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Li, Y., Yang, X., Fu, Q., Rojas, R., Yan, M. & Berglund, L. (2018). Towards centimeter thick transparent wood through interface manipulation. Journal of Materials Chemistry A, 6(3), 1094-1101
Open this publication in new window or tab >>Towards centimeter thick transparent wood through interface manipulation
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2018 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, no 3, p. 1094-1101Article in journal (Refereed) Published
Abstract [en]

Transparent wood is an attractive structural material for energy-saving buildings due to its high optical transmittance, good thermal insulation, and high toughness. However, thick highly transparent wood is challenging to realize. In the current work, highly transparent wood (1.5 mm) with a transmittance of 92%, close to that of pure PMMA (95%), is demonstrated. The high transmittance was realized by interface manipulation through acetylation of wood template. Both experiments and electromagnetic modeling support that the improved transmittance is mainly due to elimination of interface debonding gap. By applying this method, a centimeter-thick transparent wood structure was obtained. The transparent wood could be used as a substrate for an optically tunable window by laminating a polymer dispersed liquid crystal (PDLC) film on top. The techniques demonstrated are a step towards the replacement of glass in smart windows and smart buildings.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2018
National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:kth:diva-222182 (URN)10.1039/c7ta09973h (DOI)000422949700040 ()2-s2.0-85040915327 (Scopus ID)
Note

QC 20180206

Available from: 2018-02-06 Created: 2018-02-06 Last updated: 2018-02-06Bibliographically approved
Fu, Q., Yan, M., Jungstedt, E., Yang, X., Li, Y. & Berglund, L. A. (2018). Transparent plywood as a load-bearing and luminescent biocomposite. Composites Science And Technology, 164, 296-303
Open this publication in new window or tab >>Transparent plywood as a load-bearing and luminescent biocomposite
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2018 (English)In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 164, p. 296-303Article in journal (Refereed) Published
Abstract [en]

Transparent wood (TW) structures in research studies were either thin and highly anisotropic or thick and isotropic but weak. Here, transparent plywood (TPW) laminates are investigated as load-bearing biocomposites with tunable mechanical and optical performances. Structure-property relationships are analyzed. The plies of TPW were laminated with controlled fiber directions and predetermined stacking sequence in order to control the directional dependence of modulus and strength, which would give improved properties in the weakest direction. Also, the angular dependent light scattering intensities were investigated and showed more uniform distribution. Luminescent TPW was prepared by incorporation of quantum dots (QDs) for potential lighting applications. TPW can be designed for large-scale use where multiaxial load-bearing performance is combined with new optical functionalities.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Transparent Wood, Nanotechnology, Biocomposite, Photonics
National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:kth:diva-233274 (URN)10.1016/j.compscitech.2018.06.001 (DOI)000440121700036 ()2-s2.0-85048381154 (Scopus ID)
Funder
EU, European Research Council, 742733
Note

QC 20180821

Available from: 2018-08-21 Created: 2018-08-21 Last updated: 2018-08-21Bibliographically approved
Li, Y., Fu, Q., Rojas, R., Yan, M., Lawoko, M. & Berglund, L. (2017). Lignin-Retaining Transparent Wood. ChemSusChem, 10(17), 3445-3451
Open this publication in new window or tab >>Lignin-Retaining Transparent Wood
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2017 (English)In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 10, no 17, p. 3445-3451Article in journal (Refereed) Published
Abstract [en]

Optically transparent wood, combining optical and mechanical performance, is an emerging new material for light-transmitting structures in buildings with the aim of reducing energy consumption. One of the main obstacles for transparent wood fabrication is delignification, where around 30wt% of wood tissue is removed to reduce light absorption and refractive index mismatch. This step is time consuming and not environmentally benign. Moreover, lignin removal weakens the wood structure, limiting the fabrication of large structures. A green and industrially feasible method has now been developed to prepare transparent wood. Up to 80wt% of lignin is preserved, leading to a stronger wood template compared to the delignified alternative. After polymer infiltration, a high-lignin-content transparent wood with transmittance of 83%, haze of 75%, thermal conductivity of 0.23WmK(-1), and work-tofracture of 1.2MJm(-3) (a magnitude higher than glass) was obtained. This transparent wood preparation method is efficient and applicable to various wood species. The transparent wood obtained shows potential for application in energy-saving buildings.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2017
Keywords
building materials, delignification, energy saving, lignin, wood
National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:kth:diva-214873 (URN)10.1002/cssc.201701089 (DOI)000410136800018 ()2-s2.0-85029175474 (Scopus ID)
Note

QC 20171024

Available from: 2017-10-24 Created: 2017-10-24 Last updated: 2018-02-26Bibliographically approved
Dai, J., Ding, F., Bozhevolnyi, S. I. & Yan, M. (2017). Ultrabroadband super-Planckian radiative heat transfer with artificial continuum cavity states in patterned hyperbolic metamaterials. Physical Review B, 95(24), Article ID 245405.
Open this publication in new window or tab >>Ultrabroadband super-Planckian radiative heat transfer with artificial continuum cavity states in patterned hyperbolic metamaterials
2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, no 24, article id 245405Article in journal (Refereed) Published
Abstract [en]

Localized cavity resonances due to nanostructures at material surfaces can greatly enhance radiative heat transfer (RHT) between two closely placed bodies owing to stretching of cavity states in momentum space beyond the light line. Based on such understanding, we numerically demonstrate the possibility of ultrabroadband super-Planckian RHT between two plates patterned with trapezoidal-shaped hyperbolic metamaterial (HMM) arrays. The phenomenon is rooted not only in HMM's high effective index for creating subwavelength resonators but also its extremely anisotropic isofrequency contour. The two properties enable one to create photonic bands with a high spectral density to populate a desired thermal radiation window. At submicron gap sizes between such two plates, the artificial continuum states extend outside the light cone, tremendously increasing overall RHT. Our study reveals that structured HMM offers unprecedented potential in achieving a controllable super-Planckian radiative heat transfer for thermal management at nanoscale.

Place, publisher, year, edition, pages
American Physical Society, 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-210471 (URN)10.1103/PhysRevB.95.245405 (DOI)000402929900006 ()2-s2.0-85023188371 (Scopus ID)
Funder
Swedish Research Council, 2011-4526
Note

QC 20170705

Available from: 2017-07-05 Created: 2017-07-05 Last updated: 2018-09-19Bibliographically approved
Li, Y., Fu, Q., Yu, S., Yan, M. & Berglund, L. (2016). Optically Transparent Wood from a Nanoporous Cellulosic Template: Combining Functional and Structural Performance. Biomacromolecules, 17(4), 1358-1364
Open this publication in new window or tab >>Optically Transparent Wood from a Nanoporous Cellulosic Template: Combining Functional and Structural Performance
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2016 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 17, no 4, p. 1358-1364Article in journal (Refereed) Published
Abstract [en]

Optically transparent wood (TW) with transmittance as high as 85% and haze of 71% was obtained using a delignified nanoporous wood template. The template was prepared by removing the light-absorbing lignin component, creating nanoporosity in the wood cell wall. Transparent wood was prepared by successful impregnation of lumen and the nanoscale cellulose fiber network in the cell wall with refractive-index-matched prepolymerized methyl methacrylate (MMA). During the process, the hierarchical wood structure was preserved. Optical properties of TW are tunable by changing the cellulose volume fraction. The synergy between wood and PMMA was observed for mechanical properties. Lightweight and strong transparent wood is a potential candidate for lightweight low-cost, light-transmitting buildings and transparent solar cell windows.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
Keywords
Solar-Cells, Nanofiber Paper, Scattering, Efficient, Fibers, Film
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-187074 (URN)10.1021/acs.biomac.6b00145 (DOI)000374076900013 ()26942562 (PubMedID)2-s2.0-84964600674 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20160518

Available from: 2016-05-18 Created: 2016-05-17 Last updated: 2018-02-21Bibliographically approved
Gong, H., Chen, X., Qu, Y., Li, Q., Yan, M. & Qiu, M. (2016). Photothermal Switching Based on Silicon Mach-Zehnder Interferometer Integrated with Light Absorber. IEEE Photonics Journal, 8(2), Article ID 7456199.
Open this publication in new window or tab >>Photothermal Switching Based on Silicon Mach-Zehnder Interferometer Integrated with Light Absorber
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2016 (English)In: IEEE Photonics Journal, ISSN 1097-5764, E-ISSN 1943-0655, Vol. 8, no 2, article id 7456199Article in journal (Refereed) Published
Abstract [en]

We present an all-optical switch based on photothermal effects in a silicon Mach-Zehnder interferometer (MZI) integrated with a light absorber. The metal-insulator-metal light absorber located near the longer arm of the asymmetric MZI efficiently converts infrared light to heat. Pumped by a continuous-wave 1064-nm laser, the spectral transmittance of the fully etched strip waveguide (half-etched rib waveguide) MZI can be tuned with an efficiency of 38 pm/mW (98.5 pm/mW). Dynamic switching experiments show that the rise/fall time constant of the output probe light is 11.45/10.98 μs (8.25/7.13 μs) for the fully etched (half-etched) MZI.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2016
Keywords
Fabrication and charaterization, Integrated nanophotonic systems, Photothermal effect, Silicon nanophotonics, Waveguides
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-187184 (URN)10.1109/JPHOT.2016.2550319 (DOI)000388089100050 ()2-s2.0-84964692040 (Scopus ID)
Note

QC 20160520

Available from: 2016-05-20 Created: 2016-05-18 Last updated: 2017-11-30Bibliographically approved
Dai, J., Dyakov, S. A. & Yan, M. (2016). Radiative heat transfer between two dielectric-filled metal gratings. PHYSICAL REVIEW B, 93(15), Article ID 155403.
Open this publication in new window or tab >>Radiative heat transfer between two dielectric-filled metal gratings
2016 (English)In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, no 15, article id 155403Article in journal (Refereed) Published
Abstract [en]

Nanoscale surface corrugation is known to be able to drastically enhance radiative heat transfer between two metal plates. Here we numerically calculate the radiative heat transfer between two dielectric-filled metal gratings at dissimilar temperatures based on a scattering approach. It is demonstrated that, compared to unfilled metal gratings, the heat flux for a fixed geometry can be further enhanced, by up to 650% for the geometry separated by a vacuum gap of g = 1 mu m and temperature values concerned in our study. The enhancement in radiative heat transfer is found to depend on refractive index of the filling dielectric, the specific grating temperatures, and naturally the gap size between the two gratings. The enhancement can be understood through examining the transmission factor spectra, especially the spectral locations of the spoof surface plasmon polariton modes. Of more practical importance, it's shown that the radiative heat flux can exceed that between two planar SiC plates with same thickness, separation, and temperature settings over a wide temperature range. This reaffirms that one can harness rich electromagnetic modal properties in nanostructured materials for efficient thermal management at nanoscale.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-185983 (URN)10.1103/PhysRevB.93.155403 (DOI)000373569000003 ()2-s2.0-84963747850 (Scopus ID)
Note

QC 20160509

Available from: 2016-05-09 Created: 2016-04-29 Last updated: 2016-11-07Bibliographically approved
Lobov, G. S., Zhao, Y., Marinins, A., Yan, M., Li, J., Toprak, M. S., . . . Popov, S. (2015). Electric field induced optical anisotropy of P3HT nanofibers in a liquid solution. Optical Materials Express, 5(11), 2642-2647
Open this publication in new window or tab >>Electric field induced optical anisotropy of P3HT nanofibers in a liquid solution
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2015 (English)In: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 5, no 11, p. 2642-2647Article in journal (Refereed) Published
Abstract [en]

The nanofiber morphology of regioregular Poly-3- hexylthiophene (P3HT) is a 1D crystalline structure organized by π - π stacking of the backbone chains. In this study, we report the impact of electric field on the orientation and optical properties of P3HT nanofibers dispersed in liquid solution. We demonstrate that alternating electric field aligns nanofibers, whereas static electric field forces them to migrate towards the cathode. The alignment of nanofibers introduces anisotropic optical properties, which can be dynamically manipulated until the solvent has evaporated. Time resolved spectroscopic measurements revealed that the electro-optical response time decreases significantly with the magnitude of applied electric field. Thus, for electric field 1.3 V ·μm-1 the response time was measured as low as 20 ms, while for 0.65 V ·μm-1 it was 110-150 ms. Observed phenomenon is the first mention of P3HT supramolecules associated with electrooptical effect. Proposed method provides real time control over the orientation of nanofibers, which is a starting point for a novel practical implementation. With further development P3HT nanofibers can be used individually as an anisotropic solution or as an active component in a guest-host system.

Place, publisher, year, edition, pages
Optical Society of America, 2015
Keywords
Anisotropy, Electric fields, Nanofibers, Real time control, Alternating electric field, Anisotropic optical properties, Crystalline structure, Electric field induced, Electrooptical response, Poly-3-hexylthiophene, Spectroscopic measurements, Static electric fields, Optical properties
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-181212 (URN)10.1364/OME.5.002642 (DOI)000364467700027 ()2-s2.0-84947753945 (Scopus ID)
Note

QC 20160210

Available from: 2016-02-10 Created: 2016-01-29 Last updated: 2017-12-29Bibliographically approved
Lobov, G. S., Zhao, Y., Marinins, A., Yan, M., Li, J., Toprak, M., . . . Popov, S. Y. (2015). Electro-optical response of P3HT nanofibers in liquid solution. In: Asia Communications and Photonics Conference, ACPC 2015: . Paper presented at Asia Communications and Photonics Conference, ACPC 2015, 19 November 2015 through 23 November 2015.
Open this publication in new window or tab >>Electro-optical response of P3HT nanofibers in liquid solution
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2015 (English)In: Asia Communications and Photonics Conference, ACPC 2015, 2015Conference paper, Published paper (Refereed)
Abstract [en]

AC electric poling introduces in P3HT nanofibers anisotropic electro-optical response and birefringence. Along with birefringence, such material exhibits strong amplitude modulation which makes it more efficient alternative to liquid crystals. © 2015 OSA.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-195160 (URN)2-s2.0-84971612086 (Scopus ID)9781943580064 (ISBN)
Conference
Asia Communications and Photonics Conference, ACPC 2015, 19 November 2015 through 23 November 2015
Note

Correspondence Address: Lobov, G.S.; School of Information and Communication Technology, KTH-Royal Institute of TechnologySweden; email: lobov@kth.se. QC 20161108

Available from: 2016-11-08 Created: 2016-11-02 Last updated: 2016-11-08Bibliographically approved
Dai, J., Dyakov, S. A. & Yan, M. (2015). Enhanced near-field radiative heat transfer between corrugated metal plates: Role of spoof surface plasmon polaritons. Physical Review B. Condensed Matter and Materials Physics, 92(3), Article ID 035419.
Open this publication in new window or tab >>Enhanced near-field radiative heat transfer between corrugated metal plates: Role of spoof surface plasmon polaritons
2015 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 3, article id 035419Article in journal (Refereed) Published
Abstract [en]

We demonstrate with the finite-difference time-domain method that radiative heat transfer between two parallel gold plates can be significantly enhanced by engraving periodic grooves with a subwavelength width on the plate surfaces. The enhancement increases with a decrease in the separation distance at near-field regime and it can be further efficiently improved by having a supercell with multiple grooves with different depths. We attribute this near-field enhancement to coupling of thermally excited spoof surface plasmon polaritons, a type of artificial surface wave inherent to structured metal surfaces [J. B. Pendry, L. Martin-Moreno, and F. J. Garcia-Vidal, Science 305, 847 (2004)]. The frequency-dependent contribution to the heat transfer, or transmission-factor spectrum, is confirmed by calculating the dispersion relation of guided modes by the two parallel corrugated plates through a finite-element method. Especially, the photonic density of states derived from the dispersion relation is found to have excellent agreement to the transmission-factor spectrum.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-171887 (URN)10.1103/PhysRevB.92.035419 (DOI)000358031300002 ()
Funder
Swedish Research Council, 621-2011-4526
Note

QC 20150814

Available from: 2015-08-14 Created: 2015-08-10 Last updated: 2017-12-04Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3368-9786

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