Tiny Surgical Robots Require Equally Tiny Components

The NISI surgical robot was used successfully on animals in the summer of 2018. Image: NISI

November 21, 2019      

Startup company NISI Limited is currently developing a miniature surgical robot that can be inserted though natural openings in the body, and only unfolds inside the abdomen. To achieve this goal, engineers are pushing components to their limits and beyond.

In the world of medical technology, there are many astonishing new developments these days. The world of surgical robots could be turned on its head soon: In summer 2018, the Hong Kong-based startup NISI announced it had successfully performed a series of gynecological operations on live pigs. This may not sound like anything special at first, however: For the operation, the surgeons used a small robot that had been inserted rectally. This is a world’s first, according to the company.

NISI was founded in 2012, and works with the universities of Hong Kong and Cambridge to develop a robotic system that enables complex, minimal-invasive surgeries in the abdominal and pelvic area without leaving visible scars. “We want to become the world’s leading expert in non-invasive robot technology,” says Dr. Corinna Ockenfeld at NISI. The successful surgeries in the summer of 2018 have given the medtech start-up a lot of momentum. Initial surgeries on humans are planned for 2021.

Benefits of tiny robots

The idea behind the NISI surgical system is as follows: The surgical robot is inserted through a natural orifice, usually the anus or the vagina. This way, only a small cut inside the body is necessary to introduce several surgical tools into the abdomen. Current systems require several incisions, one for each instrument. The new technology has a number of benefits: Less blood loss during surgery, fewer wound complications, shorter recovery time for the patient, and no visible scars.

The robot itself has two small arms that unfold inside the body, and can be controlled by the surgeon on a control panel. The two robotic arms are powered by micromotors from maxon, and have up to 10 degrees of freedom. The system also has high-resolution 2D and 3D cameras and delivers haptic feedback, so surgeons can feel what is happening at the other end and can work with the greatest precision.

The NISI surgical robot was used successfully on live pigs in 2018. Human surgeries are expected in 2021. Image: NISI

Bringing surgical robots to the next level requires more than outstanding technicians and engineers: Quality components are a key element. NISI is therefore testing various concepts and combinations of components. “We want to push the envelope in medical and robot technology,” says Ockenfeld. With regard to the motors, this requires an extremely small size and extremely high power density. “We are working closely with maxon and have a weekly exchange of information. We really appreciate the support we’ve received over the past years. The collaboration with maxon is highly productive and extremely valuable for both sides.”

The prototypes of the surgical robot currently use various brushless DC motors from the EC series, with diameters from 4 to 8 millimeters, complemented by matching planetary gearheads. Both partners are pushing the precision drives to their limits, sometimes running them outside the nominal specifications. However, the BLDC motors are customized for the specific needs. They require high power density, must fulfill extremely strict quality standards and be sealed against body fluids. In the future, the drives will also need to be biocompatible.

The next steps are to make the entire system even smaller, to make the motors even more dynamic, and to expand the working range of the robot. “We take care of every little detail and take innovative approaches to solving problems,” says Ockenfeld. Step by step, NISI is coming closer to its vision of making non-invasive surgery without scars something that can be taken for granted.

Additional medical technology reports can be found on maxon’s corporate blog.