Analysis of the Fundamental Detection Limit in Microfluidic Chemical and Biological Sensors

Abstract

Detection limits in microfluidic chemical and biological sensors, which determine the range of analyte concentrations reliably detectable by the sensor, are important sensor parameters. The lower limit of detection, defined as the lowest concentration that can be distinguished from noise, has its minimum determined by the fundamental adsorption-desorption (AD) noise, inevitable in adsorption-based devices. In this work, we analyze this fundamental detection limit, particularly considering the influence of mass transfer processes in microfluidic devices. For that purpose, we derive the expression for the sensor’s signal-to-noise ratio (SNR), which takes into account the AD noise, and then the equation for the minimal analyte concentration at which the SNR has a sufficiently high value for reliable analyte detection. Subsequently, we analyze the mass transfer influence on the sensor’s maximal achievable signal-to-noise ratio and on the fundamental detection limit. The results of the analysis show a significant mass transfer influence on these important sensor performance metrics. They also provide guidelines for achieving the sensor’s best possible detection performance through the optimization of the sensor design and operating conditions.