- Open Access
Stretchable piezoelectric nanocomposite generator
© The Author(s) 2016
Received: 17 March 2016
Accepted: 12 April 2016
Published: 3 June 2016
Piezoelectric energy conversion that generate electric energy from ambient mechanical and vibrational movements is promising energy harvesting technology because it can use more accessible energy resources than other renewable natural energy. In particular, flexible and stretchable piezoelectric energy harvesters which can harvest the tiny biomechanical motions inside human body into electricity properly facilitate not only the self-powered energy system for flexible and wearable electronics but also sensitive piezoelectric sensors for motion detectors and in vivo diagnosis kits. Since the piezoelectric ZnO nanowires (NWs)-based energy harvesters (nanogenerators) were proposed in 2006, many researchers have attempted the nanogenerator by using the various fabrication process such as nanowire growth, electrospinning, and transfer techniques with piezoelectric materials including polyvinylidene fluoride (PVDF) polymer and perovskite ceramics. In 2012, the composite-based nanogenerators were developed using simple, low-cost, and scalable methods to overcome the significant issues with previously-reported energy harvester, such as insufficient output performance and size limitation. This review paper provides a brief overview of flexible and stretchable piezoelectric nanocomposite generator for realizing the self-powered energy system with development history, power performance, and applications.
Attractive approaches based on energy harvesting technology that convert ambient energy resources such as thermal, solar and mechanical energies into electrical energy have been recently studied to realize the demonstration of self-powered energy system in portable devices without external power sources like batteries [1–4]. Among these sustainable energy resources, the mechanical energy is easily accessible compared to outdoor renewable energy in anytime and anywhere (even inside human body) of our daily [5–8]. To convert the mechanical energy resources (e.g., pressure, bending, stretching and vibrational motions) to electricity, the piezoelectric energy conversion are proposed and investigated by many research groups [3, 9, 10]. In particular, the flexible energy harvester called a nanogenerator which can generate electrical energy from not only mechanical energy but also tiny biomechanical energy (e.g., heartbeat, muscle motions, and eye blinking) have attracted attention in response to the demands of infinite self-powered sources for operating flexible and wearable electronic systems .
Because polymer materials have the naturally flexible properties and mechanical stabilities, the piezoelectric polymers as polyvinylidene fluoride (PVDF) have been used to fabricate polymeric flexible nanogenerators (Fig. 1b) [16–18]. Figure 1b-i presents the piezoelectric PVDF nanofibers placed on a working substrate using a unique direct-write technique. The PVDF based nanogenerator generates electrical outputs of about 5–30 mV and 0.5–3 nA when the substrate is deformed by stretching and releasing motions [16, 17]. Cha et al.  proposed the polymeric nanogenerator made of porous PVDF by employing a novel template-assisted method (Fig. 1b-ii). This sonic wave driven energy harvester produces higher output performance compared to dense PVDF based nanogenerators due to the effective nanoporous structure.
In 2010, there have been new approaches to use perovskite-structured ceramic [PbZrxTi1−xO3 (PZT) and BaTiO3] thin films with inherently high piezoelectricity for higher energy conversion efficiency (Fig. 1c) [19–22]. The PZT and BaTiO3 thin films on bulk substrate are transferred onto flexible PI substrates by adopting unique transferring techniques after high temperature crystallization process (Fig. 1c-i, ii). The perovskite thin film-based nanogenerators show higher power density compared with other flexible piezoelectric devices with the similar device structure. Qi et al.  presented the energy harvester of wavy piezoelectric PZT ribbons, that can scavenge stretching motions to generate.
Recently, the research on large-area, low-cost, mechanically-stable, and high-output nanocomposite generator has been invented by using simply casting piezoelectric nanocomposites onto flexible plastic substrates at low temperature (Fig. 1d) [23–27]. In particular, several research groups have developed lead-free and high-performance flexible energy harvesters using bio-eco-compatible piezoelectric ceramics such as BaTiO3 , (K, Na)NbO3 [24, 25], and Li-doped (K, Na)NbO3 . Subsequently, a new concept of ultra-stretchable elastic-composite generator, was also developed by employing the Ecoflex silicone rubber-based piezoelectric composites and long silver nanowire-based stretchable electrodes . This review paper highlights a brief overview of flexible and stretchable piezoelectric nanocomposite generator for realizing the self-powered energy system, summarizing development history, power performance, and energy applications. These technologies provide novel solutions to overcome the challenging issues about nanogenerators, such as insufficient output signals and size limitation for the power sources of commercial electronics.
2.1 BaTiO3 nanoparticles-based flexible nanocomposite generator
2.2 NCG device based on various piezoelectric particles
Since the first demonstration of BaTiO3 NPs-based NCG device, many research groups proposed other type of composite-based nanogenerators composed of various piezoelectric materials such as ZnO, PZT, and alkaline niobate particles using the NCG technique [26, 27, 29], due to the advantage of highly-efficient and large-area energy harvesters with simple and low-cost process. By using ZnO NPs of the higher piezoelectric performance compared to ZnO nanowire, the novel flexible nanogenerator composed of ZnO NPs and multiwall-carbon nanotubes (MW-CNTs) was demonstrated, as shown in Fig. 3b . The energy harvester generated output voltage of 0.4 V and current pulse of 50 nA during the repeat finger gestures with the frequency of 1 Hz. The voltage and current signals reached up to the 7.5 V and 2.5 μA, respectively, under hammer knocking on the energy device. The inherently excellent piezoelectric PZT particles were also adopted to fabricate NCG device (Fig. 3c) . The NCG device with PZT particles and multiwall (MW)-CNTs showed the distinguishable improvement in output performance of NCG device (3 × 3 cm2): the converted output voltage and current signals are ~10 V and 1.3 μA, respectively. Although this nanogenerator provided the methodology for high-output flexible energy harvesting device, PZT-based device has critical environmental drawbacks due to Pb-related problems. One of the most attractive lead-free piezoelectric materials is alkaline niobate which provides similar piezoelectric properties compared to PZT material. Jeong et al.  constructed the lead-free NCG device made of outstanding piezoelectric and bio-ecofriendly (K,Na)NbO3-LiNbO3 (KNLN) nanoparticles and well-dispersible copper nanorods (NRs) fillers (Fig. 3d). The KNLN-based NCG device not only creates high output with 12 V and 1.2 μA but also shows excellent stability and durability without any degeneration under the repeated bending cycles. By employing the bar-coating method, a large-area NCG device of 30 × 30 cm2 was demonstrated, as shown in Fig. 3e . A large-scale NCG device harvested high output signals, output voltage of ~100 V and current of ~10 μA.
2.3 Piezoelectric nanowire/tubes-based NCG device
2.4 NCG device by adopting unusual structure and Bioinspired approach
2.5 Hyper-stretchable composite energy harvester
2.6 Energy applications by flexible and stretchable NCG devices
The developments of flexible and stretchable energy harvesting device through piezoelectric materials-polymer composites have enabled the self-powered energy system with high performance and improved mechanical stability. Simple and low-cost fabrication processes such as spin-casing, die-casting, and bar-coating allow the large-area energy harvester. First, the typical piezoelectric nanomaterial (e.g., BaTiO3 NPs) was utilized to form the piezoelectric composites; subsequently, the inherently excellent piezoelectric PZT material-based high-output NCG device were developed. Recently, the many researchers have investigated the new approaches for employing the alkaline niobate-based high piezoelectric ceramics and unusual structured BaTiO3 due to additional motivations for environment-friendly and biocompatible energy harvesters. Moreover, the ultra-stretchable NCG device were demonstrated via hyper-stretchable electrodes of Ag NWs percolation network in response to the demand of energy harvesting devices closely in contact with the curvy surfaces. The fabricated NCG device can produce the power from biomechanical movements and sufficiently operate the commercial electronic devices. The NCG technology will be expected to improve further by adopting the controllable lead-free piezoelectric ceramic materials [such as Ba(Zr,Ti)O3 (BZT), (Bi, Nd)Ti3O12, and SrBi2Ta2O9] and the enhaced core–shell structured nanomaterials. Furthermore, the novel printing technique with p-NC will open a key role in the development of the commercially available self-powered energy system. The piezoelectric rubbers will facilitate solutions to develop the self-powered road-system consisting of energy generation source, highly-sensitive sensor, and wireless transmitter for military and wearable applications. In addition, these unique approaches for flexible energy harvesters shall support energy sources of various state-of-a-art flexible and future electronic systems [37–56].
KIP and CKJ wrote the manuscript and KJL guided manuscript preparation. All authors read and approved the final manuscript.
Prof. Kwi-Il Park is currently assistant professor in the Department of Energy Engineering at Gyeongnam National University of Science and Technology (GNTECH). Prof. Park received his Ph.D. in Materials Science and Engineering (MSE) at Korea Advanced Institute of Science and Technology (KAIST). During his Ph. D. at KAIST, he studied flexible energy harvesting technology using inorganic-based piezoelectric materials by. He was previously a senior researcher at Agency for Defense Development from 2014 to 2015. His research interests include the synthesis of high performance piezoelectric nanomaterials and development of flexible/stretchable energy harvester based on inorganic piezo-materials.
Dr. Chang Kyu Jeong received his Ph.D. degree in Materials Science and Engineering from KAIST in 2016 and B.S. degree from Hanyang University in 2011. He is currently working as a research fellow in KAIST Institute for the NanoCentury (KINC). His research topics focus on mechanical energy harvesting, soft/biomaterials, surface chemistry, and nanomaterial syntheses.
Prof. Keon Jae Lee received his Ph.D. in Materials Science and Engineering (MSE) at University of Illinois, Urbana-Champaign (UIUC). During his Ph.D. at UIUC, he involved in the first co-invention of “Flexible Single-crystalline Inorganic Electronics”, using top-down semiconductors and soft lithographic transfer. Since 2009, he has been a professor in MSE at KAIST. His current research topics are self-powered flexible electronic systems including energy harvesting/storage devices, LEDs, large-scale integration (LSI), high-density memory and laser material interaction for in vivo biomedical and flexible applications.
This work was supported by Gyeongnam National University of Science and Technology (GNTECH) Grant 2015. This study was also supported by Global Frontier R&D Program on Center for Integrated Smart Sensors (Grant No. CISS-2012M3A6A6054193)
The authors declare that they have no competing interests.
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- G.J. Aubrecht, Energy: physical, environmental, and social impact (Pearson Education, London, 2006)Google Scholar
- I.R. Henderson, Piezoelectric ceramics: principles and applications (APC International Ltd, Pennsylvania, 2002)Google Scholar
- S. Priya, D.J. Inman, Energy Harvesting Technologies (Springer Science, New York, 2009)View ArticleGoogle Scholar
- Z.L. Wang, Nanogenerators for self-powered devices and systems (Georgia Institute of Technology, Atlanta, 2011)Google Scholar
- C.R. Bowen, H.A. Kim, P.M. Weaver, S. Dunn, Piezoelectric and ferroelectric materials and structures for energy harvesting applications. Energ. Environ. Sci. 7, 25–44 (2014)View ArticleGoogle Scholar
- J. Briscoe, S. Dunn, Piezoelectric nanogenerators—a review of nanostructured piezoelectric energy harvesters. Nano. Energ. 14, 15–29 (2015)View ArticleGoogle Scholar
- X. Wang, Piezoelectricnanogenerators-harvesting ambient mechanical energy at the nanometer scale. Nano. Energ. 1(1), 13–24 (2012)View ArticleGoogle Scholar
- Z.L. Wang, W. Wu, Nanotechnology-enabled energy harvesting for self-powered micro-/nanosystems. Angew. Chem. Int. Ed. 51(47), 11700–11721 (2012)View ArticleGoogle Scholar
- S.P. Beeby, M.J. Tudor, N.M. White, Energy harvesting vibration sources for microsystems applications. Meas. Sci. Technol. 17(12), R175 (2006)View ArticleGoogle Scholar
- Z.Y. Wang, J. Hu, A.P. Suryavanshi, K. Yum, M.F. Yu, Voltage generation from individual BaTiO3 nanowires under periodic tensile mechanical load. Nano. Lett. 7(10), 2966–2969 (2007)View ArticleGoogle Scholar
- X.D. Wang, J.H. Song, J. Liu, Z.L. Wang, Direct-current nanogenerator driven by ultrasonic waves. Science. 316(5821), 102–105 (2007)View ArticleGoogle Scholar
- R. Yang, Y. Qin, C. Li, G. Zhu, Z.L. Wang, Converting biomechanical energy into electricity by a muscle-movement-driven nanogenerator. Nano. Lett. 9(3), 1201–1205 (2009)View ArticleGoogle Scholar
- R.S. Yang, Y. Qin, L.M. Dai, Z.L. Wang, Power generation with laterally packaged piezoelectric fine wires. Nat. Nanotechnol. 4(1), 34–39 (2009)View ArticleGoogle Scholar
- G. Zhu, R. Yang, S. Wang, Z.L. Wang, Flexible high-output nanogenerator based on lateral ZnO nanowire array. Nano. Lett. 10(8), 3151–3155 (2010)View ArticleGoogle Scholar
- M.Y. Choi, D. Choi, M.J. Jin, I. Kim, S.H. Kim, J.Y. Choi, S.Y. Lee, J.M. Kim, S.W. Kim, Mechanically powered transparent flexible charge-generating nanodevices with piezoelectric ZnO nanorods. Adv. Mater. 21(21), 2185–2189 (2009)View ArticleGoogle Scholar
- C.E. Chang, V.H. Tran, J.B. Wang, Y.K. Fuh, L.W. Lin, Direct-write piezoelectric polymeric nanogenerator with high energy conversion efficiency. Nano. Lett. 10(2), 726–731 (2010)View ArticleGoogle Scholar
- C.E. Chang, Y-K Fuh, L. Lin, in A direct-write piezoelectric PVDF nanogenerator, transducers 2009, solid-state sensors, actuators and microsystems conference, (Denver, 2009) p. 1485–1488Google Scholar
- S.N. Cha, S.M. Kim, H. Kim, J. Ku, J.I. Sohn, Y.J. Park, B.G. Song, M.H. Jung, E.K. Lee, B.L. Choi, J.J. Park, Z.L. Wang, J.M. Kim, K. Kim, Porous PVDF as effective sonic wave driven nanogenerators. Nano. Lett. 11(12), 5142–5147 (2011)View ArticleGoogle Scholar
- K.-I. Park, S. Xu, Y. Liu, G.T. Hwang, S.J.L. Kang, Z.L. Wang, K.J. Lee, Piezoelectric BaTiO3 thin film nanogenerator on plastic substrates. Nano. Lett. 10(12), 4939–4943 (2010)View ArticleGoogle Scholar
- Y. Qi, N.T. Jafferis, K. Lyons, C.M. Lee, H. Ahmad, M.C. McAlpine, Piezoelectric ribbons printed onto rubber for flexible energy conversion. Nano. Lett. 10(2), 524–528 (2010)View ArticleGoogle Scholar
- Y. Qi, J. Kim, T.D. Nguyen, B. Lisko, P.K. Purohit, M.C. McAlpine, Enhanced piezoelectricity and stretchability in energy harvesting devices fabricated from buckled PZT ribbons. Nano. Lett. 11(3), 1331–1336 (2011)View ArticleGoogle Scholar
- Y. Qi, M.C. McAlpine, Nanotechnology-enabled flexible and biocompatible energy harvesting. Energ. Environ. Sci. 3(9), 1275–1285 (2010)View ArticleGoogle Scholar
- K.-I. Park, M. Lee, Y. Liu, S. Moon, G.T. Hwang, G. Zhu, J.E. Kim, S.O. Kim, D.K. Kim, Z.L. Wang, K.J. Lee, Flexible nanocomposite generator made of BaTiO3 nanoparticles and graphitic carbons. Adv. Mater. 24(22), 2999–3004 (2012). (Front Cover Article) View ArticleGoogle Scholar
- J.H. Jung, M. Lee, J.I. Hong, Y. Ding, C.Y. Chen, L.J. Chou, Z.L. Wang, Lead-free NaNbO3 nanowires for a high output piezoelectric nanogenerator. ACS. Nano. 5(12), 10041–10046 (2011)View ArticleGoogle Scholar
- J.H. Jung, C.Y. Chen, B.K. Yun, N. Lee, Y. Zhou, W. Jo, L.J. Chou, Z.L. Wang, Lead-free KNbO3 ferroelectric nanorod based flexible nanogenerators and capacitors. Nanotechnology. 23(37), 375401 (2012)View ArticleGoogle Scholar
- K.-I. Park, C.K. Jeong, J. Ryu, G.-T. Hwang, K.J. Lee, Flexible and large-area nanocomposite generators based on lead zirconate titanate particles and carbon nanotubes. Adv. Energ. Mater. 3(12), 1539–1544 (2013)View ArticleGoogle Scholar
- C.K. Jeong, K.-I. Park, J. Ryu, G.-T. Hwang, K.J. Lee, Large-area and flexible lead-free nanocomposite generator using alkaline niobate particles and metal nanorod filler. Adv. Funct. Mater. 24(18), 2620–2629 (2014)View ArticleGoogle Scholar
- C.K. Jeong, J. Lee, S. Han, J. Ryu, G.-T. Hwang, D.Y. Park, J.H. Park, S.S. Lee, M. Byun, S.H. Ko, K.J. Lee, A hyper-stretchable elastic-composite energy harvester. Adv. Mater. 27(18), 2866–2875 (2015)View ArticleGoogle Scholar
- H. Sun, H. Tian, Y. Yang, D. Xie, Y.C. Zhang, X. Liu, S. Ma, H.M. Zhao, T.L. Ren, A novel flexible nanogenerator made of ZnO nanoparticles and multiwall carbon nanotube. Nanoscale. 5(13), 6117–6123 (2013)View ArticleGoogle Scholar
- Z.H. Lin, Y. Yang, J.M. Wu, Y. Liu, F. Zhang, Z.L. Wang, BaTiO3 nanotubes-based flexible and transparent nanogenerators. J. Phys. Chem. Lett. 3(23), 3599–3604 (2012)View ArticleGoogle Scholar
- K.-I. Park, S.B. Bae, S.H. Yang, H.I. Lee, K. Lee, S.J. Lee, Lead-free BaTiO3 nanowires-based flexible nanocomposite generator. Nanoscale. 6(15), 8962–8968 (2014)View ArticleGoogle Scholar
- S.H. Shin, Y.H. Kim, M.H. Lee, J.Y. Jung, J. Nah, Hemispherically aggregated BaTiO3 nanoparticle composite thin film for high-performance flexible piezoelectric nanogenerator. ACS. Nano. 8(3), 2766–2773 (2014)View ArticleGoogle Scholar
- J. Chun, N.-R. Kang, J.-Y. Kim, M.-S. Noh, C.-Y. Kang, D. Choi, S.W. Kaim, Z.L. Wang, J.M. Baik, Highly anisotropic power generation in piezoelectric hemispheres composed stretchable composite film for self-powered motion sensor. Nano. Energ. 11(1), 1–10 (2015)View ArticleGoogle Scholar
- C.K. Jeong, I. Kim, K.-I. Park, M.H. Oh, H. Paik, G.T. Hwang, K. No, Y.S. Nam, K.J. Lee, Virus-directed design of a flexible BaTiO3 nanogenerator. ACS. Nano. 7(12), 11016–11025 (2013)View ArticleGoogle Scholar
- P. Lee, J. Lee, H. Lee, J. Yeo, S. Hong, K.H. Nam, D. Lee, S.S. Lee, S.H. Ko, Highly stretchable and highly conductive metal electrode by very long metal nanowire percolation network. Adv. Mater. 24(25), 3326–3332 (2012)View ArticleGoogle Scholar
- L. Gu, N. Cui, L. Cheng, Q. Xu, S. Bai, M. Yuan, W. Wu, J. Liu, Y. Zhao, F. Ma, Y. Qin, Z.L. Wang, Flexible fiber nanogenerator with 209 V output voltage directly powers a light-emitting diode. Nano. Lett. 13(1), 91–94 (2013)View ArticleGoogle Scholar
- S.Y. Lee, K.-I. Park, C. Huh, M. Koo, H.G. Yoo, S. Kim, C.S. Ah, G.Y. Sung, K.J. Lee, Water-resistant flexible GaN LED on a liquid crystal polymer substrate for implantable biomedical applications. Nano. Energ. 1, 145–151 (2012)View ArticleGoogle Scholar
- S. Kim, H.Y. Jeong, S.K. Kim, S.-Y. Choi, K.J. Lee, Flexible memristive memory array on plastic substrates. Nano. Lett. 11(12), 5438–5442 (2011)View ArticleGoogle Scholar
- M. Koo, K.-I. Park, S.H. Lee, M. Suh, D.Y. Jeon, J.W. Choi, K. Kang, K.J. Lee, Bendable inorganic thin-film battery for fully flexible electronic systems. Nano. Lett. 12(9), 4810–4816 (2012)View ArticleGoogle Scholar
- W.I. Park, B.K. You, B.H. Mun, H.K. Seo, J.Y. Lee, S. Hosaka, Y. Yin, C.A. Ross, K.J. Lee, Y.S. Jung, Self-assembled incorporation of modulated block copolymer nanostructures in phase-change memory for switching power reduction. ACS. Nano. 7(3), 2651–2658 (2013)View ArticleGoogle Scholar
- G.-T. Hwang, D. Im, S.E. Lee, J. Lee, M. Koo, S.Y. Park, S. Kim, K. Yang, S.J. Kim, K. Lee, K.J. Lee, In vivo silicon-based flexible radio frequency integrated circuits monolithically encapsulated with biocompatible liquid crystal polymers. ACS. Nano. 7(5), 4545–4553 (2013)View ArticleGoogle Scholar
- K.-I. Park, J.H. Son, G.-T. Hwang, C.K. Jeong, J. Ryu, M. Koo, I. Choi, S.H. Lee, M. Byun, Z.L. Wang, K.J. Lee, Highly-efficient, flexible piezoelectric PZT thin film nanogenerator on plastic substrates. Adv. Mater. 26(16), 2514–2520 (2014)View ArticleGoogle Scholar
- G.-T. Hwang, H. Park, J.-H. Lee, K.-I. Park, M. Byun, H. Park, G. Ahn, C.K. Jeong, K. No, H. Kwon, S.-G. Lee, B. Joung, K.J. Lee, Self-powered cardiac pacemaker enabled by flexible single crystalline PMN-PT piezoelectric energy harvester. Adv. Mater. 26(28), 4880–4887 (2014)View ArticleGoogle Scholar
- I. Choi, H.Y. Jeong, D.Y. Jung, M. Byun, C.-G. Choi, B.H. Hong, S.-Y. Choi, K.J. Lee, Laser-induced solid-phase doped graphene. ACS. Nano. 8(8), 7671–7677 (2014)View ArticleGoogle Scholar
- C.K. Jeong, K.-I. Park, J.H. Son, G.-T. Hwang, S.H. Lee, D.Y. Park, H.E. Lee, H.K. Lee, M. Byun, K.J. Lee, Self-powered fully-flexible light-emitting system enabled by flexible energy harvester. Energ. Environ. Sci. 7(12), 4035–4043 (2014)View ArticleGoogle Scholar
- H.S. Lee, J. Chung, G.-T. Hwang, C.K. Jeong, Y. Jung, J.-H. Kwak, H. Kang, M. Byun, W.D. Kim, S. Hur, S.-H. Oh, K.J. Lee, Flexible inorganic piezoelectric acoustic nanosensors for biomimetic artifi cial hair cells. Adv. Funct. Mater. 24(44), 6914–6921 (2014)View ArticleGoogle Scholar
- S. Kim, J.H. Son, S.H. Lee, B.K. You, K.-I. Park, H.K. Lee, M. Byun, K.J. Lee, Flexible crossbar-structured resistive memory arrays on plastic substrates via inorganic-based laser Lift-Off. Adv. Mater. 26(44), 7480–7487 (2014)View ArticleGoogle Scholar
- B.K. You, W.I. Park, J.M. Kim, K.-I. Park, H.K. Seo, J.Y. Lee, Y.S. Jung, K.J. Lee, Reliable control of filament formation in resistive memories by self-assembled nanoinsulators derived from a block copolymer. ACS. Nano. 8(9), 9492–9502 (2014)View ArticleGoogle Scholar
- C.K. Jeong, K.M. Baek, S. Niu, T.W. Nam, Y.H. Hur, D.Y. Park, G.-T. Hwang, M. Byun, Z.L. Wang, Y.S. Jung, K.J. Lee, Topographically-designed triboelectric nanogenerator via block copolymer self-assembly. Nano. Lett. 14(12), 7031–7038 (2014)View ArticleGoogle Scholar
- S.H. Lee, C.K. Jeong, G.-T. Hwang, K.J. Lee, Self-powered flexible inorganic electronic system. Nano. Energ. 14, 111–125 (2015)View ArticleGoogle Scholar
- G.-T. Hwang, J. Yang, S.H. Yang, H.-Y. Lee, M. Lee, D.Y. Park, J.H. Han, S.J. Lee, C.K. Jeong, J. Kim, K.-I. Park, K.J. Lee, A reconfigurable rectifi ed flexible energy harvester via solid-state single crystal grown PMN–PZT. Adv. Energ. Mater. 5(10), 1500051 (2015)View ArticleGoogle Scholar
- B.H. Mun, B.K. You, S.R. Yang, H.G. Yoo, J.M. Kim, W.I. Park, Y. Yin, M. Byun, Y.S. Jung, K.J. Lee, Flexible one diode-one phase change memory array enabled by block copolymer self-assembly. ACS. Nano. 9(4), 4120–4128 (2015)View ArticleGoogle Scholar
- H.G. Yoo, M. Byun, C.K. Jeong, K.J. Lee, Performance enhancement of electronic and energy devices via block copolymer self-assembly. Adv. Mater. 27(27), 3982–3998 (2015)View ArticleGoogle Scholar
- B.K. You, M. Byun, S. Kim, K.J. Lee, Self-structured conductive filament nanoheater for chalcogenide phase transition. ACS. Nano. 9(6), 6587–6594 (2015)View ArticleGoogle Scholar
- G.-T. Hwang, Y. Kim, J.-H. Lee, S. Oh, C.K. Jeong, D.Y. Park, J. Ryu, H. Kwon, S.-G. Lee, B. Joung, D. Kim, K.J. Lee, Self-powered deep brain stimulation via a flexible PIMNT energy harvester. Energ. Environ. Sci. 8(9), 2677–2684 (2015)View ArticleGoogle Scholar
- A.H. Park, S.H. Lee, C. Lee, J. Kim, H.E. Lee, S.-B. Paik, K.J. Lee, D. Kim, Optogenetic mapping of functional connectivity in freely moving mice via insertable wrapping electrode array beneath the skull. ACS. Nano. 10(2), 2791–2802 (2016)View ArticleGoogle Scholar