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To study an environmental or biological solution, it is essential to separate its constituents. In this study, a 3D-deformable dynamic microfilter was developed to selectively separate the target substance from a solution. This microfilter is a fine metallic nickel structure fabricated using photolithography and electroplating techniques. It is gold-coated across its entire surface with multiple slits of 10–20 μm in width. Its two-dimensional shape is deformed into a three-dimensional shape when used for fluid separation due to hydrodynamic forces. By adjusting the pressure applied to the microfilter, the size of the gap created by deformation can be changed. To effectively isolate the target substance, the relationship between the solution flow rate and the extent of microfilter deformation was investigated. The filtration experiments demonstrated the microfilter’s ability to isolate the target substance with elastic deformation without undergoing plastic deformation. Additionally, modification of the microfilter surface with nucleic acid aptamers resulted in the selective isolation of the target cell, which further demonstrates the potential application of microfilters in the isolation of specific components of heterogeneous solutions.

This paper presents a three-dimensional deformable microfilter modified with a nucleic-acid aptamer for capturing of target cells. Separating and capturing target cells from the fluid is very important for health diagnosis and medical diagnosis by liquid biopsy. The presented microfilter permits the separation of arbitrary size because the opening gap of the microfilter is three-dimensionally transformed by fluidic force. The deformation of the microfilter is able to be changed by adjusting the fluidic force. Also, the presented microfilter permits the specific capturing of target cells by specifically adsorbing ability of a nucleic-acid aptamer. In this experiment, the cancer cell was used as a target cell. The nucleic-acid aptamer that has a specific adsorbing ability to epithelial cell adhesion molecules was used for capturing the cancer cell. The results of experiment, the target cells were effectively captured by nucleic-acid aptamer modified microfilter.