A fluidic dispensing device (110) is provided, comprising: a body (122) having a chamber (148) with a perimetrical end surface (150-3), and the body having a stepped arrangement that includes a channel (122-2) having a first inner side wall (122-6) that defines a recessed path around the perimetrical end surface; and a diaphragm (130) having a dome portion (130-1), a perimetrical positioning rim (131-2) that surrounds the dome portion; and a sealing surface (131-6). The channel is sized and shaped to receive the perimetrical positioning rim. The first inner side wall engages a perimeter of the perimetrical positioning rim to position the sealing surface for sealing engagement with the perimetrical end surface to define a fluid reservoir (136).