Generating 2-dimensional concentration gradients of biomolecules using a simple microfluidic design

Abstract

This study reports a microfluidic device for generating 2-dimensional concentration gradients of biomolecules along the width and length of a chamber and conventional 1-dimensional gradients along the width of its lateral parallel channels. The gradient profile can be precisely controlled by the applied flow rate. The proposed design is simple and straightforward, has a small footprint size compared to previously reported devices such as tree-shape designs, and for the first time, provides capability of generating desired 2D and 1D gradients, simultaneously. The finite element simulation analysis proves the feasibility of the microfluidic device, and the fluorescently labelled IgG antibody is used to demonstrate generated chemical gradients. This simple microfluidic device can be implemented for a wide range of high-throughput concentration gradient applications such as chemotaxis, drug screening, and organs-on-chips.

FIG. 1.

(a) Schematic representation of the microfluidic design. (b) Simulation results for velocity streamlines throughout the chamber by applying the flow rate of 1 μl min⁻¹. (c) Velocity field at the entrance of the five parallel channels. (d) Simulation results for the concentration gradient inside the main chamber and side channels.

FIG. 2.

Simulation results of velocity and concentration gradients. (a) Y-component of velocity fields along represented arc-length directions with different colors (right image) inside the main chamber. (b) X-component of velocity fields along represented arc-length directions (right image). (c) Concentration gradients of two separate biomolecular solutions along the length of the chamber with represented arc-length directions (right image). (d) Concentration gradients along the width of the chamber with represented arc-length directions (right image).

FIG. 3.

Fluorescence microscopy results using FITC conjugated IgG at different inlet flow rates. (a)–(d) Generated 2D gradient patterns inside the chamber. (e)–(j) 3D intensity plots quantifying the fluorescence intensity of the 2D concentration gradients in the main chamber. (k)–(p) Generated 1D gradient in channels 4 and 5. (q) and (r) Intensity diagram of channels 4 and 5 as a function of the channel width showing the 1D gradient inside the channels.

FIG. 4.

Generated 2D gradients of FITC conjugated IgG and Cy3 conjugated IgG inside the chamber together with their 3D intensity plots at different inlet flow rates of (a) 0.1 μl min⁻¹ (b) 1 μl min⁻¹ (c) 2 μl min⁻¹ and (d) 8 μl min⁻¹, obtained using Image J software.