Algae Can Carry Cargo
Steve Nixon writes "Recently, a team of scientists devised a way to make single-celled algae bear loads over distances of several centimeters--a tactic that the researchers say could prove useful in tiny machines. Algae and other single-celled organisms power their movements with molecular motors. 'Scientists have long coveted these motors for use in micromachinery,' notes chemist Douglas B. Weibel of Harvard University.
The manufacturing facility for more cargo carriers is a vat with some nutrients and sunlight. What's your simpler assembly line look like?