Metamaterial Concentrator for Thermal Energy Harvester Rapha Nichita Kaikatui, Adik Putra Andika, Vinsenius Letsoin, Paulus Mangera, Damis Hardiantono, Yogo Adhi Nugroho, Herry Susanto and Haryo Wibowo E3S Web Conf., 190 (2020) 00032 Published online: 23 September 2020 DOI: 10.1051/e3sconf/202019000032