(181ag) Diamagnetic Particle Deflection In Paramagnetic Fluids Using Embedded Permanent Magnets

A variety of force fields have been demonstrated to manipulate particles in microfluidic devices, among which electric, optical, acoustic, and magnetic forces are the most-often used ones. Magnetic field-induced particle manipulation is potentially the simplest and cheapest method, and is free of heating issues that accompany most other techniques. We develop an approach to embedding permanent magnets into poly(dimethylsiloxane) (PDMS), so that strong magnetic field gradients can be realized on-chip. Within such a microfluidic chip, we perform an experimental study of diamagnetic deflection of polystyrene particles in manganese(II) chloride (MnCl2) solutions. The effects of flow rate, particle size, and MnCl2 concentration on particle deflection are examined. The experimental results agree quantitatively with the predictions from an analytical model.