Excess CO2 and sunlight are natural resources we can use now and in the future.
https://www.nature.com/articles/ncom...sical-sciences
http://pubs.acs.org/doi/abs/10.1021/acs.jpclett.5b01610
http://www.kurzweilai.net/utility-fo...ms-are-made-of
Software for flight assembled structures is being worked out now on the macro-scale
https://vimeo.com/69257453
https://www.youtube.com/watch?v=JnkMyfQ5YfY
Self replicating utility fog, made of graphene based materials, that are made using sunlight and excess carbon dioxide in the atmosphere, provide something like 70 tons of ready material for every man woman and child on the planet.
https://pdfs.semanticscholar.org/428...77d8af4d43.pdf
With artificial intelligence and a meshnet, we can basically have all we wish made on demand.
Dissolved back into foglets when you are finished using them.