--        Electrical EngineeringDoctor of Philosophy 2016     ABSTRACT MICRO-LENS-COUPLED LED NEURAL STIMULATORS FOR OPTOGENETICS By Xiaopeng Bi -------------------  --    ACKNOWLEDGMENTS    -      TABLE OF CONTENTS     .....................................................................................................................    ..................................................................................................................    ........................................................................................................   ..........................................................................................................................  ...............................................................................................................  ....................................................................................   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LIST OF TABLES  -- ·································································   - ·       LIST OF FIGURES   ································    ··    ················································   - ·    ·   -- ··················   -- ···································   - ······························   -- ··················································   --- ·····························   --- ···························   ----- ···················································   --- ········   -----·········································     --- ······························   ---- ········································   ----- ··················································································   -- ······   - ·····································   - ···················································································   --- ··································································   --- ···································································   -- ·······················································································   - ·························································································     - ·······   ---- ·····················································································   - ······························    ·················   -- ··············   - ···   - ·································   ---- ···············   --- ···················   -- ······································   -- ·····   ---  - ············   --- ·················   ------- ······································································   --- ···········································   -- ···········································································   -- ·························   --- ·································································   --- ············································   -- ····   Simulated normal light radiant intensity (I) for µ-LED-coupled microlenses with a fixed base diameter (d1) of 500 µm but varied inclined angles (1) of 30°, 45° and 60°, as a function of the distance between the µ-LED and the microlens (h). The inset shows candela distribution of µ-LED-coupled microlenses that are placed at h = 50 µm. The light radiative flux from each side of the µ-LED was set to 1 W. For comparison, the black dash line shows the value of I for the bare µ-LED. ·········································································   --  -- ························································································   -- ····························   ---- ····················································································   ---- ···································································   ---- ················   --- ·················   ----- ··     CHAPTER 1    Introduction 1.1 Motivation   --     ---        ----      --  -   --------- 1.2 Challenge - --  --- --      --  -- 1.3 Objective --   - --  1.4 Thesis Outline ---     CHAPTER 2    Previous Work 2.1 Surface Tension Modification by Plasma Treatment  -----------    - ---- 2.1.1 Experiment ---  ---  ---------  --   ------ - ---------  ---  --  -- ------ 2.1.2 Results  --  --  --- ---  -----  -----  ---  ----  ---    -----   ------------  -----    --- 2.1.3 Analysis  ---  -- -  -  -  -  ----- --  -- ,                                   (3) -  ---   --- -  -  ----    ---  -----   - ,                                                               (4)   ,                                                                   (5) .                                                              (6)  --  ,                                                            (7) .                             (8) -   ---- TABLE I Representative surface geometrical models of  plasma-treated Parylene-C films, with small error deviations Geometry Relative error deviation in Shape Direction Arrangement Roughness factor RMS roughness Crowns Downward HCP a 3.79% 6.31% Cones Upward SCP b 6.80% 17.90% Half Ellipsoids Downward HCP 7.68% 5.14% Gaussians Downward HCP  7.52% 15.39%                                       a HCP: hexagonal close packing; b SCP: square close packing.  ---  ------- 2.2 Thermal Reflow ---  --  -  -   ---- 2.2.1 Experiment ---- 2.2.2 Results and Analysis  -    ---  -----    ---    --    -    - --  -  --- 2.2.3 Summary ----    ----   CHAPTER 3    Fabrication of Microlens Arrays through Dewetting 3.1 Background --------------  -  - -----     --  ----- 3.2 Theory and Simulation ----- -- ,                                                               (9)   ---- ,                                                          (10)  ,                                                     (11) in which  is the surface tension,  is the density, g the so-called disjoining pressure with a widely-used form introduced by Schwartz and Eley [75]: ,                                    (12) ----   .            (13) -  -- -  ----- 3.3 Experiment   --     ------------  -----  - -    -     -- 3.4 Results        ----------     --  ----    ---    ,                                                      (14)    -  --    --   ----  ---  .                                                             (15)  .                                                           (16)  .                                                           (17)    ----  .                                                             (18)   -- TABLE II Geometrical and optical properties of SU-8 microlenses with typical curvatures t (µm) T (°C) d (µm) h (µm)  (°) f (µm) NA                             --- ----   --    --- 3.5 Discussion -  ---- ----------  ---  -------   -------- 3.6 Summary -------  - ---     CHAPTER 4    Micro-Lens-Coupled LED Stimulators --------- --  -- 4.1 Design Concept ------------  ---   4.2 Fabrication of Device Prototypes -------------- -- -----    --    -- 4.3 Optical Measurement   -----    ---  - --  ------  ---   CHAPTER 5    Optimization of Micro-Lens-Coupled LED Stimulators -----   ---  -  -- --  -  Simulated normal light radiant intensity (I) for µ-LED-coupled microlenses with a fixed base diameter (d1) of 500 µm but varied inclined angles (1) of 30°, 45° and 60°, as a function of the distance between the µ-LED and the microlens (h). The inset shows candela distribution of µ-LED-coupled microlenses that are placed at h = 50 µm. The light radiative flux from each side of the µ-LED was set to 1 W. For comparison, the black dash line shows the value of I for the bare µ-LED.   --  ----    --   -  -  ----   ---  ------ ------------  -  ----       ---    ----     ---- ----  --  ---      ---------   ---     -----   --  ----------       CHAPTER 6    Summary ---------------   --    ----  --  --          Appendix    Experimental Procedure                - ---  -   -     ------- -        --       -       -             -  --  -  --  -  -  -  -  -  -  -  --    ---  ----  --  --  --  -  --  --  ----  -  -  -  -    -  --  -  -----  --  -  --  -  ---  -  ---  --    -  -  -  --  --  -  --  ----  --  ----  -  --    -  -  -  ------  --  -  --  -----  ---  --  ---  ---  --    --  -  --  --  --  -  --  ----  --  --  --  --  --  -  -  ---  --  -  --  -  --  -  --  --  -  -  ---  -  -  -