ELECTROCHEMICALLY ACTUATED CAPILLARY FLOW - tdx.cat

124 Pages·2013·3.08 MB·English

by  Alemayehu Paulos

ELECTROCHEMICALLY ACTUATED CAPILLARY FLOW CONTROL FOR
THE DEVELOPMENT OF INTEGRATED MICROFLUIDIC DEVICES

Alemayehu Paulos Washe

Dipòsit Legal: T. 475-2013

ADVERTIMENT. L'accés als continguts d'aquesta tesi doctoral i la seva utilització ha de respectar els drets
de la persona autora. Pot ser utilitzada per a consulta o estudi personal, així com en activitats o materials
d'investigació i docència en els termes establerts a l'art. 32 del Text Refós de la Llei de Propietat Intel·lectual
(RDL 1/1996). Per altres utilitzacions es requereix l'autorització prèvia i expressa de la persona autora. En
qualsevol cas, en la utilització dels seus continguts caldrà indicar de forma clara el nom i cognoms de la
persona autora i el títol de la tesi doctoral. No s'autoritza la seva reproducció o altres formes d'explotació
efectuades amb finalitats de lucre ni la seva comunicació pública des d'un lloc aliè al servei TDX. Tampoc
s'autoritza la presentació del seu contingut en una finestra o marc aliè a TDX (framing). Aquesta reserva de
drets afecta tant als continguts de la tesi com als seus resums i índexs.

ADVERTENCIA. El acceso a los contenidos de esta tesis doctoral y su utilización debe respetar los
derechos de la persona autora. Puede ser utilizada para consulta o estudio personal, así como en
actividades o materiales de investigación y docencia en los términos establecidos en el art. 32 del Texto
Refundido de la Ley de Propiedad Intelectual (RDL 1/1996). Para otros usos se requiere la autorización
previa y expresa de la persona autora. En cualquier caso, en la utilización de sus contenidos se deberá
indicar de forma clara el nombre y apellidos de la persona autora y el título de la tesis doctoral. No se
autoriza su reproducción u otras formas de explotación efectuadas con fines lucrativos ni su comunicación
pública desde un sitio ajeno al servicio TDR. Tampoco se autoriza la presentación de su contenido en una
ventana o marco ajeno a TDR (framing). Esta reserva de derechos afecta tanto al contenido de la tesis como
a sus resúmenes e índices.

WARNING. Access to the contents of this doctoral thesis and its use must respect the rights of the author. It
can be used for reference or private study, as well as research and learning activities or materials in the
terms established by the 32nd article of the Spanish Consolidated Copyright Act (RDL 1/1996). Express and
previous authorization of the author is required for any other uses. In any case, when using its content, full
name of the author and title of the thesis must be clearly indicated. Reproduction or other forms of for profit
use or public communication from outside TDX service is not allowed. Presentation of its content in a window
or frame external to TDX (framing) is not authorized either. These rights affect both the content of the thesis
and its abstracts and indexes.
UNIVERSITAT ROVIRA I VIRGILI
ELECTROCHEMICALLY ACTUATED CAPILLARY FLOW CONTROL FOR THE DEVELOPMENT OF INTEGRATED MICROFLUIDIC DEVICES
Alemayehu Paulos Washe
Dipòsit Legal: T. 475-2013

Doctoral Thesis

Alemayehu Paulos Washe

ELECTROCHEMICALLY ACTUATED CAPILLARY FLOW CONTROL
FOR THE DEVELOPMENT OF
INTEGRATED MICROFLUIDIC DEVICES

Universitat Rovira i Virgili

Department of Chemical Engineering

Tarragona, 2013

1
UNIVERSITAT ROVIRA I VIRGILI
ELECTROCHEMICALLY ACTUATED CAPILLARY FLOW CONTROL FOR THE DEVELOPMENT OF INTEGRATED MICROFLUIDIC DEVICES
Alemayehu Paulos Washe
Dipòsit Legal: T. 475-2013

2
UNIVERSITAT ROVIRA I VIRGILI
ELECTROCHEMICALLY ACTUATED CAPILLARY FLOW CONTROL FOR THE DEVELOPMENT OF INTEGRATED MICROFLUIDIC DEVICES
Alemayehu Paulos Washe
Dipòsit Legal: T. 475-2013

Alemayehu Paulos Washe

ELECTROCHEMICALLY ACTUATED CAPILLARY FLOW CONTROL
FOR THE DEVELOPMENT OF
INTEGRATED MICROFLUIDIC DEVICES

Doctoral Thesis

Supervised by:

Dr. Ioanis Katakis
Dr. Pablo Lozano-Sanchez

Department of Chemical Engineering

Universitat Rovira I Virgili

Tarragona

2013

3
UNIVERSITAT ROVIRA I VIRGILI
ELECTROCHEMICALLY ACTUATED CAPILLARY FLOW CONTROL FOR THE DEVELOPMENT OF INTEGRATED MICROFLUIDIC DEVICES
Alemayehu Paulos Washe
Dipòsit Legal: T. 475-2013

4
UNIVERSITAT ROVIRA I VIRGILI
ELECTROCHEMICALLY ACTUATED CAPILLARY FLOW CONTROL FOR THE DEVELOPMENT OF INTEGRATED MICROFLUIDIC DEVICES
Alemayehu Paulos Washe
Dipòsit Legal: T. 475-2013

5
UNIVERSITAT ROVIRA I VIRGILI
ELECTROCHEMICALLY ACTUATED CAPILLARY FLOW CONTROL FOR THE DEVELOPMENT OF INTEGRATED MICROFLUIDIC DEVICES
Alemayehu Paulos Washe
Dipòsit Legal: T. 475-2013

To my family
Jada, Juliet & Bezuayehu

6
UNIVERSITAT ROVIRA I VIRGILI
ELECTROCHEMICALLY ACTUATED CAPILLARY FLOW CONTROL FOR THE DEVELOPMENT OF INTEGRATED MICROFLUIDIC DEVICES
Alemayehu Paulos Washe
Dipòsit Legal: T. 475-2013

ACKNOWLEDGEMENT
It gives me great pleasure to express my sincere gratitude to my PhD supervisor Dr. Ioanis Katakis who
accepted me and trusted me for the great scientific intent to be realized. It was great opportunity for me to
work with Dr. Katakis. He guided me properly and encouraged me to exercise the scientific attitude freely
that gave me the opportunity to develop confidence for independent thinking-Many thanks! I am also
grateful to my co-supervisor Dr Pablo Lozano who encouraged me and helped me during the PhD.

I would like to thank Dr. Ciara O' Sullivan for kind guidance during my incorporation into the BBG group
and also for recommending me for a PhD student position under Dr. Katakis. I am also grateful to Professor
F. Xavier Rius for unreserved guidance and training during my Master studies and initial periods of the
PhD. I am grateful to Dr. Santiago Macho and Dr. Enrique J. Parra for kind collaborations and friendly
atmosphere in Tarragona and URV. My appreciation and thanks to all current and previous members of the
INTERFIBIO group including Dr. Bruno Dias, Dr. Mayreli Ortiz, Dr. Angel González, Dr. Valerio Beni,
Dr. Alex Fragoso, Dr. Teresa Mairal for friendly approaches and collaborations. I am thankful to Mr. Diego
Bejarano-Nosas who helped me a lot with my activities in Lab 214. I thank Dr. Olivier Henry for helping
me with the video set ups for my experiments. I would like to thank Dr. Sergio Martínez Montequín for
training on screen-printing during initial periods of the PhD. I have special thanks to my lab-mates Mabel
Torrens and Ewelina Wajs and of course our colleague Oumaya Msehli for collaborations and friendly
atmosphere in Lab214. I would like to extend my appreciation to Dr. Mayreli Ortiz and Mabel Torrens for
showing responsibility from their own initiation and taking time to correct my Spanish on the “Resumen”
section-lots of thanks!!!

I would like to acknowledge the University of Rovira I Virgili (URV), and the Autonomous Government of
Catalunya for BRDI and FIDGR doctoral fellowships respectively. The Dilla University, my home
University in Ethiopia, is also acknowledged for granting me study leave permission and providing
financial support to my family during this PhD. I am thankful to Ms. Barbara Vastenavond and Ms. Sira
Durán for assistance in the administrative works.

My deepest gratitude and appreciation goes to my family, my daughters (Jada Alemayehu and Juliet
Alemayehu) and to my wife Bezuayehu Assefa, who showed relentless patience and endurance taking care
of the kids and encouraging me to concentrate of my study. I would like to thank also Ato Harkiso Haile
and my mother W/ro Ferenj Abebe for encouragements.

7
UNIVERSITAT ROVIRA I VIRGILI
ELECTROCHEMICALLY ACTUATED CAPILLARY FLOW CONTROL FOR THE DEVELOPMENT OF INTEGRATED MICROFLUIDIC DEVICES
Alemayehu Paulos Washe
Dipòsit Legal: T. 475-2013

Summary
Microfluidics may be defined as the study of the behavior, and manipulation of very small volume
of fluid in microchannels of dimensions 10s to 100s of micrometers. Microfluidics offers very
fascinating features with some interesting challenges to overcome in the device development. In
addition to the improved analytical performance related to the high surface area-to-volume ratio
resulting from miniaturization, the ability to perform analysis on a very small volume of samples
with economy of reagents and time makes microfluidics cost effective solution to the realization
of current needs for ASSURED (a term introduced by A. Guiseppi-Elie: Affordable, Sensitive,
Specific, User-friendly, Rapid and robust, Equipment-free and Deliverable) devices for distributed
diagnostics and home-health care (D H ) applications.
2 2

A good example of diagnostic devices that can be considered as a starting point for the
development of ASSURED microfluidic devices are Lateral flow Devices (LFDs). Because LFDs
have been successfully commercialized and used in point-of-care (POC) diagnostics. They owe
their success to their simplicity that significantly depends on the capillary-driven flow and
versatile technological platform that lends itself to fast and low cost product development.
However, these devices are often limited to screening applications. They are not sensitive enough
for certain applications that require highly sensitive and quantitative analysis such as that of
allergies. Microfluidic devices, particularly capillary driven microfluidic devices, are expected to
outperform LFDs and overcome their limitation if flow rate is precisely controlled in
microchannels given current state of the art in microfabrication techniques.

In this thesis the design, fabrication and implementation of three different electrochemically
actuated capillary flow control schemes have been developed through low voltage electrowetting/
electrochemical actuation of the flow using i) electrical stimuli responsive superhydrophobic
surfaces based on intelligent polymers ii) superhydrophobic nanoporous carbonaceous surfaces,
and iii) superhydrophobic electrodes coupled to other electrodes that facilitate the generation of
gradients to propel the liquid. The developed schemes are expected to facilitate the realization of
ASSURED devices for bioanalytical applications where an analytical response depends on the
dissolution of previously deposited reagents, the kinetics of biological affinity and enzymatic
reactions, and mass transport of products to a transducer in the microchannels. The thesis unravels
the mechanism of response of such systems and demonstrates ways for reduction to practice of
such devices for the “democratization” of theranostics.
8
UNIVERSITAT ROVIRA I VIRGILI
ELECTROCHEMICALLY ACTUATED CAPILLARY FLOW CONTROL FOR THE DEVELOPMENT OF INTEGRATED MICROFLUIDIC DEVICES
Alemayehu Paulos Washe
Dipòsit Legal: T. 475-2013

The valving configuration in all the three schemes involves a pair of screen printed electrodes
(SPEs) transversal to the flow. One of the electrodes in each pair is superhydrophobic to provide
passive stopping and facilitate low-voltage actuation of the flow by virtue of: electrically tunable
wettability based on intelligent polymers, low voltage electrowetting transition from the less
wetted Cassie to more wetted Wenzel or on-chip generated concentration gradient.

In the first scheme the fabrication of polymer based superhydrophobic surface by
electropolymerization required pretreatment of screen printed carbon electrodes (SPCEs) to
amplify the roughness and enhance electrochemical performance. The activation as well as
roughness amplification strategy was controlled to avoid nucleophilic functionalities on the
surface of the electrodes. Such functionalities as hydroxyl groups can render nucleophilic attack to
the growing polymeric chain or reactive intermediates during the electropolymerization and
destroy the conjugation- the key requirement for the expected electrically tunable property of the
polymer. In this work we achieved this by a new procedure that involves controlled and selective
subtraction of nonelectroactive components from the electrode’s surface based on solubility
principles. The selective subtraction enhances surface roughness and also activates the electrodes
for electropolymerization by increasing graphitic loading and exposure (electrochemical
accessibility) of the graphitic edges with electrocatalytic property. Electrodeposition of the
polymer was then performed on the previously roughened and activated SPCE surface through
controlled cycling of potential to produce poly(3-methylthiophene) based superhydrophobic
surface that displays passive stopping of capillary flow and facilitate low voltage actuation of the
flow.

The second approach boasts simplicity and is based on the favorable wettability transition from
the less stable Cassie-Baxter wettability regime of superhydrophobic nanoporous electrode with
no further modification to a more stable and more wettable Wenzel regime by electrowetting. By
virtue of superhydrophobicity the electrode stops the flow and by virtue of the high conductivity,
large potential window and intrinsic charge accumulation capacity of carbonaceous material it
facilitates the low voltage actuation through electrowetting transitions at extremely low voltage. In
this case both electrodes involved in the valving operation are based on screen printed carbon-one
wettable and the other superhydrophobic nanoporous in each stop/go valving electrode pair.

The third scheme also exploits the superhydrophobic nanoporous carbon electrode but couples
it to screen printed silver. The superhydrophobic electrode as usual provides passive stopping of
9