This paper, very recently published by Park et al in Science, dives into the realm of the futuristic as it outlines the development of a biohybrid robotic ray… yes that’s right, a swimming, controllable robot fish made from real muscle cells, and that can be guided by light signals to overcome an obstacle course. But how did this team go about creating this bio-inspired batoid, and what could this technology potentially achieve for us?
Ray-bots- how are they made and how do they work?
These biohybrid rays are 1/10th the size of a normal ray, and weigh ~10mg. The scientists involved in this project used a ‘skeleton’ made from gold, which stored elastic energy produced by the movement of the fins. It also has a ‘body’ made from polydimethylsiloxane, and muscles from genetically engineered rat cardiomyocytes (heart muscles).
Genetically engineered rat heart cells?
These cardiomyocytes were genetically altered to contract when stimulated with a specific wavelength of light. They were engineered to contain a light-sensitive ion channel called channelrhodopsin-2. Muscle contraction down the AP axis is triggered by the creation and propagation of an action potential, which is facilitated by the activation of channelrhodopsin-2. This recreates the undulatory motion of batoid fish (e.g. rays and skates).
Each ‘ray’ contained ~200,000 cardiomyocytes, arranged in a zig-zag pattern down each fin. When stimulated with a light source, the contraction of these cells create batoid-like undulatory motions, causing the fish to swim. These cardiomyocytes had a high sensitivity to blue light at ~10mW power. The really clever part was that each fin contained cells that were optimally sensitized to different wavelengths of light, meaning they could be independently controlled. Therefore, it was possible to use different light intensities to control the fin undulations, and make the ray turn corners. The ability to steer the ray phototactically allowed the scientists to guide it through a miniature obstacle course, with an average speed of 1.5mm.s-1, and across a distance of 250mm.
Why is this important?
Not only is the development of biohybrid rays groundbreaking, they also may prove to have some important medical and research functions. This ability to integrate living cells and non-living structures could mean a step forward in researching and creating pre-designed neurological and mechanical systems. This small biohybrid ray could be the first of many ‘soft robotic’ inventions that increase our understanding of muscles, movement, and nervous systems of animals.
Medically, the authors of this paper, and several other review papers, highlight that the ability to manipulate cardiomyocytes in such a way could lead help develop real-life hearts that can be controlled in different ways.
Isn’t this inspi-ray-tional?
The Paper- Phototactic guidance of a tissue-engineered soft-robotic ray
- Park et al 2016- Science 353 (6295), 158-162
Words in pink can be found in the glossary
Image from Science magazine, photo by Ken Richardson