Development of a Novel Semi-Active Micromixer
Date Issued
2006
Date
2006
Author(s)
Chang, Chih-Hsiang
DOI
zh-TW
Abstract
The purpose of this essay is to propose a novel micro-mixer. The structure of the proposed mixer is as simple as that of the traditional passive mixer. Furthermore, the working flow of this assay is a kind of controllable nano-magnetic fluids therefore it can be twisted or squeezed like a magnetic rod once an external magnetic field is applied. To combine the advantages mentioned above, instead of an active mixer, an external magnet is employed in our research. With the simple dragonfly type of micro-fluidic channel, the fluid can be formed as the droplet shape by this passive structure. The oil-based agent magnetic working fluid is magnetized to squeeze the droplets and enhance the mixing efficiency. This type of mixer is called a “Semi-Active Micromixer”.
First we focus on the refinement of the agent of nano-magnetic fluids. The results show that different experimental environments have effects on the characteristics of the fluid by using Taguchi method. Three controlled parameters, the way of pouring, the way of heating, and the modification of the Ammonium Oil acid are tested for the experiments. The optimal conditions are as follows. (1). Use Fe ionized solution to titrate the sodium hydroxide solution. (2). Stir the mixing fluid at 90 oC. (3). Adopt 5 mg: 5 mg as the proportion of oleic acid and ammonia. The magnetization is 0.96emu/g for optimal water-based magnetic fluids of 0.05M. The magnetization is 7.98emu/g, 6.56emu/g and 4.73emu/g for oil-based magnetic fluids of 0.5M, 0.25M, 0.125M respectively at the external magnetic filed of 13500 Oe. All the ferrofluids illustrates the characteristic of superparamagnety.
The MEMS process and soft lithography technique were employed to fabricate the micro-mixer device.The final results of the experiments focus on the mixing efficiency of the novel mixer. The oil-based magnetic fluid, transparent DI water and the blue dye are injected through the inlets respectively. The resultes show that: (1).The mixing uniformaity is more stable as closer to the end the microchannel when the same concentration of the magnetic fluid is applied. (2).The mixing is more uniform when stronger magnetic field is applied. (3).The mixed fluid is more uniform when the concerntration of the magnetic fluid is higher.
Subjects
田口參數設計
奈米磁性流體
混合器
微機電製程
微流體晶片
Taguchi method
Magnetic fluids
Mixer
MEMS process
Microfluidic chip.
Type
thesis