Abstract: A coating device has a first half and a second half located adjacent the first half to form a slot between the first and second halves. A porous material, having a thickness greater than the height of the slot, is disposed in the slot to compress uniformly along its width. The porous material has a porosity and a height selected in combination with each other to create a predetermined pressure drop through the slot and to maintain the pressure drop to create the desired flow rate along the slot width. The size of the pores in the porous material can be less than 25 .mu.m and the exit pressure drop through the slot can be at least one thousand times greater than could be obtained without the porous material.

Abstract: An electrospray coating head system for applying thin coating to a substrate comprising a slot or blade to meter a liquid onto a shaping structure which forces the liquid to have a single continuous and substantially constant radius of curvature around the shaping structure. A voltage applied to the liquid around the shaping structure causes the liquid to produce a series of filaments which are spatially and temporally fixed, the number of filaments being defined by a simple adjustment in the applied voltage. The filaments break up into a uniform mist of charge droplets and are driven to a substrate by electric fields to produce a coating.