RESEARCH ARTICLE Copyright © 2010 American Scientiﬁc Publishers All rights reserved Printed in the United States of America Journal of Nanoscience and Nanotechnology Vol. 10, 1–6, 2010 High Throughput Tip-Less Electrospinning via a Circular Cylindrical Electrode Dezhi Wu 1 , Xiaoping Huang 1 , Xiting Lai 1 , Daoheng Sun 1 ∗ , and Liwei Lin 2 ∗ 1 Department of Mechanical and Electrical Engineering, Xiamen University, Xiamen 361005, P. R. China 2 Department of Mechanical Engineering, Berkeley Sensor & Actuator Center, University of California, Berkeley, California 94720, USA High throughput production of nanoﬁbers by means of “Tip-less Electrospinning” (TLES) has been demonstrated using a circular cylinder as the emitting electrode. Electrohydrodynamics instabilities on a thin liquid ﬁlm under high electrical ﬁeld can generate artiﬁcial liquid jets for the TLES process. Experimental results have shown that the yield of poly(ethylene oxide) nanoﬁbers can be more than 260 times in weight as compared with a single-jet electrospinning process. Parameters affecting the TLES process including applied voltage, polymer solution concentration, electrode-to-substrate distance and the thickness of liquid ﬁlms have been characterized. As such, TLES has potential for high-throughput, massive production of electrospun nanoﬁbers. Keywords: Electrohydrodynamics, Nanoﬁber, Polymer, Tip-Less Electrospinning. 1. INTRODUCTION The superior characteristics of nanoﬁbers such as high surface area to volume ratio and speciﬁc properties (opti- cal, mechanical, electrical and chemical) have led to sev- eral promising applications, including ﬁltration, 1 scaffolds for tissue engineering, 2 wound dressing and protective clothing, 3 reinforced composite materials, 4 and micro/nano sensors and actuators. 5 The ability to fabricate nanoﬁbers from a broad range of polymeric materials with controlla- bility has greatly accelerated in recent years with advance- ment in electrospinning processes, such as aligned arrays and orderly patterns. 6–9 However, high production speed of electrospun nanoﬁbers has been a key technology chal- lenge. Previously, multiple-jet setup has been the main approach to speed up the manufacturing processes. For example, three different arrangements of multi-electrode array (line-shape, elliptical and concentric mode) have been studied and it was concluded that concentric electro- spinning setup has provided the best efﬁciency and qual- ity of electrospun nanoﬁbers. 10 The inﬂuence of different applied voltages on electrodes has also been investigated. It was found that ﬁber quality decreased under higher applied bias voltages as the electric ﬁelds from individual electrode interfered with each other. 11 In another approach, a cylindrical, shell-shape electrode was introduced with the ∗ Authors to whom correspondence should be addressed. setup of multiple electrodes to stabilize the electrospinning process with better uniformity. 12 In the tip-less electrospinning demonstrations, there have been two recent reports. First, ferromagnetic ﬂuid was used under a magnetic ﬁeld with the addition of an electrical ﬁeld. This setup generates steady vertical spikes and results in upward jetting of nanoﬁbers. 13 Second, a porous tube was used with random holes of 10–100 m in diameters. It was shown to generate numerous jets under high applied voltages and suitable air pressure to supply liquid polymer through the pores. 14 Nanoﬁbers were deposited on the inner surface of a cylindrical collector that enclosed the porous cylindrical tube. This paper presents results in a tip-less electrospinning setup using a circular cylindrical surface as the electrode. In contrast to the previously published reports, there are no needle arrays, no ferromagnetic liquid layer and no porous tube in this setup. The mechanism is based on electrohydrodynamics (EHD) induced ﬂuctuations on top of relatively smooth surface to create artiﬁcial liquid jets for electrospinning. Furthermore, unlike conventional tip- based electrospinning processes, the common problem of clogging on the syringe tip is eliminated. 2. EXPERIMENTAL DETAILS The setup of the high throughput tip-less electrospin- ning consists of four components as illustrated in J. Nanosci. Nanotechnol. 2010, Vol. 10, No. xx 1533-4880/2010/10/001/006 doi:10.1166/jnn.2010.2194 1