Made of hard material yet supple: Inspired by the pangolin, German researchers have developed a magnetically controllable robot made of metal elements that could be used in the body for medical missions. It can adapt its form to the task at hand, absorbing charge and selectively releasing it. Above all, however, the metallic material can be effectively heated by magnetic fields, so that bleeding or tumors, for example, can be treated, as tests show.
Small robots that travel in the patient's body in the service of medicine: this futuristic-looking vision is taking shape due to technical advances in recent years. Above all, they are working on concepts of so-called soft robotics, because constructions made of flexible materials are particularly suitable for use in the sensitive structures inside the body. Metallic materials could open up additional capabilities for the technology - but so far there has been one disadvantage: they become inflexible at certain material thicknesses.
Helpful nature patent
But as with many technical challenges, you can obviously get advice from nature in this case: the development team led by senior author Metin Sitti from the Max Planck Institute for Intelligent Systems (MPI-IS) in Stuttgart has decided to move away from the "patent" of the pangolin. The bodies of these whimsical mammals are heavily armored yet flexible. This is made possible by scales made of the hair and nail building material keratin, which overlap and are directly connected to the soft layer of skin underneath. Due to this special arrangement, the animals can curl up tightly in case of danger, despite the hard basic substance.
The Stuttgart scientists have now converted this natural patent into a metallic soft robotic concept: It is a flat, rectangular structure that is about two centimeters long and consists of two layers. The counterpart to the animal's keratin scales are small, hard, overlapping platelets made of a metallic material. This layer sits on a layer of flexible polymer material into which additional magnetic particles have been integrated.
The robot is soft and flexible, although it consists of comparatively massive metal elements that enable special functions. If the robot is exposed to a low-frequency magnetic field, the scientists can move it wirelessly and without contact: the plate can be rolled in and out and, when round, maneuvered to specific locations. The metal elements protrude slightly like the animal's scales, without damaging the surrounding tissue.
Flexible, agile and heatable
By testing organ models and prepared pig stomachs, the scientists were then able to document the performance of the concept and the medical potential. It becomes clear that the pangolin robot can be guided flexibly and effectively through the digestive system with the help of magnetic fields. Above all, it could also reach the small intestine, which is difficult to access. When rolled up, it could also transport objects such as medicines inside and then release them at certain points, the tests show.
The special ability of the pangolin robot, however, is its ability to overheat: If it is exposed to a high-frequency magnetic field, it heats up to over 70 degrees Celsius thanks to the metallic material. As the team explains, there is considerable potential for medical applications. Because thermal energy is used, for example, in the treatment of thrombosis or tumor tissue and to stop bleeding. The scientists showed that the pangolin robot could fulfill a corresponding mission in the digestive tract by testing a pig stomach model: they maneuvered it to a simulated bleeding site and then heated it up. In this way, the robot was able to produce an effect that would lead to hemostasis under real conditions.
Further developed versions of the robot could one day reach even the narrowest and most sensitive regions of the body in a minimally invasive and gentle manner and carry out treatments there. However, the concept is still at an early stage of development, according to first author Ren Hao Soon from the MPI-IS. "Some questions still have to be clarified and technical challenges solved, but I'm confident about that," says the researcher. "In order to determine possible applications, I now also hope to work closely with clinical experts," says Soon.
Video: The pangolin robot performs an experimental mission to stop bleeding in a pig stomach. © MPI for Intelligent Systems
Source: Max Planck Institute for Intelligent Systems, specialist article: Nature Communications, doi: 10.1038/s41467-023-38689-x