here's something cool. I would summarize it before posting the link, but I don't quite understand it lol http://www.nature.co...ature10500.html
The basic gist as I see it is they've made molecular tiles that form in a pattern and assemble a negative 'mold' of themselves which replicate the negative itself thus a copy of the orginal pattern. If you pair them side by side and called them a single unit you'd get a self replication unit. each side duplicating the other.
When I think about first generation assemblers I think along these lines, because one of the hard things to do is get a carbon based device to assemble carbon atoms because the carbon and carbon tend to bond and interfere with each other. But a silicon system might work for carbon, and a carbon system might work for silicon. Starting from that base pairing I can see designing an assembler 'worm' that is made of carbon by the same method they use to make race cars and stuff. Then use the worm to build a silicon twin for building carbon objects.
Then put them together and you can start building pairs of them, then clusters of them and then sheets of them. and eventually you will be able to build any mechanical or solid objects with carbon, silicon, or circuts of silicon and carbon materials. That could be a good first generation as it could meet a lot of physical and industrial needs. Like making those carbon nanotube ribbons for the space elevators.
They would also allow for being able to build second generation assemblers out of carbon/silicon that can work with a wider source of materials and build the second generation sheets that could fabricate things like medicines and more complicated mechanical and electronic components.
From that point on it's just designs as fast as we can figure them out. That's why I think after the first assembler capable of building a better assembler is the point where singularity takes off. Litterally if we build a unit that can build a unit that can make anything from any combinations of atoms it would be: Day one first unit, day two second unit, day three mass produced unit that could build anything from atoms up. Day four fastest most efficient computer core ever made crunches numbers on all potential design and allows real time simulation, day five fabrication of devices that build food and water supplies supplied to all the world, day six tricorders and injectable nanomedical devices see an end to bacterial, viral and cancerous disease, day seven the first molecularly build space station begins construction in orbit where it will function as the assembly platform for exploratory, generation and colony ships.
Live content within small means. Seek elegance rather than luxury, Grace over fashion and wealth over riches.
Listen to clouds and mountains, children and sages. Act bravely, think boldly.
Await occasions, never make haste. Find wonder and awe, by experiencing the everyday.