Chemistry Reference
In-Depth Information
SU-8 Masters
The following is the recipe for making masters in SU-8 in the clean room.
1. Wash the silicon wafer in Isopropanol and blow dry with nitrogen
2. Heat at 200
◦
C for 10min
3. Spin coat SU-8 100 (for a thickness of 100-120
µ
m, adjust the spin speed to
1400 RPM)
4. Pre-softbake at 65
◦
C for 15min
5. Softbake at 95
◦
C for 40min
6. Expose for 30 s at 15mW, 365nm in HP contact mode. Wait for 1min. Expose
again for 30 s.
7. Pre postbake at 65
◦
Cfor1min
8. Post bake at 95
◦
Cfor8min
9. Develop for 8-10min in SU-8 developer
10. Sonicate for 3-4 s and wash with acetone followed by isopropanol.
PDMS and Assembly of Devices
1. PDMS (Sylgard 184) with cross linker in the ratio of 10:1 is poured over the
silicon master.
2. This is degassed in the desiccator to remove bubbles. (Degas until the PDMS
layer is completely free of bubbles)
3. Cure PDMS at 85
◦
Cfor4h
4. Cut the PDMS mould around the structure and peel off from the master.
5. Punch holes for the inlets and outlets.
6. Wash the PDMS layer and a cover slide with isopropanol and place in plasma
cleaner.
7. Plasma clean at HIGH for 30 s to 1min
8. Bond the PDMS to the glass by immediately bringing the two in contact and
pressing lightly, making sure that no air is trapped in between.
Ag/AgCl Electrodes
1. Acleaned silver wire (diameter 100-300
µ
m) is placed in a non-metallic container
containing 150mM salt (NaCl) solution.
2. The silver wire to be chlorided in the (
) positive terminal of a power supply and
the other electrode (another silver wire) to the (
+
) negative terminal.
3. The chloriding electrode darkens, while the other bubbles. Continue until the
darkened surface is evenly coated.
−
