Aug 25, 2011
Bowl electrospinning scales up nanofibre production
Collections of nanofibres are useful materials for a variety of applications including filtration, biomedical tissue engineering, and energy storage thanks to a combination of high surface-to-volume ratios and large porosity values. The fibrous structures can be assembled using electrospinning, which offers an inexpensive and elegant route to fabricating such materials. However, one factor that inhibits more widespread industrial utilization of electrospun nanofibres is the slow production rate achieved under the commonly used traditional needle electrospinning method.
Many higher throughput systems have been proposed, but recently researchers at NC State University, US, have demonstrated a particularly simple technique that scales up nanofibre production and provides a close connection to the popular benchtop method.
Using three-dimensional modelling of the electric field parameters, the team recognized that the field gradient and amplitude generated by the edge of a metal plate was very similar to the pattern produced by a conducting needle in the traditional method. In other words, the edge of a plate could be used as a source electrode to induce nanofibre formation.
The scientists extended this idea and investigated what happens when the edge surface is curved around on itself to form a bowl, providing a natural polymer fluid reservoir, and reported the results of their study in the journal Nanotechnology.
Using a high-voltage initiation interval, instabilities spontaneously generated on the polymer solution surface radially migrate to the lip of the bowl and form approximately equally spaced circumferential jets, which are directed towards a concentrically placed cylindrical collector.
A reduction in the applied voltage subsequently produces stable jets that exhibit linear and whipping regions similar to the traditional electrospinning system.
This scale-up method generates high-quality polymeric nanofibres with small diameters and a narrow size distribution, but with a dramatically increased production rate versus a single needle approach due to the large number of parallel jets formed.
The technique requires no moving parts as fibres are produced directly from the fluid reservoir, which simplifies the set-up and prevents potential clogging issues that often confront confined feed methods.
The team has demonstrated bowl electrospinning for several different polymer fluid chemistries.
To follow up the study, the researchers are investigating how fundamental fluid properties affect the dynamics of jet formation, the maximum number of possible jets that can be formed, and effects due to jet-to-jet interactions.
Additional information can be found in the journal Nanotechnology.
About the author
This research was performed by a team from the Department of Physics (College of Mathematical and Physical Sciences) and the Textile Engineering, Chemistry, and Science Department (College of Textiles) at NC State University, US. Nagarajan Thoppey Muthuraman is a PhD student in the interdisciplinary Fibre and Polymer Science program, co-advised by Prof. Gorga and Prof. Clarke. Dr Jason Bochinski is an Assistant Research Professor with a wide range of scientific interests, including the generation of ultracold molecules, fundamental quantum optical studies of strongly driven atoms, and novel imaging characterization of electrospinning processes. Prof. Laura Clarke is an Associate Professor in the Department of Physics; her experimental research group explores fabrication, electrical properties, and novel photothermal processing of nanostructured nanocomposites. Prof. Russell Gorga is an Associate Professor in TECS and Program Director of Textile Engineering; his research interest is in developing polymer nanocomposites and nanofibres with improved mechanical and electrical properties for advanced applications. The work was supported by the National Science Foundation under grant CMMI-0800237 and by the Faculty Research and Professional Development Fund at NC State University.