Biomedical Composites

Overview  Definition- made up of bulk phase (matrix) and dispersed other phases (reinforcement); collectively, the 2 exhibit mechanical properties different from any one component alone  Anisotropic (directional) or isotropic (nondirectional)  Relatively new field  Composite research- 1960s forward  Biomedical applications  Dental and orthopedic implants Image from

Naturally Occurring Composites  Wood  Cellulose fibers in lignin matrix  Bone  Collagen fibers in apatite matrix  Palm fronds, fish scales, etc Image from

Matrices  Thermosets  High stiffness, temperature resistance  Typically non-degradable  Thermoplastics  Flexible, tough, nonreactive  Can be degradable or not  Inorganics  Metals, ceramics, etc.  Resorbable Polymers  Degrade with time  Can be used to promote tissue integration

Reinforcements  Fibers  Long fibers  Can provide anisotropic or isotropic properties, depending on orientation  Short fibers  Anisotropic properties harder to achieve; easier processing  Particles  Isotropic; can be easily processed (ex. casting)

Processing MEDICAL/NEW/HANBOOK/12_Biomedical_composites.pdf

Biological Considerations  Infection  Rough surfaces provide bacterial attachment sites  If surface is porous, pore size must be considered  Sterilization  How to sterilize implant?  Radiation, UV light, etc  Immunogenicity  Will the implant elicit an immune response?

Challenge- Designing Biomedical Composites  Groups of 3  You will be given a type of implant to design a composite material for  Ex. Artificial knee  You may choose materials from the handout, but you are not limited to them  15 minutes to design composite  2 minutes to pitch your idea to the class and defend your material choice