iFixit was the first to find out that the redesigned model of the Apple MacBook Pro keyboards had a membrane underneath the keycaps. A leaked Apple repair document confirmed that the use of this membrane was to help stop undesirable dust and debris from harming the delicate mechanism. However, after running enough tests, the membrane has been found to be able to stop dust from getting into the keyboard.
When iFixit was running some tests on the keyboard, they poured a fine, powered paint additive on the device in order to check if the membrane was really able to block dust or if it was only put there to reduce noise. The image that was sent to us revealed that the membrane appears to be highly effective at keeping the paint powder away from the middle area of the device. iFixit noted that they ran tests on the old keyboard that had no membrane and they found that it could not withstand the debris. Be that as it may, the new keyboard still could not be protected against more grit particles such as sand, translating to the fact that you cannot use the MacBook Pro anywhere sandy such as a beach.
According to the investigations that were carried out later by iFixit, one of the reasons why the new keyboard is effective in blocking out dust is that the membrane is in fact a solid sheet of silicone that has cutouts for individual keys thus making it difficult for dust to penetrate it. The investigations also showed that the keycaps are much thinner than those of the earlier version, and this made them easier to remove whenever the need arises to get rid of dust beneath the keys which is good because in the previous model, the spacebar proved difficult to remove without the possibility to destroy the key.