UBC Theses and Dissertations
Investigation and development of ferrofluid enabled micro-electro-mechanical systems Assadsangabi, Babak
Ferrofluids are magnetic fluids that can be manipulated using magnetic field. Ferrofluids have unique properties that have led to various interesting applications. Although, currently they are being used in few commercial products in macro-scale domain, there has been limited success in their applications in micro- devices and microactuators in specific. Literature review shows various efforts to develop ferrofluid-based microactuators however, most of them have utilized non-integrated means (e.g. external magnets or solenoids) to provide the necessary magnetic field for ferrofluid manipulation that inherently limit their application as a micro-device. Moreover, previous ferrofluid-based microactuators with integrated solutions (e. g. microfabricated coils) could only provide unidirectional forces which limited their application range. In the present thesis, development of integrated ferrofluid-based microactuators is investigated. A new actuation method that uses planar spiral coils with bias fields is proposed to enable bidirectional ferrofluid manipulation. To demonstrate the potentials of the proposed actuation method, two proof-of-concept devices were developed. Active mirror cells with variable reflectivity were demonstrated as the first device and then a variable planar inductor with ferrofluid as a moving magnetic core was developed and characterized. Another interesting application of ferrofluids in passive levitation of permanent magnets is also investigated for moving magnet based microactuators. Using this levitation mechanism a structurally simple and reliable microbearing is demonstrated. In order to demonstrate the effectiveness of such microbearing, a linear micromotor is first characterized and demonstrated. Also, frictional force and load carrying capacity of such microbearing is investigated showing very low frictional forces with good load bearing capabilities. Given the promising results in the developed linear micromotor, a rotary micromotor with small axial size is developed for minimally invasive endoscopy applications. The characterization of developed prototype shows its potential to be used for real time medical imaging.
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