Bacteria have been harnessed as miniature pumps for the first time. The trick was to trap a squirming army of bacteria on a chip, and then get their flagella to pump fluid through channels thinner than a human hair.

Kenneth Breuer and colleagues at Brown University in Providence, Rhode Island, squirted a concentrated solution of the naturally sticky bacteria Serratia mercescens into transparent rubber channels embedded in a glass chip. The bugs formed a "bacterial carpet" on the surface of the channels, leaving their 12-micrometre-long flagella, which they usually use to swim, free to move. They were able to pump particles through the channels at 25 micrometres per second. Raising the temperature or adding glucose made the bacteria pump faster.