Over the past few years, groups of scientists have been investigating different ways to use miniature robots for medical purposes to help treat diseases. The robots that have been developed are designed to enter the body, where they can deliver drugs at specific locations or perform precise operations, for example, clearing clogged arteries. These kinds of robots are expected to improve the medical field by replacing invasive and complicated surgeries.
Now EPFL scientist Selman Sakar, and Hen-Wei Huang and Bradley Nelson from ETH Zurich, teamed up to develop a simple and adaptable method for building these kinds of bio-inspired robots and providing them with advanced features. They also created a platform for testing different robot designs and studying different modes of locomotion.
Their work resulted in complex reconfigurable microrobots that can be manufactured in large quantities. They built an integrated manipulation platform that can remotely control the robots’ mobility with electromagnetic fields and cause them to shape-shift using heat.
Unlike ordinary robots, these microrobots are soft, flexible and require no motors. They are composed of a biocompatible hydrogel and magnetic nanoparticles, which have two functions: giving the microrobots shape during the manufacturing process, and making them move and swim when an electromagnetic field is applied.
Building one of these microrobots involves several steps: (1) The nanoparticles are placed inside layers of a biocompatible hydrogel; (2) an electromagnetic field is applied to position the nanoparticles at different parts of the robot; and (3) the polymerization step “solidifies” the hydrogel. Lastly 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 3-D style of the microrobot.
When the final shape is attained, an electromagnetic field is used to make the robot swim. Then, once it is heated, the robot changes shape and “unfolds.”
This approach allowed the researchers to build microrobots that mimic the bacterium that causes African trypanosomiasis, also known as sleeping sickness. This particular bacterium uses a flagellum for propulsion, but hides it away once inside a person’s bloodstream as a survival mechanism.
The researchers tested different microrobot designs to come up with one that imitates this behavior.
The prototype robot has a bacterium-like flagellum that allows it to swim. When it is heated with a laser, the flagellum wraps around the robot’s body and is “hidden.”
“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.”
The microrobots are still in development. The researchers still need to take into account a variety of factors. For example, they need to ensure that they will not cause any harmful side-effects in patients.