Fabrication of free standing membranes and use thereof for synthesis of nanoparticle patterns

Abstract

The present disclosure discloses a method of fabrication of free standing open pore membranes with uniform pore size and shape and ordered pore distribution, and its use for synthesis of nanoparticle patterns. The method includes applying a photoresist layer to the top surface of a substrate, heating the photoresist layer for a period of time, and exposing the photoresist layer to a dose of ultraviolet radiation through a mask having a predetermined pattern. The dose of ultraviolet radiation is controlled in intensity and time and the photoresist layer is exposed such that a top portion of the photoresist layer through which the dose of ultraviolet radiation enters the photoresist layer undergoes greater cross linking than a bottom portion of the photoresist layer immediately adjacent to the top surface of the substrate such that a cross linking gradient develops through a thickness of the photoresist layer. The mask is removed and the membrane is readily detached from the top surface of the substrate since the portion of the membrane adjacent to the top surface is less cross linked than the top surface of the membrane. The detached membrane forms a free standing patterned membrane having a preselected pattern of open pores. The method can be used with positive photoresist materials as well when deposited on a UV transparent substrate so that the photoresist can be exposed to UV from its top with photomask and UV exposure from its back of the transparent substrate without the photomask.