TINY rocket motors could one day be used to fire drugs into the human gut.

Radio-controlled capsules are already used to manoeuvre drugs to specific sites in the digestive tract to test their effectiveness. Various methods can be used to release the drug once it gets there, but in many cases much of it remains in the capsule.

So Deyu Li of Vanderbilt University in Nashville, Tennessee, and colleagues have developed a more forceful drug release system: a capsule with a drug-ejecting piston that is driven by a tiny solid-fuel rocket motor (Sensors and Actuators A: Physical, vol 159, …