3D printing: bones, buildings and burgers

I first saw 3D printing at work in the movie Mission Impossible II starring Tom Cruise, which debuted 13 years ago. It seemed like at every turn, some spy was printing out a life-like 3D facial mask to impersonate his enemies.

Action flicks tend to preview near-future technologies, and 3D printing has gone from science fiction to an over-hyped but cutting edge research area since MI 2. The printers in question print 3D objects out of plastic or concrete instead of flat images on paper using ink. To show why the subject seems to have captured popular imagination, here is a short list of objects that may be printed in the near or distant future, according to recent articles:

• Replacement teeth, ears, skin, heart valves and fingers 
• Buildings (by teams of mobile printers)  
• Burgers and pizza on long space flights. 
• Robotic octopus suckers to help robots grip

Our guest for this podcast is Kenneth Sloan, Ph.D., professor in the Department of Computer and Information Sciences within the UAB College of Arts and Sciences, and director of UAB’s 3D Print lab. As described in an article by UAB Magazine's Matt Windsor, 3D printing may have applications in areas as diverse as medical implants, gaming, archeology and crime fighting. As Dr. Sloan says, there may soon be a 3D printer in every kitchen, and available in designer colors, but who knows what we will use them for.

Show notes for the podcast

1:25 Instead of ink, one kind of 3D print head pushes out extremely thin layers of superheated material that instantly cool to hold a desired form. Most of the 3D printers at UAB lay down layers of melted plastic 1/100th of an inch thick. They then move the print head up a bit and do it again, until the 2D layers stack up into a 3D object.

2:27  A second kind of 3D printing cures material in layers. You start with a box full of powder, and the printer lays down liquid in layers that hardens the power in the desired pattern. What you end up with is a box full of powder, with the desired object inside of it.  You open the box, grab the object and shack of the lose, uncured powder.  Interestingly, since concrete is hardened by combining liquid with powder, this has enabled researcher to 3D print objects in concrete.

3:30 An important challenge in 3D printing is that engineers must often design and print out a framework right alongside the target object so that the object doesn't collapse have way through being printed.

4:13 3D printing technology has been available for 20 years, but the computational power is just arriving now to make it useful and available to all. The advent of cloud computing meant that most researchers can now afford to program complex combinations of objects and supporting frameworks. Otherwise, 3D printers are made of standard tinkerer elements like small electric motors, sprayers and heating elements that have been around since the 1950s.  

4:38 What makes 3D printing require computing power are the calculations about where to lay down solid material in space as you build the object in layers, as well as the translation of spatial relationships from a 3D model to a series of 2D slices.

6:05 For many years, engineers have looked at 3D graphical displays on computer screens when designing prototypes. They work through a series of rapid design changes for an invention, testing and rethinking versions along the way. 3D printing allows engineer to print out the object at each stage in rapid prototype design. They can test fit it against other parts of whatever they are creating. They can roll it around in their hands. 3D printing allows for the fast manufacture of quick, cheap, multiple versions of a prototype invention in plastic to solve problems before fabricating it from an expensive metal for instance.

7:03 3D printing enables the creation of complex objects that no other process can create. There are several examples on Dr. Sloan's website that you cannot take apart, and that you could not assemble out of pieces in the first place. By printing interlocking pieces in layers, the final product is made of moving pieces that cannot be assembled or dis-assembled.  Picture a door that is one solid piece with it hinges. The door swings on the hinges, but you can't remove the hinges. Fun examples of this kind of object include puzzles. Dr. Sloan mentioned that one MIT student had even designed a 3D-printed a Rubik Cube, a single, interlocking movable puzzle as opposed to the original, made of separate pieces that snapped together.

9:24 Plastic and concrete were the first materials used in 3D printers because they are easy to melt or harden quickly into durable materials. Plastic melts easily and can be shot through a print head. Concrete starts as a powder and object can be shaped by selectively getting it wet. The interesting thing is that any substance that meets either of these criteria might eventually be 3D printed, from ceramics to metal to glass to chocolate.

11:08  Dr. Sloan's original area of expertise was in computer graphics.  The field had delivered tremendous value to engineers by developing the capability to display 3D digital images of desired objects on computer screens. That said, researchers had long wished that they could cheaply 3D print digital designs. With every decade, a "zero has been chopped off the price" of 3D printers, and now most labs can afford one.

12:13 Beyond assembling equipment, Dr. Sloan has reached across UAB to offer a 3D printing service of sorts to researchers in many disciplines. With a main mission of educating students in 3D printing, his lab might have been satisfied with using "hobby level" printers, or with sending out big jobs to specialty "print farms."  By hatching collaborations across campus, he has been able to centralize equipment costs and expertise to offer more advanced 3D printing to many research efforts that couldn't do it alone.  By making this offer, his lab has enjoyed a steady flow of inquiries from researchers proposing to use 3D printing in wasy he never could have imagined. Meanwhile, his student now have unparalleled access to real world design projects.

Lamina cribrosa

14: 26 An example of an interesting, unexpected project was the 3D printing lab's collaboration with the UAB Department of Ophthalmology. The lab was able to 3-D print a computer model designed by eye researchers of part of the optic nerve, the lamina cribrosa, known malfunction in the development of glaucoma. Apparently, our eyes our sealed, with a certain pressure maintained inside. This is complicated by the need for the optic nerve to pass through the outer membrane of the eye as it carries information about images from the lens into the brain for processing. Making this possible is the lamina cribosa, a web-like mesh through which the optic nerve fibers can pass out of the eye without losing pressure. This feature of the anatomy is about two millimeters across, but Dr. Sloan's team was able to 3D print an eight-inch version. This enabled the research team to pick it up, look through it and roll it around in their hands for the first time. Since then, Dr. Sloan has watched as a series of eye researchers, including his wife, UAB anatomist, Christine Curcio, Ph.D., have picked up the model, spun it around and said,"...interesting, I never realized that XX."

16:59 Dr. Sloan also highlighted the ability of 3D printing to be useful to bioengineers seeking to design scaffolds. The body has an amazing ability to regrow skin, bone or muscle lost to injury or disease, but it often needs help. His lab is involved in current UAB research projects seeking to design of mats or scaffolds or weaves of material that act as a guide and support for tissue trying to grow back together in an orderly fashion. 3D printing may be especially useful in creating scaffolds out of biodegradable materials. That would enable surgeons to implant a scaffold that aids in tissue regeneration without requiring a second surgery to remove the scaffold later. It would simply dissolve about the time it was no longer needed. Dr. Sloan's lab has one printer that prints in a biodegradable, nontoxic material, and there has been a steady stream of researchers from the medical end seeking to build it into research projects.

18:32 3D printing will be valuable to regenerative medicine for the same reason it is useful in rapid prototyping. It lends itself to creating a single custom implant for each patient, versus technologies that require mass production of one-size-fit -all implants to break even.

19:32 Dr. Sloan believes that it will be possible in the next five years for biotechnicians to 3D print skin to cover wounds and burns, knee cartilage and heart valves. These are examples of the more straightforward, uniform tissue types that lend themselves to current 3D printing technologies. Unfortunately, he said there is also a great deal of hype surrounding 3D printing right now, and stories that predict the imminent arrival of printed, complex organs with intricate cellular structure are not realistic. These structures would require technologies that 3D print with a nanoscale resolution, and are still a long way off.

21:50 Beyond medicine, a recent article in Discover Magazine talked about how 3D printers may one day print out meals for future astronauts on long spaceflights. Dr. Sloan said burgers and pizza would be on the 3D printing menu, but not steak. The reason for this are the same ones that determine the field's ability to print out skin but not a brain. Burgers and pizza be printed out of somewhat homogeneous, simple materials that hold their form in layers as they are printed and then cooked. A pizza printer might have five printer cartridges that spew layered shapes that bake into a pizza. Steak is tissue, with a complex microstructure beyond the reach of current technologies.

24:40  Dr. Sloan this week attended the Inside 3D Printing Conference in Chicago, which included an exhibit of 30-foot high concrete sculptures made using 3D printers. He is currently seeking collaborations with artists and sculptors who wish to 3D print fantastical forms by curing concrete out of powder. Layer-by-layer printing may make possible the creation of interlocking, complex sculptures that would fall apart in mid-assembly if made any other way.

26:06 Moving from art to architecture, Dr. Sloan said he has seen reports of researchers experimenting with the idea of 3D-printed buildings. If one can print a 30 ft by 30 ft sculpture, it may be possible to print a 300 ft by 300 ft building. Furthermore, builders may one day dispatch a team of mobile robots with built-in 3D printers to assemble different parts of a building at the same time. The same idea goes for shooting robots to the moon that could mine local materials and and then 3-D print a moon base before the people even arrive. An advantage of large-scale 3D printing would be that you no longer have to build a structure out of pieces (nails, beams, etc.). That leaves the architect free to design any structure that will stand once complete.

28:23 Dr. Sloan hesitated to predict how we might use 3D printers in the future. He said he is old enough to remember when personal computers were just a pipe dream. As their advent approached, articles mistakenly predicted that we would use them to store our recipe files and to tell us what to make for dinner based on what was in the fridge. "Who knows how we will use 3D printers around the house?" If it gets cheap and useful enough, people will invent their uses for it.

Here are a few more, recent 3D printing articles from around the web:

New Scientist: Windows aims to open 3D printing to the masses

CNBC: How 3D printers are reshaping medicine

Time: Chicago 3D print shop open for business

Human body as skin-growing factory?

It happens quickly, say surgeons. You step off a curb or light a backyard grill, and your life is changed forever by profound injury. Patients arrive at major trauma centers every day with burns covering most of their bodies, or with a combination of skin, bone and muscle lost to terrible circumstance. Trauma surgeons do what they can to put things back together but are limited by today's tools.

In recent decades, surgeons have partnered with bioengineers to try to create better technologies for the replacement of lost tissue. They still have a ways to go, but surgeons may one day take a product "out of a box" and use it to patch large gaps of missing tissue.

Along these lines, research efforts captured in a recent Wired Article seek to create truly artificial replacement skin out of self-healing polymers and flexible electronics. Another near-future approach will be to use a patient's own body as a high-speed skin-producing factory with the help of appliances, engineered proteins and biochemicals.

We asked Steven Thomas, M.D., a UAB specialist in reconstructive surgery for patients with complex wounds and severe burns, for his take on both approaches. As an assistant professor in the Department of Surgery within the UAB School of Medicine and a former army surgeon, Dr. Thomas has spent much of his career looking for a better way to repair damaged tissue, layer by layer.


Show notes for the podcast:

00:56 UAB has the biggest burn and trauma centers in Alabama and Mississippi, and Dr. Thomas' team deals regularly with patients that have lost large amounts of skin, muscle and bone.

2:21 Burns pose a particular challenge when it comes to repairing skin, especially when all layers of skin (dermis, epidermis, etc.) have been destroyed. This requires surgeons to borrow skin from the non-burned areas. They can then use bioengineering techniques to regrow skin, but currently technologies do so slowly. When burns cover the majority of the patient's body, it is a challenge to regrow enough skin fast enough to avoid scarring.

3:22  According to Dr. Thomas, there is no current treatment option that efficiently and quickly makes available large amounts of replacement skin. Those that are available cost hundreds of thousands of dollars, require multiple procedures and don't work for all patients.

3:45 One product on the market now called the cultured epidermal autograph is grown from a patient's own skin cells by the biotech company Genzyme. From 2 postage stamp-sized biopsies, the company says it can  grow enough skin to cover a patient’s entire body, but it may cost $600,000, said Dr. Thomas. What the field needs is inexpensive replacement skin that you could take off a shelf and apply.

5:10  Many current research efforts seek to create good artificial skin, but no one product has gelled yet. Today's attempts are not durable enough, he said, and need to be replaced by something that can be shipped and stored without losing its useful properties.

6:48 Some of the frontiers in artificial skin research include polymers that can knit themselves the way real skin does, but nothing to date does the job as well as the body itself  The problem is large gaps in skin, which scar instead of knit.

7:58 Dr. Thomas is convinced that the future of the field will be in using the patient's own body as a high-speed bioreactor to make replacement skin, but it needs help. A current UAB research project led by graduate student Paul Bonvallet in the lab of Susan Bellis, Ph.D. seeks to provide that help using the protein collagen taken from cows. Collagen is the ingredient that gives shape, strength and structure to the body's connective tissues like bone and tendon, as well as to skin.

8:15 The UAB project is having some success in laying a mat of collagen across large areas where a patient has lost all layers of skin. The mat serves as a framework or scaffold that enables the skin to re-knit in an orderly way over of the dermis. The experimental product contains no cells, but the body populates it as needed.

8:42 UAB is among the first in the country to combine dermis scaffold and skin grafts to get patients re-covered with skin after major injuries. Dr. Thomas mentioned one accident victim that was hit and dragged underneath a garbage truck, loosing much of his skin, along with some bone and muscle, from the waist down. Through a combination of therapies, the surgeons were able to re-grow the lost skin, and the man is up and walking today. Dr. Thomas believes that in most places that man would have lost his legs.

9:21 Underway already at UAB are efforts to combine scaffolds with different mixes of stem cells and enzymes that encourage growth. The combination of framework and tailored cells is getting closer and closer to mimicking native tissue, itself a mix of cells and scaffolds.

10:09 Depending on the type of collagen used, it can act as the highway with guide rails that shows skin cells the pattern they need to grow in to cover over a wound or burn. Some types of collagen are better at doing this without leaving a scar. Dr. Thomas' team has been able to get good-sized wounds to heal in a few weeks using collagen biotechnology that used to take months.

11:57 Returning to the effort to generate truly artificial skin mentioned in the Wired article, Dr, Thomas said that the military has invested in such technologies in hopes of better regenerating skin for wounded soldiers. Institutions like DARPA, the Defense Advanced Research Projects Agency, and AFIRM, the Armed Forces Institute of Regenerative Medicine, fund related research projects.

12:15 Dr. Thomas thinks that, while the body may be best at creating skin for burns and wounds, artificial skin made from polymers has the potential to dramatically improve the nature of artificial limbs. During his years at the Brooke Army Medical Center burn unit, Dr. Thomas saw lots of amputees come in, and worked with many soldiers trying to get used to prosthetic limbs. He said today's prosthetic arms have no proprioception, the sense of where the limb is in space and with respect to the rest of the body. They also have no sense of touch. Creating limbs with these capabilities would represent a huge leap for people with prosthetics, he said.

14:00 Dr. Thomas has worked with the Bellis lab experimenting with electrospinning, a process that uses electrical charge to draw a nano-scale thread of material from a liquid. It is particularly suited for the production of fibers out of large and complex molecules like collagen.  Electrospun collage can be woven into mats that promote cell growth and the penetration of cells into the engineered scaffold.  The other great thing about electrospun materials is that they are inexpensive.

15:59 To fill in a complex wound, Dr. Thomas would like to have a treatment that could regrow skin, muscle and bone in layers. Stem cells engineered in concert and in layers to achieve such complex healing is a future possibility, he said. It may be too much to ask one product to achieve all that, and may require a combination of stem cell-driven products used together with precise timing.