Numerical analysis and experiment of high-efficiency long-term PDMS open-surface mixing chip

Abstract

The traditional closed-channel polydimethylsiloxane (PDMS) capillary mixer without a delay valve generally encounters backflow problems. In this article, the design of a polyethylene glycol (PEG) coated PDMS mixing meander channel for long-term capillary-actuating with a delay valve and open surface is investigated using numerical analysis and flow-visualization experiments. The self-driven open-surface PEG-PDMS meander mixer exhibits a high mixing extent of more than 90%. The simulation and experiments of the triggering delay valve evidence that two fluids can merge together before the meander channel and then flow into the mixing unit to eliminate the backflow problem. It also enhances an efficient mixing. In addition, the open-surface channel shows a lower channel depth for self-actuating compared to the closed one. In terms of simulation, the mixing extent of both blue and red inks at the position just after the delay valve is about 43% and enhanced to 92% at about 10 mm mixing length after the delay valve. In terms of experiments, the ImageJ analyzed mixing extent is enhanced from about 57% to 96% of mixing extent within the meander channel at the same position. The experiment is in a good agreement with the simulation result.