Stepwise colloidal lithography toward scalable and various planar chiral metamaterials

Chiral metamaterials(CMs)composed by artificial chiral resonators have attracted great attentions in the recent decades due to their strong chiroptical resonance and identifiable interaction with chiral materials,facilitating practical applications in chiral biosensing,chiral emission,and display technology.However,the complex geometry of CMs improves the fabrication difficulty and hinders their scalable fabrication for practical applications,especially in the visible and ultraviolet wavelengths.One potential strategy is the colloidal lithography that enables parallel fabrication for scalable and various planar structures.Here,we demonstrate a stepwise colloidal lithography technique that uses sequential deposition from multiple CMs and expand their variety and complexity.The geometry and optical chirality of building blocks from single deposition are systematically investigated,and their combination enables a significant extension of the range of chiral patterns by multiple-step depositions.This approach resulted in a myriad of complex designs with different characteristic sizes,compositions,and shapes,which are particularly beneficial for the development of nanophotonic materials.In addition,we designed a flexible chiral device based on PDMS,which exhibits a good CD value and excellent stability even after multiple inward and outward bendings.The excellent compatibility to various substrates makes the planar CMs more flexible in practical applications in microfluidic biosensing.

Cretaceous dinosaur and crocodylomorph egg records of the Sanshui Basin,Guangdong Province,southern China

This paper describes newly discovered dinosaur and crocodylomorph egg fragments from the Upper Cretaceous Sanshui and Dalangshan formations of the Sanshui Basin of Guangdong Province,southern China.Despite the absence of macroscopic information,the eggshell specimens can be identified to the oofamilies Prismatoolithidae,Elongatoolithidae and Krokolithidae,and it is hypothesized that these three families of eggs correspond to troodontids,oviraptorids and crocodiloids,respectively.Comparison with egg fossils from Nanxiong Basin,Heyuan Basin and Ganzhou Basin highlights the similarity between these egg assemblages and those from Nanxiong Basin.The egg fossils found in the Sanshui and the Dalangshan for-mations enrich the known faunal types in the research area and facilitate further studies on the diversity of Late Cretaceous vertebrate assemblages in the Sanshui Basin.

Hole arrayed metal-insulator-metal structure for surface enhanced Raman scattering by self-assembling polystyrene spheres

A fabrication process based on the self-assembling polystyrene spheres is proposed to obtain hole arrayed metal-insulator-metal （HA-MIM） structure for surface enhanced Raman scattering （SERS）. The localized field enhancement aroused by the gap resonance in the HA-MIM structure is analyzed by finite-different time domain （FDTD） method. With reference to the theory result, the structure is experimentally fabricated and the Raman scattering spectrum of rhodamine 6G （R6G） is measured by a miniaturized Raman spectrometer. The results shows that the enhancement factor is 3.85 times higher than the control sample with single layered metal hole array. The fabrication process to obtain the HA-MIM SERS substrate is reproducible, fast, large area and low cost.