Engineers bring surgical robots down to microscale size

In a collaboration between Harvard and Sony, engineers have brought surgical robotics down to the microscale by creating a new, origami-inspired miniature manipulator to improve precision and control.

The robotic systems that currently assist surgeons in laparoscopic surgery can often take up an entire room, their tools  larger than the delicate tissues and structures on which they operate.

Wyss Associate Faculty member Robert Wood and robotics engineer Hiroyuki Suzuki of Sony Corp. have designed the “mini-RCM,” a robot the size of a tennis ball, weighing about as much as a penny, and  successfully performing a difficult mock surgical task, as described in a recent issue of Nature Machine Intelligence.

A mini-robot for micro tasks

To create their miniature surgical robot, Suzuki and Wood turned to the Pop-Up MEMS manufacturing technique developed in Wood’s lab, in which materials are deposited on top of each other in layers that are bonded together, then laser-cut in a specific pattern that allows the desired 3D shape to “pop up,” as in a children’s pop-up picture book. This technique greatly simplifies the mass-production of small, complex structures that would otherwise have to be painstakingly constructed by hand.

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The team created a parallelogram shape to serve as the main structure of the robot, then fabricated three linear actuators (mini-LAs) to control the robot’s movement: one parallel to the bottom of the parallelogram that raises and lowers it, one perpendicular to the parallelogram that rotates it, and one at the tip of the parallelogram that extends and retracts the tool in use. The result was a robot that is much smaller and lighter than other microsurgical devices previously developed in academia.

The mini-LAs are themselves marvels in miniature, built around a piezoelectric ceramic material that changes shape when an electrical field is applied. The shape change pushes the mini-LA’s “runner unit” along its “rail unit” like a train on train tracks, and that linear motion is harnessed to move the robot. Because piezoelectric materials inherently deform as they change shape, the team also integrated LED-based optical sensors into the mini-LA to detect and correct any deviations from the desired movement, such as those caused by hand tremors.