Mimicking Neuromuscular Junctions Using Controlled Crystallization of Solvents: A Surface and Interface Engineering Technique for Polymers

Abstract

Recently, crystallization engineering has become a novel processing technique for various materials, including ceramics, polymers, and composites. Herein, a novel processing technology of polymers based on controlled directional crystallization was developed for biomimetic surfaces and interfaces. Solvent was allowed to come into contact with a polymer surface for a limited time, followed by controlled crystallization of the solvent along a temperature gradient perpendicular to the surface. As a result, perpendicular pores of well-defined patterns were successfully prepared, as well as adhesive-free strong interfaces mimicking neuromuscular junctions. By increasing the temperature of the polymer or solvent contact time, the pore depth and contact angle increased. Highly hydrophobic surfaces of polycarbonate were efficiently prepared, and interfacial adhesion with polydimethylsiloxane was improved by more than 4-fold. This novel processing technique based on crystal engineering could open completely new application possibilities, particularly for biomedical devices, soft lithography, microfabrication, soft sensors, and flexible and stretchable electronics.

In Situ Incorporation of Pores and Nanoparticles into Polymer Surfaces Using Melt Crystallization

“…If a solvent is allowed to come into contact with a polymer surface at a temperature lower than the crystallization temperature of the solvent, limited dissolution of the polymer surface occurs, followed by DMC . By controlling the temperature and its gradient, the pore morphology could be controlled.…”

“…By controlling the temperature and its gradient, the pore morphology could be controlled. The pore depth was controlled from a few microns to 400 µm by changing the initial temperature of the solvent or the contact time of the solvent, whose temperature profiles during the treatment were investigated in detail . Superior adhesion strength was also reported using the prepared porous surfaces, e.g., 7.3‐fold increases in adhesion compared to the plasma treated surfaces .…”

“…The pore depth was controlled from a few microns to 400 µm by changing the initial temperature of the solvent or the contact time of the solvent, whose temperature profiles during the treatment were investigated in detail . Superior adhesion strength was also reported using the prepared porous surfaces, e.g., 7.3‐fold increases in adhesion compared to the plasma treated surfaces . We hypothesize that if we disperse nanoparticles (secondary components) in the solvent, the nanoparticles will mix with the dissolved polymer chains during dissolution, leading to the formation of nanocomposite pore walls.…”

“…To confirm this hypothesis, we chose three different materials for the dispersion: hydrophilic inorganic nanoparticles (silica), relatively hydrophobic nanoparticles (AlN), and hydrophobic organic particles (poly(dimethylsiloxane); PDMS). Only one polymer, polycarbonate (PC), was investigated here because the basic method of limited dissolution and surface melt crystallization has already been shown to be suitable for various polymers . PC, polyurethane, polyvinyl alcohol, and polystyrene were successfully treated using 1,4‐dioxane and water using temperature gradient generated by liquid nitrogen.…”

“…The cross‐sectional image in Figure S1b, Supporting Information shows that the porous surface had a depth of ca. 150 µm, which can be controlled by manipulating the treatment time and temperature …”