The objective of this award is to explore new composite nano-manufacturing methods to enhance mechanical integrity of biopolymers and to investigate a new micro porous structure which will assist in bioactive material delivery in surgical devices. The approach will be: 1. Conduct biomaterials and nano-diamond (ND) composite research to optimize the polymer/ND interface and mass production technique to manufacture ND reinforced biopolymers. 2. Identify suitable structural and bioactive materials for a strong fixation device body and efficient bone/tissue healing and growth. 3. Research on a new technique: gradient cellular structure to generate bio-reagent storage and passage micro pores to not only assure the device mechanical strength but also assist in bioactive materials delivery. 4. Conduct various mechanical and biological testing to find, control, optimize and integrate all required functionalities for the surgical device.
The benefits and broader impacts of this research will be: Provide an innovative way to increase the mechanical integrity of biomaterials and replace current passive orthopedic surgery devices with active devices; a strong relationship with Arthrex, Inc. will be built for the new technology development and transfer; three doctoral students and two senior design teams will be trained; engaging students with design projects in nanomanufacturing, bioactive fixation devices and bio-reagents delivery. The project will be used in outreach workshops for local high school and community college students, including many underrepresented minority students to showcase high-tech nanomanufacturing and surgical engineering applications.
Biopolymers have a great potential in biomedical engineering, having been used as scaffolds for hard and soft tissues, such as bone and blood vessels for many years. More recently, biopolymers have also found applications in surgical fixation devices. Compared with conventional metal fixation devices, bone grafts and organ substitutes, biopolymer products have advantages of no long-term implant palpability or temperature sensitivity, predictable degradation to provide progressive bone loading and no stress shielding, all of which leads to better bone healing, reduced patient trauma and cost, elimination of second surgery for implant removal, and fewer complications from infections. However there are two challenges which impede more widespread applications of biopolymers in orthopedic surgery: 1. Mechanically, currently used biopolymers are not strong enough especially when used as surgical fixation devices and bone scaffolds. 2. Current surgical fixation devices, bone scaffolds etc. do not actively promote bone healing and re-growth, subsequently leaving voids in the tissue once the implanted device is pulled out (metal device) or fully degraded (biopolymer device). The main objective of this GOALI, collaborative project led by Drexel University, Georgia Tech and Arthrex, Inc., was to explore new composite nano-manufacturing methods to enhance mechanical integrity of biopolymers and to design a new micro structure which assists in bioactive material delivery. The main research tasks conducted at Georgia Tech were to develop processing techniques for dispersing nanodiamond (ND) particles into biodegradable polymers and fabrication of microporous biocomposites. By incorporating ND into microporous medical implanting materials, improved mechanical properties and enhanced bioactivity can be achieved. The results obtained by Georgia Tech include (1) By selective functionalization, dispersion of nanodiamond in biopolymers can be greatly improved. If melt processing is used, dispersion can also be enhanced by elongational flow based mixing. (2) Nanoindentation tests showed that nanodiamond reinforced PLLA biocomposites exhibit improved mechanical properties, particularly on modulus and hardness. (3) With PS as a sacrificial polymer, nanodiamond enhanced microporous PLLA biocomposites were successfully produced. The experimental results showed that nanodiamond can be an effective compatibilizer for increasing the miscibility between PS and PLLA and reducing the phase size. It was further found that the post annealing conditions significantly affect the distribution of ND particles in the blend and finally in the porous PLA structure. This project, for the first time, investigated a manufacturing process for micorporous biopolymers with functionalized nanodiamond as reinforcement. Besides the novel manufacturing process developed, fundamental contributions were made regarding kinetic and dynamic control of the phase structure of immiscible polymer blends for creation of a structured porous media. Specifically, the research helped advance understanding of (a) role of nanodiamond in reinforced biocomposites, (b) evolution of phase structures of immiscible polymer blends under nonisothermal and dynamic conditions, (c) activity of nanodiamond particles during blend processing, and (d) unique physical and mechanical properties of nanodiamond reinforced microporous biocomposites.
