The system can generate different optical effects, colors and images by using different kinds of materials for the projection particles.
“They could be just about anything,” Smalley said. “Glass beads, diamonds, cellulose, tungsten — a wide variety of materials. What we've found most effective is a substance called black liquor, which is a byproduct of the paper manufacturing process. It's essentially just paper, cellulose. There's something about its density, shape, porosity, and absorbent spectrum that makes it work really well.”
Optical trapping itself is not new, Smalley said.
“Photophoretic trapping has been around for a long time and used for other applications,” he said. “It's good for isolating particles and moving something dangerous from one place to another place. We're attempting a new application of it.”
For now, Smalley concedes that the technique is relatively limited. Projected 3D images are very tiny indeed — smaller than your pinky nail. But the system can create larger “paper doll” images that appear two dimensional, even though they're technically a few dozen microns thick. In fact, the research team has generated a flat image of the original Princess Leia scene as an homage to the kind of sci-fi imagery that inspired the project in the first place.
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The challenge now, Smalley said, is to increase the size and resolution of the projected images. As to whether we will someday be able to generate those big sci-fi displays, Smalley is optimistic.
“I think we've got everything we need,” he said. “The first step is to optimize the trap and the particles. I suspect if we do a real methodical Edison-style survey of particles, we can come up with the best trap.”
Smalley hopes to improve the size and resolution of images by a factor of three or four in the near future. The real trick, he said, will be getting multiple projection systems to work in parallel and will allow for images much larger and more detailed that what can be generated now.
“Instead of trapping one particle at a time, we'll trap ten or a hundred or a thousand,” Smalley said. “It shouldn't be too difficult. Famous last words, I know.”
For now, Smalley said he will be content if he can just get people to stop calling his images holograms.
“I sure hope we can change that,” he said. “Because we end up spending the first 15 minutes of every talk trying to disambiguate these terms. It would make our lives a lot easier if we could improve this one thing.”
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