 A new technique has been developed to create nanoporous polymer membranes with well-defined average pore diameters. This technique involves heating highly entangled polymer films to a high temperature and then rapidly cooling them down below their glass transition temperature, TG. The resultant membrane displays remarkable elastic properties and can be used in applications such as gas separation, filtration, and drug delivery. This article was authored by Sia-Ping Su, Manjesh K Sing, Yu Tsong, and others.