Soft robots are nothing new, but they're generally made with a mix of circuitry and silicone or other rubber-like materials. Researchers from a variety of universities have just announced in the journal Science that they took a different approach. To create their robotic ray, they engineered some pretty special heart cells and attached them to a golden skeleton.

Inspired by the relatively simple shape and swimming methods of batoid fish like stingrays and skates, the group, lead by Sung-Jin Park of the University of Illinois who specializes in microelectronics and photonics, first built a framework for the robotic fish from gold. The golden skeleton was about 1/10 the size of a normal skate and it was designed in such a way that it could store energy when it was flexed upward.

Meanwhile, some members of the team were busy bioengineering rat heart cells known as cardiomyocytes to make them sensitive to light.

The robotic ray, which measures 16 mm (about .6 in) long and weighs just 10 grams (about .4 oz) is on the left, while a real skate is on the right(Credit: Karaghen Hudson)

The heart cells – about 200,000 of them, to be exact – were then placed atop the gold framework. When they were stimulated by light, they contracted, causing the artificial skeleton to bend in a downward motion. Then, once the heart cells relaxed, the framework could flex downward using the energy it had stored. This created a swimming motion that could propel the half-muscle, half-machine creation through water.

By altering the position of the light pulses, the robotic ray could be steered left or right, and by adjusting the light's frequency, the speed of the tiny robot could be controlled. The researchers had so much success in steering the robot that they were able to maneuver it through a basic obstacle course.

You can watch the little hybrid critter in action in the following video.

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