Dynamic generation of power function gradient profiles in a universal microfluidic gradient generator by controlling the inlet flow rates.

We report a two-inlet universal microfluidic gradient generator capable of generating gradient profiles of the functional form x p in the same device by controlling only the inlet flow rates. We have developed an analytical model to predict the inlet flow rates needed to generate a user-specified gradient profile at the outlet. We have validated this model by performing both COMSOL simulations and experiments. Our experiments show an excellent match between the target functions ( x 0.33 , x 1 , x 2 and x 3 ) and the gradient profiles generated in this device. Unlike the universal gradient generators reported earlier, our device does not require changing the positions of the internal barriers for each new gradient profile, thereby making it easier for the user to operate this device.