A transcranial magnetic stimulation coil using rectangular braided Litz wire

A transcranial magnetic stimulation coil built by rectangular braided Litz wire is presented. The rectangular braided Litz wire used in this work is comprised of 2500 ultrafine wires, rated for high currents and voltages necessary for magnetic stimulation (10 kA, and 3 kV). The wire is only 7.3 mm wide and 0.9 mm thick making it amenable to tighter windings yielding high magnetic fields with a small coil diameter, and reduces coil heating issues. The coil is 3.1 cm in diameter and provides a magnetic field higher than the smallest available commercial coil despite being 40% smaller. This potentially expands research and therapeutic functionalities of transcranial magnetic stimulation, especially increases the stimulation specificity for use in neural prosthetic systems and bidirectional brain machine interfaces.