Dr Bayley’s paper describes not living cells, but synthetic printed material made to act like them. A cell is, in essence, a drop of watery liquid surrounded by a fatty membrane. Dr Bayley and his colleagues printed artificial versions of this arrangement: tiny droplets of an aqueous solution, each with a volume of a few trillionths of a litre, were sprayed into oil in order to pick up a fatty coat.
On its own an individual droplet, even one with a fatty coating, is rather dull. Collectively, however, they become quite interesting. In one experiment, for example, Dr Bayley printed a pattern of droplets, some with proteins in their membranes. Each droplet’s coat bound to its neighbour’s to create a wall made up of two layers. The proteins formed pores in these walls and when the researchers applied a voltage, ions in the aqueous solution coursed through the pores, generating a signal similar to the “action potentials” that carry messages through nerve cells.
Until now, those who have thought about printing artificial organs have assumed they would be made of real cells. Dr Bayley’s approach offers an alternative: artificial organs made of artificial cells. There would be an advantage to this, for such cells cannot reproduce and therefore could not become cancerous.