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Research: technology has the potential to change the way prosthetic products and spectacle lenses are designed and manufactured –

The new 3D printer uses light to convert gooey liquid to complex solid objects in minutes.

The nickname of "inventor replicator" – after Star Trek, which can materialize any object on demand – 3D printer can create objects that are smoother, more flexible and more complex than what is possible with traditional 3D printers. It can also wrap an already existing object with new materials – for example by adding a handle to a metal hexagonal shaft – which the existing printer is trying to do.

This technology has the potential to turn out how spectacle products to glasses are designed and manufactured, say researchers.

"I think it's a way to make things even more massive, whether it's prosthetic or running shoes," said Hayden Taylor, professor of mechanical engineering at the University of California at Berkeley, and the lead author of the book describes a printer that in the magazine it appears online today (January 31) Science.

"The fact that you could take a metal part or something from another manufacturing process and add it to customizable geometry, I think it can change the way the products are designed," Taylor said.

Most 3D printers, including other light-based techniques, create a 3D layer layer. The result is a "stair" effect along the edges. They also have difficulty creating flexible objects because flexible materials may become deformed during the printing process, and objects of certain shapes such as arches need to be printed.

The new printer relies on a viscous liquid that reacts to a solid when exposed to a certain threshold value. Designing carefully formed light patterns – essentially "films" – fills the desired shape "at once" on the rotating cylinder of the liquid.

"Basically, you have a video projector I've literally brought home, then plug it into your notebook and use it to display a series of calculated images while the engine rotates the cylinder that has the 3D-print resin in it," said Taylor. "Obviously there are a lot of fines – how you formulate a resin, and above all, how you calculate the images to be projected, but the obstacle to creating a very simple version of this tool is not so high."

Taylor and the team used the printer to create a series of objects, from the modest Rodin's statue "The Thinker" to the modified jaw model. At present, they can create objects up to a diameter of 4 inches.

"This is the first time we do not need to create layers of our own 3D parts by layer," said Brett Kelly, a co-author on paper who completed the work while a graduate student worked together at UC Berkeley and the Lawrence Livermore National Laboratory. "3D printing is truly three-dimensional."

CT scan – in the opposite direction

The new printer was inspired by a CT scan that can help doctors find tumors and fractures in the body.

The CT scan shows X-rays or other types of electromagnetic radiation in the body from all angles. Analysis of transmitted energy samples reveals the geometry of the object.

"Basically, we reversed this principle," Taylor said. "We try to create an object rather than measure an object, but in fact, a lot of underlying theory that allows us can be translated from the theory behind the computed tomography."

In addition to light modeling, which requires complex calculations to obtain precise shapes and intensities, the second major challenge scientists have dealt with is to formulate a material that remains fluid when exposed to a little light, but reacts to make it solid when exposed to a large amount of light.

"The fluid you do not want to cure will surely pass through the rays of light, so there must be a light exposure threshold for this transition from liquid to solid," Taylor said.

3D-print resin is composed of liquid polymers mixed with photosensitive molecules and dissolved oxygen. The light activates the photosensitive compound that depletes oxygen. Only in those 3D areas where all oxygen has been consumed the polymers form "crosslinks" that convert the resin from the liquid to the solid. Unused resin can be recycled by heating in an oxygen atmosphere, Taylor said.

"Our technology does not produce almost any material waste and uncured material is 100% reusable," said Hossein Heidari, a Taylor graduate student at UC Berkeley and co-author of the first paper. "This is another benefit of 3D printing without support."

Objects also need not be transparent. Scientists have printed objects that appear opaque when they use a dye that emits light at the curing wavelength but absorbs most other wavelengths.

"This is particularly satisfactory to me because it creates a new frame of volumetric or" all-to-one "3D printing that we have started to develop in recent years," said Maxim Shusteff, engineer at the Livermore Lab. "We hope it will open the way for many other scientists to explore this exciting technology area."

Indrasen Bhattacharya of UC Berkeley is the co-first author of the work. Other authors include Christopher M. Spadaccini of the National Lawrence Livermore National Laboratory.

This work was supported by the UC Berkeley Fund for Start-up Studies and Research and Development Funds managed by the National Lawrence Livermore National Laboratory. The team filed a patent application for this technique.

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