PDMS plasma bonding - NanoLabStaff/nanolab GitHub Wiki

by Armend G. Håti and Jonas M. Ribe

Update 30.01.2015: After having some issues with PDMS plasma bonding we cleaned the whole vacuum chamber by bead blasting. The plasma bonding is now consistent again, but the parameters have changed. Updated parameters are given below, but the comparison experiment has not been repeated.

Oxygen plasma treatments can be used to covalently bond PDMS to glass or PDMS to PDMS. The protocol is very simple:

  1. Clean the surfaces you want to bond

  2. Expose samples to oxygen plasma in Femto plasma cleaner

    O2 [%] Power [%] Time [s]
    50 20 24

  3. Bring samples slowly in contact. Start from one side to prevent bubbles.

Old parameters:

From a simple bond comparison test, we gather that the oxygen flow has less impact on the bond strength than the plasma power. The Femto plasma cleaner gave consistently good results for 80% power, 50% O2 flow and 12s exposure time. For lower power, we had some samples fail. We suspect this to be a result of delayed ignition of the plasma. By doing longer exposures at lower power this problem would be minimized. However, too long exposures or too high intensity will reduce the bond strength as well.

Experimental

Using the Femto plasma cleaner in the characterization finger we tested the bond strength of PDMS to glass after different oxygen plasma exposures. The PDMS was tape cleaned before use. Glass slides were washed with acetone, then IPA and blow dried. Each PDMS slab was bonded between two different glass slides to compare bond strengths of different parameters. The top side of the PDMS was treated with parameters A and the bottom side with parameters B. The samples were left under ambient conditions for 10-15min before testing. The bonding was tested by peeling the glass slides from one another by hand. If the glass slides would not separate or the PDMS would split, leaving a complete film of PDMS on both slides, the bonds were assumed both good. If one of the bonded surfaces would break of cleanly or partially cleanly, that plasma bond was assumed to be weaker.

Oxygen flow

O2 [%] Power [%] Time [s] vs O2 [%] Power [%] Time [s]
20 50 12 both bad 80 50 12
20 50 12 both good 50 50 12
80 50 12 higher is better 50 50 12
O2 [%] Power [%] Time [s] vs O2 [%] Power [%] Time [s]
20 80 12 both good 50 80 12
20 80 12 both good, but lower slightly better 80 80 12

Power intensity

O2 [%] Power [%] Time [s] vs O2 [%] Power [%] Time [s]
50 20 12 lower is slightly better 50 80 12
50 60 12 both good 50 80 12
50 60 12 lower is better 50 100 12
50 80 12 both good 50 100 12

Plasma exposure time

O2 [%] Power [%] Time [s] vs O2 [%] Power [%] Time [s]
50 80 6 both good 50 80 12
50 80 12 both good ,but lower slightly better 50 80 18
50 80 12 both good 50 20 48

Discuss this protocol!