METATHERM will demonstrate a versatile energy harvesting and communication system for unattended environment sensors arrays, allowing the development of maintenance free and autarkic operation devices. The novelty builds up from several different innovations, the main one being the microwave antenna, based on epsilon engineering using metamaterials, allowing the antenna to show extremely high gain and an extreme compactness [FETOPEN Project NANOPOLY]. The energy efficiency of the antenna allows the electrical power need to be decreased accordingly, which allows the consideration of novel energy harvesting technologies to be used to power the system. In METATHERM, the energy of the sun is harvested using a novel ionic thermoelectric device. This technology is based on ion migration under a thermal gradient, and show higher Seebeck coefficient than usual tellurium based semiconductors without the use of rare or toxic elements: a significant advantage in the context of the rapidly growing energy demand for IoT and mobile electronic systems. Used in addition to a supercapacitor to store the electrical energy and a thermal energy storage device, METATHERM platform will allow continuous operation of the device day and night. Moreover, due to the similarity in device structure between the iTE device and the supercapacitor, METATHERM will benefit from manufacturing know how of the latter. A substantial maturity level increase is then expected for the iTE devices. Finally, the project aims to develop a platform integrating all these technology in a single device, and exploration of its potential applications. To ensure market fit, the project plans a 3 phases exploitation plan, gathering potential user interest at the beginning of the project, selecting most promising applications at the demonstrator design stage, and produce a transfer plan at the end of the project.