Replacements versus Substitutes
The major goal of 3D bioprinting is to make replacement human organs. Replacements seek to replicate Mother Nature’s design. But before someone successfully bioprints a replacement human heart or liver, someone else may print something better: a biomechanical organ substitute that seeks to improve on Mother Nature’s design. Combining 3D printing and bioprinting will yield bio-mechanical organs more suited to the human lifestyle and increasing longevity.
"We are only at the very primitive start of the merger of 3D printing and 3D bioprinting"
One of the most exciting things about 3D printing is design freedom, which is resulting in parts that look more like they were grown than built, such as Arup’s structural node shown below. The part on the left was made with traditional manufacturing methods. The two parts to the right were topologically optimized and 3D printed. They look more like Mother Nature designed and made them, rather than humans.
Another example is Airbus’s Light Rider motorcycle, which has an organic, topologically optimized frame reminiscent of a bird’s skeleton.
As designers learn to design for 3D printing, more biomimetic designs will emerge that take full advantage of the design and material efficiencies that biomimicry offers. Combining 3D printing and bioprinting will transform the product-design paradigm from inorganic structures to truly organic ones, merging the human-made world with the natural world.
Substitute organs will be one major application of biomechanical printing. But biomemetic printing will have healthcare applications both inside and outside the body, such as infant cranial helmets, which grow with the child. Another application is MIT’s Professor Neri Oxman’s 3D printed, living wearable called Mushtari.
Inspired by the human gastrointestinal tract, Mushtari contains 3D printed internal channels designed to host synthetic microorganisms that fluoresce in bright colors and photosynthesize biofuels. Professor Oxman envisions the living wearables fueling our bodies and repairing damaged skin. According to Oxman: The incorporation of synthetic biology in 3D printed products for wearable microbiomes will enable the transition from designs that are inspired by Nature, to designs made with and by Nature, to, possibly designing Nature herself.
Mushtari is currently 3D printed in plastic. Eventually, it will be a biomechanically printed, living extension of the body.
In my book, 3D Printing Will Rock the World, I discuss the growing use of biomimicry in product design and in 3D printing and 3D bioprinting, not only for medical devices, but also for parts and products outside of healthcare. A step in this direction is USC Viterbi School of Engineering’s efforts to develop 3D printed body armor that mimics a lobster shell, using inorganic materials (carbon nanotubes) fabricated in rotating anisotropic layers. The next step will be to use organic materials to biomechanically print body armor that is essentially a living, self-healing shell that mimics Mother Nature’s armor designs.
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To make such parts and products, bioprinters (which are essentially material extrusion or micro-dispensing machines) and one or more of the other six basic types of 3D printing technology recognized by the International ASTM will merge, resulting in biomimicry printers or fabricators that use inorganic, organic, and digital materials to make biomechanical parts and products for the human body and for products that have no relation to healthcare.
Materials are the Key
Biomechanical printing will require new materials. A step in this direction is MIT’s bacteria-based bio-inks for biomechanically printing living wearable technology. The bacteria were engineered to emit green fluorescent proteins when activated by a signal chemical. Using a micro-dispensing process and two different bacteria-based bio-ink hydrogels, several living 3D structures—specifically, a square, pyramid, dome, and hollow pyramidal structure—were bio-printed in a physically cross-linking matrix, then chemically cross-linked by exposing them to UV light. When the pyramidal structure was exposed to a particular signaling chemical, the top and base turned a green, while the sides remained red.
The MIT team also used living, bacteria-based bio-inks to print living tattoos in a tree-like pattern on a thin flexible substrate, which was then stuck to a human test subject’s skin. Three branches were 3D printed with different strains of the live bacteria, which react to different signaling chemicals. Over several hours, branches of the patch’s tree lit up when bacteria sensed their corresponding chemical stimuli on the skin.
These proof-of-concept experiments show the promise of biomechanical structures.
We are only at the very primitive start of the merger of 3D printing and 3D bioprinting. When you compare traditional product and parts designs to current examples of topologically optimized designs, you catch a glimpse of what is possible, not just in the long term (in which maybe everything is possible), but even in the near future (say, 10 years). Combine topological and structural optimization, 3D printing, 3D bioprinting, organic, inorganic, and digital materials, and you have a recipe for helping humans not to advance beyond nature, but to design and build like Mother Nature herself.