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Direct ink writing (DIW) additive manufacturing is a versatile 3D printing technique for a broad range of materials. DIW can print a variety of materials provided that the ink is well-engineered with appropriate rheological properties. DIW could be an ideal technique in tissue engineering to repair and regenerate deformed or missing organs or tissues, for example, bone and tooth fracture that is a common problem that needs surgeon attention. A critical criterion in tissue engineering is that inserts must be compatible with their surrounding environment. Chemically produced calcium-rich materials are dominant in this application, especially for bone-related applications. These materials may be toxic leading to a rejection by the body that may need secondary surgery to repair. On the other hand, there is an abundance of biowaste building blocks that can be used for grafting with little adverse effect on the body. In this work, we report a bioderived ink made entirely of calcium derived from waste animal bones using a benign process. Calcium nanoparticles are extracted from the bones and the ink prepared by mixing with different biocompatible binders. The ink is used to print scaffolds with controlled porosity that allows better growth of cells. DIW printed parts show better mechanical properties and biocompatibility that are important for the grafting application. Degradation tests and a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay study were done to examine the biocompatibility of the extracted materials. In addition, discrete element modeling and computational fluid dynamics numerical methods are used in Rocky and Ansys software programs. This work shows that biowaste materials if well-engineered can be a never-ending source of raw materials for advanced application in orthopedic grafting.

The search for new hard materials is often challenging, but strongly motivated by the vast application potential such materials hold. Ti3Au exhibits high hardness values (about four times those of pure Ti and most steel alloys), reduced coefficient of friction and wear rates, and biocompatibility, all of which are optimal traits for orthopedic, dental, and prosthetic applications. In addition, the ability of this compound to adhere to ceramic parts can reduce both the weight and the cost of medical components. The fourfold increase in the hardness of Ti3Au compared to other Ti-Au alloys and compounds can be attributed to the elevated valence electron density, the reduced bond length, and the pseudogap formation. Understanding the origin of hardness in this intermetallic compound provides an avenue toward designing superior biocompatible, hard materials.