Retraction Note: Study and development of an optical waveguide cap for biomedical applicationMargarida Ferreira, Catarina S. Monteiro, Patrícia C. Henriques, Inês C. Gonçalves and Orlando FrazãoEPJ Web Conf., 266 (2022) 13036DOI: https://doi.org/10.1051/epjconf/202226613036