A splash-proof lid for a drinking cup has a splash guard in the form of a semi-permeable membrane positioned between the liquid contents of the cup and a discharge opening of the lid. The splash guard inhibits the liquid from splashing out of the discharge opening, while permitting the liquid to flow...http://www.google.com/patents/US20020038803?utm_source=gb-gplus-sharePatent US20020038803 - Splash-proof lid for a cup
