Printing and electromagnetic characteristics of 3D printing frequency selective surface using graphene

The study of Frequency Selective Surface(FSS)by Direct ink writing(DIW)has attracted much attention due to the convenience and effectiveness of 3D printing technology.However,the limited printing precision of DIW has heavily restricted its applications as the electromagnetic performance is highly sensitive to it,especially the precision at the microscale.Herein,the ultra-high printing precision of FSS was achieved through DIW by the uniformly dispersed graphene sheets to deeply modify the rheological behavior and the steric hindrance effect.Thus,the highly precision of the printed filament width as thin as67μm with a space of only 42μm were achieved,which is difficult for conventional DIW,and no structural distortion is found after 3D printing,no matter it was 2D printed on a flat surface or the sharply skewed hook face,or even 3D printed to architectural structures.According to the highly improved precision,the electromagnetic performance matching between the designed model and the printed physical FSS device was perfectly achieved,reducing the center frequency error less than 0.3 GHz,and the transmission coefficient error less than 0.046.Our work promises an effective and easy preparation of high-quality FSS from the aid of graphene.

Wrinkling modes of graphene oxide assembled on curved surfaces

Assembling two-dimensional(2D)sheets into macroscopic three-dimensional(3D)forms has created a promising material family with rich functionalities.Multiscale wrinkles are intrinsic features of 2D sheets in their 3D assembles.Therefore,the precise wrinkling modulation optimizes the transition of outstanding properties of 2D sheets to expected performances of assembled materials and dominates their fabrication process.The wrinkling evolution of 2D sheets assembling onto flat surfaces has been extensively understood,however,the wrinkling behaviors on the more generally curved surface still remain unclear.Here,we investigate the wrinkling behaviors of graphene oxide sheets assembled onto curved surfaces and reveal the selection rule of wrinkling modes that determined by the curvature mismatch between 2D sheets and target surfaces.We uncover that three wrinkling modes including isotropic cracked land,labyrinth,and anisotropic curtain phases,respectively emerge on flat,spherical,and cylindrical surfaces.A favorable description paradigm is offered to quantitatively measure the complex wrinkling patterns and assess the curvature mismatch constraint underlying the wrinkling mode selection.This research provides a general and quantitative description framework of wrinkling modulation of 2D materials such as high performance graphene fibers,and guides the precise fabrication of particles and functional coatings.

一种高选择性三阶带通三维频率选择表面

提出了一种具有高选择性和三阶带通响应的三维(3-D)频率选择表面(Frequency Selective Surface,FSS)。该3-D FSS的单元结构由3个贴片金属方筒和3个介质方筒嵌套而成,产生3个传播路径。2个方形同轴路径提供方形槽谐振,产生2个传输极点,平行板路径提供半波长谐振,产生另一个传输极点,由此形成三阶通带。由于不同传播路径出射端处电场矢量相位反相,产生了3个传输零点,提升了频率选择性。通过场理论法和等效电路法分析了该3-D FSS的工作原理。加工出该3-D FSS实物,并进行了实验测试。可以发现,该3-D FSS能够实现平坦的通带、高选择性、良好的角度稳定性、双极化和较小的电尺寸。

三维微元加载频率选择结构设计研究

频率选择表面(FSS)是谐振单元周期排布而成的人工电磁结构,其在频域上可实现带通或带阻功能。在宽频带通FSS设计中,通带内插损特性和带宽特性往往相互制约,存在严重的矛盾,这是亟待解决的技术难题。针对此问题,文中提出一种基于FP谐振机理的新型FSS设计。该设计在典型带通FSS结构基础上,通过三维微元层,引入FP共振模式。通过选择合适的微元尺寸,推迟微元层谐振频率,在不影响原有带通谐振机理的基础上,提高调制场相位的能力,达到拓展透波带宽的目的。文中对三维微元加载FSS新设计进行的特性仿真分析,验证了该结构的可行性和有效性。