In the context of global warming and decrease of pure water resources, there is an urgent need to find new water sources. Passive condensation of atmospheric water vapor (dew) by radiative cooling is the solution that we will consider in this project. Dew water, mostly ignored until now, could serve as an additional water source, supplementing rain and fog water. A promising approach takes advantage of metamaterials, which can provide a cooling power of 60-100 W/m2. The goal of METAWATER project is to take a major step in radiative cooling and dew water harvesting by designing new types of emitter-condensers based on hierarchical structured surfaces optimizing both radiative cooling and wetting properties. To address this challenging issue, we will implement surface treatment strategies by plasma process to create integrated micropatterned and nanostructured surfaces combining three outstanding characteristics which have never been coupled so far: (i) efficient radiative cooling capacities due to high emissivity in the IR atmospheric window and high reflectivity of the solar spectrum, (ii) adaptive wetting properties (superhydrophilic/superhydrophobic) to nucleate films or drop (iii) a geometry that accelerates drop and film shedding by gravity, before diurnal evaporation. This project will tackle basic questions on the influence of surface treatment upon the efficiency of radiative cooling and water condensation. It also aims exploring the efficiency of this coupled strategy for water harvesting on emitter-condensers under outdoor conditions. In this project, we aim to shed light on the impact of heterogeneous wettability and architectures on the micro-droplets morphology transition, and design high-contrast wettability patterns to improve the performance of condensation yields for water harvesting. Another major breakthrough will be to explore the new opportunities offered by metasurfaces to increase radiative cooling, particularly in terms of condensation time extension during daytime morning and evening under solar radiation. To carry out this study, meta-surfaces will be numerically optimized then fabricated. A radiative chamber will be specially created to study cooling and condensation phenomena in the laboratory. Thanks to an emissivity close to 0.99 combined with tailored wetting properties, we hope obtaining a cooling power of about 100 W/m2 together with doubling the amount of water collected by gravity (currently about 0.1-0.3 l/night/m² on average). Outdoor investigations will be conducted to study the metasurface efficiency under real environmental conditions and to evaluate their sustainability under aggressive weather conditions. An important effort will be made to evaluate the operation of condensers and their ageing in real conditions. The innovative character of METAWATER project lies in the fact that it encompasses a wide range of physical approaches, from surface treatments, wetting hydrodynamics, heat transfer and thermodynamic performances. To our knowledge, this is the only way to achieve an integrated system with high capacity of water harvesting.