Unless the cut is so deep that penetrates the first layer of the Magic Touch, the function will not be affected. It can be cleaned by regular glass cleaner, such as Windex. DO NOT spray the liquid directly to the screen. Magic Touch is made by resistive technology and it will soon be available with capacitive technology. The resistive technology is the most popular one because it provides the highest touch resolution, fastest touch response and can be activated by anything.
Capacitive technology requires skin contact to operate.
Those types of touch screens cannot be activated by sharp object, not even the fingernails. Therefore, there is much less chance to get scratched by the users. However, they still can be scratched, and once that happens, the screens will no longer function correctly. This statement was true - about 10 years ago when the material technology was still not fully developed. With today's material and coating technology, there is not much difference any more.