I previously wrote about an experiment published in the Journal of Chemical Education called “Hydroglyphics”1. In this experiment, portions of a Petri dish (which is composed of hydrophobic plastic) are exposed to electric sparks from a Tesla coil. The parts of the Petri dish treated with electric sparks become hydrophilic, due to reaction of the plastic in the Petri dish with oxygen. By protecting certain regions of the Petri dish from the sparks, hidden patterns can be developed that emerge when the treated Petri dish is exposed to water (Figure 1).
Water collects on the (hydrophilic) regions of the dish that were exposed to sparks, but avoids the (hydrophobic) regions of the dish protected from the sparks.
This is a fantastic experiment that I have successfully used in outreach events, at science camp, and in the classroom. However, this experiment requires the use of a Tesla coil, which costs around $200.
A student of mine (Jon Gurka) and I have come up with a way to do this experiment for around $20. This less expensive version of the Hydroglyphics experiment makes use of Rust-Oleum NeverWet.
NeverWet is a liquid repelling barrier that can be applied to many different surfaces. I bought some at Home Depot for under $20. Application of NeverWet to a surface requires two steps: application of a base coat and subsequent application of a top coat. NeverWet coating is composed of dialkylated silicon polymers and/or nanoparticles2, which display superhydrophobicity3,4. Jon and I decided to experiment with NeverWet applied onto T-shirts. Check out some of our results in the video below.
In this case, the portions of the T-shirt protected from the superhydrophobic coating absorbed water, while the water beaded up on the coated portions of the T-shirt. We simply applied foam stickers to spell out “CHEM IS COOL” on the T-shirt prior to applying the NeverWet as directed. Wouldn’t this be a fun way to teach students about hydrophobicity and hydrophilicity? What kinds of interesting experiments can you design that use NeverWet? I look forward to hearing from you!
Acknowledgement: Thanks to Jon Gurka for help with experiments and introducing me to NeverWet.