AC electrohydrodynamic Landau–Squire flows around a conducting nanotip

Utilizing the joint singular natures of electric field and hydrodynamic flow around a sharp nanotip, we report new electrohydrodynamic Landau–Squire-type flows under the actions of alternating current (AC) electric fields, markedly different from the classical Landau–Squire flow generated by pump discharge using nanotubes or nanopores. Making use of the locally diverging electric field prevailing near the conical tip, we are able to generate a diversity of AC electrohydrodynamic flows with the signature of a 1/r point-force-like decay at distance r from the tip. Specifically, we find AC electrothermal jet and Faradaic streaming out of the tip at applied frequencies in the MHz and 102 Hz regimes, respectively. Yet at intermediate frequencies of 1–100 kHz, the jet flow can be reversed to an AC electro-osmotic impinging flow. The characteristics of these AC jet flows are very distinct from AC flows over planar electrodes. For the AC electrothermal jet, we observe experimentally that its speed varies with the driving voltage V as V3, in contrast to the common V4 dependence according to the classical theory reported by Ramos et al. (J. Phys. D: Appl. Phys, vol. 31, 1998, pp. 2338–2353). Additionally, the flow speed does not increase with the solution conductivity as commonly thought. These experimental findings can be rationalized by means of local Joule heating and double layer charging mechanisms in such a way that the nanotip actually becomes a local hotspot charged with heated tangential currents. The measured speed of the AC Faradaic streaming is found to vary as V3/2 logV, which can be interpreted by the local Faradaic leakage in balance with tangential conduction. These unusual flow characteristics signify that a conical electrode geometry may fundamentally alter the features of AC electrohydrodynamic flows. Such peculiar electrohydrodynamic flows may also provide new avenues for expediting molecular sensing or sample transport in prevalent electrochemical or microfluidic applications.

Малогабаритный многоканальный анализатор энергии заряженных частиц на основе конусного разрезанного электрода

An electrostatic compact analyzer for obtaining the energy spectrum and for detecting simultaneously charged particles in a wide energy range, which is especially important for fast processes in various materials, has been proposed and designed. The energy analyzer consists of an outer conical electrode with closed end faces, which is cut into parts and fed in accordance with the law of odd numbers, and an grounded inner electrode on the surface of which charged particle beams with a wide energy range are focused. To increase the sharpness of low-energy beam focusing, an auxiliary, very small conical electrode is introduced. In spite of the small energy dispersion factor, the optimal regime of operation of the proposed analyzer with energy resolution not worse than 1% has been found.

Study of the secondary electron emission coefficient using disc and conical electrodes

In this work, glow discharge is formed by similar disc and conical electrode shapes from aluminum material at constant anode–cathode gap distance equal to 10 cm. The breakdown voltage and discharge current against the pressure × distance are measured at different pressures. The secondary electron emission coefficient is calculated using Townsend’s secondary ionization coefficient equation. A comparison is made between the breakdown voltage, discharge current, and secondary electron emission coefficient using disc and conical anode–cathode electrodes. Hence with a product of pressure and distance equal to 6 Torr cm, the secondary electron emission coefficient value of conical shape is higher than for the disc shape.

Arithmetic and Experimental Study of Fix-Length Compensation Based on Conical Bottom Shape of Electrode in Micro-EDM

Micro-electrical discharge machining (EDM) milling with a simple-shaped electrode is an effective machining method to fabricate three-dimensional micro parts and micro structures. However, the serious electrode wear occurring in the machining process significantly deteriorates the geometrical accuracy of the products. Fix-length compensation method is a real-time and effective electrode compensation method. During the EDM process with fix-length compensation, the bottom of cylindrical electrode trends to be conical shape. The formation process of conical electrode is illustrated by experiments and analysis. Once the cone angle of the electrode is formed, the angle of conical electrode keeps stable. Further experiments reveal the relationship between the cone angle and the layer thickness. The experiment results are in accordance with theoretical results, which provide theoretical reference for ED-milling compensation. The wear model based on fix-length compensation method with conical electrode is established and the corresponding arithmetic of compensation length is derived. Experiments show that the arithmetic equation about compensation length has high accuracy. A demonstration cavity is machined with this compensation method. The effectiveness of this compensation method is verified.

Designed PCL Nanofibers Fabricated Using a Modified Electrohydrodynamic Process for Tissue Engineering

An ideal scaffold should have good mechanical properties and provide a biologically functional implant site. Considering their large surface area, high porosity, and good interconnectivity of pores, electrospun micro-∕nanofibers have good potential as biomimic scaffolds. In this study, various poly(ε-carprolactone) webs consisting of uniaxially oriented micro-∕nanofibers were produced using an electrohydrodynamic process (electrospinning) with a conical electrode and two-axis collector. The oriented fibrous web showed mechanical orthotropic properties, which might be important for designing engineering scaffolds that mimic natural tissues, such as a blood vessel or ligament, which have orthotropic mechanical properties. In addition, the fabricated mats, which were electrospun using computer-assisted design, had good hydrophilic and good cellular behavior compared to a random fiber mat.