Featured in NPG Asia Materials

posted Jul 5, 2010, 7:04 PM by Shin-Hyun Kim   [ updated Jul 5, 2010, 7:20 PM ]
Nature Publishing Group’s Asia Materials featured our Communication in Angewandte Chemie International Edition on Magnetic particles as a Research Highlight. (http://www.natureasia.com/asia-materials/highlight.php?id=718)
Shin-Hyun Kim, Jae Young Sim, Jong-Min Lim and Seung-Man Yang, “Magneto-responsive Microparticles with Nanoscopic Surface Structures for Remote-Controlled Locomotion,” Angewandte Chemie International Edition, 49, 3786 –3790 (2010)  
Yang and his colleagues performed their manipulation experiment on ‘Janus’ particles — particles having at least two faces that are physically or chemically distinct — prepared from a colloidal suspension of a photocurable resin, ethoxylated trimethylpropane (ETPTA), iron oxide nanoparticles (hematite; <50 nm diameter) and silica particles (330 nm diameter). Under a magnetic field, the magnetic hematite particles became aligned parallel to the field and migrated to one side of the emulsion droplet, while the hydrophilic silica particles organized themselves at the ETPTA–water interface to form a two-dimensional arrangement. Photopolymerization of the ETPTA then gave the Janus particles, which had a net magnetic moment and arrays of silica ‘nanodomes’ on their
The Janus particles could be aligned by applying a magnetic field, which caused the magnetic hemispheres of the particles to realign toward the field. By rotating the field, the researchers could control both the rotation and position of the particles on a planar substrate. The type of motion was determined by the relative position of the axis of magnet rotation: if the axis was in the plane of the substrate, the particles moved around by a rolling motion, whereas if the axis was perpendicular to the substrate, the particles rotated around the same axis in the opposite direction.