A microfluidic platform for automatic continuous flow layer‐by‐layer assembly of polymer multilayered nanofilms

Abstract Capillary flow layer‐by‐layer assembly is a microfluidic platform for high throughput preparation and screening of multilayered polymer nanofilms. However, it is time‐consuming and labor‐intensive, since the switching of polyelectrolyte solutions is done manually. As the emergence of flow chemistry and microdevices for artificial intelligence‐based lab automation, an automatic system that can switch polymer solutions and washing liquids is urgently needed for building functional LbL films inside microfluidic devices. Herein, we construct a continuous flow (ConF)‐layer‐by‐layer (LbL) device that can automatically fabricate polymer nanofilms inside a microfluidic device. By including a flow separator and a mixer (a model polyelectrolyte pair), chitosan and carboxymethyl cellulose can be deposited inside a microfluidic device using the ConF‐LbL system. Resulting nanofilms are studied by investigating thickness and surface roughness of the nanofilms and comparing with the other conventional LbL methods. The acid dissolution method was used to compare the differences in stability between nanofilms made from ConF‐LbL and static immersive method in similar conditions. Furthermore, by using one optimized film formulation for coating on the inside walls of a microfluidic chip, we successfully demonstrated the ability of this device to capture cancer cells in whole blood. This ConF‐LbL platform is expected to be a convenient tool to coat functional nanofilms inside microdevices for biomedical and sensor applications.