Methods of making a droplet-generating device. In an exemplary method, an upper member is injection molded. The upper member includes a bottom surface and also includes a first microfluidic channel, a second microfluidic channel, and a third microfluidic channel each formed in the bottom surface. The upper member has a plurality of openings each extending completely through the upper member from the bottom surface and creating a side wall region of a sample well, a carrier well, and a droplet well. A cover layer is attached to the bottom surface of the upper member, such that the cover layer seals a bottom side of each microfluidic channel. The microfluidic channels meet one another to create a droplet-generation region. The sample well, the carrier well, and the droplet well are connected to the droplet-generation region via the first, second, and third microfluidic channels, respectively.