11 July 2008

What was done

We did a continuation of what we did last week which is to make our own micro channel chips.

Before doing anything to the glass pieces which had been left in the lab for a week, we had to heat up the glass at a temperature of 280 degrees Celsius for 10 minutes. This is to prevent any contamination that might have been on the glass pieces and also to ensure the ‘stickiness’ of the glass for the spin coating later on. We also heat up a small beaker at the same conditions for the same reasons.

The SU-8 was then poured into the beaker ,after it had cooled down, to about ¾ full. Following that, the SU-8 was then put in small quantities onto the glass pieces for the spin coating. After spin coating, the glass pieces were then for soft baking.

The recommended program for chemical SU-8 2025

Spin coating
Based on the dimension of our glass piece, 4-5mL of SU-8 was poured with slight excess onto the glass piece as the recommended volume to be poured on to the glass is 1ml per 25mm. Spin coat the glass piece twice with the first one at 500rpm for 5 to 10 seconds with an acceleration of 100rpm/second and the second one at 3000rpm for 30 seconds with an acceleration of 300rpm/second.

Soft baking
It is best to bake on a lead hotplate with good thermal control and uniformity.
For the size of our glass piece, it was bake at a temperature of 65 degrees Celsius for 0 to 3minutes then at 95degrees Celsius for 5 to 6 minutes.

NOTE: After removing the glass piece from the hotplate, be careful of the hot glass pieces. Allow the glass piece to cool. If wrinkles appear, soft bake the piece again at the same temperature at 5 minutes interval. Repeat until there are no more wrinkles on the glass piece.

Problems

There is only 1 problem, which are the air bubbles in the SU-8. We will try to solve the problem but we have not encountered any big problems till date as our SU-8 coating is very thin. Our problem may or will arise in the latter part of this phase when dealing with a much thicker coating

Conclusion

Though this week’s experiment might have been a short session, it was worth noting that we familiarized ourselves with the same equipments we used at the start of our FYP research. Also, we cannot proceed on with the making of the micro channel chips as the chemicals needed for developing the glass pieces are still not ready. Hopefully, the chemicals will be ready next week. If not, we can always start again with the PIV equipment.

This is still early of part of our development of using SU-8. By having this experience from these 2 weeks, it will be a stepping stone for to learn more about this chemical and how to handle it properly. This is because this is our first time handling with this chemical. By having this experience we can also predict what problems it may occur.
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