Critical overview and comparison between models for adsorption-desorption noise in bio-chemical sensors

We critically review existing models for the adsorption-desorption noise in bio-chemical sensors, in particular the model based on simplified forward Kolmogorov equation and the models based on Langevin sources. For the latter models, we propose a generalized version to handle cases beyond the branched surface reactions (a binding site that can be alternatively occupied by different ions/molecules) and the chained reaction (a binding site that sequentially binds with ions/molecules). The models are benchmarked against kinetic Monte Carlo (kMC) simulations considering relevant case studies such as pH-sensitive ions, selective molecules binding on a functionalized surface and multi-layer adsorption on bare surfaces. It is found that although the mathematical formulation of the modeling approaches appears different, when dealing with independent binding sites, they are fully equivalent and perfectly match the kMC results. The case of competitive binding considering the correlation between the occupation of the binding sites has also been analyzed.