- Open Access
Deformable devices with integrated functional nanomaterials for wearable electronics
- Jaemin Kim†1, 2,
- Jongsu Lee†1, 2,
- Donghee Son1, 2,
- Moon Kee Choi1, 2 and
- Dae-Hyeong Kim1, 2Email author
© Kim et al. 2016
- Received: 6 August 2015
- Accepted: 4 November 2015
- Published: 15 March 2016
As the market and related industry for wearable electronics dramatically expands, there are continuous and strong demands for flexible and stretchable devices to be seamlessly integrated with soft and curvilinear human skin or clothes. However, the mechanical mismatch between the rigid conventional electronics and the soft human body causes many problems. Therefore, various prospective nanomaterials that possess a much lower flexural rigidity than their bulk counterparts have rapidly established themselves as promising electronic materials replacing rigid silicon and/or compound semiconductors in next-generation wearable devices. Many hybrid structures of multiple nanomaterials have been also developed to pursue both high performance and multifunctionality. Here, we provide an overview of state-of-the-art wearable devices based on one- or two-dimensional nanomaterials (e.g., carbon nanotubes, graphene, single-crystal silicon and oxide nanomembranes, organic nanomaterials and their hybrids) in combination with zero-dimensional functional nanomaterials (e.g., metal/oxide nanoparticles and quantum dots). Starting from an introduction of materials strategies, we describe device designs and the roles of individual ones in integrated systems. Detailed application examples of wearable sensors/actuators, memories, energy devices, and displays are also presented.
- Silicon nanomembrane
- Functional nanomaterials
- Flexible electronics
- Stretchable electronics
- Wearable electronics
In the rapid technology development of low-power silicon electronics, light-emitting diodes (LEDs) fabricated on unconventionally shaped substrates, high-capacity lithium-ion batteries, and various wearable electronic devices such as smart glasses, watches, and lenses have been unveiled both in academic journals and on the market. In spite of their superb performance, wearable form factors, and compact sizes, challenges remain mainly owing to their large thickness and mechanical rigidity, which result in a mechanical mismatch between the device and the skin, and thereby discomfort, a low signal-to-noise ratio, and measurement errors . In this regard, achieving mechanical deformability of the wearable electronic/optoelectronic devices while maintaining high performances has been a major research goal [2–6].
One promising strategy is to replace the rigid electronic materials (e.g., silicon wafer) with flexible nanomaterials (e.g., silicon nanomembrane (SiNM) [7–11], carbon nanotubes (CNTs) [12–14], graphene (GP) [1, 15, 16], and organic nanomaterials [17, 18]). The electronic properties of the SiNM (down to tens of nanometers) remain the same as the bulk silicon wafer , but its bendability dramatically increases owing to the reduced thickness . SiNM-based devices outperform their competitors including low-temperature polycrystalline silicon (LTPS) and organic devices by virtue of their high electron mobility . However, SiNM based device might have issues in the high cost and complicated fabrication processes. Meanwhile, carbon nanomaterials (e.g., CNTs and GP) [21, 22] have been getting attentions as next-generation semiconducting nanomaterials. The mobility of single-walled CNTs (SWNTs) and exfoliated GP have been reported up to 100,000  and 230,000 cm2 V−1 s−1 , respectively, which are higher than that of single-crystal silicon. Their ultrathin thickness enables them to be seamlessly integrated in wearable devices while achieving the transparency [23–25]. The mass production, device performance, and fabrication processes of these carbon nanomaterials, however, have many remaining challenges for commercial device applications . Organic nanomaterials such as organic nanowires/nanofibers also have recently utilized as electric materials for fabricating complementary metal–oxide–semiconductor (CMOS) circuits  and wearable power generators [28, 29]. Intrinsic deformability of organic nanomaterials, solution processability, and low cost make them promising for wearable devices . However, their low electrical performances should be resolved for its widespread applications .
2.1 Wearable sensors/actuators
Wearable sensors/actuators have recently attracted considerable interest because of their mobile healthcare  and virtual reality applications . Sensors/actuators worn on the body, in particular, have drawn attention for the continuous and accurate monitoring of physiological (e.g., motion [1, 47] and temperature [56, 57]) and electrophysiological (e.g., electrocardiograms [58, 59] and electromyograms [60, 61]) signals and appropriate instant feedback on them , which are important for point-of-care medical diagnostics and therapy. This section describes representative wearable sensors/actuators based on functional nanomaterials and their application examples in healthcare and human–machine interfaces.
2.1.1 SiNM-based sensors
Deformability, which is one of the key characteristics of wearable electronics, can be achieved by making inorganic materials (i.e., silicon) as thin as possible, down to the nanometer scale (i.e., nanomembrane) . SiNM can be fabricated through several processes. One easy fabrication method is to remove the buried oxide of a silicon-on-insulator (SOI) wafer and pick the top part up or to etch the bottom silicon of the SOI wafer and use the remaining top part . The obtained SiNM can be located in the desired position of the designed layout by using previously reported transfer printing techniques. SiNM maintains the high carrier mobility  and intrinsic piezoresistivity  of the bulk monocrystalline silicon, while having a high flexibility, which enables diverse wearable electronics applications.
By combining the SiNM strain gauge, pressure sensor, and temperature sensor array in a single platform, a skin-like device conformally mounted onto a prosthetic arm is demonstrated. The SiNM strain gauge array monitors the change in the strain distribution according to the clenching motion of the prosthetic hand (Fig. 2d). Similarly, the SiNM pressure sensor measures the applied pressure when typing with a keyboard (Fig. 2e, top) and grasping a baseball (Fig. 2e, bottom). The SiNM temperature sensor mounted on the prosthetic skin distinguishes different surface temperatures (Fig. 2f). Although these SiNM sensors exhibit a high potential for various wearable sensing applications, there are cost issues to be addressed for the development of commercial products.
2.1.2 CNT-based wearable sensors
CNTs are also excellent nanoscale filler materials owing to their small size with good dispersion and exceptional electrical and physical properties [63, 64]. In this regard, electrically conductive rubber (ECR), which is a composite of CNTs and elastomeric polymers, is prepared and used for a wearable mechanical sensor . To enhance the sensitivity, nanopores and micropores are introduced into the ECR, thereby increasing its piezoresistivity and maximizing the locally induced strain when deformed . Figure 3g shows a representative method for introducing pores with a uniform size and distribution in the ECR. The key idea of this method is to use a reverse micelle solution (RMS) comprising an emulsifier, deionized (DI) water, and an organic solvent. In accordance with careful sequential heat treatments, the migration and merging of the reverse micelles and subsequent pore generations occur (Fig. 3h). A larger porosity and lower elastic modulus are achieved if a larger amount of solvent is included in the RMS, thereby resulting in a higher pressure sensitivity (Fig. 3i). An ECR-based strain gauge fabricated on a medical bandage by using ink-jet printing forms a conformal contact with the human wrist and successfully monitors wrist motions. Although sensors based on CNT networks/composites are relatively cheap, especially those that are solution-processed, and mechanically compatible when worn on the human body, several issues such as a slow response time, a large area uniformity, and the hysteresis and drift of signals still need to be solved.
2.1.3 Wearable sensors/actuators based on nanomaterial hybrids
Figure 4f shows an illustration and optical image (inset) of a semitransparent piezoelectric strain sensor and resistive temperature sensor for measuring wrist motions and body-temperature changes for wheelchair control and hypothermia diagnosis, respectively. The strain sensor consists of a ZnO nanomembrane as the piezoelectric material and SWNT networks as the performance enhancer (Fig. 4g). The temperature sensor consists of silver nanoparticles (AgNPs) embedded in the ZnO:Al (AZO) nanomembrane for improving its sensitivity (Fig. 4h). For the strain sensor, co-deposited Cr and SWNTs layers improve the crystallinity of ZnO and passivate intrinsic defects, respectively (Fig. 4i). These modifications dramatically amplify the piezoelectric voltage output of the intrinsic ZnO nanomembrane (Fig. 4j). For the temperature sensor, EC – EF (EC, minimum energy of the conduction band; EF, Fermi energy level) is proportional to the concentration of AgNPs inside the ZnO nanomembrane (Fig. 4k). The high concentration of AgNPs increases the carrier density and therefore improves the sensitivity of the temperature sensor (Fig. 4l). A more in-depth study of functional hybrid nanomaterials would provide new opportunities for high-performance wearable devices.
2.2 Wearable memories
Data recorded by wearable sensors should be either transferred or stored for the analysis. Usually, the data are stored in memory devices and retrieved when needed. In this section, two types of ultrathin deformable nonvolatile memory devices—charge-trap floating-gate memory (CTFM)  and resistive random access memory (RRAM) —are described.
2.2.1 Deformable charge-trap floating-gate memory
The floating gate of a continuous metal film has a critical limitation for the retention time . Instead, metal nanoparticles (NPs) are a promising candidate as the floating gate to realize a fast program/erase speed and long retention time . Figure 5e shows an optical image of a fabricated flexible CTFM using poly(4-vinylphenol) (PVP), pentacene, and gold nanoparticles (AuNPs) as the dielectric, semiconductor, and charge-trap layer, respectively. AuNPs are electrostatically adsorbed onto the PVP blocking oxide, thereby forming a monolayer of AuNPs (Fig. 5f). A large on/off window (>10 V) is obtained owing to the high density of AuNPs (Fig. 5g). Repetitive bending up to 1000 cycles with a bending radius of 20 mm does not diminish the performance of the CTFM.
2.2.2 Nanoparticle-embedded wearable RRAM
RRAM is another promising candidate for future nonvolatile memory devices [75–77]. By integrating RRAM with wearable sensors, a low power consumption and mechanical deformability are important for long-term use in mobile environments . Figure 5i shows wearable RRAM consisting of AuNP charge-trap layers that reduce its operation current. Serpentine interconnections make the wearable RRAM stretchable up to 25 % strain (Fig. 5j–l). AuNPs embedded between TiO2 nanomembranes by Langmuir–Blodgett assembly form a uniform layer over a large area (Fig. 5m–o). The operation current of the wearable RRAM with one AuNP layer is decreased by one order of magnitude compared to that without AuNPs (Fig. 5p). Three layers of AuNPs exhibit a larger current decrease (by almost a factor of three).
2.3 Wearable displays
To construct user-interactive wearable electronic systems, deformable displays that visualize measured or stored data are indispensable for users. Recently, several breakthroughs in deformable LED technologies, including deformable inorganic/organic LEDs [51, 78–81], polymer LEDs [82–84], and quantum-dot LEDs (QLEDs) [85–87], have been reported.
2.4 Wearable energy devices
Energy storage devices and power generators that supply power to wearable electronics need flexibility and biocompatibility. An all-solid-state supercapacitor (SC) [45, 49, 90, 91] is a suitable energy storage device with regard to this point. Moreover, SCs have a high power density, a fast charging/discharging speed, and cycle durability . In case of the wearable power generators, flexible and soft fiber-based materials are suitable owing to the requirement of high deformability . In this section, carbon-nanomaterial-based flexible SCs and organic nanofiber-based power generators are reviewed.
2.4.1 CNT-based wearable energy devices
Instead of coating fabrics, carbon fibers are used to make a woven fabric, which can be applied to flexible textile electrodes . To maximize the surface area, vertically-aligned CNTs are additionally synthesized on the carbon fabric. Electroplating vertical CNTs with RuO2 NPs further increases the capacitance (Fig. 7f), and an all-solid-state wearable SC is fabricated by sandwiching a poly(vinyl alcohol) (PVA)-H3PO4 gel electrolyte between two modified carbon fabric electrodes (Fig. 7g). The resulting SC exhibits high performance up to 135-degree bending and 4000 charge–discharge cycles (Fig. 7h–j).
2.4.2 GP-based wearable energy devices
Multiple chemically converted GP sheets are beneficial for fast ion transport . GP flakes and/or reduced GP oxides are densely packed by capillary pressure to fabricate flexible carbon electrodes (Fig. 7k). The packing density (ρ) of the GP sheets can be controlled by changing the ratio of the volatile and nonvolatile liquids in the gel (Fig. 7l, m). Figure 7n and o show the specific capacitance and volumetric capacitance, respectively, of SCs using stacked GP electrodes for different values of ρ. The specific capacitance slightly decreases as ρ increases, whereas the volumetric capacitance is nearly proportional to ρ. Although most SCs made of activated carbon exhibit a volumetric energy density of 5–8 Wh/L, SCs made of the GP assembly exhibit a volumetric energy density of 60 Wh/L, which is similar to that of lead-acid batteries (50–90 Wh/L).
2.4.3 Organic nanofiber-based wearable power generators
To harvest electrical energy from body movements, piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs) have been used [28, 96]. Organic nanofibers such as polyvinylidene fluoride (PVDF) formed by using electrospinning processes have shown superb deformability as well as high piezoresistivity, facilitating its use in wearable applications [18, 28]. Piezoelectric power generation using a single PVDF nanofiber , aligned multiple PVDF nanofibers [98, 99], and randomly distributed nanofiber networks  have been demonstrated. Parallel and series connection of PVDF nanofibers increase the generated voltage and current . However, relatively low output power of PENGs has limited the application for wearable devices with high power consumption . In contrast, TENGs have shown much higher output power than PENGs . Electrospun PVDF nanofibers are also suitable for fabrication of the TENG because of their strong electronegativity and high porous morphology offering large contact area to increase the output power [28, 101]. The PVDF nanofiber-based TENG has been recently demonstrated as wearable forms . Seamless integration of the organic nanofiber-based wearable power generators with energy storage devices and control circuits is another important future research topic.
The mechanical, electrical, and optical properties of bulk materials change as their size is reduced and/or nanoscale structure engineering is introduced. By using the unique properties of such nanomaterials or their hybrids, many breakthroughs in wearable devices have been accomplished. In this paper, we reviewed the current status of wearable devices including sensors/actuators, memory devices, displays, and energy storage devices. We particularly focused on the use of functional nanomaterials to enhancing the deformability and performance of these devices. Continuous research and development of new nanomaterials/hybrids and their integration into variety of electronic/optoelectronic devices would provide new opportunities for next-generation wearable electronics.
JK and JL contributed equally. JK, JL, and D-HK wrote the manuscript. JK, JL, DS, MKC and D-HK designed the figures. All authors read and approved the final manuscript.
This research was supported by IBS-R006-D1. This work was supported by a Seoul National University Research Grant.
The authors declare that they have no competing interests.
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.
- S. Lim, D. Son, J. Kim, Y.B. Lee, J.K. Song, S. Choi, D.J. Lee, J.H. Kim, M. Lee, T. Hyeon, D.H. Kim, Transparent and stretchable interactive human machine interface based on patterned graphene heterostructures. Adv. Funct. Mater. 25, 375–383 (2015). doi:10.1002/adfm.201402987 View ArticleGoogle Scholar
- J. Kim, M. Lee, J. Rhim, P. Wang, N. Lu, D.-H. Kim, Next-generation flexible neural and cardiac electrode arrays. Biomed. Eng. Lett. 4, 95–108 (2014). doi:10.1007/s13534-014-0132-4 View ArticleGoogle Scholar
- D.H. Kim, J.H. Ahn, W.M. Choi, H.S. Kim, T.H. Kim, J.Z. Song, Y.G.Y. Huang, Z.J. Liu, C. Lu, J.A. Rogers, Stretchable and foldable silicon integrated circuits. Science 320, 507–511 (2008). doi:10.1126/science.1154367 View ArticleGoogle Scholar
- D.H. Kim, R. Ghaffari, N.S. Lu, J.A. Rogers, Flexible and stretchable electronics for biointegrated devices. Annu. Rev. Biomed. Eng. 14, 113–128 (2012). doi:10.1146/annurev-bioeng-071811-150018 View ArticleGoogle Scholar
- D.H. Kim, N.S. Lu, R. Ghaffari, J.A. Rogers, Inorganic semiconductor nanomaterials for flexible and stretchable bio-integrated electronics. NPG Asia Mater. 4, e15 (2012). doi:10.1038/am.2012.27 View ArticleGoogle Scholar
- D.H. Kim, J.L. Xiao, J.Z. Song, Y.G. Huang, J.A. Rogers, Stretchable, curvilinear electronics based on inorganic materials. Adv. Mater. 22, 2108–2124 (2010). doi:10.1002/adma.200902927 View ArticleGoogle Scholar
- J. Kim, M. Lee, H.J. Shim, R. Ghaffari, H.R. Cho, D. Son, Y.H. Jung, M. Soh, C. Choi, S. Jung, K. Chu, D. Jeon, S.T. Lee, J.H. Kim, S.H. Choi, T. Hyeon, D.H. Kim, Stretchable silicon nanoribbon electronics for skin prosthesis. Nat. Commun. 5, 5747 (2014). doi:10.1038/Ncomms6747 View ArticleGoogle Scholar
- M. Ying, A.P. Bonifas, N.S. Lu, Y.W. Su, R. Li, H.Y. Cheng, A. Ameen, Y.G. Huang, J.A. Rogers, Silicon nanomembranes for fingertip electronics. Nanotechnology 23, 344004 (2012). doi:10.1088/0957-4484/23/34/344004 View ArticleGoogle Scholar
- D.H. Kim, N.S. Lu, Y.G. Huang, J.A. Rogers, Materials for stretchable electronics in bioinspired and biointegrated devices. MRS Bull. 37, 226–235 (2012). doi:10.1557/mrs.2012.36 View ArticleGoogle Scholar
- J. Viventi, D.H. Kim, L. Vigeland, E.S. Frechette, J.A. Blanco, Y.S. Kim, A.E. Avrin, V.R. Tiruvadi, S.W. Hwang, A.C. Vanleer, D.F. Wulsin, K. Davis, C.E. Gelber, L. Palmer, J. Van der Spiegel, J. Wu, J.L. Xiao, Y.G. Huang, D. Contreras, J.A. Rogers, B. Litt, Flexible, foldable, actively multiplexed, high-density electrode array for mapping brain activity in vivo. Nat. Neurosci. 14, 1599–1605 (2011). doi:10.1038/nn.2973 View ArticleGoogle Scholar
- D.-H. Kim, W.M. Choi, J.-H. Ahn, H.-S. Kim, J. Song, Y. Huang, Z. Liu, C. Lu, C.G. Koh, J.A. Rogers, Complementary metal oxide silicon integrated circuits incorporating monolithically integrated stretchable wavy interconnects. Appl. Phys. Lett. 93, 044102 (2008). doi:10.1063/1.2963364 View ArticleGoogle Scholar
- K. Hata, D.N. Futaba, K. Mizuno, T. Namai, M. Yumura, S. Iijima, Water-assisted highly efficient synthesis of impurity-free single-waited carbon nanotubes. Science 306, 1362–1364 (2004). doi:10.1126/science.1104962 View ArticleGoogle Scholar
- T. Yamada, Y. Hayamizu, Y. Yamamoto, Y. Yomogida, A. Izadi-Najafabadi, D.N. Futaba, K. Hata, A stretchable carbon nanotube strain sensor for human-motion detection. Nat. Nanotechnol. 6, 296–301 (2011). doi:10.1038/Nnano.2011.36 View ArticleGoogle Scholar
- E. Roh, B.U. Hwang, D. Kim, B.Y. Kim, N.E. Lee, Stretchable, transparent, ultrasensitive, and patchable strain sensor for human-machine interfaces comprising a nanohybrid of carbon nanotubes and conductive elastomers. ACS Nano 9, 6252–6261 (2015). doi:10.1021/acsnano.5b01613 View ArticleGoogle Scholar
- X.W. Yang, C. Cheng, Y.F. Wang, L. Qiu, D. Li, Liquid-mediated dense integration of graphene materials for compact capacitive energy storage. Science 341, 534–537 (2013). doi:10.1126/science.1239089 View ArticleGoogle Scholar
- S.M. Lee, J.H. Kim, J.H. Ahn, Graphene as a flexible electronic material: mechanical limitations by defect formation and efforts to overcome. Mater. Today 18, 336–344 (2015). doi:10.1016/j.mattod.2015.01.017 View ArticleGoogle Scholar
- S.Y. Min, T.S. Kim, Y. Lee, H. Cho, W. Xu, T.W. Lee, Organic nanowire fabrication and device applications. Small 11, 45–62 (2015). doi:10.1002/smll.201401487 View ArticleGoogle Scholar
- J.Y. Chang, M. Domnner, C. Chang, L.W. Lin, Piezoelectric nanofibers for energy scavenging applications. Nano Energy 1, 356–371 (2012). doi:10.1016/j.nanoen.2012.02.003 View ArticleGoogle Scholar
- H. Jang, W. Lee, S.M. Won, S.Y. Ryu, D. Lee, J.B. Koo, S.D. Ahn, C.W. Yang, M.H. Jo, J.H. Cho, J.A. Rogers, J.H. Ahn, Quantum confinement effects in transferrable silicon nanomembranes and their applications on unusual substrates. Nano Lett. 13, 5600–5607 (2013). doi:10.1021/nl403251e View ArticleGoogle Scholar
- D.H. Kim, J.H. Ahn, H.S. Kim, K.J. Lee, T.H. Kim, C.J. Yu, R.G. Nuzzo, J.A. Rogers, Complementary logic gates and ring oscillators on plastic substrates by use of printed ribbons of single-crystalline silicon. IEEE Electron Device Lett. 29, 73–76 (2008). doi:10.1109/Led.2007.910770 View ArticleGoogle Scholar
- T. Durkop, S.A. Getty, E. Cobas, M.S. Fuhrer, Extraordinary mobility in semiconducting carbon nanotubes. Nano Lett. 4, 35–39 (2004). doi:10.1021/nl034841q View ArticleGoogle Scholar
- K.I. Bolotin, K.J. Sikes, Z. Jiang, M. Klima, G. Fudenberg, J. Hone, P. Kim, H.L. Stormer, Ultrahigh electron mobility in suspended graphene. Solid State Commun. 146, 351–355 (2008). doi:10.1016/j.ssc.2008.02.024 View ArticleGoogle Scholar
- E. Artukovic, M. Kaempgen, D.S. Hecht, S. Roth, G. GrUner, Transparent and flexible carbon nanotube transistors. Nano Lett. 5, 757–760 (2005). doi:10.1021/nl0505254o View ArticleGoogle Scholar
- L.B. Hu, W. Yuan, P. Brochu, G. Gruner, Q.B. Pei, Highly stretchable, conductive, and transparent nanotube thin films. Appl. Phys. Lett. 94, 161108 (2009). doi:10.1063/1.3114463 View ArticleGoogle Scholar
- R.R. Nair, P. Blake, A.N. Grigorenko, K.S. Novoselov, T.J. Booth, T. Stauber, N.M.R. Peres, A.K. Geim, Fine structure constant defines visual transparency of graphene. Science 320, 1308 (2008). doi:10.1126/science.1156965 View ArticleGoogle Scholar
- M.F.L. De Volder, S.H. Tawfick, R.H. Baughman, A.J. Hart, Carbon nanotubes: present and future commercial applications. Science 339, 535–539 (2013). doi:10.1126/science.1222453 View ArticleGoogle Scholar
- S.Y. Min, T.S. Kim, B.J. Kim, H. Cho, Y.Y. Noh, H. Yang, J.H. Cho, T.W. Lee, Large-scale organic nanowire lithography and electronics. Nat. Commun. 4, 1773 (2013). doi:10.1038/ncomms2785 View ArticleGoogle Scholar
- T. Huang, C. Wang, H. Yu, H.Z. Wang, Q.H. Zhang, M.F. Zhu, Human walking-driven wearable all-fiber triboelectric nanogenerator containing electrospun polyvinylidene fluoride piezoelectric nanofibers. Nano Energy 14, 226–235 (2015). doi:10.1016/j.nanoen.2015.01.038 View ArticleGoogle Scholar
- A. Gheibi, M. Latifi, A.A. Merati, R. Bagherzadeh, Piezoelectric electrospun nanofibrous materials for self-powering wearable electronic textiles applications. J. Polym. Res. 21, 469 (2014). doi:10.1007/s10965-014-0469-5 View ArticleGoogle Scholar
- X. Huang, C.L. Tan, Z.Y. Yin, H. Zhang, 25th anniversary article: hybrid nanostructures based on two-dimensional nanomaterials. Adv. Mater. 26, 2185–2204 (2014). doi:10.1002/adma.201304964 View ArticleGoogle Scholar
- Z. Yan, L.L. Ma, Y. Zhu, I. Lahiri, M.G. Hahm, Z. Liu, S.B. Yang, C.S. Xiang, W. Lu, Z.W. Peng, Z.Z. Sun, C. Kittrell, J. Lou, W.B. Choi, P.M. Ajayan, J.M. Tour, Three-dimensional metal–graphene–nanotube multifunctional hybrid materials. ACS Nano 7, 58–64 (2013). doi:10.1021/nn3015882 View ArticleGoogle Scholar
- L.P. Singh, K. Srivastava, R. Mishra, R.S. Ningthoujam, Multifunctional hybrid nanomaterials from water dispersible CaF2:Eu3+, Mn2+ and Fe3O4 for luminescence and hyperthermia application. J. Phys. Chem. C 118, 18087–18096 (2014). doi:10.1021/jp502825p View ArticleGoogle Scholar
- C.A. Strassert, M. Otter, R.Q. Albuquerque, A. Hone, Y. Vida, B. Maier, L. De Cola, Photoactive hybrid nanomaterial for targeting, labeling, and killing antibiotic-resistant bacteria. Angew. Chem. Int. Edit. 48, 7928–7931 (2009). doi:10.1002/anie.200902837 View ArticleGoogle Scholar
- A. Fahmi, T. Pietsch, C. Mendoza, N. Cheval, Functional hybrid materials. Mater. Today 12, 44–50 (2009). doi:10.1016/S1369-7021(09)70159-2 View ArticleGoogle Scholar
- D. Son, J. Lee, D.J. Lee, R. Ghaffari, S. Yun, S.J. Kim, J.E. Lee, H.R. Cho, S. Yoon, S.X. Yang, S. Lee, S.T. Qiao, D.S. Ling, S. Shin, J.K. Song, J. Kim, T. Kim, H. Lee, J. Kim, M. Soh, N. Lee, C.S. Hwang, S. Nam, N.S. Lu, T. Hyeon, S.H. Choi, D.H. Kim, Bioresorbable electronic stent integrated with therapeutic nanoparticles for endovascular diseases. ACS Nano 9, 5937–5946 (2015). doi:10.1021/acsnano.5b00651 View ArticleGoogle Scholar
- S.J. Kim, H.R. Cho, K.W. Cho, S.T. Qiao, J.S. Rhim, M. Soh, T. Kim, M.K. Choi, C. Choi, I. Park, N.S. Hwang, T. Hyeon, S.H. Choi, N.S. Lu, D.H. Kim, Multifunctional cell-culture platform for aligned cell sheet monitoring, transfer printing, and therapy. ACS Nano 9, 2677–2688 (2015). doi:10.1021/nn5064634 View ArticleGoogle Scholar
- S.W. Zeng, D. Baillargeat, H.P. Ho, K.T. Yong, Nanomaterials enhanced surface plasmon resonance for biological and chemical sensing applications. Chem. Soc. Rev. 43, 3426–3452 (2014). doi:10.1039/c3cs60479a View ArticleGoogle Scholar
- C. Buzea, I.I. Pacheco, K. Robbie, Nanomaterials and nanoparticles: sources and toxicity. Biointerphases 2, MR17–172 (2007). doi:10.1116/1.2815690 View ArticleGoogle Scholar
- T.J. Park, G.C. Papaefthymiou, A.J. Viescas, A. Moodenbaugh, S.S. Wong, Size-dependent magnetic properties of single-crystalline multiferroic BiFeO3 nanoparticles. Nano Lett. 7, 766–772 (2007). doi:10.1021/nl063039w View ArticleGoogle Scholar
- D. Guo, G.X. Xie, J.B. Luo, Mechanical properties of nanoparticles: basics and applications. J. Phys. D Appl. Phys. 47, 013001 (2014). doi:10.1088/0022-3727/47/1/013001 View ArticleGoogle Scholar
- D. Son, J. Lee, S. Qiao, R. Ghaffari, J. Kim, J.E. Lee, C. Song, S.J. Kim, D.J. Lee, S.W. Jun, S. Yang, M. Park, J. Shin, K. Do, M. Lee, K. Kang, C.S. Hwang, N.S. Lu, T. Hyeon, D.H. Kim, Multifunctional wearable devices for diagnosis and therapy of movement disorders. Nat. Nanotechnol. 9, 397–404 (2014). doi:10.1038/Nnano.2014.38 View ArticleGoogle Scholar
- S. Choi, J. Park, W. Hyun, J. Kim, J. Kim, Y.B. Lee, C. Song, H.J. Hwang, J.H. Kim, T. Hyeon, D.H. Kim, Stretchable heater using ligand-exchanged silver nanowire nanocomposite for wearable articular thermotherapy. ACS Nano 9, 6626–6633 (2015). doi:10.1021/acsnano.5b02790 View ArticleGoogle Scholar
- M.K. Choi, O.K. Park, C. Choi, S. Qiao, R. Ghaffari, J. Kim, D.J. Lee, M. Kim, W. Hyun, S.J. Kim, H.J. Hwang, S.-H. Kwon, T. Hyeon, N. Lu, D.-H. Kim, Cephalopod-inspired miniaturized suction cups for smart medical skin. Adv. Healthc. Mater. 5, 80–87 (2015). doi:10.1002/adhm.201500285 View ArticleGoogle Scholar
- M.K. Choi, J. Yang, K. Kang, D.C. Kim, C. Choi, C. Park, S.J. Kim, S.I. Chae, T.H. Kim, J.H. Kim, T. Hyeon, D.H. Kim, Wearable red–green–blue quantum dot light-emitting diode array using high-resolution intaglio transfer printing. Nat. Commun. 6, 7149 (2015). doi:10.1038/ncomms8149 View ArticleGoogle Scholar
- S. Jung, J. Lee, T. Hyeon, M. Lee, D.H. Kim, Fabric-based integrated energy devices for wearable activity monitors. Adv. Mater. 26, 6329–6334 (2014). doi:10.1002/adma.201402439 View ArticleGoogle Scholar
- M. Park, K. Do, J. Kim, D. Son, J.H. Koo, J. Park, J.-K. Song, J.H. Kim, M. Lee, T. Hyeon, D.-H. Kim, Oxide nanomembrane hybrids with enhanced mechano- and thermo-sensitivity for semitransparent epidermal electronics. Adv. Healthc. Mater. 4, 992–997 (2015). doi:10.1002/adhm.201500097 View ArticleGoogle Scholar
- S. Jung, J.H. Kim, J. Kim, S. Choi, J. Lee, I. Park, T. Hyeon, D.H. Kim, Reverse-micelle-induced porous pressure-sensitive rubber for wearable human-machine interfaces. Adv. Mater. 26, 4825–4830 (2014). doi:10.1002/adma.201401364 View ArticleGoogle Scholar
- D. Son, J.H. Koo, J.K. Song, J. Kim, M. Lee, H.J. Shim, M. Park, M. Lee, J.H. Kim, D.H. Kim, Stretchable carbon nanotube charge-trap floating-gate memory and logic devices for wearable electronics. ACS Nano 9, 5585–5593 (2015). doi:10.1021/acsnano.5b01848 View ArticleGoogle Scholar
- L. Hu, M. Pasta, F.L. Mantia, L. Cui, S. Jeong, H.D. Deshazer, J.W. Choi, S.M. Han, Y. Cui, Stretchable, porous, and conductive energy textiles. Nano Lett. 10, 708–714 (2010). doi:10.1021/nl903949m View ArticleGoogle Scholar
- C. Wang, D. Hwang, Z.B. Yu, K. Takei, J. Park, T. Chen, B.W. Ma, A. Javey, User-interactive electronic skin for instantaneous pressure visualization. Nat. Mater. 12, 899–904 (2013). doi:10.1038/nmat3711 View ArticleGoogle Scholar
- T. Sekitani, H. Nakajima, H. Maeda, T. Fukushima, T. Aida, K. Hata, T. Someya, Stretchable active-matrix organic light-emitting diode display using printable elastic conductors. Nat. Mater. 8, 494–499 (2009). doi:10.1038/nmat2459 View ArticleGoogle Scholar
- J.H. Warner, N.P. Young, A.I. Kirkland, G.A.D. Briggs, Resolving strain in carbon nanotubes at the atomic level. Nat. Mater. 10, 958–962 (2011). doi:10.1038/nmat3125 View ArticleGoogle Scholar
- K.W. Urban, Electron microscopy the challenges of graphene. Nat. Mater. 10, 165–166 (2011). doi:10.1038/nmat2964 View ArticleGoogle Scholar
- S. Patel, H. Park, P. Bonato, L. Chan, M. Rodgers, A review of wearable sensors and systems with application in rehabilitation. J. Neuroeng. Rehabil. 9, 21 (2012). doi:10.1186/1743-0003-9-21 View ArticleGoogle Scholar
- B.A. Ponce, M.E. Menendez, L.O. Oladeji, C.T. Fryberger, P.K. Dantuluri, Emerging technology in surgical education: combining real-time augmented reality and wearable computing devices. Orthopedics 37, 751–757 (2014). doi:10.3928/01477447-20141023-05 View ArticleGoogle Scholar
- L. Gao, Y.H. Zhang, V. Malyarchuk, L. Jia, K.I. Jang, R.C. Webb, H.R. Fu, Y. Shi, G.Y. Zhou, L.K. Shi, D. Shah, X. Huang, B.X. Xu, C.J. Yu, Y.G. Huang, J.A. Rogers, Epidermal photonic devices for quantitative imaging of temperature and thermal transport characteristics of the skin. Nat. Commun. 5, 4938 (2014). doi:10.1038/ncomms5938 View ArticleGoogle Scholar
- R.C. Webb, A.P. Bonifas, A. Behnaz, Y.H. Zhang, K.J. Yu, H.Y. Cheng, M.X. Shi, Z.G. Bian, Z.J. Liu, Y.S. Kim, W.H. Yeo, J.S. Park, J.Z. Song, Y.H. Li, Y.G. Huang, A.M. Gorbach, J.A. Rogers, Ultrathin conformal devices for precise and continuous thermal characterization of human skin. Nat. Mater. 12, 938–944 (2013). doi:10.1038/nmat3755 View ArticleGoogle Scholar
- W.H. Yeo, Y.S. Kim, J. Lee, A. Ameen, L.K. Shi, M. Li, S.D. Wang, R. Ma, S.H. Jin, Z. Kang, Y.G. Huang, J.A. Rogers, Multifunctional epidermal electronics printed directly onto the skin. Adv. Mater. 25, 2773–2778 (2013). doi:10.1002/adma.201204426 View ArticleGoogle Scholar
- J.W. Jeong, M.K. Kim, H.Y. Cheng, W.H. Yeo, X. Huang, Y.H. Liu, Y.H. Zhang, Y.G. Huang, J.A. Rogers, Capacitive epidermal electronics for electrically safe, long-term electrophysiological measurements. Adv. Healthc. Mater. 3, 642–648 (2014). doi:10.1002/adhm.201300334 View ArticleGoogle Scholar
- D.H. Kim, N.S. Lu, R. Ma, Y.S. Kim, R.H. Kim, S.D. Wang, J. Wu, S.M. Won, H. Tao, A. Islam, K.J. Yu, T.I. Kim, R. Chowdhury, M. Ying, L.Z. Xu, M. Li, H.J. Chung, H. Keum, M. McCormick, P. Liu, Y.W. Zhang, F.G. Omenetto, Y.G. Huang, T. Coleman, J.A. Rogers, Epidermal electronics. Science 333, 838–843 (2011). doi:10.1126/science.1206157 View ArticleGoogle Scholar
- J.W. Jeong, W.H. Yeo, A. Akhtar, J.J.S. Norton, Y.J. Kwack, S. Li, S.Y. Jung, Y.W. Su, W. Lee, J. Xia, H.Y. Cheng, Y.G. Huang, W.S. Choi, T. Bretl, J.A. Rogers, Materials and optimized designs for human-machine interfaces via epidermal electronics. Adv. Mater. 25, 6839–6846 (2013). doi:10.1002/adma.201301921 View ArticleGoogle Scholar
- J. Viventi, D.H. Kim, J.D. Moss, Y.S. Kim, J.A. Blanco, N. Annetta, A. Hicks, J.L. Xiao, Y.G. Huang, D.J. Callans, J.A. Rogers, B. Litt, A conformal, bio-interfaced class of silicon electronics for mapping cardiac electrophysiology. Sci. Transl. Med. 2, 24ra22 (2010). doi:10.1126/scitranslmed.3000738 View ArticleGoogle Scholar
- M. Moniruzzaman, K.I. Winey, Polymer nanocomposites containing carbon nanotubes. Macromolecules 39, 5194–5205 (2006). doi:10.1021/ma060733p View ArticleGoogle Scholar
- B. Fiedler, F.H. Gojny, M.H.G. Wichmann, M.C.M. Nolte, K. Schulte, Fundamental aspects of nano-reinforced composites. Compos. Sci. Technol. 66, 3115–3125 (2006). doi:10.1016/j.compscitech.2005.01.014 View ArticleGoogle Scholar
- B.K. Sharma, B. Jang, J.E. Lee, S.H. Bae, T.W. Kim, H.J. Lee, J.H. Kim, J.H. Ahn, Load-controlled roll transfer of oxide transistors for stretchable electronics. Adv. Funct. Mater. 23, 2024–2032 (2013). doi:10.1002/adfm.201202519 View ArticleGoogle Scholar
- H. Lee, Y. Lee, C. Song, H.R. Cho, R. Ghaffari, T.K. Choi, K.H. Kim, Y.B. Lee, D. Ling, H. Lee, S.J. Yu, S.H. Choi, T. Hyeon, D.H. Kim, An endoscope with integrated transparent bioelectronics and theranostic nanoparticles for colon cancer treatment. Nat. Commun. 6, 10059 (2015). doi:10.1038/ncomms10059 View ArticleGoogle Scholar
- D. Kahng, S.M. Sze, A floating gate and its application to memory devices. Bell Sys. Tech. J. 46, 1288–1295 (1967)View ArticleGoogle Scholar
- J.S. Meena, S.M. Sze, U. Chand, T.Y. Tseng, Overview of emerging nonvolatile memory technologies. Nanoscale Res. Lett. 9, 526 (2014). doi:10.1186/1556-276x-9-526 View ArticleGoogle Scholar
- R. Bez, E. Camerlenghi, A. Modelli, A. Visconti, Introduction to flash memory. Proc IEEE 91, 489–502 (2003). doi:10.1109/jproc.2003.811702 View ArticleGoogle Scholar
- T. Sekitani, T. Yokota, U. Zschieschang, H. Klauk, S. Bauer, K. Takeuchi, M. Takamiya, T. Sakurai, T. Someya, Organic nonvolatile memory transistors for flexible sensor arrays. Science 326, 1516–1519 (2009). doi:10.1126/science.1179963 View ArticleGoogle Scholar
- S.-J. Kim, J.-S. Lee, Flexible organic transistor memory devices. Nano Lett. 10, 2884–2890 (2010). doi:10.1021/nl1009662 View ArticleGoogle Scholar
- S.M. Kim, E.B. Song, S. Lee, J.F. Zhu, D.H. Seo, M. Mecklenburg, S. Seo, K.L. Wang, Transparent and flexible graphene charge-trap memory. ACS Nano 6, 7879–7884 (2012). doi:10.1021/nn302193q View ArticleGoogle Scholar
- J. Kim, D. Son, M. Lee, C. Song, J.-K. Song, J. H. Koo, D.J. Lee, H.J. Shim, J.H. Kim, M. Lee, T. Hyeon, D.H. Kim, A wearable multiplexed silicon nonvolatile memory array using nanocrystal charge confinement. Sci. Adv. 2, e1501101 (2016). doi:10.1126/sciadv.1501101 View ArticleGoogle Scholar
- J.-S. Lee, Recent progress in gold nanoparticle-based non-volatile memory devices. Gold Bull. 43, 189–199 (2010). doi:10.1007/BF03214986 View ArticleGoogle Scholar
- R. Waser, M. Aono, Nanoionics-based resistive switching memories. Nat. Mater. 6, 833–840 (2007). doi:10.1038/nmat2023 View ArticleGoogle Scholar
- D.H. Kwon, K.M. Kim, J.H. Jang, J.M. Jeon, M.H. Lee, G.H. Kim, X.S. Li, G.S. Park, B. Lee, S. Han, M. Kim, C.S. Hwang, Atomic structure of conducting nanofilaments in TiO2 resistive switching memory. Nat. Nanotechnol. 5, 148–153 (2010). doi:10.1038/Nnano.2009.456 View ArticleGoogle Scholar
- J. Borghetti, G.S. Snider, P.J. Kuekes, J.J. Yang, D.R. Stewart, R.S. Williams, ‘Memristive’ switches enable ‘stateful’ logic operations via material implication. Nature 464, 873–876 (2010). doi:10.1038/nature08940 View ArticleGoogle Scholar
- R.H. Kim, D.H. Kim, J.L. Xiao, B.H. Kim, S.I. Park, B. Panilaitis, R. Ghaffari, J.M. Yao, M. Li, Z.J. Liu, V. Malyarchuk, D.G. Kim, A.P. Le, R.G. Nuzzo, D.L. Kaplan, F.G. Omenetto, Y.G. Huang, Z. Kang, J.A. Rogers, Waterproof AlInGaP optoelectronics on stretchable substrates with applications in biomedicine and robotics. Nat. Mater. 9, 929–937 (2010). doi:10.1038/nmat2879 View ArticleGoogle Scholar
- T.I. Kim, J.G. McCall, Y.H. Jung, X. Huang, E.R. Siuda, Y.H. Li, J.Z. Song, Y.M. Song, H.A. Pao, R.H. Kim, C.F. Lu, S.D. Lee, I.S. Song, G. Shin, R. Al-Hasani, S. Kim, M.P. Tan, Y.G. Huang, F.G. Omenetto, J.A. Rogers, M.R. Bruchas, Injectable, cellular-scale optoelectronics with applications for wireless optogenetics. Science 340, 211–216 (2013). doi:10.1126/science.1232437 View ArticleGoogle Scholar
- S.I. Park, Y.J. Xiong, R.H. Kim, P. Elvikis, M. Meitl, D.H. Kim, J. Wu, J. Yoon, C.J. Yu, Z.J. Liu, Y.G. Huang, K. Hwang, P. Ferreira, X.L. Li, K. Choquette, J.A. Rogers, Printed assemblies of inorganic light-emitting diodes for deformable and semitransparent displays. Science 325, 977–981 (2009). doi:10.1126/science.1175690 View ArticleGoogle Scholar
- T.H. Han, Y. Lee, M.R. Choi, S.H. Woo, S.H. Bae, B.H. Hong, J.H. Ahn, T.W. Lee, Extremely efficient flexible organic light-emitting diodes with modified graphene anode. Nat. Photon. 6, 105–110 (2012). doi:10.1038/nphoton.2011.318 View ArticleGoogle Scholar
- J.J. Liang, L. Li, X.F. Niu, Z.B. Yu, Q.B. Pei, Elastomeric polymer light-emitting devices and displays. Nat. Photon. 7, 817–824 (2013). doi:10.1038/nphoton.2013.242 View ArticleGoogle Scholar
- Z.B. Yu, X.F. Niu, Z.T. Liu, Q.B. Pei, Intrinsically stretchable polymer light-emitting devices using carbon nanotube-polymer composite electrodes. Adv. Mater. 23, 3989–3994 (2011). doi:10.1002/adma.201101986 View ArticleGoogle Scholar
- M.S. White, M. Kaltenbrunner, E.D. Glowacki, K. Gutnichenko, G. Kettlgruber, I. Graz, S. Aazou, C. Ulbricht, D.A.M. Egbe, M.C. Miron, Z. Major, M.C. Scharber, T. Sekitani, T. Someya, S. Bauer, N.S. Sariciftci, Ultrathin, highly flexible and stretchable pleds. Nat. Photon. 7, 811–816 (2013). doi:10.1038/nphoton.2013.188 View ArticleGoogle Scholar
- T.H. Kim, K.S. Cho, E.K. Lee, S.J. Lee, J. Chae, J.W. Kim, D.H. Kim, J.Y. Kwon, G. Amaratunga, S.Y. Lee, B.L. Choi, Y. Kuk, J.M. Kim, K. Kim, Full-colour quantum dot displays fabricated by transfer printing. Nat. Photon. 5, 176–182 (2011). doi:10.1038/nphoton.2011.12 View ArticleGoogle Scholar
- X.Y. Yang, E. Mutlugun, C. Dang, K. Dev, Y. Gao, S.T. Tan, X.W. Sun, H.V. Demir, Highly flexible, electrically driven, top-emitting, quantum dot light-emitting stickers. ACS Nano 8, 8224–8231 (2014). doi:10.1021/nn502588k View ArticleGoogle Scholar
- M.K. Choi, I. Park, D.C. Kim, E. Joh, O.K. Park, J. Kim, M. Kim, C. Choi, J. Yang, K.W. Cho, J.-H. Hwang, J.-M. Nam, T. Hyeon, J.H. Kim, D.-H. Kim, Thermally controlled, patterned graphene transfer printing for transparent and wearable electronic/optoelectronic system. Adv. Funct. Mater. 9, 7109–7118 (2015). doi:10.1002/adfm.201502956 View ArticleGoogle Scholar
- J. Kwak, W.K. Bae, D. Lee, I. Park, J. Lim, M. Park, H. Cho, H. Woo, D.Y. Yoon, K. Char, S. Lee, C. Lee, Bright and efficient full-color colloidal quantum dot light-emitting diodes using an inverted device structure. Nano Lett. 12, 2362–2366 (2012). doi:10.1021/nl3003254 View ArticleGoogle Scholar
- X.L. Dai, Z.X. Zhang, Y.Z. Jin, Y. Niu, H.J. Cao, X.Y. Liang, L.W. Chen, J.P. Wang, X.G. Peng, Solution-processed, high-performance light-emitting diodes based on quantum dots. Nature 515, 96–99 (2014). doi:10.1038/nature13829 View ArticleGoogle Scholar
- Y.J. Kang, S.J. Chun, S.S. Lee, B.Y. Kim, J.H. Kim, H. Chung, S.Y. Lee, W. Kim, All-solid-state flexible supercapacitors fabricated with bacterial nanocellulose papers, carbon nanotubes, and triblock-copolymer ion gels. ACS Nano 6, 6400–6406 (2012). doi:10.1021/nn301971r View ArticleGoogle Scholar
- X. Xiao, T.Q. Li, P.H. Yang, Y. Gao, H.Y. Jin, W.J. Ni, W.H. Zhan, X.H. Zhang, Y.Z. Cao, J.W. Zhong, L. Gong, W.C. Yen, W.J. Mai, J. Chen, K.F. Huo, Y.L. Chueh, Z.L. Wang, J. Zhou, Fiber-based all-solid-state flexible supercapacitors for self-powered systems. ACS Nano 6, 9200–9206 (2012). doi:10.1021/nn303530k View ArticleGoogle Scholar
- P. Simon, Y. Gogotsi, Materials for electrochemical capacitors. Nat. Mater. 7, 845–854 (2008). doi:10.1038/nmat2297 View ArticleGoogle Scholar
- D.N. Futaba, K. Hata, T. Yamada, T. Hiraoka, Y. Hayamizu, Y. Kakudate, O. Tanaike, H. Hatori, M. Yumura, S. Iijima, Shape-engineerable and highly densely packed single-walled carbon nanotubes and their application as super-capacitor electrodes. Nat. Mater. 5, 987–994 (2006). doi:10.1038/nmat1782 View ArticleGoogle Scholar
- H. Zhang, G.P. Cao, Z.Y. Wang, Y.S. Yang, Z.J. Shi, Z.N. Gu, Growth of manganese oxide nanoflowers on vertically-aligned carbon nanotube arrays for high-rate electrochemical capacitive energy storage. Nano Lett. 8, 2664–2668 (2008). doi:10.1021/nl800925j View ArticleGoogle Scholar
- J.S. Ye, H.F. Cui, X. Liu, T.M. Lim, W.D. Zhang, F.S. Sheu, Preparation and characterization of aligned carbon nanotube-ruthenium oxide nanocomposites for supercapacitors. Small 1, 560–565 (2005). doi:10.1002/smll.200400137 View ArticleGoogle Scholar
- S. Jung, S. Hong, J. Kim, S. Lee, T. Hyeon, M. Lee, D.H. Kim, Wearable fall detector using integrated sensors and energy devices. Sci. Rep. 5, 17081 (2015). doi:10.1038/srep17081 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, 726–731 (2010). doi:10.1021/nl9040719 View ArticleGoogle Scholar
- J. Chang, L. Lin, Large array electrospun PVDF nanogenerators on a flexible substrate. Paper presented at the 16th international conference on solid-state sensors, actuators and microsystems (TRANSDUCERS), Beijing, 5–9 June 2011Google Scholar
- B.J. Hansen, Y. Liu, R.S. Yang, Z.L. Wang, Hybrid nanogenerator for concurrently harvesting biomechanical and biochemical energy. ACS Nano 4, 3647–3652 (2010). doi:10.1021/nn100845b View ArticleGoogle Scholar
- J. Fang, X.G. Wang, T. Lin, Electrical power generator from randomly oriented electrospun poly(vinylidene fluoride) nanofibre membranes. J. Mater. Chem. 21, 11088–11091 (2011). doi:10.1039/c1jm11445j View ArticleGoogle Scholar
- A.F. Diaz, R.M. Felix-Navarro, A semi-quantitative tribo-electric series for polymeric materials: the influence of chemical structure and properties. J. Electrostat. 62, 277–290 (2004). doi:10.1016/jelstat.2004.05.005 View ArticleGoogle Scholar