A micro-valve (10) adapted for integration with a micro-fluidic device such as a micro-injector of a chromatograph, the micro-valve having a first substrate (12), a second substrate (14) having microconduits (36,38) and a seating surface (30), and an actuation membrane (16) positioned between the first substrate (12) and the second substrate (14) for opening or closing a fluid path (48) of the micro-valve (10) under a force applied by a mechanism such as a pneumatic or piezoelectric device, wherein said actuation membrane (16) is constructed from a poly(aryl ether ketone).