The list of creatures that have inspired scientists to build synthetic, or biomimetic, devices just got longer, according to a report in Nature Biotechnology (DOI: 10.1038/nbt.2269). John O. Dabiri of Caltech, Kevin Kit Parker of Harvard University, and coworkers have engineered a thin, eight-armed polymeric sheet to swim like a jellyfish. To accomplish the feat, the team mapped the pumping motions of a juvenile jellyfish while it was swimming. Then the researchers used the collected information to build a mimic from three simple components, says Janna C. Nawroth, a graduate student at Caltech and lead author of the report. The first of these parts is a spin-coated 22-µm-thick polydimethylsiloxane film. Onto that layer, the team printed the protein fibronectin in a pattern simulating jellyfish muscle-fiber alignment. Finally, the researchers seeded rat heart cells onto the structure and incubated them until they formed electrically conductive tissue. The resulting mimic, called a medusoid, swims like a jellyfish when exposed to a pulsed electrical field. Aside from being a model system to inspire the development of future tissue-engineered organs that pump, Nawroth says, these medusoids might eventually be used to test drugs for cardiac disease.