Miniature robots in convoy carry endoscopic instrument for microsurgery

Millimeter-scale miniature robots often lack the strength to transport endoscopic microsurgery instruments across the body. Scientists at the German Cancer Research Center (DKFZ) are now combining several millimeter-sized TrainBots into a single unit and equipping them with improved “feet”. For the first time, the DKFZ team was able to experimentally carry out electrical surgery on bile duct obstruction with a robotic conveyor.

The list of conceivable applications of miniature robots in medicine is long: from targeted drug application to sensing tasks and surgical interventions. An arsenal of robots has already been developed and tested for this range of tasks, from nanoscale to centimeter scale.

However, the little helpers available today reach their limits in many tasks. For example, in endoscopic microsurgery. The required instruments are often too heavy for a single-millimeter robot to transport to their destination. Another common problem is that robots often have to crawl. However, the surfaces of many body structures are covered in mucus on which the robots slide and cannot move.

A team led by Tian Qiu at the DKFZ in Dresden has developed a solution to both problems: their TrainBot connects several individual robots on a millimeter scale. Units feature improved non-slip feet. Together they are capable of carrying an endoscopic instrument.

The TrainBot unit works wirelessly; a rotating magnetic field controls the different units simultaneously. Magnetic control allows movements in one plane with rotation control. The external actuation and control system is designed for distances on the scale of the human body.

The article is published in the journal Advanced science.

Microsurgery in the bile ducts

DKFZ researchers based in Dresden have already used their robotic convoy consisting of three TrainBot units to simulate a surgical procedure. In the case of bile duct cancer, the bile ducts often become blocked, causing bile to flow back, which is a very dangerous situation for those affected.

In this case, the occlusion must be opened after endoscopic diagnosis. To do this, a flexible endoscope is inserted through the mouth into the small intestine and from there into the bile duct. One of the major difficulties here is that the endoscope bypasses the acute angle going from the small intestine to the bile duct.

“This is where the flexible robot convoy can show its strengths,” explains project manager Tian Qiu. His team demonstrated this using organs taken from a pig. The convoy of robots was able to operate an endoscopic instrument for electrical ablation of tissue in the bile ducts.

Once the tip of the wire electrode arrives at the site, an electrical voltage is applied and a tissue blockage is gradually removed electrically, a procedure known as “electrocautery.” The wire electrode used was 25 cm long and three and a half times heavier than a TrainBot unit.

“Then, for example, another TrainBot convoy can bring a catheter for fluid drainage or drug delivery,” says Moonkwang Jeong, the first author of the paper. “After the promising results obtained with TrainBots in the organ model, we are optimistic about our ability to develop teams of miniature robots for other tasks in endoscopic surgery.”