Steffen Greiser

Ferrofluid-based Flow Manipulation and Locomotion Systems

The article demonstrates some examples of locomotion systems with bifluidic flow control using ferrofluid. By controlling the change of shape, position, and pressure of the ferrofluid in a secondary low viscous fluid by magnetic fields locomotion of objects or the ferrofluid itself can be realized. The locomotion of an object is caused, in the first example, by a ferrofluid generated flow of the secondary fluid and in the second and third case by the direct alteration of the ferrofluid position.

Position control of magnetic beads by means of electromagnetic fields with respect to apodal locomotion systems

Motivated by the technical progress, electromagnetic action principles are more and more used in micro systems. It is well known that the discrete positioning of magnetic beads like ferrofluid droplets can be realised using an array of electromagnets whereat the position of the beads depends on the arrangement of the electromagnets. nThis paper refers to the analogous positioning of magnetic beads independent from the arrangement of the electromagnets. Therefore a control strategy was designed to position magnetic beads like ferrofluid droplets, ferrogels or ferroelastomers. The derived control law allows the definition of dynamic properties like time and damping constant. To achieve these properties, the controller is adjusted based on a model of the plant. This model regards the dynamical movement of the mentioned materials in electromagnetic fields and is characterised by simplified, nonlinear, ordinary differential equations. nThe theoretical results are verified by means of a basic assembly allowing the positioning of spherical ferroelastomers on macro scale. The measurements illustrate that the theoretically derived position controller meets the requirements of a predefined time and damping constant.