Discoloration results from Bernhard Group
The Bernhard group wants to use our membranes to separate pieces of DNA. During their experiments they noticed that some of their samples caused discoloration over the summer. Since then, I’ve been helping a new student to the project, Paul Black.
He first started by testing pH, and found that higher pH leads to fast discoloration. Bill and Paul thought the cause of discoloration may be the dissolution of the oxide layer beneath the membrane. For that reason, they wanted to test a membrane sans pores.
Here’s what we did:
- I gave them samples of 683, which appeared to lack pores according to TEM. Unfortunately 683 has too many pinholes to confirm this with air permeability.
- I also gave them samples from 685, which had pores and was from the same wafer series as 683 (in order to limit questions of wafer similarity when comparing discoloration rate).
- They found that 685 discolored 2x faster than 683.
- If 683 is indeed non-porous, the mechanism of discoloration is a-Si dissolution.
- Increasing pores increases discoloration rate – surface area?