A design for the additive manufacture of functionally graded porous structures with tailored mechanical properties for biomedical applications

CAD/CAM-based layered manufacturing and additive manufacturing techniques of metals have found applications in near-net-shape fabrication of complex shaped parts with tailored mechanical properties for several applications. Especially with the onset of newer processes such as electron beam melting (EBM) and direct metal laser sintering (DMLS), revolutionary advances may be achieved in material substitution in the medical implant industry. These processes must be suitably developed and tested for the production of medical grade substitutions. In this article, we discuss a design process for creating periodic cellular structures specifically targeted for biomedical applications. Electron beam melting is used to fabricate the parts. Evaluation of the mechanical properties is performed and compared with design parameters. Compression tests of the samples show effective stiffness values ranging from 0.57 (±0.05) to 2.92 (±0.17) GPa and compressive strength values of 7.28 (±0.93) to 163.02 (±11.98) MPa. Substituting these values for simulation of biomechanical performance of patient-specific implants illustrates the compatibility and matched functional performance characteristics of highly porous parts at a safety factor of 5 and an effective reduction in weight. These developments are unique for the construction of maxillofacial and craniofacial implants. The novel design strategy also lends itself very well to metal additive manufacturing technologies. Implants designed and fabricated with this design strategy and manufacturing process would have mechanical properties equivalent to the part they replace and restore better function and esthetics as against the currently used methods of reconstruction. Suitable examples of a titanium porous cranioplasty plate and a sandwich structure are illustrated.     

Multi-drug resistance,integron and transposon-mediated gene transfer in heterotrophic bacteria from Penaeus vannamei and its culture environment

Environmental Science and Pollution Research - Multi-drug resistance (MDR) in bacteria is regarded as an emerging pollutant in different food production avenues including aquaculture. One hundred...