Doped aluminum oxide layers having a porous aluminum oxide layer and methods of their fabrication. Such manual input interfaces may provide tactile feedback to a user. The tube is attached to the body and in fluid communication with the tube aperture. 3, M is a metal selected from among Nb, Ce, W, Mn, Ta, Pd, Pt, Ru andor Rh, c is from 0. The combustion is thereafter controlled resonantly at high frequency and the metal is heated to a molten state.