Systems comprising electromagnetic radiation source; dielectric contrast analysis structure comprising: bulk dielectric substance and a plurality of receptacles in the bulk dielectric substance, wherein the plurality of receptacles allow a material to flow through the receptacles from a first side of the bulk dielectric substance to a second side of the dielectric substance; first flow line connected to the first side of the bulk dielectric substance; second flow line connected to the second side of the bulk dielectric substance; flow path for the material comprising the first flow line, the plurality of receptacles, and the second flow line. A flow path for a material to flow through the receptacles; a first pressure sensor with the first flow line; a second pressure sensor with the second flow line; and an electromagnetic radiation detector, wherein the dielectric contrast analysis structure is between the electromagnetic radiation source and the electromagnetic radiation detector.