A microfluidic device includes a microfluidic chamber fluidly coupled to an inlet port and an outlet port, a semiconductor microchip including fluid active circuitry and transistor circuitry, and a bed of solid supports positioned within the microfluidic chamber fluidly positioned between the inlet port and the outlet port. The transistor circuitry in this example provides onboard logic at the semiconductor microchip to control fluid active circuitry. The semiconductor microchip also defines a portion of the microfluidic chamber.