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chili-feet heat insoles convert pressure energy into heat when walking. A minimum weight of 48 kg is required for this.

Development and functioning

After an initial feasibility study, which analyzed different technologies, a technical variant was discovered at the end of 2010 to develop a sole based on a new type of polyurethane material (PUR). This converts the pressure generated when walking into heat.

As a result, in 2011 several development teams from Wafe Technology GmbH were commissioned with the elaboration. largest Knowledge was a prerequisite for optimizing the material to such an extent that it could convert as much energy as possible (from the pressure of walking) into heat. It was just as important that the material relaxes in the rhythm of normal walking to such an extent that heat can be gained again through the pressure with the next step.

After countless attempts, a development team has delivered convincing results:
In late autumn 2011, a prototypical sole material was developed that delivered a permanent output of over 2 watts - the desired goal was achieved! In the winter of 2011/2012 was extensively and tested very successfully.

Impressive rise in temperature

Tests in the laboratory show the temperature rise of the 3mm/5mm chili-feet insoles. After 12 minutes, the sole temperature is 5°/10° C higher compared to the starting temperature.



Below is a video showing one such attempt:

Flexible and versatile use

The chili-feet insoles are for the sizes 35 to 47 individually cut to size. They are available in thicknesses of 3mm and 5mm. The 3mm soles are primarily suitable for the transitional periods (autumn/winter) and the 5mm soles for the cold season at lower temperatures.

Requirements for proper functioning

  • Weight over 48 kg
  • Continuous running/walking as the soles only produce heat when walking. Heat is produced by periodically compressing and relaxing the material. As soon as you stop, no heat is generated and the effect is gone. Despite this, the isolating effect is retained.
  • Sufficient space in the shoe so that you can also compress the sole when running and relax it again when rolling in the area of the unloaded area. If the foot is too tight in the shoe, it is more difficult to compress and heat production is reduced.
  • Furthermore, the soles must not be stored in winter when the outside temperatures are low. They stiffen due to the cold and the warming effect then no longer occurs because the material can hardly be pressed anymore. The shoes with chili-feet or the chili-feet themselves must therefore not be left outside in the cold. This effect is reversible and as soon as the soles return to normal room temperature, the functionality is available again.
  • Applications when skiing, horseback riding, standing around or anywhere where you don't move or move too little or put too little pressure on your feet only work to a limited extent.

material properties

The heat-producing material can be compressed about 1.5 million times. This roughly corresponds to the route from Zurich to Hamburg and back again. The microfiber surface ensures a comfortable fit and absorbs sweat directly. chili-feet are washable at max. 30 degrees.

You can find more information on how the chili-feet insole works in this fact sheet.