Gas Adsorption Response of Piezoelectrically Driven Microcantilever Beam Gas Sensors: Analytical, Numerical, and Experimental Characterizations

Abstract

This work presents an approach for the estimation of the adsorbed mass of 1,5-diaminopentane (cadaverine) on a functionalized piezoelectrically driven microcantilever (PD-MC) sensor, using a polynomial developed from the characterization of the resonance frequency response to the known added mass. This work supplements the previous studies we carried out on the development of an electronic nose for the measurement of cadaverine in meat and fish, as a determinant of its freshness. An analytical transverse vibration analysis of a chosen microcantilever beam with given dimensions and desired resonance frequency (> 10 kHz) was conducted. Since the beam is considered stepped with both geometrical and material non-uniformity, a modal solution for stepped beams, extendable to clamped-free beams of any shape and structure, is derived and used for free and forced vibration analyses of the beam. The forced vibration analysis is then used for transformation to an equivalent electrical model, to address the fact that the microcantilever is both electronically actuated and read. An analytical resonance frequency response to the mass added is obtained by adding simulated masses to the free end of the beam. Experimental verification of the resonance frequency response is carried out, by applying known masses to the microcantilever while measuring the resonance frequency response using an impedance analyzer. The obtained response is then transformed into a resonance frequency to the added mass response polynomial using a polynomial fit. The resulting polynomial is then verified for performance using different masses of cantilever functionalization solution. The functionalized cantilever is then exposed to different concentrations of cadaverine while measuring the resonance frequency and mass of cadaverine adsorbed estimated using the previously obtained polynomial. The result is that there is the possibility of using this approach to estimate the mass of cadaverine gas adsorbed on a functionalized microcantilever, but the effectiveness of this approach is highly dependent on the known masses used for the development of the response polynomial model.

Modeling Nonlinear Dynamics of Functionalization Layers: Enhancing Gas Sensor Sensitivity for Piezoelectrically Driven Microcantilever

“…For this study, an increase in resonance frequency was observed up to a concentration of ∼87 ± 2 ppm v . Beyond this point, the change in resonance frequency is due to added mass from adsorption, and quantification of this response can be found in our previous study, which elaborates on the parametrized impact of adsorption-induced damping within the context of response factors. It can therefore be assumed that for low concentrations of adsorbed cadaverine, the elastic dynamics of the functionalization layer have a significant impact on the response obtained and decrease with an increase in the mass of cadaverine adsorbed.…”

“…The deviation from the response model observed for higher concentrations is attributed to the dominance of damping over the adsorption-induced functionalization layer dynamics. 31…”

“…A reduced order approximation of eq can be derived using the Galerkin method, using an approximation of v ( s , t ) evaluated as v false( s , t false) = ∑ n = 1 ∞ ψ n false( s false) q n false( t false) where ψ n ( s ) are a set of admissible functions representing the mode shapes of the microcantilever whose definition can be found in ref . q n ( t ) denotes generalized temporal coordinates.…”

“…where ψ n (s) are a set of admissible functions representing the mode shapes of the microcantilever whose definition can be found in ref 31. q n (t) denotes generalized temporal coordinates.…”

“…The response of the PD-MC is nonlinear, with an increase in resonance frequency for low cadaverine concentrations (for fresh samples or when the temperature is low) and a polynomial-natured decrease in resonance frequency for higher concentrations. We have shown in our previous work the parametrization of the response of a functionalized PD-MC 31 for higher concentrations of cadaverine. In this regard, ignoring the nonlinearity effects limits the sensor range to the dotted window.…”