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|The Perils of Hydrophobicity|
Just eleven months ago I was extolling
the benefits of hydrophobic cement.1 And just this
morning I discovered one of the pitfalls of hydrophobic sidewalks.
Just to review, standard concrete is rather porous. It's like Swiss
cheese except the holes are much smaller. One of the downsides to
sidewalks made from porous concrete is that over time and after many
freeze/thaw cycles, the water that seeps into the concrete can lead
to surface scaling and cracks.
That's where hydrophobic cement and sealants shine. By preventing the water from entering into the pores of the sidewalk, scaling is prevented.
Now the downside: If it rains and water droplets accumulate on the hydrophobic surface and then it suddenly drops below freezing before the drops have a chance to evaporate, then the surface becomes layered with slippery small ice balls which, if left unsalted, will lead to slip and fall accidents. I know because I practically took a tumble myself this morning on my neighbor's new hydrophobic sidewalk.
Interestingly, I observed that our old non-hydrophobic sidewalk, while somewhat scaled, was not slippery at all. Careful what you ask for - the solution to one problem can lead to another.
1 See our
February 2021 Newsletter
|Top DROPimage Support Questions|
If you use a ramé-hart instrument that was
made in the last 20 years, there's a pretty good chance that you use
DROPimage software which is now available in three flavors: CA Edition,
Pro, and Advanced.2 What follows are the top five support questions and
our answers. Maybe one of them will help you better run your contact
angle and surface tension measurements.
Q1. When I attempt to measure contact angle, I get 180° for the left and zero for the right contact angle? What's going on?
A1. DROPimage uses the vertical midway point to determine if it should be analyzing a sessile drop or a pendant drop. If the baseline is above the midway point (there is a red tick mark on the left and right sides of the picture window), then DROPimage is looking for a pendant drop and you will get erroneous results if you are trying to measure a sessile drop. See the first tip in this video for more details.
Q2. When I measure the surface tension of water, I get a value below the expected 72.8 mN/m. What's going on?
A2. There could be a number of reasons. The most common problem is the water or syringe is contaminated. Even small trace amounts of contaminants can lower the surface tension noticeably. You will also want to check your calibration (see Q4 below). To review these and nine other tips, check out this video.
Q3. I'm trying to measure contact angle on a reflective surface but snap doesn't seem to work. What do I do?
A3. The algorithm we use for the snap feature, works well in most circumstances. But on reflective surfaces, the actual baseline that snap finds may be too low. This is the result of the drop reflecting on the surface. It's easy to fix. Simply manually adjust the baseline so it passes through the "tips of the football". See this tip in action in this video.
Q4. I'm trying to measure contact angle. It looks like it should be around 45° but when I click measure, I get a value of 89.98. What's going on?
A4. Your calibration is invalid. This can happen if you click in the wrong place when calibrating. If you click on Calibrate > Show Calibration, you will see that the Aspect Ratio is nowhere near the desired value of 1.0000. The fix is to recalibrate your instrument and then check the aspect ratio.3
Q5. I have an Automated Dispensing System, but when I click on Device Control, the Drop Volume Control option is now grayed out. How do I fix this?
A5. If you start up DROPimage and the Automated Dispensing System is turned off, you will get a COM timeout error. The software will then turn off the device to prevent additional errors. (This behavior is the same for the Automated Tilting Base and the Temperature Controller as well.) To fix this, turn on the Automated Dispensing System and then go to Edit > Options and turn on the Drop Volume Control. When you click Okay, it will ask you if you want to install or reinitialize the device; say yes.
2 Note that DROPimage
Standard was replaced with DROPimage Pro in 2020. The Pro Edition
includes all of the functionality that was available in DROPimage
Standard but Pro includes additional tools - e.g., tools to measure
surface and interfacial tension.
|Happy New Year|
As we started 2021, we were happy to have
2020, the year of the pandemic, behind us. Optimistically, we were
hoping the worse was mostly behind us. Now as the highly virulent but
less severe Omicron variant makes its rounds, we're reminded that this
virus will be with us for a while longer. This past year, we've been
plagued with chip shortages, supply chain challenges, and
inflation. Despite these troubles, we've managed to survive and continue
to thrive in a world that has a persistent interest in wetting
properties and surface energy.
As we start 2022, we hope for calmer waters ahead. We wish to thank our employees who have made adjustments to keep our facility safe and operational. We thank our suppliers who have made Herculean efforts to ensure we have all the critical components necessary to make the world's best contact angle goniometers. And, most importantly, we wish to thank you and each of our customers for your continued business. Happy New Year!