Reliable diameter control of carbon nanotube nanowires using withdrawal velocity

Carbon nanotube (CNT) nanobundles are widely used in nanoscale imaging, fabrication, and electrochemical and biological sensing. The diameter of CNT nanobundles should be controlled precisely, because it is an important factor in determining electrode performance. Here, we fabricated CNT nanobundles on tungsten tips using dielectrophoresis (DEP) force and controlled their diameters by varying the withdrawal velocity of the tungsten tips. Withdrawal velocity pulling away from the liquid-air interface could be an important, reliable parameter to control the diameter of CNT nanobundles. The withdrawal velocity was controlled automatically and precisely with a one-dimensional motorized stage. The effect of the withdrawal velocity on the diameter of CNT nanobundles was analyzed theoretically and compared with the experimental results. Based on the attachment efficiency, the withdrawal velocity is inversely proportional to the diameter of the CNT nanobundles; this has been demonstrated experimentally. Control of the withdrawal velocity will play an important role in fabricating CNT nanobundles using DEP phenomena.110Ysciescopu

One-directional flow of ionic solutions along fine electrodes under an alternating current electric field

Electric fields are widely used for controlling liquids in various research fields. To control a liquid, an alternating current (AC) electric field can offer unique advantages over a direct current (DC) electric field, such as fast and programmable flows and reduced side effects, namely the generation of gas bubbles. Here, we demonstrate one-directional flow along carbon nanotube nanowires under an AC electric field, with no additional equipment or frequency matching. This phenomenon has the following characteristics: First, the flow rates of the transported liquid were changed by altering the frequency showing Gaussian behaviour. Second, a particular frequency generated maximum liquid flow. Third, flow rates with an AC electric field (approximately nanolitre per minute) were much faster than those of a DC electric field (approximately picolitre per minute). Fourth, the flow rates could be controlled by changing the applied voltage, frequency, ion concentration of the solution and offset voltage. Our finding of microfluidic control using an AC electric field could provide a new method for controlling liquids in various research fields

Ionic liquid flow along the carbon nanotube with DC electric field

Liquid pumping can occur along the outer surface of an electrode under a DC electric field. For biological applications, a better understanding of the ionic solution pumping mechanism is required. Here, we fabricated CNT wire electrodes (CWEs) and tungsten wire electrodes (TWEs) of various diameters to assess an ionic solution pumping. A DC electric field created by a bias of several volts pumped the ionic solution in the direction of the negatively biased electrode. The resulting electroosmotic flow was attributed to the movement of an electric double layer near the electrode, and the flow rates along the CWEs were on the order of picoliters per minute. According to electric field analysis, the z-directional electric field around the meniscus of the small electrode was more concentrated than that of the larger electrode. Thus, the pumping effect increased as the electrode diameter decreased. Interestingly in CWEs, the initiating voltage for liquid pumping did not change with increasing diameter, up to 20 mu m. We classified into three pumping zones, according to the initiating voltage and faradaic reaction. Liquid pumping using the CWEs could provide a new method for biological studies with adoptable flow rates and a larger 'Recommended pumping zone'.open116sciescopu

Smart sensor systems for wearable electronic devices

Wearable human interaction devices are technologies with various applications for improving human comfort, convenience and security and for monitoring health conditions. Healthcare monitoring includes caring for the welfare of every person, which includes early diagnosis of diseases, real-time monitoring of the effects of treatment, therapy, and the general monitoring of the conditions of people's health. As a result, wearable electronic devices are receiving greater attention because of their facile interaction with the human body, such as monitoring heart rate, wrist pulse, motion, blood pressure, intraocular pressure, and other health-related conditions. In this paper, various smart sensors and wireless systems are reviewed, the current state of research related to such systems is reported, and their detection mechanisms are compared. Our focus was limited to wearable and attachable sensors. Section 1 presents the various smart sensors. In Section 2, we describe multiplexed sensors that can monitor several physiological signals simultaneously. Section 3 provides a discussion about short-range wireless systems including bluetooth, near field communication (NFC), and resonance antenna systems for wearable electronic devices

The enhancement of the CNT nanowire by acylation reaction

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Junction-free Flat Copper Nanofiber Network-based Transparent Heater with High Transparency, High Conductivity, and High Temperature

Abstract Transparent conducting electrodes (TCE) are widely used in a variety of applications including displays, light-emitting diodes (LEDS), and solar cells. An important factor in TCE design is active control of the sheet resistance and transparency; as these are inversely proportional, it is essential to develop a technology that can maintain high transparency, while actively controlling sheet resistance, for a range of applications. Here, a nanofiber network was fabricated based on direct electrospinning onto a three-dimensional (3-D) complex substrate; flat metal electrodes without junction resistance were produced using heat treatment and electroless deposition. The fabricated transparent electrode exhibited a transparency of over 90% over the entire visible light range and a sheet resistance of 4.9 ohms/sq. Adhesion between the electrode and substrate was superior to other electrospinning-based transparent electrodes. The performance of the transparent electrode was verified by measurements taken while using the electrode as a heater; a maximum temperature of 210 °C was achieved. The proposed copper nanofiber-based heater electrode offers the advantages of transparency as well as application to complex 3-D surfaces

Dispensing small droplets with low generating power

Dispensed small droplets are widely used in analyses of small organisms in various bioapplications. The generating power used to induce "flying beads" of dispensed small droplets should be sufficiently low to guarantee the safety of the organisms. In this study, we fabricated carbon nanotube (CNT) nanobundles electroplated with gold nanoparticles. Small droplets were generated by the repulsive force in an ion-concentrated zone; in this region, the droplets were generated at lower voltages due to the higher ion concentration. The generating power was examined as a function of electrode diameter (0.6, 20, and 500 mu m) and decreased significantly with electrode size, specifically 0.007 mW for the 0.6-mu m-diameter electrode compared with 0.017 W for the 20-mu m-diameter electrode. The beads expelled from the mother droplet at 0.007 mW had an initial velocity of similar to 2 m min(-1). This technique is expected to be particularly useful for the analysis of very small analytes.ungraded11sciescopu

Direct-write printing for producing biomimetic patterns with self-aligned neurites

Various techniques have been introduced to produce artificial neural constructs with aligned architectures, which have shown significantly improved neural function and regeneration. However, the techniques used to fabricate sophisticated patterns with aligned neurites show some limitations. Herein, we developed a direct-write printing process capable of producing versatile biomimetic patterns with aligned neurites using multiple cell types. Fibrin-based bio-ink was prepared for patterning with neuronal cells. After printing fixed pillars at both ends, microfibers were fabricated between the pillars using PC-12 neuronal cell/normal human dermal fibroblast (NHDF)-laden bio-ink and a direct-write printer. After two weeks of differentiation, aligned neurites were induced by the contractile force of the printed cells. We found that this self-induced alignment improved PC-12 differentiation and that neurite alignment could be adjusted by controlling the NHDF and bio-ink concentration. The bundle of cell-laden microfibers also showed uniform formation of neurites and synapse-like structures. Finally, we demonstrated the usefulness of the printing process by fabricating a Y-shaped branch and six-layered pattern. The six-layered pattern mimicking cerebral cortex tissue was produced by precise printing of two different colored cells. These results indicate that versatile biomimetic neural constructs composed of multiple cell types can be produced by our new direct-write printing process

CNT-Au nanocomposite deposition on gold microelectrodes for improved neural recordings

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