====== Microfluidics ======

===== Jonathan's PDMS procedure (adapted from Arthur) =====

=== PDMS prep ===
Mix PDMS 10:1 with hardener, stirring for a minute.

To remove bubbles, place in dessicator, pump down.  If PDMS looks like it will foam over, bleed air into the dessicator.  Shaking the dessicator a little will help to pop the bubbles.  When there are no more bubbles, and the liquid appears transparent, this step is done.

Pour or spin PDMS onto template wafer.  To cure at room temperature, it may a few days.  To speed this up, bake at 80 degrees C for ~1 hour.

=== PDMS transfer and binding ===

Depending on your procedure, you may use a razor blade to cut out a portion of the PDMS to transfer to your final substrate...

Heat a hot plate to 70 degrees C, for use later.

Place your PDMS piece-to-transfer upside down, and the substrate face up into the lab's plasma cleaner.  (Only do this if there are no nanotubes or graphene, which the plasma will destroy.)  You can cut a piece of glass slide as a shelf to hold the pieces close to the center of the plasma etcher's barrel.

Make sure the oxygen tank is open (but don't yet open the oxygen inlets to the plasma cleaner).  With the lid off the plasma cleaner, gently open the vacuum line until you can hear some air flow.  Place the lid on the plasma cleaner.  Open the vacuum line the rest of the way.  Open both oxygen valves and purge the system by flowing oxygen for ~30s.

Turn off the room lights, so that you can see the plasma through the holes in the metal casing.  Close the oxygen bleed valve. Turn the plasma on high, watching for it to ignite.  This may take 10-15s.  Once it ignites, increase the flow of oxygen to ~150 on the flow meter.  Turn the plasma off after 5s.

Close the oxygen valves.  Close the vacuum line valve.  Bleed air into the system with the bleed valve in the back of the plasma cleaner, holding the plasma cleaner's lid so it doesn't drop.  Remove samples.

Place cleaned PDMS on device substrate, aligning if necessary.  The PDMS should stick itself down.  If it needs a little help, gently tap the PDMS near the area that is already stuck down.  Once adhered, place on hotplate for 5 minutes at 70 degrees C.

Once bound, it should be very hard to remove the PDMS without ripping it.

===== Making a Ag/AgCl Electrode =====

- Leave the Ag electrode in bleach (just general purpose bleach) for ~5min 

- Wipe off the electrode

- Prepare 10X dilute HCl solution

- Applying a bias of -1V on a Pt electrode and 0V on the Ag electrode, place both in the solution for ~2minutes. 


The Ag electrode should have a dark gray film on the surface where it was exposed to the HCl solution. This process deposits chlorine onto the Ag electrode while bubbling off hydrogen gas on the Pt electrode (which is visible during the process). 
