This protocol provides an introduction to soft lithography--a collection of techniques based on printing, molding and embossing with an elastomeric stamp. Soft lithography provides access to three-dimensional and curved structures, tolerates a wide variety of materials, generates well-defined and controllable surface chemistries, and is generally compatible with biological applications. It is also low in cost, experimentally convenient and has emerged as a technology useful for a number of applications that include cell biology, microfluidics, lab-on-a-chip, microelectromechanical systems and flexible electronics/photonics. As examples, here we focus on three of the commonly used soft lithographic techniques: (i) microcontact printing of alkanethiols and proteins on gold-coated and glass substrates; (ii) replica molding for fabrication of microfluidic devices in poly(dimethyl siloxane), and of nanostructures in polyurethane or epoxy; and (iii) solvent-assisted micromolding of nanostructures in poly(methyl methacrylate).

/pdf/soft-lithography-for-micro-and-nanoscale-patterning-21e1ngmrqv.pdf

Soft lithography for micro- and nanoscale patterning

Ordered magnetic nanostructures: fabrication and properties

Nanofabrication of magnetic storage media, where servo marks, discrete tracks or individual islands are defined, offer the prospect for improved performance and increased areal density. However, this increase in performance will require that new and additional processes be introduced into disk manufacturing. We review here the fundamental patterning and fabrication processes that have been proposed, along with their respective strengths and weaknesses and the potential advantages they may offer for magnetic recording. The increase in data density afforded by nanofabrication may have added significance as more conventional approaches to ever increasing density will encounter physical limitations set by the thermal stability of the recorded bits.

https://iopscience.iop.org/article/10.1088/0022-3727/38/12/R01/pdf

Nanofabricated and self-assembled magnetic structures as data storage media

Microcontact printing is a remarkable surface patterning technique. Developed about 10 years ago, it has triggered enormous interest from the surface science community, as well as from engineers and biologists. The last five years have been rich in improvements to the microcontact printing process itself, as well as in new technical innovations, many designed to suit new applications. In this review, we describe the evolution of microcontact printing over the past five years. The review is categorized into three main sections: the improvements made to the technique, new variations, and new applications.

Recent advances in microcontact printing

Microcontact printing (μCP) with elastomeric stamps is a versatile method to modify the chemistry of surfaces. We explore this patterning process here, examining the origin and character of its limits and demonstrating how best to use μCP and alkanethiols for lithography on gold at submicron scales. We find that, ultimately, this type of lithography is constrained by the need to carry the monolayer-forming reaction to completion, with significant degradation of the accuracy of prints at sub-500-nm scales due to molecular diffusion. Printing monolayers of eicosanethiol on gold proved to be the best practical compromise between self-assembly of the resist and its transport along the stamp and substrate interfaces as well as through the gas phase. Results for this system were particularly sensitive to the geometry of the stamp and how eicosanethiol was placed on, and transferred from, its surface to the gold. Our experiments, and simulations that corroborate them, show the relative importance of the various ...

Transport Mechanisms of Alkanethiols during Microcontact Printing on Gold

This paper demonstrates the use of microcontact printing (μCP) and capillary filling (CF) to pattern the deposition of iron oxides on a surface with feature sizes of microns. Selective wetting of both self-assembled monolayers (SAMs) of alkanethiolates on gold and alkylsiloxanes on Si/SiO2 formed by microcontact printing limited the deposition of the iron oxides to the hydrophilic areas on the surfaces; thereby, the chemical functionality of the hydrophilic SAM had only a minor influence on the wetting behavior and the deposition. The iron oxides were deposited either as magnetite particles from colloidal solution, by precipitation of the oxide from previously deposited drops of water containing an iron(III) salt, or by ferrite plating. The size of the metal oxide patterns was limited to the size of the areas that could be patterned using μCP. Capillary filling using a colloidal solution of magnetite could also be used to fabricate continuous, interconnected structures of magnetite. The magnetic properties of the deposited iron oxides were characterized by magnetic force measurement (MFM) and by measurement of the magnetization. The magnetite particles deposited in these experiments showed superparamagnetic behavior; they were too small individually to support a permanent magnetization.

Patterning with Magnetic Materials at the Micron Scale

Permalloy cylindrical submicron size dot arrays

The interfacial coupling between Gd(0001) and Fe(110) in an epitaxial Gd/Fe bilayer has been studied by means of magnetometry and polarized neutron reflectivity with spin analysis. The results are interpreted in terms of a Gd twisted spin state in low applied fields. This original magnetic configuration was examined by theoretical calculations and found to be due to competing Gd-Gd and Gd-Fe exchange interactions with the Gd-Fe exchange interactions being long ranged and oscillatory.

Corinne Miramond

Papers

Patterning with Magnetic Materials at the Micron Scale

Permalloy cylindrical submicron size dot arrays

Observation and interpretation of a partial Gd twisted spin state in an epitaxial Gd/Fe bilayer

Structure and magnetism of dysprosium/zirconium multilayers