Steering electrodes are located between the spinneret tip and the collector and are found in pairs for better control of the electrospinning jet. Usually stationary, they control the electrospinning jet by varying the voltage applied to them. A direct-current (DC) power supply is normally used to apply a high voltage to the steering electrode and is usually of the same polarity as the voltage applied to initiate electrospinning so as to deflect and control the spinning jet away from the steering electrode. However, an alternating current (AC) high voltage has also been used to introduce high voltage to the steering electrode. Kim et al (2009) used an AC electric field of 2 - 5 kV/cm at 300 Hz to control the electrospinning jet and it has the added advantage of reducing the overall charges on the deposited fibers. Steering electrodes usually come in pairs with a single pair controlling a axis while two pairs enables steering of the electrospinning jet in x - y axes [Bellan and Craighead 2006].They may function like focusing electrode if the voltage applied to all the electrodes are the same or to guide the jet by pairing the voltage applied such that one provides a repulsive force while the other provides a attractive force. Steering electrodes can be very effective in fabricating highly aligned fiber membrane when used in tandem with a rotating collector [Arras et al 2012].
A study was conducted by Nurfaizey A H et al(2014) on the voltage applied on the steering electrodes and its influence on the electrospinning jet. The distance at which the electrospinning jet was deflected and the voltage applied on the steering electrodes has a linear relationship. Applying the same voltage on both steering electrodes causes the deposition area of the fibers to compress from a circular area to a ellipsoidal area with the decreases in aspect ratio of the deposition area varying linearly with increasing voltage. Their study also found that the steering electrodes have the greatest influence on the trajectory of the electrospinning jet when it is near the spinneret tip and progressively weakens towards the collector.
The steering electrode may be used in tandem with the movement of the collector for precise deposition of fibers with the collector moving in one direction and the steering electrode controlling movement of the jet in the perpendicular direction. This is particularly useful when the distance between the spinneret tip and the collector is small such as in the case of near field electrospinning. Karisson et al (2021) demonstrated the precise deposition of near field, melt electrospun polycaprolactone (PCL) with the use of a single steering electrode. With the aid of a feedback control from a CCD camera and programmed voltage applied to the steering electrode, they were able to space fibers at 50 µm and 40 µm apart and maintain the accuracy of the fiber deposition to within a few micrometers.
▼ Reference
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Arras M M L, Grasl C, Bergmeister H, Schima H (2012) Electrospinning of aligned fibers with adjustable orientation using auxiliary electrodes. Sci. Technol. Adv. Mater. 13, 035008.
Open Access
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Bellan L M, Craighead HG. (2006) Control of an electrospinning jet using electric focusing and jet-steering fields. J. Vac. Sci. Technol. B 24 pp. 3176.
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Karlsson A, Bergman H, Johansson S. Active real-time electric field control of the e-jet in near-field electrospinning using an auxiliary electrode. Journal of Micromechanics and Microengineering 2021; 31: 035001
Open Access
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Kim G H, Yoon H, Lee H N, Park G M. Polycarprolactone Ultrafine Fiber Membrane Fabricated Using a Charge-reduced Electrohydrodynamic Process. Macromolecular Research 2009; 17: 533.
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Nurfaizey A H, Stanger J, Tucker N, Buunk N, Wood A R, Staiger M P. Control of Spatial Deposition of Electrospun Fiber Using Electric Field Manipulation. Journal of Engineered Fibers and Fabrics 2014; 9: 155.
Open Access
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