A Microfluidic Device With Circular Microchannels T-crossed Via Wall-through-hole: Its Micromixing Effects And Initial Application In Particle Synthesis

Microfluidics is an emerging technology featured by processing and manipulation of nano-volume liquid, or even smaller, in tens to hundreds of micro-scale channels. Recently, realizing mixing of nanoliter volume, or even smaller, has been a significant aspect of microfluidic in microchannel field. It is appealing to researchers that the ability to control small volume liquid is used to synthesize micro/nanoparticles. And achievements have seen the attraction. Here, we applied microwire-molding technique to design and fabricate a microfluidic device with circular microchannels T-crossed via wall-through-hole and investigated into the mixing effect and ability to synthesize particles.First, based on the feasibility of micro-wire molding technique, we designed and fabricated a microfluidic device with circular microchannels T-crossed, which featured a wall-through-hole. This structure was supposed to cause the flowing fluid to shrink, enlarge and redirect.Behaviors of flowing fluid were demonstrated by both numerical simulation and fluid tracking method. In simulation experiment, micro-circular channel diameters of 100μm, 80μm and 60μm was done with various central axis distances d, respectively. By analyzing velocity vector of micro-circular channel, we concluded that T-type micro-circular channel with diameter of 80μm, d of 70μm had the best performance of mixing.In the fluid tracking experiment, we conducted colorful solution mixing. Red and green solutions were injected into micro-circular channel by syringe pump at different flow rate, so as to observe and analyze mixing effect in micro-circular channel. It was concluded that optimal mixing effect could be realized by keeping the same flow rate and maintaining at a low rate of 2~8μL/min.To further demonstrate the mixing effect of such device, micro/nanoparticles were co-precipitationally synthesized. By configuring with various concentrations of the reaction solution and comparing the experimental results, we could draw the optimal reaction conditions for synthesizing microparticles: concentration of Group-4, syringe pump flow 2-8μL/min and the pH> 9. We characterized morphology of synthesized microparticles with inverted fluorescence microscope, Confocal Laser Scanning Microscope(CLSM) and atomic force microscopy(AFM). The results showed that under these conditions, we obtained microparticles.The aforementioned achievements show that the microfluidic device with circular microchannels T-crossed via wall-through-hole based on microwire-molding technique is an micromixing device and can be applied in the micromixing areas.