Analysis of Intrinsic Stochastic Fluctuations of the Time Response of Adsorption-Based Microfluidic Bio/Chemical Sensors: the Case of Bianalyte Mixtures

Real-time in situ operation of bio/chemical sensors assumes detection of chemical substances or biological specimens in samples of complex composition. Since sensor selectivity cannot be ideal, adsorption of particles other than target particles inevitably occur on the sensing surface. That affects the sensor response and its intrinsic fluctuations which are caused by stochastic fluctuations of the numbers of adsorbed particles of all the adsorbing substances. In microfluidic sensors, such response fluctuations are a result of coupled adsorption, desorption and mass transfer (convection and diffusion) processes of analyte particles. Analysis of these fluctuations is important because they constitute the adsorption-desorption noise, which limits the sensing performance. In this work we perform the analysis of fluctuations by using a stochastic model of sensor response after the steady state is reached, in the case of two-analyte adsorption, considering mass transfer processes. The results enable estimation of the ultimate sensing performance of adsorption-based microfluidic bio/chemical sensors of different sensing areas, operating in bianalyte mixture environments.