title: Sudden breakdown in linear response of a rotationally driven magnetic microparticle and application to physical and chemical microsensing.
abstract: In this work, sensing magnetic microparticles were used to probe both the local pH and the viscosity-dependent nonlinear rotational behavior of the particles. The latter resulted from a critical transition marking a driven particle's crossover from phase-locking to phase-slipping with an externally rotating magnetic field, i.e., a sudden breakdown in its linear response that can be used to measure a variety of physical quantities. The transition from simple rotation to wobbling is described both theoretically and experimentally. The ability to measure both chemical and physical properties of a system could enable simultaneous monitoring of chemical and physical interactions in biological or other complex fluid microsystems.
authors.affiliation: Applied Physics Program, 2477 Randall Laboratory, The University of Michigan, Ann Arbor, Michigan 48109-1120, USA.
authors.forename: Brandon H
authors.initials: BH
authors.lastname: McNaughton
authors.forename: Karen A
authors.initials: KA
authors.lastname: Kehbein
authors.forename: Jeffrey N
authors.initials: JN
authors.lastname: Anker
authors.forename: Raoul
authors.initials: R
authors.lastname: Kopelman