Microheater with copper nanofiber network via electrospinning and electroless deposition.

In this report, we present the development of a copper nanofiber network-based microheater, designed for applications in electron microscopes, gas sensing, and cell culture platforms. The seed layer, essential for electroless deposition, was fabricated through the electrospinning of a palladium-contained polyvinylpyrrolidone solution followed by a heat treatment. This process minimized the contact resistance between nanofibers.

Review: Sensors for Biosignal/Health Monitoring in Electronic Skin.

Skin is the largest sensory organ and receives information from external stimuli. Human body signals have been monitored using wearable devices, which are gradually being replaced by electronic skin (E-skin). We assessed the basic technologies from two points of view: sensing mechanism and material.

Highly-robust, solution-processed flexible transparent electrodes with a junction-free electrospun nanofiber network.

Flexible transparent electrodes (FTEs) are widely used in a variety of applications, including flexible displays and wearable devices. Important factors in FTE design include active control of electrical sheet resistance, optical transparency and mechanical flexibility. Because these factors are inversely proportional to one another, it is essential to develop a technique that maintains flexibility while actively controlling the sheet resistance and transparency for a variety of applications.

Fabrication of a Novel Nanofluidic Device Featuring ZnO Nanochannels.

We developed a novel fabrication method for nanochannels that are easily scaled up to mass production by selectively growing zinc oxide (ZnO) nanostructures and covering using a flat PDMS surface to make hollow nanochannels. Nanochannels are used in the biotechnological and environmental fields, being employed for DNA analysis and water purification, due to their unique features of capillary-induced negative pressure and an electrical double-layer overlap. However, existing nanochannel fabrication methods are complicated, costly, and not amenable to mass production.

Recent Progress on Microelectrodes in Neural Interfaces.

Brain‒machine interface (BMI) is a promising technology that looks set to contribute to the development of artificial limbs and new input devices by integrating various recent technological advances, including neural electrodes, wireless communication, signal analysis, and robot control. Neural electrodes are a key technological component of BMI, as they can record the rapid and numerous signals emitted by neurons. To receive stable, consistent, and accurate signals, electrodes are designed in accordance with various templates using diverse materials.

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

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.

Fabrication of Optical Switching Patterns with Structural Colored Microfibers.

Structural color was generated using electrospinning and hydrothermal growth of zinc oxide (ZnO). An aligned seed layer was prepared by electrospinning, and the hydrothermal growth time control was adjusted to generate various structural colors. The structural color changed according to the angle of the incident light.

Electrospinning onto Insulating Substrates by Controlling Surface Wettability and Humidity.

We report a simple method for electrospinning polymers onto flexible, insulating substrates by controlling the wettability of the substrate surface. Water molecules were adsorbed onto the surface of a hydrophilic polymer substrate by increasing the local humidity around the substrate. The adsorbed water was used as the ground electrode for electrospinning.

Bioinspired Structural Colors Fabricated with ZnO Quasi-Ordered Nanostructures.

Despite their advantages in different applications, structural colors are difficult to use because of the inability to change a structural color once it is implemented, as well as their high fabrication costs; implementing multiple structural colors simultaneously on one substrate is a challenge as well. In this study, structural colors were reproduced using quasi-ordered scattering to mitigate these issues. To this end, a ZnO flower-like structure having unimodal distributions of size and spacing was fabricated by ZnO hydrothermal growth.

Reliable Diameter Control of Carbon Nanotube Nanobundles 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.

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.

Simultaneous imaging of the topography and electrochemical activity of a 2D carbon nanotube network using a dual functional L-shaped nanoprobe.

The application of nanomaterials for biosensors and fuel cells is becoming more common, but it requires an understanding of the relationship between the structure and electrochemical characteristics of the materials at the nanoscale. Herein, we report the development of scanning electrochemical microscopy-atomic force microscopy (SECM-AFM) nanoprobes for collecting spatially resolved data regarding the electrochemical activity of nanomaterials such as carbon nanotube (CNT) networks. The fabrication of the nanoprobe begins with the integration of a CNT-bundle wire into a conventional AFM probe followed by the deposition of an insulating layer and cutting of the probe end.

Cell behaviour on a polyaniline nanoprotrusion structure surface.

The extracellular matrix provides mechanical support and affects cell behaviour. Nanoscale structures have been shown to have functions similar to the extracellular matrix. In this study, we fabricated nanoprotrusion structures with polyaniline as cell culture plates using a simple method and determined the effects of these nanoprotrusion structures on cells.

Three-dimensionally designed anti-reflective silicon surfaces for perfect absorption of light.

An ideal black material absorbs light perfectly over all wavelengths and is totally nonreflective. Material and structural design are crucial to the management of reflectivity. Here, we report a three-dimensionally designed (3D) silicon structure consisting of silicon pillars.

Carbon-nanotube-modified electrodes for highly efficient acute neural recording.

Microelectrodes are widely used for monitoring neural activities in various neurobiological studies. The size of the neural electrode is an important factor in determining the signal-to-noise ratio (SNR) of recorded neural signals and, thereby, the recording sensitivity. Here, it is demonstrated that commercial tungsten microelectrodes can be modified with carbon nanotubes (CNTs), resulting in a highly sensitive recording ability.

Replicable and shape-controllable fabrication of electrospun fibrous scaffolds for tissue engineering.

Controlling the architecture of electrospun fibers is one of the key issues in tissue engineering. This report describes a rapid and reproducible patterning method for the fabrication of an electrospun fibrous scaffold. The electrospun fibers were deposited on a patterned electrode.

Fabrication of conducting polymer micro/nanostructures coated with Au nanoparticles for electrochemical sensors.

Polypyrrole (PPy) micro/nanostructures coated with Au nanoparticles were prepared by electropolymerization and electro-deposition. Two types of PPy structures, micro-embossed and nanowire forest, were synthesized on patterned gold electrodes using different aqueous solutions, and Au nanoparticles were coated onto the PPy micro/nanostructure surface. The size of the Au nanoparticles ranged from 10 to 100 nm, and the maximum density of the nanoparticles was 73 particles/microm2.

Organic electrochemical transistors based on a dielectrophoretically aligned nanowire array.

In this study, we synthesized an organic electrochemical transistor (OECT) using dielectrophoresis of a carbon nanotube-Nafion (CNT-Nafion) suspension. Dielectrophoretically aligned nanowires formed a one-dimensional submicron bundle between triangular electrodes. The CNT-Nafion composite nanowire bundles showed p-type semiconductor characteristics.

Fabrication of functional micro- and nanoneedle electrodes using a carbon nanotube template and electrodeposition.

Carbon nanotube (CNT) is an attractive material for needle-like conducting electrodes because it has high electrical conductivity and mechanical strength. However, CNTs cannot provide the desired properties in certain applications. To obtain micro- and nanoneedles having the desired properties, it is necessary to fabricate functional needles using various other materials.

Superhydrophobic nanostructured silicon surfaces with controllable broadband reflectance.

Nanostructured superhydrophobic silicon surfaces with tunable reflectance are fabricated via a simple maskless deep reactive-ion etching process. By controlling the scale of the high-aspect-ratio nanostructures on a wafer-scale surface, surface reflectance is maximized or minimized over the UV-vis-IR range while maintaining superhydrophobic properties.

Replicable multilayered nanofibrous patterns on a flexible film.

This report describes a simple method for the direct patterning of nanofibers on a flexible, insulating film. The method allows the replication of nanofibrous patterns from a single patterned electrode and the fabrication of multilayered patterns from various electrode shapes. The architecture of the fibrous patterns can be controlled by tailoring the ambient humidity, thickness of the insulating film, polarity of the electrode, and size of the patterned electrode.

Real-time, step-wise, electrical detection of protein molecules using dielectrophoretically aligned SWNT-film FET aptasensors.

Aptamer functionalized addressable SWNT-film arrays between cantilever electrodes were successfully developed for biosensor applications. Dielectrophoretically aligned SWNT suspended films made possible highly specific and rapid detection of target proteins with a large binding surface area. Thrombin aptamer immobilized SWNT-film FET biosensor resulted in a real-time, label-free, and electrical detection of thrombin molecules down to a concentration of ca.