Mechanism for Cell Separation Based on Size and Deformability Using Microfluidic Ratchets

We present a mechanism for separating cells based on size and deformability using microfluidic ratchets created using micrometer-scale funnel constrictions. The force required to deform individual cells through such constrictions is directionally asymmetric, enabling rectified transport from oscillatory flow of the bulk fluid. Combining ratcheting with simple filtration enables cell separation based on size and deformability. Based on this concept, we developed a microfluidic device using a 2D matrix of funnel constrictions. We demonstrate highly selective separation of two cell types while retaining viability, study the effect of oscillation flow pressure, and confirm the irreversible nature of the ratcheting process.