Self-organisation of multiple jets in near-field electrospinning process

A dispersion law analysis and the critical value of applied electric field intensity/field strength formulations are employed to investigate the self-organised behaviour of multiple jets in near-field electrospinning (NFES) experiments. In particular, the theoretical 'fastest forming instability' in mesocopic scale was also found to play a crucial role in selecting a specific characteristic wavelength under the NFES setup. The onset of electrospinning from a free liquid surface is experimentally observed from the porous material sandwiched by two flat copper electrodes and electrified 8 wt polyethylene oxide polymeric solution. Predicting critical values of the critical field strength and corresponding critical interjet distance, that is, the maximal distance between the neighbouring jets, are also deduced and validated to be simply depending on the capillary length. Subsequently, a modified theory based on the addition of hydrostatic, capillary and electric pressures is proposed to compensate the deviation of the NFES experiment and the theory of conventional electrospinning from a free liquid surface. The extra capillary pressure term is curve-fitted and found to be effective to reduce the deviation in the interjet distance range of 3-5 mm, which falls into the regime of NFES at the similar length scale of electrode-to-collector distance.