Flow through wet/dry membranes?

I obtained some perplexing results today that I have re-run multiple times. Ozone treating w504 permits the passage of water in a wet/dry format w/o PVP coating.

I ran several experiments with the constant pressure device with water on the top side and dry on the bottom. Some of the membranes had once been wet/wet, but I also tested two membranes that had only seen water on one side. All samples produced small droplets of water on the bottom surface within 20-60 seconds (quite similarly to the previous PVP results). I looked at all of these samples previously for pinholes and detected nothing under the 10x objective. Additionally, w504 had only about 10-20% pinhole affected membranes total.

Even more shocking – these membranes continued to pass water once I put them in the fixed rotor centrifuge in 1.5 mL tubes (wet/dry). While the droplets did get pulled off to the side during the spin, the membranes continued to pass water. I decided to test a PVP-treated membrane and found the same thing – continual passage of water. I started and stopped the spin at least four times for multiple tubes. Every time you could see streaks of water across the silicon surface.

I showed this to Jess and she was just as surprised. She confirmed that we have never seen water go through wet/dry ozone or non-ozone treated membranes in the constant pressure device and certainly not in the centrifuge. In my previous experiments, even the PVP-treated membranes would run dry in the centrifuge as the droplets and PVP were pulled off of the surface. We even tried this approach before very unsuccessfully, where we would pipette 20-30uL on the backside before the spin only to find 20-30uL in the bottom of the bucket after many minutes of spinning.

Is there something special about the surface chemistry of w504? Is there anything else that could be happening? I did notice that about 1/3 of the samples have become visibly wrinkled under the microscope and about 1/2 of those visible by the naked eye. But under the weight of the water, and ~2-4 psi there should be no wrinkles, just a slight bowing?

Lastly, the flow rates in the (wet/dry) centrifuge tube were not that bad. The last sample I ran today did about 35uL in 15 minutes at 1500rpm (~4psi) with obviously just the two slits. Wet/wet samples (or constant pressure with a droplet on the bottom side) had flow rates that seemed to be maybe double this, but its tough to say with a small sample size because of variations in porosity. I have a complete data set with all of the possible conditions, but these are the key points.