Research on Multinozzle Near-Field Electrospinning Patterned Deposition

Hindawi Publishing Corporation Journal of Nanomaterials Volume 2015, Article ID 529138, 8 pages http://dx.doi.org/10.1155/2015/529138 Research Article Research on Multinozzle Near-Field Electrospinning Patterned Deposition Han Wang, Shenneng Huang, Feng Liang, Peixuan Wu, Minhao Li, Sen Lin, and Xindu Chen Guangdong Provincial Key Laboratory of Micro-Nano Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, China Correspondence should be addressed to Peixuan Wu; and Xindu Chen; Received 18 February 2015; Revised 26 May 2015; Accepted 27 May 2015 Academic Editor: Ilaria Armentano Copyright © 2015 Han Wang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Multinozzle electrospinning systems are designed to increase productivity, while near-field electrospinning (NFES) systems are designed to deposit solid nanofibers in a direct, continuous, and controllable manner. In this paper, several multinozzle NFES setups are tested. The experiment reveals that the deposition distance becomes larger when working distance and needle spacing increase, and the influence of voltage is relatively weaker. The deposition of double nozzle NFES has been studied with Coulomb’s law and theoretical derivation has been verified by the experimental conclusion. The experiment result and theoretical derivation are helpful to get different distance of direct-written fibers by adjusting working distance or needle spacing to change distance of fibers largely and adjusting voltage to change distance slowly. Through these efforts, it is convenient to adjust the distance of straight fibers in multinozzle system. 1. Introduction Nowadays, the microdevices and flexible electronics have been receiving considerable attention. These devices have various applications in communications, biomedicine, and military industries [1]. The development of polymer nanofibers has surfaced because the miniaturized applications necessitate ultralightweight and strong structures [2]. In recent years, electrospinning has been considered as a hopeful technique to generate high strength nanofibers. Although it is easy to get specific structures and control fiber diameters, the whipping in far-field electrospinning system makes some special structures (such as straight fiber) which are hard to obtain by conventional electrospinning techniques [3–6]. It is difficult to control nanofibers deposition accuracy, which is performed by adjusting related processing parameters, such as voltage and solution concentration [7–9]. In NFES system, when the voltage applied on the nozzle is high enough, the Taylor cone will spray fibers; the electrodeto-collector distance, ℎ, is in the range of 500 𝜇m to 3 mm, which can suppress the nanofiber whipping [10]; then the process can be developed to deposit solid nanofibers precisely in a direct, continuous, and controllable manner [11, 12]. Jets from the electrospinning nozzle become more stable and controllable, increasing the accuracy of nanofiber deposition correspondingly [13, 14]. By adjusting electrospinning parameters and materials, chemical etching, lithography, and microassembly, NFES can process micro-nano-devices without excessive labor and environment pollution [15– 17]. NFES nanofibers have different morphology parameters and physical and chemical properties. This solves a key problem in microstructure manufacturing: how to put nanofibers into the correct and precise position. Compared to conventional methods, such as chemical etching, lithography, and microassembly, NFES can process micro-nanodevices without excessive labor and environment pollution [15–17]. However, the single nozzle NFES is difficult to reduce production cost and improve product efficiency. Multinozzle electrospinning is proposed as an efficient way to increase production rate, and the method has been used in volume manufacturing, such as air filter, clothing fabrics, fireproof materials, and medical gauze [18–20]. But unordered collections of nanofibers remain a problem resulting in difficulty 2 of manufacturing multi-line structures. Therefore, it is a real problem to utilize NFES technique for manufacturing microdevices on a large scale [21–24]. This paper provides a multinozzle NFES technique and the method can improve manufacturing efficiency and guarantee manufacturing consistency. Moreover, the effect of various electrospinning parameters is observed and analyzed in multinozzle NFES deposition process. The parameters included working distance, needle spacing, and voltage. The experiment result reveals that the deposition distance becomes larger when working distance and needle spacing increase, and the influence of voltage is particularly weak. This paper also discusses the theoretical reasons of these phenomena and discovery of the main causes of interference, which are electric field force and Coulomb force. The conclusion can help to adjust the deposition of straight fibers by changing experiment parameters in multinozzle system. And it is hopeful to adjust the distance of straight fibers in multinozzle system conveniently. 2. Materials and Methods 2.1. Materials. The solutions used in electrospinning experiments were prepared using polymer ethylene oxide (PEO, Aladdin, Shanghai, China, 𝑀 = 2 × 106 g/mol). This material was dissolved in distilled water to make solutions with several concentrations under stirring for 4 hours at room temperature (20∘ C) to make solutions with concentrations of 5 wt%. The fibers are collected in a constant condition (temperature: 20∘ C–30∘ C, relative humidity: 50%–70%). As shown in Figure 1, the morphology of the electrospun fiber is observed by means of scanning electron microscopy (SEM). The observation is performed using a HITACHIMT3030 (Hitachi desktop SEM TM3030). 2.2. Experiment System. Experiment system is shown in Figure 2. Controlled deposition equipment of multinozzle near-field electrospinning has been built with an 𝑋-𝑌 motion platform, and the nozzle arrangement is mounted on the sliding block of 𝑧-axis linear guide. Various near-field electrospinning models can be adjusted by a motion controller, which includes the working distance, collector speed, and locus. Programmable power supports control the high voltage DC (direct current) power supply to maintain electrospinning, so that the work voltage parameter can be adjusted at any time. A syringe pump was utilized to control flow rate of PEO solution. CCD (charge coupled device) microscope is used for observing multinozzle near-field electrospinning process, which will be displayed on a PC (personal computer). Special nozzles, where the needles spacing can be changed, constitute the arrangements according to certain shapes, which are shown in Figure 3. Arrangement jets will deposit on the collec (...truncated)