FABRICATION OF MICROFLUIDIC CHANNELS USING MICROFIBERS FOR APPLICATIONS IN BIOTECHNOLOGY

Transcription

1 FABRICATION OF MICROFLUIDIC CHANNELS USING MICROFIBERS FOR APPLICATIONS IN BIOTECHNOLOGY Tom Huang, 1,5 Woo-Jin Chang, 2 Demir Akin, 2 Rafael Gomez, 2 Rashid Bashir, 2,3 Nathan Mosier, 4 and Michael R. Ladisch 3,4,5 1 School of Chemical Engineering, 2 School of Electrical and Computer Engineering, 3 Department of Biomedical Engineering, 4 Department of Agricultural and Biological Engineering, 5 Laboratory of Renewable Resources Engineering Purdue University, West Lafayette, IN

2 ACKNOWLEDGEMENT Research supported by ARS of USDA (# ) and a grant from National Defense University (DAB J29-03-P-0022) Tim Miller, C-Y Fong, Bill Crabill (SSLAB) Kunn Hadinoto and Xiaotao Wan (CHE) Richard Low and Dr. David Taylor (CHE) LORRE group members

3 BACKGROUND INFORMATION Microfluidic technology Movement and control of fluids at microscopic level Micron-sized fluidic channels Applications of microfluidic systems Biological assays Point of care testing Chem/bio detections Advantages Consumes less regents Higher sensitivity Shorter analysis time

4 SCALE OF INTEREST 1mm typical microchannels typical microchannel patterning { { } } 10µm 1µm cellular scale radius of gyration of DNA 100µm } 100nm persistence length of double stranded DNA { } 10nm 10Ǻ=1nm } 1Ǻ protein s Debye screening in charge double layers organic molecules Stone and Kim, 2002

5 RAPID PROTOTYPING USING UV High resolution transparency as mask photoresist SiO 2 or silicone substrate Develop photoresist obtains master Pour over master Cure 70 C for 1 hour Release from master and seal against a flat substrate Microchannels formed. PROCESS TAKES A DAY

6 THE NEED Simple and rapid fabrication Well defined surface chemistries Flexibility and adaptability Amendable for rapid prototyping techniques

7 MICROFIBER ASSISTED FABRICATION Flat cover Glass fiber (~12 µm diameter) SiO 2, glass, or substrate Labeled avidin (green) and BSA (red) liquid mixture; t=0 SiO 2 substrate Glass substrate (a) (b) (c) t= ~3 minutes 1 nl/mm channel SiO 2 Glass fiber TAKES LESS THAN 1 HOUR Flow channel Huang et al., 2003

8 MIXING IN MICROCHANNEL Glass fiber (~12 µm diameter) SiO2 substrate (a) Labeled BSA (red; 200 µg/ml)); t=0 Labeled avidin (green; 200 µg/ml)); t= ~10 seconds 1 nl well at intersection (b) t= ~3 minutes Huang et al., 2003

9 COATING MICROFIBERS WITH MICRO/NANO PARTICLES (a) Dimethylamino microbeads (0.8um diameter) Glass fiber Avidin microbeads (0.8µm diameter) Biotinylated BSA coated glass fiber (b)

10 MICROSCALE SEPARATION DEVICE Labeled avidin (green; 10 µg/ml) and BSA (red; 10 µg/ml) liquid mixture; t=0 Labeled avidin (green; 10 µg/ml) and BSA (red; 10 µg/ml) liquid mixture; t=0 Glass substrate Glass fiber coated with dimethylamino microbeads Glass substrate Glass fiber coated with biotinylated BSA (a) t= ~3 minutes (b) t= ~5 minutes Huang et al., 2003

11 SURFACE EFFECT IN MICROFLUIDIC CHANNELS Hydrophobic vs. Hydrophilic Surface chemistry of a microchannel is extremely important in the movement and control of fluids at microscopic level Water in hydrophobic channel Water in hydrophilic channel

12 FLUIDIC SIMULATION OF LIQUID FLOW IN HYDROPHILIC MICROCHANNEL (a) Symmetry (b) L=72 µm Glass fiber Hydrophilic SiO 2 Flow channel 1 Flow channel 2 Glass fiber H=12 µm W=48 µm Mass conservation equation: Momentum conservation equation:

13 MTHODS AND GEOMETRIES Outflow Outflow H=12 µm Inflow L=72 µm H=12 µm L=72 µm Inflow y Assumptions: W=48 µm Laminar flow z x W=48 µm Incompressible flow (Density is constant) Steady state flow (Flow is independent of time.) Fluid is Newtonian Fluids behaves as continuum No slip at the walls

14 SIMULATION RESULTS Boundary conditions: No slip at walls (V z =0) Inflow condition: Average velocity (V z =0.001m/s) Outflow condition: Pressure = 0 Pascal Microfiber microchannel (simulation results) Rectangular microchannel (simulation results) Rectangular microchannel (analytical results)* Q=0.024 µl/min Q=0.035 µl/min Q=0.035 µl/min Vmax m/s Vmax m/s Vmax m/s P = 10.7 Pascal P = 7.5 Pascal P = 7.2 Pascal N Re = N Re =0.003 N Re =0.013 *Calculation based on equation by (Foster and Parker, 1970)

15 (a) VELOCITY PROFILE (b)

16 FLUID FLOW IN LIQUID FILLED HYDROPHILIC MICROCHANNEL Pipette in labeled 0.6 µm polystyrene beads Vacuum = 127 mmhg Hydrophilic glass L= 1cm

17 C18 MODIFICATION O H O H O H O H O SiO 2 Si H O H O H O H O H Cl Hydrophilic surface with a contact angle of <15 º using DI water Octadecyltrichlorosilane (OTS) Si Cl Cl Si Si Si Si O O OO O OO O OO O O SiO 2 Si Hydrophobic surface modified with C18 with a contact angle of ~ 118 º using DI water Ladisch, 2003

18 HYDROPHOBIC EFFECT ON LIQUID FLOW Pipette in labeled 0.6 µm polystyrene beads L= 1cm Vacuum = 127 mmhg Hydrophobic C18 Liquid Air Liquid Air Air Air

19 PARTICLE FLOW IN FOCUSED LIQUID STREAMS 2.3 µm beads in water at inlet 2.3 µm beads in water at outlet Sample liquid Air Sample liquid Air Air Air

20 GFP E. coli FLOW IN FOCUSED LIQUID STREAMS 1-2 µm GFP E. coli (~10^6 cells/ml) in PBS 1-2 µm GFP E. coli (~10^6 cells/ml) in PBS (~ 10 um/s) slow (~ 100 um /s ) faster

21 GENERATION OF FLOW DATA AND WORK IN PROGRESS Air slit PMT Microscope objective HV power Microchip Oscilloscope TWO-PHASE FLOW MODEL

22 SUMMARY Microfiber assisted fabrication provides Simple and rapid fabrication of microchannel Well-defined chemistry Flexibility and adaptability Useful research tool for studies of Microfluidic transport Microfluidic separation, mixing Microfluidic reaction, sensing Demonstrated hydrophobic effect of microchannel on liquid flow

23 THANKS FOR YOUR ATTENTION!

24 MORE ON LIQUID FOCUSING Air inlet 1 Sample liquid inflow To Vacuum P=0-0.5 atm C18 substrate Air inlet 2 (a) Air inlet 2 (OPEN) (b) Air inlet 2 (CLOSED) liquid Air liquid Air Air

25 MANY OTHER APPLICATIONS Microchip capillary electrophoresis Sample injection Sample dispensing Separation High voltage High voltage

26 ADVANTAGES OF MICROFLUIDIC SYSTEMS Miniaturization and Lab-on-a-chip Consumes less expensive regents Higher sensitivity Shorter analysis time More efficient product yields Improved integration Increased automation Increase throughput for parallel analysis

27 FABRICATION OF MICROCHANNELS UV Photomask Photoresist SiO 2 or silicone substrate Develop photoresist Etching with gas or acid Purdue silicon biochip (Gomez et al., 2001) Remove photoresist Thermal or anodical bonding with cover plate Microchannel Caliper glass lab-on-a-chip

28 MICROSCALE COULTER COUNTER Microfiber Microelectrode for four-point measurement Particle inflow Particle outflow