Christian Niederauer/Notebook/RacingBacteria/Protocols/Microfluidics/PDMS

How to Create a PDMS-Stamp from Silicone/Araldite Mold

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