That means nothing. Modern actuators are piezo-electric. I have no idea what "ceramic substrate" they are talking about.
The mashable link is just a press kit.
I don't know what is in the RNIB podcast, because the audio is not available to me.
The piezo crystals are the ceramic. This new device claims not to use piezo crystals, and that's why it's smaller.
There's a possibility it's using electroactive polymers in a closed bubble together with latches. This would be much cheaper than piezo systems, and also smaller.
N. Di Spigna, P. Chakraborti, D. Winick, P. Yang, T. Ghosh and P. Franzon, “The Integration of Novel EAPBased Braille Cells for Use in a Refreshable Tactile Display,” Proceedings of the 12th International Conference on Electroactive Polymer Actuators and Devices, San Diego, March 2010, p. 9.
https://audioboom.com/posts/5655817-the-first-braille-smartw...
They include interviews with blind people who've tried it.
They say that it's smaller, lighter, and cheaper because they use a new type of actuator that isn't "on a ceramic substrate".
The company plans to ship its first 150,000 devices by the end of the year for £300; the dot mini is an educational braille reader planned for sale for £650.
Here's a mashable link saying the product is shipping: http://mashable.com/2017/02/22/dot-smartwatch-retails/#c8Hyx...