磁性流體在微流體晶片之混合與分離之研究

Abstract

The mixing and the separation of the ferrofluid in microfluidic chips were investigated in this thesis. Mixing processes of the ferrofluid in the presence of a permanent magnet (5mm*4mm*2mm, 1000 Gauss) are highly different from that of pure diffusion. The magnetic field re-distributes the ferrofluid and the mixing efficiencies vary with the positions of the magnet and the volumetric flow rates of the fluids. With the suitable setup of the magnet, the mixing efficiencies can reach more than 90% within one characterisitic width of the channel. The segmented flows are also studied by injecting two immiscible fluids (water and oil were used in the present study) into the microchannel, which can be applied for fluid control. The length of the segmented slugs can be controlled by modulating the flow rates of water and oil; the geometry of the microchannels also plays an important role during the formation of the slugs. The mixing and the separation were then combined on the PDMS microfluidic chips to perform a more complete function. By the suitable design of the microfluidic chips and the proper position of the magnet, mixing and separation of the ferrofluid in microfluidic chips can be performed in order.