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Corletto A, Shapter JG. Nanoscale Patterning of Carbon Nanotubes: Techniques, Applications, and Future. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2020; 8:2001778. [PMID: 33437571 PMCID: PMC7788638 DOI: 10.1002/advs.202001778] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 07/30/2020] [Indexed: 05/09/2023]
Abstract
Carbon nanotube (CNT) devices and electronics are achieving maturity and directly competing or surpassing devices that use conventional materials. CNTs have demonstrated ballistic conduction, minimal scaling effects, high current capacity, low power requirements, and excellent optical/photonic properties; making them the ideal candidate for a new material to replace conventional materials in next-generation electronic and photonic systems. CNTs also demonstrate high stability and flexibility, allowing them to be used in flexible, printable, and/or biocompatible electronics. However, a major challenge to fully commercialize these devices is the scalable placement of CNTs into desired micro/nanopatterns and architectures to translate the superior properties of CNTs into macroscale devices. Precise and high throughput patterning becomes increasingly difficult at nanoscale resolution, but it is essential to fully realize the benefits of CNTs. The relatively long, high aspect ratio structures of CNTs must be preserved to maintain their functionalities, consequently making them more difficult to pattern than conventional materials like metals and polymers. This review comprehensively explores the recent development of innovative CNT patterning techniques with nanoscale lateral resolution. Each technique is critically analyzed and applications for the nanoscale-resolution approaches are demonstrated. Promising techniques and the challenges ahead for future devices and applications are discussed.
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Affiliation(s)
- Alexander Corletto
- Australian Institute for Bioengineering and NanotechnologyThe University of QueenslandBrisbaneQueensland4072Australia
| | - Joseph G. Shapter
- Australian Institute for Bioengineering and NanotechnologyThe University of QueenslandBrisbaneQueensland4072Australia
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Rao SG. Wafer-scale directed self-assembly of nanostructures using self-assembled monolayer based controlled-wetting. Colloids Surf A Physicochem Eng Asp 2013. [DOI: 10.1016/j.colsurfa.2013.08.050] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Lee BY, Sung MG, Lee J, Baik KY, Kwon YK, Lee MS, Hong S. Universal parameters for carbon nanotube network-based sensors: can nanotube sensors be reproducible? ACS NANO 2011; 5:4373-4379. [PMID: 21615164 DOI: 10.1021/nn103056s] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Carbon nanotube (CNT) network-based sensors have been often considered unsuitable for practical applications due to their unpredictable characteristics. Herein, we report the study of universal parameters which can be used to characterize CNT network-based sensors and make their response predictable. A theoretical model is proposed to explain these parameters, and sensing experiments for mercury (Hg(2+)) and ammonium (NH(4)(+)) ions using CNT network-based sensors were performed to confirm the validity of our model.
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Affiliation(s)
- Byung Yang Lee
- Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
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Lee J, Jo M, Kim TH, Ahn JY, Lee DK, Kim S, Hong S. Aptamer sandwich-based carbon nanotube sensors for single-carbon-atomic-resolution detection of non-polar small molecular species. LAB ON A CHIP 2011; 11:52-56. [PMID: 20967396 DOI: 10.1039/c0lc00259c] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A portable sensor platform for the detection of small molecular species is crucial for the on-site monitoring of environmental pollutants, food toxicants, and disease-related metabolites. However, it is still extremely difficult to find highly selective and sensitive sensor platforms for general small molecular detection. Herein, we report aptamer sandwich-based carbon nanotube sensor strategy for small molecular detection, where aptamers were utilized to capture target molecules as well as to enhance the sensor signals. We successfully demonstrated the detection of non-polar bisphenol A molecules with a 1 pM sensitivity. Significantly, our sensors were able to distinguish between similar small molecular species with single-carbon-atomic resolution. Furthermore, using the additional biotin modification on labeling aptamer, we enhanced the detection limit of our sensors down to 10 fM. This strategy allowed us to detect non-polar small molecular species using carbon nanotube transistors, thus overcoming the fundamental limitation of field effect transistor-based sensors. Considering the extensive applications of sandwich assay for the detection of rather large biomolecules, our results should open up completely new dimension in small molecular detection technology and should enable a broad range of applications such as environmental protection and food safety.
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Affiliation(s)
- Joohyung Lee
- Department of Physics and Astronomy, Seoul National University, Seoul, 151-742, Korea
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Lee H, Lee M, Namgung S, Hong S. Wide contact structures for low-noise nanochannel devices based on a carbon nanotube network. ACS NANO 2010; 4:7612-7618. [PMID: 21050016 PMCID: PMC3010873 DOI: 10.1021/nn102296e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/06/2010] [Accepted: 10/29/2010] [Indexed: 05/30/2023]
Abstract
We have developed a wide contact structure for low-noise nanochannel devices based on a carbon nanotube (CNT) network. This low-noise CNT network-based device has a dumbbell-shaped channel, which has wide CNT/electrode contact regions and, in effect, reduces the contact noise. We also performed a systematic analysis of structured CNT networks and established an empirical formula that can explain the noise behavior of arbitrary-shaped CNT network-based devices including the effect of contact regions and CNT alignment. Interestingly, our analysis revealed that the noise amplitude of aligned CNT networks behaves quite differently compared with that of randomly oriented CNT networks. Our results should be an important guideline in designing low-noise nanoscale devices based on a CNT network for various applications such as a highly sensitive low-noise sensor.
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Affiliation(s)
- Hyungwoo Lee
- Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
| | - Minbaek Lee
- Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
| | - Seon Namgung
- Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
| | - Seunghun Hong
- Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
- Department of Biophysics and Chemical Biology (WCU Program), Seoul National University, Seoul 151-747, Korea
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Lee BY, Seo SM, Lee DJ, Lee M, Lee J, Cheon JH, Cho E, Lee H, Chung IY, Park YJ, Kim S, Hong S. Biosensor system-on-a-chip including CMOS-based signal processing circuits and 64 carbon nanotube-based sensors for the detection of a neurotransmitter. LAB ON A CHIP 2010; 10:894-898. [PMID: 20300676 DOI: 10.1039/b916975j] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We developed a carbon nanotube (CNT)-based biosensor system-on-a-chip (SoC) for the detection of a neurotransmitter. Here, 64 CNT-based sensors were integrated with silicon-based signal processing circuits in a single chip, which was made possible by combining several technological breakthroughs such as efficient signal processing, uniform CNT networks, and biocompatible functionalization of CNT-based sensors. The chip was utilized to detect glutamate, a neurotransmitter, where ammonia, a byproduct of the enzymatic reaction of glutamate and glutamate oxidase on CNT-based sensors, modulated the conductance signals to the CNT-based sensors. This is a major technological advancement in the integration of CNT-based sensors with microelectronics, and this chip can be readily integrated with larger scale lab-on-a-chip (LoC) systems for various applications such as LoC systems for neural networks.
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Affiliation(s)
- Byung Yang Lee
- Nano-Systems Institute, Seoul National University, Seoul, 151-742, Korea
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Lee M, Lee J, Kim TH, Lee H, Lee BY, Park J, Jhon YM, Seong MJ, Hong S. 100 nm scale low-noise sensors based on aligned carbon nanotube networks: overcoming the fundamental limitation of network-based sensors. NANOTECHNOLOGY 2010; 21:055504. [PMID: 20032552 DOI: 10.1088/0957-4484/21/5/055504] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Nanoscale sensors based on single-walled carbon nanotube (SWNT) networks have been considered impractical due to several fundamental limitations such as a poor sensitivity and small signal-to-noise ratio. Herein, we present a strategy to overcome these fundamental problems and build highly-sensitive low-noise nanoscale sensors simply by controlling the structure of the SWNT networks. In this strategy, we prepared nanoscale width channels based on aligned SWNT networks using a directed assembly strategy. Significantly, the aligned network-based sensors with narrower channels exhibited even better signal-to-noise ratio than those with wider channels, which is opposite to conventional random network-based sensors. As a proof of concept, we demonstrated 100 nm scale low-noise sensors to detect mercury ions with the detection limit of approximately 1 pM, which is superior to any state-of-the-art portable detection system and is below the allowable limit of mercury ions in drinking water set by most government environmental protection agencies. This is the first demonstration of 100 nm scale low-noise sensors based on SWNT networks. Considering the increased interests in high-density sensor arrays for healthcare and environmental protection, our strategy should have a significant impact on various industrial applications.
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Affiliation(s)
- Minbaek Lee
- Department of Physics and Astronomy, Seoul National University, Shilim-Dong, Kwanak-Gu, Seoul 151-742, Korea
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Lee M, Noah M, Park J, Seong MJ, Kwon YK, Hong S. "Textured" network devices: overcoming fundamental limitations of nanotube/nanowire network-based devices. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2009; 5:1642-1648. [PMID: 19347856 DOI: 10.1002/smll.200801500] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Affiliation(s)
- Minbaek Lee
- Department of Physics and Astronomy, Seoul National University, Korea
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Koh J, Yi M, Yang Lee B, Kim TH, Lee J, Jhon YM, Hong S. Directed assembly of carbon nanotubes on soft substrates for use as a flexible biosensor array. NANOTECHNOLOGY 2008; 19:505502. [PMID: 19942770 DOI: 10.1088/0957-4484/19/50/505502] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We have developed a method to selectively assemble and align carbon nanotubes (CNTs) on soft substrates for use as flexible biosensors. In this strategy, a thin oxide layer was deposited on soft substrates via low temperature plasma enhanced chemical vapor deposition, and a linker-free assembly process was applied on the oxide surface where the assembly of carbon nanotubes was guided by methyl-terminated molecular patterns on the oxide surface. The electrical characterization of the fabricated CNT devices exhibited a typical p-type gating effect and 1/f noise behavior. The bare oxide regions near CNTs were functionalized with glutamate oxidase to fabricate selective biosensors to detect two forms of glutamate substances existing in different situations: L-glutamic acid, a neurotransmitting material, and monosodium glutamate, a food additive.
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Affiliation(s)
- Juntae Koh
- Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
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Heo K, Cho E, Yang JE, Kim MH, Lee M, Lee BY, Kwon SG, Lee MS, Jo MH, Choi HJ, Hyeon T, Hong S. Large-scale assembly of silicon nanowire network-based devices using conventional microfabrication facilities. NANO LETTERS 2008; 8:4523-4527. [PMID: 19367934 DOI: 10.1021/nl802570m] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We present a method for assembling silicon nanowires (Si-NWs) in virtually general shape patterns using only conventional microfabrication facilities. In this method, silicon nanowires were functionalized with amine groups and dispersed in deionized water. The functionalized Si-NWs exhibited positive surface charges in the suspensions, and they were selectively adsorbed and aligned onto negatively charged surface regions on solid substrates. As a proof of concepts, we demonstrated transistors based on individual Si-NWs and long networks of Si-NWs.
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Affiliation(s)
- Kwang Heo
- Interdisciplinary Program in Nano-Science and Technology, Department of Physics and Astronomy, School of Chemical and Biological Engineering, Seoul National University, Seoul 151-747, Korea
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Lee UY, Heo K, Bak JH, Cho SU, Moon S, Park YD, Hong S. Scalable assembly method of vertically-suspended and stretched carbon nanotube network devices for nanoscale electro-mechanical sensing components. NANO LETTERS 2008; 8:4483-4487. [PMID: 19367853 DOI: 10.1021/nl802434s] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
For the first time, vertically suspended and stretched carbon nanotube network junctions were fabricated in large quantity via the directed assembly strategy using only conventional microfabrication facilities. In this process, surface molecular patterns on the side-wall of the Al structures were utilized to guide the assembly and alignment of carbon nanotubes in the solution. We also performed extensive experimental (electrical and mechanical) analysis and theoretical simulation about the vertically suspended single-walled carbon nanotube network junctions. The junctions exhibited semiconductor-like conductance behavior. Furthermore, we demonstrated gas sensing and electromechanical sensing using these devices.
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Affiliation(s)
- Ung Yang Lee
- Department of Physics and Astronomy, Interdisciplinary Program in Nano-Science and Technology, Seoul National University, Seoul 151-747, Korea
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Kang J, Lee J, Kim TH, Park J, Seong MJ, Hong S. Large-scale assembly of carbon nanotube-based flexible circuits for DNA sensors. NANOTECHNOLOGY 2008; 19:135305. [PMID: 19636144 DOI: 10.1088/0957-4484/19/13/135305] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We present a simple but efficient method to prepare carbon nanotube (CNT)-based flexible devices embedded in polymer substrates. In this strategy, a methyl-terminated self-assembled monolayer is first coated on a solid substrate as a release layer, and CNT-network devices fabricated on it are directly transferred into a poly(dimethylsiloxane) (PDMS) mold, resulting in flexible CNT-network devices embedded in PDMS. The embedded circuits exhibit stable operation even after significant bending. We also propose Raman spectroscopy as a powerful tool to remotely characterize the CNT-network device structures covered by a polymer layer. As a proof of concept, we demonstrate DNA sensors utilizing the fabricated CNT-network devices.
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Affiliation(s)
- Juwan Kang
- Physics and Astronomy, Seoul National University, Shilim-Dong, Kwanak-Gu, Seoul 151-742, Korea
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Kang J, Myung S, Kim B, Oh D, Kim GT, Hong S. Massive assembly of ZnO nanowire-based integrated devices. NANOTECHNOLOGY 2008; 19:095303. [PMID: 21817667 DOI: 10.1088/0957-4484/19/9/095303] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Although a directed assembly strategy has been utilized for the massive assembly of various nanowires and nanotubes (NWs/NTs), its application has usually been limited to rather small-diameter NWs/NTs prepared in solution. We report two complementary methods for the massive assembly of large-size ZnO nanowires (NWs). In the solution-phase method, ZnO NWs were assembled and aligned selectively onto negatively charged surface patterns in solution. In addition, the substrate bias voltage and capillary forces can be used to further enhance the adsorption rate and degree of alignment of ZnO NWs, respectively. In the direct-transfer method, a NW film grown on a solid substrate was placed in close proximity to a molecule-patterned substrate, and ultrasonic vibration was applied so that the NWs were directly transferred and aligned onto the patterned substrate. The solution-phase and direct-transfer methods are complementary to each other and suitable for the assembly of NWs prepared in solution and on solid substrates, respectively.
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Affiliation(s)
- Juwan Kang
- School of Physics, Seoul National University NS50, Shilim-Dong, Kwanak-Gu, Seoul 151-742, Korea
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YANG LINGLU, NURAJE NURXAT, BAI HANYING, MATSUI HIROSHI. Crossbar assembly of antibody-functionalized peptide nanotubes via biomimetic molecular recognition. J Pept Sci 2008; 14:203-9. [PMID: 18008382 PMCID: PMC6345667 DOI: 10.1002/psc.953] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2007] [Accepted: 09/13/2007] [Indexed: 11/07/2022]
Abstract
Previously, a large scale assembly of nanowires in a parallel array configuration has been demonstrated, and one type of nanowire could interconnect two electrodes in the high-wire density. However, to assemble nanowires into practical logic-gate configurations in integrated circuits, we need more than the parallel assembly of nanowires. For example, when the assembling nanowires are monopolar semiconductors, logic gates such as AND, OR and NOR are to be assembled necessarily from two types of semiconducting nanowires, n-type and p-type, and some of these nanowires must cross perpendicularly to form a crossbar geometry for the logical operation. In this paper, the crossbar assembly of antibody-functionalized peptide nanotubes was demonstrated by a new biomimetic bottom-up technique. Molecular recognition between antigens and antibodies enabled two types of the antibody-functionalized bionanotubes to place them onto targeted locations on substrates, where their complementary antigens were patterned. When two rectangular pads of antigens, human IgG and mouse IgG, were patterned perpendicularly on an Au substrate by nanolithography and then the antihuman IgG nanotubes and the antimouse IgG nanotubes were incubated on this substrate in solution, these bionanotubes were attached onto corresponding locations to form the crossbar configuration.
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Affiliation(s)
- LINGLU YANG
- Department of Chemistry and Biochemistry at Hunter College and the Graduate Center, The City University of New York, New York, NY 10021, USA
| | - NURXAT NURAJE
- Department of Chemistry and Biochemistry at Hunter College and the Graduate Center, The City University of New York, New York, NY 10021, USA
| | - HANYING BAI
- Department of Chemistry and Biochemistry at Hunter College and the Graduate Center, The City University of New York, New York, NY 10021, USA
| | - HIROSHI MATSUI
- Department of Chemistry and Biochemistry at Hunter College and the Graduate Center, The City University of New York, New York, NY 10021, USA
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Lee NK, Johner A, Hong SC. Compressing a rigid filament: buckling and cyclization. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2007; 24:229-241. [PMID: 17992470 DOI: 10.1140/epje/i2007-10230-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2007] [Accepted: 10/16/2007] [Indexed: 05/25/2023]
Abstract
We study elastic properties of rigid filaments modeled as stiff chains shorter than their persistence length. By rigid filaments we mean that fluctuations around the optimal filament shape are weak and that low-order expansions (quadratic or quartic) in the deviation from the optimal shape are sufficient to describe them. Our main interest lies in the profiles of force vs. projected filament length, closure probability and weakly buckled states. Results may be relevant to experiments on self-assembled biological (microtubules, actin filaments) and synthetic (organo-gelators) filaments, carbon nanotubes and polymers grafted with strongly repelling side chains, some of which are discussed here.
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Affiliation(s)
- N-K Lee
- Institute of Fundamental Physics, Department of Physics, Sejong University, 143-743, Seoul, South Korea.
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Byun KE, Kim MG, Chase PB, Hong S. Selective assembly and guiding of actomyosin using carbon nanotube network monolayer patterns. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:9535-9. [PMID: 17705520 DOI: 10.1021/la7019318] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
We report a new method for the selective assembly and guiding of actomyosin using carbon nanotube patterns. In this method, monolayer patterns of the single-walled carbon nanotube (swCNT) network were prepared via the self-limiting mechanism during the directed assembly process, and they were used to block the adsorption of both myosin and actin filaments on specific substrate regions. The swCNT network patterns were also used as an efficient barrier for the guiding experiments of actomyosin. This is the first result showing that inorganic nanostructures such as carbon nanotubes can be used to control the adsorption and activity of actomyosin. This strategy is advantageous over previous methods because it does not require complicated biomolecular linking processes and nonbiological nanostructures are usually more stable than biomolecular linkers.
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Affiliation(s)
- Kyung-Eun Byun
- Physics and Astronomy, Seoul National University, Shilim-Dong, Kwanak-Gu, Seoul, Korea
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Zhao Z, Matsui H. Accurate immobilization of antibody-functionalized peptide nanotubes on protein-patterned arrays by optimizing their ligand-receptor interactions. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2007; 3:1390-3. [PMID: 17590881 PMCID: PMC6369532 DOI: 10.1002/smll.200700006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Affiliation(s)
- Zheyuan Zhao
- Department of Chemistry and Biochemistry City University of NewYork, Hunter College NewYork, NY 10021 (USA), Fax: (+ 1) 212-650-3918
| | - Hiroshi Matsui
- Department of Chemistry and Biochemistry City University of NewYork, Hunter College NewYork, NY 10021 (USA), Fax: (+ 1) 212-650-3918
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Wei JH, Coffey DC, Ginger DS. Nucleating Pattern Formation in Spin-Coated Polymer Blend Films with Nanoscale Surface Templates. J Phys Chem B 2006; 110:24324-30. [PMID: 17134183 DOI: 10.1021/jp065409a] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We use Dip-Pen Nanolithography (DPN) to generate monolayer surface templates for guiding pattern formation in spin-coated polymer blend films. We study template-directed pattern formation in blends of polystyrene/poly(2-vinylpyridine) (PS/P2VP) as well as blends of PS and the semiconducting conjugated polymer poly(3-hexylthiophene) (P3HT). We show that acid-terminated monolayers can be used to template pattern formation in PS/P3HT blends, while hydrophobic monolayers can be used to template pattern formation in PS/P2VP blends. In both blends, the polymer patterns comprise laterally-phase separated regions surrounded by vertically separated bilayers. We hypothesize that the observed patterns are formed by template-induced dewetting of the bottom layer of a polymer bilayer during the spin-coating process. We compare the effects of template feature size and spacing on the resulting polymer patterns with predictions from published models of template-directed dewetting in thin films and find the data in good agreement. For both blends we observe that a minimum feature size is required to nucleate dewetting/phase separation. We find this minimum template diameter to be approximately 180 nm in 50/50 PS/P2VP blends, and approximately 100 nm in 50/50 PS/P3HT blends. For larger template diameters, PS/P2VP blends show evidence for pattern formation beginning at the template boundaries, while PS/P3HT blends rupture randomly across the template features.
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Affiliation(s)
- Joseph H Wei
- Department of Chemical Engineering, University of Washington, Seattle, Washington 98195-1750, USA
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