Embodiments of the present application can provide systems and methods for a micromixer combustion head end assembly. The micromixer may include one or more base nozzle structures. The base nozzle structures may include coaxial tubes. The coaxial tubes may include an inner tube and an outer tube. The micromixer may also include one or more segmented mixing tube bundles at least partially supported by a respective base nozzle structure. Moreover, the micromixer may include an end cap assembly disposed about the one or more segmented mixing tube bundles.