Apple Confirms 2018 MacBook Pro Keyboard Has 'Membrane' to 'Prevent Debris From Entering the Butterfly Mechanism' July 19 2018
Apple has recently revised it's 15" & 13" MB Pro models to include the latest generation Intel processors. Some users will be pleasantly surprised to find their new laptops have dust resistant keyboard thanks in part to a silicone membrane integrated into the key switches. Apple originally filed a patent for a "dust-resistant keyboard" back in 2016, but only is now integrating this feature into their keyboards.
Taken from:
https://www.macrumors.com/2018/07/19/apple-confirms-2018-mbp-keyboard-prevents-debris/