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Publications (10 of 152) Show all publications
Quellmalz, A., Smith, A. D., Elgammal, K., Fan, X., Delin, A., Östling, M., . . . Niklaus, F. (2018). Influence of Humidity on Contact Resistance in Graphene Devices. ACS Applied Materials and Interfaces, 10(48), 41738-41746
Open this publication in new window or tab >>Influence of Humidity on Contact Resistance in Graphene Devices
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2018 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 48, p. 41738-41746Article in journal (Refereed) Published
Abstract [en]

The electrical contact resistance at metal–graphene interfaces can significantly degrade the properties of graphene devices and is currently hindering the full exploitation of graphene’s potential. Therefore, the influence of environmental factors, such as humidity, on the metal–graphene contact resistance is of interest for all graphene devices that operate without hermetic packaging. We experimentally studied the influence of humidity on bottom-contacted chemical-vapor-deposited (CVD) graphene–gold contacts, by extracting the contact resistance from transmission line model (TLM) test structures. Our results indicate that the contact resistance is not significantly affected by changes in relative humidity (RH). This behavior is in contrast to the measured humidity sensitivity  of graphene’s sheet resistance. In addition, we employ density functional theory (DFT) simulations to support our experimental observations. Our DFT simulation results demonstrate that the electronic structure of the graphene sheet on top of silica is much more sensitive to adsorbed water molecules than the charge density at the interface between gold and graphene. Thus, we predict no degradation of device performance by alterations in contact resistance when such contacts are exposed to humidity. This knowledge underlines that bottom-contacting of graphene is a viable approach for a variety of graphene devices and the back end of the line integration on top of conventional integrated circuits.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
Keywords
graphene, bottom-contact, contact resistance, humidity sensitivity, integration, sheet resistance
National Category
Nano Technology Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-232554 (URN)10.1021/acsami.8b10033 (DOI)
Note

QC 20181207

Available from: 2018-07-25 Created: 2018-07-25 Last updated: 2018-12-07Bibliographically approved
Redzwan, S., Velander, J., Perez, M. D., Asan, N. B., Rajabi, M., Niklaus, F., . . . Augustine, R. (2018). Initial in-vitro trial for intra-cranial pressure monitoring using subdermal proximity-coupled split-ring resonator. In: IMBioc 2018 - 2018 IEEE/MTT-S International Microwave Biomedical Conference: . Paper presented at 2018 IEEE/MTT-S International Microwave Biomedical Conference, IMBioc 2018, Pennsylvania Convention CenterPhiladelphia, United States, 14 June 2018 through 15 June 2018 (pp. 73-75). Institute of Electrical and Electronics Engineers (IEEE), Article ID 8428854.
Open this publication in new window or tab >>Initial in-vitro trial for intra-cranial pressure monitoring using subdermal proximity-coupled split-ring resonator
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2018 (English)In: IMBioc 2018 - 2018 IEEE/MTT-S International Microwave Biomedical Conference, Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 73-75, article id 8428854Conference paper, Published paper (Refereed)
Abstract [en]

Intra cranial pressure (ICP) monitoring is used in treating severe traumatic brain injury (TBI) patients. All current clinical available measurement methods are invasive presenting considerable social costs. This paper presents a preliminary investigation of the feasibility of ICP monitoring using an innovative microwave-based non-invasive approach. A phantom mimicking the dielectric characteristics of human tissues of the upper part of the head at low microwave frequencies is employed together to a proof-of-concept prototype based on the proposed approach consisting in a readout system and a sub-dermally implanted passive device, both based in split ring resonator techniques. This study shows the potential of our approach to detect two opposite pressure variation stages inside the skull. The employed phantom model needs to be improved to support finer variations in the pressure and better phantom parts, principally for the skull mimic and the loss tangent of all mimics.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2018
Keywords
Biocompatible, Intra cranial pressure, Microwave technique, Split ring resonator (SRR) sensor
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:kth:diva-234095 (URN)10.1109/IMBIOC.2018.8428854 (DOI)2-s2.0-85052400710 (Scopus ID)9781538659182 (ISBN)
Conference
2018 IEEE/MTT-S International Microwave Biomedical Conference, IMBioc 2018, Pennsylvania Convention CenterPhiladelphia, United States, 14 June 2018 through 15 June 2018
Note

QC 20180905

Available from: 2018-09-05 Created: 2018-09-05 Last updated: 2018-09-05Bibliographically approved
Dubois, V. J., Raja, S. N., Gehring, P., Caneva, S., van der Zant, H. S. J., Niklaus, F. & Stemme, G. (2018). Massively parallel fabrication of crack-defined gold break junctions featuring sub-3 nm gaps for molecular devices. Nature Communications, 9, Article ID 3433.
Open this publication in new window or tab >>Massively parallel fabrication of crack-defined gold break junctions featuring sub-3 nm gaps for molecular devices
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2018 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 9, article id 3433Article in journal (Refereed) Published
Abstract [en]

Break junctions provide tip-shaped contact electrodes that are fundamental components of nano and molecular electronics. However, the fabrication of break junctions remains notoriously time-consuming and difficult to parallelize. Here we demonstrate true parallel fabrication of gold break junctions featuring sub-3 nm gaps on the wafer-scale, by relying on a novel self-breaking mechanism based on controlled crack formation in notched bridge structures. We achieve fabrication densities as high as 7 million junctions per cm(2), with fabrication yields of around 7% for obtaining crack-defined break junctions with sub-3 nm gaps of fixed gap width that exhibit electron tunneling. We also form molecular junctions using dithiol-terminated oligo(phenylene ethynylene) (OPE3) to demonstrate the feasibility of our approach for electrical probing of molecules down to liquid helium temperatures. Our technology opens a whole new range of experimental opportunities for nano and molecular electronics applications, by enabling very large-scale fabrication of solid-state break junctions.

Place, publisher, year, edition, pages
Nature Publishing Group, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-234594 (URN)10.1038/s41467-018-05785-2 (DOI)000442594800035 ()30143636 (PubMedID)2-s2.0-85052211020 (Scopus ID)
Note

QC 20180914

Available from: 2018-09-14 Created: 2018-09-14 Last updated: 2018-09-14Bibliographically approved
Errando-Herranz, C., Edinger, P., Colangelo, M., Björk, J., Ahmed, S., Stemme, G., . . . Gylfason, K. B. (2018). New dynamic silicon photonic components enabled by MEMS technology. In: Proceedings Volume 10537, Silicon Photonics XIII: . Paper presented at Silicon Photonics XIII 2018, San Francisco, United States, 29 January 2018 through 1 February 2018. SPIE - International Society for Optical Engineering, 10537, Article ID 1053711.
Open this publication in new window or tab >>New dynamic silicon photonic components enabled by MEMS technology
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2018 (English)In: Proceedings Volume 10537, Silicon Photonics XIII, SPIE - International Society for Optical Engineering, 2018, Vol. 10537, article id 1053711Conference paper, Published paper (Refereed)
Abstract [en]

Silicon photonics is the study and application of integrated optical systems which use silicon as an optical medium, usually by confining light in optical waveguides etched into the surface of silicon-on-insulator (SOI) wafers. The term microelectromechanical systems (MEMS) refers to the technology of mechanics on the microscale actuated by electrostatic actuators. Due to the low power requirements of electrostatic actuation, MEMS components are very power efficient, making them well suited for dense integration and mobile operation. MEMS components are conventionally also implemented in silicon, and MEMS sensors such as accelerometers, gyros, and microphones are now standard in every smartphone. By combining these two successful technologies, new active photonic components with extremely low power consumption can be made. We discuss our recent experimental work on tunable filters, tunable fiber-to-chip couplers, and dynamic waveguide dispersion tuning, enabled by the marriage of silicon MEMS and silicon photonics.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2018
Series
Proceedings of SPIE - The International Society for Optical Engineering, ISSN 0277-786X ; 10537
Keywords
MEMS, silicon photonics, tuning, ring resonator, waveguide dispersion, surface grating coupler
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-225106 (URN)10.1117/12.2297588 (DOI)000448020000015 ()2-s2.0-85047395610 (Scopus ID)9781510615595 (ISBN)
Conference
Silicon Photonics XIII 2018, San Francisco, United States, 29 January 2018 through 1 February 2018
Projects
VR-HETXMEMSM&M
Funder
Swedish Research Council, 621-2012-5364Swedish Research Council, B0460801EU, European Research Council, 277879EU, European Research Council, 267528
Note

QC 20180404

Available from: 2018-03-28 Created: 2018-03-28 Last updated: 2018-11-12Bibliographically approved
Laakso, M. J., Bleiker, S. J., Liljeholm, J., Mårtensson, G. E., Asiatici, M., Fischer, A. C., . . . Niklaus, F. (2018). Through-Glass Vias for Glass Interposers and MEMS Packaging Applications Fabricated Using Magnetic Assembly of Microscale Metal Wires. IEEE Access, 6, 44306-44317
Open this publication in new window or tab >>Through-Glass Vias for Glass Interposers and MEMS Packaging Applications Fabricated Using Magnetic Assembly of Microscale Metal Wires
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2018 (English)In: IEEE Access, E-ISSN 2169-3536, Vol. 6, p. 44306-44317Article in journal (Refereed) Published
Abstract [en]

A through-glass via (TGV) provides a vertical electrical connection through a glass substrate. TGVs are used in advanced packaging solutions, such as glass interposers and wafer-level packaging of microelectromechanical systems (MEMS). However, TGVs are challenging to realize because via holes in glass typically do not have a sufficiently high-quality sidewall profile for super-conformal electroplating of metal into the via holes. To overcome this problem, we demonstrate here that the via holes can instead be filled by magnetically assembling metal wires into them. This method was used to produce TGVs with a typical resistance of 64 m Omega, which is comparable with other metal TGV types reported in the literature. In contrast to many TGV designs with a hollow center, the proposed TGVs can be more area efficient by allowing solder bump placement directly on top of the TGVs, which was demonstrated here using solder-paste jetting. The magnetic assembly process can be parallelized using an assembly robot, which was found to provide an opportunity for increased wafer-scale assembly speed. The aforementioned qualities of the magnetically assembled TGVs allow the realization of glass interposers and MEMS packages in different thicknesses without the drawbacks associated with the current TGV fabrication methods.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2018
Keywords
Chip scale packaging, femtosecond laser, glass interposer, laser ablation, multichip modules, robotic assembly, self-assembly, spin-on glass, thermal expansion, through-glass via, through-silicon vias, TSV
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-235465 (URN)10.1109/ACCESS.2018.2861886 (DOI)000444505800001 ()2-s2.0-85050982480 (Scopus ID)
Funder
Knut and Alice Wallenberg FoundationVINNOVA, 324189Swedish Foundation for Strategic Research , GMT14-0071 RIF14-0017
Note

QC 20180928

Available from: 2018-09-28 Created: 2018-09-28 Last updated: 2018-10-02Bibliographically approved
Laakso, M., Bleiker, S. J., Liljeholm, J., Mårtensson, G., Asiatici, M., Fischer, A. C., . . . Niklaus, F. (2018). Through-Glass Vias for MEMS Packaging. In: : . Paper presented at The Micronano System Workshop (MSW), 2018, Helsinki, Finland, 13-15 May.
Open this publication in new window or tab >>Through-Glass Vias for MEMS Packaging
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2018 (English)Conference paper, Oral presentation with published abstract (Other academic)
Abstract [en]

Novelty / Progress Claims We have developed a new method for fabrication of through-glass vias (TGVs). The method allows rapid filling of via holes with metal rods both in thin and thick glass substrates.

Background Vertical electrical feedthroughs in glass substrates, i.e. TGVs, are often required in wafer-scale packaging of MEMS that utilizes glass lids. The current methods of making TGVs have drawbacks that prevent the full utilization of the excellent properties of glass as a package material, e.g. low RF losses. Magnetic assembly has been used earlier to fabricate through-silicon vias (TSVs), and in this work we extend this method to realize TGVs [1].

Methods The entire TGV fabrication process is maskless, and the processes used include: direct patterning of wafer metallization using femtosecond laser ablation, magnetic-fieldassisted self-assembly of metal wires into via holes, and solder-paste jetting of bump bonds on TGVs.

Results We demonstrate that: (1) the magnetically assembled TGVs have a low resistance, which makes them suitable even for low-loss and high-current applications; (2) the magneticassembly process can be parallelized in order to increase the wafer-scale fabrication speed; (3) the magnetic assembly produces void-free metal filling for TGVs, which allows solder placement directly on top of the TGV for the purpose of high integration density; and (4) good thermal-expansion compatibility between TGV metals and glass substrates is possible with the right choice of materials, and several suitable metals-glass pairs are identified for possible improvement of package reliability [2].

[1] M. Laakso et al., IEEE 30th Int. Conf. on MEMS, 2017. DOI:10.1109/MEMSYS.2017.7863517

[2] M. Laakso et al., “Through-Glass Vias for Glass Interposers and MEMS Packaging Utilizing Magnetic Assembly of Microscale Metal Wires,” manuscript in preparatio

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-238647 (URN)
Conference
The Micronano System Workshop (MSW), 2018, Helsinki, Finland, 13-15 May
Note

QC 20181106

Available from: 2018-11-06 Created: 2018-11-06 Last updated: 2018-11-06Bibliographically approved
Schröder, S., Gatty, H. K., Stemme, G., Roxhed, N. & Niklaus, F. (2017). A low-cost nitric oxide gas sensor based on bonded gold wires. In: TRANSDUCERS 2017 - 19th International Conference on Solid-State Sensors, Actuators and Microsystems: . Paper presented at 19th International Conference on Solid-State Sensors, Actuators and Microsystems, TRANSDUCERS 2017, Kaohsiung, Taiwan, 18 June 2017 through 22 June 2017 (pp. 1457-1460). Institute of Electrical and Electronics Engineers (IEEE), Article ID 7994334.
Open this publication in new window or tab >>A low-cost nitric oxide gas sensor based on bonded gold wires
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2017 (English)In: TRANSDUCERS 2017 - 19th International Conference on Solid-State Sensors, Actuators and Microsystems, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 1457-1460, article id 7994334Conference paper, Published paper (Refereed)
Abstract [en]

In this paper we report of a novel and very simple fabrication method for realizing amperometric gas sensors using conventional wire bonding technology. Working and counter electrodes are made of 360 vertically standing bond wires, entirely manufactured by a fully automated, standard wire bonding tool. Our process enables standing bond wires with a length of 1.24 mm, resulting in an extremely high aspect-ratio of 50, thus effectively increasing the surface area of the working electrode. All gas sensor electrodes are embedded in a polymer-based, solid electrolyte. Therefore, laborious handling of liquid electrolytes can be avoided. Here, we report of a nitric oxide (NO) gas sensor that is capable of detecting NO gas concentrations down to the single-digit ppm range. The proposed approach demonstrates the feasibility towards a scalable and entire back-end fabrication concept for low-cost NO gas sensors.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2017
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-214452 (URN)10.1109/TRANSDUCERS.2017.7994334 (DOI)000426701400362 ()2-s2.0-85029388567 (Scopus ID)9781538627310 (ISBN)
Conference
19th International Conference on Solid-State Sensors, Actuators and Microsystems, TRANSDUCERS 2017, Kaohsiung, Taiwan, 18 June 2017 through 22 June 2017
Note

QC 20171211

Available from: 2017-09-14 Created: 2017-09-14 Last updated: 2018-03-22Bibliographically approved
Schröder, S., Rödjegård, H., Stemme, G. & Niklaus, F. (2017). A single wire large-area filament emitter for spectroscopic ethanol gas sensing fabricated using a wire bonding tool. In: TRANSDUCERS 2017 - 19th International Conference on Solid-State Sensors, Actuators and Microsystems: . Paper presented at 19th International Conference on Solid-State Sensors, Actuators and Microsystems, TRANSDUCERS 2017, Kaohsiung, Taiwan, 18 June 2017 through 22 June 2017 (pp. 315-318). IEEE, Article ID 7994052.
Open this publication in new window or tab >>A single wire large-area filament emitter for spectroscopic ethanol gas sensing fabricated using a wire bonding tool
2017 (English)In: TRANSDUCERS 2017 - 19th International Conference on Solid-State Sensors, Actuators and Microsystems, IEEE, 2017, p. 315-318, article id 7994052Conference paper, Published paper (Refereed)
Abstract [en]

Non-dispersive infrared (NDIR) gas spectroscopy is a highly accurate optical gas sensing technology, which has been implemented in various industrial applications. However NDIR systems remain too expensive for many consumer and automotive apphcations. The cost of the infrared (IR) emitter component is a substantial part of the total system cost. In this paper we report of a single filament IR emitter that is fabricated using wire bonding technology. Our fabrication approach offers the prospect of a fully automated assembly by means of utihzing a wire bonding tool to integrate the single filament to the MEMS structured silicon substrate. An apphcation-specific wire bond trajectory enables the mechanical attachment of the filament to form the meander-shaped emitter with a total area of 1 mm2. The fabricated IR emitter utilizes a Kanthal (FeCrAl) filament with very high thermal stability and excellent emitting properties under atmospheric conditions. The packaged IR emitter has been characterized using Fourier transform infrared (FTIR) spectroscopy to study the emitted IR spectrum with respect to the requirements of NDIR systems.

Place, publisher, year, edition, pages
IEEE, 2017
Keywords
NDIR, non-dispersive infrared gas sensing, ethanol gas sensing, breath alcohol sensing, infrared emitter, wire bonding, non-bondable wire materials, integration platform, Kanthal filament
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-214450 (URN)10.1109/TRANSDUCERS.2017.7994052 (DOI)000426701400080 ()2-s2.0-85029362985 (Scopus ID)978-1-5386-2732-7 (ISBN)
Conference
19th International Conference on Solid-State Sensors, Actuators and Microsystems, TRANSDUCERS 2017, Kaohsiung, Taiwan, 18 June 2017 through 22 June 2017
Funder
EU, European Research Council, 277879Swedish Research Council, 621-2011-4437VINNOVA, 2015-00402
Note

QC 20171211

Available from: 2017-09-14 Created: 2017-09-14 Last updated: 2018-03-23Bibliographically approved
Dubois, V. J., Niklaus, F. & Stemme, G. (2017). Design and fabrication of crack-junctions. MICROSYSTEMS & NANOENGINEERING, 3, Article ID UNSP 17042.
Open this publication in new window or tab >>Design and fabrication of crack-junctions
2017 (English)In: MICROSYSTEMS & NANOENGINEERING, ISSN 2055-7434, Vol. 3, article id UNSP 17042Article in journal (Refereed) Published
Abstract [en]

Nanogap electrodes consist of pairs of electrically conducting tips that exhibit nanoscale gaps. They are building blocks for a variety of applications in quantum electronics, nanophotonics, plasmonics, nanopore sequencing, molecular electronics, and molecular sensing. Crack-junctions (CJs) constitute a new class of nanogap electrodes that are formed by controlled fracture of suspended bridge structures fabricated in an electrically conducting thin film under residual tensile stress. Key advantages of the CJ methodology over alternative technologies are that CJs can be fabricated with wafer-scale processes, and that the width of each individual nanogap can be precisely controlled in a range from <2 to >100 nm. While the realization of CJs has been demonstrated in initial experiments, the impact of the different design parameters on the resulting CJs has not yet been studied. Here we investigate the influence of design parameters such as the dimensions and shape of the notches, the length of the electrode-bridge and the design of the anchors, on the formation and propagation of cracks and on the resulting features of the CJs. We verify that the design criteria yields accurate prediction of crack formation in electrode-bridges featuring a beam width of 280 nm and beam lengths ranging from 1 to 1.8 mu m. We further present design as well as experimental guidelines for the fabrication of CJs and propose an approach to initiate crack formation after release etching of the suspended electrode-bridge, thereby enabling the realization of CJs with pristine electrode surfaces.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2017
Keywords
arrays, crack-junctions, lithography, nanofabrication, nanogap electrodes, notches, optimization, tunneling junctions
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-217431 (URN)10.1038/micronano.2017.42 (DOI)000414166400001 ()
Note

QC 20171117

Available from: 2017-11-17 Created: 2017-11-17 Last updated: 2018-05-22Bibliographically approved
Smith, A. D., Elgammal, K., Fan, X., Lemme, M. C., Delin, A., Råsander, M., . . . Östling, M. (2017). Graphene-based CO2 sensing and its cross-sensitivity with humidity. RSC Advances, 7, 22329-22339
Open this publication in new window or tab >>Graphene-based CO2 sensing and its cross-sensitivity with humidity
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2017 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 7, p. 22329-22339Article in journal (Refereed) Published
Abstract [en]

We present graphene-based CO2 sensing and analyze its cross-sensitivity with humidity. In order to assess the selectivity of graphene-based gas sensing to various gases, measurements are performed in argon (Ar), nitrogen (N2), oxygen (O2), carbon dioxide (CO2), and air by selectively venting the desired gas from compressed gas bottles into an evacuated vacuum chamber. The sensors provide a direct electrical readout in response to changes in high concentrations, from these bottles, of CO2, O2, nitrogen and argon, as well as changes in humidity from venting atmospheric air. From the signal response to each gas species, the relative graphene sensitivity to each gas is extracted as a relationship between the percentage-change in graphene's resistance response to changes in vacuum chamber pressure. Although there is virtually no response from O2, N2 and Ar, there is a sizeable cross-sensitivity between CO2 and humidity occurring at high CO2 concentrations. However, under atmospheric concentrations of CO2, this cross-sensitivity effect is negligible – allowing for the use of graphene-based humidity sensing in atmospheric environments. Finally, charge density difference calculations, computed using density functional theory (DFT) are presented in order to illustrate the bonding of CO2 and water molecules on graphene and the alterations of the graphene electronic structure due to the interactions with the substrate and the molecules.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2017
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-206164 (URN)10.1039/C7RA02821K (DOI)
Note

QC 20170517

Available from: 2017-04-27 Created: 2017-04-27 Last updated: 2018-07-26
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-0525-8647

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