UA Biophysics:Protocols:Microfluidics Valves

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Upper Section (Control Layer)

1. Mix PDMS with curing agent 5:1 respectively (30 g PDMS - 6g Curing Agent) inside a plastic glass and use a plastic fork to mix during 5 minutes
2. Place the mixture inside the degasser for 60 min until all bubbles are gone
3. Pour the mixture over the master
4. Place the master at 65°C for 33 min
5.Leave PDMS for two hours at room temperature

Lower Section (Flow Layer)

1. Mix PDMS with curing agent in a 20:1 proportion (20g PDMS: 1g Curing Agent)
2. Pour only a little PDMS on the wafer
3. Use dirty sticky tape to place the master on the spinner
4. Spin for 1 min at 2500 RPM
5. Place the wafer @ 65°C for 33 min
6. Let the wafer cool down at room temperature for two hours

Thermal Bonding

1. Take both stacks out from the oven
2. Punch holes with 3/4 mm puncher in the upper layer
3. Cut the squares for the upper layer with a new razor blade and clean the chip with magic tape
4. Place the upper layer chips on the lower layer so that rectangles match
5. Place bonded surfaces @ 65°C for 4 hours
6. Cut whole chips from wafer with a new razor blade
7. Punch holes for the flow layer

Last Part of the Process

1. Sonicate chips in isopropanol for 30-40 min
2. Blow, dry and place in oven for 4 hours @ 65°C
3. Sonicate Glass Slides in 1M KOH during 30 min
4. Take slides out from KOH and sonicate them in milliQ water for 10 min
5. Take glass out of water, blow, dry and place in oven for 10 min

Plasma Bonding

1. Use magic tape to clean chips
2. Put glass and chips inside plasma cleaner for 1 min under plasma treatment
3. Take out both and bond them: place PDMS chip upside down and gently let the slide fall on the chip from a 45° angle
4. Make bonding during 5 min @ 150°C in hot plate
5. Leave device overnight so that surfaces recover their original properties

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