The inventor of the hoverboard says he's made no money from it

While Chinese factories pump out copies, Shane Chen - who patented the original hoverboard - is sanguine. It's 'just a toy', he says

Shortly before Christmas, with sales of hoverboards surging as the must-have gadget of 2015, Shane Chen flew to China to confront his tormentors.

Chen is the man who developed and patented the hoverboard design in his lab on the US west coast four years ago. With its two wheels, the "hoverboard" doesn't quite match up to the promise of its namesake in Back to the Future - but that has not put a dent in its popularity.