Detecting Thermal Cloaks via Transient Effects.
Recent research on the development of a thermal cloak has concentrated on engineering an inhomogeneous thermal conductivity and an approximate, homogeneous volumetric heat capacity. While the perfect cloak of inhomogeneous κ and inhomogeneous ρcp is known to be exact (no signals scattering and only mean values penetrating to the cloak's interior), the sensitivity of diffusive cloaks to defects and approximations has not been analyzed. We analytically demonstrate that these approximate cloaks are detectable. Although they work as perfect cloaks in the steady-state, their transient (time-dependent) response is imperfect and a small amount of heat is scattered. This is sufficient to determine the presence of a cloak and any heat source it contains, but the material composition hidden within the cloak is not detectable in practice. To demonstrate the feasibility of this technique, we constructed a cloak with similar approximation and directly detected its presence using these transient temperature deviations outside the cloak. Due to limitations in the range of experimentally accessible volumetric specific heats, our detection scheme should allow us to find any realizable cloak, assuming a sufficiently large temperature difference.
Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.|Department of Mechanical Engineering, University of California, Berkeley, California 94720, USA.|Department of Mechanical Engineering, University of Colorado Boulder, Colorado 80309, USA.
Sophia R
SR
Sklan
Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117583, Republic of Singapore.|Department of Physics and Centre for Computational Science and Engineering, National University of Singapore, Singapore 117546, Republic of Singapore.|NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Kent Ridge 119620, Republic of Singapore.
Xue
X
Bai
Department of Mechanical Engineering, University of California, Berkeley, California 94720, USA.|Department of Mechanical Engineering, University of Colorado Boulder, Colorado 80309, USA.
Baowen
B
Li
Department of Mechanical Engineering, University of California, Berkeley, California 94720, USA.|NSF Nanoscale Science and Engineering Centre, 3112 Etcheverry Hall, University of California, Berkeley, California 94720, USA.|Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA.
Xiang
X
Zhang