Fabrication and testing of integrated permanent micromagnets for microfluidic systems

magnetic powder and polydimethysiloxane bonded material that can be micropatterned into micromagnets. The magnetic powder, with an average particle size of 5 m-6 m, has been prepared from an alloy ingot of raw materials which are put in a va cuum induction furnace and melt spun to obtain ribbons with nanocrystalline microstructure. The ribbons are crushed using vibrating ball milling under inert atmosphere to obtain coarse powder (average particle size of 200 m). In order to obtain 5 m fine powder the course powder is jet milled at 6000rpm under inert atmosphere. The fine magnetic powder (referred to as MQFP-15) is ultrasonically uniformly dispersed in a polydimethylsiloxane matrix (PDMS) using a horn tip probe operating at a frequency of 42 kHz. Micromagnets (diameter of 50 m, height 30 m) are fabricated from the prepared composite via soft lithography and are tested using a SQUID magnetometer, showing a remanent magnetization (M