In Search of a Green Process: Polymeric Films with Ordered Arrays via a Water Droplet Technique

As an efficient technique for the preparation of polymeric hexagonal orderly arrays, the breath figure (BF) process has opened a modern avenue for a bottom-up fabrication method for more than two decades. Through the use of the water vapor condensation on the solution surface, the water droplets will hexagonally pack into ordered arrays, acting as a template for controlling the regular micro patterns of polymeric films. Comparing to the top-down techniques, such as lithography or chemical etching, the use of water vapor as the template provides a simple fabrication process with sustainability. However, using highly hazardous solvents such as chloroform, carbon disulfide (CS2), benzene, dichloromethane, etc., to dissolve polymers might hinder the development toward green processes based on this technique. In this review, we will touch upon the contemporary techniques of the BF process, including its up-to-date applications first. More importantly, the search of greener processes along with less hazardous solvents for the possibility of a more sustainable BF process is the focal point of this review.