Robotic control of live jellyfish
Keywords: Bioengineering.

The present study establishes the robotic control of jellyfish swimming by incorporating a self-contained microelectronic system embedded into live jellyfish. Prior work to develop bioinspired robots include designs using entirely engineered materials, and biohybrid designs that incorporate biological components. Two approaches to biohybrid robotics are to seed biological tissues onto artificial scaffolds and to use live organisms, which leverage the animal body as a natural scaffold with existing actuators that can tolerate damage because of tissue regenerative properties. Although biohybrid approaches incorporating live animals have been used to control insect locomotion, the microelectronic control of aquatic invertebrates has not been demonstrated. Aquatic invertebrates are particularly advantageous because swimming, compared to running and flying, exhibits a low cost of transport, a metric of energy efficiency in which lower values translate to higher efficiencies. We use Aurelia aurita as a model organism because of its demonstrated energy efficiency and simple body design dating past 500 million years, which can offer insights into both designing low-power robots and probing the structure-function of more basal organisms. Thus, we show the first demonstration of enhanced swimming capabilities and metabolic experiments with user-controlled inputs of live jellyfish, which provide new insights into the design spaces of both organisms and robots. In order to create a biohybrid robotic jellyfish, we first characterized the spatiotemporal response of jellyfish muscle to electrical stimulations to obtain a range of signal voltages, pulse durations, frequencies, and locations on the animal for successful muscle excitation. We then developed a microelectronic system that used these electrical signals at various frequencies for laboratory and in situ free-swimming experiments. Our laboratory results showed enhanced vertical swimming speeds up to 2.8 times compared to their baselines, while in situ experimental results showed similar vertical speed enhancements of up to 2.3 times in the presence of surface currents in the ocean. Finally, we used these experimental morphological and time-dependent input parameters to develop a hydrodynamic model to show predictable swimming speeds and trends in enhancements. We also conducted a series of metabolic experiments that showed a twofold increase in the animals' oxygen consumption, which is less than the increase in the animals' speed. These values accord with our theoretical model, which suggests the possibility of both faster and more efficient jellyfish swimming. This work also demonstrated improved energy efficiency compared to other aquatic robots in the field. The microelectronic components consumed only 10 mW, which was 10 to 1000 times less external power per mass than other swimming robots reported in literature. With the successful deployment of biohybrid robotic jellyfish in field tests off the coast of Massachusetts, the implications of the present study suggest that further iterations of this biohybrid robotic jellyfish could be used for practical applications in ocean monitoring. Future work can improve robotic maneuverability and incorporate sensors to track data, such as temperature and acidity