Medical ‘millirobots’ could replace invasive surgery

Using a “Gauss gun” principle, an MRI machine drives a “millirobot” through a hypodermic needle into your spinal cord and guides it into your brain to release life-threatening fluid buildup ...
May 28, 2015

Cross-section: three-component Gauss gun before (top) and after (bottom) firing (credit: Aaron T. Becker et al./Proceedings of the IEEE)

University of Houston researchers have developed a concept for MRI-powered millimeter-size “millirobots” that could one day perform unprecedented minimally invasive medical treatments.

This technology could be used to treat hydrocephalus, for example. Current treatments require drilling through the skull to implant pressure-relieving shunts, said Aaron T. Becker, assistant professor of electrical and computer engineering at the University of Houston.

But MRI scanners alone don’t produce enough force to pierce tissues (or insert needles). So the researchers drew upon the principle of the “Gauss gun.”

K&J Magnetics | Gauss Gun Demonstrations

Here’s how the a Gauss gun works: a single steel ball rolls down a chamber, setting off a chain reaction when it smashes into the next ball, etc., until the last ball flies forward, moving much more quickly the initial ball.

Based on that concept, the researchers imagine a medical robot with a barrel self-assembled from three small high-impact 3D-printed plastic components, with slender titanium rod spacers separating two steel balls.

Millirobot components (credit: Aaron T. Becker et al./Proceedings of the IEEE)

Aaron T. Becker, assistant professor of electrical and computer engineering at the University of Houston, said the potential technology could be used to treat hydrocephalus and other conditions, allowing surgeons to avoid current treatments that require cutting through the skull to implant pressure-relieving shunts.

Becker was first author of a paper presented at ICRA, the conference of the IEEE Robotics and Automation Society, nominated for best conference paper and best medical robotics paper.

“Hydrocephalus, among other conditions, is a candidate for correction by our millirobots because the ventricles are fluid-filled and connect to the spinal canal,” Becker said. “Our noninvasive approach would eventually require simply a hypodermic needle or lumbar puncture to introduce the components into the spinal canal, and the components could be steered out of the body afterwards.”

Future work will focus on exploring clinical context, miniaturizing the device, and optimizing material selection.

Abstract of Toward Tissue Penetration by MRI-powered Millirobots Using a Self-Assembled Gauss Gun

MRI-based navigation and propulsion of millirobots is a new and promising approach for minimally invasive therapies. The strong central field inside the scanner, however, precludes torque-based control. Consequently, prior propulsion techniques have been limited to gradient-based pulling through fluid-filled body lumens. This paper introduces a technique for generating large impulsive forces that can be used to penetrate tissue. The approach is based on navigating multiple robots to a desired location and using self-assembly to trigger the conversion of magnetic potential energy into sufficient kinetic energy to achieve penetration. The approach is illustrated through analytical modeling and experiments in a clinical MRI scanner.