Why not aim to improve on blood? Its primary function is to
carry oxygen, and it has evolved to do the bare minimum
necessary on this front - separate any part of the body from a
supply of oxygen for a minute or so and you're in trouble. It
would be nice, for example, to have blood with a reserve
capacity of a few hours, achieved using nanomachines that store
the surplus oxygen that the body doesn't otherwise extract from
air breathed in. Even if the heart stopped or blood stopped
flowing in some vital tissue, you'd have those few hours to seek
medical help. Here is a gentle first step towards the
technologies of better blood: researchers "designed tiny, gas-
filled microparticles that can be injected directly into the
bloodstream to quickly oxygenate the blood. The microparticles
consist of a single layer of lipids (fatty molecules) that
surround a tiny pocket of oxygen gas, and are delivered in a
liquid solution. ... report that an infusion of these
microparticles into animals with low blood oxygen levels re