This invention is another tool to help improve the handwashing of hospital medics (a New York Times article recently claimed that washing only happens about 1/3 as frequently as training requires).
All medical staff in contact with patients would wear a brightly coloured bracelet (collecting a fresh one as they began their shift). This would contain an aerosol full of harmless, water-soluble paint.
The bracelet would also contain a timer which would ensure that a small spot of bright paint was delivered onto the back of a medic’s hand, say every ten minutes throughout the day.
This device could be manufactured as cheaply as a digital watch using that technology as well as the simplest inkjet mechanism (in volumes big enough to equip all people in contact with patients).
The appearance of the paint would remind wearers to wash their hands at once. Patients could raise an objection if either the bracelet wasn’t worn or there was a spot of paint on the hand of their examiner.
A more advanced version would also print the digital time on the skin of the medic.