Sep 28, 2015 | By Benedict
Scientists at the University of Florida developed a way to print detailed soft structures from a 3D printer. The new 3D printer is able to print traditionally ‘impossible’ shapes, such as a thin tube tied in a knot. The process involves injecting inks into a gel that solidifies and traps the inks in place, with the end product being a soft yet sturdy structure. The researchers believe that this technique overcomes several limits of 3D printing, and could be useful for tissue engineering, providing invaluable aid to neurosurgeons and cancer researchers.
3D-printed jellyfish. Image by Tapomoy Bhattacharjee and Kyle Schulze.
The team of researchers behind the project looked to combat the problem of instabilities, or the tendency of the 3D printed object to deform after it is 3D printed because of surface tension, gravity, and particle diffusion. To address the problem, the team of researchers, led in part by Thomas Angelini, assistant professor in the department of mechanical and aerospace engineering at the University of Florida, took advantage of the physical properties of a commercially available granular hydrogel made up of 7µm-wide particles (Carbopol EDT 2020).
The gel, similar to common hand sanitizer, minus alcohol and perfume, is able to rapidly switch from a solid to liquid state in response to stress. Angelini likens this effect to the way that sugar can appear both solid and fluid depending on physical impact: “Stick your finger down there, drag it through, those grains can flow. It temporarily fluidizes it. Take your finger out, it becomes a solid again.”
Using the gel as a matrix material for 3D printing combats the problems associated with solid and liquid equivalents. A more solid matrix could easily be damaged by the moving parts of a 3D printer, whilst a liquid one would not be able to support a detailed structure. By using the granular gel, researchers were able to make far more complex structures than were previously possible, because the gel can support the incomplete structure as it is being 3D printed. Researchers now can inject different materials out of the 3D printer’s nozzle to draw structures. These materials can include anything from silicone polymers to living cells. Then, once 3D printed, the gel can simply be gently washed away, leaving the 3D printed object intact. Although there is a risk of very tiny molecules slipping past the individual grains of gel, most of the materials that the researchers are interested in working with are more big enough for this to not be a serious problem.
Writing solid shells and capsules
“Whatever it is that comes out of the nozzle is trapped in space wherever we place it,” explained Angelini. “So 3D printing is no longer a game of making a solid material that has to support itself; it’s now a game of trapping stuff in space and leaving it wherever you want to put it.”
Angelini explains that the concept of embedded 3D printing - a material being printed into a liquid or solid substance rather than empty space - is something researchers have been trying to perfect for years, and for good reason. "It changes the way you think about 3D printing," he says. "It goes from being about melting certain materials and limiting yourself to structures that can't collapse while being printed to just placing those objects in 3D space wherever you want. And so long as you can push a material out of a needle—and have it be trapped by the [matrix]—there's no limit to what you could print with."
Over the past year, the team has used the machine to 3D print complex shapes shapes with seven different types of living cells, including primary cells grown from a patient. Angelini and co were able to produce a kind of silicone jellyfish and suspended networks of veins written entirely out of living human aortic cells. Impressively, their 3D printer can print at a resolution of ~1 micron, or 1% the width of a human hair. This high level of precision is why the researchers are confident in their 3D printer’s ability to contribute to the building of flexible electronics and assisting organ and tissue engineering.
For further information, the team’s research paper can be found here.
Posted in 3D Printing Applications
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