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How to make a PDMS chip
Material used (both from Dow Corning):
- Sylgard 184 silicone elastomer curing agent
- Sylgard 184 silicone elastomer base
- by weight, make mixture base:curing agent of 10:1. For 6 inch wafer, 70g-77g total gives good height to avoid hitting objective on microscope.
- mix gently with glass rod for 10 min
- put mixture into vacuum chamber to get rid of air bubbles inside mixture (1-2 hours)
- Turning on and off the vacuum also helps in eliminating bubbles
- With alumninum foil, create a container around the wafer
- Pour mixture onto the master wafer (gently without generating too many air bubbles)
- If air bubbles are present, blow on it with a nitrogen gun
- Put wafer into over @ 65C for at least 2 hours (overnight preferred)
- Cut carefully the foil off the wafer and pull off the PDMS from the wafer. It is easiest to start at the bottom of the wafer.
- Cut the chips out of the PDMS
- Avoid touching the surface to be bonded (the side with the microfluidic channels, i.e. the bottom) with fingers
To attach the PDMS to glass:
- Clean the glass with soap, DI water, isopropanol, then dry with nitrogen
- Use scotch tape to remove any particles that may be on the PDMS chip. Just stick some tape on to the surface and pull. Repeat.
- Turn the power on the plasma machine
- Put samples in the machine with the bonding face up
- Make sure RF power is in off position
- Close the valve completely
- Turn on vacuum for at least 3 minutes
- Turn RF power to high. Open the vent valve on the door slowly until the plasma turns pink
- Hit the sample with pink plasma for 1 min
- Turn off RF power, vacuum, and main power
- Place glass on bench with bonding surface up. Then place the PDMS on top of the glass. Watch it bond.
- After bonding, apply a bit of force to remove any air that may remain between the PDMS and glass