A generic label-free microfluidic microobject sorter using a magnetic elastic diverter.

Cell sorters play important roles in biological and medical applications, such as cellular behavior study and disease diagnosis and therapy. This work presents a label-free microfluidic sorter that has a downstream-pointing magnetic elastic diverter. Different with most existing magnetic sorters, the proposed device does not require the target microobjects to be intrinsically magnetic or coated with magnetic particles, giving users more flexibility in sorting criteria. The diverter is wirelessly deformed by an applied magnetic field, and its deformation induces a fluid vortex that sorts incoming microobjects, e.g., cells, to the collection outlet. The diverter does not touch samples in this process, reducing the sample contamination and damage risks. This sorter uses a magnetic field generated by off-chip electromagnetic coils that are centimeters away from the device. With simple structure and no on-chip circuits or coils, this device can be integrated with other lab-on-a-chip instruments in a sealed chip, ameliorating the safety concerns in handling hazardous samples. The parallel and independent control of two such diverters on a single chip were demonstrated, showing the potential of doubling the overall throughput or forming a two-stage cascaded sorter. The sorter was modeled based on the Euler-Bernoulli beam theory and its reliability was demonstrated by achieving a raw success rate of 96.68% in sorting 1506 registered microbeads. With a simple structure, the sorter is easy and cheap to fabricate. The advantages of the proposed sorter make it a promising multi-purpose sorting tool in both academic and industrial applications.