Tiny robots swim the front crawl through your veins

It would take about two months for the bot to swim the length of an Olympic swimming pool – in that time, Phelps could swim almost 5 million lengths. But the nano-swimmer is fast for its size, and it's strong enough to pass through more viscous liquids, like blood, to deliver medicine from inside your veins. The front crawl is the fastest way for humans to swim. So Tianlong Li at the Harbin Institute of Technology in China and his colleagues built their swimming robot to mimic that motion. Each nano-swimmer is 5 micrometres long and has three main parts, connected together like sausage links by two silver hinges.