ALEXANDRIA, Va., March 26 -- United States Patent no. 12,257,005, issued on March 25, was assigned to Northern Digital Inc. (Waterloo, Canada).
"Tracking a sensor that includes a ferrofluid" was invented by Nikolai Mikuszeit (Radolfzell, Germany).
According to the abstract* released by the U.S. Patent & Trademark Office: "A system comprising: one or more field generating coils configured to generate a magnetic field; a sensor comprising a shell that contains a ferrofluid, the sensor configured to be introduced in proximity to the magnetic field, wherein the ferrofluid causes distortion of the magnetic field when the ferrofluid is in proximity to the magnetic field; and one or more field measuring coils configured to: measure a characteris...