| 1. |
- Kim, Seong-Min, et al.
(författare)
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High-performance, polymer-based direct cellular interfaces for electrical stimulation and recording
- 2018
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Ingår i: NPG ASIA MATERIALS. - : NATURE PUBLISHING GROUP. - 1884-4049 .- 1884-4057. ; 10, s. 255-265
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Tidskriftsartikel (refereegranskat)abstract
- Due to the trade-off between their electrical/electrochemical performance and underwater stability, realizing polymer-based, high-performance direct cellular interfaces for electrical stimulation and recording has been very challenging. Herein, we developed transparent and conductive direct cellular interfaces based on a water-stable, high-performance poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) film via solvent-assisted crystallization. The crystallized PEDOT:PSS on a polyethylene terephthalate (PET) substrate exhibited excellent electrical/electrochemical/optical characteristics, long-term underwater stability without film dissolution/delamination, and good viability for primarily cultured cardiomyocytes and neurons over several weeks. Furthermore, the highly crystallized, nanofibrillar PEDOT:PSS networks enabled dramatically enlarged surface areas and electrochemical activities, which were successfully employed to modulate cardiomyocyte beating via direct electrical stimulation. Finally, the high-performance PEDOT:PSS layer was seamlessly incorporated into transparent microelectrode arrays for efficient, real-time recording of cardiomyocyte action potentials with a high signal fidelity. All these results demonstrate the strong potential of crystallized PEDOT:PSS as a crucial component for a variety of versatile bioelectronic interfaces.
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| 2. |
- Jo, Min-Seung, et al.
(författare)
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Aligned CuO nanowire array for a high performance visible light photodetector
- 2022
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Recently, copper oxide (CuO) has drawn much attention as a promising material in visible light photodetection with its advantages in ease of nanofabrication. CuO allows a variety of nanostructures to be explored to enhance the optoelectrical performance such as photogenerated carriers scattering and bandgap engineering. However, previous researches neglect in-depth analysis of CuO's light interaction effects, restrictively using random orientation such as randomly arranged nanowires, single nanowires, and dispersed nanoparticles. Here, we demonstrate an ultra-high performance CuO visible light photodetector utilizing perfectly-aligned nanowire array structures. CuO nanowires with 300 nm-width critical dimension suppressed carrier transport in the dark state and enhanced the conversion of photons to carriers; additionally, the aligned arrangement of the nanowires with designed geometry improved the light absorption by means of the constructive interference effect. The proposed nanostructures provide advantages in terms of dark current, photocurrent, and response time, showing unprecedentedly high (state-of-the-art) optoelectronic performance, including high values of sensitivity (S = 172.21%), photo-responsivity (R = 16.03 A/W, lambda = 535 nm), photo-detectivity (D* = 7.78 x 10(11) Jones), rise/decay time (tau(r)/tau(d) = 0.31 s/1.21 s).
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| 3. |
- Kim, Jong Min, et al.
(författare)
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A novel textile-like carbon wrapping for highperformance silicon anodes in lithium-ion batteries
- 2018
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 6:26, s. 12475-12483
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Tidskriftsartikel (refereegranskat)abstract
- Carbon coating is essential for active materials in electrochemical applications that are often insulators or poor conductors. A conventional conformal carbon coating can hinder the ion diffusion to and from the active material and form an isolated conducting network. Especially, active materials with very large volume expansion, e.g., silicon, can destroy the carbon coating during lithiation, which makes conformal carbon coating inappropriate. This paper presents a novel textile-like carbon wrapping that provides efficient electron and ion diffusion paths via a wide-range carbon network and pores. The textile-like carbon wrapping can reduce the electrical contact loss during cycling through the wide-range carbon network, which makes it a suitable carbon coating for materials that undergo volume expansion. A textile-like carbon-wrapped silicon is formed by pyrolysis of a dried suspension of silicon nanoparticles mixed with enzymatically hydrolyzed cellulose nanofibers. It shows excellent electrochemical performance compared to a conformal carbon-coated silicon. It exhibits a reversible specific capacity of 680mA h g(-1) at 8.0 A g(-1) and shows excellent cycling stability (capacity retention of 94.5% after 500 cycles at 2.0 A g(-1)) with high Si content (95.71 wt%). Therefore, this novel textile-like carbon wrapping can be utilized in many electrochemical applications instead of the conventional carbon coating, especially for active materials that undergo large volume expansion.
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| 4. |
- Lee, Jung Soo, et al.
(författare)
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Stiffness measurement of nanosized liposomes using solid-state nanopore sensor with automated recapturing platform
- 2019
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Ingår i: Electrophoresis. - : Wiley. - 0173-0835 .- 1522-2683. ; 40:9, s. 1337-1344
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a method to gauge the stiffness of nanosized liposomes – a nanoscale vesicle – using a custom-made recapture platform coupled to a solid-state nanopore sensor. The recapture platform electrically profiles a given liposome vesicle multiple times through automated reversal of the voltage polarity immediately following a translocation instance to re-translocate the same analyte through the nanopore – provides better statistical insight at the molecular level by analyzing the same particle multiple times compared to conventional nanopore platforms. The capture frequency depends on the applied voltage with lower voltages (i.e., 100 mV) permitting higher recapture instances than at higher voltages (>200 mV) since the probability of particles exiting the nanopore capture radius increases with voltage. The shape deformation was inferred by comparing the normalized relative current blockade ((Formula presented.) at the two voltage polarities to that of a rigid particle, i.e., polystyrene beads. We found that liposomes deform to adopt a prolate shape at higher voltages. This platform can be further applied to investigate the stiffness of other types of soft matters, e.g., virus, exosomes, endosomes, and accelerate the potential studies in pharmaceutics for increasing the drug packing and unpacking mechanism by controlling the stiffness of the drug vesicles.
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| 5. |
- Shin, Su Ryon, et al.
(författare)
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Layer-by-Layer Assembly of 3D Tissue Constructs with Functionalized Graphene
- 2014
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 24:39, s. 6136-6144
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Tidskriftsartikel (refereegranskat)abstract
- Carbon-based nanomaterials have been considered promising candidates to mimic certain structure and function of native extracellular matrix materials for tissue engineering. Significant progress has been made in fabricating carbon nanoparticle-incorporated cell culture substrates, but only a limited number of studies have been reported on the development of 3D tissue constructs using these nanomaterials. Here, a novel approach to engineer 3D multilayer constructs using layer-by-layer (LbL) assembly of cells separated with self-assembled graphene oxide (GO)-based thin films is presented. The GO-based structures are shown to serve as cell adhesive sheets that effectively facilitate the formation of multilayer cell constructs with interlayer connectivity. By controlling the amount of GO deposited in forming the thin films, the thickness of the multilayer tissue constructs could be tuned with high cell viability. Specifically, this approach could be useful for creating dense and tightly connected cardiac tissues through the co-culture of cardiomyocytes and other cell types. In this work, the fabrication of stand-alone multilayer cardiac tissues with strong spontaneous beating behavior and programmable pumping properties is demonstrated. Therefore, this LbL-based cell construct fabrication approach, utilizing GO thin films formed directly on cell surfaces, has great potential in engineering 3D tissue structures with improved organization, electrophysiological function, and mechanical integrity.
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| 6. |
- Kim, Hyeri, et al.
(författare)
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Toward Sustaining Bioplastics : Add a Pinch of Seasoning
- 2023
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 11:5, s. 1846-1856
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Tidskriftsartikel (refereegranskat)abstract
- Modern society can no longer sustain accumulating plastic pollution without intervention; plastic waste has even found its way into the food that we consume. Unfortunately, biodegradable alternatives lack sound commercial and economic distinctiveness because mechanical strength and biodegradability are typically mutually exclusive. Inspired by fine cuisine, we introduce a novel synthetic method, referred to as “seasoning”, which consists of adding a minimal amount of a biobased multifunctional monomer to pinch the amorphous domains of poly(butylene succinate). Seasoning with only 0.03 mol % of a biobased monomer led to a significantly improved oxygen barrier, high strength (86 MPa), and excellent elongation at break (654%). To the best of our knowledge, this “seasoning” approach with the significant property improvement provided is unique in the bioplastics research field. The proposed approach is highly scalable, relies on existing industrial production, and has the potential to expand current biodegradable plastic applications through its simplicity.
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| 7. |
- Kim, Su Min, et al.
(författare)
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Distributed MAC Based on Adaptive Sensing Period Adjustment in Overlay Cognitive Radio Networks
- 2013
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Ingår i: Proceedings of IEEE Asia-Pacific Wireless Communications Symposium (APWCS) 2013, Seoul, Korea.
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose distributed MAC protocols based on adaptive sensing period adjustment in overlay cognitive radio (CR) networks. The proposed MAC protocols adjust the sensing period based on both primary sensing and secondary data channel information at each CR user. A user with the shortest adjusted sensing period accesses to the channel in a distributed manner through an exchange of RTS/CTS messages. We propose two kinds of sensing period adjustment (SPA) protocols: logarithmic SPA (LSPA) and exponential SPA (ESPA) protocols. Through Monte-Carlo simulations, we evaluate the performance of the proposed protocols in terms of spectral efficiency and collision probability. Numerical results show that the collision probability is the most dominant factor to determine the spectral efficiency. The proposed ESPA protocol efficiently reduces the collision probability with a moderate increase of the sensing period.
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| 8. |
- Kwon, Kiwoong, et al.
(författare)
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Traffic-aware stateless multipath routing for fault-tolerance in IEEE 802.15.4 wireless mesh networks
- 2018
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Ingår i: Wireless networks. - : Springer. - 1022-0038 .- 1572-8196. ; 24:5, s. 1755-1774
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Tidskriftsartikel (refereegranskat)abstract
- Single-path routing is widely used in wireless networks due to low resource consumption. However, it is vulnerable to link failure because such a failure may adversely affect an entire path. To overcome this, multipath routing has been proposed providing fault-tolerance. In this paper, we propose a novel multipath routing protocol called traffic-aware stateless multipath routing (TSMR) based on an overlaid tree topology comprising two topologies, namely, bounded degree tree (BDT) and root-oriented directional tree (RODT). BDT is strong on reducing routing overhead, and RODT is resilient against lossy links. By synergistically overlaying them, TSMR dynamically selects the local optimal path according to the given traffic flow and the failure on the primary path. In particular, TSMR enables stateless and low overhead routing despite multipath routing by keeping only one-hop neighbors to maintain multiple paths. To evaluate TSMR, we conducted simulations with a shadowing model reflecting lossy links, and compared with single and multipath routing protocols, such as ZTR, STR, AODV, and RPL. The simulation results show that the overall performance of TSMR surpasses that of others for packet delivery ratio, end-to-end delay, control overhead, memory consumption, and power consumption regardless of network size, number of sessions, and traffic flow.
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| 9. |
- Popovski, Petar, et al.
(författare)
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Wireless Access for Ultra-Reliable Low-Latency Communication (URLLC): Principles and Building Blocks
- 2018
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Ingår i: IEEE Network. - 1558-156X .- 0890-8044. ; 32:2, s. 16-23
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Tidskriftsartikel (refereegranskat)abstract
- Ultra-reliable low latency communication (URLLC) is an important new feature brought by 5G, with a potential to support a vast set of applications that rely on mission-critical links. In this article, we first discuss the principles for supporting URLLC from the perspective of the traditional assumptions and models applied in communication/information theory. We then discuss how these principles are applied in various elements of the system design, such as use of various diversity sources, design of packets and access protocols. The important messages are that there is a need to optimize the transmission of signaling information, as well as a need for a lean use of various sources of diversity.
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| 10. |
- Bang, I., et al.
(författare)
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Opportunistic user selection with adaptive jamming for secure communication in heterogeneous networks
- 2015
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Ingår i: IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC. - : IEEE conference proceedings. - 9781479949120 ; , s. 42-46
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose an opportunistic user selection criterion to obtain a multiuser diversity gain for secure communication. At the same time, we also propose a strategy for utilizing a small base station in heterogeneous networks as a helper or a jammer adaptively. Our approach is to maximize the secrecy achievable rate based on an analytically derived lower bound instead of the original objective function due to its complexity. Based on a simple proposed user selection criterion considering both macro and small base stations, we propose two jamming strategies according to knowledge of eavesdropper's channel: adaptive jamming and probabilistic jamming strategies. Through simulations in two scenarios, it is shown that our proposed user selection and jamming schemes provide a good performance gain in terms of secrecy achievable rate.
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