2.5-Dimensional Parylene C micropore array with a large area and a high porosity for high-throughput particle and cell separation

Large-area micropore arrays with a high porosity are in high demand because of their promising potential in liquid biopsy with a large volume of clinical sample.However,a micropore array with a large area and a high porosity faces a serious mechanical strength challenge.The filtration membrane may undergo large deformation at a high filtration throughput,which will decrease its size separation accuracy.In this work,a keyhole-free Parylene molding process has been developed to prepare a large(>20 mm×20 mm)filtration membrane containing a 2.5-dimensional(2.5D)micropore array with an ultra-high porosity(up to 91.37% with designed pore diameter/space of 100μm/4μm).The notation 2.5D indicates that the large area and the relatively small thickness(approximately 10μm)of the fabricated membranes represent 2D properties,while the large thickness-to-width ratio(10μm/<4μm)of the spaces between the adjacent pores corresponds to a local 3D feature.The large area and high porosity of the micropore array achieved filtration with a throughput up to 180 mL/min(PBS solution)simply driven by gravity.Meanwhile,the high mechanical strength,benefiting from the 2.5D structure of the micropore array,ensured a negligible pore size variation during the high-throughput filtration,thereby enabling high size resolution separation,which was proven by single-layer and multi-layer filtrations for particle separation.Furthermore,as a preliminary demonstration,the prepared 2.5-dimensional Parylene C micropore array was implemented as an efficient filter for rare cancer cell separation from a large volume,approximately 10 cells in 10 mL PBS and undiluted urine,with high recovery rates of 87±13% and 56±13%,respectively.