Micro and Nano Machining by Electro-Physical and Chemical Processes

Thin-film technology is widely implemented in numerous applications1. Although flat substrates are commonly used, we report on the advantages of using curved surfaces as a substrate. The curvature induces a lateral film-thickness variation that allows alteration of the properties of the deposited material2,3. Based on this concept, a variety of implementations in materials science can be expected. As an example, a topographic pattern formed of spherical nanoparticles4,5 is combined with magnetic multilayer film deposition. Here we show that this combination leads to a new class of magnetic material with a unique combination of remarkable properties: The so-formed nanostructures are monodisperse, magnetically isolated, single-domain, and reveal a uniform magnetic anisotropy with an unexpected switching behaviour induced by their spherical shape. Furthermore, changing the deposition angle with respect to the particle ensemble allows tailoring of the orientation of the magnetic anisotropy, which results in tilted nanostructure material.

http://absimage.aps.org/image/MAR06/MWS_MAR06-2005-000595.pdf

Magnetic multilayers on nanospheres

In this paper, electrochemical machining (ECM) for fabricating micro structures is presented. By applying ultra short pulses, dissolution of a workpiece can be restricted to the region very close to an electrode. Using this method, 3D micro structures were machined on stainless steel. Good surface quality of the structures was obtained in the low concentration electrolyte, 0.1 M H2SO4. In ECM, when the machining depth increases, structures taper. To reduce the taper, a disc-type electrode is introduced. By electrochemical milling, various 3D micro structures including a hemisphere with 60 µm diameter were fabricated.

https://iopscience.iop.org/article/10.1088/0960-1317/15/1/019/pdf

Micro electrochemical milling

Pulse polymerized polypyrrole electrodes for high energy density electrochemical supercapacitor

Electrochemical micromachining with ultrashort voltage pulses–a versatile method with lithographical precision

Application of ultrashort voltage pulses to a tiny tool electrode under suitable electrochemical conditions enables precise three-dimensional machining of stainless steel In order to reach submicrometer precision and high processing speed, the formation of a passive layer on the workpiece surface during the machining process has to be prevented by proper choice of the electrolyte Mixtures of concentrated hydrofluoric and hydrochloric acid are well suited in this respect and allow the automated machining of complicated three-dimensional microelements The dependence of the machining precision on pulse duration and pulse amplitude was investigated in detail

/pdf/electrochemical-micromachining-of-stainless-steel-by-3w9ompr147.pdf

Electrochemical Micromachining of Stainless Steel by Ultrashort Voltage Pulses

An electrochemical pulse technique enables the fabrication of three-dimensional microelements from stainless steel. The method is based on the application of ultrashort (nanosecond) voltage pulses, whereupon electrochemical reactions are locally confined with submicrometer precision. Employing properly shaped tool electrodes enables the machining of freestanding cantilevers or microstructures directly to a metal sheet. Due to gentle removal of the material, the grain structure of the material is revealed without any chemical or mechanical modifications. This is demonstrated by measuring the vibration frequency of a cantilever, and agrees well with the value derived from the bulk material properties.

/pdf/electrochemical-machining-of-stainless-steel-microelements-1gecjnn872.pdf

Electrochemical machining of stainless steel microelements with ultrashort voltage pulses

Cu/Co/Cu trilayers have been deposited on nanoporous alumina membranes. Magnetic properties of the resulting Co antidot arrays are investigated using SQUID magnetometry. Hysteresis loops of these arrays show two-step magnetization reversal. In addition, exchange bias is observed, whether the cooling field is applied within or perpendicular to the surface plane. In the former case, the exchange bias changes sign close to the blocking temperature, and becomes positive. We attribute these effects to the local, crescent shape of the Co films, induced by the surface morphology of the alumina membranes. This morphology leads to a three-dimensional magnetization distribution at the nanoscale.

3D magnetization profile and multi-axes exchange bias in Co antidot arrays

Magnetic properties of Cu/Co/Cu trilayers deposited on nanoporous alumina membranes are investigated using a superconducting quantum interference device. Hysteresis loops of the resulting Co antidot arrays show two-step magnetization reversal. Due to oxidation when samples are exposed to air, CoO forms and exchange bias is observed, whether the cooling field is applied within or perpendicular to the surface plane. In the former case, the exchange bias changes sign close to the blocking temperature of Co/CoO. We attribute these effects to the local, crescent shape of the Co films induced by the surface morphology of the membranes, which leads to a three-dimensional magnetization distribution.

Laurent Cagnon

Papers

Electrochemical Micromachining of Stainless Steel by Ultrashort Voltage Pulses

Electrochemical machining of stainless steel microelements with ultrashort voltage pulses

3D magnetization profile and multi-axes exchange bias in Co antidot arrays

Three-dimensional magnetization profile and multiaxes exchange bias in Co antidot arrays