Phononic crystal sensor is a novel technology for sensing applications with high performance. The present work
proposes theoretically a design of gas (CO2) sensor based on a one-dimensional (1D) porous silicon (PSi) phononic
crystal (PnC) sandwiched between two thin rubber layers. The transfer matrix method (TMM) was used for
the numerical modeling of the acoustic waves spectra through the 1DPSi-PnC sensor structure. The results
showed that a resonant mode was created inside the transmission spectrum as a result of the presence of the twosided
rubber layers. Also, the position of the resonant mode was invariant with changing CO2 concentration,
temperature, and pressure. On the contrary, the intensity of the transmitted mode is very sensitive to any change
in these parameters. With increasing the CO2 concentration (from 0% to 90%) and pressure (from 2 atm to 6
atm), the intensity of the resonant mode are significantly increased. While, with increasing temperature (from 20
�C to 200 �C), the intensity of the resonant mode is decreased. These results are correlated directly to the density
of the CO2/air mixture. Therefore, the proposed 1DPSi-PnC sensor can measure CO2 pollutions in the surrounding
air over a wide range of concentration, temperature, and pressure values.
The merits of a gas sensor based on porous materials and PnC structure are numerous. For example, the ease of
fabrication, working under tough conditions, and its capability to sense CO2 pollutions from the surrounding air
directly. Also, the proposed sensor can be developed as a monitor for many gases in industrial and biomedical
applications. Moreover, porous materials enable the proposed design to be compatible with other fluidic components
specifically liquids. Thereby, allowing the proposed gas sensor to be replicated for various fluidic sensing
applications.