Article www.acsaem.org
Cite This: ACS Appl. Energy Mater. 2018, 1, 3103−3112
Biomechanical and Acoustic Energy Harvesting from TiO2 Nanoparticle Modulated PVDF Nanofiber Made High Performance Nanogenerator Md. Mehebub Alam,† Ayesha Sultana,† and Dipankar Mandal*,†,‡ †
Organic Nano-Piezoelectric Device Laboratory, Department of Physics, Jadavpur University, Kolkata 700032, India Institute of Nano Science and Technology (INST), Phase-10, Sector-64, Mohali 160062, India
‡
Downloaded via IOWA STATE UNIV on January 7, 2019 at 22:14:41 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.
S Supporting Information *
ABSTRACT: An integrated platform made with a piezoelectric nanogenerator (NG) is designed to convert daily human activities and acoustic vibration into useable electrical energy. The titanium dioxide (TiO2) nanoparticles (NPs) are playing a significant role as external fillers in poly(vinylidene fluoride) (PVDF) electrospun nanofiber that improves the overall performance of the NG. It effectively enhanced the piezoelectric β-phase content (16% higher F (β)) and mechanical (148% increment of tensile strength) properties of composite PVDF nanofiber. The superior integration of NG has been demonstrated to generate electricity from a human gait. The acoustic sensitivity and energy conversion efficiency are found to be 26 V Pa−1 and 61%, respectively, which are superior in comparison to the reported results. By scavenging the mechanical energy, NG is capable of charging up a 1 μF capacitor; for example, ∼20 V is within 50 s that ensures its ability to power up commercial LED tape and a LCD screen. Thus, in this work, a high performance piezoelectric NG is presented that has potential application in the health care sector and robotics area, in particular for use as a self-powered system. KEYWORDS: TiO2 doped PVDF nanofiber, electrospinning, β-phase, wearable and biomechanical energy scavenging, acoustic nanogenerator human skin by belt or integrated into a textile.16−18 However, some drawbacks are associated with harvesting the mechanical energy from human activities. For example, the garment or belt needs to be tight enough to catch an adequate level of signal which results in an inherent trade-off between comfort and sensitivity. It becomes more uncomfortable in the case of long time application. Thus, an alternative way of energy harvesting from human activities without compromising comfort is of prime importance. Recently, energy harvesting from the several random energy sources such as irregular vibrations, noise, wind flow, water flow, raindrops, and ultrasonic wave are also carried out by piezoelectric NG.19−23 In contrast, acoustic energy harvesting becomes increasingly interesting as it is a clean, omnipresent, sustainable energy source.24−26 Recently, utility of an acoustic energy harvester for designing a self-powered sound recorder or voiceprint sensor is also demonstrated.27,28 Thus, it is expected that NG can be used in noisy places where energy harvesting from both human activities and acoustic noise is feasible. From the material point of view, poly(vinylidene fluoride) (PVDF) has positioned itself as a most studied piezoelectric polymer due to its superior ferro-, piezo-,
1. INTRODUCTION A drastic change has been observed in our modern life style with uses of low powered electronic units also increasing rapidly.1−3 Moreover, these electronic devices are also shrinking in size, and the requirement of very low power consumption becomes a unique characteristic for the future technology. Several limitations of conventional batteries are driving rapid development toward self-powered systems, particularly scavenging the mechanical and thermal energy from the surrounding environment.4,5 For example, batteries have a limited lifetime and thus need to be replaced or recharged repeatedly. There are several energies (i.e., solar or thermal energy) that can be harvested, but most of them are time and location dependent. In contrast, the existence of mechanical energy with variable frequencies and amplitudes is everywhere regardless of its time dependency. Therefore, a piezoelectric and triboelectric nanogenerator (NG) based mechanical energy harvesting approach has an enormous appeal.1−6 Noteworthy to mention is that the human body is generating several kilowatts of energy during daily activities.2 Thus, biomechanical energy harvesting becomes a prime focus of research interest.7−9 Several approaches have already been initiated for human body energy harvesting from the movements of individual body parts and respiration.10−15 In most of the cases the devices are directly attached to the © 2018 American Chemical Society
Received: February 13, 2018 Accepted: June 7, 2018 Published: June 7, 2018 3103
DOI: 10.1021/acsaem.8b00216 ACS Appl. Energy Mater. 2018, 1, 3103−3112
Article
ACS Applied Energy Materials
Figure 1. Schematic presentation of NG fabrication. (a) The electrospun fiber mat is sandwiched between two conducting fabrics. (b) The edges are encapsulated by adhesive tape. The enlarge cross-sectional view is demonstrating the different layers in the NG at the edges.
Figure 2. Surface morphology of (a) PNF and (b) TPNF mats. Corresponding insets are ensuring the reduction of average fiber diameter due to TiO2 NPs doping. The XRD pattern of (c) PNF and (d) TPNF mats. (e) FT-IR spectra of PVDF powder and PNF and TPNF mats. (f) Stress− strain curves of the PNF and TPNF mats.
3104
DOI: 10.1021/acsaem.8b00216 ACS Appl. Energy Mater. 2018, 1, 3103−3112
Article
ACS Applied Energy Materials
Figure 3. Digital photographs showing (a) the prepared TPNF mat and its (b) foldability, (c) rollability, and (d) wearability.
Figure 4. Open-circuit output voltages from the NGs made of (a) PNF and (b) TPNF mats. Output currents from (c) PNF and (d) TPNF based NG under repeated finger touch.
and pyroelectricity, apart from its flexibility, lightweight, biocompatibility, cost-effectiveness, and nontoxicity.29,30 PVDF has polar and nonpolar phases (i.e., α, γ, β, δ, and ε), and the nonpolar α-phase is the stable phase among them.29 However, β-phase is the most desirable as it exhibits the best piezo-, pyro-, and ferroelectric properties.29,31 Thus, several approaches such as mechanical stretching, thermal annealing, or electrical poling are typically attempted to induce the βphase. But, due to several limitations, it may fail to get β-phase containing PVDF in a desirable form through these methods.32 On the other hand, electrospinning is a technique that involves mechanical stretching and electrical poling simultaneously and it can easily produce β-phase in nanofibers.33,34 It has been shown that an electrospun PVDF nanofiber mat exhibits superior flexibility, wearability, air permeability, and higher energy conversion efficiency compared to those made of films.35,36 More importantly postpoling treatment is not required which is a typical step for high performance device fabrication toward piezoelectric based mechanical energy harvesting application.37 However, improvement of output performance of electrospun fiber based NG is still a challenging task to make it suitable for practical application.7 Therefore, it is expected that the improvement of piezoelectric β-phase content and mechanical property can effectively improve the output performance of the corresponding
nanogenerator.38 Very recently, researchers have been focused on the doping of semiconducting fillers (e.g., ZnO and MoS2) to improve the β-phase content of PVDF fiber.39,40 It is also noticed that TiO2 is a wide indirect band gap semiconductor that exhibits prominent thermal and chemical stability, high photoconversion efficiency, or photostability and most importantly it can make PVDF more suitable for energy harvesting and storage application.41,42 Herein, we have prepared a PVDF/TiO2 electrospun fiber mat based flexible and wearable NG to harvest mechanical energy from regular human activities and acoustic vibration. The sensitivity and efficiency for acoustic to electrical energy conversion of the NG exhibit up to 26 V Pa−1 and 61%, respectively. It should be also noted that, within 50 s, a 1 μF capacitor is possible to charge up to 20 V that powers up a LED tape and LCD screen individually.
2. EXPERIMENTAL SECTION 2.1. Materials. PVDF powder (Alfa Aesar), DMF, acetone (Merck Chemical), TiO2 powder (AEROXIDE TiO2 P 25, Evonik Degussa) and nickel−copper−nickel plated fine knit polyester fabric (Coatex Industries, India) of thickness 0.1 ± 0.01 mm with surface resistance 0.05−0.1 Ω/sq. 2.2. Preparation of NFs Mat. A 1.2 g amount of PVDF powder was dissolved in 10 mL of solvent consisting of 6 mL of DMF and 4 mL of acetone. Then 0.5 wt % of TiO2 NPs of average diameter ∼ 20 3105
DOI: 10.1021/acsaem.8b00216 ACS Appl. Energy Mater. 2018, 1, 3103−3112
Article
ACS Applied Energy Materials
Figure 5. Working mechanism of the NG at (a) the initial state (enlarged view shows that the dipoles are aligned along the thickness direction), (b) pressed state, and (c) released state. (d) Press and release states resulting in positive and negative peaks of AC current generated from the NG. nm was added into the PVDF solution. A schematic presentation of the electrospinning setup employed in this work is shown in Supporting Information Figure S1. The prepared PVDF solution was put into a hypodermic syringe and flowed through the needle with a feeding rate of 1.5 mL h−1. Once the solution reached the needle tip, then it was attracted toward the collector (kept at 14 cm apart from the needle tip) under the influence of applied voltage of 10 kV. Finally, the TiO2 doped PVDF nanofibers (TPNFs) are amassed on the collector. A reference mat was also fabricated with pure PVDF nanofiber (PNF). 2.3. Fabrication of NG. After the preparation of a 250 μm thick electrospun mat, sandwich-like NG was prepared by a simple and scalable method as shown in the schematic presentation in Figure 1. In short, two electrodes (conducting fabrics) of area 60 cm2 are physically attached on both sides of the electrospun mat of length 9.0 cm and breadth 7.5 cm (Figure 1a). The edges are encapsulated by adhesive tape to make a compact structure (Figure 1b). The enlarged view (Figure 1b) demonstrates the cross-sectional view of the NG at the edge. 2.4. Characterization. FT-IR spectroscopy (Bruker, Tensor II) and X-ray diffraction (XRD; Bruker, D8 Advance diffractometer) studies were carried out to evaluate crystallographic information on the NF mats. Surface morphologies of the NF mats were carried out by field emission scanning electron microscope (FE-SEM; INSPECT F50). A universal testing machine (Tinius Olsen H50KS) was employed to test the mechanical property (stress−strain measurement) of the NF mats. Output voltage was measured by National Instrument (NI) Data acquisition (DAQ) device (NI, USB 6000) which was interfaced with a computer by LabVIEW program. The short-circuit currents were recorded by using a picoammeter (Keithley 6485).
phenomenon could be explained by taking into consideration the entire electrospinning process. It depends on the Coulomb force (F = qE) exerted upon the charge (q) of the surface of the fluid due to the applied electric field (E).39,40 Since the semiconducting TiO2 NPs comprising PVDF composite solution must have higher conductivity compared to the neat PVDF solution, thus, the PVDF/TiO 2 composite jet experiences a stronger force in comparison with that of pure PVDF jet under the same applied electric field strength, resulting in a decrease of fiber diameter after doping of TiO2 NPs. The reduction of fiber diameter may also cause improvement in mechanical as well as piezoelectric properties of the TPNF mat.43 X-ray diffraction peaks appeared at 2θ = 20.9° and 36.9° revealing the electroactive β-phase induction in both the PNF and TPNF mats (Figure 2c,d).40,44 Both mechanical stretching and electrical poling during the electrospinning process triggered the β-phase in the NF mats. However, after TiO2 doping, diffraction peaks at 2θ = 18.8° and 26.9° corresponding to the α-phase in PNF (Figure 2c) are almost diminished in the TPNF mat (Figure 2d).40,44 In addition, there are additional peaks at 25.8° and 27.9° in the TPNF mat corresponding to the (101) and (110) diffraction peaks of TiO2 NPs, respectively. These are direct evidence of the existence of TiO2 NPs in the TPNF mat. The presence of TiO2 NPs in the TPNF is also shown in the TEM image. It is found that the TiO2 NPs are embedded inside the individual nanofiber as shown in Figure S2. For further confirmation of crystal structures of the NF mats, FT-IR spectra were also carried out and shown in Figure 2e. The PVDF powder that was used for solution preparation consists of solely mainly α-phase as evident from the peaks at 613, 764, 796, 974, 1018, 1148, 1210, and 1381 cm−1.29 Furthermore, no vibrational peaks at 840 and 1275 cm−1 ensure that there is no β-phase present in the PVDF powder. However, weak vibrational bands at 613 and 764 cm−1 with a
3. RESULTS AND DISCUSSION FE-SEM images of fabricated PNF (Figure 2a) and TPNF (Figure 2b) mats depict that randomly oriented fibers are formed. The corresponding histogram profile shows that the average fiber diameter of the TPNF mat is distinctly decreased in comparison with that of the PNF mat. This is because of the difference in conductivity of the electrospun solutions. This 3106
DOI: 10.1021/acsaem.8b00216 ACS Appl. Energy Mater. 2018, 1, 3103−3112
Article
ACS Applied Energy Materials
Figure 6. (a) Photographic illustration of arm swings with the mounted NG on a T-shirt in the armpit region. Open-circuit voltage generated by the NG from arm swings during (b) walking and (c) running states. (d) Photographic illustration of leg (foot) swings with the mounted NG on a slipper. Open-circuit voltage generated by the NG from repeated foot on leg (foot) swings during (e) walking and (f) running states.
newly appeared band at 1275 cm−1 ensured the coexistence of α-phase along with the β-phase in PNF.29,40 But, the vibrational bands corresponding to α-phase in the TPNF mat are almost diminished. Additionally, the intensity of 1275 cm−1 band in TPNF becomes stronger which ensures the improvement of β-phase due to TiO2 NPs doping. Thus, a very small amount of TiO2 NPs can improve the β-phase content in PVDF NF mats. The relative proportions of β-phase (F(β)) in the NF mats are estimated from the equation mentioned in ref 23. It indicates that the TPNF exhibits 93% of the β-phase that is 16% higher than the PNF mat. This improvement arises due to the reduction of fiber diameter (Figure 2a,b) and surface charge−dipole interaction (Supporting Information Figure S3).40 Stress−strain curves of PNF and TPNF mats are shown in Figure 2f. Initially, the network-like structures of the nanofibers show a strong opposition against the deformation. Then, slight alignment of the fibers along the tensile force might occur. After that the mat dimension along the applied
stress direction is extended, which leads to a decrease in the cross-section (Supporting Information Figure S4). Thus, the stress−strain curve shows a nonlinear nature up to the final breakage point at ultimate strain. The deformation behavior of the fibers mat is also consistent with that from previous work.38,45−47 However, tensile strength and fracture strain are clearly enhanced for the TPNF mat in comparison to the PNF mat. Young’s modulus of the TPNF mat is found to be 22 N/ mm2, which is ∼129% higher than that of the PNF mat. A decrease in the fiber diameter and the interactions between TiO2 NPs and PVDF lead to improved mechanical properties. Thus, a TPNF mat with higher mechanical strength is anticipated to be more suitable in mechanical energy harvesting application.48 The digital photographs of the prepared TPNF mat, its foldability, rollability, and wearability are also shown in Figure 3. Thus, the TPNF mat is suitable for the fabrication of a flexible and wearable nanogenerator. It is found that the NG 3107
DOI: 10.1021/acsaem.8b00216 ACS Appl. Energy Mater. 2018, 1, 3103−3112
Article
ACS Applied Energy Materials
Figure 7. (a) Illustration of arm swings with the mounted NG on a T-shirt (NG-1 and NG2) and leg (foot) swings with the mounted NG on a slipper (NG-3 and NG-4). (b) The corresponding output voltage when the NGs are in series connection during running state. (c) Schematic presenting a typical circuit diagram of capacitor charging that powered up a LED by NGs, connected in series. (d) Capacitor charging curve of a 1 μF capacitor by the motion of extremities during running state (inset shows the lighting of LED bulb through charged capacitor).
moment and thickness of the mat under applied pressure.33 Thus, the application of a compressive stress leads to a change in the polarization of the mat, and the generated charges start to flow through an external circuit, resulting in an electrical signal (Figure 5b). After the external stress is removed, the polarization is restored and current starts to flow in the opposite direction, resulting in a reverse signal (Figure 5c).49 Thus, the NG delivers typical AC signals under periodic press and release motions (Figure 5d). However, the TPNF based NG shows superior piezoelectric throughput due to the overall improved properties of the TPNF mat compared to that of the PNF mat as discussed before. Furthermore, the piezoelectric coefficient of the TPNG based NG is found to be 39 pC/N.50 Therefore, further characterizations are carried out with the TPNF based NG only. The characterization of the biomechanical−electrical energy conversion is inspired by the motion of extremities during movement of the human body for energy harvesting purposes as they are triggered in most of the normal activities including walking. During walking (or running), there are to and fro motions of the feet (z direction) and hands (perpendicular to z direction) and this consideration implies that the to and fro motions of the extremities are the only interesting parameters to be considered.51 Here, NG is attached in the armpit region to demonstrate mechanical energy harvesting throughout the swinging motion of a hand (arm) during walking/running in a normal jogging procedure (Figure 6a). The corresponding output voltages of around 1 and 1.5 V during walking and running are shown in Figure 6b,c, respectively. During the swinging motion, the NG experienced repeated arm pressure and that pressure was transformed into an electrical signal. A similar experiment was also carried out when the NG was
Figure 8. Output voltage generation from NG subjected to weight of the people during walking and jumping over it.
based on PNF mat exhibited an open-circuit output (peak-topeak) voltage of 7 V (Figure 4a), whereas 11.5 V (Figure 4b) is observed for the TPNF based NG under compression of a human finger touch of force ∼ 5 N in a vertical direction. Short-circuit (peak-to-peak) currents under the same applied force are found to be 104 nA (Figure 4c) and 176 nA (Figure 4d) from PNF and TPNF mat based NGs, respectively. Figure 5 shows the working mechanism of the NG under repeated press and release motion. Due to in situ poling during electrospinning, the dipoles of PVDF are aligned inside the fibers as shown in the Figure 5a (enlarged view). Thus, electrospun fiber mat is a polarized material in which dipoles are aligned along the thickness, establishing a total polarization inside the mat (Figure. 5a). Hence, the current from the electrospun fiber mat is generated due to change in the total polarization that results in the change in surface charge during repetitive pressing and releasing. The change in polarization mainly arises from a change of total dipole 3108
DOI: 10.1021/acsaem.8b00216 ACS Appl. Energy Mater. 2018, 1, 3103−3112
Article
ACS Applied Energy Materials
Figure 9. (a) Photograph of the NG placed on a speaker for monitoring the sound vibration. (b) Output voltage as a function of different SPL (inset shows direct lighting of a LED). Variations of (c) output voltage and current and (d) power density of the NG across load resistances. (e) Voltage−time curve of the capacitor charging by the NG driven through sound vibration (inset schematic presenting the typical circuit diagram of capacitor charging for lighting a LED tape by the NG). (f) Snapshots of the LED tape of 100 LED bulbs and a LCD screen (inset) powered up by the charged capacitor.
for designing smart footpath or a dance floor. The good stability of the NG is also found as there is no degradation in output voltage after continuous repeated pressing by an imparting machine up to 2000 s as shown in Figure S5. To test the performance of the NG, a different type of experiment was also carried out where the NG is attached to a speaker as shown in Figure 9a for harvesting mechanical energy from the acoustic vibration. It should be noted that there are plenty of similar vibrational sources available throughout, which can be effectively used as an electrical energy source if NG is properly integrated. In our experiment, when music is on (a pop song was played), NG produces an open-circuit output voltage that also increased with increasing SPL and saturated at 90 dB, shown in Figure 9b and in Supporting Information, Figure S6. The maximum output peak-to-peak voltage is found to be 17.5 V indicating that the NG could be useful for monitoring noise pollution and, more interestingly, tiny portable electronic devices might be operated in a self-powered mode as well. During the presence of music, sound waves propagate through the air medium and once it reaches the surface of the NG cause it to vibrate and subsequently convert it to an electrical signal by the piezoelectric nanofibers present in the NG. Figure 9c presents the variation of output voltage across load resistances (RL). The short-circuit current (I) and power (P), related to the output voltage by the relation P = IV = V2/
attached onto a slipper for converting foot pressure into an electrical signal. Figure 6d shows the swinging motion of legs (feet) during walking or running, and the corresponding output voltages of around 1.2 and 1.6 V are shown in Figure 6e,f, respectively. Multiple NGs are also utilized for harvesting energy from the swinging motion of the extremities during running mode. The schematic presentation to demonstrate the attachments of the NGs are shown in Figure 7a. NGs are connected in series to add up for gaining a higher voltage value of 2.8 V (Figure 7b). Furthermore, the generated electrical energy was employed to charge up a 1 μF capacitor. The schematic presentation in Figure 7c demonstrates that the NGs are connected in series and the output signal from the NGs are rectified by a bridge rectifier. Rectified signals are applied across the capacitor to charge it up (when the key “K” is connected to point “A”). The charged capacitor then employed to lighting a blue LED bulb (when K is connected to the point “B”). The capacitor charging result shows that up to 1.3 V is possible to store within 20 s, which is enough to light a blue LED bulb. The capacitor charging results are shown in Figure 7d. The inset photograph of Figure 7d shows a blue LED at the moment of being lit up by the charged capacitor. We have also attached the NG on the floor and harvested energy from the weight of the people walking/jumping over it, examined and shown in Figure 8. These results promise the utility of the NG 3109
DOI: 10.1021/acsaem.8b00216 ACS Appl. Energy Mater. 2018, 1, 3103−3112
Article
ACS Applied Energy Materials RL, is also shown in Figure 9c,d, respectively. Output voltage, current, and power density (P/A, where A is the electrode area) show the typical nature across the resistances, where voltage gradually increases to a maximum value, current gradually decreases, and power density exhibits a peak value. Under sound vibration, the NG is also capable of powering a blue LED, directly connected to it (inset of Figure 9b and Video S1). Furthermore, high acoustic sensitivity make the NG promising for harvesting vibrational energy available in the environment, such as wind flow, water waves, and transportation vehicles. The acoustic sensitivity (Sa) of this NG is calculated from the equation mentioned in ref 40. The sensitivity becomes as high as 26 V Pa−1 for acoustic to electrical energy conversion, which is much superior than recently reported results.40,52−54 A 1 μF capacitor is also successfully charged up, using a typical full wave rectifier circuit. The typical circuit diagram for capacitor charging to power up the LED tape is shown in the inset of Figure 9e. It is found that within 50 s the NG charges the capacitor up to 20 V with time constant (τ) 22 s. The storage voltage is enough to power up the LED tape and a LCD screen, shown in Figure 9f and Video S2. The power output of the NG is found to be 4 μW.40 Thus, the overall P efficiency (ηHG) = out × 100% is found to be 61%, a value
■
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected];
[email protected]. Tel.: +91 33 2414 6666 × 2880. Fax: +91 33 2413 8917. ORCID
Dipankar Mandal: 0000-0003-2167-2706 Funding
We thank the Science and Engineering Research Board (SERB/1759/2014-15), Govt. of India for the support. Md.M.A. is supported by the UGC-BSR fellowship (No. P1/ RS/191/14). We also thank DST, Govt. of India for developing instrumental facilities under the FIST-II programme, Department of Physics, Jadavpur University, Kolkata, India. Notes
The authors declare no competing financial interest.
■
Pin
which is comparable to recently published acoustic energy harvesters.55,56 It is noteworthy to mention that here Pin = 6.5 μW·55 The high β-phase content, improved mechanical property, and adequate flexibility make the NG highly sensitive and efficient for acoustic to electrical energy conversion. A drumming cartoon toy was also utilized, and NG was attached to the top head of the drum (Supporting Information Figure S7). During drumming, the NG delivers an output peak-to-peak voltage of 2 V (Supporting Information Figure S7). These merits provide great potential for a smart musical instrument, smart toy, or robotic application.
REFERENCES
(1) Wang, Z. L. Self-Powered Nanosensors and Nanosystems. Adv. Mater. 2012, 24, 280−285. (2) Paradiso, J. A.; Starner, T. Energy Scavenging for Mobile and Wireless Electronics. Pervasive Comput. 2005, 4, 18. (3) Bhatnagar, V.; Owende, P. Energy Harvesting for Assistive and Mobile Applications. Energy Sci. Eng. 2015, 3, 153−173. (4) Mitcheson, P. D.; Yeatman, E. M.; Rao, G. K.; Holmes, A. S.; Green, T. C. Energy Harvesting from Human and Machine Motion for Wireless Electronic Devices. Proc. IEEE 2008, 96, 1457−1486. (5) Zhong, Q.; Zhong, J.; Hu, B.; Hu, Q.; Zhou, J.; Wang, Z. L. A Paper-based Nanogenerator as a Power Source and Active Sensor. Energy Environ. Sci. 2013, 6, 1779−1784. (6) Garain, S.; Jana, S.; Sinha, T. K.; Mandal, D. Design of In Situ Poled Ce3+‑Doped Electrospun PVDF/Graphene Composite Nanofibers for Fabrication of Nanopressure Sensor and Ultrasensitive Acoustic Nanogenerator. ACS Appl. Mater. Interfaces 2016, 8, 4532− 4540. (7) Dong, K.; Wang, Y.-C.; Deng, J.; Dai, Y.; Zhang, S. L.; Zou, H.; Gu, B.; Sun, B.; Wang, Z. L. A Highly Stretchable and Washable AllYarn- Based Self-Charging Knitting Power Textile Composed of Fiber Triboelectric Nanogenerators and Supercapacitors. ACS Nano 2017, 11, 9490−9499. (8) Wu, N.; Cheng, X.; Zhong, Q.; Zhong, J.; Li, W.; Wang, B.; Hu, B.; Zhou, J. Cellular Polypropylene Piezoelectret for Human Body Energy Harvesting and Health Monitoring. Adv. Funct. Mater. 2015, 25, 4788−4794. (9) Dong, K.; Deng, J.; Zi, Y.; Wang, Y.-C.; Xu, C.; Zou, H.; Ding, W.; Dai, Y.; Gu, B.; Sun, B.; Wang, Z. L. 3D Orthogonal Woven Triboelectric Nanogenerator for Effective Biomechanical Energy Harvesting and as Self-Powered Active Motion Sensors. Adv. Mater. 2017, 29, 1702648. (10) Choi, B. M.-Y.; Choi, D.; Jin, M.-J.; Kim, I.; Kim, S.-H.; Choi, J.-Y.; Lee, S. Y.; Kim, J. M.; Kim, S.-W. Mechanically Powered Transparent Flexible Charge-Generating Nanodevices with Piezoelectric ZnO Nanorods. Adv. Mater. 2009, 21, 2185−2189. (11) Sultana, A.; Alam, M. M.; Garain, S.; Sinha, T. K.; Middya, T. R.; Mandal, D. An Effective Electrical Throughput from PANI Supplement ZnS Nanorods and PDMS-Based Flexible Piezoelectric Nanogenerator for Power up Portable Electronic Devices: An Alternative of MWCNT Filler. ACS Appl. Mater. Interfaces 2015, 7, 19091−19097.
4. CONCLUSION We have fabricated an ultrasensitive and highly efficient piezoelectric NG based on a TiO2 NPs doped PVDF electrospun mat. It becomes a suitable material for piezoelectric NG due to the enhancement of β-phase content, flexibility, and mechanical property. Mechanical energy harvesting from human daily activities such as walking, running, and jumping is demonstrated. The outstanding electrical output from NG under acoustic vibration is sufficient to directly power a blue LED, charge up a capacitor to 20 V, and power up LED tape and an LCD screen. This work thus represents a crucial step in building battery-less self-powered sensors for biomedicine or robotics application and developing smart footpaths, train stations, bus terminals, dance clubs, and musical instruments for smart city designing.
■
the NG to harvest energy from a drumming cartoon toy (PDF) Video S1 showing NG powering blue LED (AVI) Video S2 showing storage voltage powering LED tape and LCD screen (AVI)
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsaem.8b00216. Schematic of electrospinning setup, FT-IR spectra of the mats, TEM image of TPNF, digital photograph of the TPNF mat when clipped in universal testing machine, stability test, output voltages from NG and under different average SPL (40−90 dB), and applications of 3110
DOI: 10.1021/acsaem.8b00216 ACS Appl. Energy Mater. 2018, 1, 3103−3112
Article
ACS Applied Energy Materials (12) Saravanakumar, B.; Mohan, R.; Thiyagarajan, K.; Kim, S.-J. Fabrication of a ZnO Nanogenerator for Eco-friendly Biomechanical Energy Harvesting. RSC Adv. 2013, 3, 16646−16656. (13) Lee, S.; Bae, S.-H.; Lin, L.; Yang, Y.; Park, C.; Kim, S.-W.; Cha, S. N.; Kim, H.; Park, Y. J.; Wang, Z. L. Super-Flexible Nanogenerator for Energy Harvesting from Gentle Wind and as an Active Deformation Sensor. Adv. Funct. Mater. 2013, 23, 2445−2449. (14) Cheng, Y.; Wang, C.; Zhonga, J.; Lin, S.; Xiao, Y.; Zhong, Q.; Jiang, H.; Wu, N.; Li, W.; Chen, S.; Wang, B.; Zhang, Y.; Zhou, J. Electrospun Polyetherimide Electret Nonwoven for Bi-Functional Smart Face Mask. Nano Energy 2017, 34, 562−569. (15) Zhong, J.; Zhong, Q.; Chen, G.; Hu, B.; Zhao, S.; Li, X.; Wu, N.; Li, W.; Yu, H.; Zhou, J. Surface Charge Self-recovering Electret Film for Wearable Energy Conversion in a Harsh Environment. Energy Environ. Sci. 2016, 9, 3085−3091. (16) Zhang, M.; Gao, T.; Wang, J.; Liao, J.; Qiu, Y.; Yang, Q.; Xue, H.; Shi, Z.; Zhao, Y.; Xiong, Z.; Chen, L. A. Hybrid Fibers based Wearable Fabric Piezoelectric Nanogenerator for Energy Harvesting Application. Nano Energy 2015, 13, 298−305. (17) Lee, M.; Chen, C.-Y.; Wang, S.; Cha, S. N.; Park, Y. J.; Kim, J. M.; Chou, L.-J.; Wang, Z. L. A Hybrid Piezoelectric Structure for Wearable Nanogenerators. Adv. Mater. 2012, 24, 1759−1764. (18) Seung, W.; Gupta, M. K.; Lee, K. Y.; Shin, K.-S.; Lee, J.-H.; Kim, T. Y.; Kim, S.; Lin, J.; Kim, J. H.; Kim, S.-W. Nanopatterned Textile-Based Wearable Triboelectric Nanogenerator. ACS Nano 2015, 9, 3501−3509. (19) Wang, Z.; Pan, X.; He, Y.; Hu, Y.; Gu, H.; Wang, Y. Piezoelectric Nanowires in Energy Harvesting Applications. Adv. Mater. Sci. Eng. 2015, 2015, 165631. (20) Li, Z.; Wang, Z. L. Air/Liquid-Pressure and Heartbeat-Driven Flexible Fiber Nanogenerators as a Micro/nano-Power Source or Diagnostic Sensor. Adv. Mater. 2011, 23, 84−89. (21) Guigon, R.; Chaillout, J.-J.; Jager, T.; Despesse, G. Harvesting Raindrop Energy: Experimental Study. Smart Mater. Struct. 2008, 17, 015039. (22) Wang, X.; Song, J.; Liu, J.; Wang, Z. L. Direct-Current Nanogenerator Driven by Ultrasonic Waves. Science 2007, 316, 102− 105. (23) Alam, M. M.; Ghosh, S. K.; Sultana, A.; Mandal, D. An Effective Wind Energy Harvester of Paper Ash-Mediated Rapidly Synthesized ZnO Nanoparticle-Interfaced Electrospun PVDF Fiber. ACS Sustainable Chem. Eng. 2018, 6, 292−299. (24) Cha, B. S. N.; Seo, J.-S.; Kim, S. M.; Kim, H. J.; Park, Y. J.; Kim, S.-W.; Kim, J. M. Sound-Driven Piezoelectric Nanowire-Based Nanogenerators. Adv. Mater. 2010, 22, 4726−4730. (25) Li, B.; You, J. H.; Kim, Y. - J. Low Frequency Acoustic Energy Harvesting Using PZT Piezoelectric Plates in a Straight Tube Resonator. Smart Mater. Struct. 2013, 22, 055013. (26) Li, B.; Laviage, A. J.; You, J. H.; Kim, Y.-J. Acoustic Energy Harvesting Using Quarter-Wavelength Straight-Tube Resonator. Proc. ASME Int. Mech. Eng. Congr. Expo.- 2012 2012, 12, 467−473. (27) Fan, X.; Chen, J.; Yang, J.; Bai, P.; Li, Z.; Wang, Z. L. Ultrathin, Rollable, Paper-Based Triboelectric Nanogenerator for Acoustic Energy Harvesting and Self-Powered Sound Recording. ACS Nano 2015, 9, 4236−4243. (28) Li, W.; Zhao, S.; Wu, N.; Zhong, J.; Wang, B.; Lin, S.; Chen, S.; Yuan, F.; Jiang, H.; Xiao, Y.; Hu, B.; Zhou, J. Sensitivity-Enhanced Wearable Active Voiceprint Sensor Based on Cellular Polypropylene Piezoelectret. ACS Appl. Mater. Interfaces 2017, 9, 23716−23722. (29) Martins, P.; Lopes, A. C.; Lanceros-Mendez, S. Electroactive phases of Poly (vinylidene fluoride): Determination, Processing and Applications. Prog. Polym. Sci. 2014, 39, 683−706. (30) Lovinger, A. J. Ferroelectric polymers. Science 1983, 220, 1115−1121. (31) Sencadas, V.; Gregorio, R., Jr.; Lanceros-Méndez, S. Alpha to Beta Phase Transformation and Microestructural Changes of PVDF Films Induced by Uniaxial Stretch. J. Macromol. Sci., Part B: Phys. 2009, 48, 514−525.
(32) El Mohajir, B.-E.; Heymans, N. Changes in Structural and Mechanical Behaviour of PVDF with Processing and Thermomechanical Treatments. 1. Change in Structure. Polymer 2001, 42, 5661−5667. (33) Mandal, D.; Yoon, S.; Kim, K. J. Origin of Piezoelectricity in an Electrospun Poly (vinylidene fluoride-trifluoroethylene) Nanofiber Web-Based Nanogenerator and Nano-Pressure Sensor. Macromol. Rapid Commun. 2011, 32, 831−837. (34) Chang, C.; Tran, V. H.; Wang, J.; Fuh, Y.-K.; Lin, L. DirectWrite Piezoelectric Polymeric Nanogenerator with High Energy Conversion Efficiency. Nano Lett. 2010, 10, 726−731. (35) Gheibi, A.; Bagherzadeh, R.; Merati, A. A.; Latifi, M. Electrical Power Generation from Piezoelectric Electrospun Nanofibers Membranes: Electrospinning Parameters Optimization and Effect of Membranes Thickness on Output Electrical Voltage. J. Polym. Res. 2014, 21, 571. (36) Pan, X.; Wang, Z.; Cao, Z.; Zhang, S.; He, Y.; Zhang, Y.; Chen, K.; Hu, Y.; Gu, H. A. Self-Powered Vibration Sensor based on Electrospun Poly(vinylidene fluoride) Nanofibres with Enhanced Piezoelectric Response. Smart Mater. Struct. 2016, 25, 105010. (37) Sorayani Bafqi, M. S.; Bagherzadeh, R.; Latifi, M. Nanofiber Alignment tuning: An Engineering Design Tool in Fabricating Wearable Power Harvesting Devices. J. Ind. Text. 2017, 47, 535−550. (38) Ghosh, S. K.; Biswas, A.; Sen, S.; Das, C.; Henkel, K.; Schmeisser, D.; Mandal, D. Yb3+ Assisted Self-polarized PVDF based Ferroelectretic Nanogenerator: A Facile Strategy of Highly Efficient Mechanical Energy Harvester Fabrication. Nano Energy 2016, 30, 621−629. (39) Sorayani Bafqi, M. S.; Bagherzadeh, R.; Latifi, M. Fabrication of Composite PVDF-ZnO Nanofiber Mats by Electrospinning for Energy Scavenging Application with Enhanced Efficiency. J. Polym. Res. 2015, 22, 130. (40) Maity, K.; Mahanty, B.; Sinha, T. K.; Garain, S.; Biswas, A.; Ghosh, S. K.; Manna, S.; Ray, S. K.; Mandal, D. Two-Dimensional Piezoelectric MoS2-Modulated Nanogenerator and Nanosensor Made of Poly(vinlydine Fluoride) Nanofiber Webs for Self-Powered Electronics and Robotics. Energy Technol. 2017, 5, 234−243. (41) Alam, M. M.; Ghosh, S. K.; Sarkar, D.; Sen, S.; Mandal, D. Improved Dielectric Constant and Breakdown Strength of γ-phase Dominant Super Toughened Polyvinylidene fluoride/TiO2 Nanocomposite Film: An Excellent Material for Energy Storage Applications and Piezoelectric Throughput. Nanotechnology 2017, 28, 015503. (42) Alam, M. M.; Sultana, A.; Sarkar, D.; Mandal, D. Electroactive β-crystalline Phase Inclusion and Photoluminescence Response of a Heat Controlled Spin-coated PVDF/TiO2 Free Standing Nanocomposite Film for a Nanogenerator and an Active Nanosensor. Nanotechnology 2017, 28, 365401. (43) Ico, G.; Showalter, A.; Bosze, W.; Gott, S. C.; Kim, B. S.; Rao, M. P.; Myung, N. V.; Nam, J. Size-Dependent Piezoelectric and Mechanical Properties of Electrospun P(VDF-TrFE) Nanofibers for Enhanced Energy Harvesting. J. Mater. Chem. A 2016, 4, 2293−2304. (44) Li, J.; Meng, Q.; Li, W.; Zhang, Z. Influence of Crystalline Properties on the Dielectric and Energy Storage Properties of Poly(vinylidene fluoride). J. Appl. Polym. Sci. 2011, 122, 1659−1668. (45) Yu, H.; Huang, T.; Lu, M.; Mao, M.; Zhang, Q.; Wang, H. Enhanced Power Output of an Electrospun PVDF/MWCNTs-based Nanogenerator by Tuning its Conductivity. Nanotechnology 2013, 24, 405401. (46) Ayutsede, J.; Gandhi, M.; Sukigara, S.; Micklus, M.; Chen, H. E.; Ko, F. Regeneration of Bombyxmori Silk by Electrospinning. Part 3: Characterization of Electrospun Nonwoven Mat. Polymer 2005, 46, 1625−1634. (47) Bazbouz, M. B.; Stylios, G. K. The Tensile Properties of Electrospun Nylon 6 Single Nanofibers. J. Polym. Sci., Part B: Polym. Phys. 2010, 48, 1719−1731. (48) Sarkar, S.; Garain, S.; Mandal, D.; Chattopadhyay, K. K. Electro-active Phase Formation in PVDF-BiVO4 Flexible Nano3111
DOI: 10.1021/acsaem.8b00216 ACS Appl. Energy Mater. 2018, 1, 3103−3112
Article
ACS Applied Energy Materials composite Films for High Energy Density Storage Application. RSC Adv. 2014, 4, 48220−737. (49) Kou, Y.; Chai, X.; Yu, R.; Liu, Y.; Wang, Z. Bio-Compatible BCTZ-based Piezoelectric Nanogenerator as Energy Harvester and Waterdrop Counter. Ceram. Int. 2017, 43, 6666−6670. (50) Alam, M. M.; Mandal, D. Native Cellulose Microfiber-Based Hybrid Piezoelectric Generator for Mechanical Energy Harvesting Utility. ACS Appl. Mater. Interfaces 2016, 8, 1555−1558. (51) Ylli, K.; Hoffmann, D.; Willmann, A.; Becker, P.; Folkmer, B.; Manoli, Y. Energy Harvesting from Human Motion: Exploiting Swing and Shock Excitations. Smart Mater. Struct. 2015, 24, 025029. (52) Lang, C.; Fang, J.; Shao, H.; Ding, X.; Lin, T. High-sensitivity Acoustic Sensors from Nanofiber Webs. Nat. Commun. 2016, 7, 11108. (53) Sultana, A.; Alam, M. M.; Biswas, A.; Middya, T. R.; Mandal, D. Fabrication of Wearable Semiconducting Piezoelectric Nanogenerator made with Electrospun-derived Zinc Sulphide Nanorods and Poly (vinyl alcohol) Nanofibers. Transl. Mater. Res. 2016, 3, 045001. (54) Yang, J.; Chen, J.; Liu, Y.; Yang, W.; Su, Y.; Wang, Z. L. Triboelectrification-Based Organic Film Nanogenerator for Acoustic Energy Harvesting and Self-Powered Active Acoustic Sensing. ACS Nano 2014, 8, 2649−2657. (55) Lang, C.; Fang, J.; Shao, H.; Wang, H.; Yan, G.; Ding, X.; Lin, T. High-output Acoustoelectric Power Generators from Poly(vinylidenefluoride-co-trifluoroethylene) Electrospun Nano-nonwovens. Nano Energy 2017, 35, 146−153. (56) Sultana, A.; Alam, M. M.; Sadhukhan, P.; Ghorai, U. K.; Das, S.; Middya, T. R.; Mandal, D. Organo-lead Halide Perovskite Regulated Green Light Emitting Poly (vinylidene fluoride) Electrospun Nanofiber Mat and its Potential Utility for Ambient Mechanical Energy Harvesting Application. Nano Energy 2018, 49, 380−392.
3112
DOI: 10.1021/acsaem.8b00216 ACS Appl. Energy Mater. 2018, 1, 3103−3112
