PDMS processing & devices. 2 nd master PDMS 1 st master PDMS control channel active channel PDMS 3...
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Transcript of PDMS processing & devices. 2 nd master PDMS 1 st master PDMS control channel active channel PDMS 3...
2nd master
PDMS
1. Substrate: anything smooth and flat silicon is the easy choice
Surface preparation:-bake adsorbed water vapor out-clean: remove particles -adhesion promotion: HMDS
Adhesion promotion
HMDS More hydrophobic surface,Better adhesion with resist (which is organic polymer)
Resist processing
Resist dispensing Acceleration Final spinning 5000 rpm
(a few milliliters) (resist expelled) (evaporation/partial drying)
PDMS processing
Pre-polymer and curing agent
10:1 ratio
Mixing bubble free
Casting
Curing, e.g. 65oC, 2 h; or 40oC 10 h
PDMS propertiesTg Tdegr CTE Ther UV-
transparencyconduc
0C oC ppm/oC W/K.m
PMMA 100 200 70 0.2 opaque
PC 150 230 65 0.2 >350 nmPDMS -130 400 300 0.15 >240 nmSU-8 240 340 100 0.2 >350 nmPolyimid400 620 3-50 0.2 opaqueParylene 150 290 35 0.1
>300 nmTeflon 130 330 100 0.1 opaque
PDMS Young’s modulus 10 MPa very elastic, peels off easily
Release
Release criteria:
-no retrograde angles-smooth surfaces-low surface energy-no interfacial reactions
Masters
•photolithography of SU-8•photolithography and silicon etching•photolithography and metal electroplating•discharge machining•laser machining•mechanical milling•natural objects
PDMS
3rd substrate
Thin PDMS
What is thin ?
10-50 µmSpin coating
Applicable to viscous polymers
Typical thickness: 1-100 µm
Casting: 100 µm to mm’s
PDMS
3rd substrate
PDMS bonding
Self-adhesive bonding ?
Need strong bond for a valve application.
Oxygen plasma activation
Reactive OH-groups on surface permanent bonding