The present invention is based on the development of a dual promoter system for the efficient intracellular synthesis of viral RNA. The device includes a mould, a sheet holder and a die, with which the metallic substrate is formed to produce a drawn test surface. The filter assembly can include a particulate filter portion for removing physical or particulate contaminants, a chemical filter portion for removing chemical contaminants, or can have both portions. The coil elements may be generally circular or rectangular in shape, or can have other shapes, and they may have different sizes from one another. By adapting models already available to the new environment, the system does not need separate adaptation training data.