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  • LED Induced Fluorescence using microscale visualization

    methods

    Jorge Andr Garcia Arromba

    Thesis to obtain the Master of Science Degree in

    Mechanical Engineering

    Supervisor: Prof. Antnio Lus Nobre Moreira

    Examination Committee

    Chairperson: Prof. Viriato Srgio de Almeida Semio

    Supervisor: Prof. Antnio Lus Nobre Moreira

    Member of the Committee: Prof. Jos Maria Campos da Silva Andr

    October 2014

  • i

  • ii

    Acknowledgements

    First of all, I would like to thank my supervisor Professor Lus Moreira for the opportunity of working

    with him and his availability, patience and guidance throughout the elaboration of this work.

    Financial support through project PTDC/EME-MFE/109933/2009 from Fundao para a Cincia e a

    Tecnologia, FCT, is gratefully acknowledged. Laboratory facilities were built in the framework of project

    RECI/EMS-SIS/0147/2012 and therefore also acknowledged.

    I would like to express my gratitude towards Vnia Silvrio, for all the help, discussions, guidance,

    lectures and laughs. Your support was essential for the outcome of this work, and thank you for

    believing in me and for the encouragement until the very end.

    To all my closest friends, and to my fellow colleagues in the Laboratory, for the support, fellowship and

    understanding that helped me to go through this 6 months and take this to a conclusion, thank you.

    At last, but not at least, I thank all the unconditional love and support from my family. To my brother,

    my parents, I am infinitely grateful to you. Love you all.

  • iii

  • iv

    Resumo

    Este trabalho consiste na optimizao e aplicao de duas tcnicas de fluorescncia, utilizando um ou

    dois corantes, para medio no intrusiva da temperatura em escoamento microescala. Foram

    efetuadas medies num sistema microfludico, iluminado em volume com uma fonte de luz LED, a

    partir das quais se definiram e otimizaram os parmetros que determinam a preciso do mtodo.

    Posteriormente a tcnica foi aplicada a dois casos de teste, ao escoamento num microcanal de

    paredes aquecidas e a uma mistura trmica de dois escoamentos numa zona de mistura em T.

    Foram utilizados dois corantes, Rodamina B e Rodamina 110, uma vez que a intensidade de

    fluorescncia emitida por cada um deles varia de forma diferente com a temperatura. Enquanto o sinal

    da Rodamina B apresenta uma dependncia acentuada da temperatura, o da Rodamina 110

    aproximadamente independente (sensibilidade < 0.011 %. 1). A tcnica de um corante (RhB)

    apresentou-se mais vantajosa, com sensibilidade de 1.68 %. 1, sendo posteriormente aplicada ao

    caso prtico num microcanal, onde foi encontrada concordncia na variao de temperatura medida

    atravs de um termopar na sua parede. Os erros associados medio do sinal de intensidade de

    fluorescncia so inferiores a 3.8% enquanto os associados s medidas de temperatura so inferiores a

    0.71%.

    Medidas das distribuies bidimensionais de temperatura no escoamento de solues aquosas de

    corantes com corantes em concentraes residuais num canal de dimenses micromtricas

    comprovaram a capacidade da tcnica ser aplicada com a fonte de iluminao LED e com elevadas

    resolues espacial (1.54 ) e temporal (~5 ).

    Palavras-chave: Tcnica de Fluorescncia, Iluminao LED, Medio temperatura escoamento,

    Microfluidos, Perfis de temperatura 2D.

  • v

    Abstract

    A non-intrusive LED Induced Fluorescence Thermometry measurement technique is developed and

    applied using microscale visualization techniques. Whole field temperature measurements in a

    volume-illuminated microfluidic setup were performed with a good spatial and temporal resolutions,

    being applied to practical that serve as training benchmark tests, often imposed to CPU chips, and to

    the thermal mixing of two fluid streams in a T-shaped micro-mixer.

    Two different techniques are addressed: Normalized Induced Fluorescence Thermometry (N-LED-IFT)

    and Normalized Ratiometric Induced Fluorescence Thermometry (NR-LED-IFT), using one and two

    dyes, respectively. Parameters influencing the results and the feasibility of these techniques at the

    microscale using a Leica illumination system LED SFL100 530 were also addressed.

    Rhodamine B and Rhodamine 110 are used as temperature sensitive and insensitive dyes, respectively.

    The single-dye technique (N-LED-IFT) proved most advantageous, obtaining a sensitivity of

    1.68 %. 1. This technique was then used for training benchmark testing, where good agreement with

    temperature variations on wall temperature measured using a thermocouple was found. The N-LED-IFT

    results present errors lower than 3.8 % in fluorescence intensity and lower than 0.71 % in temperature

    measurements. Radial and longitudinal temperature profiles in the microchannel were also observed.

    The capability of this technique to be applied to low and high velocity microscale flows using a LED

    illumination source was proved and 2D fluid temperature profiles where obtained with high spatial

    (1.54 ) and temporal (~ 5 ) resolutions.

    Keywords: LED Induced Fluorescence Thermometry, LED illumination, Flow temperature measurement,

    Microfluidics, 2D fluid temperature profiles.

  • vi

    Nomenclature

    Cross section area [2]

    12 External area between sections 1 and 2

    [2]

    Number of bits

    C Dye concentration in the solution [/3]

    Specific heat of the fluid [. 1. 1]

    Hydraulic diameter []

    Light fraction []

    Heat transfer coefficient [. 1. 2]

    Fluorescent intensity emitted per unit of

    volume [. . ]

    0 Light incident flux [/2]

    Percentage of energy loss from the

    resistance directly to environment []

    Hydrodynamic entrance length []

    Thermal entrance length []

    Mass flow [. 1]

    Perimeter []

    Output electrical power from power

    generator []

    Particles A Temperature dependent dye

    particles

    Particles B Temperature independent dye

    particles

    Prandtl number []

    Volumetric flow [. 1]

    Heat flux [. 2]

    12 Net heat flux dissipated from section 1

    to section 2 [. 2]

    Reynolds number []

    SNR Signal-to-Noise Ratio [dB]

    Temperature [ ]

    Flow velocity, eq. 22 and 23 [. 1]

    Voltage []

    Signal output from camera []

    Solution volume, Equation 24 [3]

    Greek symbols

    C Collection efficiency

    Temperature difference [ ]

    Absorption coefficient [2/]

    Microchannel characteristic dimension []

    0 Wavelength of light in vacuum []

    Mean intensity of the image set [. . ]

    Fluid kinematic velocity [2. 1]

    Fluid density [. 3]

    Standard deviation of the image set,

    Equation 16 [. . ]

    Quantum yield []

  • vii

    Acronyms

    CCD Charge Coupled Device

    CPU Central Processing Unit

    DOF Depth Of Field

    FRET Fluorescent Resonance Energy Transfer

    FS Fluorescence Signal

    IC Integrated Circuits

    LaVision HSS LaVision HighSpeedStar high

    speed imaging camera

    LED Light emitting diode

    LED-IFT LED Induced Fluorescence

    Thermometry

    LIF Laser Induced Fluorescence

    NA Numerical Aperture

    N-LIFT Normalized Laser Induced

    Fluorescence Thermometry

    N-LED-IFT Normalized LED Induced

    Fluorescence Thermometry

    NR-LIFT Normalized Ratiometric Laser

    Induced Fluorescence Thermometry

    NR-LED-IFT Normalized Ratiometric LED

    Induced Fluorescence Thermometry

    Phantom Vision Research Phantom v4.0 high

    speed imaging camera

    RhB Rhodamine B, temperature dependent

    dye

    Rh110 Rhodamine 110, temperature

    independent dye

    TLCs Thermochromic Liquid Crystals

    VLSI Very Large Scale Integration systems

    Subscripts

    Related to Particles A

    Related to Particles B

    Inner dimension

    Outer dimension

    Superscripts

    Image that captures particles A

    fluorescence emission

    Image that captures particles B

    fluorescence emission

  • viii

    Table of Contents

    Acknowledgements ....................................................................................................................................................................... ii

    Resumo ............................................................................................................................................................................................. iv

    Abstract .............................................................................................................................................................................................. v

    Nomenclature ................................................................................................................................................................................. vi

    List of Tables ................................................................................................................................................................................... ix

    List of Figures .................................................................................................................................................................................. x

    1. Introduction ..................................