In the next years, the LHC accelerator will be upgraded with an increase of instantaneous and integrated luminosity, so that the particle rate will drastically increase. The ATLAS goal is to cope this large particle rate and at the same time trying to conserve the high muon detection efficiency. For this purpose the current innermost stations of the Muon Spectrometer end-caps, the Small Wheels , will be replaced in the year 2019/2020 shutdown with the New Small Wheel detector for high luminosity LHC runs. The New Small Wheel will feature two new detector technologies: resistive Micromegas will be used as a precision detector while small strip Thin Gap Chambers will provide the trigger.
An overview of the design, construction and assembly procedures of the Micromegas modules will be reported with particular reference to the SM1 chambers built in Italy. Results and characterizations will also be presented.