy were first heated and melted inside a vacuum chamber, and then silicon gas was introduced into the chamber. As the melted gold-aluminum bead absorbed the silicon, it became “supersaturated” with silicon, causing the silicon to precipitate and form wires. Each growing wire was topped with a liquid bead of gold-aluminum so that the structure resembled a mushroom.

Then, the researchers reduced the temperature inside the chamber enough to cause the gold-aluminum cap to solidify, allowing germanium to be deposited onto the silicon precisely and making it possible to create a heterostructure of silicon and germanium.

The cycle could be repeated, switching the gases from germanium to silicon as desired to make specific types of heterostructures, Stach said.

Having a heterostructure makes it possible to create a germanium “gate” in each transistor, which enables devices to switch on and off.

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The work is based at IBM’s Thomas J. Watson Research Center and Purdue’s Birck Nanotechnology Center in the university’s Discovery Park and is funded by the National Science Foundation through the NSF’s Electronic and Photonic Materials Program in the Division of Materials Research.

Writer: Emil Venere, (765) 494-4709, venere@purdue.edu

Source: Eric Stach, (765) 494-1466, eastach@purdue.edu

Related Web site:

Eric Stach: https://engineering.purdue.edu/MSE/People/ptProfile?id=12299

PHOTO CAPTION:

Researchers are closer to using tiny devices called semiconducting nanowires to create a new generation of ultrasmall transistors and more powerful computer chips. The researchers have grown the nanowires with sharply defined layers of silicon and germanium, offering better transistor performance. As depicted in this illustration, tiny particles of a gold-aluminum alloy were alternately heated and cooled inside a vacuum chamber, and then silicon and germanium gases were alternately introduced. As the gold-aluminum bead absorbed the gases, it became “supersaturated” with silicon and germanium, causing them to precipitate and form wires. (Purdue University, Birck Nanotechnology Center/Seyet LLC)

A publication-quality image is available at http://news.uns.purdue.edu/images/+2009/stach-nanowires.jpg

Abstract on the research in this release is available at: http://news.uns.purdue.edu/x/2009b/091126Stachnanowires.html