In one aspect, the invention features assemblies for depositing droplets on a substrate during relative motion of the assembly and the substrate along a process direction. The assemblies include a first printhead module and a second printhead module contacting the first printhead module, each of the printhead modules including a surface that includes an array of nozzles through which the printhead modules can eject fluid droplets, wherein each nozzle in the first printhead module's nozzle array is offset with respect to a corresponding nozzle in the second printhead module's nozzle array in a direction orthogonal to the process direction.