Particle Manipulation-on-chip: Using programmable hydrodynamic forcing in a closed loop

The precise manipulation of particles and droplets is crucial to many microfluidic applications in engineering. The design of microfluidic devices is generally tailored to perform a specific task, with each specific application requiring a unique and fixed design. In this way, using a single device to perform multiple analyses of a wide range of specimens, from biological to chemical specimens, is unfeasible. Here, we address this issue and present a microfluidic approach that dynamically controls the hydrodynamic flow and the streamlines to realize complex multi-particle manipulations within a single device. Our approach combines the design of a flow-through microfluidic flow cell together with an optimization procedure to find a priori optimal particle path-lines, and a Proportion-Integral-Derivative-based (PID) feedback controller to provide real time control over the particle manipulations. In our device, particles are manipulated with hydrodynamic forces, by using a uniform flow through the flow cell and three inlets perpendicular to the flow cell. The streamlines within the device are manipulated by injecting or extracting fluid through the three inlets. We demonstrate the robustness of our approach by performing multiple functions within the device, including particle trapping, particle sorting, particle separation and assembly. We show that the real time control procedure affords accurate particle manipulation, with a maximum error on the order of the diameter of the particle. Our particle manipulation approach is particularly well suited to biological samples and living cells.Fluid Mechanic