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Cartilage as a tissue in the body possesses a low regenerative capacity and is extremely difficult to repair. Today, treatment of cartilage injury, degeneration and defects presents critical clinical challenges, yet none of the currently available cartilage treatments provides a perfect solution. Since natural cartilage extracellular matrix is a nanoscaled structure, the main objective of this study is to design a novel biomimetic nanostructured cartilage construct via electrospinning and carbon nanomaterials for enhancing human bone marrow mesenchymal stem cell chondrogenic differentiation. For this purpose, we synthesized a carbon nanomaterial mixture, using a plasma arc discharge method, consisting of graphene nanoplatelets and single walled carbon nanotubes. This nanomaterial was then incorporated into electrospun polycaprolactone (PCL) microfibrous scaffolds, with and without an additional poly-L-lysine surface coating. Scaffolds were thoroughly characterized for both their biomimetic features and biocompatibility. Our results showed that our scaffolds with carbon nanomaterial have greatly improved mechanical properties and enhanced stem cell adhesion, proliferation and chondrogenic differentiation than PCL controls without carbon nanomaterials, and thus hold promise for improving cartilage formation in future in vivo studies and clinical applications.

Arc discharge is one of the most efficient and environmental friendly method to synthesize Single Wall Carbon Nanotube (SWCNT). However, due to the ultra-fast synthesis procedure, localization of the SWCNT synthesis in an arc discharge plasma volume in situ has been a long standing problem. This relates to the ability of controlling volumetric synthesis of nanostructures in plasmas in general. In order to better understand the mechanism of the nanotube growth in plasma, we have developed an actuator driven high-speed system that is able to extract material from the arc plasma volume during the synthesis procedure. The majority of the SWCNTs produced using arc discharge method are semiconducting with diameter of about 1.5nm. It is shown that the growth region of SWCNTs is between 3mm to 11mm away from the center of the arc

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The breakdown mechanism in the Micro-Cathode Arc Thruster has been studied to better understand the nature of the discharge ignition and to extend the ignition system lifetime. It has been found that optimal material selection of the insulator is an important factor during breakdown. Two opposite processes have been found to cycle during operation. The processes are degradation of the conductive film from the inter-electrode interface and re-deposition of the conductive film due to cathode spot erosion. Initial resistances were found to vary from hundreds of ohms to thousands of ohms based on the initial connectivity of the film to the electrodes. After initial breakdown however, resistances have been found to stabilize in a typical pattern. Materials capable of withstanding high temperatures, high pressures, and smooth surfaces are shown to be beneficial for extending thruster lifetime.