# Carbon Dioxide Gas Sensor Based on Polyhexamethylene Biguanide Polymer Deposited on Silicon Nano-Cylinders Metasurface

## TL;DR

This paper presents a CO2 gas sensor using a metasurface with a polymer layer, achieving high sensitivity through changes in resonance wavelength.

## Contribution

A novel CO2 gas sensor design using a metasurface with polyhexamethylene biguanide polymer for high sensitivity detection.

## Key findings

- The sensor detects CO2 concentrations up to 524 ppm with a sensitivity of 17.3 pm/ppm.
- The resonance wavelength blueshifts due to CO2 absorption in the polymer layer.
- The metasurface design is polarization and angle of incidence independent.

## Abstract

In this paper, we have numerically investigated a metasurface based perfect absorber design, established on the impedance matching phenomena. The paper comprises of two parts. In the first part, the device performance of the perfect absorber—which is composed of silicon nano-cylindrical meta-atoms, periodically arranged on a thin gold layer—is studied. The device design is unique and works for both x-oriented and y-oriented polarized light, in addition to being independent of the angle of incidence. In the second part of the paper, a CO2 gas sensing application is explored by depositing a thin layer of functional host material—a polyhexamethylene biguanide polymer—on the metasurface. The refractive index of the host material decreases due to the absorption of the CO2 gas. As a result, the resonance wavelength of the perfect absorber performs a prominent blueshift. With the help of the proposed sensor design, based on metasurface, the CO2 gas concentration range of 0–524 ppm was detected. A maximum sensitivity of 17.3 pm/ppm was acquired for a gas concentration of 434 ppm. The study presented in this work explores the opportunity of utilizing the metasurface perfect absorber for gas sensing applications by employing functional host materials.