The primary sentiment in the passage is one of frustration. The writer expresses fatigue and disillusionment with the repetitiveness, hype, and branding associated with the field of nanotechnology. This feeling is primarily grounded in their experience of having seen the same cycle of enthusiasm, critique, despondency, and renewed enthusiasm around nanotechnology, without substantial changes in perception or application of the field. They also express irritation at the superficial labeling and branding of this scientific field as something entirely new or revolutionary, while they perceive it to be just an extension or rebranding of what scientists have been doing for years. Despite their frustration, they also express a persistent engagement with the field and acknowledge its transformative potential.