一种制备磁性聚二甲基硅氧烷微柱的新技术

In past decades, polymeric micropillars have been employed in many complex functional micro‐devices, such as micro‐fluids, micro‐sensors, tunable wetting surfaces, and substrate structures. This paper presents a novel technique to fabricate high‐aspect‐ratio magnetic polydimethylsiloxane (PDMS) micropillars that can move under gradient magnetic fields. First, a drop of Fe3O4 superparamagnetic nanoparticles was dispersed in acetone solution, sonicated, and poured over a pre‐etch silicon mold with deep micro‐holes. Second, we quickly attracted Fe3O4 nanoparticles in micro‐holes with a strong permanent magnet at the silicon mold's backside. Third, we used a soft lithography process to force the PDMS liquid to flow into the micro‐holes by sequencing the air in a vacuum chamber, baked in a hot plate, and then peeled off in ethanol solution and dried in a CO2 dryer machine. The diameters of PDMS magnetic micropillars were from 1 μm, 2 μm to 10 μm, and the heights were 30 μm and 50 μm. We observed 1 μm micropillar with 50 aspect ratio could deflect its end up to 12 μm under a gradient magnetic field of 5 mT/mm. The magnetic micropillar end movement in an ethanol solution was validated, which broads the application to micro‐fluidics and other liquid microdevices. The energy‐dispersive X‐ray spectroscopy also examined the iron percentage in PDMS micropillars. They were in a range of 42% to 81.4%; with the median value was 59.6% that is the highest value reported in the literature, to our best knowledge.