Wireless and batteryless two-dimensional opto-electro-mechanical positioner inside 3 T MRI scanner

To present a wireless, batteryless, and optically powered two-dimensional (2D) electro-mechanical positioner operable inside a 3 T MRI scanner.

The system uses Lorentz force actuators, each comprising a coil connected to a monocrystalline silicon solar cell, leveraging the scanner's strong B₀ field. Six actuators form a rotor; two rotors are used to construct the 2D positioner using plastic, glass, and ceramic parts for MRI compatibility. The rotor is modeled using circuit-based analytical and numerical simulations, incorporating the solar cell's nonlinear current-voltage behavior. A custom coil is designed for 3 T to maximize mechanical power.

Experimental validation includes dynamic torque measurements inside a 53 mT home-made desktop Helmholtz coil. The clinical-grade 3 T MRI scanner experiments demonstrate successful positioning in X and Y directions via remote laser diode control and power transmission through fiber optic cables. The rotor achieves 150 rotations per minute and 3.4 mN∙m torque at 6.3 mW/mm² optical intensity, amplified to 194 mN∙m by the gear train. The positioner attains a linear velocity of 2.2 mm/s with an open-loop accuracy of 1.5 mm, verified using MR images. The system shows stable behavior without imaging artifacts during in-scanner operation.

This is the first demonstration of a remotely controlled, optically powered 2D positioner operating wirelessly inside a clinical 3 T MRI. It enables precise marker placement or mechanical stimulation and can be extended to 5 degrees of freedom for MRI-guided interventions such as biopsies.