“…However, most previous studies mainly considered ideal interfaces including steady-state and transient state response, see for example [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ] and [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. A recent progress in the study of the imperfect interface effect in the design of thermal metamaterials was made by Chen and Lin [ 27 , 28 ] for conduction phenomena in the steady-state regime. In these studies, they showed that an object can always be made thermally invisible, with the effect of the imperfect interface, as that of a homogeneous background material.…”