Fish built with plastic and heart cells swims for three months

A world of biological robots is just a heartbeat away. Artificial muscles based on human heart cells have just powered a swimming ‘fish’ for more than three months.

In a study published by the journal Science, Harvard University bioengineers put a film of human cardiac muscles on either side of a robotic fish skeleton’s tail. The “fish” itself was made from paper and plastic coated in gelatin. 

Fed by nutrients in its pond, the bio-fish maintained its motion for 108 days. That is 38 million beats of the tail.

“Rather than using heart imaging as a blueprint, we are identifying the key biophysical principles that make the heart work,” says Kit Parker of Harvard’s Wyss Institute. “[We are] using them as design criteria, and replicating them in a system – a living, swimming fish, where it is much easier to see if we are successful.”

The idea is to reverse-engineer the human heart’s ability to beat over a billion times during its lifetime while “rebuilding its cells on the fly”.

“The really interesting thing about these fish, which we weren’t expecting, is how long they would swim and how fast they would swim in the dish,” Parker says.

As the muscles matured over the first month, they reportedly became ‘fitter’ – improving the biorobot’s swimming performance. The researchers say it eventually reached speeds similar to that of a zebrafish.

The biorobot reportedly regrew its heart muscles about five times over the 108 days.

The centre of the experiment was a cluster of cells that synchronised the alternating contraction of the muscle cells, causing the fin to produce a sustained swimming motion.

These cells are behind human heart diseases such as arrhythmia.

Early experiments artificially stimulated the cardiac cells. Then, the ‘fish’ were put in an incubator and “forgotten” for several weeks. When the team returned, “all the fish were swimming by themselves,” Parker told NPR.

But bio-hybrid robotics is not the primary purpose of the research.

Instead, the research team hopes to find ways to produce advanced pacemakers – and eventually bio-artificial hearts – for humans.

The Harvard researchers say the next challenge is how to keep bigger muscles, and therefore more powerful artificial hearts (and bio-robots), alive. That may involve reverse-engineering mammalian vascular and blood vessel systems and digestive systems.

The Harvard biophysics group in 2012 used rat heart cells to build a bio-robotic pump. In 2016 they turned rat heart cells into a swimming, bio-robotic stingray.

“Our ultimate goal is to build an artificial heart to replace a malformed heart,” says Parker.