(98ab) Producing Stable Nanoparticle Dispersions With Microfluidic Devices

In this study, we experimentally examined the effectiveness of applying conventional microfluidic devices to enhance dispersion stability of nanoparticles in liquid phase.  Regularly, homogenizer and sonication bath are widely used to disperse nanoparticle powders in liquids by breaking large particles into small ones with vibrational energy.  In the literature, similar breakage of particle-particle aggregates can also be accomplished by introducing large shear rate in microfluidic channels with obstructions.  Following this idea, a microfluidic device able to provide large shear rates for particle disintegration was fabricated from plolydimethylsiloxane (PDMS) using soft lithography method.  Rectangular and circular obstructions were placed inside the channel to introduce large transverse velocity components and shear rates to tear particle aggregates apart.  Computational fluid mechanical models from commercial software were also used to calculate the shear stress along microchannels with optimum obstruction patterns.  The inlet fluid stream containing nanoparticle aggregates (~ um) were driven into the channels by a high pressure syringe pump.  The outlet stream fluids were collected for particle size analysis.  After the microfluidic treatment, the particle sizes were found to be greatly reduced and thus the dispersion stability was enhanced.