Harnessing the oloid shape in magnetically driven robots to enable high-resolution ultrasound imaging

Abstract

Magnetic fields enable remote manipulation of objects and are ideal for medical applications because they pass through human tissue harmlessly. This capability is promising for surgical robots, allowing navigation deeper into the human anatomy and accessing organs beyond the reach of current technologies. However, magnetic manipulation is typically limited to a maximum two–degrees-of-freedom orientation, restricting complex motions, especially those including rolling around the main axis of the magnetic robot. To address this challenge, we introduce a robot design inspired by embodied intelligence and the unique geometry of developable rollers, leveraging the oloid shape. The oloid, with its axial asymmetry and sinusoidal motion, facilitates rolling when precisely controlled by an external magnetic field. We present a versatile closed-loop control model to ensure precise magnetic manipulation of an oloid-shaped robot. This capability was validated in endoluminal applications through the integration of a 28-megahertz micro-ultrasound array to perform virtual biopsies, noninvasive real-time histological imaging. Extensive in vitro and in vivo tests using a porcine model showed the robot’s ability to execute sweeping motions, identify lesions, and generate detailed three-dimensional scans of gastrointestinal subsurface tissue. This research not only restores a critical movement capability to magnetic medical robots but also enables additional clinical applications deep within the human body.