What does not work? Flash is already 3D. DRAM is rapidly becoming 3D. High end FPGA chips have been 3D for a couple of years. Going vertical is the obvious way to extend Moore's Law, and the main reason why we don't see more of it today is that until recently it was easier to shrink transistors, so that's what people did. Now that's changing, and people will solve engineering problems related to 3D just like they solved engineering problems related to transistor shrinking.
We might not know how exactly brain performs some of the tasks, but we are pretty sure neurons are arranged in 3D structures, and heat dissipation is not a problem.
> we are pretty sure neurons are arranged in 3D structures, and heat dissipation is not a problem.
Actually, heat dissipation is a HUGE problem for biological structures. Heat exhaustion is a really easy thing to have happen to you.
Biological organisms operate well only in a very narrow temperature range. The brain is a gigantic heat producing organ coupled to an enormous heat dissipating organ--skin.
Flash and DRAM only have localized activity so heat isn't so much an issue - yet.
There is actually a limit study using fundamental physics that shows that the amount of heat you can remove from a solid per unit time has a limit. Overheating is unavoidable below a certain volume. We're very close to that limit.
We might not know how exactly brain performs some of the tasks, but we are pretty sure neurons are arranged in 3D structures, and heat dissipation is not a problem.