The term cyborg conjures up images from Star Trek, RoboCop, and even The Six Million Dollar Man, and while we might get there someday, our first attempts at creating biohybrids are a lot simpler, but no less impressive, as demonstrated by this robotic fish powered by human heart cells.
Calling this fish a robot might be a generous description of its capabilities, but like the robot arms in a factory designed to repetitively replicate the movements of a human arm, it’s able to swim through the water like a real fish can, but without any intelligence guiding its path. That wasn’t why the tiny fish automaton was created, however. Instead, researchers at Harvard and Emory University are using it as the groundwork towards growing organic artificial hearts one day.
The fish’s design features a flexible tail that’s covered in a layer of heart muscle cells (cardiomyocytes derived from stem cells) on each side. When the cells on one side contract, it pulls the tail in that direction, and when the cells on the other side contract, it pulls the tail in the opposite direction. But what’s particularly interesting about this biohybrid is that the two layers of muscle cells are continuously triggering each other. When one side contracts, it causes the other side to stretch, and the stretching action opens a “mechanosensitive protein channel” that causes that side to contract, which in turn stretches the other side, and the process repeats.
The robo-human-fish also features a simple pacemaker-like mechanism that autonomously regulates the frequency and rhythm of these contractions so the tail has a proper back-and-forth motion to propel it through the water. Without any additional inputs, the muscle cells functioned as a closed-loop system and were able to propel the fish for over 100 days. Furthermore, like the muscles in your body improving with exercise, the biohybrid fish got better and better at swimming as time went on, until it was able to move through the water at speeds similar to a zebrafish.
The prospect of an aquarium full of artificial fish you rarely have to feed is a tempting one for those who are notoriously irresponsible at taking care of pets, but the researchers have loftier goals. Successfully recreating the biophysics of the heart’s function, and the self-sustaining mechanisms that make it endlessly beat, is a huge step towards one day being able to create artificial hearts from the same organic ingredients our bodies use.