Credit: University of Illinois at Urbana-Campaign

Robots can be very strong, fast and enduring. However, unlike in animals, none of this strength comes from muscle, instead robots mainly rely on electrical motors and other hard and generally inflexible parts. But with all the advantages that conventional robot hardware can deliver, it still does not match the ability of muscle-powered animals to provide an accurate response to different physical environments. To address this downside of robotics, a group of researchers, led by Professor Rashid Bashir, at the University of Illinois at Urbana-Campaign developed tiny walking bio-robots powered by engineered muscle tissue.

The robot consists of a 6 mm long flexible 3D-printed backbone with two strains of muscle attached to each of its ends. The backbone has two little feet and is used both for walking and sustaining the structure. The important thing about the robot is that the muscle tissue used in it is the skeletal muscle, the one humans use to move around, which means that it can be easily turned on by administering electric impulses. Furthermore, by adjusting the frequency of the impulses, the robots’ speed can be modified.

The use of skeletal muscle allows for a better control over the robots’ movements. This significantly differs from the previous study conducted by the same group, where the researchers used heart tissue, which contracts non-stop and with a constant rate.

This technology is an important step on the way to integrating biological tissue in machines, which in some cases can be priceless. For example, muscle-powered robots are perfect for medical applications inside the body: the tissue is a perfect biodegradable material and such robots could run in a nutrient rich fluid without any additional power source. In addition, the use of muscle-powered limbs in biomimetic machine design would open hundreds of new possibilities, especially in the field of soft robotics. Imagine how much more lifelike a robotic starfish or octopus could be if powered by muscle tissue!

With the concept of a muscle-powered robot tested, the researchers are now preparing for the next step: the group envisions equipping their robots with light or chemically sensitive neurons for controlling direction of robot’s movement as well as testing new designs of the backbone to enable a wider range of motions.

The results of the study can found in PNAS in the article called “Three-dimensionally printed biological machines powered by skeletal muscle.”

Developers of these types of robots are applying the concept of simplexity; while these robots are capable of more complex behaviour, on some levels their architecture is quite simple. The robot pictured above has no sensors, a mere 5 actuators , and it operates using pressurized air.

These kinds of simple designs call for inspiration from ¨simple¨ creatures. Consistent with the name of the European project, OCTOPUS, focuses on the incredible motor capabilities of the eight armed animal. Meanwhile, scientists at the Soft Robotics Lab at Tufts University  have focused the majority of their studies on the Maduca sexta caterpillar.  Their GoQBot mimics more than the caterpillar’s crawl- it’s able to simulate a fascinating attack response termed a ¨ballistic roll¨. You may have to see it to believe it in the video below.

There are  however, some hard issues to face when making soft robots; soft materials are much more difficult to control. When a given amount of force is applied on a hard object, for example a metal rod, scientists can easily predict how the rod will move and this movement can also be easily reproduced. However, when a given force is applied to a soft object like a rubber band, its motion is much more difficult to predict because there is much more variability in the way that the force affects it.

In any case, researchers around the world are up to the challenge. Robot Companions for Citizens is a European initiative that aims to incorporate soft-material robotics in the development of sentient machines. These robots will be cognizant and aware of their physical and social world which will allow them to assist us among the chaotic variety of our everyday lives. Click HERE for more information on that initiative.