This past week saw an intriguing confluence of multiple disciplines, in the form a new artificial stingray model its creators call a “living robot,” and an unconventional means of studying the human heart. Driven by rat cells and modeled after a fish, it might seem like (and be) an odd way of looking into human anatomy, but it could help improve our heart health as well. Plus: robot stingray!
This robot, a continuation of a line of research that began with a robot jellyfish, is less than half an inch long and weighs only about 10 grams. The unusual creation is made of lightweight gel in the iconic shape of a stingray, which has been the subject of scrutiny for its remarkable efficiency in moving through water. The outer layer which forms the overall body shape is made of the same form of silicone used to coat breast implants, while the interior skeleton is made of gold. This skeleton provides the much-needed tension that springs that fins back into place after they flex.
Flex? Yes, the undulating motion of a stingray is replicated in this case with contracting rat heart cells, which are places along the skeleton so they can be stimulated to produce the desired movement. Stimulating these cells at will requires a technique called optogenics, in which cells are genetically engineered so they contain light-sensitive versions of specific proteins; let the cells develop so those proteins are worked into its entire structure, and you’ve got a light-sensitive cell. The researchers co-opted an algae protein for their purposes.
The gold skeleton is actually covered in a super-thin layer of silicone that’s etched with the details necessary to promote the structure of fully, properly developed muscles. Without that, they might all respond to the light impulse, but they’ll all contract in a different direction — no good can come of that. With this guidance, however, they work to contract the skeleton is a very specific way, allowing the researchers to direct the ray-bot with a beam of light — in practice, it appears to be “chasing” the spotlight.
The researchers placed different versions of the cell at different points in the stingray, each sensitive to a different wavelength of light. By controlling the robot’s exposure to different forms of light, the researchers could “drive” and “steer” the creature at will. This isn’t a particularly groundbreaking achievement in optogenics specifically, but an ingenious application of it. By applying new understanding of just how rays move through water, they were able to create quite an efficient little robot.
The hope is that building these sorts of projects, and learning how to better manipulate and develop heart cells to achieve certain aims, we’ll gain a better understanding of how heart cells work, and how whole hearts pump fluid throughout the body.
But is this a “living robot,” or, as the researchers said in one interview, a biological life form? It seems like a bit of a stretch. After all, the shape of the silicon we put around the heart cells shouldn’t matter much to the definition of life — how is this more a biological life form than those same heart cells just sitting in a pile in a dish? It’s alive, because those cells are alive, but unless that lump of cells is a biological life form, the stingray probably isn’t, either. Its abilities aren’t sufficient to let it respond to threats or pressures, and it can’t reproduce.
In other words, it’s just a bunch of genetically engineered and artificially grown animal cells attached to a golden skeleton inside a breast implant shaped like the animal that killed the Crocodile Hunter. For now, that seems like it ought to be enough.