Polymer membranes

A method for the production of a porous polymer membrane suitable for liquid filtration or analyte capture, comprising the following steps:

• providing a flowable composition on a substrate, the composition including photo-activatable monomer molecules, photo-activation initiator molecules and photo-activation quencher molecules;
• providing one or more pulses of laser light to at least one focal point in the composition of sufficient energy to locally polymerize the monomer;
• moving the or each focal point relative to the composition in a continuous or stepwise predetermined manner to a multiplicity of positions and repeating the pulse(s) at those positions such that three dimensional pillars are formed of a size of from 0.1 microns to 10 microns,
• the method further comprising the steps of:
• removing unpolymerized composition, infilling the regions around said pillars with a membrane material, and then removing the pillars from the membrane material, to leave open pores in the membrane material.