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.