3-D/4-D-Printed Reconfigurable Metasurfaces for Controlling Electromagnetic Waves

A comprehensive review of 3-D/4-D-printed reconfigurable metasurfaces (RMSs) is presented in this article. A metasurface (MS) demonstrates exceptional abilities for electromagnetic (EM) wave molding beyond that offered by conventional planar interfaces, and RMS provides MS with more diverse EM wave-control capabilities. RMSs are categorized by the type of external stimulus used for reconfiguration, such as electrical RMS, fluidic RMS, mechanical RMS, and thermal RMS. To implement these RMSs, it is important to understand the design and fabrication requirements as well as the EM characteristic of each RMS, including its advantages and disadvantages. In particular, except for electrical RMS, RMSs require complex 3-D structures or special materials that are difficult to implement with conventional subtractive manufacturing methods such as printed-circuit-board manufacturing. Recently, advanced 3-D/4-D printing technology has achieved high fabrication freedom and meets the design and fabrication requirements of each type of RMS. In this article, we introduce representative RMSs with the development of 3-D/4-D printing technology and materials. Furthermore, current issues of RMSs based on 3-D/4-D printing technology and future directions are described.

I. Introduction

The impact of manipulating EM waves is growing with the development of wireless communication, stealth, hologram, virtual reality, augmented reality technology, and the Internet of Things. RMSs represent the key technology for controlling EM waves [1], [2], [3], [4], [5], [6]. For example, in 5G wireless communication, a reconfigurable intelligent surface is a crucial part for solving the non-line-of-sight and high path loss using a beam-controllable transmitter or reflector [7], [8], [9], and in RF energy harvesting, the MS absorber has been used for achieving high energy-harvesting efficiency by absorption and transference in a large area [10], [11], [12], [13].