A novel direct aerodynamically assisted threading methodology for generating biologically viable microthreads encapsulating living primary cells

In a recent discovery, coaxial electrospinning was explored to encapsulate living organisms within a continuous bio‐polymeric microthread from which active biological scaffolds were fabricated (Townsend‐Nicholson and Jayasinghe, Biomacromolecules 2006, 7, 3364). The cells were demonstrated to have gone through all expected cellular activity without their viability being compromised. These biologically active threads and scaffolds have direct and tremendous applicability from regenerative to therapeutic medicine. Currently these post‐processed cells as composite threads and scaffolds are being investigated in‐depth at a cellular level to establish if the processing methodology has any affect on the cellular make‐up. We now demonstrate a competing non‐electric field driven approach for fabricating composite threads and scaffolds influenced only by a differential pressure. We refer to this novel composite thread to scaffold fabrication methodology as coaxial aerodynamically assisted bio‐threading (CAABT). Our investigations firstly, demonstrate that this technique can process handle living organisms without biologically perturbing them in anyway. Secondly the process is elucidated as possessing the ability to form composite active threads from which biologically viable scaffolds are formed. Finally our study employs florescent activated cell sorting (FACScan), a method by which the cellular dynamics and viability are quantified on control and threaded cellular samples at two prescribed time points. In parallel with FACScan, optical comparison of cellular morphology at three time points within a period of three weeks is carried out to photographically observe any changes in the post‐processed cellular phenotype. Our developmental investigations into this novel aerodynamically assisted threading methodology has unearthed a unique biomicrofabrication approach, which joins cell electrospinning in the cell threading to scaffold fabrication endeavor. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Solidification Behavior of Intensively Sheared Hypoeutectic Al-Si Alloy Liquid

The effect of the processing temperature on the microstructural and mechanical properties of Al-Si (hypoeutectic) alloy solidified from intensively sheared liquid metal has been investigated systematically. Intensive shearing gives a significant refinement in grain size and intermetallic particle size. It also is observed that the morphology of intermetallics, defect bands, and microscopic defects in high-pressure die cast components are affected by intensive shearing the liquid metal. We attempt to discuss the possible mechanism for these effects.     

Versatile methodology for generating size-controlled composite micrometer beads capsulating nanomaterials

Our developmental investigations into aerodynamically assisted jetting have previously shown great promise (Jayasinghe and Suter in Micro and Nano Letts., 2006, 1, 35) in materials science and engineering. This processing approach is currently undergoing rapid development where it will join other related jet-based processes such as ink-jet printing and electrospraying with which the precision deposition of droplet residues (containing a wide variety of micro-and nanomaterials) is most useful in micro-and nanosciences. The ability for capsulating nanomaterials (having a mean particulate size of 5 nm) as micrometer-sized composite beads is demonstrated. Investigations reported here show the influence of the applied aerodynamic forces to the chamber or flow rate to the needle, respectively, having effect on the generated composite bead sizes, their distributions and on the jetting characteristics. These investigations imply the versatility of this processing science for capsulating a wide variety of nano-sized materials as composite beads for applications ranging from the formation of stable emulsions to a route for controlled delivery of drugs, which would be most useful to the pharmaceutical industry.     

A versatile pressure assisted jet-fabrication by coating approach for forming biocompatible constructs for tissue engineering

In the current work we elucidate the emergence of a versatile jetting methodology, which is completely determined by an applied pressure. The applied pressure draws out the flowing polymer to generate droplets, which are later used for coating a template resulting in the fabrication of a structure. Our investigations demonstrate the ability to generate a wide range of two- and three-dimensional architectures by the coupling of this processing approach together with a polymer (in this study polycaprolactone is used). These investigations illustrate the versatility of this pressure assisted processing route for the fabrication of structures by way of templated coating.     

Enhanced heterogeneous nucleation in AZ91D alloy by intensive melt shearing

Intensive melt shearing was applied to the commercial AZ91D alloy melt to investigate its effects on grain refinement. Alloy melts with and without melt shearing were also filtered using a pressurized filtration technique to concentrate the potential nucleating particles for electron microscopic examination. The results showed that intensive melt shearing resulted in significant refinement of both the Al₈Mn₅ intermetallics and the primary α-Mg phase in the as-cast AZ91D alloy, and that this grain-refining effect is insensitive to the superheat and can persist even after prolonged isothermal holding. The pressurized filtration experiments showed for the first time that oxide films and skins consist of nano-sized MgO particles populated densely in a liquid matrix. Intensive melt shearing can effectively disperse such MgO particles throughout the alloy melt. The HRTEM investigation and detailed crystallographic analysis confirmed that dispersed MgO particles act as potent heterogeneous nucleation sites for both the Al₈Mn₅ and α-Mg phase.