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Human-robot hybrids are advancing quickly, but the applications aren't just for complete synthetic humans. There's a lot we can learn about ourselves in the process.

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[♪ INTRO].

As robotics has become more advanced, we’re starting to see more robots that look and move just like humans. But there’s still some room for improvement, like to robotic faces.

It’s a complicated thing, the face. We’re still working on getting out of that Uncanny Valley, there. And one way we might close that gap is to replace clunky robotic parts with human ones.

While this might sound like Bicentennial Man, human-robot hybrids or bio-hybrid robotics isn’t a sci-fi dream, it’s a real field that already exists. And it’s not just a way to make more life-like robots. By mimicking our bodies better, bio-hybrid robots might help scientists learn more about how we move, why we’re built the way we are, and how to fix all these moving parts when something goes wrong.

Just like a human body, a robot generally needs a skeleton, and ways to move that skeleton. These include motors and actuators, which can deliver rotational or linear forces to the joints of the skeleton. In bio-hybrid robots, that movement comes from live muscle tissue.

Of course, scientists aren’t just taking entire muscles from humans and throwing them on a robot. At least if they are, they’re not telling us. You don’t know what they’re doing in that weird volcano lair.

But, the legitimate scientists, they grow their own muscles. This happens in a lab by culturing myoblasts, embryonic cells with the unique ability to differentiate into different muscle cells in a process called myogenesis. To make muscles grow how they want, the scientists create a scaffold in the form of a hydrogel, a special water-based gel that’s great at absorbing and retaining cells.

Inside the hydrogel, the cells form into muscle fibers, long strands of muscle cells that all pull together in the same direction. By altering the shape of the hydrogel, the alignment of the muscle fibers can be tweaked and adjusted, giving scientists control over the direction they pull in. And once these fibers are formed, a tiny electric shock is all it takes to make them contract.

They are then ready to be connected to the joints of a robotic skeleton, and voila! A bio-hybrid robot is born, or built, I guess. We don’t have whole human replicates running around, though.

Not yet, anyway. Scientists at the University of Tokyo just managed to get small muscle pairs working in early 2018. That’s because there are a number of limitations that need to be overcome before bio-hybrid robots really take off.

These lab-grown muscles don’t have any way to repair themselves, so they only last a few days to a week. In your body, muscles receive spare parts via your blood. But bio-hybrid robots don’t have that fluid exchange system, so once the tissue wears down, that’s it.

And this breakdown is accelerated by the friction generated when the muscles move. So, your muscles are surrounded by epimysia and fascia, connective tissues which separate individual muscles and help them glide smoothly past each other. So to last longer, bio-hybrid robots need some kind of biocompatible lubricant to reduce friction, like bio-WD40.

Also, the electrical stimulation part could use some work. While it does get the job done, it’s difficult to control precisely how strongly the muscle contracts, especially for sustained contractions. So fine motor movements aren’t really possible yet.

The electricity also contributes to wear and tear. The muscles have to stay wet, so using electricity inevitably causes some of that water to separate into hydrogen and oxygen gas, a process called electrolysis. These gas bubbles, in turn, further damage the muscles.

One possible way to get around that is to grow motor neurons in the muscle tissue and let them command the muscles instead. Which seems a little too close to a Westworld host for my comfort. But there are some good reasons to continue perfecting these bio-hybrid robots, even if they seem pretty creepy.

One big advantage of using real muscles is that they are flexible. And the idea of using soft, flexible moving parts is the driving force behind the field of Soft Robotics. These robots use things like cables and inflatable bladders to move instead of metallic motors.

And their flexibility allows them to adapt better to new tasks. Bio-hybrid robots could lead to better soft robots, including ones that would be safe to use on or even in our bodies, since they won’t have as many sharp bits or cell-harming chemicals in them. But what’s really exciting to scientists is that bio-hybrid robots can move like us.

That means they can help us understand why we move the way we do, how our brains control our bodies, and how to fix things if they go wrong. The human body is an incredibly complex machine. Hundreds of muscles are responsible for moving the joints in our limbs that allow us to work and play and do things like click that button below to subscribe to SciShow.

Yep. Several muscles can be responsible for a single movement, and a single muscle can contribute to several different movements. And that means if someone develops a motor impairment, it can be difficult to understand exactly what’s going on.

For example, people recovering from a stroke sometimes experience hemiparesis, or weakness on one side of the body. Others may have muscle synergies, where activating one set of muscles results in the involuntary activation of another. Both conditions may be a result of missing or mixed communication from the brain, changes to the muscles themselves, or some combination of the two.

Having a bio-hybrid robot that mimics a human arm might help scientists better understand how these conditions arise and, more importantly, how therapists can best work with patients to help them recover. Basically, we have to build ourselves from scratch to fully understand these marvelous bodies. Which I’m fine with, so long as we stop short of that full-on Westworld scenario, where I’m not sure whether Caitlin’s real or not.

Also I wouldn’t mind if we made some progress on those faces. It’s not good. Thanks for watching this episode of SciShow!

If you want to continue learning about how humans work, stick around by clicking on that subscribe button, using all your muscles! And if you want to learn more about how your muscles work and how to make them, you can check out our episode on proteins. [♪ OUTRO].