Conformal metamaterial coats for underwater magnetic-acoustic bi-invisibility
Junjie Zhan, Yujian Mei, Kai Li, Yi Zhou, Jian Chen, Yungui Ma
Abstract
Invisible coats inspired by metamaterials have been widely explored for different physical quantities and even with multifunctional response capabilities. In particular, a magnetic cloak has gained special attention for high practicability when compared with its electromagnetic counterparts. In this work, we report a bi-physical metamaterial invisible coating technique that could effectively hide underwater objects from being detected via both magnetic fields and acoustic waves. An ultra-thin coat could work for objects having irregular shapes like squares, greatly broadening potential practical applications. The bilayer magnetic cloaking technique is fully exploited to cast a spatially dependent permeability profile, which could quasi-statically balance out the diamagnetic response of irregular-shaped metals based on field “scattering” cancellation. Integrated with this magnetic cloak, an ultrathin acoustic metasurface made of periodic microbubbles is developed to achieve broadband acoustic absorption for acoustic stealth. This integrated magnetic-acoustic bi-physical conformal coat may lead to important applications not only for military purposes but also for civilian apparatus in shielding the field and wave disturbances, for example, in medical scanning.