“Sketch and Peel” Lithography for High-Resolution Multiscale Patterning

We report a unique lithographic process, termed “Sketch and Peel” lithography (SPL), for fast, clean, and reliable patterning of metallic structures from tens of nanometers to submillimeter scale using direct writing technology. The key idea of SPL process is to define structures using their presketched outlines as the templates for subsequent selective peeling of evaporated metallic layer. With reduced exposure area, SPL process enables significantly improved patterning efficiency up to hundreds of times higher and greatly mitigated proximity effect compared to current direct writing strategy. We demonstrate that multiscale hierarchical metallic structures with arbitrary shapes and minimal feature size of ∼15 nm could be defined with high fidelity using SPL process for potential nanoelectronic and nano-optical applications

Sensitive Surface-Enhanced Raman Scattering Detection Using On-Demand Postassembled Particle-on-Film Structure

Highly sensitive and low-cost surface-enhanced Raman scattering (SERS) substrates are essential for practical applications of SERS. In this work, we report an extremely simple but effective approach to achieve sensitive SERS detection of molecules (down to 10^–10 M) by using a particle/molecule/film sandwich configuration. Compared to conventional SERS substrates which are preprepared to absorb analyte molecules for detection, the proposed sandwich configuration is achieved by postassembling a flexible transparent gel tape embedded with plasmonic nanoparticles onto an Au film decorated with to-be-detected analyte molecules. In such a configuration, the individual plasmonic gel tape and Au film have low or no SERS activity but the final assembled sandwich structure shows strong SERS signal due to the formation of numerous hot spots at the particle–film interface, where the analyte molecules themselves serve as both spacer and signal probes. Because of its simple configuration, we demonstrate that the proposed SERS substrate can be obtained over a large area with extremely low cost. Particularly, because of the on-demand nature and the flexibility, such a postassembly strategy provides an ideal solution to detect the pesticide residue on fruit surfaces with significantly enhanced sensitivity