Ferroelectric Zinc Oxide Nanowire Embedded Flexible Sensor for

Subscriber access provided by UB + Fachbibliothek Chemie | (FU-Bibliothekssystem)

Letter

Ferroelectric Zinc Oxide Nanowire Embedded Flexible Sensor for Motion and Temperature Sensing Sungho Shin, DaeHoon Park, Joo-Yun Jung, Min Hyung Lee, and Junghyo Nah ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b00380 • Publication Date (Web): 09 Mar 2017 Downloaded from http://pubs.acs.org on March 9, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 15

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Ferroelectric Zinc Oxide Nanowire Embedded Flexible Sensor for Motion and Temperature Sensing Sung-Ho Shin1, Dae Hoon Park1, Joo-Yun Jung2, Min Hyung Lee3, Junghyo Nah1,* 1

Department of Electrical Engineering, Chungnam National University, Yuseong-Gu,

Daejeon 34134, Korea 2

Department of Nano Manufacturing Technology, Korea Institute of Machinery and

Materials, Yuseong-Gu, Daejeon 34103, Korea 3

Department of Applied Chemistry, Kyung Hee University, Yongin, Gyeonggi 17104, Korea

*Corresponding author: [email protected]

KEYWORDS: piezoelectric sensor, nanowires-polymer structure, flexible motion sensor, dynamic sensing, multifunction

1

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ABSTRACT We report a simple method to realize multifunctional flexible motion sensor using ferroelectric lithium-doped ZnO-PDMS. The ferroelectric layer enables piezoelectric dynamic sensing and provides additional motion information to more precisely discriminate different motions. The PEDOT:PSS-functionalized AgNWs, working as electrode layers for the piezoelectric sensing layer, resistively detect a change of both movement or temperature. Thus, through the optimal integration of both elements, the sensing limit, accuracy, and functionality can be further expanded. The method introduced here is a simple and effective route to realize high performance flexible motion sensor with integrated multifunctionalities.

2


Page 2 of 15

Page 3 of 15

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Different types of electronic sensors1,2 have been widely used for various applications in our lives, rapidly expanding the related market and industry. With recent advancement of sensor and flexible electronic technology, multifunctional flexible sensors3,4 that can perceive different external stimuli have been actively investigated and developed. Flexible motion sensors in particular have been of interest as they can be widely adopted for robotics,5,6 infrastructure monitoring7 and healthcare devices.8-9 Up to date, various types of flexible motion sensors have been developed, where many of them employ resistive network composed of conductive nanomaterials and polymers, such as metal-polymer, 10,11 carbon nanotubes (CNTs)-polymer,12,13 and AgNWs-polymer.14,15 These sensors can effectively sense different motions by monitoring resistance change originated from deformation of the sensing elements. Besides, these conductive polymer structures can provide resilience, durability, and flexibility, which are essential to flexible motion sensors. However, instantaneous dynamic movement cannot easily be sensed in this way if the speed or frequency of external stimuli exceeds the required recovery time of resistive sensing element 16 , 17 and thus only limited motion information can be obtained. In addition, if the motion does not entail direct physical deformation, such movement cannot be easily sensed as well. Therefore, a new method is necessary to overcome this limitation and expand the sensing capability. Besides, it is also necessary to propose a platform suitable for the integration of multiple functionalities on a single flexible device. Here we present a simple approach to fabricate multifunctional flexible sensor, which can to detect a change in movement and temperature. Specifically, the sensor consists of PEDOT:PSS-functionalized AgNW electrode embedded in the polymer layer and phase transformed ferroelectric Li-doped ZnO NWs-polymer composite layer. The functionalized AgNW layer resistively detects temperature and motions, which also function as electrode layers for piezoelectric output detection. The ferroelectric ZnO NWs-polymer composite layer 3



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 15

is employed to piezoeletrically sensing instantaneous dynamic motions. Through successful integration of both elements, different motions are more accurately distinguished and the sensing limit is further extended. Besides, fabricated device exhibits superb mechanical flexibility, durability, and stretchability, which is suited for various sensor applications.

The fabrication process of multifunctional flexible sensor is schematically illustrated in

Figure

1(a).

Briefly,

pre-cleaned

Si

wafer

was

treated

with

anti-adhesive

trichloro(1H,1H,2H,2H-perfluorooctyl) silane (FOTS), followed by silver nanowires (AgNWs) spray-coating and then PDMS spin-coating, respectively. The PDMS coveredAgNWs layer was transferred from the Si wafer.18,19 The details of fabrication process is described in experimental section [Supplementary Information]. The anti-adhesive layer coating is critical for fully transferring the AgNW layer from the Si wafer. We observed that the AgNW layer is only partially transferred from the Si wafer in the absence of FOTS layer [Supplementary information S1]. Figure 1(b) shows the SEM of the transferred AgNWs on the PDMS surface. Here, the role of conductive AgNWs is three-fold. First, AgNWs is a good resistive sensing element, due to high conductivity and mechanical stability.20 The AgNW network packed inside PDMS is deformed when the mechanical stress is applied to the device. Thus, the deformation of the electrode layer can be easily determined by measuring the resistance of the layer. Second, the AgNW layer works as a superb flexible electrode. Besides, temperature sensor can also be easily fabricated by functionalizing AgNW electrode with PEDOT:PSS.21 Using the prepared electrode layers, lithium (Li)-doped ZnO NWs-PDMS was sandwiched in between [Figure 1(c)]. Figure 1(d) shows the SEM of the uniformly mixed composite [Fig. 1(d) (inset) and Supplementary Information S2]. Figure 1(e) is a SEM of synthesized Li-doped ZnO NWs with an average length of ~20 µm and a diameter of ~700 nm. Compared with the photoluminescence (PL) of undoped ZnO NWs in 4


Page 5 of 15

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 1(f), relatively high yellow emission reveals substitutional Li (LiZn) and interstitial Li (Lii) in ZnO crystal structure22 [Figure 1(g)]. Figure 2(a)–(b) demonstrate principles of both resistive and piezoelectric sensing mechanism adopted for motion sensing. The strain (ε) of AgNW embedded electrode layer is ‘0’ when there are no external stimuli [Figure 2(a), left].

During bending and stretching

motions initiated by compressive and tensile force applied to the device, respectively, either partial or entire AgNW network is elongated, resulting in resistance increases [Figure 2(a), right]. Thus, the bending angle or stretch length can be determined by resistance change of the AgNW electrode layer. On the other hand, instantaneous motion sensing can be achieved by piezoelectric element sandwiched between the electrode layers where the polarized Lidoped ZnO NWs are packed inside PDMS between the two AgNW electrode layers. [Figure 2(b), left]. When the external force is applied to the device, bound charges will be released, generating piezoelectric voltage between the top and the bottom AgNW electrode layers23 [Figure 2(b), right]. As demonstrated in Figure 2(c), both resistances and piezoelectric output voltages were monitored as a function of time during bending and stretching motions at different speeds, using the device with a size of 1 cm × 5 cm. The resistances of AgNW electrode were increased to ~2000 % at the bending angle of 70° [Fig. 2(c), bottom left] and 2600 % at the stretch length of 3 mm [Fi. 2(c), bottom right]. We note that △R is a resistance change, defined as R-R0, where R0 is the resistance of AgNW layer at the initial state measured at room temperature and R is a resistance measured under applied force, respectively. At the same time, piezoelectric output voltages between the top and bottom AgNW electrodes were simultaneously measured while varying the motion speed. The results show that the output voltage increased from 0.97 V to 1.48 V as the bending speed increases from 65 mm/s to 75 mm/s [Fig. 2(c), top left]. Similarly, for stretch motions, the output 5



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

voltage is increased from 0.23 V to 0.47 V as the motion speed increases [Fig. 2(c), top right]. From these piezoelectric output voltages, relative speed can be estimated and the instantaneous motions can be more precisely determined. Besides, polarity of generated piezoelectric output signal was reversed when the bending direction is changed, revealing direction of motions [Figure 2(c)]. The results demonstrated here clearly indicate that the sensing capability can be extended by dynamic motion information obtained by piezoelectric element. Figure 3(a) and (b) show photographs of the bending machine, displaying different bending angles from 30° to 90° and stretching distances from 1 mm to 4 mm. The △R/R0 of top AgNW electrode under tensile stress is proportionally increased to ~2600 % as the bending angle gradually reaches 90° [Fig. 3(c), square]. The △R/R0 of the bottom electrode layer under compressive stress, on the other hand, was similar to the initial value even if the bending angle increases [Fig. 3(c), triangle]. Figure 3(d) shows the contour map of the piezoelectric output voltages at different bending speeds for each bending angle. As the bending angle and speed increase, the output voltages were increased from 0.8 V to 3.5 V. The detailed piezoelectric output data for each case are presented in Supplementary information S3.

In the case of stretching motion, the △R/R0 of both top and bottom AgNWs

electrode layer are increased up to ~3400 % as the stretch length reaches ~4 mm, while generating the piezoelectric output voltage up to 1.34 V at the maximum motion frequency [Fig. 3(e,f)]. Additionally, pushing motions normal to the device surface can also be determined. In this case, both △R/R0 of top and bottom AgNW electrodes are negligible as the NW network is not much affected in this mode [Fig. 3(g)]. This indicates the limitation of the resistive sensing method, requiring obvious shape deformation. However, piezoelectric output voltage is still generated and its amplitude is increased in proportion to applied force 6


Page 6 of 15

Page 7 of 15

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


and frequency, generating piezoelectric output voltages from 2.48 V at 0.05 MPa and 1 Hz to 6.7 V at 0.3 MPa and 5 Hz [Fig. 3(h)]. We note that piezoelectric sensing element is particularly useful for sensing relatively high frequency motions, sound wave, and stimuli entailing less shape deformation.24,25 Therefore, more precise sensing and differentiation of motions can be achieved by combining both resistive and piezoelectric sensing elements. In Figure 4, temperature sensing with PEDOT:PSS-functionalized AgNW electrode layers was investigated. The △R of PEDOT:PSS-coated AgNW electrode was decreased as the temperature is increased from 30 °C to 60 °C [Figure 4(a)]. This trend is originated from shrinkage of grain boundaries of PEDOT covered PSS structure. Also, no degradation was observed [Figure 4(b)] when the sensor was repeatedly exposed to temperature up to 60 °C over 103 cycles. In Figure 4(c)–(d), durability and reliability of AgNW electrode embedded in PDMS were also tested at the bending angle of 90° and a stretch length of 4 mm over 103 cycles, showing negligible performance degradation. In summary, we have developed a multifunctional flexible electronic sensor, which can function as motion and temperature sensor. PEDOT:PSS-functionalized AgNW electrode embedded in the polymer layer was employed to resistively monitor motion and temperature change. Based on this structure, the piezoelectric layer composed of Li-doped ZnO NWs and PDMS was integrated as a dynamic sensing element, providing additional motion information and enabling instantaneous motion detection. Through successful integration of both elements, sensing limit and accuracy was further extended. Besides, fabricated device exhibits superb mechanical flexibility, durability, and stretchability, which is suitable for various applications necessitating operation under harsh stress conditions.

7



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ASSOCIATED CONTENT The Supporting Information is available free of charge on the ACS Publications website at DOI: xx.xxxx/acsami.xxxxxxx. Schematic processes and SEMs of coated AgNWs; SEM of Li-doped ZnO NWs inside PDMS; Measured piezoelectric output voltages (PDF) AUTHOR INFORMATION Corresponding author *E-mail: [email protected] ORCID Author Contributions Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF-2015R1A1A1A05027235).

8


Page 8 of 15

Page 9 of 15

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure. 1 (a) Schematic illustration of the sensor fabrication process: composite layer, containing piezoelectric Li-doped ZnO NWs and PDMS, is sandwiched between two PEDOT:PSS-coated Ag NW electrodes embedded in the PDMS. (b) SEM of the AgNW network, which is seamlessly connected on the PDMS surface. The inset shows a magnified view of the Ag NWs on the PDMS. (c) Schematic representation of the sensor device consisting of two main parts: resistive and piezoelectric sensing elements. The inset shows the flexibility of device. (d) Cross-section of the device SEM (e) SEM of as-synthesized Lidoped ZnO NWs (f) PL spectra of undoped ZnO NWs and (g) Li-doped ZnO NWs. The yellow emission explicitly indicates the Li-doping in ZnO.

9



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure. 2 Principles of motion sensing. (a) Resistive sensing: the resistance of AgNW electrode layer changes with the elongation of AgNW network during bending and stretching motions. (b) Piezoelectric sensing: piezoelectric output signal is generated between the top and the bottom AgNW electrodes when the external force or stress is applied to the device as a result of instantaneous bending and stretching. Piezoelectric output voltage is generated due to polarized Li-doped ZnO NWs packed between the AgNW electrodes. (c) Piezoelectric (top) and resistive (bottom) output measurement for bending (70°) and stretching motions (3 mm) at different speeds. 10


Page 10 of 15

Page 11 of 15

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure. 3 Photographs of the measurement setup, displaying different (a) bending angles from 30° to 90° and (b) stretching distances from 1 mm to 4 mm. (c) △R/R0 of the top (red colored square) and bottom (blue colored triangles) Ag NW electrodes at different bending angle (d) The contour map displaying dynamic piezoelectric output voltages at different bending angles and speeds (e) △R/R0 of the top and the bottom Ag NW electrodes at different stretching lengths (f) Piezoelectric output voltages at different stretch lengths and speeds (g) △R/R0 of AgNW electrodes at different applied forces normal to the surface for motion sensing, showing negligible change. (h) Piezoelectric output voltages at different pressure and frequencies. 11



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure. 4 (a) Measured △R/R0 of PEDOT:PSS-functionalized AgNWs at different temperatures, showing a linear decrease with the increase of temperature (thermal sensitivity ~0.52 %/°C). (b) Cyclic thermal stability measurement repeated between 30 to 60 °C. (c-d) Cyclic bending (90°) and stretching (4 mm) measurement for mechanical durability and stability test. The results show negligible performance degradation over theses measurement.

12


Page 12 of 15

Page 13 of 15

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


REFERENCES

(1) Takei, K.; Takahashi, T.; Ho, J. C.; Ko, H.; Gillies, A. G.; Leu, P. W.; Fearing, P. W.; Javey, A. Nanowire Active-Matrix Circuitry for Low-Voltage Macroscale Artificial Skin. Nat. Mater. 2010, 9, 821–826. (2) Pang, C.; Lee, G.-Y.; Kim, T.-i.; Kim, S. M.; Kim, H. N.; Ahn, S.-H.; Suh, K.-Y. A Flexible and Highly Sensitive Strain-Gauge Sensor using Reversible Interlocking of Nanofibres. Nat. Mater. 2012, 11, 795–801. (3) Harada, S.; Honda, W.; Arie, T.; Akita, S.; Takei, K. Fully Printed, Highly Sensitive Multifunctional Artificial Electronic Whisker Arrays Integrated with Strain and Temperature Sensors. ACS Nano 2014, 8, 3921–3927. (4) M,

A.; RA, B.; RM, P.; M, D. Flexible Integrated Circuits and Multifunctional Electronics Based on Single Atomic Layers of MoS2 and Graphene. Nanotechnology 2015, 26, 115202.

(5) Song, Y. M.; Xie, Y.; Malyarchuk, V.; Xiao, J.; Jung, I.; Choi, K.-J.; Liu, Z.; Park, H.; Lu, C.; Kim, R.-H.; Li, Rui; Crozier, Kenneth B.; Huang, Y.; Rogers, John A. Digital Cameras with Designs Inspired by the Arthropod Eye. Nature 2013, 497, 95–99. (6) Misawa, N.; Mitsuno, H.; Kanzaki, R.; Takeuchi, S. Highly Sensitive and Selective Odorant Sensor using Living Cells Expressing Insect Olfactory Receptors. Proc. Natl. Acad. Sci. U.S.A. 2010, 107, 15340–15344. (7) Xiao, X.; Yuan, L.; Zhong, J.; Ding, T.; Liu, Y.; Cai, Z.; Rong, Y.; Han, H.; Zhou, J.; Wang, Z. L. High-Strain Sensors Based on ZnO Nanowire/Polystyrene Hybridized Flexible Films. Adv. Mater. 2011, 23, 5440–5444. (8) Hussain, A. M.; Lizardo, E. B.; Torres Sevilla, G. A.; Nassar, J. M.; Hussain, M. M. Ultrastretchable and Flexible Copper Interconnect-Based Smart Patch for Adaptive Thermotherapy. Adv. Healthcare Mater. 2015, 4, 665–673. (9) Yeo, W.-H.; Kim, Y.-S.; Lee, J.; Ameen, A.; Shi, L.; Li, M.; Wang, S.; Ma, R.; Jin, S. H.; Kang, Z.; Huang, Y.; Rogers. John A. Multifunctional Epidermal Electronics Printed Directly Onto the Skin. Adv. Mater. 2013, 25, 2773–2778. (10) Lacour, S. P.; Jones, J.; Wagner, S.; Li, T.; Suo, Z. Stretchable Interconnects for Elastic Electronic Surfaces. Proc. IEEE 2005, 93, 1459–1467. (11) Mattmann, C.; Clemens, F.; Tröster, G. Sensor for Measuring Strain in Textile. Sensors 2008, 8, 3719–3732. (12) Ryu, S.; Lee, P.; Chou, Jeffrey B.; Xu, R.; Zhao, R.; Hart, A. J.; Kim, S.-G. Extremely Elastic Wearable Carbon Nanotube Fiber Strain Sensor for Monitoring of Human Motion. 13



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano 2015, 9, 5929–5936. (13) Yamada, T.; Hayamizu, Y.; Yamamoto, Y.; Yomogida, Y.; Izadi-Najafabadi, A.; Futaba, D. N.; Hata, K. A Stretchable Carbon Nanotube Strain Sensor for Human-Motion Detection. Nat. Nanotechnol. 2011, 6, 296–301. (14) Amjadi, M.; Pichitpajongkit, A.; Lee, S.; Ryu, S.; Park, I. Highly Stretchable and Sensitive Strain Sensor Based on Silver Nanowire–Elastomer Nanocomposite. ACS Nano 2014, 8, 5154–5163. (15) Kim, K. K.; Hong, S.; Cho, H. M.; Lee, J.; Suh, Y. D.; Ham, J.; Ko, S. H. Highly Sensitive and Stretchable Multidimensional Strain Sensor with Prestrained Anisotropic Metal Nanowire Percolation Networks. Nano Lett. 2015, 15, 5240–5247. (16) Otto, J. K.; Brown, T. D.; Callaghan, J. J. Static and Dynamic Response of a Multiplexed-Array Piezoresistive Contact Sensor. Exp. Mech. 1999, 39, 317–323. (17) Pan, L.; Chortos, A.; Yu, G.; Wang, Y.; Isaacson, S.; Allen, R.; Shi, Y.; Dauskardt, R.; Bao, Z. An Ultra-Sensitive Resistive Pressure Sensor Based on Hollow-Sphere Microstructure Induced Elasticity in Conducting Polymer Film. Nat. Commun. 2014, 5, 3002. (18) Shin, S.-H.; Kwon, Y. H.; Kim, Y.-H.; Jung, J.-Y.; Lee, M. H.; Nah, J. Triboelectric Charging Sequence Induced by Surface Functionalization as a Method To Fabricate High Performance Triboelectric Generators. ACS Nano 2015, 9, 4621–4627. (19) Zhuang, Y. X.; Hansen, O.; Knieling, T.; Wang, C.; Rombach, P.; Lang, W.; Benecke, W.; Kehlenbeck, M.; Koblitz, J. Vapor Phase Self-Assembled Monolayers for Anti-stiction Applications in MEMS. J. Microelectromech. Syst. 2007, 16, 1451–1460. (20) Lee, J.; Lee, P.; Lee, H.; Lee, D.; Lee, S. S.; Ko, S. H. Very Long Ag Nanowire Synthesis and Its Application in a Highly Transparent, Conductive and Flexible Metal Electrode Touch Panel. Nanoscale 2012, 4, 6408–6414. (21) Vuorinen, T.; Niittynen, J.; Kankkunen, T.; Kraft, Thomas M.; Mäntysalo, M. InkjetPrinted Graphene/PEDOT:PSS Temperature Sensors on a Skin-Conformable Polyurethane Substrate. Sci. Rep. 2016, 6, 35289. (22) McCluskey, M. D.; Jokela, S. J. Defects in ZnO. J. Appl. Phys. 2009, 106, 071101. (23) Shin, S.-H.; Kim, Y.-H.; Lee, M. H.; Jung, J.-Y.; Seol, J. H.; Nah, J. Lithium-Doped Zinc Oxide Nanowires–Polymer Composite for High Performance Flexible Piezoelectric Nanogenerator. ACS Nano 2014, 8, 10844–10850. (24) Yu, P.; Liu, W.; Gu, C.; Cheng, X.; Fu, X. Flexible Piezoelectric Tactile Sensor Array for Dynamic Three-Axis Force Measurement. Sensors 2016, 16, 819. 14


Page 14 of 15

Page 15 of 15

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(25) Cha, S.; Kim, S. M.; Kim, H.; Ku, J.; Sohn, J. I.; Park, Y. J.; Song, B. G.; Jung, M. H.; Lee, E. K.; Choi, B. L.; Park, J. J.; Wang, Z. L.; Kim, J. M.; Kim, K. Porous PVDF As Effective Sonic Wave Driven Nanogenerators. Nano Lett. 2011, 11, 5142–5147.

Figure for Table of Contents

15


Ferroelectric Zinc Oxide Nanowire Embedded Flexible Sensor for

Recommend Documents