  The vast majority of the ocean's volume remains unexplored, in part because
of limitations on the vertical range and measurement duration of existing
robotic platforms. In light of the accelerating rate of climate change impacts
on the physics and biogeochemistry of the ocean, the need for new tools that
can measure more of the ocean on faster timescales is becoming pressing.
Robotic platforms inspired or enabled by aquatic organisms have the potential
to augment conventional technologies for ocean exploration. Recent work
demonstrated the feasibility of directly stimulating the muscle tissue of live
jellyfish via implanted microelectronics. We present a biohybrid robotic
jellyfish that leverages this external electrical swimming control, while also
using a 3D printed passive mechanical attachment to streamline the jellyfish
shape, increase swimming performance, and significantly enhance payload
capacity. A six-meter-tall, 13,600-liter saltwater facility was constructed to
enable testing of the vertical swimming capabilities of the biohybrid robotic
jellyfish over distances exceeding 35 body diameters. We found that the
combination of external swimming control and the addition of the mechanical
forebody resulted in an increase in swimming speeds to 4.5 times natural
jellyfish locomotion. Moreover, the biohybrid jellyfish carried a payload
volume up to 105% of the jellyfish body volume. The added payload decreased the
intracycle acceleration of the biohybrid robots relative to natural jellyfish,
which could facilitate more precise measurements by onboard sensors. In
contrast with existing robotic exploration tools, this platform is inexpensive,
highly efficient, and benefits from the widespread natural habitats of
jellyfish. The demonstrated performance of these biohybrid robots suggests an
opportunity to expand the set of robotic tools for comprehensive monitoring of
the changing ocean.
