Biohybrid robotics: Self-trained bio-muscles power swimming robot
Bio-muscles for robots need to be strong. A research team had them train themselves to gain strength.
The training device (left) is used to train the cultured muscles. They are used in small swimming robots with two tail fins (right).
(Image: NUS)
Scientists at the National University of Singapore (NUS) have strengthened lab-grown muscle tissue through self-training on a simple mechanical training platform without any external stimulation, to the extent that the muscles could be used to power a small fish-like swimming robot. The OstraBot achieved what is likely the highest speed ever measured for a skeletal muscle-powered biohybrid robot.
Muscle-based actuators, i.e., those powered by living cells instead of motors, are soft, operate quietly, and are very energy-efficient at small scales. Furthermore, they are biodegradable and do not generate electronic waste. However, for larger robots, the use of bio-muscles is less suitable because they cannot generate enough force and are therefore currently of little use for practical applications.
The NUS research team has been looking for a way to increase the force of bio-muscles, as described in the study „Fast-swimming biohybrid OstraBot with self-trained high-strength muscles“, published in Nature Communications. To this end, they built a training platform for lab-grown muscles. It essentially consists of a movable block in a guide, to which two muscle rings are attached in opposition and can work against each other. When one muscle contracts, the other is stretched, and vice versa, so they train each other and become stronger over time.
Self-training muscles
The researchers are using a behavior observed in young skeletal muscle cells during their maturation. Spontaneous contractions occur from the third day onwards. These are used to allow the muscles to train themselves. External stimulation of the muscles is not necessary for this. On the fifth day, the contractions reach their peak and then subside until full maturation.
The muscles trained in this way achieved a maximum force of 7.05 millinewtons and a tension of 8.51 millinewtons, as can be seen from the study. According to the researchers, these values are the highest ever measured for this cell line in biohybrid robotics. They are said to be more than an order of magnitude higher than those reported in many other studies.
The researchers are using the trained muscles in a swimming robot named OstraBot. The robot uses the locomotion principle of a boxfish (Ostraciidae) with a rigid body, which propels itself solely through tail fin movements. The difference between OstraBot and its biological model is that in the robot, one muscle drives two tails. The muscle is electrically stimulated.
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At a stimulation frequency of 3 Hz, the OstraBot swam about three times faster than an identical robot with conventionally grown, untrained muscles. The OstraBot thus achieved a speed of 467 mm per minute, which, according to the scientists, is the highest speed ever measured for a skeletal muscle-powered biohybrid robot.
(olb)
