Digital Light Processing 3D-Printed Ceramic Metamaterials for Electromagnetic Wave Absorption

Combining 3D printing with precursor-derived ceramic for fabricating electromagnetic(EM) wave-absorbing metamaterials has attracted great attention. This study presents a novel ultraviolet-curable polysiloxane precursor for digital light processing(DLP) 3D printing to fabricate ceramic parts with complex geometry, no cracks and linear shrinkage. Guiding with the principles of impedance matching, attenuation, and effective-medium theory, we design a crosshelix-array metamaterial model based on the complex permittivity constant of precursor-derived ceramics. The corresponding ceramic metamaterials can be successfully prepared by DLP printing and subsequent pyrolysis process, achieving a low reflection coefficient and a wide effective absorption bandwidth in the X-band even under high temperature. This is a general method that can be extended to other bands, which can be realized by merely adjusting the unit structure of meta-materials. This strategy provides a novel and effective avenue to achieve “target-design-fabricating” ceramic metamaterials, and it exposes the downstream applications of highly efficient and broad EM wave-absorbing materials and structures with great potential applications.

Miura origami based reconfigurable polarization converter for multifunctional control of electromagnetic waves

Polarization is one of the basic characteristics of electromagnetic(EM)waves,and its flexible control is very important in many practical applications.At present,most of the multifunction polarization metasurfaces are electrically tunable based on PIN and varactor diodes,which are easy to operate and have strong real-time performance.However,there are still some problems in them,such as few degrees of freedom of planar structure control,complex circuit,bulky sample,and high cost.In view of these shortcomings,this paper proposes a Miura origami based reconfigurable polarization conversion metasurface for multifunctional control of EM waves.The interaction between the electric dipoles is changed by adjusting the folding angleθ,thereby tuning the operating frequency of the polarization conversion and the polarization state of the reflected wave.This mechanical control method brings more degrees of freedom to manipulate EM waves.And the processed sample is with lightweight and low cost.To verify the performance of the proposed origami polarization converter,a Miura origami structure loaded with metal split rings is designed and fabricated.The operating frequency of the structure can be tuned in different folding states.In addition,by controlling the folding angleθ,linear-to-linear and linear-to-circular polarization converters can be realized at different folding states.The proposed Miura origami polarization conversion metasurface provides a new idea for reconfigurable linear polarization conversion and multifunctional devices.

Switchable chiral mirror based on PIN diodes

Chiral mirrors can produce spin selective absorption for left-handed circularly polarized(LCP) or right-handed circularly polarized(RCP) waves. However, the previously proposed chiral mirror only absorbs the designated circularly polarized(CP) wave in the microwave frequency band, lacking versatility in practical applications.Here, we propose a switchable chiral mirror based on a pair of PIN diodes. The switchable chiral mirror has four working states, switching from the handedness-preserving mirror to the LCP mirror, RCP mirror, and perfect absorber. The basis of these advances is to change the chirality of two-dimensional(2D) chiral metamaterials and the circular conversion dichroism related to it, which is the first report in the microwave frequency band.Surface current distributions shed light on how switchable chiral mirrors work by handedness-selective excitation of reflective and absorbing electric dipole modes. Energy loss distributions verify the working mechanism. The thickness of the switchable chiral mirror is one-tenth of the working wavelength, which is suitable for integrated manufacturing. The measurement results are in good agreement with the simulation results.

Shape memory alloy-based 3D morphologically reconfigurable chiral metamaterial for tailoring circular dichroism by voltage control

Three-dimensional chiral materials with intrinsic chirality play a crucial role in achieving a strong chiral response and flexible light manipulation.Reconfigurable chirality through the 3D morphological transformation of chiral materials is significant for greater freedom in tailoring light but remains a challenge.Inspired by the unique 3D morphological memory capability of shape memory alloys(SMAs),we demonstrate and discuss a chiral resonator in the microwave regime that can realize reconfigurable chirality through 3D morphological transformation.The introduction of heating film realizes voltage control of SMA’s morphology for utilizing the temperature sensitivity of SMA better,enabling arbitrary control of circular dichroism(CD)flip and CD intensity.The qualitative and quantitative analysis of the surface current distribution of chiral enantiomers reveals that the chirality of metaatoms originates from the surge of electric dipole pxand electric quadrupole Q.It is worth mentioning that the proposed strategy to achieve reconfigurable chirality using 3D morphological transformations can be directly extended to other higher frequencies,such as visible,infrared,and terahertz bands.Significantly,our paradigm to study the relationship between complex 3D morphology and chirality holds potential for application in biosensing,spin detection,and spin-selective devices.

Optical transparent infrared high absorption metamaterial absorbers

In this work,an optical transparent infrared high absorption metamaterial absorber is proposed based on indium tin oxide(ITO)substrate.Due to the fact that ITO holds high reflectivity property in infrared region while transparent in optical region,ITO can be used in the application of Surface Plasmon Polaritons.In this design,three kinds of infrared metamaterial absorbers were proposed.All of them can achieve high absorption at 10.6μm while remaining transparent in visible region.LC equivalent circuit model was served as design foundation.The infrared absorption efficiency was numerically calculated and the mechanism analysis is given in the paper.The simulation results show that all three structures can achieve high absorption efficiency at 10.6μm under TE/TM polarization.The absorption remains high when the incident angle is less than 70°.Experimental results exhibit good accordance with simulation.

A reflective-backing-free metamaterial absorber with broadband response

In this paper,we propose a polarization-independent and broadband perfect infrared(IR)metamaterial absorber(MA)without reflective backing.The proposed absorber is a periodic meta-atom array consisting of metal-dielectric-multilayer truncated cones which can absorb 80%EM wave from 50.70 to 81.87 THz,while transmit 80%EM wave from 0 to 37.71 THz.With the decreasing of frequency,the transmissivity increases,which is close to 100%from 0 to 5 THz.We can broaden the absorption bandwidth of the MA by cascading multi-layers truncated cones.Furthermore,the proposed IR MA promises to be one desirable stealth material for radar-IR compatibility.