QC on Dual Scale Membranes (Lot 1383)

ByDan Ahmad

Recently we have received dual scale (nanoporous and microporous) membranes from SiMPore at two porosities: 0.625% and 1.25%. These feature 3 µm circular pores (Lot 1383). We routinely perform QC checks on membrane deliveries, so the following is report on this delivery.

First, I’d like to note that we were supposed to receive equal amounts of both 0.625% and 1.25% porosity membranes, however there appears to be a mix up in the labeling. A box labeled 0.625% actually contains all 1.25% membranes (with the exception of one; Figure 1). This means that we actually have about 11 membranes at 0.625%, and about 60 at 1.25%.

Figure 1: The three boxes on the left are 1.25% porosity, the one box on the right is 0.625% porosity.

Most of the membranes were clean (Figure 2), and any instances of debris were limited to small particles in the single digits (Figure 3).

Figure 2: Examples of clean membranes (10x). The circular artifacts are debris on the lens, while the darker gray splotches in Figure A is PDMS in the background. Figure B was taken on a glass slide, outside of the gel box, hence why there’s no splotches in the background.
Figure 3: Examples of debris found on the membrane. Prior experience with microplastics isolation has taught us that these bits of debris can easily be washed off with 200 proof ethanol (Koptec).

Sometimes a strange debris pattern appears when changing the plane of focus (Figure 4). This is not inherent to the membrane itself, its actually on the PDMS layer in the gel box.

Figure 4: Strange debris that appears on the gel layer in a storage box. This is not on the membrane itself.

Here’s a video showing how changing the plane of focus makes this artifact appear.

DSC_0306

Here’s the same membrane removed from the gel box, now on a glass slide. The only artifacts seen are from the microscope itself.

Figure 5: The membrane from the above figure but now isolated on a clean glass slide. Here the only artifacts are from the microscope itself.

Lastly, in terms of manufacturing, some of the membranes have off centered pores (Figure 6). In severe cases this may effect porosity, but in the case of this shipment no major deviations were observed.

Figure 6: Off centered micropores.

Overall the membranes are clean and ready to be used straight from the gel box (only about 4 or 5 had any sort of debris on them). The only other considerations we may wish to evaluate in the future is staining with nile red (checking for PDMS encroachment on the membrane surface).

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