This paper presents an evaluation of the sensing properties of a new thin-film stiffness sensing technology that utilizes commercial electret microphones. The analysis is intended to provide researchers with both quantitative and qualitative information on microphone selection for stiffness sensing applications. The sensing properties examined include sensitivity, selectivity and the effect of microphone's electric field. Specifically, a mathematical method to estimate the stiffness sensitivity of a commercial microphone from its acoustic sensitivity is presented. This method utilizes direct measurements of the microphone's parameters to compute sensitivity to thin-film stiffness changes. The discussion on selectivity focuses on undesired cross-stiffness changes in the microphone membrane in the presence of changes in unrelated environmental analytes. Finally, the influence of the microphone's electric field on its stiffness sensing ability is presented.
Bibliographical noteFunding Information:
Financial support for this research was provided by the Minnesota Partnership Program for Biotechnology and Medical Genomics. Film fabrication and characterization were performed at the Nano-fabrication Center and the Characterization Facility at the University of Minnesota, Twin Cities which are supported by the NSF's National Nanotechnology Infrastructure Network (NNIN). The authors thank Prof. Kent R. Mann for assistance on the gas sensing setup and Shankar Sivaramakrishnan for discussions on material properties.
- Carbon dioxide sensor
- Electret microphone
- Stiffness sensor
- Thin-film stiffness