The Hong Kong University of Science and Technology Final Year Project presentation 2007

Transcription

1 The Hong Kong University of Science and Technology Final Year Project presentation 2007 Project supervisor: Dr. Andrew Poon Department of Electronic and Computer Engineering Wong Ka Ki Chris, ee_wkkaf, Wong Tsz Ong Mark, ee_wto, Wong Tsz Ming Keith, ee_wtm,

2 Introduction

3 A B C Bottle A Bottle B Bottle C C A B? Bottle C Bottle A Bottle B

4 Project Objective Preliminary testing and sorting of droplets based on light scattering principles. Fast and non-intrusive such that the nature of sample would not be affected.

5 Droplet Generator. Pinhole STEP 1 vibrate Droplet filter Speaker Function Generator Gated Red Laser 60º CCD timer E CCD 2 STEP 3 42º Droplet Objective Lens To PC (Interferometic Particle Imaging ) STEP 2 To PC (Rainbow Refractometry) Air Puffer PC Data input from CCDs Glass Plate CCD 1 CCD 2 STEP 5 STEP 4 Wanted droplet Unwanted droplet Move using step motor Motor

6 System Flow Five Steps Approach [Step 1]: Droplet is produced by droplet generator. [Step 2]: Droplet size is determined by CCD1 (Interferometric Particle Imaging) [Step 3]: Droplet refractive index is determined by CCD2 (Rainbow Refractometry) [Step 4]: Computer analysis. [Step 5]: Unwanted droplets are sorted by air puffer

7 Project Advantages & Applications

8 Project Advantages Fast-testing Preliminary Result Non-intrusive Non Bio-Chemical

9 Applications Pharmaceutical Industries Medical Testing Bacteria Medicine Composition Industrial workplace Pigment

10 Droplet Generator. Pinhole Function Generator Upstream vibrate Speaker Droplet filter Gated Red Laser 60º CCD timer CCD 2 42º Droplet Objective Lens To PC (Interferometric Particle Imaging) Mid-stream Wanted droplet Unwanted droplet To PC (Rainbow Refractometry) Glass Plate Air Puffer Syringe Knob PC Data input from CCDs Down-stream Move using step motor Motor

11 Upstream

12 Components [Droplet Generator] -Produces a stream of droplet samples -Manual control of production rate [Droplet Filter] -Falling path control

13 Droplet Generator: To start [Primary ideas]: (1) Syringe? (2) Burette? (3) Dropper? (4) Spraying bottle?

14 Droplet Generator: Structure [Building unit]: (1) Loudspeaker (2) Syringe (3) Plastic tape (4) Optical fiber (5) Function generator [Where does this idea come from?] [Building steps]

15 Droplet Generator: Performance Droplet production rate can be controlled by the function generator Droplet size is approximately 270µm in diameter [Problem]: - Falling path deviation - Plastic tape depreciation

16 Droplet Filter [Any water-resistive materials / tools]: -Laser aperture control -Screw -Plastic taped surface with a tiny hole in the middle Video number: P

17 Mid-stream

18 Components [Gated laser source] -Hitting the sample droplet to gives out scattering patterns -As a light source for image capturing [CCD cameras] -Located at 42 0 and 60 0 respectively -Capture light scattering patterns

19 Why Gated laser source?? Blurred images Overlapping of images even from a single sample droplet Limitation of the shutter s speed of the CCD camera

20 Gated laser source Stroboscopic Investigation technique Overlapping of images is resolved Pulse duration = 0.4µs

21 Image Capturing Two light scattering techniques were used: Droplet size measurement Interferometric Particle Imaging (IPI) Droplet Refractive Index determination Rainbow Refractometry What is Light Scattering?

22 Light Scattering from Droplet Interaction of a laser beam with droplets is considered Incident plane wave k The laser is operated in the TEM00 mode creating a beam with a profile of Gaussian like y φ r x Detector When the droplet is comparably small to the diameter of the laser source, the Gaussian beam can be considered to be a plane wave The interaction between the laser beam and the droplet results in light scattering in all directions around the droplet Droplet θ z Scattering plane Polarization plane The scattered light can be captured by a receiver, for example, a CCD camera which is placed on the scattered plane The region with (0º θ 90º) is called forward scattering region, whereas the remaining hemisphere is called backward scattering region. The intensity distribution can be calculated with Lorenz-Mie Theory

23 Light Scattering from Droplet Forward Scattering Region Backward Scattering Region 2 nd rainbow 1 st rainbow Light Source Related intensity versus scattering angle Plotted by MiePlot. (n =1.334, λ =650nm, droplet diameter = 20µm) In the forward light scattering region, interference patterns with regular fringe spacing can be observed and part of this scattered light can be used to determine the Falling droplet droplet size. (Interferometric Particle Imaging) In the backward light scattering region, rainbow fringes are observed and they are droplet content dependent, for example texture and refractive index. (Rainbow Refractometry) Red Laser

24 Theories of Light scattering Why such intensity distribution comes out? If the droplet size is much smaller than the wavelength of the laser source (d << λ) Raleigh theory will be applied. If the droplet size a much larger than the wavelength of the laser source (d >> λ) geometrical optics will be applied However, geometrical optics does not provide an accurate result in scattering angles Lorenz-Mie theory. It works well for all droplets sizes and scattering angles. This theory came out from Lorenz (1890) and Mie (1908). It is a wave theory that is a solution of Maxwell s equations for Electromagnetic waves. Geometrical optics has deficits but it still helps to understand the light scattering phenomena Incident Light P = 0, Reflection droplet θ P = 1,1 st Refraction By Snell s law The 1st refraction is on the forward scattering region. The interference of these refracted lights together with the reflected light results in the regular interference fringes pattern While the scattered angle of different light rays from the 2nd refraction attains maximum at a certain angles, which is called rainbow angle P = 2, 2 nd Refraction

25 Rainbow Refractometry Refractive index is an important parameter for one to obtain additional information from a droplet Several laser-based techniques have been investigated. E.g. fluorescence and intensity-based light scattering Fluorescence: Additives are added and these pollute the droplet sample Intensity based light scattering: The intensity distribution of the scattered light is used to determine the droplet refractive index. E.g. Rainbow Refractometry The interference between internally reflected rays will induce a low frequency structure called Airy fringes. The interferences between internally and externally reflected rays will cause a high frequency structure called ripple structure superimposed on the Airy fringes Airy Theory Lorenz Mie theory Diameter: 200µm Refractive Index: 1.33 Wavelength: 650 nm Lorenz-Mie theory, we can compute the rainbow scattered by a single droplet. This helps us to determine the refractive index of the droplet

26 Rainbow Refractometry How the refractive index is determined? n = 1.33 n = 1.34 n = 1.35 The refractive index is determined from the absolute angular position of the interference pattern, the pattern shifts uniformly for about 1.5º when the refractive index changes by 0.1 Another method such as the relative intensity of the first few peak of the fringes of different are measured to obtain the refractive index. However, the pattern is size dependent, droplet size should be known Interferometric Particle Imaging (IPI)

27 Interferometric Particle Imaging (IPI) Technique used to measure droplet size Top View Non Focal Plane Focal plane 1 st refraction z Focused Image Droplet θ α da Reflection Aperture Red Laser Beam Lens Image Plane d = 2 λn msin( θ / 2) 1 α (cos( θ / 2) + m 2 ) 2mcos( θ / 2) + 1 N is the number of fringes, λ is the source wavelength, m is the refractive index of the liquid droplet, θ and α are the scattering and collecting angles, respectively. α is equivalent to the product of fringe number N and angular inter-spacing Δδ

28 Interferometric Particle Imaging (IPI) The dependence of the size measurement on the refractive index reduces to a minimum as a scattering angle of 60. In the other word, the diameter measurement is less dependent on the refractive index of the droplet. By measuring the number of fringes captured by a CCD camera non focused plane, droplet diameter can be obtained by the equation.

29 Down-stream

30 Sorting System Electrostatic Sorting Air Puffing

31 Electrostatic Wanted Cell Unwanted Cell

32 Electrostatic Implementation Difficulties Charge Injection High Voltage (Hazard)

33 Air Puffer Advantages: Relatively Safe Syringe Easy to Control Plastic membrane Needle

34 Air Puffer Real Time On Substrate Glass Plate Syringe Wanted droplet Unwanted droplet

35 Real Time Puffer Triggering signal Plastic membrane MP3 layer Amplifier magnet Loud Speaker 3W Syringe Needle

36 On Substrate Puffer Knob Plastic membrane nail Syringe Needle Motor

37 Result

38 Droplet size measurement Water, 3% glucose, 10 % glucose having different refractive index were measured. Number of interference fringes were counted by ImageJ. Using the equation from IPI, we can obtain the droplet size. Scattering angle of around 60 was used to obtain a lesser dependence of the refractive index on the droplet size measurement. In this experiment, λ = 650nm. α = rad and θ = 60º 10 samples were used for the calculation in each set of data. Water Refractive index is 1.33 at room temperature. Average number of fringes = 30.6 Droplet diameter = μm 42.0

39 Droplet size measurement 3% Glucose Solution Refractive index is at room temperature. Average number of fringes = 33.1 Droplet diameter = μm 10% Glucose Solution Refractive index is at room temperature. Average number of fringes = 33.8 Droplet diameter = μm

40 Droplet size measurement The average diameter of a falling droplet calculated by the IPI equation is 270.1μm, which is close to estimated droplet diameter from the photo.

41 Rainbow Refractometry P = 0, Reflection Droplet Incident Light P = 1,1 st Refraction θ P = 2, 2 nd Refraction (Rainbow Region) Backscattering

42 Rainbow Refractometry HeNe gas Laser Wavelength ~ 632.8nm Optical power ~ 20mW

43 Rainbow Refractometry

44 Rainbow Refractometry Droplet Intensity Measurement Relative Intensity Pixel (Distance)

45 Rainbow Refractometry Water (sample): Water Intensity Pixel (Distance) Contrast Ratio = (55/96) X 100% = 56%

46 Rainbow Refractometry 10% Glucose Solution (sample): 10% Glucose Solution Intensity Pixel (Distance) Contrast Ratio = (63/104) X 100% = 60.5%

47 Rainbow Refractometry 30% Glucose Solution (sample): 30% Glucose Solution Intensity Pixel (Distance) Contrast Ratio = (73/110) X 100% = 66.4%

48 Rainbow Refractometry Summary Table: Contrast Ratio Water 10% Glucose 30% Glucose captured photos for each solution 0

49 Rainbow Refractometry Water 10 % Glucose 30% Glucose

50 Rainbow Refractometry Frequency 12 Comparison Between Contrast Ratio Verus Differnent Aqeous Solution Water 10% Glucose Solution 30% Glucose Solution Contrast Ratio

51 Conclusions

52 Limitations Preliminary test Affected by air flow

53 Limitations

54 Eccentricity Limitations

55 Droplets Shape Limitations

56 Limitations Sensitivity ( n???) Solution Water 10% Glucose 30% Glucose Refractive Index 1.33?? Concentration = Mass of Glucose (g) Water Volume (ml) X 100%

57 Limitations Example. Slope = 2.5µ n/mg/dl g/ml mg/dl (10% Glucose) 1g/10mL mg/dl n = 0.025

58 Limitations Solution Refractive Index Water % Glucose % Glucose Sensitivity = 0.03

59 Improvement Smaller droplet can be generated by ink-jet printer Scattering angle detection can be used as an additional information to the change in refractive index The glass plate can be replaced by a Micro-fluidic cells that droplets can be further investigated bio-medically

60 Example on the usage of micro-fluidic cells Data from CCD Data from Micro-fluidic cell Microscope Air Puffer Output Signal Puff of air hydraulic pull Unwanted Droplet Wanted Droplet Micro-fluidic cells Light ray Diode

61 Contributions & Further work

62 Acknowledgements & Final Words