Surgical instruments have to be disposed of after a certain number of heat-sterilisation cycles. Staff may not remember to mark every instrument every time, so Ross Electro-medical of Wiltshire, UK, has developed a mechanical tag designed to mark itself (GB patent application 2407187).
The tag, which is fixed to the instrument, is like a small plastic fob watch with an index wheel marked from 0 to whatever number of sterilisation cycles is considered safe. A plastic spring inside the index wheel heats up during each cycle and expands by just enough to push a ratchet around…
