The Origin and Effect of Space Charges in Electrospinning Rashi Grewal, Mike Jaffe, John Federici, Bryan Pfister and George Collins Department of Biomedical Engineering New Jersey Institute of Technology Newark, NJ 07102 I.Introduction This work involves the study of the origin and effect of space charges in the electrospinning process. Electrospinning is a process used to make solid, nanofibrous polymer mats. These mats are used in tissue engineering as scaffolds for cells. The origin and effect of space charges in this process has not been well-studied. II.Experimental A polymer solution is loaded into a plastic syringe capped by a needle. The lead of a wire from a high DC voltage supply is connected to the needle, from where the solution will flow out. The opposing lead is connected to a metal plate. A syringe pump hydraulic system creates pressure to push the solution out from its syringe. The polymer solution is drawn out of the syringe by the electric field created by the high voltage, and forms a Taylor cone at the tip of the needle. This Taylor cone is then elongated into fibers that travel towards the metal plate, where they are then collected. These fibers complete the circuit. The presence of residual charges was detected using thermally stimulated current (TSC). Novel results were obtained using a highly sensitive electrometer to measure current between the needle and grounded plate under different conditions. Fig. 1. Electrospinning Setup III.Initial Results and Discussion Electrospinning is possible because the charges that are injected into the polymer solution electrostatically drive the ejected fluid stream from the needle to the grounded plate. The focus here is on the fate of the charges in the resulting fibrous mat. It has been previously shown that residual charges can be detected in electrospun mats. These are space charges trapped within the internal structure of the solid. It was assumed that the singular origin of these charges was injection into the solution as it exited the metal needle. Space charges collect at irregularities such as defects or grain boundaries, and on the surface at the dielectric-electrode interface [1-3]. It is possible to remove space charges from their locations within the polymer. The decay, or release, of space charges occurs through either neutralization with atmospheric charges or dissipation from the surface or bulk of the material. There are various techniques to dissipate space charges: UV irradiation, and water or alcohol soaking. In the case of UV irradiation, the polymer sample is exposed to UV radiation source. The energy of the photons is greater than that of the space charges, which excites the charges and causes them to become detrapped, or mobile, from their locations and released into the air. The presence of space charges has also been observed to be greatly reduced when a polymer is soaked in water or alcohol. The actual mechanism behind which this works has yet to be understood. [4- 6]. The role of space charges in electrospun scaffolds has not been studied. Preliminary results in Table I indicate that the total charge of a mat treated to dissipate charge was less than a freshly electrospun untreated mat. One aim of this study is to examine the effect of space charges on protein adsorption by comparing freshly electrospun mats treated to dissipate the charge.