I didn't include this in my article but I did some experiments early on (for a different idea) with air bubbles in oil inside a Teflon coated tube but that presented a lot of challenges (mainly the bubble breaking up) that made it not ideal for something like this.
This can certainly be miniaturized with the right manufacturing techniques but I left that for the future.
This can certainly be miniaturized with the right manufacturing techniques but I left that for the future.