- Nano Express
- Open Access
Electrospun Aligned Fibrous Arrays and Twisted Ropes: Fabrication, Mechanical and Electrical Properties, and Application in Strain Sensors
- Jie Zheng†1,
- Xu Yan†1,
- Meng-Meng Li†1, 2,
- Gui-Feng Yu1,
- Hong-Di Zhang1,
- Wojciech Pisula2,
- Xiao-Xiao He1,
- Jean-Luc Duvail3 and
- Yun-Ze Long1Email author
© Zheng et al. 2015
- Received: 23 October 2015
- Accepted: 1 December 2015
- Published: 9 December 2015
Electrospinning (e-spinning) is a versatile technique to fabricate ultrathin fibers from a rich variety of functional materials. In this paper, a modified e-spinning setup with two-frame collector is proposed for the fabrication of highly aligned arrays of polystyrene (PS) and polyvinylidene fluoride (PVDF) nanofibers, as well as PVDF/carbon nanotube (PVDF/CNT) composite fibers. Especially, it is capable of producing fibrous arrays with excellent orientation over a large area (more than 14 cm × 12 cm). The as-spun fibers are suspended and can be easily transferred to other rigid or flexible substrates. Based on the aligned fibrous arrays, twisted long ropes are also prepared. Compared with the aligned arrays, twisted PVDF/CNT fiber ropes show enhanced mechanical and electrical properties and have potential application in microscale strain sensors.
- Aligned arrays
- Twisted ropes
- Electrical properties
- Strain sensors
Electrospinning (e-spinning) is a simple and versatile technique to fabricate fibers with diameters typically ranging from a few micrometers down to 10 nm or less. In a traditional e-spinning process, a charged jet is ejected from a Taylor cone and rushes onto the grounded collector under the driving force of an electric field. After solvent evaporation, solid fibers with uniform diameter are randomly deposited on the collector [1–5]. In the past decade, numerous ultrathin fibers originated from polymer, metal, ceramic, and glass have been prepared by e-spinning, and their potential applications in optoelectronics, sensors, catalysis, textiles, filters, fiber reinforcement, tissue engineering, drug delivery, and wound healing have also been extensively explored [1, 6–9].
Normally, the products fabricated by traditional e-spinning are randomly oriented fibers known as a nonwoven mat. In order to extend the potential applications of e-spinning, a lot of modified e-spinning techniques have been proposed to obtain fibers with desired morphologies such as aligned fibrous arrays and twisted ropes. For example, aligned fibers can be prepared by introducing a gap into the conventional collector , adding an auxiliary electric or magnetic field , double spinning,  near-field e-spinning [13–18], and rotating collector . Twisted fiber bundles have also been fabricated by a few means such as dual collection rings , AC e-spinning , a modified setup with two collectors , or with an alternating electric field . The twisted nanofiber rope is promising in the applications of artificial muscle, electron devices, and suture materials . Nevertheless, there are few methods by which both well-aligned fibers and twisted ropes can be fabricated.
So far, the applications of electrospun fibers have been paid much attention due to their unique physical, chemical, and even biological properties, especially in the field of electrical sensors. For instance, piezoelectric materials such as ZnO and polyvinylidene fluoride (PVDF) have been electrospun into aligned fibers and then integrated into a nanogenerator. If this device is pressed or bended by a strain, the current will be induced, resulting from the piezoelectric properties of the functional fibers [24, 25]. Lotus et al. modified the traditional e-spinning setup by introducing a rotating and a stationary collector , and obtained semiconducting twisted ZnO/NiO composite yarns, exhibiting a rectifying behavior of a p-n junction . In addition, twisted microropes of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)-polyvinyl pyrrolidone (PEDOT:PSS-PVP) fibers doped with ionic liquid showed a linear correlation of electrical conductivity with a strain up to 35 % and a repeatable cycle loop of tensile-resilience .
Moreover, efforts have been done to study a nanocomposite made of PVDF and carbon nanotube (CNT) and the interfacial interactions between the two components [29–31]. For example, the difference of the Raman spectra of CNT and CNT dispersed in the PVDF was ascribed to the interfacial interaction between the fluorine of PVDF and the CNTs . The interfacial interaction between the single-walled carbon nanotube (SWCNT) and PVDF and the extensional force experienced by the nanofibers in the e-spinning and collection processes could work synergistically to induce highly oriented β-form crystallites of PVDF extensively . Although the morphological and structural properties and polymorphic behaviors as well as interfacial interactions between PVDF and embedded CNT have been studied, the electrical and mechanical properties of electrospun PVDF/CNT fibers have not been reported intensively.
In this letter, we report on a novel e-spinning device with a set of a modified frame collector, by which highly ordered arrays of polystyrene (PS) and PVDF nanofibers, as well as PVDF/multiwall CNT (MWCNT) composite nanofibers, can be fabricated. It is worthy to note that the spun fibrous arrays show excellent orientation over a large area (more than 14 × 12 cm2). Moreover, twisted ropes can be also prepared successfully with ~10 cm in length by the same technique. The twisted PVDF/CNT composite ropes exhibit improved mechanical performance and conductivity compared with aligned fibrous arrays. In addition, an electrical device has been integrated with high-strain sensitivity based on the twisted rope, indicating good potential in the high-strain sensor.
Preparation of Spun Solution and Electrospinning
Polystyrene (PS) solution was prepared by dissolving 2.0 g PS (average molecular weight of 250,000, ACROS) in 8.0 g tetrahydrofuran (THF). After being stirred for 4 h at room temperature, the PS solution was kept at room temperature for 0.5 h before e-spinning. The PVDF solution was prepared by a similar way by dissolving 1.25 g PVDF (average molecular weight of 275,000, Aldrich) in the mixture of 2.5 g acetone and 2.5 g dimethylformamide (DMF) with 2 h stirring at 60 °C. CNT precursor solution was prepared by dissolving 1.2 g CNTs (Chengdu Organic Chemical Co., LTD) in the mixture of 16.8 g acetone and 2.0 g CNT dispersion (TNWIDS, Chengdu Organic Chemical Co., LTD). PVDF/CNT solution was prepared by dissolving CNT precursor solution and PVDF in the mixture of acetone and DMF (the weight ratio is 1:1). Here, the contents of the CNTs in the final fibers were 8.0, 12.4, and 16.7 wt%, respectively. The PVDF/CNT solution was stirred for 4 h in a water bath at 60 °C before e-spinning.
A high-voltage DC power supply (Tianjin Dongwen, China) was employed to generate voltages. The spun solution was loaded into a 5.0-ml syringe with a stainless spinneret (inner diameter 0.72 mm) which is connected with the anode of the power supply. The applied spinning voltage was 20 kV, and the vertical distance (work distance) between the spinneret and the top of the grounded frame was 8 cm, while the inner frame was placed horizontally at the beginning. The feed rate (e.g., 0.5 ml min−1) could be controlled by a syringe pump. During the electrospinning (ES) process, the rotating speed of the outer frame was set to 600 rpm. All experiments were carried out at room temperature.
A digital camera, an optical microscope (SMZ-168), and a scanning electron microscope (SEM; JEOL JSM-6390) were used to observe morphologies of the ES fibers. All samples are coated with an evaporated gold thin film before SEM imaging to ensure higher conductivity. The PVDF/CNT fibers were characterized by a transmission electron microscope (TEM; HITACHI H-9000), and Fourier transform infrared spectroscopy (FTIR) using a Thermo Scientific Nicolet iN10 spectrometer and absorbance data were processed for the wave number range 700–1000 cm−1. A mechanical test system (Agilent T150 UTM) and a set of an electrical measurement system (Keithley 6220 and Vitech triple output DC power supply) were used to measure the mechanical and electrical properties of the fiber bundles and ropes, separately.
Fabrication of Aligned Fibrous Arrays and Twisted Ropes
Influence of the ES Parameters on the Morphology of Aligned Fibrous Arrays and Twisted Ropes
Fabrication of PVDF/CNT Twisted Ropes
Mechanical and Electrical Properties of Aligned PVDF/CNT Bundles and Twisted Ropes
Strain Sensors Based on Twisted Ropes
In summary, a modified e-spinning setup with two-frame collector is introduced for fabrication of highly ordered arrays within an area up to 14 × 10 cm2. Based on the aligned arrays, twisted continuous ropes can be prepared. The results show that both the position of the inner frame and the rotation speed have significant influence on the morphologies of resultant twisted ropes. On the other hand, the mechanical properties of PVDF/CNT composite twisted ropes are improved by one order of magnitude, indicating their potential in many applications, such as artificial muscle and electronic devices. In addition, the strain-sensitive property of these composite twisted ropes indicates their potential use in strain sensors.
This work was supported by the National Natural Science Foundation of China (51373082); the Taishan Scholars Program of Shandong Province, China (ts20120528); the National Key Basic Research Development Program of China (973 special preliminary study plan, 2012CB722705); the Program for Scientific Research Innovation Team in Colleges and Universities of Shandong Province; and the Postdoctoral Scientific Research Foundation of Qingdao.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
- Huang ZM, Zhang YZ, Kotaki M, Ramakrishna S (2003) A review on polymer nanofibers by electrospinning and their applications in nanocomposites. Compos Sci Technol 63(15):2223–2253View ArticleGoogle Scholar
- Li MM, Yang DY, Long YZ, Ma HW (2010) Arranging junctions for nanofibers. Nanoscale 2:218–221View ArticleGoogle Scholar
- Li MM, Long YZ, Tan JS, Yin HX, Sui WM, Zhang ZM (2010) Dielectric properties of electrospun titanium compound/polymer composite nanofibres. Chin Phys B 19(2):028102/1–6View ArticleGoogle Scholar
- Long YZ, Yu M, Sun B, Gu CZ, Fan ZY (2012) Recent advances in large-scale assembly of semiconducting inorganic nanowires and nanofibers for electronics, sensors and photovoltaics. Chem Soc Rev 41(12):4560–4580View ArticleGoogle Scholar
- Tan JS, Long YZ, Li MM (2008) Preparation of aligned polymer micro/nanofibres by electrospinning. Chin Phys Lett 25(8):3067–3070View ArticleGoogle Scholar
- Greiner A, Wendorff JH (2008) Functional self-assembled nanofibers by electrospinning. Adv Polym Sci 219:107–171Google Scholar
- Reneker DH, Yarin AL (2008) Electrospinning jets and polymer nanofibers. Polymer 49(10):2387–2425View ArticleGoogle Scholar
- Schiffman JD, Schauer CL (2008) A review: electrospinning of biopolymer nanofibers and their applications. Polymer Rev 48(2):317–352View ArticleGoogle Scholar
- Agarwal S, Wendorff JH, Greiner A (2008) Use of electrospinning technique for biomedical applications. Polymer 49(26):5603–5621View ArticleGoogle Scholar
- Sundaray B, Subramanian V, Natarajan TS, Xiang RZ, Chang CC, Fann WS (2004) Electrospinning of continuous aligned polymer fibers. Appl Phys Lett 84(7):1222–1224View ArticleGoogle Scholar
- Gu BK, Sohn K, Kim SJ, Kim SI (2007) Fabrications of nanofibers as crossed arrays by electrospinning. J Nanosci Nanotechnol 7(11):4202–4205View ArticleGoogle Scholar
- Li MM, Long YZ, Yang DY, Sun JS, Yin HX, Zhao ZL, Kong WH, Jiang XY, Fan ZY (2011) Fabrication of one dimensional superfine polymer fibers by double-spinning. J Mater Chem 21:13159–13162View ArticleGoogle Scholar
- Sun DH, Chang C, Li S, Lin LW (2006) Near-field electrospinning. Nano Lett 6(4):839–842View ArticleGoogle Scholar
- Chang C, Limkrailassiri K, Lin LW (2008) Continuous near-field electrospinning for large area deposition of orderly nanofiber patterns. Appl Phys Lett 93:123111/1–3Google Scholar
- Rinaldi M, Ruggieri F, Lozzi L, Santucci S (2009) Well-aligned TiO2 nanofibers grown by near-field-electrospinning. J Vac Sci Technol B 27(4):1829–1833View ArticleGoogle Scholar
- Zheng GF, Li WW, Wang X, Wu DZ, Sun DH, Lin LW (2010) Precision deposition of a nanofibre by near-field electrospinning. J Phys D Appl Phys 43:415501/1–6View ArticleGoogle Scholar
- Pu J, Yan XJ, Jiang YD, Chang C, Lin LW (2010) Piezoelectric actuation of direct-write electrospun fibers. Sensors Actuators A 164:131–136View ArticleGoogle Scholar
- Chang C, Tran VH, Wang JB, Fuh YK, Lin LW (2010) Direct-write piezoelectric polymeric nanogenerator with high energy conversion efficiency. Nano Lett 10:726–731View ArticleGoogle Scholar
- Katta P, Alessandro M, Ramsier RD, Chase GG (2004) Continuous electrospinning of aligned polymer nanofibers onto a wire drum collector. Nano Lett 4(11):2215–18View ArticleGoogle Scholar
- Dalton PD, Klee D, Moller M (2008) Electrospinning with dual collection rings. Polymer 46:611–614View ArticleGoogle Scholar
- Gu BK, Shin MK, Sohn KW, Kim SI, Kim SJ (2007) Direct fabrication of twisted nanofibers by electrospinning. Appl Phys Lett 90:263902/1–3Google Scholar
- Liu LQ, Eder M, Burgert I, Tasis D, Prato M, Wagner HD (2007) One step electrospun nanofiber-based composite ropes. Appl Phys Lett 90:083108/1–3Google Scholar
- Maheshwari S, Chang HC (2009) Assembly of multi-stranded nanofiber threads through AC electrospinning. Adv Mater 21:349–354View ArticleGoogle Scholar
- Hansen BJ, Liu Y, Yang RS, Wang ZL (2010) Hybrid nanogenerator for concurrently harvesting biomechanical and biochemical energy. ACS Nano 4:3647–3652View ArticleGoogle Scholar
- Xiao X, Yuan LY, Zhong JW, Ding TP, Liu Y, Cai ZX, Rong YG, Han HW, Zhou J, Wang ZL (2011) High-strain sensors based on ZnO nanowire/polystyrene hybridized flexible films. Adv Mater 23:5440–5444View ArticleGoogle Scholar
- Lotus AF, Bender ET, Evans EA, Ramsier RD, Reneker DH, Chase GG (2008) Electrical, structural, and chemical properties of semiconducting metal oxide nanofiber yarns. J Appl Phys 103:024910/1–6View ArticleGoogle Scholar
- Lotus AF, Bhargava S, Bender ET, Evans EA, Ramsier RD, Reneker DH, Chase GG (2009) Electrospinning route for the fabrication of p-n junction using nanofiber yarns. J Appl Phys 106:014303/1–4View ArticleGoogle Scholar
- Lin DP, He HW, Huang YY, Han WP, Yu GF, Yan X, Long YZ, Xia LH (2014) Twisted microropes for stretchable devices based on electrospun conducting polymer fibers doped with ionic liquid. J Mater Chem C 2(42):8962–8966View ArticleGoogle Scholar
- Chen GX, Li YJ, Shimizu H (2007) Ultrahigh-shear processing for the preparation of polymer/carbon nanotube composites. Carbon 45:2334–2340View ArticleGoogle Scholar
- Owens FJ, Jayakody JRP, Greenbaum SGC (2006) Characterization of single walled carbon nanotube: polyvinylene difluoride composites. Compos Sci Technol 66:1280–4View ArticleGoogle Scholar
- Huang S, Yee WA, Tjiu WC, Liu Y, Kotaki M, Yin CFB, Jan MA, Liu TX, Lu XH (2008) Electrospinning of polyvinylidene difluoride with carbon nanotubes: synergistic effects of extensional force and interfacial interaction on crystalline structures. Langmuir 24:13621–13626View ArticleGoogle Scholar
- Wang M, Shi JH, Pramoda KP, Goh SH (2007) Microstructure, crystallization and dynamic mechanical behaviour of poly(vinylidene fluoride) composites containing poly(methyl methacrylate)-grafted multiwalled carbon nanotubes. Nanotechnology 18:235701View ArticleGoogle Scholar
- Baughman RH, Zakhidov AA, de Heer WA (2002) Carbon nanotubes—the route toward applications. Science 297:787–792View ArticleGoogle Scholar
- Collins PG, Arnold MS, Avouris P (2001) Engineering carbon nanotubes and nanotube circuits using electrical breakdown. Science 292:706–709View ArticleGoogle Scholar
- Zhang QH, Lippits DR, Rastogi S (2006) Dispersion and rheological aspects of SWNTs in ultrahigh molecular weight polyethylene. Macromolecules 39(2):658–666View ArticleGoogle Scholar
- Zhou CF, Liu T, Wang T, Kumar S (2006) PAN/SAN/SWNT ternary composite: pore size control and electrochemical supercapacitor behavior. Polymer 47:5831–5837View ArticleGoogle Scholar
- Qian D, Dickey EC, Andrews R, Rantell T (2000) Load transfer and deformation mechanisms in carbon nanotube-polystyrene composites. Appl Phy Lett 76:2868–2870View ArticleGoogle Scholar
- Meng Q, Wang K, Guo W, Fang J, Wei Z, She XL (2014) Thread‐like supercapacitors based on one‐step spun nanocomposite yarns. Small 10(15):3187–3193View ArticleGoogle Scholar
- Lima MD, Hussain MW, Spinks GM, Naficy S, Hagenasr D, Bykova JS, Tolly D and Baughman RH (2015) Efficient, absorption-powered artificial muscles based on carbon nanotube hybrid yarns. Small. doi: 10.1002/smll.201500424.Google Scholar
- Sarvi A, Chimello V, Silva AB, Bretas RES, Sundararaj U (2014) Coaxial electrospun nanofibers of poly (vinylidene fluoride)/polyaniline filled with multi-walled carbon nanotubes. Polymer Compos 35(6):1198–1203Google Scholar
- Georgousis G, Pandis C, Kalamiotis A, Georgiopoulos P, Kyritsis A, Kontou E, Omastova M (2015) Strain sensing in polymer/carbon nanotube composites by electrical resistance measurement. Compos Part B: Eng 68:162–169View ArticleGoogle Scholar