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Microfluidics and Bio-MEMS for Next Generation Healthcare.

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Title:Microfluidics and Bio-MEMS for Next Generation Healthcare.
Authors:Rahman, M Arifur
Contributors:Electrical Engineering (department)
Date Issued:Aug 2018
Publisher:University of Hawaiʻi at Mānoa
Abstract:Microfluidics and bio-MEMS technology provide essential tools for next-generation healthcare,
in areas such as tissue engineering, disease diagnostics, and embryology. Tissue engineering
requires precise in vitro patterning and multilayer assembly of cells and biomaterial scaffolds, and
often requires mesoscale structures to be assembled with microscale resolution. A potential
method of micromanipulation for in vitro tissue constructs is microassembly by a system
employing untethered microrobots. Many microrobots should operate in parallel to increase the
throughput of such a bio-micromanipulation system. However, current microrobot systems lack
the independent actuation of many entities in parallel. In this dissertation, opto-thermocapillary
flow-addressed bubble (OFB) microrobots are studied, and the independent actuation of fifty OFB
microrobots in parallel is demonstrated. In addition, individual microrobots and groups of
microrobots were moved along linear, circular, and arbitrary 2D trajectories. The independent
addressing of many microrobots enables higher-throughput microassembly of micro-objects, and
cooperative manipulation using multiple microrobots. Demonstrations of manipulation with
numerous OFB microrobots include the transportation of microstructures using a pair or team of
microrobots, and the cooperative manipulation of multiple micro-objects. The OFB microrobot
system presented here represents an order of magnitude increase in the number of independently
actuated microrobots in parallel, as compared to other magnetically or electrostatically actuated
microrobots, and a factor of five increase as compared to previous demonstrations of OFB
microrobots.
Microfluidics provides precise positioning and manipulation of fluids contained in microscale
structures. Microfluidic techniques were used to precisely position room-temperature liquid metal
in microtubes, enabling tunable capacitors for the receive coil of a magnetic resonance imaging
(MRI) scanner. This liquid-metal-based flexible tunable capacitor functions as the tuning element
of the MRI receive coil. In this dissertation, four types of liquid-metal-based tunable capacitors
with a high tuning range are demonstrated. The capacitors are easily fabricated by placing a pair
of liquid-metal-filled tubes in contact with one another. Tunability is achieved by varying the
length of the liquid metal in one of the tubes using a mechanical pump. Four different structures
are demonstrated: parallel-tube, folded-tube, coil, and spiral capacitors. The highest measured
tuning ratio is 42:1, and the highest change in capacitance per unit length of the pumped liquid
metal is 0.07 pF.mm-1.
Microfabricated sensors and actuators for biomedical applications are known as biomicroelectromechanical
systems, or bio-MEMS. In this dissertation, a microfluidic bio-MEMS
device was designed and made to study embryo viability, which is critical for successful in vitro
fertilization (IVF) treatment. Conventional methods of embryo evaluation rely mostly on
subjective visual analysis of embryo morphological features. Here, two different approaches have
been studied for automating the morphological embryo grading and developing a quantitative
embryo evaluation process free from human subjective errors. In the first approach, the human
blastocyst microscope images were analyzed using image processing tools. Their growth dynamics
were studied leading to crucial viability information. In the second approach, the embryo was
positioned in between two electrodes inside a microfluidic bio-MEMS device, and their electrical
impedance was measured during their development. Experiments with Artemia cysts showed a
distinct pattern of impedance changes at three different stages of cyst development. The measured
impedance changes corresponded to physiological changes as the cyst developed. The change in
impedance during the first stage of development provided sufficient quantitative data to predict if
the cyst would hatch. This work shows the potential of impedance spectroscopy for developing a
non-invasive test to quantitatively determine the health of the embryos.
Description:Ph.D. Thesis. University of Hawaiʻi at Mānoa 2018.
URI:http://hdl.handle.net/10125/62402
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections: Ph.D. - Electrical Engineering


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