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- 1. Ghulam Destgeer Particle Separation and Chemical Gradient Control via Focused Travelling Surface Acoustic Waves (F-TSAW) Flow Control Laboratory, Department of Mechanical Engineering 2013.06.10
- 2. 2 Contents • Introduction • Theory • Device design and fabrication • Experimental setup • Results • Summary
- 4. 4 Particle separation • The isolation and separation of micro particulate materials in a continuous flow are required for chemical syntheses and biological analyses. • The separation and sorting of cells are critical in a variety of biomedical applications including: i. Diagnostics ii. Therapeutics iii. Cell biology <Lee et al., 2010, Lab Chip> <Daniel et al., 2010, Anal Bioanal Chem> Huang’s group Sung’s group
- 5. 5 Particle manipulation by SSAW • Particle separation: – Particle diameter: 0.87μm (Red), 4.16μm (Green) • Experimental parameters: – Frequency: 12.6MHz – Power: 15-22dBm (30-160mW) – Flow rate: 0.6-2μl/min <Shi et al., 2009, Lab Chip>
- 6. 6 Chemical gradient control • Most methods are capable of generating linear chemical gradient profiles in a static manner. • Generating pulsatile chemical gradients in microfluidic devices has important implications for the characterization of dynamic biological and chemical processes. • Dynamic temporal control of chemical gradients is required. <Ahmed et al., 2013, Lab Chip> <Daniel et al., 2006, Anal. Chem.> <Seidi et al., 2011, Biomicrofluidics>
- 7. 7 Chemical gradient control by oscillating bubbles • Chemical solutions: – Dextran-FITC (stimulant) – Phosphate buffered saline(buffer) • Input voltage and frequency: – 12-16Vpp and 30kHz <Ahmed et al., 2013, Lab Chip>
- 8. 8 Objective • (a) Device schematic (b) Particle separation • (c) Chemical gradient control and uniform micromixing • (d) F-TSAW amplitude (e) Fabricated device
- 9. Theory
- 10. 10 Acoustic radiation force on compressible spheres For TSAW: <Yosioka & Kawasima, 1955, Acoustica> 𝐸 𝑎𝑐 = (4π𝑓𝑢)2 𝜌 𝑓 𝐴 2 = 2(4π𝑓𝑢)2 𝑘2 = 8(𝑐𝑢)2𝐴 2 = 2 𝐸 𝑎𝑐 𝑘2 𝜌 𝑓 where, 𝐸 𝑎𝑐 is acoustic energy density, 𝑢 is SAW amplitude, 𝑘 = 2π λ is wavenumber, 𝑐 is speed of sound on wafer surface, 𝑓 is the frequency of SAW, Pin is the input power and V is the input voltage. where, 𝛼 = 𝜌 𝑓 𝜌 𝑝 , 𝛽 = 𝑐 𝑓 𝑐 𝑝 , R is radius of μ-particles & A is complex amplitude of the velocity potential. 𝐹 𝑇𝑆𝐴𝑊 = 2𝜋𝜌 𝑓 𝐴 2(𝑘𝑅)6φ 𝑇𝑆𝐴𝑊 φ 𝑇𝑆𝐴𝑊 = 1 − 𝛼 2 + 𝛼 𝛽2 3 2 + 2 1 − 𝛼 2 9 (2 + 𝛼)2 TSAW Flow 𝐹 𝑇𝑆𝐴𝑊 ~ 𝑉2 𝑓6 𝑅6 ~ Pin 𝑓6 𝑅6
- 11. 11 F-TSAW amplitude • Acoustic wave amplitude is estimated as: • Acoustic wave amplitude qualitative measure: 𝑢(𝑥, 𝑧) ≈ 1 𝑍1/4 −∞ +∞ 𝐺 𝑡 exp 𝑗 𝑡4 +𝑍′ 𝑡2 +𝑋′ 𝑡 𝑑𝑡 𝑍′ = (0.145𝑍 − 𝑅𝑘0/2) 4.98𝑍 𝑋′ = −𝑋 4 4.98𝑍 𝑡 = 4 4.98𝑍𝐾1 𝑍 = 𝑘0 𝑧 𝑋 = 𝑘0 𝑥 𝐾1 = 𝑘1/𝑘0 <Fang and Zhang, 1989, IEEE Transactions on Ultrasonic> <Wu et al., 2005, IEEE Transactions on Ultrasonic> Wu et al. 2005 Calculated θ R A A’
- 12. 12 F-TSAW amplitude 5R 5R 5R 5R 5R 5R 5R 5R 5R AmplitudeAmplitudeAmplitude AmplitudeAmplitudeAmplitude AmplitudeAmplitudeAmplitude
- 14. 14 SAW amplitude calculation F 𝑇𝑆𝐴𝑊~ (Eac/k2) (kR)6φ 𝑇𝑆𝐴𝑊 E 𝑎𝑐~ u2 f2 ρ Energy density (Eac) – J/m3 SAW displacement (u) – nm Frequency (f) – MHz Density (ρ) – kg/m3 Wave number (k) – (μm)-1 Particle radium (R) – (μm) Constant (φ) Contour plots of SAW displacement square (u2) – m2 Top – f =133.3MHz Bottom – f = 40.0MHz x z
- 15. Device design and fabrication
- 16. 16 F-TSAW device design • Two salient features: (i) unidirectional (ii) focused • Interdigitated transducer(IDT): Two interlocking comb-shaped metallic electrodes on top of a piezoelectric substrate. • Frequency of applied AC signal = frequency of SAW (fSAW) – fSAW = c/λ, c is speed of sound in the piezoelectric substrate Maximum energy is transmitted in the forward direction. Very little energy is transmitted in the backward direction. SAW λ λ/8 λ/43λ/16 SAW Unidirectional transducer λλ/4 SAW SAW IDT F-TSAW amplitude by a focusing transducer
- 18. 18 Microfluidic channels 150µm 500µm200µm 1st 2nd 3rd
- 21. 21 Experiment schematic Signal generator, N5181A [3GHz] μ-pump, neMESYS Microscope, BX51 Camera, DP26 Power amplifier, ZHL-1-2W DC power supply, E3634A Micro Chip PDMSLiNbO3 Au electrodes
- 22. 22 Experimental setup Power supply Amplifier Signal generator Microscope Microchip Micropump Display screen Oscilloscope Camera
- 23. Results
- 24. 24 Experimental parameters PARAMETERS Device #1 Device #2 Device #3 Device #4 Frequency (MHz) 40 133.3 133.3 133.3 Input power 0.25µW 0.45mW 0.07mW --- After amplification 0.175mW 275mW 63mW 60–200mW Radius of FUT (mm) 6 4 4 4 Distance from FUT to microchannel 1.25R 2.5R 2.5R 2.5R µ-channel cross section (µm×µm) 150×110 150×45 200×40 500×90 Particles diameter (µm) 30 and 10 10 and 3 10 and 3 --- Fluid/media DI water DI water DI water DI water, rhodamine Total flow rate (µl/hr) 50 150 100 100 Average velocity (mm/s) 0.84 6.17 3.5 0.6 Function Particle Separation Particle Separation Particle Separation Gradient Generation Names CAPS-1 CAPS-2 CAPS-3 CAGG *CAPS: Cross-type Acoustic Particle Separator *CAGG: Cross-type Acoustic Gradient Generator
- 25. 25 CAPS-1: Particle trajectory and separation • Experimental conditions: – Frequency (f): 40MHz (Low) – Input power: 725µW – Flow rate (Q): 50μl/h (0.84mm/s) – μ-channel cross-section: 150x110μm – μ-particles diameter: 10, 30μm • Equation of particle motion: • Acoustic radiation force: • Stokes drag force: • Particle trajectory: – Left figure: Theoretical – Center figure: Experimental • Particle separation on right 𝑚 𝑧 = 𝐹 𝑇𝑆𝐴𝑊 − 𝐹 𝐷 𝐹 𝑇𝑆𝐴𝑊 = 4π𝐸 𝑎𝑐 𝑘4 𝑅6φ 𝑇𝑆𝐴𝑊 𝐹 𝐷 = 6πη𝑅 𝑧
- 26. 26 CAPS-2: Particle trajectory and separation • Experimental conditions: – Frequency (f): 133.3MHz (High) – Input power: 1.36W – Flow rate (Q): 150μl/h (6.17mm/s) – μ-channel cross-section: 150x45μm – μ-particles diameter: 10, 3μm • (a) Schematic diagram of a PDMS microchannel. • (b-c) Once the TSAW was turned ON, a distinct separation distance could be observed. • (d) Trajectory followed by a 10 µm particle influenced by acoustic streaming.
- 27. 27 CAPS-3: Particle trajectory and separation • Experimental conditions: – Frequency: 133.3MHz – Input power: 225mW – μ-channel cross-section: • h x w: 40 x 200 μm – Flow rate (Q): • Sample+ Sheath: 25μl/h + 75μl/h = 100μl/h • Average speed: 3.5mm/s – μ-particles diameter: 3μm and 10μm • Left: TSAW OFF, all the particles flowing together with the laminar flow. • Right: TSAW ON, larger particles are pushed towards the opposite wall resulting in separation
- 28. 28 Particle separation efficiency • (a) TSAW OFF: all of the particles are collected at the same outlet • (b) TSAW ON: 3µm particles are collected at same outlet whereas almost 100% of the 10µm particles passed through a separate outlet. (a) (b)
- 29. 29 CAPS-3: Particle deflection vs. input power • Flow rate is kept constant: – Sheath + Sample = 80 + 20 = 100 µlh-1
- 30. 30 CAPS-3: Deflection vs. input power and flow rate • For particles with diameter 10µm:
- 31. 31 CAPS-3: Deflection (µm) vs. Input Power (mW)
- 32. 32 CAGG • Acoustic streaming flow induced via F-TSAW • Flow is traced by 1µm polymer microspheres dispersed in DI water. • On smaller particles, drag force is dominant compared to acoustic radiation force. • Three microchannels 150µm x 45µm, 200µm x 40µm and 500µm x 90µm from left to right, respectively, are tested. • Microchannel 500µm x 90µm can produce strong and large vortices appropriate for mixing and gradient control. F-TSAW F-TSAW
- 33. 33 Chemical gradient control and micromixing • Acoustic streaming flow – Generate chemical gradient – Uniformly mix fluids. • Microchannel – w×h: 500µm×90µm • Flow rate: 100µl/h (0.6mm/s) – Fluid 1: rhodamine: 50µl/h – Fluid 2: DI water: 50 µl/h • Power input – Gradient control: 60–200mW (18– 23dBm) – Uniform mixing: 800mW (29dBm)
- 34. 34 Chemical gradient control and micromixing
- 35. 35 Summary • Four types of devices are tested: – First three are Cross-type Acoustic Particle Separator (CAPS) – Fourth is Cross-type Acoustic Gradient Generator (CAGG) • A single micro-chip is capable to be used as CAPS or CAGG • Particles are successfully separated with efficiency close to 100%: – 10μm particles from 3μm and 30μm particles from 10μm • Particle deflection is plotted against input power which shows: – 3μm, 7μm and 10μm are separated • Low amplitude and high frequency (40 and 133.3MHz) waves are used. • Chemical gradient control and uniform mixing is also shown using F-TSAW without trapping any micro-bubble.
- 36. THANK YOU FOR YOUR ATTENTION!!!