I think when nanodevice engineers talk about 2D problems, they are talking about devices in which the interesting physics happen in 2D.
The actual devices actually exist in the 3 spatial dimensions of course, and evolve in the time dimension. They just have physics that involve very flat sheets of things, or all of the interesting stuff happens on the surface of something.
The big deal stuff about time and space both being dimensions is more of a relativity thing I think. IIRC in quantum physics time is really annoying and everybody hates it.
The actual devices actually exist in the 3 spatial dimensions of course, and evolve in the time dimension. They just have physics that involve very flat sheets of things, or all of the interesting stuff happens on the surface of something.
The big deal stuff about time and space both being dimensions is more of a relativity thing I think. IIRC in quantum physics time is really annoying and everybody hates it.