If you’ve ever had surgery, slowly  coming out of the anesthesia-induced lull can be great until you are suddenly hit  with the excruciating post-operative pain.

Yes, there are plenty of medications  that can help relieve that pain. But they can have some unpleasant side  effects, as well as the risk of dependency.

Which is why researchers have been  exploring a totally different way to control pain: using an implantable  device that literally freezes it away. [♪ INTRO] It’s no secret that when you have a mild  injury, cold can help numb the pain. This is already used in  medicine, with vapocoolant sprays as an option to help reduce the  sting of getting an IV inserted. Topical cold sprays are a  great solution for mild pain, but they do not do much for deep pain  in the body, like from a surgery.

Surgical pain requires deep and  strong relief, a combination that can be difficult to achieve without  opiates or supplemental injections. And it can’t be too strong either,  because coming out of knee surgery totally numb from head to toe is also not ideal. One team of researchers at  Northwestern University came up with a potential solution that harkens  back to the vapocoolant spray: a device that cools down your nerves.

See, pain is communicated in  nerves through electrical signals and when the nerves get colder,  the signals move slower and slower, and they’re blocked entirely when  the nerves reach 15 degrees Celsius. This means that if the nerves can get  that cold, pain signals will be minimized, which is part of why icing an  injury helps reduce the pain. But it’s also pretty impractical to just  ice any injury or surgical incision forever, not to mention potentially  damaging to the surrounding tissue.

Which is why these researchers  used a combination of two chemicals to recreate that  cooling effect just on the nerves. And rather than using an ice pack, these devices use a super basic  source of cooling: Evaporation. But before we get to that… quick ad break.

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Now, back to the soothing power of cold. The device developed by the researchers  uses a chemical called perfluoropentane, which boils just above room temperature. When perfluoropentane is exposed to  another chemical, gaseous nitrogen, it is immediately forced to evaporate.

That evaporation leads to a cooling effect, almost like making your body sweat  on the inside to cool itself off. And to keep this focused just on the  nerve cells, they designed a tiny device, only 5 millimeters wide at its widest point, to hold those two fluids  inside microfluidic channels. Microfluidic channels are pretty  much what they sound like: they are extremely tiny tubes, like  only a few micrometers in diameter, that small amounts of fluid can move through.

So when the fluids combine in a  shared chamber, the perfluoropentane evaporates, and voila, a nice burst of cold. Before that, the fluids remain in their separate channels where they  can, you know, just chill. In rat studies, this burst of cold  translated to about 10 degrees Celsius, 5 degrees past the necessary  threshold to stop pain signals.

However, there is a catch. The temperature has to be carefully regulated, since our bodies aren’t designed to have  any part of us stay that cold for that long. Constantly cooling your  nerves can lead to neuropathy, meaning permanent nerve damage.

To mitigate this, the device also contains a tiny thermal sensor to make sure  nothing gets dangerously cold. The best part about this device  is that it is bioresorbable, meaning that once it’s done  its job, it will quietly dissolve away over the next month or so. That means that there’s no need  to have surgery to remove it!

The device wouldn’t be the perfect  solution for every patient, of course. The researchers envision it being  used for individuals who are having a surgical procedure that  already isolates the involved nerves, since one of the more risky  aspects of implanting it would be actually getting to the nerve. Our nerves are pretty fragile, and digging around for them  adds a bit of unnecessary risk.

The device would also be best suited when opioids are expected to be required post-operation. Amputations, for example, would  meet both of these criteria. All of that said, these things  are still far from human trials.

The invasive nature of this device  and the need for more research means it’ll be years before the  device is ready to test on humans. Plus, no device is immune to failure, like the channels bursting or  the thermal sensor failing, so safety will have to be  a priority moving forward. And while the whole idea of a  dissolvable implant seems pretty sci-fi, this research team isn’t the only group  that’s thinking along these lines.

For example, another device from  that same Northwestern University lab was also a fully biocompatible design, but instead of aiding with post surgical pain,  it helps with post surgical nerve repair. By sending regular, tiny electrical  impulses, the device can not only speed up nerve growth, but also  recruit all sorts of factors that help nerves grow up big and strong. And microfluidics are useful in biomedicine too, doing everything from catching  cancer cells as blood flows through them to decreasing eye  pressure in glaucoma patients.

The use of these devices in  humans may still be years away, but this research highlights  how there are still many creative pain management strategies yet  to be discovered - which is pretty… cool. [♪ OUTRO]