DIY electrowetting on a hydrophilic surface

[HelloCthulhu]

TL;DR Summary

And after reading this paper, I thought testing the electrostatic repulsion of water on a hydrophilic surface would be an interesting experiment. I'd like to see if the water droplet starts dispersing into smaller droplets or not.

https://iopscience.iop.org/article/10.1088/0953-8984/17/28/R01

Even as a layman, I've been fascinated with the structure and activity of water for years. And after reading this paper, I thought testing the electrostatic repulsion of water on a hydrophilic surface would be an interesting experiment. I'd like to see if the water droplet starts dispersing into smaller droplets or not. Here's a snippet of the affect I'd like to get close to recreating:

https://iopscience.iop.org/article/10.1088/0953-8984/17/28/R01

pg. 21, Fig 13

"In the same publication, Vallet et al [31] also reported another phenomenon that occurred only for low conductivity liquids (deionized water and water–ethanol mixtures). For these liquids, the contact line was found to become unstable at high voltage leading to the ejection of small satellite droplets from the edge of the main droplet with a characteristic lateral spacing. This observation was later reproduced by Mugele and Herminghaus [54] for mixtures of water and glycerol (see figure 13). Qualitatively, this instability is due to the mutual repulsion of like charges at the contact line. Beyond a certain threshold voltage, surface tension can no longer balance the electrostatic repulsion and the emission of satellites sets in."

I have distilled water. A digital pipette that can dispense samples as small as 0.1 μL. Adhesive microscope slides. Copper plates I can shape and use as electrodes. A high voltage AC/DC power supply (≤15kV) and it's worked really well for 100 mL water bridge experiments so far. Only thing I don't have yet are lab grade glycerol or silicone oil.

Here's a diy electrowetting setup from Gaudi Labs:



I think they're using silicone oil and oil ink in this demo.

I'd like to just try a sample of 10 mL distilled water on a hydrophilic glass slide with two 10 mm x 10 mm copper electrodes underneath to start and see if any deformities occur during high AC or DC voltage. Any advice is greatly appreciated!

 

[member38644]

First of all, it's great to hear that you are interested in exploring the phenomenon of electrowetting on a hydrophilic surface. It is indeed a fascinating area of study and has many practical applications in fields such as microfluidics and lab-on-a-chip devices.

Based on the information provided, it seems like you have most of the necessary materials to set up a DIY electrowetting experiment. However, there are a few things to consider before getting started.

Firstly, it's important to note that the paper you referenced is discussing experiments with low conductivity liquids, such as deionized water and water-ethanol mixtures. This means that using distilled water may not yield the same results as the ones shown in the paper. It would be best to use a low conductivity liquid, such as deionized water, for your experiment.

Secondly, it's important to ensure that your setup is properly insulated and that there are no leaks or gaps where the high voltage could escape. Safety should always be a top priority when working with high voltage equipment.

Additionally, the electrode size and spacing can also affect the results of the experiment. The paper mentions using electrodes with a diameter of 10 mm and a spacing of 10 mm. You may want to consider using electrodes of similar size and spacing for your experiment.

Finally, it would be best to start with a lower voltage and gradually increase it to see the effects on the water droplet. This will help prevent any potential damage to the equipment or the sample.

In terms of advice, it would be best to follow a protocol or guide for setting up the experiment, as it can be a bit complex. You may also want to consult with someone who has experience with electrowetting experiments for further guidance.

Overall, DIY experiments in science can be a great way to learn and explore new concepts, but it's important to prioritize safety and carefully plan and execute the experiment. Good luck with your experiment!