On-chip magnetic particle transport: where physics, chemistry and biology meet

Magnetic biosensors are emerging as promising alternatives for classical fluorescent-based micro-arrays, replacing the fluorescent label by a super-paramagnetic particle. While on-chip detection of magnetic particles is firmly established, research groups now start to explore the unique ability of manipulating these particles by applying controlled magnetic forces. In this paper, we describe the importance of magnetic, hydrodynamic and electrostatic forces in the actuation of magnetic particles. The use of magnetic actuation for biological applications in which aqueous solutions with high ionic strengths are often used, increases the need to study the effect of electrostatic forces into greater detail. We conclude that for transport of magnetic particles, suspended in aqueous solutions with a high ionic strength, the electrostatic force starts to become an important factor. Therefore, a quantitative study of air forces acting on the magnetic particle is necessary for a further development of magnetic force generating structures.