Is touching the aunt-in-law through a very thick barrier, so that it is not felt, considered unlawful?

Your maternal uncle's wife is a stranger [non-mahram] and not one of your unmarriageable kin. Therefore, it is not permissible to be in seclusion with her or to touch her, even if through a barrier. The jurists have stipulated the impermissibility of touching a non-mahram woman, except for her face and hands, even if through a barrier, and even if there is no fear of temptation and no lust.