On-the-Fly Formation of Polymer Film at Water Surface

Abstract

The self-propulsion of bodies floating in water is of great interest for developing new robotic and intelligent systems at different scales, and whenever possible, Marangoni propulsion is an attractive candidate for the locomotion of untethered micro-robots. Significant cases have been shown using liquid and solid surfactants that allow an effective propulsion for bodies floating on water to be achieved. Here, we show for the first time a strategy for activating a twofold functionality where the self-propulsion of a floating body is combined with the formation of a polymer thin film at the water surface. In fact, we demonstrate that by using polymer droplets with an appropriate concentration of solvent and delivering such drops at specific locations onto freely floating objects, it is possible to form “on-the-fly” thin polymer films at the free water surface. By exploiting self-propulsion, a polymer thin film can be formed that could cover quite extensive areas with different shapes depending on the motion of the floating object. This intriguing twice-functionality activated though a single phenomenon, i.e., film formation and related locomotion, could be used in perspective to perform complex operations at water surfaces, such as dynamic liquid packaging, cleaning, and moving away floating particles, monolayer films, or macro-sized objects, as discussed in the text.

Multimodal quantitative phase contrast characterization of thin polymeric film

“…In addition, depending on the amount of polymer used and how the polymer is fed into the water, films of different sizes and thicknesses can be obtained. 21,31,32 The experimental process is reported in Fig. 1.…”

“…The process occurs in a few seconds, changing from a single water-air interface to a double interface: water-polymer, polymer-air. In addition, depending on the amount of polymer used and how the polymer is fed into the water, films of different sizes and thicknesses can be obtained 21 , 31 , 32 . The experimental process is reported in Fig.…”

“…The results obtained show that, for future application, interferometry, which is noncontact, nondestructive, and full field, could be used for real time monitoring of the process proposed for membrane formation or eventually to follow the membrane formation on the fly. 31 The results are shown for 2D film, but the method is scalable, and by optimizing the surface tension of the polymer solution, the polymer could spread spontaneously on the surface of the water, forming ultrathin continuous and 3D uniform membranes.…”