Battery-powered, self-heating insoles can help keep your feet extra toasty during winter activities, but few of us want to charge our shoes. Solecooler’s Climfeet insoles promise to not only warm your feet without the use of chemical reactions or batteries, but to also cool them when temperatures soar. Better yet, the only power source they need is your footsteps.

Even the most advanced battery-powered heating insoles, which generate heat as a by-product of a chemical reaction, only last for about 10 hours. That’s long enough for a day’s skiing adventures, but inadequate if you’re heading out into the frigid wilderness for some long hikes and winter camping. The Climfeet insoles take an entirely different approach, leveraging the same approach as another camping tool: the fire piston.

Instead of relying on a stock of matches to start a fire, some outdoorsy types prefer to rely on a fire piston: a simple device featuring a cylinder with a piston inside that you slam against a hard surface. The force of the blow causes the piston to rush into the cylinder and quickly compress the air inside, increasing the air’s temperature to over 500 degrees Fahrenheit, which is hot enough to ignite a small piece of tinder. All the energy needed to produce those extreme temperatures is provided by the user, and it’s the same for the Climfeet insoles.

Instead of pistons and cylinders, the insoles feature closed and completely sealed bubbles, made of a combination of silicone and copper, with each side having a different consistency: one is very flexible and squishy, while the other is much less so. Separating each side of each bubble is a wall with a small opening that serves as a sort of nozzle, allowing air to be transferred back and forth between the two. When the insole is stepped on, the softer side of the bubble compresses and forces air into the more rigid side, creating a temperature increase of about 7.2 degrees F. When the foot is raised and the pressure on the insole decreases, air rushes back into the softer side of each bubble, creating a cooling effect instead.

The process works the same no matter which side of the insole is being stepped on, so using it with the rigid bubbles on top will have the effect of warming a wearer’s feet while they walk, while using it with the softer bubbles on top will instead help cool their feet with every step.

No other source of power is needed, but that’s also one of the downsides of this approach: it won’t offer any temperature regulation if someone isn’t walking. Its creators also point out that the heating and cooling effects are most noticeable in more extreme temperatures, like below 68 degrees F, or above 86 degrees F. That makes their ~$69 price tag a bit of a tough sell when battery-powered heating insoles are roughly the same price and can increase the temperature inside a boot up to almost 150 degrees F. Will a temperature increase of 7.2 degrees F under your feet really make much of a noticeable difference when the rest of your body is freezing in the cold?


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