The present invention provides improved synthetic polymer hydrogel permeation layers for use on active electronic matrix devices for biological assays. The present invention includes methods for forming a permeation layer on an array of microelectrodes including the steps of attaching a linker to the surface of the array and providing a polymerization solution that includes a porogen. The surface of the array is then contacted with the polymerization solution and the polymerization solution is then polymerized on the surface of the array to form a permeation layer that is attached o the surface of the array through the linker. The porogen is then removed from the permeation layer, thereby creating void spaces in the permeation layer.