Introducing robo-ray
The tiny artificial stingray is the first step towards bigger, more complex tissueengineered robots, scientists say.
It’s a cybernetic organism: living tissue over a metal endoskeleton.
No, it’s not the T-800 from the 1991 film Terminator 2, but a robotic stingray made of rat heart cells stretched over a gold frame that can glide through water just like the real thing.
Sung-jin Park from Harvard University, and colleagues in the US and South Korea, unveiled their new method for building bio-inspired robots with engineered tissue in the journal Science.
Batoid fish, a family that includes stingrays, are ideal inspiration for robotics. As they manoeuvre through water, their wing-like fins ripple with a front-to-rear undulating motion.
This means they’re exceptionally energy-efficient swimmers and their flattened bodies stabilise them against rolling.
Inspired by batoids, Park and colleagues decided to reverse engineer a stingray’s muscle and skeletal structures – albeit on a smaller scale.
They started with a 3D body made of stretchy polymer, then overlaid it with a stiff gold skeleton and another stretchy polymer layer. Living cells from heart tissue, which contract naturally, were added last.
The cells were genetically engineered to contract when exposed to certain coloured light. They were printed onto the top of the robo-ray in a serpentine pattern, like squiggles, on the fin.
The end result was a “living robot” just 16 millimetres long and weighing 10 grams but housing 200,000 rat heart cells. Cells at the front of the robo-ray, when stimulated, contracted the fins down. When they relaxed, the gold skeleton popped them up again.
This movement stimulated the neighbouring cell to contract, and so on down the line.
When popped in a 37ºc salt solution – similar to a rat heart environment – with glucose for energy and a light to guide it, the tiny hybrid propelled itself through the liquid, albeit very slowly.
With an average speed of 1.5 millimetres per second, the robo-ray could be steered by adjusting the light’s brightness on either fin. More intense light causes the cells to twitch faster.
Park and colleagues found the robot could maintain 80% of its initial speed for six consecutive days.
Their prototypes, the researchers write, are a step towards “autonomous and adaptive creatures able to process multiple sensory inputs and produce complex behaviours”.