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:
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
T ABLE OF CONTENT Introduction Experiments Result and discussion Conclusion AMN & APLOC 2011
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 (200-700kPa) Natural bondingSurface property modification.
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
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 4 - + O Reactive atomic oxygen species AMN & APLOC 2011 +
Bonding mechanism: SiO O CH 3 n PDMS surface O O H 2 O OH - + CH 3 O· OH - OH AMN & APLOC 2011
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
R ESULT & D ISCUSSION 2 methods are used to test bonding power: Tensile strength test Leakage test AMN & APLOC 2011
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 String500473486486.33
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
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 20- 30 seconds.
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
Leakage test Water is pumped into closed channels for 5 minutes at 5,20,50µl/min. No leakage detected!! AMN & APLOC 2011
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
T HANK YOU FOR YOUR ATTENTION. AMN & APLOC 2011