Preparation of silicon chips for 2-D polymer transfer

Cutting:

Glossy face down onto Kimwipes, score and break 1 x 4 cm rectangles using the cutting tools in the basement lab (scribing pen + larger tool), then score rectangles forming 1 x 0.75 cm chips. Do not break these chips until after polymerization.

Cleaning:

(Wet cleaning) Attach suction to the bottom of the chip (glossy face up).

Run deionized water and soap over glossy face and clean with cotton (Q-tips) over the glossy face intermittently in same direction to remove contaminants. Blow dry the chips with filtered N2 gas.

Remove suction by turning off vacuum, residual suction will keep chip gently attached. Remove with tweezers and place in a petri dish and cover immediately to minimize exposure.

(Dry cleaning) Place pre-cleaned chips in UV Ozone generator (Refer to instructions for operation of UV Ozone generator) for about an hour to remove residual organic molecules on the surface of the chip.

Silanization:

For chips undergoing top-down transfers it is currently preferred to perform silanization. Carefully transfer silicon chips into desiccator glossy side up, easiest to move the whole microscope slide. Pipette a few drops of distilled trimethylsilyl chloride (TMSCl) solution into an open vial in the desiccator and cover the desiccator with a lid for about 48hrs (weekend) for complete silanization of the chip.

2-D Photopolymerization on the air/water interface.

Detailed instructions for operation of the trough software can be found here.

  1. Turn on the chiller set to 1.0°C. It is located under the computer desk (necessity of this step is under investigation as of 4/30/24)
  2. Remove trough with barriers from container and wash with large amounts of millipore water, rinse with solvent (isopropyl alcohol, semiconductor grade), then rinse again with millipore water. Wash physically with Kimwipes/Q-tips intermittently during this process. Rinse again and dry with N2 gas. Return trough/barriers to the container, close the cover after each piece is cleaned. For a more thorough clean, see instructions here.
  3. If performing a top-down transfer, ensure vacuum is active and connected to the dipper arm. Attach chip glossy face down to the dipper arm at this stage. If performing a bottom-up transfer, place a small Teflon slab to span the trough well. Gently place the chip glossy face up on this piece.
  4. If performing a bottom-up transfer, ensure the trough is oriented such that the two holes on the front face towards the user, then thread a 3 in. syringe needle through one of the holes such that the tip is at least 1 cm in depth in the well.
  5. Compress the barriers to between 3000 and 4000 mm2, then add Millipore water to the trough on the outer sides of the barriers.
  6. Aspirate the surface within the barriers to remove contamination. Be thorough at this stage, many contaminants are removable here.
  7. Flame treat the platinum sensor probe until glowing yellow/white. Once cooled (~10 seconds) return probe to sensor arm and lower the probe into surface of water about 2 mm followed by raising back up by 1 mm. The probe should primarily be in contact with the water via surface tension. Aspirate the surface again here. Adjust sensor position as needed.
  8. Open barriers.
  9. Optional: perform an isothermal compression to test for surface contaminants. If there is a significant rise in surface pressure ( > ±0.3 mN/m2), aspirate the surface again, adding additional water if needed.
  10. Turn off the normal lab lights and turn on the red lamp (located on the high level of the benchtop) then place monomer onto water surface; the exact amount depends on the concentration of carboxyfantrip solution (approximately 80 uL needed at 0.05 mg/ml). Do so by pushing out a drop with syringe then gently touching drop to the surface of the water until all the solution has been added. Add to different areas of the trough surface to ensure maximum spreading.
  11. Allow at least 15 minutes for chloroform solvent to evaporate and the water to come to an equilibrium temperature.
  12. Under the notebook in the trough software (FirmWareX) make sure the film is properly defined. See instructions for this here.
  13. If performing a bottom-up transfer, connect the rubber tubing to the syringe threaded through the trough in step 4.
  14. Change barrier settings to constant pressure and closing speed of 2mm2/min and a final pressure of approximately 12 mN/m2
  15. Once pressure begins to rise, reduce closing speed to 1mm2/min until surface pressure is approximately 12 mN/m2
  16. Allow the barriers to hold pressure constant at 12 mN/m2 for 15 min to anneal the monomer. After resting, STOP the barriers then turn on UV lamp and allow exposure for 5-15 minutes, surface pressure will drop rapidly if done correctly. The Switch for the UV lamp is on the power source located near the trough.

    WARNING: Do not open the trough box while the UV light is active, it is irreversibly destructive to eyes. Eye protection is present in the microscope room and should be used whenever the light is activated.
  17. If performing a top-down transfer, lower the dipper arm until contact is made with water’s surface viewed by internal camera. If camera is unavailable the contact should also result in a disturbance of surface pressure which can be observed. Then raise the dipper arm at 1mm/min while aspirating around the chip. Remove any water droplets adhered to the surface of chip with the aspirator making sure to not touch the chip surface.

    If performing a bottom-up transfer, turn on the aspirator and slowly allow the trough to drain through the well. Allow the chip to fully dry before removing from the trough, water is trapped between the sheet and the chip surface, aspiration will likely damage the chip.
Last modified: May 2, 2024