Protocol for Making Gradient Solution Using Microfluidic Device

Nadia ZAARI 05/30/02

Biomimetic Materials Engineering Lab

Pr. Joyce WONG

Protocol for making gradient solution using microfluidic device

Step 1 through 4 need to be performed in the clean box.

1. Cut the PDMS stamp with razor blade out of the Si Wafer (be careful when cutting not to break the Si wafer)

2. Place PDMS stamp with microfluidic pattern facing up in the box

Note: at this time you should refill the petri dish with PDMS to avoid exposure of the Si wafer to air contamination. (10:1 PDMS to curing agent)

3. Punch hole into the inlet (from the patterned side to the non patterned side) with pipetting 18G needle.

Cut the end of the PDMS stamp so that the outlet channel is open to the air when placed on the glass slide

4. This step is to achieve an irreversible seal between the glass slide and the stamp.

Put the PDMS stamp and a glass slide cleaned with ethanol and with no dust in the chamber.

Set the power to medium, turn on the plasma etcher and then turn on the vacuum pump (the vacuum pump isn’t turned on at the beginning because we don’t want a high vacuum that would result in a strong plasma etching).

Stop the pump and the plasma etcher 30-40s after the plasma has formed (pink/violet glow).

Assemble the 2 surfaces and apply some pressure (with back of a needle for example) on the PDMS stamp.

5. Cut with a blade 3 pieces of tubing around 10cm each

6. Prepare the epoxy glue. Use a 9” Pasteur pipette to mix the 2 components.

7. Place the tubing in the inlets and seal with the epoxy glue using the Pasteur

pipette.

8.  Let the glue dry for around 10 min.

9.  place microfluidic device on microscope stage

10.  Fill in Hamilton gastight syringes ( 0.5mL or 1mL…) with the appropriate solutions

11.  Place syringes in pump rack and align manually the plungers

12.  Adjust height of the pump with the jack so that the tubing and the syringes are at the same level

13.  Connect the tubing to the needles.

14.  Set flow rate at 50mL/min and flow solution in the tubing until it reaches 1cm

before the inlets.

15.  Set the flow rate at 5mL/min 1cm before the inlets and let the solution flow

until gradient establishes in the outlet channel.

16.  To get rid of the bubbles in the outlet channel, tap gently on the outlet channel or increase the flow rate.