(Invited) Fabrication of Polymer Gels with Double Network Using Multi-Material 2/3D Printing

Abstract

Multi-material systems for additive manufacturing, also known as 3D printing, are used to fabricate the functional objects with different color materials or with the position dependent material properties such as elastic modulus or solubility. The previous work for Fused Deposition Modeling (FDM) method have demonstrated that the multiple print heads or a single head with the mixed-material systems can extrude the complex and composite materials with piling up the multi-material layers connected with the physical bonds between layers.However, few studies have focused on the fabrication of 3D printed gel materials with different materials, and the creation of chemical bonds on the interface between the multi-material layers.In our previous work, 3D printed hollow objects made of gel materials were fabricated with a customized optical 3D printing system, and the 3D printed objects of multifunctional ionic gels incorporating ionic liquid (IL) in the thiol–ene network of thiol-based end-crosslinker and acrylate monomers were fabricated using commercial stereolithography (SLA) system. It was found that optical 3D printing system utilized to fabricate gel materials could create the microscale objects.This study report the design and fabrication of 3D printed polymer gels containing two types of gels using 3D gel printer named “SWIMER”. The double network technique for hydrogels is used for the creation of chemical bonds between two types of gels. Figure shows one of examples of 3D printed gel.This gel consists of two parts: the soft body frame for structural support which is made of nonionic polymer gels and the part which is made of the ionic polymer gels. The nonionic gels with an ordered structure are synthesized by the polymerization of the monomer, N,N-Dimethylacrylamide (DMAAm), and the crosslinker, N, N'-Methylenebisacrylamide (MBAA). The ionic gels are synthesized by the polymerization of the monomer, N-(1,1-Dimethyl-2-(sodiosulfo)ethyl)acrylamide and the same chemicals as the nonionic gels. Chemicals as the ultraviolet (UV) initiator are depending on the wavelength of laser source in the process of how we fabricate the gels.The significant difference in the swelling behavior between the two parts enabled them to be actuated in one direction. We found that by controlling the ion concentration in water they enlarged the solvent-induced strains to 108% in water which is comparable to the polymer actuators driven with high voltage. Figure 1