Magnetic particles that can be remotely manipulated by an external magnetic field have attracted considerable interests for applications, including bioimaging, biosensing, multiplexed detection, and separation, transport, and sorting in microfluidic devices. While most studies have focused on spherical magnetic particles, it has been reported that magneto- and electro-rheological properties can be enhanced using anisotropic particles. Here, we report a facile and versatile method to fabricate monodispersed hybrid and Janus microrod particles of variable size and shape, and investigate their magneto-responsive behaviors in aqueous dispersions with and without geometric confinement. The key feature of our method involves co-assembly of silica colloidal particles and magnetic iron oxide nanoparticles in a poly(dimethylsiloxane) (PDMS) mold with a periodic micron-sized hole array, followed by infiltration and UV curing of epoxy resin to lock the particles, and releasing the microstructures from the mold and the substrate. The synthesized magnetic microrod particles were highly responsive: they could be isolated and flipped freely and reversibly. Further, our fabrication strategy allowed for creation of diblock and triblock-like Janus particles, where magneto-responsiveness and fluorescent emission could be integrated into different blocks within a single rod particle. Specifically, the use of silica particles in one of the blocks is advantageous since different functionality, surface chemistry, and fluorescent dyes can be introduced in addition in sequestering magnetic nanoparticle. Using these particles, we demonstrated field-responsive displays of multiple colors.

Synthesis of magneto-responsive, hybrid, and Janus microrod particles

248th National Meeting (2014)

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