Miniature robots at the millimeter scale typically struggle to carry instruments for endoscopic microsurgery within the body. Researchers from the German Cancer Research Center (DKFZ) are now combining multiple millimeter-sized TrainBots into a single unit and enhancing them with better “feet.” This marks the first time the DKFZ team successfully conducted an electric surgical procedure for a bile duct obstruction using a robotic convoy in an experimental setting.
The potential uses for tiny robots in medicine are vast, including targeted drug delivery, sensory functions, and surgical tasks. A variety of robots have already been designed and tested for these purposes, spanning sizes from nanometers to centimeters.
However, the current small-scale robots often face limitations. For instance, in endoscopic microsurgery, the tools needed can be too heavy for a single millimeter-sized robot to carry effectively. Additionally, many of these robots must crawl, but numerous areas inside the body are lined with mucus, causing the robots to slip and become immobilized.
“Spikes” on the feet provide three times the propulsive force
A research team led by Tian Qiu at DKFZ in Dresden has addressed both challenges by developing the TrainBot, which links multiple individual millimeter-scale robots. These units feature enhanced anti-slip feet and can collectively transport an endoscopic instrument. The TrainBot operates wirelessly; a rotating magnetic field controls each unit simultaneously. This magnetic system allows for two-dimensional movement while also managing rotation, tailored for the scales relevant within the human body.
Microsurgery in the bile duct
The researchers from DKFZ in Dresden have already used a convoy of three TrainBots to simulate a surgical intervention. In cases of bile duct cancer, the duct can become blocked, leading to a dangerous build-up of bile. Once diagnosed endoscopically, it’s crucial to clear the obstruction. A flexible endoscope is inserted through the mouth and into the small intestine, where it must then navigate a sharp turn into the bile duct.
“This is where the flexible robot convoy showcases its advantages,” explains the project leader, Tian Qiu. His team demonstrated this with organs obtained from a pig. The robot convoy successfully guided an endoscopic tool for electrical tissue ablation in the bile duct. When the wire electrode’s tip reaches the blockage, electrical energy is applied to gradually remove the tissue obstruction, a technique known as “electrocauterization.” The electrode used measured 25 cm and weighed over three times more than a single TrainBot unit. “After this procedure, another TrainBot convoy can transport a catheter for fluid drainage or drug administration,” adds Moonkwang Jeong, the paper’s lead author. “Given our promising outcomes with the TrainBots in this organ model, we are hopeful about developing teams of miniature robots for additional endoscopic surgical tasks.”
