  Robust nanoporous polymer films with approximate 100-nm thicknesses would be
broadly applicable in technological areas such as flexible sensors, artificial
skins, separators, antireflection and self-cleaning films. However, the
creation of these films has been extremely challenging. To date, all reported
ultrathin films are of insufficient mechanical strength for use without
substrate supports. We describe here the fabrication of a new ultrastrong and
highly flexible ultrahigh molecular weight polyethylene (UHMWPE) 100-nm porous
membrane. Scanning and transmission electron microscopy evaluations of film
microstructures reveal a planar fibrous structure with randomly oriented
polygonal interconnected pores. Moreover, the tensile strength of this film is
twice as strong as that of solid stainless steel, with a measured in-plane
tensile strength and ductility of approximately 900 MPa and 26%, respectively.
We further coated our newly developed film with a monolayer graphene to invent
an optically transparent and fully conformable piezoresistive skin sensor and
thus demonstrated a potential application.
