Seeing in Stereo: Engineers Invent Lens for 3-D Microscope

Seeing in Stereo: Engineers Invent Lens for 3-D Microscope

  1:44:00 AM    Science Lover

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Engineers at Ohio State University have invented a lens that enables microscopic objects to be seen from nine different angles at once to create a 3-D image.

A lens invented at Ohio State University 
enables microscopes to capture 3-D images 
of tiny objects. (Credit: Photo by Kevin 
Fitzsimons, courtesy of Ohio State University.)

Other 3-D microscopes use multiple lenses or cameras that move around an object; the new lens is the first single, stationary lens to create microscopic 3-D images by itself.

Allen Yi, associate professor of integrated systems engineering at Ohio State, and postdoctoral researcher Lei Li described the lens in a recent issue of the Journal of the Optical Society of America A.

Yi called the lens a proof of concept for manufacturers of microelectronics and medical devices, who currently use very complex machinery to view the tiny components that they assemble.

Though the engineers milled their prototype thermoplastic lens on a precision cutting machine, the same lens could be manufactured less expensively through traditional molding techniques, Yi said.

"Ultimately, we hope to help manufacturers reduce the number and sizes of equipment they need to miniaturize products," he added.

The prototype lens, which is about the size of a fingernail, looks at first glance like a gem cut for a ring, with a flat top surrounded by eight facets. But while gemstones are cut for symmetry, this lens is not symmetric. The sizes and angles of the facets vary in minute ways that are hard to see with the naked eye.

"No matter which direction you look at this lens, you see a different shape," Yi explained. Such a lens is called a "freeform lens," a type of freeform optics.

Freeform optics have been in use for more than a decade. But Lei Li was able to write a computer program to design a freeform lens capable of imaging microscopic objects.

Then Yi and Li used a commercially available milling tool with a diamond blade to cut the shape from a piece of the common thermoplastic material polymethyl methacrylate, a transparent plastic that is sometimes called acrylic glass. The machine shaved bits of plastic from the lens in increments of 10 nanometers, or 10 billionths of a meter -- a distance about 5,000 times smaller than the diameter of a human hair.

The final lens resembled a rhinestone, with a faceted top and a wide, flat bottom. They installed the lens on a microscope with a camera looking down through the faceted side, and centered tiny objects beneath the flat side.

Each facet captured an image of the objects from a different angle, which can be combined on a computer into a 3-D image.

The engineers successfully recorded 3-D images of the tip of a ballpoint pen -- which has a diameter of about 1 millimeter -- and a mini drill bit with a diameter of 0.2 millimeters.

"Using our lens is basically like putting several microscopes into one microscope," said Li. "For us, the most attractive part of this project is we will be able to see the real shape of micro-samples instead of just a two-dimensional projection."

In the future, Yi would like to develop the technology for manufacturers. He pointed to the medical testing industry, which is working to shrink devices that analyze fluid samples. Cutting tiny reservoirs and channels in plastic requires a clear view, and the depths must be carved with precision.

Computer-controlled machines -- rather than humans -- do the carving, and Yi says that the new lens can be placed in front of equipment that is already in use. It can also simplify the design of future machine vision equipment, since multiple lenses or moving cameras would no longer be necessary.

Other devices could use the tiny lens, and he and Li have since produced a grid-shaped array of lenses made to fit an optical sensor. Another dome-shaped lens is actually made of more than 1,000 tiny lenses, similar in appearance to an insect's eye.

This research was sponsored by the National Science Foundation. Moore Nanotechnology Systems in Keene, NH, provided the ultraprecision milling machine.

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New Generation of Superplastics

New Generation of Superplastics

  1:20:00 AM    Science Lover

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Scientists are reporting an in-depth validation of the discovery of the world's first mass producible, low-cost, organoclays for plastics. The powdered material, made from natural clay, would be a safer, more environmentally friendly replacement for the compound widely used to make plastics nanocomposites.

A substance made from natural clay (shown), the 
material used to make pottery, may be spinning its 
way toward use as an inexpensive, eco-friendly 
replacement for a compound widely used to make 
plastic nanocomposites. (Credit: iStockphoto/
Henry Chaplin)

A report on the research appears in ACS' Macromolecules, a bi-weekly journal.

Miriam Rafailovich and colleagues focused on a new organoclay developed and patented by a team of scientists headed by David Abecassis. The scientists explain that so-called quaternary amine-treated organoclays have been pioneering nanoparticles in the field of plastics nanotechnology. Just small amounts of the substances make plastics flame retardant, stronger, and more resistant to damage from ultraviolet light and chemicals. They also allow plastics to be mixed together into hybrid materials from plastics that otherwise would not exist.

However, quaternary amine organoclays are difficult to produce because of the health and environmental risks associated with quaternary amines, as well as the need to manufacture them in small batches. These and other disadvantages, including high cost, limit use of the materials.

The new organoclay uses resorcinol diphenyl phosphate (which is normally a flame retardant), to achieve mass producible organoclays which can be made in continuous processing. In addition these organoclays are cheaper, generate less dust, and are thermostable to much higher temperatures (beyond 600 degrees Fahrenheit). This clay has also been proven to be superior for flame retardance applications. In addition, unlike most quaternary amine based organoclays, it works well in styrene plastics, one of the most widely used kinds of plastic.

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Plastic Electronics Could Slash the Cost of Solar Panels

Plastic Electronics Could Slash the Cost of Solar Panels

  11:01:00 PM    Science Lover

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A new technique developed by Princeton University engineers for producing electricity-conducting plastics could dramatically lower the cost of manufacturing solar panels.

Plastic transistor Princeton researchers have developed a new way to manufacture electronic devices made of plastic, employing a process that allows the materials to be formed into useful shapes while maintaining their ability to conduct electricity. In the plastic transistor pictured here, the plastic is molded into interdigitated electrodes (orange) allowing current flow to and from the active channel (green). (Credit: Loo Research Group)

By overcoming technical hurdles to producing plastics that are translucent, malleable and able to conduct electricity, the researchers have opened the door to broader use of the materials in a wide range of electrical devices.

With mounting concerns about global warming and energy demand, plastics could represent a low-cost alternative to indium tin oxide (ITO), an expensive conducting material currently used in solar panels, according to the researchers.

"Conductive polymers [plastics] have been around for a long time, but processing them to make something useful degraded their ability to conduct electricity," said Yueh-Lin Loo, an associate professor of chemical engineering, who led the Princeton team. "We have figured out how to avoid this trade-off. We can shape the plastics into a useful form while maintaining high conductivity."

A multi-institutional team reported on its new technique in a paper published online March 8 in the Proceedings of the National Academy of Sciences.

The area of research, known as "organic electronics" because plastics are carbon-based like living creatures, holds promise for producing new types of electronic devices and new ways of manufacturing existing technologies, but has been hampered by the mysterious loss of conductivity associated with moldable plastics.

"People didn't understand what was happening," said Loo, who co-wrote the paper. "We discovered that in making the polymers moldable, their structures are trapped in a rigid form, which prevented electrical current from traveling through them."

Once they understood the underlying problem, Loo and her colleagues developed a way to relax the structure of the plastics by treating them with an acid after they were processed into the desired form.

Using the method, they were able to make a plastic transistor, a fundamental component of electronics that is used to amplify and switch electronic signals. They produced the electrodes of the transistor by printing the plastic onto a surface, a fast and cheap method similar to the way an ink-jet printer produces a pattern on a piece of paper.

Loo said the technique potentially could be scaled up for mass production presses akin to those used to print newspapers. "Being able to essentially paint on electronics is a big deal," Loo said. "You could distribute the plastics in cartridges the way printer ink is sold, and you wouldn't need exotic machines to print the patterns."

By allowing plastic solar cells to be manufactured using low-cost printing techniques and by replacing ITO as the primary conducting material, the plastics the team developed hold potential for lowering the cost of solar panels.

Currently, the electricity generated by plastic solar cells is collected by a transparent metal conductor made of ITO. The conductor must be transparent so that sunlight can pass through it to the materials in solar cells that absorb the light energy.

A rare and pricey byproduct of mining, ITO had come under increasing demand for use in flat-screen televisions, mobile phones and other devices with display screens. "The cost of indium tin oxide is skyrocketing," Loo said. "To bring down the costs of plastic solar cells, we need to find a replacement for ITO. Our conducting plastics allow sunlight to pass through them, making them a viable alternative."

The researchers anticipate that the plastics also could replace expensive metals used in other electronic devices, such as flexible displays. In addition, the scientists are beginning to explore the use of the plastics in biomedical sensors that would display a certain color if a person had an infection. For instance, the plastics turn from yellow to green when exposed to nitric oxide, a chemical compound produced during ear infections in children.

If the devices could be produced at a low cost, they might be useful in developing countries that lack advanced medical facilities. "You wouldn't need any fancy machines or lab equipment to diagnose an infection," Loo said, "all you would need is your eyes to see the color change in the plastics."

The co-authors of the paper were Joung Eun Yoo, who received her doctorate in chemical engineering from the University of Texas-Austin in 2009 with Loo as her adviser; Kimberly Baldwin, a high school student who spent a summer in Loo's lab; Jacob Tarver, a Princeton chemical engineering graduate student; Enrique Gomez of Pennsylvania State University; Kwang Seok Lee and Yangming Sun of the University of Texas-Austin; Andres Garcia and Thuc-Quyen Nguyen of the University of California-Santa Barbara; and Hong Meng of DuPont Central Research and Development.

The research was supported by the National Science Foundation, the W.M. Keck Foundation and the Arnold and Mabel Beckman Foundation.

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