A novel technique to fabricate magnetic polydimethylsiloxane micropillar

Abstract

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.

Functional PDMS Elastomers: Bulk Composites, Surface Engineering, and Precision Fabrication

“…However, by adding magnetic components, the composites can be equipped with magneto-active properties for new-generation magnetic actuators. [36] A recently explored architecture is a cilia-inspired pillar array, [37][38][39] which can swing back and forth in response to an external magnetic field. The hair-like micro-actuator array was fabricated by filling pre-designed templates or molds with a composite paste made of PDMS prepolymer and magnetic particles, as illustrated in Figure 3a.…”

Control of the asymmetric growth of nanowire arrays with gradient profiles

“…Indeed, the elongated cylindrical geometry of these nanostructures is susceptible to the appearance of confinement and size-dependent effects and quantum mechanical optical, magnetic, and electrical properties. 34–37 Other systems consisting of arrays of programmable stimuli-responsive hybrid magnetic micropillars, polydimethylsiloxane micropillars, and slanted functional gradient micropillars have been proposed as novel prototypes for reconfigurable patterns upon actuation, 38,39 microfluidics 40 and bioinspired dry adhesives as self-cleaning superhydrophobic and biosensing applications, 41 respectively. Previous works on the use of a combined technique based on electrodeposition and dip-coating have been developed to synthesize gradients with transversal section widths of the order of 10 2 –10 3 μm.…”