PEG Microarray Developments

Updates: We can now put the glass on top of the mask, which allows the use of nonstick agents in the creation of PEG microarrays.

The ability to cross-link PEG-Diacrylate (PEG-DA) with a photoinitator and UV exposure was previously tested and shown to work. At the lowest power setting on the Leica (~25%) fluorescence source, we were able to cross-link PEG in the open regions with minimal cross-linking in the dark regions of the mask. We have been successful creating features with heights of approximately 100 and  300 microns. Thickness is controlled using silicon gaskets cut using a computer controlled knife cutter and confirmed using the z-axis on the microscope. We plan to use fluorescent beads to more easily judge focus points.

Challenges associated with this technique are the adherence of PEG onto the substrate and the cross-linking of PEG through the dark parts of the mask, into the features. Currently, PEG will minimally adhere to the bottom coverslip when the top coverslip has been treated with Rain-X. The use of trichlorosilyl-propyl methacrylate (TPM) to modify the surface will allow firm PEG adhesion. These modifications combined should produce desired results when the top coverslip is peeled from the cross-linked PEG structure. To address the cross-linking through features, light intensity and exposure time both will be considered based on proposed thickness, to achieve a uniformly featured mask. Additional control experiments are required to determine individual optimal times and intensities. Pictured: 300 micron thickness

The desired result of adherence to the glass cover slip allowed the move to the use of polycarbonate membranes. The opaqueness of the filters requires them to be above the PEG to allow the UV light through. PEG is showing to more readily adhere to Rain-X treated glass than the unmodified membrane. The next step is to attempt to modify the surface of the filter without affecting the porosity.