A Zeta (zeta)-Pipet Tip to Reduce the Spontaneously Induced Electrical Charge of a Dispensed Aqueous Droplet

We report that the zeta potential of a pipet tip's inner surface is one of the crucial parameters for controlling the electrical charge of the dispensed droplet. Since the charge is unexpected and undesirable for most experiments in various fields of science and, thereby, they can cause unsuspected problems, reducing the charge on a dispensed droplet is important for the results of pipetting-based experiments. We fabricate a graphene-based nanocomposite-coated pipet tip, which we called a zeta-pipet tip, as a proof-of-concept example to reduce the zeta potential of the pipet tip's inner surface. The fabricated zeta-pipet tip can successfully mitigate the undesired droplet separation in the droplet merging experiments in an oil bath, which is one of the unexpected effects caused by the electrification. The findings of this study provide helpful guidelines for researchers in many fields of science and technology, who utilize a pipet tip in their respective experiments.X111112Ysciescopu

Capacitive Control of Spontaneously Induced Electrical Charge of Droplet by Electric Field-Assisted Pipetting

The spontaneously generated electrical charge of a droplet dispensed from conventional pipetting is undesirable and unpredictable for most experiments that use pipetting. Hence, a method for controlling and removing the electrical charge needs to be developed. In this study, by using the electrode-deposited pipet tip (E-pipet tip), the charge-controlling system is newly developed and the electrical charge of a droplet is precisely controlled. The effect of electrolyte concentration and volume of the transferred solution to the electrical charge of a dispensed droplet is theoretically and experimentally investigated by using the equivalent capacitor model. Furthermore, a proof-of-concept example of the self-alignment and self-assembly of sequentially dispensed multiple droplets is demonstrated as one of the potential applications. Given that the electrical charge of the various aqueous droplets can be precisely and simply controlled, the fabricated E-pipet tip can be broadly utilized not only as a general charge-controlling platform of aqueous droplets but also as a powerful tool to explore fundamental scientific research regarding electrical charge of a droplet, such as the surface oscillation and evaporation of charged droplets.1143Ysciescopu

Complex 3D microfluidic architectures formed by mechanically guided compressive buckling.

Microfluidic technologies have wide-ranging applications in chemical analysis systems, drug delivery platforms, and artificial vascular networks. This latter area is particularly relevant to 3D cell cultures, engineered tissues, and artificial organs, where volumetric capabilities in fluid distribution are essential. Existing schemes for fabricating 3D microfluidic structures are constrained in realizing desired layout designs, producing physiologically relevant microvascular structures, and/or integrating active electronic/optoelectronic/microelectromechanical components for sensing and actuation. This paper presents a guided assembly approach that bypasses these limitations to yield complex 3D microvascular structures from 2D precursors that exploit the full sophistication of 2D fabrication methods. The capabilities extend to feature sizes <5 μm, in extended arrays and with various embedded sensors and actuators, across wide ranges of overall dimensions, in a parallel, high-throughput process. Examples include 3D microvascular networks with sophisticated layouts, deterministically designed and constructed to expand the geometries and operating features of artificial vascular networks

Development of Pipette Tips to Control the Spontaneously Generated Charge of Droplets

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Utilization of Thermoplastic Fluoropolymers for One-step Fabrication of Triboelectric Replicable Nanogenerators

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Fabrication o fcomb-shape single electrode based triboelectric nanogenerators via hot embossing process for two-directional contact energy harvesting

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Comb-shaped electrode-based triboelectric nanogenerators for bi-directional mechanical energy harvesting

Triboelectric nanogenerators (TENGs), which utilize coupling of contact electrification and electric induction to effectively harvest the mechanical energy around us, have attracted much attention due to their advantages such as simple design and high accessibility. Herein, we report new types of TENGs containing comb-shaped electrode, which are fabricated with a simple thermal nanoimprinting process where a commercially-available metal mesh was used as a stamp to simply impart microtopography on the TENGs to increase electrical output performance. The fabricated TENG with the comb-shaped electrode enables to harvest bi-directional mechanical energy (including both lateral and vertical contact/separation), which can be a new strategy to efficiently harvest the energy from complex real mechanical motions. The TENG with the comb-shaped electrode generates a short circuit current (I-SC) of 85 nA and an open circuit voltage (V-OC) of 6.4 V under the lateral contact/separation, which are increased up to 850% and 1600%, respectively, compared to the TENGs with the conventional rectangular electrode. The TENG with comb-shaped electrode is also found to harvest energy of I-SC of 339 nA and V-OC, of 31 Vat a pressing frequency of 0.5 Hz and force of 58.8 N under the vertical contact/separation without significant loss of electrical output performance compared with the TENG with the conventional rectangular electrode. The results indicate that the comb-shaped electrode would be a powerful (potential) candidate of electrode shape of the TENG to harvest the energy from real mechanical motions. (C) 2017 Elsevier B.V. All rights reserved.1120sciescopu