Exploration of a Flexible Metasurface for Strain Sensors: A Perspective from 2D Grating Fabrication to Spectral Characterization

Abstract

The flexible plasmonic metasurface is a novel optical device consisting of a large number of subwavelength-sized noble metal (gold, silver, etc.) structures arranged in a specific pattern on a flexible substrate. The usual method for a fabricating flexible metasurface is to build nanostructures on rigid substrates and then transfer them to flexible substrates. However, problems such as structural distortion and structural loss can occur during fabrication. To address these issues, this work improved the process to fabricate and characterize a flexible plasma 2D grating–a type of metasurface composed of gold cubelets with a thickness of 50 nm and a side length of 250 nm. First, an electron beam lithography method modified by proximity effect correction was used to fabricate nanostructures on a rigid substrate. Then, the structures were transferred by a chemical functionalization and a sacrificial layer etching method. In addition, the feasibility of using flexible plasmonic 2D gratings as strain sensors was investigated in this work through a stretching test. Experimental results show that electron beam lithography improved by correcting the proximity effect enabled the fabrication of more precisely shaped nanostructures; the chemical functionalization method significantly improved the transfer yield; and the spectroscopic analysis in the stretching test demonstrated the potential of the flexible plasmonic 2D gratings for sensing applications.