The experimental device is being developed by a team led by Northwestern University's Prof. John A. Rogers. It has already been tested on rats, with promising results.
Made mainly of a biodegradable, biocompatible elastomer, the soft and flexible implant takes the form a thin strip which is 5 mm wide at its widest point, and is about as thick as a piece of paper. In a surgical procedure, one end of it gets wrapped around the peripheral nerve that needs to be temporarily silenced. The device is linked to a pump located on the outside of the patient's body.
Whenever the person starts feeling pain in the affected area, they use the pump to separately send a liquid coolant and nitrogen gas into the implant. The coolant is called perfluoropentane, and is already medically approved for use in inhalers and as an ultrasound contrasting agent.
Within the device, the coolant flows through one microfluidic channel, while the nitrogen flows through another. When the two both flow into a shared chamber and mix together, the nitrogen causes the coolant to rapidly evaporate, producing a localized cooling effect. That effect numbs the nerve, causing the pain to cease.
Of course, if the nerve were to get too cold, it could be permanently damaged. In order to keep that from happening, an integrated sensor continuously monitors the temperature of the nerve. If it starts getting excessively cold, the flow rates of the coolant and nitrogen are reduced accordingly.