Abstract
Nanomechanical sensors and their arrays have been attracting significant attention for detecting, distinguishing, and identifying target analytes. In the static mode operation, sensing signals are obtained by a concentration-dependent sorption-induced mechanical strain/stress. The analytical models for the static mode nanomechanical sensing with viscoelastic receptor layers have been proposed, while they are not formulated for practical conditions, such as multistep injection-purge cycles. Here, we derive an analytical model of viscoelastic material-based nanomechanical sensing by extending the theoretical model via solving differential equations with recurrence relations. The presented model is capable of reproducing the transient behaviors observed in the experimental signal responses with multistep injection-purge cycles, including drifts and/or changes in the baseline. Moreover, this model can be utilized for extracting viscoelastic properties of the receptor material/analyte pairs as well as the concentrations of analytes accurately by fitting a couple of injection-purge curves obtained from the experimental data. The parameters of the model that best fit the data can be used for predicting the entire signal response.
Highlights
Nanomechanical sensors have gained significant attention as powerful tools for detecting target analytes,1–7 especially odors that are composed of a complex mixture of gaseous molecules.8–11 An array of nanomechanical sensors can be potentially used as a sensing unit for artificial olfaction
The analytical models for the static mode nanomechanical sensing with viscoelastic receptor layers have been proposed, while they are not formulated for practical conditions, such as multistep injection-purge cycles
In the case of so-called static mode operation, sensing signals are obtained by measuring mechanical stress/strain induced by the sorption of target molecules in a receptor layer designed to respond to a wide range of chemical classes
Summary
Nanomechanical sensors have gained significant attention as powerful tools for detecting target analytes, especially odors that are composed of a complex mixture of gaseous molecules. An array of nanomechanical sensors can be potentially used as a sensing unit for artificial olfaction. We derive a general analytical expression that includes the sorption kinetics and the viscoelastic stress relaxation This model is applicable to the multistep injectionpurge cycles without reaching a steady-state, allowing us to effectively analyze the sensor response even if it drifts and/or changes its baseline over time. On the basis of the theoretical model proposed by Wenzel et al., we formulated a new model by deriving analytical solutions of overall transient (and steady-state) responses with multistep injection-purge cycles This analytical model agrees well with sensor responses experimentally measured using a nanomechanical Membrane-type Surface stress Sensor (MSS) coated with viscoelastic materials because of the high robustness and high sensitivity of MSS.. This analytical model agrees well with sensor responses experimentally measured using a nanomechanical Membrane-type Surface stress Sensor (MSS) coated with viscoelastic materials because of the high robustness and high sensitivity of MSS. The curve fitting provides several physical parameters and analyte concentration that can be utilized as solid features for scientifically reliable pattern recognition-based analyses.
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