A team of researchers led by Northwestern University have developed a device that seems to miraculously relieve pain without the use of painkillers. The small, flexible implant would be inserted during surgery to help manage postoperative pain. This could be especially useful for patients that undergo routine surgeries and would need to take a course of pain medication. The device works on a simple premise. The speed that nerves can transmit messages can be reduced when the nerves are cooled. John A. Rogers, a professor at Northwestern and the lead researcher explained in a press release that “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. 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”.
The implant is liquid cooled, and makes use of tiny microfluidic channels, one of which contains a coolant (perfluoropentane) and the other dry nitrogen. When the coolant and the dry nitrogen are allowed to mix in a shared chamber a reaction occurs causing the liquid to evaporate. This evaporation is key to the device’s effectiveness. The evaporation can be triggered at very specific locations on the nerve to give extremely targeted pain relief. An external pump allows the user to remotely activate the device and control the intensity of the relief.
The implant makes use of integrated sensor monitors to ensure that the device does not get too cold which could damage nerve tissue. “Excessive cooling can damage the nerve and the fragile tissues around it,” Rogers explained. “The duration and temperature of the cooling must therefore be controlled precisely. By monitoring the temperature at the nerve, the flow rates can be adjusted automatically to set a point that blocks pain in a reversible, safe manner. On-going work seeks to define the full set of time and temperature thresholds below which the process remains fully reversible.”
This is not the first attempt to develop cryotherapy to treat pain. There have been a number of attempts in the past but those devices could not target specific nerves instead imprecisely blocking whole areas of tissue which could have led to unwanted side effects such as tissue damage and inflammation.
The device is also fully bioresorbable meaning that once it is implanted it will be absorbed by the body eliminating the need to remove it via surgery. Roger’s lab has been researching these bioresorbable devices for about a decade, in 2012 the team introduced the concept in an article published in Science. Since then they have demonstrated two devices using the same technology. The first was in 2018 when they revealed an implant that sped up nerve regeneration. In 2021 they showcased a wireless, battery-free pacemaker designed to disappear when it is no longer needed.
