Different treatments of the plasma cleaner have been tested in order to achieve the best hydrophilic properties. Here is the protocol for hydrophilic treatment:
- Place your samples on the window inside the plasma, the faces that need to be treated should be facing up
- Close the chamber, start the pump and wait for the vacuum to stabilize (around .1 mbar)
- Open the oxygen bottle (two valves) and set the flowmeter to a value of 60
- Let the chamber fill with oxygen for 5 minutes at least
- Decrease the flow of oxygen to a value of 5 (the bead in the flowmeter is always oscillating a bit, use your integrating eye!)
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While the pressure stabilizes, you can check the plasma parameters
- Power: maximum (100)
- Time: 10 (up dial should display 0, bottom dial should display 10)
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Once the pressure is stable start the plasma, when the treatment is finished bring the oxygen flowmeter to 0 (no need to tighten this screw, if it displays 0 then it is closed. Tightening it can damage the flowmeter)
- Close the oxygen bottle
- Shut down the pump, start the ventilation
- Once the pressure is balanced with the atmosphere stop the ventilation, open the door and take your samples
- Replace the glass plate inside and start the pump for a few seconds to hold it closed, shut down the pump, and the plasma cleaner.
- You are done!
Note: plasma treatment wears out with time and in contact with the atmosphere. To achieve best results you can depose a drop of distilled water on one of the inlet/outlet once you chip is closed. If the PDMS is hydrophilic enough the chip should completely fills with water, protecting the plasma.