From theory to reality: College of Science delves into 3-D printing

October 7, 2015  

3-D printing

A Purdue "Motion P" is created using 3-D printing technology. (Photo provided)

As 3-D printers have become cheaper to produce, research has gone from creating practical objects for everyday use to encoding objects to foil cybercriminals. Perhaps one of the most promising areas of research is bioprinting of human parts for medical purposes. In the College of Science, researchers are exploring all of these areas and more.

One program uses the technology for multiple research efforts while another uses a printer to help build parts for analytical chemistry research instruments and initiatives.

Two 3-D printers are a large part of the Department of Computer Science's Visualization Laboratory, stationed on the third floor of the Lawson Computer Science Building. Professor Daniel Aliaga brought in two printers to fuel his research efforts. Layer by layer, the printers take spooled or powdered plastics to create objects. The objects can be a simple shape -- even a traditional Purdue P -- or it can be an algorithm created by Computer Science faculty brought into the three-dimensional world.

"Definitely, 3-D printing is increasing in popularity, even more so since 3-D printers are becoming cheaper and cheaper and more savvy," Aliaga says. "Many different things can be printed. One that I've been reading about is printing clothing, printing fabric. You control the specifics of where it's stronger, where it's weaker, how stretchable and bendable it is. It's not here yet but it's right around the corner. … There's dozens of materials you can use for 3-D printing. It's been really, really exploding the last few years."

Most common 3-D printers take spools of plastic and flow the material in the shape of a scanned object. The filaments are heated into a paste -- close to the consistency of toothpaste. The "paste" is heated up to more than 440 degrees as the object is modeled. The platform is kept at a toasty 240 degrees as the piece forms.

The scan of the object is imported into the machine with programs like 3-DSMax from Autodesk. The programs turn the scan into stacked "slices," which serve as maps for the printer heads to trace one by one. For experts like Aliaga, the scanning takes minutes while the actual printing takes an hour or more, depending on how large and complex the object is.

3-D printing in the life sciences

In the Department of Chemistry, graduate student Zane Baird's interest in 3-D came after a couple years working in Professor Graham Cooks' labs in the basement of Brown Laboratory. Baird helped form the Purdue 3-D Printing Club in 2013 and he pieced together his own printer for the lab. Based around components from a MakerFarm Prusa i3v model he inherited from the club, Baird's printer is used to build components for his analytical chemistry research. Recently, Baird was creating nylon extrusions, used to prepare surgical biopsies for analysis. The extrusions are scraped across slides to create smears for the pathologists for different kinds of cancer. The project is a collaboration with the Indiana University School of Medicine.

"We can prepare samples on demand and examine them using desorption electrospray ionization in the operating room," Baird says. "We take these and smear a small portion of tissue across a glass slide and then we have our DESI set up in front of a mass spectrometer. We scan across the tissue section and look at the chemical signatures and lipid profiles that come from this tissue. From that, with some statistical analysis, we can do diagnose cancer types, states and grades."

Over the years, Baird has worked diligently to improve the accuracy and speed of the printer.

"I added a bunch of improvements and changed the configuration," Baird says. "I use it to make life in the lab easier because there are a lot of little components that we have that are really specialized. Rather than go to the machine shop and have a longer turnaround time and make it a lot more expensive, this really simplifies the work process."

Baird published a paper from an experiment where he used conductive plastic hewn from the printer. The components were used in ion mobility spectroscopy. The work could improve airport security as similar methods are used for screening. 

Cooks, the Henry Bohn Hass Distinguished Professor of Chemistry, appreciates Baird's work, which has become valuable in prototyping parts for new and smaller mass spectrometers. Although sometimes the printed parts are "imprecise," the printer is a welcome new piece of equipment.

"It has allowed ideas to be tried very rapidly," Cooks says.

Top of the line

Aliaga's main piece of equipment in his work is the Objet Alaris 30. The printer uses plastic powder, layer by layer, that is selectively solidified by a laser within the machine to create fine, detailed pieces.

"The piece appears gradually on the platform," Aliaga says. "The platform lowers as the printer head moves back, forward, left, right. The object is then taken to a water station where the extra plastic is shot off."

The objects are light in weight but still impress. Aliaga is working on a project that creates  a three-dimensional watermark to adhere to objects like 3-D printed car parts.

"Some years ago, we got a grant to start exploring encoding information in 3-D objects," Aliaga says. "We want to differentiate a copy of the object from its original. Counterfeiting is actually a problem in industries, including the car industry. It's about a $10 billion a year loss due to that."

Infringers are skilled enough to add the logos and even serial numbers on counterfeit parts. Aliaga's work on 3-D printing watermarks looks to show differences between the real and the fake. Even if an object with a watermark is copied, the watermark will be altered to allow the consumer to know if it is a copy or not.

"To recreate this watermark, you will need a special code, a 128- or 256-byte key code," Aliaga says.

What's inside a 3-D printed object?

Christoph Hoffmann, professor of computer science, and visiting professor Ulas Yaman are using their algorithms to help strengthen the inside of 3-D printed pieces. The challenge is to come up with a design that offers strength but conserves the plastics that fuel most pieces on the Visualization lab's MakerBot Replicator 2X printer.

Hoffman and Yaman mostly use polylactic acid (PLA) plastic along with thinner T-Glas for clear pieces.

Hoffman and Yaman are working from hexagons that create the honeycomb-like interior structure of 3-D pieces. They are experimenting to see if there are better, more efficient ways to give 3-D printed materials their third dimension.

"By modifying the interior, we want to have different mechanical properties," says Yaman, who is visiting from Middle East Technical University in Ankara, Turkey.

The research is crucial as 3-D printing could bring about important items like car parts and surgical tools. The pieces must be strong, not flimsy. Hoffmann cites the U.S. Navy's use of 3-D printing technology for parts. Manufacturing on the ship will make for fewer trips to shore.

Hoffman is not surprised by the popularity of 3-D printing. In January, Hershey unveiled its own 3-D printing technology for "printing" chocolate.

Such sweet technological leaps will increase research in the College of Science.

"It's not so abstract. You can touch it," Hoffmann says.

This story originally appeared in the spring 2015 issue of the College of Science's Insights magazine. 

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