SU-8 Surface Modification

Last summer, I attempted to modify the surface of SU-8. The purpose of the experiment was to covalently bond poly(ethylene glycol) (PEG)  to SU-8, which would be useful when the SU-8 is used as a scaffold on the membranes. The method of surface modification was derived from the attached article, which can be found here.   The protocol involved a sulphochromic solution with a catalyst, K₂Cr₂O₇  For my setup, I only used sulfric acid.

The steps are as followed:

1. Rinse with IPA and dry
2. 30 seconds in sulfuric acid
3. Rinse with DI water
4. Dry in oven

From here, the steps varied based on what I was doing at the time. Last summer, I was attempting to covalent bond PEG to the SU-8 surface so the SU-8 was modified again using 3-(trichlorosilyl) propyl methacrylate (TPM) surface modification. This attaches an adhesion molecule when PEG is crosslinked.

For TPM:

1. 5 minutes in toluene+TPM solution (10 mM TPM in toluene)
2. Wash with DI water
3. Dry

The PEG structures was crosslinked onto the continuous film of SU-8.  The sulfuric acid was not enough only to for bonding. The TPM surface modification was also needed. The PEG structures were left in PBS 1x for 96 hours and were agitated once in a while to determine whether it was still bonded to the SU-8. The picture below was one of the PEG structures fabricated.

For PDMS bonding, the SU-8 was not further modified with TPM. So far, there are two tests; untreated and treated with sulfuric acid. The Corona wand is used on the PDMS, and the setup is placed in the oven. Below are the two samples. On the left is the untreated and on the right is the treated SU-8. Right now, an adhesion test needs to be implemented to determine whether the sulfuric acid improved the bonding.