An example system includes a primary channel having a first end and a second end, at least two reagent reservoirs coupled to the first end, and a controller. Each reservoir contains a reagent in a fluid solution and is associated with an integrated pump to drive a reagent droplet from the corresponding reagent reservoir into the primary channel towards the second end. The controller is coupled to the integrated pumps and operates according to a sequence to actuate the integrated pumps, the sequence being indicative of reagents in the reagent reservoirs. The actuation of the pumps is to drive the reagent droplets from the reagent reservoirs into the primary channel in accordance with the sequence. The example system also includes a shell material reservoir with a shell material and an associated shell material pump to drive the shell material into the primary channel to encapsulate the reagent droplets.