You May Soon Be Treated With Remote-Controlled Microrobots

As overall death rate has risen for the first time in a decade in the US, scientists are actively look for ways to revolutionize medical treatment. A team of scientists at ETH Zurich and Ecole Polytechnique Fédérale de Lausanne EPFL has developed a new method of treating such diseases using remote-controlled microrobots.

The robots are designed to enter the human body where they can deliver drugs at target areas or perform precise operations like clearing blocked arteries. By replacing invasive, often risky surgical operations, they could enhance medicine. EPFL scientist Selman Sakar collaborated with Hen-Wei Huang and Bradley Nelson at ETH Zurich to engineer a multi-function and adaptable method to build these bio-inspired robots and give them highly advanced multi-features. They also developed a platform for testing several robot designs and studying different methods of motion. Their work, published in Nature Communications, produced revolutionary programmable microrobots that can be manufactured with high throughput. The platform they built can be manipulated using electromagnetic fields which they can use to remotely control the robots, and cause them to change their form using heat.

Unlike typical robots which are rigid, mechanical and metallic, these robots are inspired by nature and are soft, flexible and motor-less. The robots are made out of metallic nanoparticles and bio-compatible hydrogel which allows for control using electro-magnetic fields and better propulsion through the body fluids.

Developing one of these microbots involves several steps. First, the nanoparticles are placed in inside layers of the biocompatible hydrogel. Then an electromagnetic field is applied to orientate the nanoparticles at different parts of the robot, followed by a polymerization step to “solidify” the hydrogel. After this, the robot is placed in water where it folds in specific ways depending on the orientation of the nanoparticles inside the gel, to form the final overall 3D structure of the microbot. Under different temperatures, the structure shape-shifts differently. This process is completely reversible and the micromachines will fold and unfold back to their initial state when they are cooled down.

This fabrication approach allowed the researchers to build microrobots that mimic the bacterium that causes African trypanosomiasis, otherwise known as sleeping sickness. This particular bacterium uses a flagellum, a tail like structure that allows bacterium to swim, for propulsion, but hides it away once inside a person’s bloodstream as a survival technique. The scientists verified that the propulsion is due to coupling between the flagellum and the body and not due to the magnetic field when the flagella were removed from the compound micromachines. Without the flagella, the devices rolled in place and did not propel forward. Another fascinating observation was that the swimming movement of the microbots depended on both the rate and direction of rotation of the magnetic field.

The design of these microbots was inspired by bacterial evolution. In nature, motile organisms are able to drastically change their morphologies and motion mechanisms to adapt to changes in their microenvironment. African trypanosomes exhibit a long slender form with a free flagellum that propels the organism through bodily fluids and penetrates the blood vessels to invade extravascular tissues. After entering the bloodstream, the bacterium changes its long slender form to a short and stumpy one for better survivability. Hence bio-inspired designs such as these increase resilience and adaptability of microrobots in extreme conditions and challenging environments.

“We show that both a bacterium’s body and its flagellum play an important role in its movement,” said Sakar. “Our new production method lets us test an array of shapes and combinations to obtain the best motion capability for a given task. Our research also provides valuable insight into how bacteria move inside the human body and adapt to changes in their microenvironment.”

Currently, the microrobots are still in the development phase. “There are still many factors we have to take into account,” says Sakar. “For instance, we have to make sure that the microrobots won’t cause any side-effects in patients.”

This is not the first robot to be inspired by nature. Recently a team of scientists from Harvard designed a light-sensitive robot out of heart cells of a rat. The robot’s shape was inspired by a stingray and its movements were engineered to follow a similar pattern. The cardiomyocytes are engineered in such a manner that they contract under a specific wavelength of light. When the muscles contract, the robot is propelled forward using its fins similar to a stingray. The robot automatically finds the source of light as it swims through the nutrient-rich liquid that keeps its cells alive, allowing it to be remotely controlled. Each wing is tuned to a different light pattern, allowing the it to turn and maneuver.

If the trend remains similar we will see a new breed of bio-engineered robots that are more adept, resilient and robust than traditional robots, in the near future. These advancements will greatly benefit the medical world, by cutting down operation costs and time, and increasing overall patient life expectancy due to their non-invasive nature of operation.

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