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The essential therapeutic cues provided by a nanofibrous arginine-glycine-aspartic acid-engineered M13 phage were exploited as extracellular matrix (ECM)-mimicking niches, contributing to de novo soft tissue niche engineering. The interplay of biomimetic phage cues with surrounding organ tissues was identified, and cells were implanted between tissues to achieve an appropriate soft tissue niche that enables the proper functioning of the implanted stem cells at the injured site. With the polyacrylamide (PA) hydrogel mimicking the soft tissue organ stiffness ranges, it was found that biochemical and topological cues in conjunction with the ∼1-2 kPa elastic and mechanical cues of engineered phage nanofibers in soft tissues efficiently enhance the desired response of implanted stem cells. This phage cue with angiogenic and antioxidant functions overcomes the pathological environment to support implanted cells and surrounding soft tissues at the ischemic site, thereby successfully decreasing myogenic degeneration, minimizing fibrosis, and enhancing blood vessel regeneration with M2 macrophage polarization by improving the survival of the implanted endothelial progenitor cells (EPC) in an ischemic mouse model. These biomimetic phage nanofiber cues are considerably supportive of cell therapy, as they establish promising therapeutic extracellular de novo soft tissue niches for curing ischemic diseases.

Triboelectrification is a phenomenon that generates electric potential upon contact. Here, we report a viral particle capable of generating triboelectric potential. M13 bacteriophage is exploited to fabricate precisely defined chemical and physical structures. By genetically engineering the charged structures, we observe that more negatively charged phages can generate higher triboelectric potentials and can diffuse the electric charges faster than less negatively charged phages can. The computational results show that the glutamate-engineered phages lower the LUMO energy level so that they can easily accept electrons from other materials upon contact. A phage-based triboelectric nanogenerator is fabricated and it could produce ∼76 V and ∼5.1 μA, enough to power 30 light-emitting diodes upon a mechanical force application. Our biotechnological approach will be useful to understand the electrical behavior of biomaterials, harvest mechanical energy, and provide a novel modality to detect desired viruses in the future.

Molybdenum disulfide (MoS2) is a novel material with remarkable properties that is widely investigated for future applications in electronics, sensors, and smart materials. In this respect, a low cost, easy process, large-area mass production process is needed to obtain diverse structures and surface patterns of MoS2. Here, we demonstrate an effective MoS2 patterning process using substrate surface modification that can solve the difficulties encountered in previous studies. This technique utilizes the sulfur vacancies introduced during chemical exfoliation of MoS2 flakes. The MoS2 patterning is performed via surface modification with thiol molecules on the substrate in pre-designed shapes. The thiol (–SH) group required to bond MoS2 to the surface-modified substrate using (3-mercaptopropyl)trimethoxysilane was confirmed by FT-IR and the patterned MoS2 was confirmed by Raman shift. Through this process, a gas sensor was fabricated and its feasibility was confirmed to show its applicability to various applications MoS2.

We demonstrate a systematic approach to produce colored films based on hierarchical structures of peptide amphiphiles and their application for detecting gaseous aldehydes. Lysine-rich peptide amphiphiles (LRPAs) were designed to spontaneously self-assemble into nanofibers, which were deposited to form the colored films on solid substrates via controlled evaporation of the meniscus using a facile dipping-pulling method. The control of assembly conditions such as pH, concentration, and pulling speed enable the manifestation of film colors in a controllable way. When exposed to aldehyde gases, the color band pattern exhibited large color change due to structural change of the matrices which occur upon specific binding of aldehydes to lysine motifs. The statistical analysis of the color-change showed that the LRPA-based band patterns exhibit excellent selectivity toward aldehydes over non-aldehyde gases. We expect that our method will expedite the development of inexpensive, rapid and user-friendly aldehyde detection systems with on-site monitoring capabilities.

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−2, 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.

Supercapacitors are strong future candidates for energy storage devices owing to their high power density, fast charge–discharge rate, and long cycle stability. Here, a flexible supercapacitor with a large specific capacitance of 443 F g−1 at a scan rate of 2 mV s−1 is demonstrated using nanotube-reinforced polypyrrole nanowires with hollowed cavities grown vertically on a nanotube/graphene based film. Using these electrodes, we obtain improved capacitance, rate capability, and cycle stability for over 3000 cycles. The assembled all-solid-state supercapacitor exhibits excellent mechanical flexibility, with the capacity to endure a 180° bending angle along with a maximum specific and volumetric energy density of 7 W h kg−1 (8.2 mW h cm−3) at a power density of 75 W kg−1 (0.087 W cm−3), and it showed an energy density of 4.13 W h kg−1 (4.82 mW h cm−3) even at a high power density of 3.8 kW kg−1 (4.4 W cm−3). Also, it demonstrates a high cycling stability of 94.3% after 10 000 charge/discharge cycles at a current density of 10 A g−1. Finally, a foldable all-solid-state supercapacitor is demonstrated, which confirms the applicability of the reported supercapacitor for use in energy storage devices for future portable, foldable, or wearable electronics.

We demonstrate a unique system mainly composed of a carbon nanotube field-effect transistor (CNT-FET) integrated with malt extract agar (MEA) hydrogel for the real-time monitoring of microbial growth and activity. Consumption of nutrients and production of metabolites by microbial cells such as fungi or yeast results in the change of chemical properties of the hydrogel matrix, and this chemical change is detected by the underlying CNT-FET underneath the MEA hydrogel. In this study, we were able to distinguish the different growth phases (lag phase, log phase and stationary phase) of microbial organisms from the conductance measurement of the MEA-hybridized CNT-FET. Two fungal species (Aspergillus niger, Aspergillus versicolor), and one yeast species (Saccharomyces cerevisiae) were tested. The CNT-FET signals showed peculiar signal patterns according to the microbial species, enabling the classification of microbial species in terms of CNT-FET signal patterns. The CNT-FET signals were compared with pH change of the MEA hydrogel matrix, and the CNT-FET signal followed the microorganism activity more closely than the pH signal. We expect that this platform can serve as a suitable substitute of currently time-consuming, high-cost, and laborious microbial monitoring procedure and expedite the development of improved simultaneous monitoring of various fungal and/or bacterial organisms.

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.

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.

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 &ldquo, pulling&rdquo, 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.

The rapid and sensitive detection of allergenic fungal spores is of great interest owing to the potentially negative impact of these spores on personal and public health and safety. We present a simple and prompt colorimetric strategy for detecting Aspergillus niger based on interactions between fungal spores and gold nanoparticles (AuNPs) modified with a specific binding peptide. The A. niger spore-binding peptide ligand was identified by phage display screening, which exhibited enhanced affinity through multivalent effects with specificity over common airborne bacteria. Immobilization of peptide ligands on AuNPs enabled rapid binding to A. niger spores, resulting in a visible change in the color intensity of the supernatant after sedimentation of the spores. This simple colorimetric approach displayed a high sensitivity of ∼50 spores and a rapid detection time of

We report a method to grow structurally-controlled CdSe nanostructures by adopting Bi-mixed CdSe powder source to a catalyst-assisted chemical vapor deposition. Using this method, we synthesized Bi-doped CdSe nanocrystals with different shapes, such as nanocrystal film, nano-bumpy film, nanobelts, and nanowires. We fabricated a photodetector and a field-effect device using Bi-doped CdSe nanowires with high responsivity to white light. These results will offer a wide range of application possibilities in optoelectronic devices using CdSe nanostructures.

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 105, transconductance around 47 nS, and mobility around 0.175 cm2 V− 1 s− 1. 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 Vds, showing maximum photoresponsivity at Vds = 7 V. Electronic supplementary material The online version of this article (10.1186/s11671-018-2774-0) contains supplementary material, which is available to authorized users.

We demonstrate the formation of micro-patterned porous electronic channels of tin-doped indium oxide nanoparticles (ITO NPs) and their utilization as sensor transducers for the detection of NH 3 and NO 2 gas in air. The ITO NP channels were formed by dipping a molecularly patterned solid substrate into an ITO NP suspension and then pulling it vertically at a precisely controlled speed. The ITO NPs were self-assembled on the intended regions with high definition, as the NPs were selectively adsorbed on the polar SiO 2 regions avoiding the nonpolar regions. The thickness of the assembled ITO NP patterns could be modulated by controlling the pulling speed. The NPs formed a dense percolated network through which current could flow without any post-treatment such as heat annealing. By forming electrodes on the assembled ITO NP patterns, we fabricated sensor transducers for the detection of ammonia and nitrogen dioxide. The sensor showed a highly sensitive detection of NH 3 and NO 2 gas down to ppb-level. Furthermore, the sensor response changed in opposite direction to reducing NH 3 and oxidizing NO 2 gases, which shows that our sensor can be utilized in the selective detection of NH 3 and NO 2 .

Airborne fungus, including Aspergillus species, is one of the major causes of human asthma. Conventional immunoassay or DNA-sequencing techniques, although widely used, are usually labor-intensive, time-consuming and expensive. In this paper, we demonstrate a sensor for the rapid detection of Aspergillus niger, a well-known allergenic fungal species, using single-walled carbon nanotube (SWNT) field effect transistors (FETs) functionalized with pentameric antibodies that specifically bind to Aspergillus species. This strategy resulted in the real time and highly sensitive and selective detection of Aspergillus due to an electrostatic gating effect from the Aspergillus fungus. This mechanism is in contrast to a previously reported Aspergillus sensor, which was based on mobility modulation from Aspergillus adsorption. Also, our sensor shows a much wider detection range from 0.5 pg mL−1 to 10 μg mL−1 with a lower detection limit of 0.3 pg mL−1. The resulting SWNT-FET was able to selectively detect Aspergillus molds in the presence of more concentrated amounts of other mold species such as Alternaria alternata, Cladosporium cladosporioides, and Penicillium chrysogenum. We expect that our results can be used in real-time monitoring of the indoor air quality of a variety of public facilities for the elderly and children, who are more vulnerable to environmental biohazards.

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−2) 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.

We developed a method to prepare photoconductive channels of hybrid nanostructures based on Au nanohemispheres (Au NHs) and cadmium sulfide nanowires (CdS NWs) for photoconductive applications. The hybrid nanostructures exhibited enhanced absorbance, which was attributed to the strong electronic coupling between plasmons in Au NHs and excitons in CdS NWs. The photoconductive channels based on the hybrid nanostructures showed an increase in photocurrent level by ∼5× compared to bare CdS NWs. Because our strategy can be utilized to improve the photoconductivity of quite versatile photoconductive channels, it can be a powerful method for the development of various advanced optoelectronic and photovoltaic devices.

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., Improving the stability of perovskite solar cells remains crucial. Here, Ahn et al. show that trapped charges at grain boundaries induce the dissociation of the perovskite compound in the presence of moisture, and explain why degradation is irreversible under illumination and reversible in the dark.

Diverse biological tissues and structures that often exhibit remarkable physical and chemical properties can be found throughout nature. Starting from very few and simple building blocks such as collagen fibrils, nature effortlessly makes hierarchical and complex structures which are often hard to imitate with the current top-down microfabrication techniques. With the recent development of diverse assembly methods of nanobiomaterials, we have started to build biomimetic structures with diverse optical, mechanical, and electrical properties using bottom-up approaches. The properties of such biomimetic materials, when exposed to certain physical or chemical stimuli, sometimes change enough and may be utilized for sensing applications. For example, some filamentous viruses can be assembled into colorful films on solid substrates, the colors of which can change when exposed to organic solvents and volatile organic compounds. These same films, when applied with mechanical pressure, can exhibit piezoelectric properties, where mechanical pressure can be transduced to electrical signals, allowing the utilization of these structures as mechanical force sensors. In this chapter, we will discuss the current state of the biomimetic materials and structures for sensor applications, giving emphasis on hierarchical structures based on fiber building blocks.

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.

The shrinkage of pixel size down to sub-2 mu m 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 mu m 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 degrees, 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. (C)2016 Optical Society of America

A constant reactive power (Q) reserve (CQR) is measured by the difference between the maximum reactive power generation and its current. However, all reactive power sources must not affect the entire power system when severe contingencies occur. Thus, generators must be evaluated as to whether or not they will have an impact on the maximum permissible loading of buses. This definition considers some generators to still have reactive power reserves when the system faces voltage collapse. This remaining reactive power reserve, although available, cannot be used in an arbitrary manner. This paper proposes the concept of an effective reactive power reserve and it is calculated on the basis of a sensitivity analysis. The computed reactive power reserve is analyzed using static and dynamic simulations in bulk power systems.

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.

There have been extensive efforts to improve the properties of conventional metals such as electrical conductivity and rigidity. Here, we report a massive fabrication strategy for metal–carbon nanotube (CNT) laminate-based electrodes. In this method, CNTs were assembled by directed assembly strategy and a thin metal layer was formed by electrodeposition process, and those processes were repeated several times to fabricate multilayered structures. We demonstrated that metal–CNT laminates showed 42% enhancement in the conductivity compared to electrodeposited metals. Furthermore, its Young’s modulus was found to be 88% higher than pure bulk metals. Interestingly, the fabricated structures show I–V characteristics of metal wires while exhibiting typical noise characteristics of CNTs. Since our method uses only conventional microfabrication facilities, it can be readily used by the present microfabrication industry.

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.

Concentrated power demand can cause a fault current problem in a real power system. The Superconducting Fault Current Limiter (SFCL) application is one of the solutions for this problem. At present, many projects for the development of SFCLs are being done actively throughout the world. In Korea, LS Industrial Systems Co., Ltd. (LSIS) and the Korea Electric Power Research Institute (KEPRI) are jointly developing a 22.9 kV hybrid SFCL. It will be installed onto the Icheon 154 kV substation for an actual distribution power system operation in 2010. It is very important to carry out some feasibility studies for the application of SFCLs to the real power system. For the accuracy of the results of these studies, it is necessary to develop an analysis model which considers the real operating mechanism of the SFCLs. In this paper, we developed an SFCL analysis model using the PSCAD/EMTDC program, which is commonly used in the transient analysis of power systems. The developed model realizes the operating mechanisms of the SFCL, including the superconductor quenching property, for fault current and temperature, based on the experimental data from the 22.9 kV SFCL being developed by LSIS and KEPRI in Korea. This paper then conducts a technical analysis using the model and proposes specifications for the Current Limiting Resistor/Reactor (CLR) used for applying the SFCL to a real distribution power system in Korea.

We report on the direct thermal conductivity measurement of nanoscale nanolaminate material system from metallic thin-film (Al) and carbon-based low-dimensional material (swCNT). Such accurate measurement was made possible by realizing submicron measurement platform using micromaching techniques. Furthermore, by measuring the resonant response of such nanomechanical structures, we are able to deduce their thermal-elastic properties. We find that addition of swCNTs to Al thin-film greatly suppresses the overall coefficient of thermal expansion. On the other hand, addition of swCNTs has marginal effects on the resulting thermal conductivities.

Although advanced devices based on nanotubes (NTs) and nanowires (NWs) are drawing much attention, devices based on a single NT or NW are not suitable for general manufacturing purposes, as it is still extremely difficult to control the electronic properties, growth and alignment of individual NTs or NWs on an industrially reliable scale. An alternative strategy for implementing NTs or NWs in real-world devices is the use of NT- or NW-network-based structures containing a number of NTs or NWs. Herein, we review the recent progress in NT/NW-network-based integrated devices. The technology for NW/NT-network-based devices is supported by massive integration methods, such as directed assembly, printing and directed growth, and devices based on NW/NT networks display several unique properties, such as percolating conduction and scaling behaviors, that differentiate them from individual NT/NW-based devices. A variety of applications are possible for NT/NW networks, including transistors and sensors, all of which offer unique characteristics for use in integrated nanoelectronics.

This paper presents a simple and sensitive method for the real-time detection of a prostate cancer marker (PSA-ACT complex) through label-free protein biosensors based on a carbon nanotube field effect transistor (CNT-FET). Herein, the CNT-FET was functionalized with a solution containing various linker-to-spacer ratios, the binding event of the target PSA-ACT complex onto the receptor detected by monitoring the gating effect caused by charges in the target PSA-ACT complex. Since the biosensors were used in a buffer solution, it was crucial to control the distance between the receptors through introduction of linkers and spacers so that the charged target PSA-ACT complex could easily approach the CNT surface within the Debye length to give a large gating effect. The results show that CNT-FET biosensors modified with only linkers could not detect target proteins unless a very high concentration of the PSA-ACT complex solution (approximately 500 ng/ml) was injected, while those modified with a 1:3 ratio of linker-to-spacer could detect 1.0 ng/ml without any pretreatment. Moreover, our linker and spacer-modified CNT-FET could successfully block non-target proteins and selectively detect the target protein in human serum. Significantly, this strategy can be applied to general antibody-based detection schemes and enables production of very simple and sensitive electronic biosensors to detect clinically important biomarkers for disease diagnosis.

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.

Composites with added carbon nanotubes are known for their improved mechanical strength. Laminates of thin films of aluminium and carbon nanotubes are now used for the fabrication of micromechanical resonators with significantly enhanced mechanical properties. At micro- and nanoscales, materials with high Young’s moduli and low densities are of great interest for high-frequency micromechanical resonator devices1,2,3,4,5,6,7,8. Incorporating carbon nanotubes (CNTs), with their unmatched properties, has added functionality to many man-made composites9,10,11. We report on the fabrication of ≤100-nm-thick laminates by sputter-deposition of aluminium onto a two-dimensional single-walled CNT network12,13. These nanolaminates—composed of Al, its native oxide Al2O3 and CNTs—are fashioned, in a scalable manner, into suspended doubly clamped micromechanical beams. Dynamic flexural measurements show marked increases in resonant frequencies for nanolaminates with Al–CNT laminae. Such increases, further supported by quasi-static flexural measurements, are partly attributable to enhancements in elastic properties arising from the addition of CNTs. As a consequence, these nanolaminate micromechanical resonators show significant suppression of mechanical nonlinearity and enhanced strength, both of which are advantageous for practical applications and analogous to biological nanocomposites, similarly composed of high-aspect-ratio, mechanically superior mineral platelets in a soft protein matrix14.

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.

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.

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. Electronic supplementary material The online version of this article (doi:10.1186/s11671-015-1037-6) contains supplementary material, which is available to authorized users.

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. Electronic supplementary material The online version of this article (doi:10.1186/s11671-015-0729-2) contains supplementary material, which is available to authorized users.

Advanced electronic devices based on carbon nanotubes (NTs) and various types of nanowires (NWs) could have a role in next-generation semiconductor architectures. However, the lack of a general fabrication method has held back the development of these devices for practical applications. Here we report an assembly strategy for devices based on NTs and NWs. Inert surface molecular patterns were used to direct the adsorption and alignment of NTs and NWs on bare surfaces to form device structures without the use of linker molecules. Substrate bias further enhanced the amount of NT and NW adsorption. Significantly, as all the processing steps can be performed with conventional microfabrication facilities, our method is readily accessible to the present semiconductor industry. We use this method to demonstrate large-scale assembly of NT- and NW-based integrated devices and their applications. We also provide extensive analysis regarding the reliability of the method.

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.

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), with90% 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.

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.