Many animals have evolved camouflage to evade both predators and prey. The moon jellyfish (Aurelia aurita) takes this strategy further: with its near-transparent body, the species blends into and thrives in open oceans worldwide.
Inspired by the moon jellyfish’s form and function, a team of researchers from A*STAR’s Singapore Institute of Manufacturing Technology (SIMTech), the National University of Singapore, and the Chinese University of Hong Kong, Shenzhen, China, have created a new ‘soft’ robot that not only swims like A. aurita, but looks just as glasslike.
“Integrating transparency into soft robots can be valuable for many applications, such as non-disruptive underwater surveillance, allowing researchers to observe aquatic animals in their natural habitats,” said Yuzhe Wang, a SIMTech Senior Scientist and first author of the study.
It’s not easy to transition robots from metallic structures to soft, translucent blobs, as most conventional motors, actuators and chassis used in robotics aren’t designed to be see-through. To overcome this limitation, the team aimed to develop a new type of dielectric elastomer actuator (DEA) which would be both fully transparent and able to mimic the moon jellyfish’s pulsating, rhythmic motions underwater.
“DEAs stand out among other soft actuation technologies; they’re flexible polymers that can deform greatly under applied voltage,” said Wang. “They also have high energy density, fast response times, low weights and quiet operations. Crucially, they can be made extremely thin—DEAs can comprise just a single dielectric membrane and two layers of compliant electrodes.”
Wang and colleagues examined the ability of DEAs to form thin structures with smooth surface curvatures that minimise diffuse reflections. While other jellyfish-like soft robots have previously been developed using DEAs, these DEAs typically use opaque materials like carbon grease for electrodes.
To create a transparent and highly conductive DEA, the team developed a novel hybrid compliant electrode that combines a conductive polymer, PEDOT:PSS/WPU, with silver nanowires—a popular component in flexible electronics. The researchers then used two layers of such hybrid electrodes—each layer a mere 1 µm thick—to sandwich a transparent dielectric membrane, then sealed the three layers with a waterproof silicone-based coating.
When the team applied voltage across the DEA, it expanded its area by up to 146 percent, while only exhibiting a 3 percent energy loss during cyclic actuation.
Using their DEA to construct a jellyfish robot, the researchers found that the robot’s bell-shaped DEA ‘body’ could stretch and contract like a muscle. The robot was also capable of imitating the moon jellyfish’s vertical and horizontal movements in water, and had an average visible light transmittance of 87 percent across its body; many transparent and translucent deep-sea animals have a range between 50 and 90 percent.
According to Wang, their biologically-inspired robot is a breakthrough in soft robotics that could invite new opportunities in stealthy underwater surveillance, environmental research and marine education. The robot’s mimicry of natural biological movements not only improved its function, but also allowed the robot to integrate into aquatic environments.
“We plan to explore enhancements to soft robot durability and robustness,” said Wang. “In future, a fully-contained soft robot driven by these transparent soft actuators could house power sources, electrical circuits, microcontrollers, cameras and sensors.”
The A*STAR-affiliated researchers contributing to this research are from the Singapore Institute of Manufacturing Technology (SIMTech).
