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Plastic surgery

Origami-inspired surgical robots sliced down to size

Image credit: Dreamstime

Harvard University researchers have used an origami-inspired technique to enhance the precision and control of teleoperated surgical robots.

Minimally invasive laparoscopic surgery – in which tools and a tiny camera are inserted into small incisions to perform operations – has rendered surgery markedly safer over the past half-century.

Recently, surgical robots have been introduced to operating theatres to assist surgeons by allowing them to manipulate many tools at once with better precision, flexibility and control than was previously possible.

However, these robotic systems are so large that they often take up an entire room, with tools much larger than the delicate biological structures on which they operate.

In an effort to bring surgical robots down to size, Professor Robert Wood from Harvard’s Wyss Institute for Biologically Inspired Engineering has been working with Sony to create a miniaturised remote centre of motion manipulator: a “mini-RCM”. The robot is the size of a tennis ball and weighs barely as much as a penny coin.

Wood and Sony engineer Hiroyuki Suzuki used a manufacturing technique (“MEMS”) developed in Wood’s laboratory in which materials are deposited in layers and bonded together, then laser-cut in a pattern which allows for a 3D shape to “pop up” out of the structure. This technique hugely simplifies the production of tiny, complex structures which would be impractical to mass produce by hand.

They created a parallelogram shape for the main structure of the robot, then added three linear actuators (made from a piezoelectric ceramic which changes shape when an electrical field is applied) to control its movement: one to raise and lower it; one to rotate it, and one to extend and retract its tool. The result was a robot far smaller and lighter than alternative microsurgical devices.

The researchers connected the mini-RCM to a device which manipulates it in response to the movements of a user controlling a pen-like tool. The first test evaluated a human’s ability to trace a microscopic shape looking through a microscope; this showed that the mini-RCM significantly steadied the hand, reducing error by 68 per cent compared to manual operation.

The researchers then created a mock-up of a retinal vein cannulation – in which the surgeon must inject therapeutics into the veins at the back of the eyeball – with a silicone tube the same size as the retinal vein. Using the mini-RCM, they were able to puncture this tube without causing any local damage.

“The Pop-Up MEMS method is proving to be a valuable approach in a number of areas that require small yet sophisticated machines and it was very satisfying to know that it has the potential to improve the safety and efficiency of surgeries to make them even less invasive,” said Wood.

Wood and Suzuki aim to increase the force of the robot’s actuators to cover the maximum forces experienced during an operation and improve its positioning precision.

The report describing this work has been published in Nature Machine Intelligence.

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