FLOW PATH DEVICE

A second device includes a first surface, a second surface in contact with a first device, and a first hole extending through and between the first surface and the second surface and being continuous with a groove on the first device. A third device includes a third surface in contact with the first surface, a second hole open in the third surface and continuous with the first hole, and a flow path continuous with the second hole and open in the third surface. As viewed in a first direction from the first surface to the second surface, the first hole includes at least one vertex surrounded by the second hole, and a pair of sides joined to the at least one vertex and widening toward the flow path to define a minor angle.