Magnetic actuation, heat transfer and microsystem applications of iron-oxide nanoparticle based ferrofluids

Ferrofluids are colloidal suspensions, in which the solid phase material is composed of magnetic nanoparticles, while the base fluid can potentially be any fluid. The solid particles are held in suspension by weak intermolecular forces and may be made of materials with different magnetic properties. Magnetite is one of the materials used for its natural ferromagnetic properties. They have vital applications in the field of microfluidics such as microscale flow control in microfluidic circuits, actuation of fluids in microscale, and drug delivery mechanisms. Heat transfer performance of such ferrofluids is also one of the crucial properties among many potential coolants that should be analyzed and considered for their wide range of applications. In the first study, different families of devices actuating ferrofluids were designed and developed to reveal this potential. A family of these devices actuates discrete plugs, whereas a second family of devices generates continuous flows in tubes of inner diameter ranging from 254μm to 1.56mm. The devices were first tested with minitubes to prove the effectiveness of the proposed actuation method. The setups were then adjusted to conduct experiments on microtubes. Promising results were obtained from the experiments. Flow rates up to 120μl/s and 0.135μl/s were achieved in minitubes and microtubes with modest maximum magnetic field magnitudes of 300mT for discontinuous and continuous actuation, respectively. The proposed magnetic actuation method was proven to work as intended and is expected to be a strong alternative to the existing micropumping methods such as electromechanical, electrokinetic, and piezoelectric actuation. The results suggest that ferrofluids with magnetic nanoparticles merit more research efforts in micro pumping. In the second study, convective heat transfer experiments were conducted in order to characterize convective heat transfer enhancements with Lauric acid coated ironoxide (Fe3O4) nanoparticle based ferrofluids, which have volumetric fractions between 0%- ~5% and average particle diameter of 25 nm, in a 2.5 cm long hypodermic stainless steel microtube with an inner diameter of 514 μm and an outer diameter of 819 μm. Heat fluxes up to 184 W/cm2 were applied to the system at three different flow rates (1ml/s, 0.62ml/s and 0.36 ml/s). A decrease of around 100% in the maximum surface temperature (measured at the exit of the microtube) with the ferrofluid compared to the pure base fluid at significant heat fluxes (>100 W/cm2) was observed. Moreover, the enhancement in heat transfer increased with nanoparticle concentration, and there was no clue for saturation in heat transfer coefficient profiles with increasing volume fraction over the volume fraction range in this study (0%-5%). The promising results obtained from the experiments suggest that the use of ferrofluids for heat transfer, drug delivery, and biological applications can be advantageous and a viable alternative as new generation coolants and futuristic drug carriers

An experimental study on heat transfer performance of iron oxide based ferrofluids

Nanofluids are colloidal compounds, where the solid phase material is composed of nano sized particles, and the liquid phase can potentially be any fluid but aqueous media are common. As a common nanofluid type, ferrofluids are formed by holding solid nanoparticles in suspension by weak intermolecular forces and may be produced from materials with different magnetic properties. Magnetite is one of the materials used for its natural ferromagnetic properties. Heat transfer performance of ferrofluids is one of the crucial properties among many others that should be analyzed and considered for their wide range of applications. For this purpose, experiments were conducted in order to characterize heat transfer properties of ironoxide based ferrofluids flowing through a microchannel. Promising results were obtained from this study, which are suggesting the use of ferrofluids for heat transfer applications can be advantageous

Simulation of magnetic actuation of ferrofluids in microtubes

Magnetic actuation of ferrofluids with dynamic magnetic fields is one of the most promising research areas with its wide and different potential application areas such as biomedical and micropumping applications. Ferrofluid has the potential of opening up new possibilities. To have more understanding about various fields of engineering, more research should be conducted by considering both the experimental and modeling aspects. The most important parameters determining the flow property, flow rates and overall system efficiency are the quality and the topology of magnetic fields used in these systems. Therefore, the methods of dynamic magnetic field generation constitute a central problem to obtain desired performance. This study includes modeling and simulation of ferrofluid actuation with dynamic magnetic fields by using the COMSOL software and reports that ferrofluid actuation can be successfully used and the simulation results agree well with the experimental results

Heat transfer enhancement with iron oxide nanoparticle based ferrofluids

Nanofluids are colloidal compounds, where the solid phase material is composed of nano sized particles, and the liquid phase can potentially be any fluid but aqueous media are common. As a common nanofluid type, ferrofluids are formed by holding solid nanoparticles in suspension by weak intermolecular forces and may be produced from materials with different magnetic properties. Heat transfer performance of ferrofluids is one of the crucial properties among many others that should be analyzed and considered for their wide range of applications. For this purpose, experiments were conducted in order to characterize heat transfer properties of ironoxide based ferrofluids flowing through a microchannel. In this study, convective heat transfer experiments were conducted in order to characterize convective heat transfer enhancements with Lauric acid coated ironoxide (Fe3O4) nanoparticle based ferrofluids, which have volumetric fractions between 0%–∼5% and average particle diameter of 25 nm, in a 2.5 cm long hypodermic stainless steel microtube with an inner diameter of 514 μm and an outer diameter of 819 μm. Heat fluxes up to 184 W/cm2 were applied to the system at three different flow rates (1ml/s, 0.62ml/s and 0.36 ml/s). Promising results were obtained from this study, which are suggesting the use of ferrofluids for heat transfer applications can be advantageous

Experimental study on heat transfer performance of iron oxide based ferrofluids to be used as new generation coolants and drug delivery agents

Ferrofluids are colloidal suspensions, in which the solid phase material is composed of magnetic nanoparticles, while the base fluid can potentially be any fluid. The solid particles are held in suspension by weak intermolecular forces and may be made of materials with different magnetic properties. Magnetite is one of the materials used for its natural ferromagnetic properties. Heat transfer performance of ferrofluids should be carefully analyzed and considered for their potential of their use in wide range of applications. In this study, convective heat transfer experiments were conducted in order to characterize convective heat transfer enhancements with Lauric acid coated ironoxide (Fe3O4) nanoparticle based ferrofluids, which have volumetric fractions varying from 0% to ~5% and average particle diameter of 25 nm, in a hypodermic stainless steel microtube with an inner diameter of 514 Hm, an outer diameter of 819 Hm, and a heated length of 2.5 cm. Heat fluxes up to 184 W/cm2 were applied to the system at three different flow rates (1ml/s, 0.62ml/s and 0.36 ml/s). A decrease of around 100% in the maximum surface temperature (measured at the exit of the microtube) with the ferrofluid compared to the pure base fluid at significant heat fluxes (>100 W/cm2) was observed. Moreover, the enhancement in heat transfer increased with nanoparticle concentration, and there was no clue for saturation in heat transfer coefficient profiles with increasing volume fraction over the volume fraction range in this study (0%-5%). The promising results obtained from the experiments suggest that the use of ferrofluids for heat transfer, drug delivery, and biological applications can be advantageous and a viable alternative as new generation coolants and futuristic drug carriers