XPatch is a biocompatible and flexible module, worn directly on the skin. This called for a soft and stretchable skin-like choice of material, like polyurethane and silicon. As the electronics are embedded in that material, the components are fully protected and never in direct contact with bare skin. The patchs thin biochemical sensor chips are where the magic happens: They are placed into the surface of the patch, where they are kept close to the skin. A tiny opening in the substrate allows the sweat analysis to work. A miniscule piece of fabric is integrated in the empty space behind the chip and captures the wearers perspiration. The sensor built into the chip analyses this sample and pushes the resulting data in real time to a device, where the user can visualize the information and use the insights to improve their physical fitness.