Researchers at Thayer School of Engineering at Dartmouth College and City University of Hong Kong are said to have combined cardiac tissue engineering, a 3D-printed wing structure and a light-sensitive gel to produce the soft robot. The switchable device transforms its shape when exposed to skin-penetrating near-infrared light, causing it to start and stop through fluid environments like the human bloodstream.
The team in Hong Kong produced the original robot design and performed the experimental tests. In the US, researchers performed mechanical and numerical analysis on the device.
"With this technology we can create soft transformable robots with unprecedented manoeuvrability," said Zi Chen, an assistant professor of engineering at Thayer.
The new study is said to be part of a long-term effort to develop robots that mimic shape-changing behaviours found in nature. To be effective, the new generation of robots need to be energy efficient and able to respond to stimuli such as light or heat.
According to Thayer, this class of robot already exists but researchers have struggled to create a device that fluently transforms its shape to allow it to start and stop moving on demand. Current systems also depend on temperature variations that are difficult to stimulate in the human body because of its nearly-constant temperature.
"The ability to control the robot's motion using light creates a much more functional device that can be operated with high precision," said Xiaomin Han, a recent PhD graduate from the Chen Research Lab at Thayer.
The remote-controlled robot is driven by a tail fin that mimics the swimming action of whales. The structure was 3D printed in the shape of an airplane wing and then coated with heart muscle cells. In the same way that cardiomyocytes cause the heart to beat continuously, they also propel the biohybrid device through an undulating action.
To control the movement of the robot, researchers applied photosensitive hydrogels to the wings. In the absence of light, the wings deploy, allowing the heart cells to propel it forward. When exposed to light, the floating plane retracts its wings, causing it to stop.
"The heart muscles keep churning, but they are unable to overcome the stopping power of the wings," Chen said in a statement.
The robot's sensitivity to near-infrared light creates a response rate that allows an almost immediate transformation of wing shape, allowing it to be highly manoeuvrable. In the study, researchers used the "unprecedented controllability and responsiveness" of the floating-plane robot as a cargo carrier to conduct targeted drug delivery against cancer cells.
"We literally dropped drug bombs on cancer cells," said Chen. "The realisation of the transformable concept paves a pathway for potential development of next-generation intelligent biohybrid robotic systems."
The biohybrid robot can be produced in numerous sizes ranging from several millimetres to dozens of centimetres. Such scalability gives it good flexibility to take on tasks related to navigation and surveillance in difficult environments.
A study describing the research first appeared in the academic journal Small in March. In the current study, researchers control start-stop motion of the entire robot through the use of light.
Future research will use light to target separate wings on the robot so that it can be steered with even more precision.
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