NOVELTY - Producing a nanoscale membrane involves: applying a nanoscale film to one side of a substrate; masking an opposite side of the substrate; and etching the substrate from the masked opposite side of the substrate to form a passage through the substrate and exposing the nanoscale film on both sides to form the nanoscale membrane.    USE - For producing a nanoscale membrane useful in a structure; a sensor (e.g. pressure sensor, piezoelectric, or piezoresistive sensor); and in a device for supporting a product during electron microscopy (claimed).    ADVANTAGE - The single-side etching procedure uses a different etching chemistry that allows a membrane formed of any material(s) to be locally released from the substrate with a single etching step, forming square edge-bound membranes. This greatly simplifies processing requirements because (i) for silicon dioxide films, this material is generally more accessible and easier to pattern and remove than silicon nitride; (ii) potassium hydroxide (a restricted contamination source in most clean rooms) is eliminated; and large area ultrathin (less than 100 nm) membranes are formed with a single etching step requiring no additional thinning. The modified single-side etching procedure is able to prepare membranes having a thickness of less than about 10 nm, and having high aspect ratios; and avoids the need for mechanical polishing steps or ion beam etching procedures, which can cause damage to planar films in some circumstances.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a nanoscale membrane exposed on opposite sides have an average thickness of less than 100 nm, and a lateral length to thickness aspect ratio not greater than 10000:1, the membrane formed of a material selected from semiconductor materials, non-conducting materials, metals, organic polymers, optical coating materials and/or dielectric coating materials;    (2) a structure comprising a support, and at least one nanoscale membrane bound at its outer edges to the support;    (3) a fuel cell comprising the nanoscale membrane;    (4) a sensor comprising the nanoscale membrane;    (5) an electrospray device comprising the nanoscale membrane;    (6) a device for supporting a product during electron microscopy, and comprising the nanoscale membrane;    (7) a method of forming shaped nanoscale products; and    (8) a method of performing transmission electron microscopy.