A sample-to-answer polymer lab-on-a-chip with superhydrophilic surfaces using a spray layer-by-layer nano-assembly method

In this research, an innovative 'smart' sample-to-answer (S-to-A) polymer lab-on-a-chip (LOC) platform with superhydrophilic surfaces has been proposed, developed, and fully characterized for point-of-care clinical testing (POCT) applications. A spray layer-by-layer (LbL) nano-assembly method has been developed and applied for the development of a superhydrophilic surface on a cyclic olefin copolymer (COC). Then, the developed superhydrophilic surfaces were designed and optimized for three device applications such as lateral transportation of whole blood in the device by capillary pumping, on-chip whole blood/plasma separation with an asymmetric capillary force, and detection using a capillary-driven lateral flow colorimetric assay. With the integration of the developed three devices, the S-to-A polymer LOC platform has been successfully developed for the calorimetric assay of bovine serum albumin (BSA) from a whole blood sample without an external power source.;One of the most important achievements in this research was to realize a new on-chip whole blood/plasma separator driven by asymmetric capillary forces. A nanoporous superhydrophilic surface by spray LbL nano-assembly method and a patterned hydrophobic patch were combined to attain asymmetric capillary forces through the microchannel for the effective separation of blood plasma from whole blood without external power resources. The blood plasma was effectively separated from the whole blood through the accumulated blood cells which worked as a so-called `self-built-in blood cell microfilter'. A spray LbL nano-assembly method developed for the superhydrophilic surfaces was simple, functional, practical, cost-effective, and a manufacturable tool for selectively constructing nanoporous multilayer surfaces at room temperature. The resulting multilayer networks were effectively characterized by several characterization methods.;The newly developed superhydrophilic surfaces were also applied for the realization of a capillary-driven lateral flow colorimetric assay platform targeted to a S-to-A polymer LOC device. This superhydrophilic surface used for a capillary-driven lateral flow colorimetric assay has shown superior properties to the paper-based lateral flow colorimetric assay. Both high-quality blood plasma separated from whole blood and its quantitative analysis were simultaneously demonstrated in the S-to-A polymer LOC platform that was constructed by the integration of the on-chip blood plasma separator with the capillary-driven colorimetric assay. The limit of detection (LoD) in the S-to-A polymer LOC platform for BSA was comparable to or better than that of the paper-based colorimetric assay.;In conclusion, the 'smart' S-to-A polymer LOC device developed in this research is a generic platform for the POCT, particularly useful for physicians, nurses, patients in the developing world, in poor-resource settings, in the field, and in home-care settings because it is simple, disposable, inexpensive, and a user-friendly diagnostic device. The S-to-A polymer LOC platform is also envisaging a mass production for low-cost POCT applications.