A structured film of a semi-crystalline polyolefin and a beta-nucleating agent is disclosed. The structured film has a backing and upstanding posts attached to the backing. At least a portion of the film typically includes beta-spherulites. In some embodiments, the backing is microporous while the upstanding posts have lower porosity. A method of making a structured film is also disclosed. The method includes extruding a melt of a polyolefin and a beta-nucleating agent in the presence of a tool to provide the structured film having upstanding posts on a backing and cooling at least a portion of the structured film to a temperature sufficient to form beta-spherulites. In some embodiments, the method further includes stretching the structured film containing beta-spherulites to provide micropores in the backing.本發明揭示一種半晶質聚烯烴及貝他-成核劑(beta-nucleating agent)之結構化薄膜。該結構化薄膜具有一襯底及附著至該襯底之直立柱狀物。該薄膜之至少一部分通常包括貝他-球粒。在一些實施例中，該襯底為微孔性，而該等直立柱狀物具有較低孔隙率。亦揭示一種製造結構化薄膜之方法。該方法包括在一件工具存在下擠出聚烯烴及貝他-成核劑之熔融物以提供在一襯底上具有直立柱狀物之結構化薄膜及將該結構化薄膜之至少一部分冷卻至足以形成貝他-球粒的溫度。在一些實施例中，該方法進一步包括拉伸含有貝他-球粒之該結構化薄膜以在該襯底中產生微孔。
