Synthesizing and 3D bioprinting tissues has become an increasingly popular topic in medical science, particularly in the search for an alternative to heart transplants and biocompatible polymers. We recently published a blog post on the ghost heart and its promising applications, but scientists continue searching for other methods of heart synthesis. While researching how today’s academia is approaching biocompatibility, two research projects stood out – one conducted at Harvard University and another at Case Western Reserve University - have successfully created “living” robots, or biohybrids. While these robots meet the requirements to be considered living organisms, these robots are not capable of thought or any of the parameters that classify an organism as living – i.e. they are not autonomous. Rather, these organisms are made of animal muscular tissues and synthesized polymers.
As an exercise in heart tissue engineering, Harvard’s team, led by Kevin Kit Parker, has synthesized a tiny, robotic stingray comprised of a 3D printed gold cartilaginous skeleton, elastic polymers, and cardiomyocytes (heart cells extracted from a rat). The thin, carefully engineered layers of rat heart muscle cells have been genetically engineered to make them reactive to light. The amazing part is what this ray’s cells can do. Light cues cause the robot’s musculature to undulate like an actual stingray, allowing researchers to control its movements!
Optogenetics, or the genetic engineering of cells so they become light sensitive, is the recently pioneered science that has allowed for this breakthrough. The synthesis of an organic robot allowed for more natural movement than would have been possible with a traditional motor-and-wires robot. As it says on the Harvard biohybrid materials website, “The ability to synthetically produce contractile bio-hybrid structures has created new opportunities to mimic natural configurations and properties.” Moreover, 3D printed gold frame overlaid with elastic polymers provides recoil that returns the ray’s sturdy yet flexible frame to a resting position between each flash of light. Again providing greater maneuverability than traditional robotics. Parker hopes to eventually utilize the advancements from their experiment to engineer a working, biomechanical human heart.
Case Western’s team fabricated a biohybrid crawlers that search the underwater locations for wreckage and toxic leaks. The extensive team of scientists, including PhD student Victoria Webster, Dr. Roger Quinn, Dr. Hillel Chiel, and Dr. Ozan Akkus, utilized buccal (cheek) cells from a California sea slug for motor purposes and a 3D printed polymer body. The mobility that sea slugs demonstrate in both calm and strong currents along the ocean floor inspired the team to create a robot that could have similar locomotion potential. Moreover, sea slugs are extremely hardy animals. Capable of adapting to environments of varying salinity and temperatures, their cells’ proficiency at surviving made them perfect candidates for the underwater crawlers. In the initial testing, Webster and Quinn’s team discovered that the locomotion muscles they experimented with didn’t work as well as the buccal cells. The picture below illustrates the “Y” shaped crawler.
The easily visible muscle beneath the translucent polymer body contracts and releases (with electrical impulses), causing the biohybrid to be propelled forward. “We’re creating a robot that can manage different tasks than an animal or a purely man-made robot could,” Quinn said to Case University’s blog. Here’s where these robotic crawlers get even more science fiction: they have their own ganglia. In other words, they have small, nerve center that controls what they do i.e. a primitive brain. With this ganglia, the muscles are capable of more complex movements and potentially will be able to learn. It’s possible that any sci-fi fans reading this are getting flashes of cylon invasions or the rise of Skynet, but this is highly unlikely.
The team intends to train this ganglia nerve center to respond to signals to move forward and backward. “We want the robots to be compliant, to interact with the environment,” Webster said. With continued experimentation and progress with the crawlers, Webster hopes to 3D print the gel-like collagen of the California sea slug in order to make a lightweight, flexible and strong scaffold for the crawler that would be completely biodegradable. With these advances, the crawlers could be sent out into the ocean with no need for recovery; the expendable crawlers could simply be eaten by local fauna or degrade naturally.