Nobody wants to suffer physical pain if they don't have to, yet they also don't want to risk developing an addiction to pain-killing opioids. That's where a new drug-free implant comes in, as it reduces pain by cooling nerves.
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.
The implant is designed for temporary use, by people such as patients who are experiencing postoperative pain. With that in mind, the entire device harmlessly dissolves and is absorbed by the body over a matter of weeks – that means a second operation to remove it is not required.
"As engineers, we are motivated by the idea of treating pain without drugs – in ways that can be turned on and off instantly, with user control over the intensity of relief," said Rogers. "The technology reported here exploits mechanisms that have some similarities to those that cause your fingers to feel numb when cold. Our implant allows that effect to be produced in a programmable way, directly and locally to targeted nerves, even those deep within surrounding soft tissues."
A paper on the research is being published in the journal Science.
Source: Northwestern University
