Recent years have seen the emergence of a number of devices designed to separate specific cells of interest from background cells and particulate. Applications range from the isolation of stem and bone marrow cells from bone marrow aspirates to the detection of abnormal and malignant cells from spinal and pleural fluids. Of particular interest have been microfluidic devices, due to their ability to process relatively large volumes on a small surface area, and the favorable fluidics within. Attempts at improving the interaction between flowing cells and the adhesive wall have been carried out with the incorporation of wall features that create microvortices and with the introduction of obstacles that span the flow regime. Significant drawbacks of these technologies include the need for complex and sophisticated microfabrication techniques and difficulties removing captured. The focus of this research is to investigate the utility of cell capture in a relatively simple microfluidic device that is enhanced by the modulation of surface roughness through the addition of a coating of naturally-occurring halloysite nanotubes. This nanotube coating is characterized thoroughly and shown to create significant advantages in the capture of viable target cells, and its utility proven in the ability to capture primary circulating tumor cells from peripheral blood samples of cancer patients. Comparison to today's gold standard for circulating tumor cells enumeration demonstrates the advantages offered by this device. Finally, it is established that enhancements in the purity of the captured cell population is achieved due to the remarkable activity of the halloysite nanotube coating in reducing the capture of and preventing the spreading of contaminating leukocytes within the device.