Wafer silanization
- Before each fabrication make sure all silicon wafers are silanized using chlorotrymethylsilane (TMCS).
- Add 1 mL of TMCS in a small cap and place it inside a container where the wafers are stored. Place the container inside a fume hood for approximately 15 min.
Note: Before first use of a mold, do the silanization process overnight.
- When finished, leave the equipment inside the fume hood for a few more min, to make sure the entire TMCS has evaporated before.
Wafers are now ready to be used.
Fabrication
Introduction
This protocol is about the fabrication of a chip design (flow or control layer). During this procedure you need to make sure that your working place (PDMS lab) is very clean and avoid any distractions in order to not contaminate your materials. Try to minimize the interactions with your colleagues and always wear gloves and a mask.
Materials
- Silicone elastomer kit (SYlgard 184)
- Curing agent
- Vacuum desiccator
- Vacuum pump
- Silicon wafer (mold)
- Regular oven
- Air gun
- Petri Dishes made of glass
- Sterile disposable scalpels
- Aluminium foil
- Scotch crystal tape (19 mm x 32.9 mm)
- Pasteur pipettes plastic - 5 ml
- 0.8 mm hole punch or syringe
- Tweezers
Procedure
- Carefully pour 30 g PDMS elastomer from its container into a clean Petri dish and then, using a plastic pasteur pipette, add 3 g of curing agent into the Falcon (ratio 10:1).
- Using the plastic pasteur pipette mix the mixture well for at least 5 min.
- Using tweezers hold the mold from its edges avoiding the designs and use an air gun to clean it.
- Place it into an aluminum foil (or into a Petri dish made of glass and covered with aluminum foil with a satisfying diameter).
- Place the aluminum foil with the wafer on a straight surface and pour the PDMS mixture on top of the wafer.
- Degas mixture for approximately 25 min inside the vacuum desiccator using a vacuum pump.
- Preheat the oven at 90°C for 5 min.
- Using the oven pan place the PDMS control layer on the mid floor inside the oven and bake it at 90°C for 30 min (make sure that the surface is straight).
- Remove from the oven and using a sharp scalpel cut out the two PDMS designs.
- Place the two designs on a clean surface preferably with holes on it and then create holes for inlets and outlets using a 0.8 mm hole puncher or a syringe (penetrate all the way through the PDMS device).
- Protect PDMS surfaces from dust using scotch tape and store them in a clean Petri dish.