###### Abstract  
Biosensors are favored devices for the fast and cost-effective detection of biological species without the need for laboratories. Microfluidic integration with biosensors has advanced their capabilities in selectivity, sensitivity, controllability, and conducting multiple binding assays simultaneously. Despite all the improvements, their design and fabrication are still challenging and time-consuming. The current study aims to enhance microfluidic-integrated biosensors' performance. Three different functional designs are presented with both active (with the help of electroosmotic flow) and passive (geometry optimization) methods. For validation and further studies, these solutions are applied to an experimental setup for DNA hybridization. The numerical results for the original case have been validated with the experimental data from previous literature. Convection, diffusion, migration, and hybridization of DNA strands during the hybridization process have been simulated with finite element method (FEM) in 3D. Based on the results, increasing the velocity on top of the functionalized surface, by reducing the thickness of the microchamber in that area, would increase the speed of surface coverage by up to 62%. An active flow control with the help of electric field would increase this speed by 32%. In addition, other essential parameters in the fabrication of the microchamber, such as changes in pressure and bulk concentration, have been studied. The suggested designs are simple, applicable and cost-effective, and would not add extra challenges to the fabrication process. Overall, the effect of the geometry of the microchamber on the time and effectiveness of biosensors is inevitable. More studies on the geometry optimization of the microchamber and position of the electrodes using machine learning methods would be beneficial in future works. engineering: computational fluid dynamics; mass transfer in microfluidic systems; biosensor design and optimization; electroosmotic flow +
Footnote †: journal: Applied Sciences  
attention towards microfluidic-integrated biosensors is enhanced extra by its capability of detecting a low concentration of biomarkers [7; 8]. It also has application in various fields such as real-time health monitoring, point-of-care (POC) disease diagnosis, significant data statistics in health management, food safety, and environmental monitoring [9; 10; 11]. Although there has been a significant improvement in current biosensors, the design and fabrication are still challenging and time-consuming. These challenges are bolder in bio-receptors and assay matrix design, achieving specific binding and detecting low concentration target molecules within a low-volume sample [12; 13; 14; 15; 16]. Scientists have been using various active and passive methods to improve biosensors' sensing and fabrication to resolve these challenges. In passive methods, sensing is enhanced with new materials and geometry optimization, while in active methods, moving parts and external forces such as electric or pressure field are applied. Some solution in this matter include utilizing conducting polymers for high-performance biosensors due to their chemical versatility and charge transport [17; 18], use of metamaterials in resonators for better and durable biosensors [19; 20], microelectrode array approach for high sensitivity and live detection [21; 22], and microfluidic approach for DNA analysis [23; 24; 25]. In the current study, to enhance the performance of microfluidic-integrated biosensors, three different types of functional designs, with both active (E cases) and passive (H cases) methods, are presented. It is shown that these designs would improve the efficiency (in sensing and time of detection) by 6-62%, while they would not have a considerable effect on the fabrication and costs. Additional advantages of these designs are simplicity and application to different channels. Finally, for validation and further studies, these methods are applied on an experimental setup of DNA hybridization.