A series of symmetrical and asymmetrical microfluidic T-sensors with different inlet angles were fabricated to study the mixing characteristics of a T-type microstructure for generating concentration gradient. Computational fluid dynamics (CFD) simulations showed that the concentration gradient, transition zone and diffusion length were different for various configurations and inlet angles. Quick mix and sharp concentration gradient occurred in the asymmetrical structure with large inlet angle. The observed concentration gradients in the fabricated microchannel were consistent with the theoretical prediction. In this microstructure, stagnant zone and z-direction diffusion also affected the concentration gradient. Based on the simulation results, the microfluidic structure was optimized to generate desired concentration gradient for a cell-based study.

Laser-based biosensors Biosensors using lasers are defined as sensors for biological applications which are based on laser technology. There is a series of biosensors which use laser-based detection methods such as surface plasmon resonance, fiber optics, waveguides, microcantilevers, and so on. Due to their high sensitivity and precision, laser-based biosensors have been widely used in many fields, including immunoassays and drug screening. Biological sensing is a process which obtains selected information about biological macromolecular interactions in real time. Biosensors are miniaturized analytical devices based on biological sensing technology, which commonly comprise a biorecognition molecular layer immobilized on the interface between the analyte solution and a signal transducer (Fig. 1) [1]. The main part of a typical biosensor is this biologically sensitive layer that converts the biological change into a detectable signal, which is subsequently transl ...