April 2, 2013

Special Edition: 3-D Printing

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3-D printing technology is evolving and expanding each day, and its uses are becoming more revolutionary with each new discovery in processing plastics, metals, food and body parts.

The origin of 3-D printing can be traced back to 1984, when Charles Hull, co-founder of 3-D Systems, invented stereolithography, an additive manufacturing process by which digital data can be used to form three-dimensional objects.

This process, colloquially known as 3-D printing, works by laying down successive layers of material in different configurations. 3-D printers read digital blueprints from animation modeling software and print the model as a series of cross sections. The layers are then fused together to create the final object.

3-D printing has a great deal of flexibility, allowing the user to print almost any shape or geometric feature. Advanced 3-D printers can even use a wide variety of materials in a single print, giving users more complex possibilities for production.

Plastics and Metals

3-D printing technology is often used for the printing of models, tools, and machine parts. However, the printing of plastics and metals is not limited to the fabrication of production parts. Prof. Jeff Clune, computer science, University of Wyoming, worked as a postdoctorate researcher in Cornell’s Creative Machines Laboratory with others to create Endlessforms.com, a website where the principles of 3-D printing are used to investigate the mechanisms of evolutionary biology. Endlessforms.com is a website that allows anyone in the world to design their own shapes that they can then 3-D print.

“We’ve had many different kinds of users, from college professors using it to teach evolution to 10-year-olds designing toys,” Clune said. “Just like you might breed dogs, you can breed shapes.”

At the core of the website is an evolutionary process that produces similar shapes to the ones selected. The “offspring” shapes resemble the “parent” shapes, but are not the same.

“You can guide evolution in a matter of minutes,” Clune said. “Evolution is the best engineer we know.”

Objects can also be 3-D printed in bronze, silver, or sandstone. When a user has finished designing a shape, the design is sent to Shapeways, a company specializing in 3-D printing, to be produced. Metal objects are constructed layer-by-layer with metallic dust, then hit with a laser to melt the object together in the desired places. Plastic objects are also printed in layers with droplets of liquid plastic, then hit with ultraviolet light to harden the object.

Since the website’s founding, over four million objects have been evaluated by users around the world. The website has been used by 50 to 60 thousand users from over 150 countries.

“It has been an international exploration,” Clune said. “Everything on the site was created by people from many different cultures.”.

Food

“One of the first uses of the open-source 3-D printer was printing chocolate,” said Prof. Hod Lipson, mechanical and aerospace engineering, co-founder of the Fab@Home project.

Fab@Home is an open-source 3-D printing project with the aim to produce a 3-D printer that anyone could build, experiment with and improve. Prior to this project, 3-D printers were used primarily in industrial settings and did not allow users to experiment with new materials or processes. Believing that this held back the potential of the industry, the Fab@Home project was started to make 3-D printing technology accessible to the public.

The 3-D printing of food was an outcome of open-sourcing the project. Instead of printing with plastics or metals, users could print with food materials such as chocolate, peanut butter, cheese, cookie dough, or any other substance that could fit through the print nozzle. The idea was to form these food materials into new, complex shapes and combinations that are difficult to achieve using conventional cooking methods.

For example, researchers were able to print a cake with a letter C baked inside of it, a challenging task for even experienced pastry chefs. 3-D printing also allows for the control of nutrition, such as easier control of sugar levels for diabetic users.

“3-D printed foods taste just like the real thing,” said Lipson. “Familiarity is very important with food. Using conventional food materials allows us to focus on new shapes and combinations of traditional recipes.”

According to Lipson, most processed foods can be 3-D printed. Foods that are unlikely to be successful in 3-D printing are unprocessed foods in their raw state, such as meat, fruits and vegetables.

Engineers in the Cornell Creative Machines Lab have nonetheless been able to use 3-D printing to print a variety of “lab meats,” such as scallop nuggets shaped like miniature buildings and space shuttles. These synthetic meats have the same texture as conventional meat, but do not come from living animals.

The 3-D printing of foods has a wide variety of practical applications. It is considered a possible remedy for menu fatigue, the loss of interest in eating that occurs when people are on a restricted diet. 3-D printing could also allow astronauts to take fairly small amounts of basic ingredients with them to outer space and combine them in many different ways.

“Having a large digital pantry can alleviate some of these challenges of food variety,” Lipson said.

3-D printing of food can also potentially be used in economically deprived areas where people may have access to only a few basic food materials. Using a 3-D printer would allow them to make the food more interesting and appetizing.

“A 3-D printer could turn a few alternative protein sources into a large variety of other foods,” Lipson said.

3-D printers in the home would be used for printing toys and printing food.

“3-D printing is slow, but compared to ordering something online, it’s very fast,” Lipson said. The use of 3-D printing technology would allow users to prepare complex foods without the expertise needed to prepare them through conventional cooking methods.

“It’s not just about cookies,” Lipson said. “The opportunities are endless.”

Ears

Deformation of the ear is not an uncommon injury or birth defect, but the current standard of surgical reconstruction often leaves patients dissatisfied with the finished product. Replacement ears are made from cartilage taken from the rib cage and shaped into an ear. This is then implanted on the side of the head, which just isn’t the same as a bona fide human ear.

“It’s a classic challenge in the tissue engineering field,” said Prof. Lawrence Bonassar, biomedical engineering.

Bonassar, along with a team of scientists and doctors from both Weill Medical School and the Department of Biomedical Engineering recently published a paper in PLOS ONE detailing their creation of a replica human ear using a 3-D printer and live cartilage and collagen cells.

It starts with a high-resolution image of an existing human ear, accurate to within 15 microns. From there, 3-D imaging software is used to design a seven- or eight-piece mold. The printing material used to make the mold in this case is collagen, the main structural protein in the body. The mold is then injected with cartilage cells and allowed to develop into a solid, substantial ear.

While the project used cartilage from cow ears, future applications of the technique would ideally use the patient’s own cells to grow a new organ.

“Cartilage cells tend to be easier to grow outside the body,” said Bonassar. This fact makes ears a good starting

point for engineering replacement organs.

According to Bonassar, cartilage cells can survive for a longer period of time without a blood supply than many other cell types, and cartilaginous structures tend to be simple, biologically speaking. The same technique used to create an ear could easily be applied to any number of other cartilage-based structures within the body, including joints and spinal cartilage. Bones would also be a fairly straightforward creation.

Internal organs such as livers and kidneys present a “different class of problems,” said Bonassar. These organs tend to have many different types of cells working together and would be more difficult to create artificially. But when it comes down to it “the printer works the same, the process works the same,” he said.

The potential benefits of an implant manufactured to a precise anatomic correctness using a patient’s own cells are immense. A 3-D printed ear would look completely natural and be accepted by the patient’s body and immune system.

The technique has yet to be perfected, however, and it could be several years before these ears are on the market.

“There are lots of very discreet hurdles that one has to overcome [before the treatment can get FDA approval],” Bonassar said. Once that happens, however, it could easily take off.

A 3-D printer is the ideal tool for tissue engineering thanks to its ability to “rapidly create complicated geometries” and easy customizability, Bonassar said.

A three dimensional, high resolution image of any human ear can be taken, modified and edited in image software, and given to the 3-D printer to create. The printer can take the complex shapes that are present in a human ear and use whatever material it is given to turn an image into a tangible object. According to Bonassar, what began as a living human ear could eventually develop into hearts, livers, kidneys, and many other organs in the future, making organ transplants more effective for generations to come.

Original Author: Kathleen Bitter

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