‘Smart sand’ can self-assemble to duplicate parts or create new tools

‘Smart sand’ can self-assemble to duplicate parts or create new tools: Unlike many other approaches to reconfigurable robots, smart sand uses a subtractive method, akin to stone carving, rather than an additive method, akin to snapping LEGO blocks together. A heap of smart sand would be analogous to the rough block of stone that a sculptor begins with. The individual grains would pass messages back and forth and selectively attach to each other to form a three-dimensional object; the grains not necessary to build that object would simply fall away...

Algorithmically, the main challenge in developing smart sand is that the individual grains would have very few computational resources.