Mechanical strength reinforcement by alginate binders in three dimensional powder printing

Abstract

For the 3D printing industry, materials that satisfy the current manufacturing industry are needed. Powder bed and inkjet 3d printing, known as 3D printing (3DP), brings a new level of considerable material flexibility to the manufacturing industry. In addition, with the appropriate choice of powders and binders, sturdy structures that are conformable, colorful, and robust can be produced. Especially, binders are consid-ered to be significant factors due to their transparency, adhesiveness, and reliability. However, one of the problems of using commercial binders is the post processing. The post-treatment process of the 3DP struc-ture is necessary with additional adhesive due to their weak stability, otherwise the structure can get frag-mented or powder dusts at the surface can be easily blown away after the manufacturing. Therefore, blowing the powder and adding cover adhesives are needed, but most of the cover adhesives composed of 2-methoxyethyl-2-cyanoacrylate which also cause skin irritation, serious eye irritation, and respiratory irrita-tion. One of the solutions to not go through with post-treatment process is to combine powders and bind-ers with stronger and biocompatible adhesives. One of which is derived from marine brown algae, Laminaria Hyperborea. The brown algae produce alginate, which is reported to chelate with divalent or trivalent cati-ons. Here, we propose a new 3DP systems for manufacturing the powder based structures. The powder, which is generally used, is composed of calcium sulfate hemihydrate which can be transformed to a ‘needle-shape’ when it adsorbs water based binder. Then the powder undergo physical crosslinking and the binders help to make more solid structures. By binding the powder with alginate solution and stacking layer by layer with binders, we demonstrate the sturdy structures are made. Solidification undergo at molecular level with powder and alginate binder solution. The shape of granular powder is converted into needle crystal and met-al coordination is occur between alginate and calcium cation, concurrently. In addition, vacuum treatment steps after stacking the structures improve the mechanical strength similar to existing post-treatment using cover adhesives. The study suggests that biocompatible adhesives and vacuum treatment without toxic cover adhesives can enhance mechanical properties of powder based 3DP structures.