Microfluidic Gradient Dilution Device

Gradient-based-dilution systems are unique to microfluidics because they work on the principle of laminar flow. Current dilution methods include dilution using micropipettes which is a time-consuming and labour-intensive process, especially when a solution with a particular concentration of a solute has to be diluted into multiple samples with known concentrations and furthermore, this resulting set of samples could be said to have a ‘gradient of concentration’. 

The laminar flow in microfluidic systems offer controlled transport of solute which can be modelled by using computational-fluid-dynamics simulations and the streamlines could then be observed. The density of streamlines represent the flow rates in different branches and offer an easy method to calculate the concentration in different branches.

The following device was made from a 3D printed mould which was designed using CAD software. All the simulations were done in COMSOL Multiphysics 5.3a assuming creeping flow in the channels.

The Velocity Profile

Flow Streamlines (COMSOL)

Concentration Profile (COMSOL)

Testing of MGDD (Capillary flow)