A robotic pill that can propel itself through mucus in the intestine could enable some injection-only drugs, such as insulin or certain antibiotics, to be delivered by mouth. To be absorbed into the bloodstream, drugs taken orally have to survive harsh stomach acid and enzymes, as well as manoeuvre through bacteria and mucus in the intestine, which can rule out many sensitive drugs from being taken this way. Only 1 per cent of insulin, for example, is taken up by the body when it is swallowed because stomach enzymes break it down, so people with diabetes have to take injections instead. Shriya Srinivasan at the Massachusetts Institute of Technology and her colleagues have developed a drug-carrying capsule called RoboCap that can drill through mucus in the lower intestine and disperse its load. "I was watching videos of these machines that can make tunnels and I thought, 'OK, what if we did this but for mucus,'" she says.