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  • Small angle light scattering apparatus for analysisof single micrometric particles in microfluidic flows

    David Dannhauser

    AdvisorPaolo A. Netti

    Federico II University of Naples

  • Small angle light scattering apparatus for analysis ofsingle micrometric particles in microfluidic flows

    A thesis submitted in partial fulfilment of the requirementfor the degree of Doctor of Philosophy in

    Materials and Structures Engineering

    AuthorDavid Dannhauser

    CoordinatorProfessor Giuseppe Mensitieri

    TutorFilippo Causa

    AdvisorProfessor Paolo A. Netti

    Universit degli studi di Napoli Federico II

    Facolt di Ingegneria

    Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione In-dustriale D.I.C.MA.P.I

    2. April 2013

    I

  • II

  • Affidavit

    I hereby declare by oath that I have written this paper myself. Any ideasand concepts taken from other sources either directly or indirectly have beenreferred to as such. The paper has neither in the same nor similar form beenhanded in to an examination board, nor has it been published.

    Place, Date Signature

    III

  • IV

  • Table of Contents

    1 INTRODUCTION 1

    2 THEORY of LIGHT SCATTERING 52.1 Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.2 Scattering by small particles . . . . . . . . . . . . . . . . . . . 62.3 Rayleigh theory . . . . . . . . . . . . . . . . . . . . . . . . . . 92.4 Lorenz-Mie theory . . . . . . . . . . . . . . . . . . . . . . . . 112.5 Fraunhofer diffraction . . . . . . . . . . . . . . . . . . . . . . 14

    3 EXPERIMENTAL SETUP 173.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173.2 Optical focusing & collimation . . . . . . . . . . . . . . . . . 19

    3.2.1 Incident beam . . . . . . . . . . . . . . . . . . . . . . . 193.2.2 Optical focusing . . . . . . . . . . . . . . . . . . . . . 203.2.3 Collimation . . . . . . . . . . . . . . . . . . . . . . . . 22

    3.3 Sample device . . . . . . . . . . . . . . . . . . . . . . . . . . . 253.3.1 Quiescent - device . . . . . . . . . . . . . . . . . . . . 253.3.2 In-flow - device . . . . . . . . . . . . . . . . . . . . . . 253.3.3 Temperature control module . . . . . . . . . . . . . . . 28

    3.4 Detection system . . . . . . . . . . . . . . . . . . . . . . . . . 293.4.1 Lens position . . . . . . . . . . . . . . . . . . . . . . . 303.4.2 Beam stop . . . . . . . . . . . . . . . . . . . . . . . . . 333.4.3 Mapping & detector . . . . . . . . . . . . . . . . . . . 36

    4 ACQUISITION and DATA PROCESSING 394.1 Sample preparation & acquisition . . . . . . . . . . . . . . . . 394.2 Data processing . . . . . . . . . . . . . . . . . . . . . . . . . . 41

    4.2.1 Data selection . . . . . . . . . . . . . . . . . . . . . . . 414.2.2 Data analysis . . . . . . . . . . . . . . . . . . . . . . . 43

    4.3 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

    5 RESULTS 535.1 Quiescent measurements . . . . . . . . . . . . . . . . . . . . . 535.2 In-flow measurements . . . . . . . . . . . . . . . . . . . . . . 63

    V

  • 5.3 SEM measurements . . . . . . . . . . . . . . . . . . . . . . . . 755.4 Microgel measurements . . . . . . . . . . . . . . . . . . . . . . 76

    6 FUTURE ASPECTS 796.1 Wavelength change . . . . . . . . . . . . . . . . . . . . . . . . 796.2 Fluorescence implementation . . . . . . . . . . . . . . . . . . 806.3 Index of refraction change . . . . . . . . . . . . . . . . . . . . 816.4 Polarization implementation . . . . . . . . . . . . . . . . . . . 82

    7 CONCLUSION 85

    A Equipment 97

    B Manuscript - Optical Metrology - Munich 16-5-2013 99

    C Matlab code 111C.1 Spot size calculation . . . . . . . . . . . . . . . . . . . . . . . 111C.2 Analysis software . . . . . . . . . . . . . . . . . . . . . . . . . 111

    VI

  • List of Figures

    2.1 Scattering of incident light by a particle . . . . . . . . . . . . 62.2 General scattering geometry . . . . . . . . . . . . . . . . . . . 72.3 Scattering theories . . . . . . . . . . . . . . . . . . . . . . . . 82.4 Schematic scattering profile of a dipole . . . . . . . . . . . . . 102.5 Polar plot of a scattering profile with the Lorenz-Mie theory . 142.6 Diffraction pattern in 3D . . . . . . . . . . . . . . . . . . . . . 152.7 Diffraction pattern of a pinhole with radius 5 m . . . . . . . 16

    3.1 Schematic overview of experimental setup . . . . . . . . . . . 183.2 Schematic overview of incident beam . . . . . . . . . . . . . . 193.3 Schematic overview of optical focusing and collimation . . . . 213.4 Picture of a glass ball showing the collimation of incident light 233.5 Picture of bound GRIN lens . . . . . . . . . . . . . . . . . . . 233.6 Gaussian beam profile after lens L4 . . . . . . . . . . . . . . . 243.7 3D view of the microfluidic device . . . . . . . . . . . . . . . . 273.8 Peltier device . . . . . . . . . . . . . . . . . . . . . . . . . . . 293.9 Schematic overview of scattering pattern detection system . . 303.10 Schematic figure of a plano-convex lens . . . . . . . . . . . . . 323.11 Schematic overview of beam stop . . . . . . . . . . . . . . . . 343.12 Picture of beam stop . . . . . . . . . . . . . . . . . . . . . . . 35

    4.1 Schematic figure of averaging raw data stack . . . . . . . . . . 414.2 Graphical subtraction of background . . . . . . . . . . . . . . 424.3 Background subtraction for a PSL 4 particle . . . . . . . . . . 434.4 Masks for wave-vector calculation . . . . . . . . . . . . . . . . 444.5 Mask of rings over scattering pattern . . . . . . . . . . . . . . 454.6 Wave-vector plus theory for one particle . . . . . . . . . . . . 464.7 Screen-shot of Matlab routine - Auswertungssoftware . . . . . 474.8 Schematic overview of parts important for calibration . . . . . 484.9 Pinhole with radius 5 m plus theory . . . . . . . . . . . . . . 494.10 Pinhole with radius 10 m plus theory . . . . . . . . . . . . . 504.11 Screen-shot of the fitting from a pinhole in Matlab . . . . . . 51

    5.1 PSL 8 particles measured in quiescent condition . . . . . . . . 54

    VII

  • 5.2 PSL 6 particles measured in quiescent condition . . . . . . . . 555.3 PSL 5 particles measured in quiescent condition . . . . . . . . 565.4 PSL 4 particles measured in quiescent condition . . . . . . . . 585.5 PSL 3 particles measured in quiescent condition . . . . . . . . 595.6 PSL 2 particles measured in quiescent condition . . . . . . . . 605.7 Nominal versus in quiescent measured radii . . . . . . . . . . 615.8 PSL quiescent measurements versus Lorenz-Mie theory . . . . 625.9 PSL 8 particles measured in-flow condition . . . . . . . . . . . 645.10 PSL 7 particles measured in-flow condition . . . . . . . . . . . 655.11 PSL 5 and PSL 7 particle in sample . . . . . . . . . . . . . . 665.12 PSL 6 particles measured in-flow condition . . . . . . . . . . . 675.13 PSL 5 particles measured in-flow condition . . . . . . . . . . . 685.14 PSL 4 particles measured in-flow condition . . . . . . . . . . . 695.15 PSL 3 particles measured in-flow condition . . . . . . . . . . . 705.16 PSL 2 particles measured in-flow condition . . . . . . . . . . . 715.17 Nominal versus in-flow measured radii . . . . . . . . . . . . . 725.18 PSL in-flow versus Lorenz-Mie theory . . . . . . . . . . . . . 735.19 SEM images of PSL particle . . . . . . . . . . . . . . . . . . . 755.20 PNIPAM microgel in four different sizes . . . . . . . . . . . . 765.21 PNIPAM microgel measured over time . . . . . . . . . . . . . 77

    6.1 PSL 2 particle with different incident wavelengths . . . . . . . 806.2 Influence of absorption for the scattering profile . . . . . . . . 816.3 PSL 6 particle with different index of refraction . . . . . . . . 826.4 Polarization dependence of scattered light . . . . . . . . . . . 83

    VIII

  • List of Tables

    3.1 Specifications of lens L5 & L6 . . . . . . . . . . . . . . . . . . 31

    4.1 Nominal radii from supplier . . . . . . . . . . . . . . . . . . . 39

    5.1 Nominal radii from supplier versus measured quiescent radii . 605.2 Nominal radii from supplier versus measured in-flow radii . . 725.3 Table of SEM results . . . . . . . . . . . . . . . . . . . . . . . 75

    A.1 Equipment of the SALS system Part 1 . . . . . . . . . . . . . 97A.2 Equipment of the SALS system Part 2 . . . . . . . . . . . . . 98

    IX

  • X

  • Acknowledgments

    I would like to express my deepest gratitude to all who have supported meduring this work.

    In particular I would like to thank Prof. Paolo A. Netti for allowing meto work in his working group.

    Without the great support of my wife Gaia, all of my research activitieswouldnt be possible, therefore I want to especially thank you.

    The encouragement, guidance and support, from my tutor Filippo Causaand Giovanni Romeo enabled me to develop an understanding of the sub-ject. Without there guidance writing this thesis would not have been such asatisfying and successful experience for me.

    The discussions and co-operations with all of my colleagues have contributedsubstantially to this work, particularly those of my working group, Maur-izio Ventre, Carlo Natale, Costantino Casale, Raffaele Vecchione, DanielaGuarnieri, Maria Iannone and Anna Aliberti.

    Finally, I would like to show my gratitude to my family and friends for theircontinuous and unconditional support of all my undertakings, scholastic orotherwise.

    XI

  • XII

  • Abstract

    The fast characterization of micrometric particle is becoming of increasingimportance. The measurement of shape and the index of refraction of aparticle allows very accurate characterization of the analysed material. ACCD-camera based small angle light scattering (SALS) apparatus has beendeveloped to char