Special Issue "Nanomaterials for Flexible and Stretchable Devices: Synthesis, Processes, and Applications"

A special issue of Nanomaterials (ISSN 2079-4991).

Deadline for manuscript submissions: closed (31 May 2016)

Special Issue Editors

Guest Editor
Prof. Dr. Ming-Tsang Lee

Department of Mechanical Engineering, National Chung Hsing University, Taichung, Taiwan
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Phone: +886-4-22840433 ext. 419
Interests: heat transfer; nanocatalysis; energy conversion; advanced manufacturing
Guest Editor
Prof. Dr. Te-Hua Fang

Department of Mechanical Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung 807, Taiwan
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Phone: +886-7-3814526 (ext. 5336)
Interests: solid mechanics; nanomaterials; scanning probe microscopy and nanofabrication; computational mechanics and nanomechanics
Guest Editor
Prof. Dr. Chien-Hung Liu

Department of Mechanical Engineering, National Chung Hsing University, 250 Kuo Kuang Rd., Taichung 402, Taiwan
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Fax: +886 4 2287 7170
Interests: high precision instrument design; laser engineering; smart sensors and actuators; optical device; optical measurement; metrology; automatic control; nanotechnology

Special Issue Information

Dear Colleagues,

Recent demands regarding wearable, light-weight portable devices stressed the importance of developing new materials for bendable, rollable, and even stretchable electronics on nonrigid substrates, and nanomaterials have played a significant role in the improvement of these flexible/stretchable electronics in recent years. The wide variety of nanomaterials has proven to exhibit significant flexibility/stretchability at both the micro- and macroscale, while much attention also has been focused on novel techniques developed for nanomaterial processing to meet the mild processing conditions and enable facile production in relatively simple procedures. The application of these nanomaterials on flexible/stretchable devices is currently an active and vibrant research area that has high potential in the display, sensors, energy storage, conversion, and harvesting fields.

We invite authors to contribute original research articles and review articles covering current progress on the preparation and the usage of nanomaterials for flexible and stretchable devices. The current Special Issue will take account of a broad range of subjects from nanomaterial synthesis to relevant technologies and the resultant nanomaterial-based flexible and stretchable devices. Potential topics include, but are not limited to:

  1. Synthesis and characterization of nanomaterials
  2. Design and preparation of novel nanotextured/nanostructured surfaces
  3. Flexible/stretchable percolation network composed of low-dimensional nanomaterials
  4. Solution processes and other lithography-free techniques for nanomaterial processing
  5. Nanomaterial-based printing techniques including 3D printing
  6. Other environmentally friendly processes compatible to substrates
  7. Nanomaterial-based flexible/stretchable electronics including display, sensor, and energy devices
  8. Other applications related to nanomaterials for devices
  9. Post-processing to enhance mechanical stability of flexible/stretchable devices

Dr. Ming-Tsang Lee
Prof. Dr. Te-Hua Fang
Prof. Dr. Chien-Hung Liu
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Nanomaterials is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • nanomaterial for display, sensor, and energy devices
  • flexible/stretchable devices
  • nanotextured/nanostructured surfaces
  • nanomaterials for micro/nano manufacturing
  • nanomaterials for 3D printing
  • lithography-free techniques

Published Papers (13 papers)

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Research

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Open AccessCommunication Controlled Mechanical Cracking of Metal Films Deposited on Polydimethylsiloxane (PDMS)
Nanomaterials 2016, 6(9), 168; doi:10.3390/nano6090168
Received: 25 May 2016 / Revised: 30 August 2016 / Accepted: 7 September 2016 / Published: 9 September 2016
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Abstract
Stretchable large area electronics conform to arbitrarily-shaped 3D surfaces and enables comfortable contact to the human skin and other biological tissue. There are approaches allowing for large area thin films to be stretched by tens of percent without cracking. The approach presented here
[...] Read more.
Stretchable large area electronics conform to arbitrarily-shaped 3D surfaces and enables comfortable contact to the human skin and other biological tissue. There are approaches allowing for large area thin films to be stretched by tens of percent without cracking. The approach presented here does not prevent cracking, rather it aims to precisely control the crack positions and their orientation. For this purpose, the polydimethylsiloxane (PDMS) is hardened by exposure to ultraviolet radiation (172 nm) through an exposure mask. Only well-defined patterns are kept untreated. With these soft islands cracks at the hardened surface can be controlled in terms of starting position, direction and end position. This approach is first investigated at the hardened PDMS surface itself. It is then applied to conductive silver films deposited from the liquid phase. It is found that statistical (uncontrolled) cracking of the silver films can be avoided at strain below 35%. This enables metal interconnects to be integrated into stretchable networks. The combination of controlled cracks with wrinkling enables interconnects that are stretchable in arbitrary and changing directions. The deposition and patterning does not involve vacuum processing, photolithography, or solvents. Full article
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Open AccessArticle Inverter Circuits Using ZnO Nanoparticle Based Thin-Film Transistors for Flexible Electronic Applications
Nanomaterials 2016, 6(9), 154; doi:10.3390/nano6090154
Received: 27 May 2016 / Revised: 10 August 2016 / Accepted: 16 August 2016 / Published: 23 August 2016
Cited by 2 | PDF Full-text (4116 KB) | HTML Full-text | XML Full-text
Abstract
Innovative systems exploring the flexibility and the transparency of modern semiconducting materials are being widely researched by the scientific community and by several companies. For a low-cost production and large surface area applications, thin-film transistors (TFTs) are the key elements driving the system
[...] Read more.
Innovative systems exploring the flexibility and the transparency of modern semiconducting materials are being widely researched by the scientific community and by several companies. For a low-cost production and large surface area applications, thin-film transistors (TFTs) are the key elements driving the system currents. In order to maintain a cost efficient integration process, solution based materials are used as they show an outstanding tradeoff between cost and system complexity. In this paper, we discuss the integration process of ZnO nanoparticle TFTs using a high-k resin as gate dielectric. The performance in dependence on the transistor structure has been investigated, and inverted staggered setups depict an improved performance over the coplanar device increasing both the field-effect mobility and the ION/IOFF ratio. Aiming at the evaluation of the TFT characteristics for digital circuit applications, inverter circuits using a load TFT in the pull-up network and an active TFT in the pull-down network were integrated. The inverters show reasonable switching characteristics and V/V gains. Conjointly, the influence of the geometry ratio and the supply voltage on the devices have been analyzed. Moreover, as all integration steps are suitable to polymeric templates, the fabrication process is fully compatible to flexible substrates. Full article
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Open AccessArticle Optoelectronic and Electrochemical Properties of Vanadium Pentoxide Nanowires Synthesized by Vapor-Solid Process
Nanomaterials 2016, 6(8), 140; doi:10.3390/nano6080140
Received: 31 May 2016 / Revised: 11 July 2016 / Accepted: 19 July 2016 / Published: 29 July 2016
Cited by 1 | PDF Full-text (5288 KB) | HTML Full-text | XML Full-text
Abstract
Substantial synthetic vanadium pentoxide (V2O5) nanowires were successfully produced by a vapor-solid (VS) method of thermal evaporation without using precursors as nucleation sites for single crystalline V2O5 nanowires with a (110) growth plane. The micromorphology and
[...] Read more.
Substantial synthetic vanadium pentoxide (V2O5) nanowires were successfully produced by a vapor-solid (VS) method of thermal evaporation without using precursors as nucleation sites for single crystalline V2O5 nanowires with a (110) growth plane. The micromorphology and microstructure of V2O5 nanowires were analyzed by scanning electron microscope (SEM), energy-dispersive X-ray spectroscope (EDS), transmission electron microscope (TEM) and X-ray diffraction (XRD). The spiral growth mechanism of V2O5 nanowires in the VS process is proved by a TEM image. The photo-luminescence (PL) spectrum of V2O5 nanowires shows intrinsic (410 nm and 560 nm) and defect-related (710 nm) emissions, which are ascribable to the bound of inter-band transitions (V 3d conduction band to O 2p valence band). The electrical resistivity could be evaluated as 64.62 Ω·cm via four-point probe method. The potential differences between oxidation peak and reduction peak are 0.861 V and 0.470 V for the first and 10th cycle, respectively. Full article
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Open AccessArticle A Gallium Oxide-Graphene Oxide Hybrid Composite for Enhanced Photocatalytic Reaction
Nanomaterials 2016, 6(7), 127; doi:10.3390/nano6070127
Received: 1 June 2016 / Revised: 20 June 2016 / Accepted: 23 June 2016 / Published: 1 July 2016
Cited by 3 | PDF Full-text (2086 KB) | HTML Full-text | XML Full-text
Abstract
Hybrid composites (HCs) made up of gallium oxide (GaO) and graphene oxide (GO) were investigated with the intent of enhancing a photocatalytic reaction under ultraviolet (UV) radiation. The material properties of both GaO and GO were preserved, even after the formation of the
[...] Read more.
Hybrid composites (HCs) made up of gallium oxide (GaO) and graphene oxide (GO) were investigated with the intent of enhancing a photocatalytic reaction under ultraviolet (UV) radiation. The material properties of both GaO and GO were preserved, even after the formation of the HCs. The incorporation of the GO into the GaO significantly enhanced the photocatalytic reaction, as indicated by the amount of methylene blue (MB) degradation. The improvements in the reaction were discussed in terms of increased surface area and the retarded recombination of generated charged carriers. Full article
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Open AccessArticle Stress Waves and Characteristics of Zigzag and Armchair Silicene Nanoribbons
Nanomaterials 2016, 6(7), 120; doi:10.3390/nano6070120
Received: 3 March 2016 / Revised: 1 June 2016 / Accepted: 16 June 2016 / Published: 24 June 2016
Cited by 3 | PDF Full-text (3980 KB) | HTML Full-text | XML Full-text
Abstract
The mechanical properties of silicene nanostructures subject to tensile loading were studied via a molecular dynamics (MD) simulation. The effects of temperature on Young’s modulus and the fracture strain of silicene with armchair and zigzag types were examined. The maximum in-plane stress and
[...] Read more.
The mechanical properties of silicene nanostructures subject to tensile loading were studied via a molecular dynamics (MD) simulation. The effects of temperature on Young’s modulus and the fracture strain of silicene with armchair and zigzag types were examined. The maximum in-plane stress and the corresponding critical strain of the armchair and the zigzag silicene sheets at 300 K were 8.85 and 10.62, and 0.187 and 0.244 N/m, respectively. The in-plane stresses of the silicene sheet in the armchair direction at the temperatures of 300, 400, 500, and 600 K were 8.85, 8.50, 8.26, and 7.79 N/m, respectively. The in-plane stresses of the silicene sheet in the zigzag direction at the temperatures of 300, 400, 500, and 600 K were 10.62, 9.92, 9.64, and 9.27 N/m, respectively. The improved mechanical properties can be calculated in a silicene sheet yielded in the zigzag direction compared with the tensile loading in the armchair direction. The wrinklons and waves were observed at the shear band across the center zone of the silicene sheet. These results provide useful information about the mechanical and fracture behaviors of silicene for engineering applications. Full article
Open AccessArticle A Flexible 360-Degree Thermal Sound Source Based on Laser Induced Graphene
Nanomaterials 2016, 6(6), 112; doi:10.3390/nano6060112
Received: 26 April 2016 / Revised: 16 May 2016 / Accepted: 30 May 2016 / Published: 7 June 2016
Cited by 2 | PDF Full-text (2603 KB) | HTML Full-text | XML Full-text
Abstract
A flexible sound source is essential in a whole flexible system. It’s hard to integrate a conventional sound source based on a piezoelectric part into a whole flexible system. Moreover, the sound pressure from the back side of a sound source is usually
[...] Read more.
A flexible sound source is essential in a whole flexible system. It’s hard to integrate a conventional sound source based on a piezoelectric part into a whole flexible system. Moreover, the sound pressure from the back side of a sound source is usually weaker than that from the front side. With the help of direct laser writing (DLW) technology, the fabrication of a flexible 360-degree thermal sound source becomes possible. A 650-nm low-power laser was used to reduce the graphene oxide (GO). The stripped laser induced graphene thermal sound source was then attached to the surface of a cylindrical bottle so that it could emit sound in a 360-degree direction. The sound pressure level and directivity of the sound source were tested, and the results were in good agreement with the theoretical results. Because of its 360-degree sound field, high flexibility, high efficiency, low cost, and good reliability, the 360-degree thermal acoustic sound source will be widely applied in consumer electronics, multi-media systems, and ultrasonic detection and imaging. Full article
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Open AccessArticle Investigation of the Structural, Electrical, and Optical Properties of the Nano-Scale GZO Thin Films on Glass and Flexible Polyimide Substrates
Nanomaterials 2016, 6(5), 88; doi:10.3390/nano6050088
Received: 7 March 2016 / Revised: 21 April 2016 / Accepted: 29 April 2016 / Published: 10 May 2016
Cited by 2 | PDF Full-text (4198 KB) | HTML Full-text | XML Full-text
Abstract
In this study, Ga2O3-doped ZnO (GZO) thin films were deposited on glass and flexible polyimide (PI) substrates at room temperature (300 K), 373 K, and 473 K by the radio frequency (RF) magnetron sputtering method. After finding the deposition
[...] Read more.
In this study, Ga2O3-doped ZnO (GZO) thin films were deposited on glass and flexible polyimide (PI) substrates at room temperature (300 K), 373 K, and 473 K by the radio frequency (RF) magnetron sputtering method. After finding the deposition rate, all the GZO thin films with a nano-scale thickness of about 150 ± 10 nm were controlled by the deposition time. X-ray diffraction patterns indicated that the GZO thin films were not amorphous and all exhibited the (002) peak, and field emission scanning electron microscopy showed that only nano-scale particles were observed. The dependences of the structural, electrical, and optical properties of the GZO thin films on different deposition temperatures and substrates were investigated. X-ray photoemission spectroscopy (XPS) was used to measure the elemental composition at the chemical and electronic states of the GZO thin films deposited on different substrates, which could be used to clarify the mechanism of difference in electrical properties of the GZO thin films. In this study, the XPS binding energy spectra of Ga2p3/2 and Ga2p1/2 peaks, Zn2p3/2 and Zn2p1/2 peaks, the Ga3d peak, and O1s peaks for GZO thin films on glass and PI substrates were well compared. Full article
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Open AccessArticle High Refractive Organic–Inorganic Hybrid Films Prepared by Low Water Sol-Gel and UV-Irradiation Processes
Nanomaterials 2016, 6(3), 44; doi:10.3390/nano6030044
Received: 29 December 2015 / Revised: 20 February 2016 / Accepted: 23 February 2016 / Published: 9 March 2016
Cited by 1 | PDF Full-text (3442 KB) | HTML Full-text | XML Full-text
Abstract
Organic-inorganic hybrid sols (Ti–O–Si precursor) were first synthesized by the sol-gel method at low addition of water, and were then employed to prepare a highly refractive hybrid optical film. This film was obtained by blending the Ti–O–Si precursor with 2-phenylphenoxyethyl acrylate (OPPEA) to
[...] Read more.
Organic-inorganic hybrid sols (Ti–O–Si precursor) were first synthesized by the sol-gel method at low addition of water, and were then employed to prepare a highly refractive hybrid optical film. This film was obtained by blending the Ti–O–Si precursor with 2-phenylphenoxyethyl acrylate (OPPEA) to perform photo-polymerization by ultraviolet (UV) irradiation. Results show that the film transparency of poly(Ti–O–Si precursor-co-OPPEA) film is higher than that of a pure poly(Ti–O–Si precursor) film, and that this poly(Ti–O–Si precursor-co-OPPEA) hybrid film exhibits a high transparency of ~93.7% coupled with a high refractive index (n) of 1.83 corresponding to a thickness of 2.59 μm. Full article
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Open AccessArticle Nano-Welding of Multi-Walled Carbon Nanotubes on Silicon and Silica Surface by Laser Irradiation
Nanomaterials 2016, 6(3), 36; doi:10.3390/nano6030036
Received: 10 December 2015 / Revised: 15 January 2016 / Accepted: 20 January 2016 / Published: 24 February 2016
Cited by 1 | PDF Full-text (2071 KB) | HTML Full-text | XML Full-text
Abstract
In this study, a continuous fiber laser (1064 nm wavelength, 30 W/cm2) is used to irradiate multi-walled carbon nanotubes (MWCNTs) on different substrate surfaces. Effects of substrates on nano-welding of MWCNTs are investigated by scanning electron microscope (SEM). For MWCNTs on
[...] Read more.
In this study, a continuous fiber laser (1064 nm wavelength, 30 W/cm2) is used to irradiate multi-walled carbon nanotubes (MWCNTs) on different substrate surfaces. Effects of substrates on nano-welding of MWCNTs are investigated by scanning electron microscope (SEM). For MWCNTs on silica, after 3 s irradiation, nanoscale welding with good quality can be achieved due to breaking C–C bonds and formation of new graphene layers. While welding junctions can be formed until 10 s for the MWCNTs on silicon, the difference of irradiation time to achieve welding is attributed to the difference of thermal conductivity for silica and silicon. As the irradiation time is prolonged up to 12.5 s, most of the MWCNTs are welded to a silicon substrate, which leads to their frameworks of tube walls on the silicon surface. This is because the accumulation of absorbed energy makes the temperature rise. Then chemical reactions among silicon, carbon and nitrogen occur. New chemical bonds of Si–N and Si–C achieve the welding between the MWCNTs and silicon. Vibration modes of Si3N4 appear at peaks of 363 cm−1 and 663 cm−1. There are vibration modes of SiC at peaks of 618 cm−1, 779 cm−1 and 973 cm−1. The experimental observation proves chemical reactions and the formation of Si3N4 and SiC by laser irradiation. Full article
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Open AccessArticle The Coupled Photothermal Reaction and Transport in a Laser Additive Metal Nanolayer Simultaneous Synthesis and Pattering for Flexible Electronics
Nanomaterials 2016, 6(1), 12; doi:10.3390/nano6010012
Received: 11 November 2015 / Revised: 14 December 2015 / Accepted: 5 January 2016 / Published: 8 January 2016
Cited by 4 | PDF Full-text (947 KB) | HTML Full-text | XML Full-text
Abstract
The Laser Direct Synthesis and Patterning (LDSP) technology has advantages in terms of processing time and cost compared to nanomaterials-based laser additive microfabrication processes. In LDSP, a scanning laser on the substrate surface induces chemical reactions in the reactive liquid solution and selectively
[...] Read more.
The Laser Direct Synthesis and Patterning (LDSP) technology has advantages in terms of processing time and cost compared to nanomaterials-based laser additive microfabrication processes. In LDSP, a scanning laser on the substrate surface induces chemical reactions in the reactive liquid solution and selectively deposits target material in a preselected pattern on the substrate. In this study, we experimentally investigated the effect of the processing parameters and type and concentration of the additive solvent on the properties and growth rate of the resulting metal film fabricated by this LDSP technology. It was shown that reactive metal ion solutions with substantial viscosity yield metal films with superior physical properties. A numerical analysis was also carried out the first time to investigate the coupled opto-thermo-fluidic transport phenomena and the effects on the metal film growth rate. To complete the simulation, the optical properties of the LDSP deposited metal film with a variety of thicknesses were measured. The characteristics of the temperature field and the thermally induced flow associated with the moving heat source are discussed. It was shown that the processing temperature range of the LDSP is from 330 to 390 K. A semi-empirical model for estimating the metal film growth rate using this process was developed based on these results. From the experimental and numerical results, it is seen that, owing to the increased reflectivity of the silver film as its thickness increases, the growth rate decreases gradually from about 40 nm at initial to 10 nm per laser scan after ten scans. This self-controlling effect of LDSP process controls the thickness and improves the uniformity of the fabricated metal film. The growth rate and resulting thickness of the metal film can also be regulated by adjustment of the processing parameters, and thus can be utilized for controllable additive nano/microfabrication. Full article
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Open AccessArticle Effects of Annealing Temperature on Properties of Ti-Ga–Doped ZnO Films Deposited on Flexible Substrates
Nanomaterials 2015, 5(4), 1831-1839; doi:10.3390/nano5041831
Received: 8 October 2015 / Revised: 20 October 2015 / Accepted: 29 October 2015 / Published: 3 November 2015
Cited by 6 | PDF Full-text (2348 KB) | HTML Full-text | XML Full-text
Abstract
An investigation is performed into the optical, electrical, and microstructural properties of Ti-Ga–doped ZnO films deposited on polyimide (PI) flexible substrates and then annealed at temperatures of 300 °C, 400 °C, and 450 °C, respectively. The X-ray diffraction (XRD) analysis results show that
[...] Read more.
An investigation is performed into the optical, electrical, and microstructural properties of Ti-Ga–doped ZnO films deposited on polyimide (PI) flexible substrates and then annealed at temperatures of 300 °C, 400 °C, and 450 °C, respectively. The X-ray diffraction (XRD) analysis results show that all of the films have a strong (002) Ga doped ZnO (GZO) preferential orientation. As the annealing temperature is increased to 400 °C, the optical transmittance increases and the electrical resistivity decreases. However, as the temperature is further increased to 450 °C, the transmittance reduces and the resistivity increases due to a carbonization of the PI substrate. Finally, the crystallinity of the ZnO film improves with an increasing annealing temperature only up to 400 °C and is accompanied by a smaller crystallite size and a lower surface roughness. Full article
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Review

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Open AccessReview Copper Nanowires and Their Applications for Flexible, Transparent Conducting Films: A Review
Nanomaterials 2016, 6(3), 47; doi:10.3390/nano6030047
Received: 31 December 2015 / Revised: 26 February 2016 / Accepted: 2 March 2016 / Published: 9 March 2016
Cited by 16 | PDF Full-text (3248 KB) | HTML Full-text | XML Full-text
Abstract
Cu nanowires (NWs) are attracting considerable attention as alternatives to Ag NWs for next-generation transparent conductors, replacing indium tin oxide (ITO) and micro metal grids. Cu NWs hold great promise for low-cost fabrication via a solution-processed route and show preponderant optical, electrical, and
[...] Read more.
Cu nanowires (NWs) are attracting considerable attention as alternatives to Ag NWs for next-generation transparent conductors, replacing indium tin oxide (ITO) and micro metal grids. Cu NWs hold great promise for low-cost fabrication via a solution-processed route and show preponderant optical, electrical, and mechanical properties. In this study, we report a summary of recent advances in research on Cu NWs, covering the optoelectronic properties, synthesis routes, deposition methods to fabricate flexible transparent conducting films, and their potential applications. This review also examines the approaches on protecting Cu NWs from oxidation in air environments. Full article
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Other

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Open AccessErratum Erratum: Tsai, S.-L.; et al. The Coupled Photothermal Reaction and Transport in a Laser Additive Metal Nanolayer Simultaneous Synthesis and Pattering for Flexible Electronics. Nanomaterials 2016, 6, 12
Nanomaterials 2016, 6(4), 62; doi:10.3390/nano6040062
Received: 4 April 2016 / Revised: 6 April 2016 / Accepted: 7 April 2016 / Published: 7 April 2016
PDF Full-text (495 KB) | HTML Full-text | XML Full-text
Abstract
Due to an error during production, the Figure 7b in the published paper [1] was incorrect. The correct figure is as follows:[...] Full article
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Figure 7

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