ABSTRACT
The challenges in reliably removing the sacrificial material from fully enclosed microfluidic channels hinder the use of three-dimensional (3D) printing to create microfluidic devices with intricate geometries. With advances in printer resolution, the etching of sacrificial materials from increasingly smaller channels is poised to be a bottleneck using the existing techniques. In this study, we introduce a microfabrication approach that utilizes centrifugation to effortlessly and efficiently remove the sacrificial materials from 3D-printed microfluidic devices with densely packed microfeatures. We characterize the process by measuring the etch rate under different centrifugal forces and developed a theoretical model to estimate process parameters for a given geometry. The effect of the device layout on the centrifugal etching process is also investigated. We demonstrate the applicability of our approach on devices fabricated using inkjet 3D printing and stereolithography. Finally, the advantages of the introduced approach over commonly used injection-based etching of sacrificial material are experimentally demonstrated in direct comparisons. A robust method to postprocess additively manufactured geometries composed of intricate microfluidic channels can help utilize both the large printing volume and high spatial resolution afforded by 3D printing in creating a variety of devices ranging from scaffolds to large-scale microfluidic assays.
ABSTRACT
Isolation and analysis of circulating tumor cells (CTCs) from blood samples present exciting opportunities for basic cancer research and personalized treatment of the disease. While microchip-based negative CTC enrichment offers both sensitive microfluidic cell screening and unbiased selection, conventional microchips are inherently limited by their capacity to deplete a large number of normal blood cells. In this paper, we use 3D printing to create a monolithic device that combines immunoaffinity-based microfluidic cell capture and a commercial membrane filter for negative enrichment of CTCs directly from whole blood. In our device, stacked layers of chemically-functionalized microfluidic channels capture millions of white blood cells (WBCs) in parallel without getting saturated and the leuko-depleted blood is post-filtered with a 3 µm-pore size membrane filter to eliminate anucleated blood cells. This hybrid negative enrichment approach facilitated direct extraction of viable CTCs off the chip on a membrane filter for downstream analysis. Immunofluorescence imaging of enriched cells showed â¼90% tumor cell recovery rate from simulated samples spiked with prostate, breast or ovarian cancer cells. We also demonstrated the feasibility of our approach for processing clinical samples by isolating prostate cancer CTCs directly from a 10 mL whole blood sample.
