Project Description

#3087

The bracelets are intended to transmit touch at a distance, a squeeze of the wrist, which acts as a comforting reminder from one person to another – even when they are separated by thousands of miles. They do this by measuring a squeeze on the bracelet as a change in voltage. This analogue input is then approximated into a digital number by an Analogue-to-Digital converter in a micro-controller. That number can then be transmitted to the paired bracelet as a text message by mobile phone technology, using the already existing networks throughout the world. Once the message is received, which normally is almost instantaneous, the process is reversed at the other bracelet and the receiver feels a comforting squeeze. This allows differently pressured squeezes to be felt by the receiver.
The bracelets are intended to be something cheap that everyone could afford to have if they wanted to. They are made from a soft material such as silicone rubber, something that stretches and is also thermally insulating. There are a number of different materials that change shape when subjected to an electrical current; the bracelets include strands of muscle wire, but another alternative, perhaps safer, could be piezo ceramic. Muscle wire changes shape at 70�C so it must be insulated from the wrist. Piezo ceramic has the problem of not contracting enough for a meaningful squeeze, so wasn’t chosen. It also relies on improving battery technology, getting more current and voltage from smaller and smaller batteries, while at the same time not being too expensive to stop people buying something that is a bit of fun. The material that is used to sense the pressure is called Quantum Tunnelling Composite, which can be used in a powder included in another material. Again there are other possibilities, such as graphite powder; however the basic idea is the same: resistance changes relative to the applied pressure.
The bracelets are sold as pairs, with matched sim cards that can be removed and replaced, if someone wanted to squeeze someone else. The only sign that this piece of jewellery may be something more than just cheap and cheerful is the microcontroller visible on top. All other pieces of circuitry are hidden inside the silicone, or in the case of batteries and sim cards that need to be accessible, against the wrist. The transmitting circuit and the pressure monitoring circuits have been placed on opposite sides of the wrist as a precaution against possible interference.