Functionality

chili-feet heat insoles convert pressure energy into heat when walking. This requires a minimum weight of 48 kg.

Development and mode of operation

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

As a result, several development teams were commissioned in parallel by Wafe Technology GmbH in 2011. A great deal of knowledge was required to optimize the material so that it could convert as much energy as possible (resulting from the pressure when walking) into heat. It was equally important to achieve that the material relaxes again in the rhythm of normal walking to such an extent that heat can be gained again from the pressure during the next step.

After countless trials, a development team delivered convincing results:
In late fall 2011, a prototype sole material was developed that produced a permanent output of over 2 watts - the desired goal had been achieved! Extensive and extremely successful testing was carried out in the winter of 2011/2012.

Impressive temperature rise

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

 

Tests in the laboratory show the temperature rise of the 3mm/5mm chili-feet warming soles. After 12 minutes, the sole temperature is 5°/10° C higher compared to the starting temperature. Below a video shows such a test:

Flexible and versatile use

The chili-feet warming insoles can be individually cut to size for sizes 35 to 47. They are available in the thicknesses 3mm and 5mm. The 3mm soles are primarily suitable for the transitional seasons (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 corresponds approximately to the distance from Zurich to Hamburg and back again. The microfiber surface ensures a pleasant wearing comfort and absorbs any sweat directly. chili-feet are washable at max. 30 degrees.

More information about the function of the chili-feet insole can be found in this factsheet.