Using plasma cleaner for bonding microfludicts

Goal

Based on the manual for the Plasma Cleaner/Plasmaflo/Vacuum-pump, here I develope a simple protocol for how to use the Plasma-Cleaner to bond PDMS-microfluidic device to cover-glass.

Procedure

Safety information

1. The Plasma Cleaner is an electrical instrument: to avoid electric shock, plase observe all standard precautions, such as not operating the device near water and operating the device at appropriate libne voltage and frequency.
2. Do not remove panels or housing, except by a certified electronics technician.
3. Do not use the Plasma Cleaner front door when the chamber is under vacuum.
4. Do not use the Plasma Cleaner near flammable materials.
5. Do not plug vacuum pumps whose input electrical current requirement exceeds 7 Amps into the Plasma Cleaner rear vacuum outlet.
6. With respect to vacuum pumps, please refer to the pump user's manual for specific precautions.
7. If oxygen is used as the process gas in concentrations near or above its flammability thresgold, an oxygen service pump must be used.
8. If corrosove gasses are used, make sure the seals and gas connection materials are compatible with the gas. Use a suatable vacuum pump to sercvice corrosove gases.
9. If toxic gases or gases that ionize to toxic products or intermedeiates are usd, the gases must be properly purged from the chamber prior to venting and the pump exhaust must br properly vented. For safe gas handling prcedures specific to your process gas, contact your process gas supplier.

Evacuating the chamber

1. Turn on the Plasma Cleaner main power.
2. Put the sample in the chamber: On the top of small petri-dish, I put one coverglass and one chip with the pattern side-up.
3. Check that the 3-way valve is clesed (level is vertical, manual Figure 12C).
4. Close and hold the front door against the chamber.
5. Turn on the vacuum pump. The vacuum will hold the front door in place. Evacuate the chamber for 1-3 minutes or to the desired vacuum pressure.

Inputing gas

1. Open the 3-way vlave to air or gas (lever points to the metering valve, Figure 12A).

Generating plasma

1. Select the desired RF power level: Used "low" mode today.
2. Look through the viewing window for the plasma glow and indication that plasma has formed .
3. If needed, adjust the metering valve slightly until the plasma intensity is visibly maximized. This broadly corresponds to optimal plasma generation conditions.

Plasma treatment

1. Process the sample for the desired duration. The timing of the plasmia treatment should begin when the plasma glow is first observed.
   • I used \~1 minute.
2. At the end of the process, turn off the RF power.
3. Allow 1-3 minutes for the vacuum pump to evacuate any residual process gas from the chamber.
4. Close the 3-way vlave (lever is vertical, Figure 12C).

Venting the chamber

1. Turn off the vacuum pump.
2. Slowly open the 3-way valve to vent (lever points to vent, Figure 12B).
3. Once atmospheric pressure is reached, close the 3-way valve (lever is vertical, Figure 12C).
4. Turn off the Plasma Cleaner main power.
5. Open the front ddor and remove the sample.

Notes

• Here I do not use the PlasmaFlo
• For the protocol with the PlasmaFlo, see the manual again.

Bonding chips

1. Follow the short protocol without using PlasmaFlo and by only using air, I bonded one 4-channel and one 1-channel chip on the cover-glases.
2. Bake the bonded chip on the hot plate for \~30 minutes.
3. 80 ℃ expected but I realized the plate temperature was \~85 ℃.