Christian Niederauer/Notebook/RacingBacteria/Protocols/Microfluidics/PDMS
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How to Create a PDMS-Stamp from Silicone/Araldite Mold
Why PDMS? -> PDMS is optically clear (good for microscopy!), and, in general, inert, non-toxic, and non-flammable.
Preparation of PDMS mixture
- with pipette boy and 5ml stripette pour ~4g of elastomer into a (clean) cup
- with micropipette (1000µl) add one tenth of elastomer mass (~0.4g) of linker fluid to the cup
- mix well with stripette
- degass for 30min-60min
Preparation of PDMS membrane
- pour degassed mixture onto wafer placed in petri dish with aluminium foil
- pour just enough to cover the waver
- use Leveling Petri Dish to ensure constant thickness
- araldite wafer: cure it for 3-4 hours in oven at 60°C
- silicon wafer: cure it for 2 hours in oven at 80°C for
- peel off membrane from wafer surface with forceps
- cut out the pattern but leave enough space around it
Final Processing
- punch holes with 2mm coring tool at the desired connection points under dissection microscope (tip: target the hole with coring tool under microscope, then put the stamp onto one finger with alufoil between stamp and finger and push/turn until you feel the coring tool on your skin)
- plasma clean the treated face of the stamp and a coverslip and press them together with alufoil in order to prevent contamination
If the stamp is too thin
BEFORE PUNCHING HOLES
- take a slice of PDMS with bigger or same area than the stamp
- plasma clean unshaped face of stamp and extra slice and stick them together
- now punch desired holes with 2mm coring tool
How to clean the PDMS cup
- scratch out all solid PDMS residues with forceps
- use tissue to clean out crudely
- pour pentane into the cup and gently sway the cup
- clean out with water and let dry
How to clean dirty stamp
- let the stamp soak in ethanol
- use forceps and (with caution) submerge the stamp into a jet of water
- let dry on clean alufoil