A Ferrofluidic Inertial Sensor Exploiting the Rosensweig Effect

In this paper, a novel device for sensing perturbations imposed to liquid media contained in a disposable housing is addressed. The device consists of a glass beaker filled with deionized water surrounding a small volume of ferrofluid; a permanent magnet is used to fix the position of the ferrofluidic mass in a compliant position and to generate spikes due to the Rosensweig effect. The effect of external stimuli on the beaker can be estimated by measuring the perturbation produced on the ferrofluidic mass. The latter strategy allows reducing drawbacks related to static friction of conventional inertial devices. The ferrofluid perturbations are monitored by two external planar coils in a differential configuration. The main features of the proposed strategy are structural decoupling between the electric read-out system and beaker housing, which allows both implementing noninvasive measurement in liquid media and making the architecture partially disposable, of low cost, and suitable for real applications.