all Mazur Group stories

Harvard launches wireless classroom

70652986 — Mon, 26 Mar 2007 06:24:42 -0400

It's not what you'd expect a college classroom to sound like, especially at Harvard. It's as noisy as a singles bar on a Friday night. Students are talking to those beside them and in the rows in front and behind them. Some of the conversations are heated. Many students are clicking what look like TV remote control devices. Some are using cell phones or huddled over laptop computers. The teacher, Eric Mazur, Gordon McKay Professor of Applied Physics, checks his cell-phone screen to see how the students are doing.

It seems more like chaos than class. But Mazur sees this as the classroom of the future, where students teach one another with the help of wireless technology.

"I cannot make people learn," he says. "Learning is a hard process. Students have to do it by themselves. I see myself as an available and encouraging coach. If I can use technology to facilitate that role, I think it's marvelous."

The technology he talks about includes a Web site that students can access, in class or outside, with wireless devices such as cell phones, laptops, and personal digital assistants. On the screens are questions that Mazur expects only about half of them can answer. Those questions provoke animated discussions.

The questions are shaped by misconceptions that Mazur looks for and then corrects. The students learn the right answers from one another.

Mazur wants students to learn in the classroom, instead of spending their time writing in notebooks. With wireless communication, teachers will not be confined to the front of the class, tied to blackboards and slide projectors. "That is what classrooms will be like in 2010," he predicts.

Physics 1b at Harvard is not quite there yet. The University does not require students to buy Web-enabled cell phones or laptops, so those who don't have them use remote control "clickers" to register their answers on screens at the front of the room.

"We developed a hybrid system that lets us have a wireless classroom in 2006 instead of waiting until 2010 when all students will carry wireless devices with them," Mazur says.

Harvard started using clickers in 1998. Now the infrared gadgets are used in colleges all over the world in courses ranging from physics and economics to art and French drama. That's a path Mazur sees cell phones and laptops following.

Light propagates via wires more slender than its own wavelength

70652986 — Mon, 26 Mar 2007 05:33:37 -0400

A research team led by Harvard's Eric Mazur and Limin Tong, a visiting professor from Zhejiang University in China, reported on their work with nanowires in the Dec. 18, 2003 issue of the journal Nature. "You wouldn't normally imagine that a baseball could pass through a garden hose, but these nanowires appear able to handle exactly that kind of wide load," says Mazur, Harvard College professor, Gordon McKay Professor of Applied Physics, and professor of physics. "In some cases light is propagating along wires just one-third the width of its own wavelength. It's almost as if the wire serves as a rail to guide the light rather than funneling it in the traditional sense." The wires could aid in the development of optical chips that operate more rapidly and efficiently than today's electronic chips. The tiny structures could also be used to manipulate cells and other microscopic objects. The wires are so fine that they could poke into a cell or a droplet of liquid without disrupting them, yet are extremely sturdy - several times stronger than spider silk, one of the gold standards in the world of materials.

Surgery done on a single cell

70652986 — Mon, 26 Mar 2007 05:33:20 -0400

A superprecise scalpel that can be used to operate on an individual cell is now a reality thanks to experimenters at Harvard University. "Ultrashort laser pulses [up to 1,000 a second] produce a spot as hot as the sun," notes Eric Mazur, Gordon McKay Professor of Applied Physics. "Normally, that kind of heat would vaporize a cell, but it only shines for a millionth of a billionth of a second. The light intensity is very high, but the energy generated in such a short time can be compared to a mosquito bumping into your arm. A cell can easily take that." A laser beam ordinarily travels right through a piece of glass or a transparent cell, but in this application it is focused into a very, very small space within a cell. "It's like lighting a hot spark inside the cell without disturbing the surface membrane, the fragile bag that holds the cell together," Mazur says. An exacting technique like this opens up a plethora of medical possibilities. The Harvard researchers vaporized a single mitochondrion, a minute biological motor that provides power to a cell to carry out its many functions. They cleaved a single nerve in a tiny roundworm, knocking out the creature's sense of smell.

New use found for black silicon

70652986 — Mon, 26 Mar 2007 05:15:59 -0400

In 1999, Harvard researchers used laser pulses to etch the surface of silicon, the most common substance used in electronic devices. By accident, they created a material that efficiently traps light. Called black silicon, it holds amazing potential for efficiently converting sunlight to electricity, for communicating by light, and for monitoring the environment for evidence of pollution and global warming. Now, a Harvard graduate student has discovered another use for black silicon. When placed in a strong electric field, the substance emits electrons with surprising efficiency.

Black silicon: A new way to trap light

70652986 — Mon, 26 Mar 2007 05:04:34 -0400

Eric Mazur, Harvard College Professor and Gordon McKay Professor of Applied Physics, and his students were studying what kinds of new chemistry can occur when lasers shine on metals, like platinum. One day, they decided to put a chip of gray silicon into a vacuum chamber, add some halogen gas, and scan it with ultrashort, ultra-intense laser pulses. Each pulse lasted a mere 100 millionths of a billionth of a second. However, the energy in a single pulse approximates focusing all the sunlight hitting Earth at one time onto a space the size of a fingernail. After more than 500 pulses, the silicon turned black. It wasn't burned; rather, its surface had been etched by the heat and gas into a dazzling forest of billions of minute needlelike spikes.