Control mechanism of an organic self-regulating microfluidic system

The control mechanism and fluid dynamic properties of a previously developed organic pH regulation system are analyzed. The system regulates an output fluid stream to a pH of 6.7 with varying input flow rates. A pH sensitive hydrogel post acts as the feedback pH sensor and flow regulator. The control mechanism of the system is studied through numerical modeling of the regulator and the model is validated through experimentation. Analysis of the fluid dynamics at a T-channel junction, in which two buffer streams merge into one, is performed by solving the Navier-Stokes equation with commercial software. Various areas of a star-shaped orifice are occluded by a flexible membrane to throttle the rate that compensating buffer is fed back into the system. The relationship between orifice open area and volume of compensating buffer through the orifice was analyzed numerically. The axial and lateral visualization of the hydrogel post was obtained via optical microscopy. The model of the regulation system successfully predicts experimental results.