Publications by authors named "Byung Yang Lee"

38 Publications

Electroluminescent soft elastomer actuators with adjustable luminance and strain.

Soft Matter 2019 Oct 2;15(40):7996-8000. Epub 2019 Oct 2.

Department of Mechanical Engineering, Korea University, Seoul 02841, Republic of Korea.

We demonstrate a multifunctional soft actuator that exhibits both electroluminescence (EL) and soft actuation with a strain of 85% and a maximum luminance of 300 cd m, superior to previous devices with individual functions. This was possible by combining several strategies such as the development of highly conductive, transparent, and stretchable electrodes, incorporation of high-k nanoparticles to increase the electric field applied to the EL particles, and application of AC + DC composite signals to simplify the device structure. We expect this research to contribute to the development of new soft devices that can further enhance human-machine interactions in color displaying actuator applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c9sm01122fDOI Listing
October 2019

Electric Field Assisted Self-Assembly of Viruses into Colored Thin Films.

Nanomaterials (Basel) 2019 Sep 13;9(9). Epub 2019 Sep 13.

Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC 20052, USA.

Filamentous viruses called M13 bacteriophages are promising materials for devices with thin film coatings because phages are functionalizable, and they can self-assemble into smectic helicoidal nanofilament structures. However, the existing "pulling" approach to align the nanofilaments is slow and limits potential commercialization of this technology. This study uses an applied electric field to rapidly align the nanostructures in a fixed droplet. The electric field reduces pinning of the three-phase contact line, allowing it to recede at a constant rate. Atomic force microscopy reveals that the resulting aligned structures resemble those produced via the pulling method. The field-assisted alignment results in concentric color bands quantified with image analysis of red, green, and blue line profiles. The alignment technique shown here could reduce self-assembly time from hours to minutes and lend itself to scalable manufacturing techniques such as inkjet printing.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/nano9091310DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6781059PMC
September 2019

Facile fabrication of self-assembled ZnO nanowire network channels and its gate-controlled UV detection.

Nanoscale Res Lett 2018 Dec 24;13(1):413. Epub 2018 Dec 24.

Department of Mechanical Engineering, Korea University, Seoul, 02841, South Korea.

We demonstrate a facile way to fabricate an array of gate-controllable UV sensors based on assembled zinc oxide nanowire (ZnO NW) network field-effect transistor (FET). This was realized by combining both molecular surface programmed patterning and selective NW assembly on the polar regions avoiding the nonpolar regions, followed by heat treatment at 300 °C to ensure stable contact between NWs. The ZnO NW network FET devices showed typical n-type characteristic with an on-off ratio of 10, transconductance around 47 nS, and mobility around 0.175 cm V s. In addition, the devices showed photoresponsive behavior to UV light that can be controlled by the applied gate voltage. The photoresponsivity was found to be linearly proportional to the channel voltage V, showing maximum photoresponsivity at V = 7 V.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s11671-018-2774-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6305260PMC
December 2018

Modified Floating Electrode-Based Sensors for the Quantitative Monitoring of Drug Effects on Cytokine Levels Related with Inflammatory Bowel Diseases.

ACS Appl Mater Interfaces 2018 May 9;10(20):17100-17106. Epub 2018 May 9.

Department of Internal Medicine and Healthcare Research Institute , Seoul National University Hospital Healthcare System Gangnam Center , Seoul 06236 , Korea.

Modified floating electrode-based sensors were developed to quantitatively monitor the levels of tumor necrosis factor α (TNF-α), a pro-inflammatory cytokine related with inflammatory bowel disease (IBD), and to evaluate the effect of drugs on the cytokine levels. Here, antibodies (anti-TNF-α) were immobilized on the floating electrodes of carbon nanotube devices, enabling selective and real-time detection of TNF-α among various cytokines linked to IBD. This sensor was able to measure the concentrations of TNF-α with a detection limit of 1 pg/L, allowing the quantitative estimation of TNF-α secretion from mouse macrophage Raw 264.7 cells stimulated by lipopolysaccharides (LPS). Notably, this method also allowed us to monitor the anti-inflammatory effect of a drug, lupeol, on the activation of the LPS-induced nuclear factor κB signaling in Raw 264.7 cells. These results indicate that our novel TNF sensor can be a versatile tool for biomedical research and clinical applications such as screening drug effects and monitoring inflammation levels.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsami.8b04287DOI Listing
May 2018

Cellulose Nanocrystal-Based Colored Thin Films for Colorimetric Detection of Aldehyde Gases.

ACS Appl Mater Interfaces 2018 Mar 19;10(12):10353-10361. Epub 2018 Mar 19.

Department of Mechanical Engineering , Korea University , Seoul 02841 , Korea.

We demonstrate a controllable and reliable process for manifesting color patterns on solid substrates using cellulose nanocrystals (CNCs) without the use of any other chemical pigments. The color can be controlled by adjusting the assembly conditions of the CNC solution during a dip-and-pull process while aiding the close packing of CNCs on a solid surface with the help of ionic-liquid (1-butyl-3-methylimidazolium) molecules that screen the repelling electrostatic charges between CNCs. By controlling the pulling speed from 3 to 9 μm/min during the dip-and-pull process, we were able to control the film thickness from 100 to 300 nm, resulting in films with different colors in the visible range. The optical properties were in good agreement with the finite-difference time-domain simulation results. By functionalizing these films with amine groups, we developed colorimetric sensors that can change in color when exposed to aldehyde gases such as formaldehyde or propanal. A principal component analysis showed that we can differentiate between different aldehyde gases and other interfering molecules. We expect that our approach will enable inexpensive and rapid volatile organic compound detection with on-site monitoring capabilities.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsami.7b19738DOI Listing
March 2018

Engineered Phage Matrix Stiffness-Modulating Osteogenic Differentiation.

ACS Appl Mater Interfaces 2018 Feb 22;10(5):4349-4358. Epub 2018 Jan 22.

BIO-IT Foundry Technology Institute, Pusan National University , Busan 46241, Republic of Korea.

Herein, we demonstrate an engineered phage mediated matrix for osteogenic differentiation with controlled stiffness by cross-linking the engineered phage displaying Arg-Gly-Asp (RGD) and His-Pro-Gln (HPQ) with various concentrations of streptavidin or polymer, poly(diallyldimethylammonium)chloride (PDDA). Osteogenic gene expressions showed that they were specifically increased when MC3T3 cells were cultured on the stiffer phage matrix than the softer one. Our phage matrixes can be easily functionalized using chemical/genetic engineering and used as a stem cell tissue matrix stiffness platform for modulating differential cell expansion and differentiation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsami.7b17871DOI Listing
February 2018

Highly sensitive and flexible strain sensors based on patterned ITO nanoparticle channels.

Nanotechnology 2017 Dec;28(49):495501

Department of Mechanical Engineering, Korea University, Seoul 02841, Republic of Korea.

We demonstrate a highly sensitive and flexible bending strain sensor using tin-doped indium oxide (ITO) nanoparticles (NPs) assembled in line patterns on flexible substrates. By utilizing transparent ITO NPs without any surface modifications, we could produce strain sensors with adjustable gauge factors and optical transparency. We were able to control the dimensional and electrical properties of the sensors, such as channel height and resistance, by controlling the NP assembly speed. Furthermore, we were able to generate controlled gauge factor with values ranging from 18 to 157, which are higher than previous cases using metallic Cr NPs and Au NPs. The alignment of the ITO NPs in parallel lines resulted in low crosstalk between the transverse and longitudinal bending directions. Finally, our sensor showed high optical transmittance, up to ∼93% at 500 nm wavelength, which is desirable for flexible electronic applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/1361-6528/aa9237DOI Listing
December 2017

Highly flexible and transparent dielectric elastomer actuators using silver nanowire and carbon nanotube hybrid electrodes.

Soft Matter 2017 Sep;13(37):6390-6395

Department of Mechanical Engineering, Korea University, Seoul 02841, Republic of Korea.

We demonstrate a dielectric elastomer actuator (DEA) with a high areal strain value of 146% using hybrid electrodes of silver nanowires (AgNWs) and single-walled carbon nanotubes (SWCNTs). The addition of a very small amount of SWCNTs (∼35 ng mm) to a highly resistive AgNW network resulted in a remarkable reduction of the electrode sheet resistance by three orders, increasing the breakdown field by 183% and maximum strain, while maintaining the reduction of optical transmittance within 11%. The DEA based on our transparent and stretchable hybrid electrodes can be easily fabricated by a simple vacuum filtration and transfer process of the electrode film on a pre-strained dielectric elastomer membrane. We expect that our approach will be useful in the future for fabricating stretchable and transparent electrodes in various soft electronic devices.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c7sm01329aDOI Listing
September 2017

Trapped charge-driven degradation of perovskite solar cells.

Nat Commun 2016 11 10;7:13422. Epub 2016 Nov 10.

Global Frontier Center for Multiscale Energy Systems, Seoul National University, Seoul 08826, Korea.

Perovskite solar cells have shown unprecedent performance increase up to 22% efficiency. However, their photovoltaic performance has shown fast deterioration under light illumination in the presence of humid air even with encapulation. The stability of perovskite materials has been unsolved and its mechanism has been elusive. Here we uncover a mechanism for irreversible degradation of perovskite materials in which trapped charges, regardless of the polarity, play a decisive role. An experimental setup using different polarity ions revealed that the moisture-induced irreversible dissociation of perovskite materials is triggered by charges trapped along grain boundaries. We also identified the synergetic effect of oxygen on the process of moisture-induced degradation. The deprotonation of organic cations by trapped charge-induced local electric field would be attributed to the initiation of irreversible decomposition.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/ncomms13422DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5110646PMC
November 2016

Efficiency enhancement in a backside illuminated 1.12 μm pixel CMOS image sensor via parabolic color filters.

Opt Express 2016 Jul;24(14):16027-36

The shrinkage of pixel size down to sub-2 μm in high-resolution CMOS image sensors (CISs) results in degraded efficiency and increased crosstalk. The backside illumination technology can increase the efficiency, but the crosstalk still remains an critical issue to improve the image quality of the CIS devices. In this paper, by adopting a parabolic color filter (P-CF), we demonstrate efficiency enhancement without any noticeable change in optical crosstalk of a backside illuminated 1.12 μm pixel CIS with deep-trench-isolation structure. To identify the observed results, we have investigated the effect of radius of curvature (r) of the P-CF on the efficiency and optical crosstalk of the CIS by performing an electromagnetic analysis. As the r of P-CF becomes equal to (or half) that of the microlens, the efficiencies of the B-, G-, and R-pixels increase by a factor of 14.1% (20.3%), 9.8% (15.3%), and 15.0% (15.7%) with respect to the flat CF cases without any noticeable crosstalk change. Also, as the incident angle increases up to 30°, the angular dependence of the efficiency and crosstalk significantly decreases by utilizing the P-CF in the CIS. Meanwhile, further reduction of r severely increases the optical crosstalk due to the increased diffraction effect, which has been confirmed with the simulated electric-field intensity distribution inside the devices.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.24.016027DOI Listing
July 2016

Carbon and metal nanotube hybrid structures on graphene as efficient electron field emitters.

Nanotechnology 2016 Jul 27;27(27):275301. Epub 2016 May 27.

Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea. Department of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul 05006, Korea.

We report a facile and efficient method for the fabrication of highly-flexible field emission devices by forming tubular hybrid structures based on carbon nanotubes (CNTs) and nickel nanotubes (Ni NTs) on graphene-based flexible substrates. By employing an infiltration process in anodic alumina oxide (AAO) templates followed by Ni electrodeposition, we could fabricate CNT-wrapped Ni NT/graphene hybrid structures. During the electrodeposition process, the CNTs served as Ni nucleation sites, resulting in a large-area array of high aspect-ratio field emitters composed of CNT-wrapped Ni NT hybrid structures. As a proof of concepts, we demonstrate that high-quality flexible field emission devices can be simply fabricated using our method. Remarkably, our proto-type field emission devices exhibited a current density higher by two orders of magnitude compared to other devices fabricated by previous methods, while maintaining its structural integrity in various bending deformations. This novel fabrication strategy can be utilized in various applications such as optoelectronic devices, sensors and energy storage devices.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/0957-4484/27/27/275301DOI Listing
July 2016

Fully Automated Field-Deployable Bioaerosol Monitoring System Using Carbon Nanotube-Based Biosensors.

Environ Sci Technol 2016 05 29;50(10):5163-71. Epub 2016 Apr 29.

Department of Mechanical Engineering and ‡BK21PLUS Program in Embodiment: Health-Society Interaction, Department of Public Health Sciences, Graduate School, Korea University , Seoul 02841, Korea.

Much progress has been made in the field of automated monitoring systems of airborne pathogens. However, they still lack the robustness and stability necessary for field deployment. Here, we demonstrate a bioaerosol automonitoring instrument (BAMI) specifically designed for the in situ capturing and continuous monitoring of airborne fungal particles. This was possible by developing highly sensitive and selective fungi sensors based on two-channel carbon nanotube field-effect transistors (CNT-FETs), followed by integration with a bioaerosol sampler, a Peltier cooler for receptor lifetime enhancement, and a pumping assembly for fluidic control. These four main components collectively cooperated with each other to enable the real-time monitoring of fungi. The two-channel CNT-FETs can detect two different fungal species simultaneously. The Peltier cooler effectively lowers the working temperature of the sensor device, resulting in extended sensor lifetime and receptor stability. The system performance was verified in both laboratory conditions and real residential areas. The system response was in accordance with reported fungal species distribution in the environment. Our system is versatile enough that it can be easily modified for the monitoring of other airborne pathogens. We expect that our system will expedite the development of hand-held and portable systems for airborne bioaerosol monitoring.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.5b06361DOI Listing
May 2016

Synaptic compartmentalization by micropatterned masking of a surface adhesive cue in cultured neurons.

Biomaterials 2016 06 19;92:46-56. Epub 2016 Mar 19.

Department of Anatomy, Brain Korea 21, Korea University College of Medicine, Anam-Dong, Sungbuk-Gu, Seoul, 136-705, Republic of Korea. Electronic address:

Functions of neuronal circuit are fundamentally modulated by its quality and quantity of connections. Assessment of synapse, the basic unit for a neuronal connection, is labor-intensive and time-consuming in conventional culture systems, due to the small size and the spatially random distribution. In the present study, we propose a novel 'synapse compartmentalization' culture system, in which synapses are concentrated at controlled locations. We fabricated a negative dot array pattern by coating the entire surface with poly-l-lysine (PLL) and subsequent microcontact printing of 1) substrates which mask positive charge of PLL (Fc, BSA and laminin), or 2) a chemorepulsive protein (Semaphorin 3F-Fc). By combination of physical and biological features of these repulsive substrates, functional synapses were robustly concentrated in the PLL-coated dots. This synapse compartmentalization chip can be combined with the various high-throughput assay formats based on the synaptic morphology and function. Therefore, this quantifiable and controllable dot array pattern by microcontact printing will be potential useful for bio-chip platforms for the high-density assays used in synapse-related neurobiological studies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.biomaterials.2016.03.027DOI Listing
June 2016

Selective and Sensitive Sensing of Flame Retardant Chemicals Through Phage Display Discovered Recognition Peptide.

Nano Lett 2015 Nov 13;15(11):7697-703. Epub 2015 Oct 13.

Physical Biosciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.

We report a highly selective and sensitive biosensor for the detection of an environmentally toxic molecule, decabrominated diphenyl ether (DBDE), one of the most common congeners of the polybrominated frame retardants (polybrominated diphenyl ether (PBDE)), using newly discovered DBDE peptide receptors integrated with carbon nanotube field-effect transistors (CNT-FET). The specific DBDE peptide receptor was identified using a high-throughput screening process of phage library display. The resulting binding peptide carries an interesting consensus binding pocket with two Trp-His/Asn-Trp repeats, which binds to the DBDE in a multivalent manner. We integrated the novel DBDE binding peptide onto the CNT-FET using polydiacetylene coating materials linked through cysteine-maleimide click chemistry. The resulting biosensor could detect the desired DBDE selectively with a 1 fM detection limit. Our combined approaches of selective receptor discovery, material nanocoating through click chemistry, and integration onto a sensitive CNT-FET electronic sensor for desired target chemicals will pave the way toward the rapid development of portable and easy-to-use biosensors for desired chemicals to protect our health and environment.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.nanolett.5b03678DOI Listing
November 2015

Bi-Assisted CdTe/CdS Hierarchical Nanostructure Growth for Photoconductive Applications.

Nanoscale Res Lett 2015 Dec 19;10(1):1037. Epub 2015 Aug 19.

Department of Physics and Astronomy, Seoul National University, Seoul, 151-747, Republic of Korea,

We developed a method to control the structure of CdTe nanowires by adopting Bi-mixed CdTe powder source to a catalyst-assisted chemical vapor deposition, which allowed us to fabricate CdTe/CdS hierarchical nanostructures. We demonstrated that diverse nanostructures can be grown depending on the combination of the Bi powder and film catalysts. As a proof of concepts, we grew CdTe/CdS branched nanowires for the fabrication of photodetectors. The hierarchical nanostructure-based photodetectors showed an improved photoresponsivity compared to the single CdTe nanowire (NW)-based photodetector. Our strategy can be a simple but powerful method for the development of advanced optoelectronic devices and other practical applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s11671-015-1037-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4539310PMC
December 2015

Real-time detection of chlorine gas using Ni/Si shell/core nanowires.

Nanoscale Res Lett 2015 28;10:18. Epub 2015 Jan 28.

School of Mechanical Engineering, Korea University, 145 Anam-Ro, Seongbuk-Gu, Seoul 136-713 Korea.

We demonstrate the selective adsorption of Ni/Si shell/core nanowires (Ni-Si NWs) with a Ni outer shell and a Si inner core on molecularly patterned substrates and their application to sensors for the detection of chlorine gas, a toxic halogen gas. The molecularly patterned substrates consisted of polar SiO2 regions and nonpolar regions of self-assembled monolayers of octadecyltrichlorosilane (OTS). The NWs showed selective adsorption on the polar SiO2 regions, avoiding assembly on the nonpolar OTS regions. Utilizing these assembled Ni-Si NWs, we demonstrate a sensor for the detection of chlorine gas. The utilization of Ni-Si NWs resulted in a much larger sensor response of approximately 23% to 5 ppm of chlorine gas compared to bare Ni NWs, due to the increased surface-to-volume ratio of the Ni-Si shell/core structure. We expect that our sensor will be utilized in the future for the real-time detection of halogen gases including chlorine with high sensitivity and fast response.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s11671-015-0729-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4314467PMC
April 2015

Synergistically enhanced stability of highly flexible silver nanowire/carbon nanotube hybrid transparent electrodes by plasmonic welding.

ACS Appl Mater Interfaces 2014 Jul 7;6(14):10974-80. Epub 2014 Jul 7.

School of Mechanical Engineering, Korea University , Anam-Dong, Seongbuk-Gu, Seoul 136713, Korea.

Here, we report highly transparent and flexible AgNW/SWCNT hybrid networks on PET substrates combined with plasmonic welding for securing ultrahigh stability in mechanical and electrical properties under severe bending. Plasmonic welding produces local heating and welding at the junction of AgNWs and leads strong adhesion between AgNW and SWCNT as well as between hybrid structure and substrate. The initial sheet resistance of plasmon treated AgNW/SWCNT hybrid film was 26 Ω sq(-1), with >90% optical transmittance over the wavelength range 400-2700 nm. Following 200 cycles of convex/concave bending with a bending radius of 5 mm, the sheet resistance changed from 26 to 29 Ω sq(-1). This hybrid structure combined with the plasmonic welding process provided excellent stability, low resistance, and high transparency, and is suitable for highly flexible electronics applications, including touch panels, solar cells, and OLEDs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/am502639nDOI Listing
July 2014

Direct-write complementary graphene field effect transistors and junctions via near-field electrospinning.

Small 2014 May 5;10(10):1920-5. Epub 2014 Mar 5.

Department of Physics, University of California at Berkeley, USA; Berkeley Sensor and Actuator Center, University of California at Berkeley, USA.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/smll.201302965DOI Listing
May 2014

Biomimetic virus-based colourimetric sensors.

Nat Commun 2014 ;5:3043

1] Department of Bioengineering, University of California, Berkeley, California 94720, USA [2] Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.

Many materials in nature change colours in response to stimuli, making them attractive for use as sensor platform. However, both natural materials and their synthetic analogues lack selectivity towards specific chemicals, and introducing such selectivity remains a challenge. Here we report the self-assembly of genetically engineered viruses (M13 phage) into target-specific, colourimetric biosensors. The sensors are composed of phage-bundle nanostructures and exhibit viewing-angle independent colour, similar to collagen structures in turkey skin. On exposure to various volatile organic chemicals, the structures rapidly swell and undergo distinct colour changes. Furthermore, sensors composed of phage displaying trinitrotoluene (TNT)-binding peptide motifs identified from a phage display selectively distinguish TNT down to 300 p.p.b. over similarly structured chemicals. Our tunable, colourimetric sensors can be useful for the detection of a variety of harmful toxicants and pathogens to protect human health and national security.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/ncomms4043DOI Listing
November 2015

Highly selective and sensitive detection of neurotransmitters using receptor-modified single-walled carbon nanotube sensors.

Nanotechnology 2013 Jul;24(28):285501

Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea.

We present receptor-modified carbon nanotube sensors for the highly selective and sensitive detection of acetylcholine (ACh), one kind of neurotransmitter. Here, we successfully expressed the M1 muscarinic acetylcholine receptor (M1 mAChR), a family of G protein-coupled receptors (GPCRs), in E. coli and coated single-walled carbon nanotube (swCNT)-field effect transistors (FETs) with lipid membrane including the receptor, enabling highly selective and sensitive ACh detection. Using this sensor, we could detect ACh at 100 pM concentration. Moreover, we showed that this sensor could selectively detect ACh among other neurotransmitters. This is the first demonstration of the real-time detection of ACh using specific binding between ACh and M1 mAChR, and it may lead to breakthroughs for various applications such as disease diagnosis and drug screening.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/0957-4484/24/28/285501DOI Listing
July 2013

Impedimetric graphene-based biosensors for the detection of polybrominated diphenyl ethers.

Nanoscale 2013 Jul 29;5(13):6048-52. Epub 2013 May 29.

Department of Chemical and Biomolecular Engineering, University of California at Berkeley, 94720 Berkeley, CA, USA.

Single-layer graphene, decorated with Au nanoparticles, and a specially designed peptide are used for the first time in the detection of decabrominediphenyl ether using impedance spectroscopy. Biosensor calibration is presented, showing a good linear response from 5% to saturated dissolutions (100 ppt). Selectivity towards brominated species is demonstrated by lack of response to molecules with similar structures but without any bromines.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c3nr01268aDOI Listing
July 2013

Electrical control of kinesin-microtubule motility using a transparent functionalized-graphene substrate.

Nanotechnology 2013 May 17;24(19):195102. Epub 2013 Apr 17.

Department of Biophysics and Chemical Biology, Seoul National University, Seoul, Korea.

We report a new strategy to selectively localize and control microtubule translocation via electrical control of microtubules using a microfabricated channel on a functionalized-graphene electrode with high transparency and conductivity. A patterned SU-8 film acts as an insulation layer which shields the electrical field generated by the graphene underneath while the localized electric field on the exposed graphene surface guides the negatively charged microtubules. This is the first report showing that functionalized graphene can support and control microtubule motility.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/0957-4484/24/19/195102DOI Listing
May 2013

Reply to comment on 'Metallic nanowire-graphene hybrid nanostructures for highly flexible field emission devices'.

Nanotechnology 2012 Jul 25;23(28):288002. Epub 2012 Jun 25.

Department of Physics and Astronomy, Seoul National University, Seoul, Korea.

In our previous paper (Arif et al 2011 Nanotechnology 22 355709), we developed a method to prepare metallic nanowire-graphene hybrid nanostructures and applied it to the fabrication of flexible field emission devices. For the quantitative analysis of the devices, the basic Fowler-Nordheim model was used. However, as pointed out by Forbes (2012 Nanotechnology 23 288001) the basic Fowler-Nordheim model should be corrected when the quantum confinement effect and the screening effect are considered. Forbes also developed a method that checks quantitatively the consistency between the experimental data and the theoretical assumptions. These discussions should provide an important theoretical framework in the quantitative analysis of our devices as well as large area field emitters in general.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/0957-4484/23/28/288002DOI Listing
July 2012

Virus-based piezoelectric energy generation.

Nat Nanotechnol 2012 May 13;7(6):351-6. Epub 2012 May 13.

Department of Bioengineering, University of California, Berkeley, California 94720, USA.

Piezoelectric materials can convert mechanical energy into electrical energy, and piezoelectric devices made of a variety of inorganic materials and organic polymers have been demonstrated. However, synthesizing such materials often requires toxic starting compounds, harsh conditions and/or complex procedures. Previously, it was shown that hierarchically organized natural materials such as bones, collagen fibrils and peptide nanotubes can display piezoelectric properties. Here, we demonstrate that the piezoelectric and liquid-crystalline properties of M13 bacteriophage (phage) can be used to generate electrical energy. Using piezoresponse force microscopy, we characterize the structure-dependent piezoelectric properties of the phage at the molecular level. We then show that self-assembled thin films of phage can exhibit piezoelectric strengths of up to 7.8 pm V(-1). We also demonstrate that it is possible to modulate the dipole strength of the phage, hence tuning the piezoelectric response, by genetically engineering the major coat proteins of the phage. Finally, we develop a phage-based piezoelectric generator that produces up to 6 nA of current and 400 mV of potential and use it to operate a liquid-crystal display. Because biotechnology techniques enable large-scale production of genetically modified phages, phage-based piezoelectric materials potentially offer a simple and environmentally friendly approach to piezoelectric energy generation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/nnano.2012.69DOI Listing
May 2012

Nanotube-bridged wires with sub-10 nm gaps.

Nano Lett 2012 Apr 28;12(4):1879-84. Epub 2012 Mar 28.

Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea.

We report a simple but efficient method to synthesize carbon nanotube-bridged wires (NBWs) with gaps as small as 5 nm. In this method, we have combined a strategy for assembling carbon nanotubes (CNTs) inside anodized aluminum oxide pores and the on-wire lithography technique to fabricate CNT-bridged wires with gap sizes deliberately tailored over the 5-600 nm range. As a proof-of-concept demonstration of the utility of this architecture, we have prepared NBW-based chemical and biosensors which exhibit higher analyte sensitivity (lower limits of detection) than those based on planar CNT networks. This observation is attributed to a greater surface-to-volume ratio of CNTs in the NBWs than those in the planar CNT devices. Because of the ease of synthesis and high yield of NBWs, this technique may enable the further incorporation of CNT-based architectures into various nanoelectronic and sensor platforms.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/nl204259tDOI Listing
April 2012

Biomimetic self-templating supramolecular structures.

Nature 2011 Oct 19;478(7369):364-8. Epub 2011 Oct 19.

Department of Bioengineering, University of California, Berkeley, California 94720, USA.

In nature, helical macromolecules such as collagen, chitin and cellulose are critical to the morphogenesis and functionality of various hierarchically structured materials. During tissue formation, these chiral macromolecules are secreted and undergo self-templating assembly, a process whereby multiple kinetic factors influence the assembly of the incoming building blocks to produce non-equilibrium structures. A single macromolecule can form diverse functional structures when self-templated under different conditions. Collagen type I, for instance, forms transparent corneal tissues from orthogonally aligned nematic fibres, distinctively coloured skin tissues from cholesteric phase fibre bundles, and mineralized tissues from hierarchically organized fibres. Nature's self-templated materials surpass the functional and structural complexity achievable by current top-down and bottom-up fabrication methods. However, self-templating has not been thoroughly explored for engineering synthetic materials. Here we demonstrate the biomimetic, self-templating assembly of chiral colloidal particles (M13 phage) into functional materials. A single-step process produces long-range-ordered, supramolecular films showing multiple levels of hierarchical organization and helical twist. Three distinct supramolecular structures are created by this approach: nematic orthogonal twists, cholesteric helical ribbons and smectic helicolidal nanofilaments. Both chiral liquid crystalline phase transitions and competing interfacial forces at the interface are found to be critical factors in determining the morphology of the templated structures during assembly. The resulting materials show distinctive optical and photonic properties, functioning as chiral reflector/filters and structural colour matrices. In addition, M13 phages with genetically incorporated bioactive peptide ligands direct both soft and hard tissue growth in a hierarchically organized manner. Our assembly approach provides insight into the complexities of hierarchical assembly in nature and could be expanded to other chiral molecules to engineer sophisticated functional helical-twisted structures.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/nature10513DOI Listing
October 2011

Metallic nanowire-graphene hybrid nanostructures for highly flexible field emission devices.

Nanotechnology 2011 Sep 9;22(35):355709. Epub 2011 Aug 9.

Department of Physics and Astronomy, Seoul National University, Seoul, Korea.

We report a simple but efficient method to prepare metallic nanowire-graphene (MN-G) hybrid nanostructures at a low temperature and show its application to the fabrication of flexible field emission devices. In this method, a graphene layer was transferred onto an anodic alumina oxide template, and vertically aligned Au nanowires were grown on the graphene surface via electrodeposition method. As a proof of concept, we demonstrated the fabrication of flexible field emission devices, where the MN-G hybrid nanostructures and another graphene layer on PDMS substrates were utilized as a cathode and an anode for highly flexible devices, respectively. Our field emission device exhibited stable and high field emission currents even when bent down to the radius of curvature of 25 mm. This MN-G hybrid nanostructure should prove tremendous flexibility for various applications such as bio-chemical sensors, field emission devices, pressure sensors and battery electrodes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/0957-4484/22/35/355709DOI Listing
September 2011

Universal parameters for carbon nanotube network-based sensors: can nanotube sensors be reproducible?

ACS Nano 2011 Jun 26;5(6):4373-9. Epub 2011 May 26.

Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea.

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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/nn103056sDOI Listing
June 2011

Selective and sensitive TNT sensors using biomimetic polydiacetylene-coated CNT-FETs.

ACS Nano 2011 Apr 1;5(4):2824-30. Epub 2011 Mar 1.

Department of Bioengineering, University of California, Berkeley, California 94720, USA.

Miniaturized smart sensors that can perform sensitive and selective real-time monitoring of target analytes are tremendously valuable for various sensing applications. We developed selective nanocoatings by combining trinitrotoluene (TNT) receptors bound to conjugated polydiacetylene (PDA) polymers with single-walled carbon nanotube field-effect transistors (SWNT-FET). Selective binding events between the TNT molecules and phage display derived TNT receptors were effectively transduced to sensitive SWNT-FET conductance sensors through the PDA coating layers. The resulting sensors exhibited an unprecedented 1 fM sensitivity toward TNT in real time, with excellent selectivity over various similar aromatic compounds. Our biomimetic receptor coating approach may be useful for the development of sensitive and selective micro- and nanoelectronic sensor devices for various other target analytes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/nn103324pDOI Listing
April 2011

Alignment strategies for the assembly of nanowires with submicron diameters.

Small 2010 Aug;6(16):1736-40

Department of Chemistry and International Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113, USA.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/smll.201000815DOI Listing
August 2010