Magnetic torque-based method for quantifying the flexural rigidity of microfibers

Probing the flexural rigidity of micropillars and microfibers is challenging as they are short and difficult to handle. We developed a magnetic torque methodology where a coil-generated uniform magnetic field acts on a magnetic microrod attached to the fiber end, forcing it to turn. It is shown that magnetic torque bends microfiber in a circular arc, whose radius depends on the flexural rigidity. Magnetic microrods were fabricated by electroplating nickel on tungsten microwires. The methodology was validated with synthetic microfibers. Available magnetic stages for optical microscopes offering uniform magnetic fields within a millimeter-wide spot can be implemented to study a variety of beam-like microstructures.