Repeating monomer of SiO(CH 3 ) units. Polymerization causes cross linking. Visco elastic polymer (Based on n ). H 3 C[SiO(CH 3 ) 2 ] nsi(ch 3 ) 3 Intrinsically hydrophobic. Biocompatible and Oxygen permeable.
Variety of Applications Micro fluidics Molds Microfluidic Devices Devices Brain Slice Device
Hydrophobic because of the methyl groups. Applications of PDMS require it to be hydrophilic. Increased cell adhesion and less repulsion when incubating sample.
Hydrophilicity due to Before Plasma Activation Addition of a Silanol group. Alteration of surface Chemistry. After Plasma Activation Never regains its original hydrophobicity due to permanent scarring of surface.
Vacuum Chamber Erratic Behavior of PDMS after plasma activation. Major instrumentation : plasma chamber. 1.5 CM Schematic Representation of the Plasma Chamber Non uniform activation of plasma. Variation Humidity, atmospheric pressure, flow rate
Least Hydrophobic = Best Area Spatial Location vs Contact Angle Contact Angle 67 62 57 52 47 42 37 32 27 22 1 2 3 4 5 6 7 8 Spatial Placement in Chamber
Quantification Experiment Samples were not aged (10 per time frame). Bonding and contact angle was measured. Image J Since the samples were not aged, could be used as a control Image J is used for measuring contact
P L A S M A 1 hour (10 samples) 2 hours (10 samples) 3 hours (10 samples) 60 PDMS samples A C T I V A T I O N 4 hours (10 samples) 5 hours (10 samples) 6 hours (10 samples) Quant. Bonding Measurements Contact angle Measurements
Bonding vs. Time Quantitative Bonding Strength 10 8 6 4 2 0 10 9.5 8.3 5.3 5.2 p <.005 1.3 0.9 0 1 2 3 4 5 6 Time (Hrs) Time frame of interest
Contact Angle vs. Time Contact Angle (Degrees) 54 49 44 39 34 29 24 19 14 9 p <.0005 46.5485 42.1757 34.6016 34.9736 27.9247 21.2569 10 0 1 2 3 4 5 6 Time (Hrs) Time frame of interest
Contact Angle and Bonding Variation with Time Quantitative Bonding Strength 12 10 8 6 4 2 0 0 1 2 3 4 5 6 Time (Hours) 50 45 40 35 30 25 20 15 10 Contact Angle (Degrees) Bonding Contact Angle Time frame of interest
Test the effect of ageing after plasma activation. Ageing before plasma activation decreases the rate of hydrophobic recovery. In - house goniometer Five samples for each time frame. Compared to the control/quantification experiment. Contact angle on a perfectly hydrophobic surface
P L A S M A 1 hour (10 samples) 2 hours (10 samples) 3 hours (10 samples) A G 60 PDMS samples A C T I V A T I O N 4 hours (10 samples) 5 hours (10 samples) 6 hours (10 samples) E I N G Quant. Bonding Measurements Contact angle Measurements
Contact Angle vs Time Contact Angle (Degrees) 120 100 80 60 40 20 0 1 2 3 4 5 6 Time (Hrs) Aged Sample (1 hr) Aged Sample (2 hrs) Unaged Sample/ Control
Ageing after plasma activation increases the rate of hydrophobic recovery. No significant difference between 1 hour aged samples and 2 hours aged sample. Indicates that although ageing does have an effect, beyond a certain time frame, length of ageing does not matter.
Non uniform surface of Aluminum causes Self contained environment for micro fluidic liquids. Exploits PDMS s strong affinity for Aluminum.
The NSF and DoD for funding this work through grant number CTS 0630470 This project would not have been possible but for the patient oversight of Professor David Eddington and Dr. Javeed Shaikh Mohammad. Their constant support and encouragement was invaluable in the completion of this line of research.
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