A microelectronic package includes a die which may include MEMS and CMOS circuitry for analyzing a fluid. A defined path is provided for channeling fluid to the die. Rather than patterning depressions or physical channels in the package substrate, the defined paths comprise coatings that may channel the flow of liquids to the die for biological sensor type applications. The defined paths may comprise a wetting coating that has an affinity to fluids. Similarly, the defined paths may comprise a dewetting coating the tend to repel fluid surrounding the paths.