A battery-operated device a little larger than a golf ball could one day help treat people with hearing loss by delivering medication directly into the cavity in their ear.

Engineers at Draper, a non-profit research company in Cambridge, have been developing the device along with collaborators at Massachusetts Eye and Ear.

This month, they showed that the device is safe to be used in guinea pigs — mammals with sufficiently similar ear anatomy to ours. The next step, they say, is to test it in people.