Don't ferrofluids break down in to the surrounding liquid over time? Or is that mitigated by treating the glass as was mentioned in the bluetooth speaker video from the article?
Ferrofluid has been used in certain high end speakers for quite a while, it can break down or dry out eventually but generally lasts well over a decade in that application.
The glass treatment is just to prevent the ferrofluid from sticking.
Thank you. I remember seeing someone had made a clock face using ferrofluids, and wanted to give something like that a go myself, but was put off hearing the information I was questioning.
The smaller detail that really clinches it here is suspending the ferrofluid in another fluid. I have seen at least one of the clocks, and the ferrofluid doesn't behave nearly as nicely in air.