In medical and clinical research,circulating tumor cells (CTCs) are identified from the cancer patients blood,which can meet the existing medical demand to monitor disease progress during a course of treatment and to help determine recurrent disease [1].Current strategies for isolating CTCs are mostly based on antibody against EpCAM,a membrane protein that is expressed on almost all carcinomas.However,the EpCAM antibody is disadvantageous due to its large size and instability,which limits its application in cancer imaging and CTC detection [2].In this study,we have successfully identified DNA ligands known as aptamers that bind EpCAM specifically.The aptamers were found to bind EpCAM expressed cell lines,not negative cell lines (Fig.1).Flow cytometry analysis results indicated that SYL3C aptamer was able to recognize target cancer cells from mixed cells in cell media (Fig.2).When used to capture cancer cells,up to 63% cancer cell capture efficiency was achieved with about 80% purity (Fig.3).Additional optimization of the experimental conditions will further improve the capture efficiency and purity.Microfluidic devices with novel microstructure designs such as arrays of pillars,slots or nanowires,can be constructed to enhance the interactions with cells flowing in the microchannels,and a 3D aptamer network on microfluidic channel can also be built to enhance the binding efficiency by the multivalent effect.The EpCAM binding aptamers have great potential for use in targeted cancer therapy,cancer imaging,and circulating tumor cell detection.