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ILP Institute Insider

June 23, 2014

Harnessing the Speed of Light

Nicholas Fang pushes the limits of light to improve performance in communication, fabrication, and medical imaging.

Steve Calechman

The fields of data communication, fabrication and ultrasound imaging share a common challenge when it comes to improving speed and efficiency. That obstacle is light’s diffraction limit. Nicholas Fang thinks his group might have found a solution.

Nicholas Fang
MIT Associate Professor
Mechanical Engineering
“In my group we play tricks with optics,” says the MIT Associate Professor of Mechanical Engineering. The playing has led to findings that allow for generating three dimensional microstructures, using graphene as a more efficient delivery channel, and creating a new lens that would produce intense ultrasonic energy. With the ability to focus and target light onto the nanoscale, not only would data communication become quicker, but also the diagnosis and treatment of disease would transform into something that’s more precise, less invasive, less cumbersome and more cost effective than what’s available in current approaches.

Narrowing the Target
The key element of Fang’s work is his discovery of how to beat the diffraction of light. Since light and sound waves tend to spread out when blocked by an obstacle, images and communication signals can become blurry and muddled. What Fang has discovered in his lab is that by breaking the diffraction barrier, light signals can be sent at 10 times more capacity. This has allowed him to produce results on the sub-nanometer scale, with light as a machining tool providing “a new degree of precision,” he says.

The benefits are two-fold. First, such technology could allow printing electronic circuits using more manageable and less expensive equipment. Currently to produce nanoscale features on computing chips, an extreme UV light source is needed. The investment costs can be in the hundreds of millions of dollars, Fang says. With new, high-resolution optics that can print nanoscale elements on the wafer scale, set up costs can decreases to hundreds of thousands.

Second, the technology also provides the means to print and generate biosensors and scaffolding for tissue growth for something like an artificial liver and artificial tumor models. When it comes to drug and drug therapy, screening would become faster and delivery more precise. The eventual goal, Fang says, is the creation of nano-robots and nano-devices that would be able to flow into the blood stream and not only detect malicious cells at an early stage but also create a long-term self-sustained care system that’s not possible at this point in time.


A Smarter Optical Fabric for Chips
Fang says that he’s particularly excited about the potential to control and deliver a large bundle of light signals for communication over a small area. Increasing the downloading speed of data is nothing new. It’s continually happening, but the ramifications of Fang’s work reach past getting videos on a smartphone in under thirty seconds and work on a much smaller processing level. Now the improvement means that same amount of data can be handled and exchanged across different chips, he says.

“Our vision is the cell phone will eventually be replaced by wearable devices,” says Fang, noting the existence already of Pebble and Google Glass. By replacing breakable elements with flexible ones, a better user experience will be created by being able to provide a more visual life that’s more transparent, portable and energy efficient, he says.

The hope could lie in transmitting light on chips with graphene. Light itself is a marvelous carrier of information, Fang says, because it’s not limited by bandwidth and signals don’t necessarily interfere with each other. The only problem is that the diffraction limit creates a bottleneck in which close signals can start bending towards each other. Think of a highway with everyone trying to exit at the same place at the same time. To prevent this kind of jamming with information, each signal needs to maintain its own identity.

This is where graphene comes in. The electronic benefits of the carbon-based material are already known, but the optical properties remain untapped. Graphene is 10 times faster optically than electronically and can guide light in a dense and precise way, keeping signals in their own channel, in a sense, making light look like a motorcycle rather than a big van, Fang says. With a reduced size, more signals can be driven in the same field. “We could use graphene as our information highway,” he says.

One big question that remains is how much power is needed to drive each bit, but the potential is that the technology could be used in Intel or IBM chips, increasing the amount of data capacity while decreasing the amount of time to respond to information requests. The end product? A smarter chip, Fang says.

Seeing Cells through the Body
One other project coming out of Fang’s lab takes his knowledge of optics and applies them to acoustics and ultrasound. Being able to generate intense ultrasonic energy would break up specific cells or cell membranes and inject drug particles into them. The challenge, once again, is the diffraction limit. Available medical devices can go down to half a millimeter, but individual cells are in micrometers. The need is to overcome 10 times the lens change in order to treat or cure one particular cell.

Fang says his research holds the possibility; he’s shown to be able to generate a flat lens that can deliver acoustic energy into a tightly focused spot – a healthy cell could be differentiated from a malignant one and therapy could be targeted. A physician collaborator is still needed to build a suitable test that would gain eventual FDA approval, but Fang says that he’s excited about the potential. The device would be more precise – a large fiber bundle wouldn’t be needed to penetrate the body’s tissue – and would only need a fraction of the power that’s currently used. “We do consider this medical ultrasound innovation could be less invasive and it could be less painful for the patients,” he says.