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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
  1. 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.
  2. mix gently with glass rod for 10 min
  3. 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
  4. With alumninum foil, create a container around the wafer
  5. Pour mixture onto the master wafer (gently without generating too many air bubbles)
  6. If air bubbles are present, blow on it with a nitrogen gun
  7. Put wafer into over @ 65C for at least 2 hours (overnight preferred)
  8. 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.
  9. Cut the chips out of the PDMS
  10. Avoid touching the surface to be bonded (the side with the microfluidic channels, i.e. the bottom) with fingers

Plasma bonding

To attach the PDMS to glass:

  1. Clean the glass with soap, DI water, isopropanol, then dry with nitrogen
  2. 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.
  3. Turn the power on the plasma machine
  4. Put samples in the machine with the bonding face up
  5. Make sure RF power is in off position
  6. Close the valve completely
  7. Turn on vacuum for at least 3 minutes
  8. Turn RF power to high. Open the vent valve on the door slowly until the plasma turns pink
  9. Hit the sample with pink plasma for 1 min
  10. Turn off RF power, vacuum, and main power
  11. Place glass on bench with bonding surface up. Then place the PDMS on top of the glass. Watch it bond.
  12. After bonding, apply a bit of force to remove any air that may remain between the PDMS and glass