technizzel

Associate Professor Giri Venkataramanan (center) and a team of workers built a wind turbine in the Scottish Highlands. The community there is not connected to the electrical grid. (Large image)

The rolling hills of the Scottish highlands are dotted with small stone houses. Their residents, mostly farmers and craftsmen, enjoy a peaceful existence miles from the nearest city—so far, in fact, that they are not connected to the nearest power grid.

That is where Electrical and Computer Engineering Associate Professor Giri Venkataramananbegan his sabbatical. He did not travel to Scotland to enjoy its peace and tranquility, but rather as part of a team building an electricity-generating wind turbine. Without connection to energy utilities—power lines cost between $50,000 and $1 million per mile, says Venkataramanan—the region’s inhabitants must generate their own power.

Wind turbines, machines that use the energy from the wind to turn a generator, are common in the area. “Every house has one or two turbines. They also use solar panels and have batteries to store charge for when there’s no wind or sun,” says Venkataramanan. “They live pretty comfortably.”

The team had no prior turbine-building experience, but came prepared to saw, drill and weld. It took the team one week to build the turbine, by hand, from the raw materials. Turbines the size of this one generally average 200 watts at a reasonably windy site. At this rate, one turbine can generate enough electricity in a day to power the modest needs of a small home, says Venkataramanan.

“That was a very eye-opening experience for me. Even in that primitive setting, we were able to accomplish something. I was quite impressed,” says Venkataramanan. “I thought, we ought to do something like that on campus.”

Inspired by that thought, he spent the rest of his sabbatical learning how to implement a program about this clean, sustainable solution for rural energy on a university campus.

A few months after returning from Scotland, Venkataramanan traveled to the Tokyo Institute of Technology to lecture about his research activities. While he was there, he investigated a new undergraduate program in international development engineering, which focuses on sustainable global development.

Venkataramanan then spent three months as a visiting research associate at the University of California-Berkeley. While conducting research and writing a paper on rural electrification for the Journal of Energy Engineering, he also assembled a team of students to build a wind turbine like the one he built in Scotland. Although without a full-scale workshop or credit, the students worked weekends to assemble the turbine in a team member’s garage.

The students’ enthusiasm for the project did not wane after Venkataramanan’s departure, and the workgroup continues to meet. “Since I left Berkeley, they’ve developed more wind-focused activities and are planning to install two or three more wind turbines,” he says.

While at UC-Berkeley, Venkataramanan also visited other schools and institutions focused on sustainable energy development. The efforts he witnessed inspired him, such as the University of Colorado-Denver student team that not only built a wind turbine, but also installed it in a tribal community in India.

For the spring of 2006, Venkataramanan received a fellowship as a visiting researcher at the Federal University of Minas Gerais (UFMG) in Belo Horizonte, Brazil. “The first thing I did in Brazil was get a bunch of students together to build a wind turbine,” he says. Despite bureaucratic red tape, the team found the parts it needed and finished the turbine.

To finish his sabbatical, Venkataramanan spent the summer as a visiting scientist at Gazi University in Ankara, Turkey, where he also recruited a team of students to build another wind turbine, bringing his number of construction endeavors to four. With these experiences fresh in his mind, he returned to UW-Madison in fall armed with ideas for ways Wisconsin students could help develop rural energy.

Venkataramanan is planning several courses that will give students opportunities to learn about and work with energy technology. This spring, he piloted a section of Introduction to Engineering (InterEgr 160) that focuses on small-scale wind turbines, intending to integrate it into the curriculum long-term. He also has integrated renewable energy technologies and developing electric grids into his ECE 714 course, Utility Applications of Power Electronics, focusing on under- developed and off-grid communities.

Venkataramanan (right) helped a team of students in Brazil build a smaller scale wind turbine like the one he built in Scotland. He also built turbines with student groups in Turkey and California. (Large image)

To give students hands-on experience, Venkataramanan is planning a section of the service-learning program Engineering Projects in Community Service that will enable them to build and install a renewable energy system, such as wind turbines, in an off-grid community.

Venkataramanan believes that adding rural, renewable energy development to an engineering curriculum could make a difference not only for the students involved and the communities they reach, but also on a global level. “There are two billion people without electricity access in the world. That’s one-third of the population. Many of these communities don’t have economic wealth for people to go and build power lines. By engaging our students in projects like this, they can learn to think globally and perhaps come up with creative solutions for the future,” he says. “The potential for what our students and faculty can do is unlimited; we just have to be creative.”

An artistic rendition of a smart liquid microlens where a stimuli-responsive hydrogel (dark circular ring) regulates the shape of the liquid lens (center). The liquid microlens autonomously adapts to local environmental stimuli (denoted by small spheres and yellow plasma rays outside the hydrogel) in microfluidics. The stimuli can be biological and chemical agents, and physical parameters (light, temperature, pH, electric field, etc.) (Large image

When Hongrui Jiang looked into a fly’s eye, he saw a way to make a tiny lens so “smart” that it can adapt its focal length from minus infinity to plus infinity — without external control.

Incorporating hydrogels that respond to physical, chemical or biological stimuli and actuate lens function, these liquid microlenses could advance lab-on-a-chip technologies, optical imaging, medical diagnostics and bio-optical microfluidic systems.

Jiang, an assistant professor of electrical and computer engineering and biomedical engineering; Biomedical Engineering Professor David Beebe; postdoctoral researcher Liang Dong; and doctoral student Abhishek Agarwal described the technology in the cover story of the Aug. 3 issue of the journal Nature.

David J. Beebe (Large image)

At this size — hundreds of microns up to about a millimeter — variable focal length lenses aren’t new; however, existing microlenses require external control systems to function, says Beebe. “The ability to respond in autonomous fashion to the local environment is new and unique,” he says.

In a lab-on-a-chip environment, for example, a researcher might want to detect a potentially hazardous chemical or biological agent in a tiny fluid sample. Using traditional sensors on microchips is an option for this kind of work — but liquid environments often aren’t kind to the electronics, says Jiang.

That’s where hydrogels — thick, jellylike polymers — are important. Researchers can tune a hydrogel to be responsive to just about any stimulus parameter, including temperature and pH, says Jiang. So as the hydrogel “senses” the substance of interest, it responds with the programmed reaction. “We use the hydrogel to provide actuation force,” he says.

A water-oil interface forms the group’s lens, which resides atop a water-filled tube with hydrogel walls. The tube’s open top, or aperture, is thin polymer. The researchers applied one surface treatment to the aperture walls and underside, rendering them hydrophilic, or water-attracting. They applied another surface treatment to the top side of the aperture, making them hydrophobic, or water-repelling. Where the hydrophilic and hydrophobic edges meet, the water-oil lens is secured, or pinned, in place.

When the hydrogel swells in response to a substance, the water in the tube bulges up and the lens becomes divergent; when the hydrogel contracts, the water in the tube bows down and the lens becomes convergent. “The smaller the focal length, the closer you can look,” says Jiang.

Because they enable researchers to receive optical signals, the lenses may lead to new sensing methods, he says. Researchers could measure light intensity, like fluorescence, or place the lenses at various points along a microfluidic channel to monitor environmental changes. “We’ve also thought about coupling them to electronics — that is, using electrodes to control the hydrogel,” says Beebe. “Then you can think about lots of imaging applications, like locating the lenses at the ends of catheters.”

Clustered in an array, the lenses also could enable researchers to take advantage of combinatorial patterns and provide them with more data, he says.

The array format improves upon the natural compound eye, found in most insects and some crustaceans. This eye essentially is a sphere comprised of thousands of smaller lenses, each of which has a fixed focal length. “Since the lenses are fixed, an object has to be a certain distance away for it to be clearly seen,” says Jiang. “In some sense, our work is actually better than nature, because we can tune the focal length now so we can scan through a larger range of view field.”

Fabricating lenses is a straightforward, inexpensive process that takes just a couple of hours. The real advantage, however, is their autonomous function, says Jiang. “That forms a universal platform,” he says. “We have a single structure and we can put different kinds of hydrogels in and they can be responsive to different parameters. By looking at the outputs of these lenses, I know what’s going on in that location.”

Electrical and Computer Engineering Graduate Student Hao-Chih Yuan holds a sample of a semiconductor film on plastic. (Large image)

New thin-film semiconductor techniques invented by UW-Madison engineers promise to add sensing, computing and imaging capability to an amazing array of materials.

Historically, the semiconductor industry has relied on flat, two-dimensional chips upon which to grow and etch the thin films of material that become electronic circuits for computers and other electronic devices. But as thin as those chips might seem, they are quite beefy in comparison to the result of a new University of Wisconsin-Madison semiconductor fabrication process detailed in the Journal of Applied Physics.

A team led by Electrical and Computer Engineering Assistant Professor Zhenqiang (Jack) Ma and Materials Science and Engineering Professor Max Lagally developed a process to remove a single-crystal film of semiconductor from the substrate on which it is built. This thin layer (only a couple of hundred nanometers thick) can be transferred to glass, plastic or other flexible materials, opening a wide range of possibilities for flexible electronics. In addition, the semiconductor film can be flipped as it is transferred to its new substrate, making its other side available for more components. This doubles the possible number of devices that can be placed on the film. By repeating the process, layers of double-sided, thin-film semiconductors can be stacked together, creating powerful, low-power, three-dimensional electronic devices.

“It’s important to note that these are single-crystal films of strained silicon or silicon germanium,” says Ma. “Strain is introduced in the way we form the membrane. Introducing strain changes the arrangement of atoms in the crystal such that we can achieve much faster device speed while consuming less power.”

For non-computer applications, flexible electronics is beginning to have significant impact. Solar cells, smart cards, radio frequency identification (RFID) tags, medical applications, and active-matrix flat panel displays could all benefit from the development. The techniques could allow flexible semiconductors to be embedded in fabric to create wearable electronics or computer monitors that roll up like a window shade. “This is potentially a paradigm shift,” says Lagally. “The ability to create fast, low-power, multilayer electronics has many exciting applications. Silicon germanium membranes are particularly interesting. Germanium has a much higher adsorption for light than silicon. By including the germanium without destroying the quality of the material, we can achieve devices with two to three orders of magnitude more sensitivity.”

That increased sensitivity could be applied to create superior low-light cameras, or smaller cameras with greater resolution. Ma, Lagally, Materials Science and Engineering Assistant Professor Paul Evans, Physics Associate Professor Mark Eriksson, and graduate students Hao-Chih Yuan and Guogong Wang are patenting the new techniques through the Wisconsin Alumni Research Foundation. The team’s work was supported in part by grants from the National Science Foundation Materials Research Science and Engineering Center, the Department of Energy and the Air Force Office of Scientific Research.

In roughly four minutes, the UW-Madison Steel Bridge Team can construct an 18-foot-long bridge that easily holds 2,500 pounds.

That lightning-fast time is the product of hundreds of hours of preparation and hard work by a group that, for more than a decade, has been a regular National Student Steel Bridge Competition regional winner and national championship contender.

2005-06 Steel Bridge Team

The steel bridge competition challenges university teams around the country to design, fabricate, test and build a steel bridge within certain spatial and structural constraints. Teams strive to earn the lowest overall score based on their performance in six categories: bridge appearance and poster display, construction speed and time penalties, construction economy, lightness, stiffness, and structural efficiency.

For the 2007 competition, a fictitious state department of transportation is seeking to replace a century-old bridge that spans a river and adjacent floodway. Each team must design a 1:10 scale model and erect it under simulated field conditions to demonstrate its concept. At that scale, the river width is 9 feet; the bridge may be up to 4 feet wide and span between 18 and 20 feet.

Constructing the bridge during competition (Large image)

Among the restrictions: A single component, or “member,” can weigh no more than 20 pounds and may be no larger than 3 feet long by 6 inches square. During assembly, each member must connect directly to every member it touches by at least one steel bolt and hexagonal nut combination.

Construction takes place in a 95-by-15-foot area, including a 15-foot-square staging area on either end. The construction team, which can include up to six builders and one superintendent, may not cross the river while building the bridge.

The competition is fierce and the margin of error is very small. At the 2003 national competition, for example, the team placed in the top three in five of the six categories, yet missed a first-place finish by two seconds of construction time. In 2006, bridge deflection was greater than the group expected, yet the team scored well in other categories and took home a third-place finish—its second-best showing in the national competition since the event began in 1992.

Naturally, the team is excited about its design for the 2007 competition— particularly since it incorporates the fewest number of components possible. “It performs fairly similar to other ones with a lot more members,” says current team co-chair Adam Bechle, a civil and environmental engineering junior. “We picked this one because there wasn’t a huge difference in the structural stability.”

To simulate loads, weight and deflection, team members analyze the bridge using a computer program called SAP 2000. “We have hundreds of thousands of lines of data that it prints, and we figure out where we need to pull that data so that we can figure out the deflections we need,” he says.

While a civil engineering background is helpful for members hoping to shape the bridge design, the Steel Bridge Team is open to anyone, says Bechle. Team members learn how to operate machine-shop tools and fabricate small bridge parts, including connectors like sleeves, pins or dovetails. Per a broad interpretation of competition rules, such innovations circumvent the need for a time-consuming bolt-and-nut combination.

During the university winter break, about 10 students put in 12-hour days at Endres Manufacturing in Waunakee. The company purchases materials for the team and “loans” them an experienced welder and its machining facilities for a week. “We don’t know how we would fabricate the bridge if it weren’t for them,” says Bechle.

Once the bridge is finished, the “athletes” take over. Working initially for three or four hours on Saturday afternoons in the Engineering Centers Building, the construction crew choreographs the most efficient way to assemble the bridge. “We put painter’s tape on the floor and set up the yard exactly like it says in the rules,” says Bechle.

The crew first walks through the assembly, noting restrictions in the rules about how many people can be in the construction area at a time, where they can and cannot step, and how they can handle and place bridge members. By the time the builders have run through the assembly several times, they sprint into and out of the construction area like dancers in a wild musical production. Before the competition, these students will have assembled and disassembled their bridge more than 100 times.

In practice as well as in competition, their focus is unwavering and the intensity is high. It truly is a sport—and one that combines creativity, ingenuity and mental and physical agility, says Bechle. “You can win a national championship, whereas in high school sports, you can win a conference championship, or something like that,” he says. “Here, you’re competing against the best people in the nation.”

Bechle joined the team as a freshman and says a benefit of membership is that it has provided him a way to apply his engineering knowledge outside the classroom. The team’s culture of mentorship gave him an opportunity to learn from and now, to teach, his fellow students. In addition, he says, employers appreciate his leadership role. “If you’re looking for an engineering job, you’re going to be solving problems and working in teams,” he says. “You know—it’s exactly what you do here.”