A drug reservoir loading and unloading mechanism for drug delivery device using unidirectional rotated lead screw and method thereof are disclosed. The VCSELs include reliability-enhancing layers that perform specific functions at one or more critical locations within a VCSEL structure to reduce or prevent defect formation and migration that otherwise might degrade VCSEL performance, for example, by increasing optical absorption in the mirror stacks or by degrading the electro-optic properties of the active region. The coloring layer overlaps with the reflective electrode layer and the partition. A device for fastening binder sides is also disclosed. Integration may be manual, semi-automated andor fully automated.