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AN INEXPENSIVE METHOD FOR PDMS-PDMS BONDING IN FABRICATION OF MICROFLUIDIC DEVICE Koh Kai Seng, The University of Notitngham Malaysia Campus The Second.

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Presentation on theme: "AN INEXPENSIVE METHOD FOR PDMS-PDMS BONDING IN FABRICATION OF MICROFLUIDIC DEVICE Koh Kai Seng, The University of Notitngham Malaysia Campus The Second."— Presentation transcript:

1 AN INEXPENSIVE METHOD FOR PDMS-PDMS BONDING IN FABRICATION OF MICROFLUIDIC DEVICE Koh Kai Seng, The University of Notitngham Malaysia Campus The Second Conference on Advances in Microfluidics and Nanofluidics and Asian-Pacific International Symposium on Lab on Chip 5 th -7 th January 2011, Singapore AMN & APLOC 2011

2 T ABLE OF CONTENT Introduction Experiments Result and discussion Conclusion AMN & APLOC 2011

3 I NTRODUCTION Poly(dimethylsiloxane) (PDMS) has been widely used in microfluidic applications. Sealing has been the key challenges in microfluidic fabrication. Reversible bonding, irreversible bonding. AMN & APLOC 2011 Reversible bondingIrreversible bonding Reusable.Not reusable. Able to sustain low pressureAble to sustain relatively high pressure ( kPa) Natural bondingSurface property modification.

4 Conventional sealing techniques require Costly equipments.(Oxygen plasma) Time consuming. (Partial curing technique) Involve complicated steps. (Oxygen plasma) Reliability and repeatability are always at the centre of argument. AMN & APLOC 2011 Piranha solution is used because More economical, Time saving, Involve less complicated steps. Relatively high reliability and repeatability

5 B ONDING MECHANISM First stage: Dehydration of hydrogen and oxygen into water unit. Second stage: H 2 SO 4 + H 2 O 2 H 3 O + +H 2 O O Reactive atomic oxygen species AMN & APLOC

6 Bonding mechanism: SiO O CH 3 n PDMS surface O O H 2 O OH - + CH 3 O· OH - OH AMN & APLOC 2011

7 E XPERIMENT M ETHOD Sealing procedure: PDMS samples with strings embedded in it were solidified. The samples were cut into 2cm × 2cm square piece each. Piranha solution concentrated Sulfuric acid (96wt%) & Hydrogen peroxide(30wt%) at 3:1 weight ratio. Interfaces of two PDMS are drenched into the solution for a define interval. Next, both surfaces attached and bounded together followed by thermally curing of 70°C for 60 minutes. AMN & APLOC 2011

8 R ESULT & D ISCUSSION 2 methods are used to test bonding power: Tensile strength test Leakage test AMN & APLOC 2011

9 Table 1: Tensile strength (kPa) against drenching time (sec) at 3:1 weight ratio of Piranha solution AMN & APLOC 2011 Table 2: Calibration of tensile strength of string (kPa) Material Tensile strength (kPa) 123Average String

10 P IRANHA SOLUTION USING HNO 3 (65 WT %) + H 2 O 2 AT 3:1 WEIGHT RATIO AMN & APLOC 2011 Table 3: Tensile strength (kPa) against drenching time (sec) at 3:1 weight ratio of Piranha solution

11 Figure 1: Graph average tensile strength (kPa) against drenching time (sec) AMN & APLOC 2011 Sustaining time of the PDMS-PDMS interfaces is within the range of seconds.

12 Optimum drenching time is 45 seconds. Reaction ends at around 65±5seconds. Pure Sulfuric acid remains. (limiting reactant is Hydrogen peroxide). PDMS surface will be attacked. AMN & APLOC 2011

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14 Leakage test Water is pumped into closed channels for 5 minutes at 5,20,50µl/min. No leakage detected!! AMN & APLOC 2011

15 C ONCLUSION An inexpensive polymer-based sealing technique, using piranha solution (3:1 weight ratio) is demonstrated and quantitative result is shown. This irreversible bonding techniques is able to sustain a mechanical strength of (200±20kPa). Water is injected into closed microchannels at different flowrates and no leakage occurred up to a flowrate 0.3ml/hr. In future work, optimization of the bonding strength using the same method will be investigated. AMN & APLOC 2011

16 T HANK YOU FOR YOUR ATTENTION. AMN & APLOC 2011


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