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. With the development of microelectromechanical systems (MEMS) technology, electrodes have become more integrated, and their performance has gradually evolved through surface modification and advances in biotechnology. In this paper, we review the development of the extracellular/intracellular type of in vitro microelectrode array (MEA) to investigate neural interface technology and the penetrating/surface (non-penetrating) type of in vivo electrodes. We briefly examine the history and study the recently developed shapes and various uses of the electrode. Also, electrode materials and surface modification techniques are reviewed to measure high-quality neural signals that can be used in BMI.

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The flexible transparent electrode of this study used electrospinning and electroless deposition, which is a fabrication method to remove contact resistance at the nanofiber intersection and fabricate large-area electrode.

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. This fabricated nanostructure has a thickness on the order of 10 nm and a diameter on the order of 10 nm. The thickness and diameter increase in proportion with the synthesis time (thickness growth rate = 43 nm/min, diameter growth rate = 20 nm/min). The shape of the nanostructure can be easily tuned by simply adjusting the synthesis and etching times. This method combines the advantages of top-down and bottom-up synthetic approaches in that the structural color can be continuously modified once fabricated.

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.

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 electro-osmotic 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 μm. 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’.

A 65-year-old woman with a deeply infiltrating basal cell carcinoma in the right ala underwent full-thickness excision of most of the ala, including the alar rim, crease, and the adjacent cheek, leaving a 'through-and-through' defect. Reconstruction was performed by using the reverse nasolabial flap and a cartilage graft across the alar defect, harvested from the concha, to prevent nostril collapse and to maintain the alar shape. The reverse or turnover nasolabial flap is a variant of the conventional nasolabial flap; however, it may be more suited for the repair of a full-thickness, lateral alar defect. The reverse nasolabial flap functions both as an inner liner and an outer cover and the repair is performed as a single-stage procedure. Furthermore, this flap can provide both excellent function and excellent cosmetic outcome.

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. The electrospun fibers were deposited only onto hydrophilic areas of the substrate, allowing for patterning through wettability control. Direct writing of polymer fiber was also possible through near-field electrospinning onto a hydrophilic surface.Electronic supplementary materialThe online version of this article (10.1186/s11671-017-2380-6) contains supplementary material, which is available to authorized users.