11,286 research outputs found
Controlled open-cell two-dimensional liquid foam generation for micro- and nanoscale patterning of materials
Liquid foam consists of liquid film networks. The films can be thinned to the nanoscale via evaporation and have potential in bottom-up material structuring applications. However, their use has been limited due to their dynamic fluidity, complex topological changes, and physical characteristics of the closed system. Here, we present a simple and versatile microfluidic approach for controlling two-dimensional liquid foam, designing not only evaporative microholes for directed drainage to generate desired film networks without topological changes for the first time, but also microposts to pin the generated films at set positions. Patterning materials in liquid is achievable using the thin films as nanoscale molds, which has additional potential through repeatable patterning on a substrate and combination with a lithographic technique. By enabling direct-writable multi-integrated patterning of various heterogeneous materials in two-dimensional or three-dimensional networked nanostructures, this technique provides novel means of nanofabrication superior to both lithographic and bottom-up state-of-the-art techniques
Directing cell migration and organization via nanocrater-patterned cell-repellent interfaces.
Although adhesive interactions between cells and nanostructured interfaces have been studied extensively, there is a paucity of data on how nanostructured interfaces repel cells by directing cell migration and cell-colony organization. Here, by using multiphoton ablation lithography to pattern surfaces with nanoscale craters of various aspect ratios and pitches, we show that the surfaces altered the cells focal-adhesion size and distribution, thus affecting cell morphology, migration and ultimately localization. We also show that nanocrater pitch can disrupt the formation of mature focal adhesions to favour the migration of cells towards higher-pitched regions, which present increased planar area for the formation of stable focal adhesions. Moreover, by designing surfaces with variable pitch but constant nanocrater dimensions, we were able to create circular and striped cellular patterns. Our surface-patterning approach, which does not involve chemical treatments and can be applied to various materials, represents a simple method to control cell behaviour on surfaces
One-step deposition of nano-to-micron-scalable, high-quality digital image correlation patterns for high-strain in-situ multi-microscopy testing
Digital Image Correlation (DIC) is of vital importance in the field of
experimental mechanics, yet, producing suitable DIC patterns for demanding
in-situ mechanical tests remains challenging, especially for ultra-fine
patterns, despite the large number of patterning techniques in the literature.
Therefore, we propose a simple, flexible, one-step technique (only requiring a
conventional deposition machine) to obtain scalable, high-quality, robust DIC
patterns, suitable for a range of microscopic techniques, by deposition of a
low melting temperature solder alloy in so-called 'island growth' mode, without
elevating the substrate temperature. Proof of principle is shown by
(near-)room-temperature deposition of InSn patterns, yielding highly dense,
homogeneous DIC patterns over large areas with a feature size that can be tuned
from as small as 10nm to 2um and with control over the feature shape and
density by changing the deposition parameters. Pattern optimization, in terms
of feature size, density, and contrast, is demonstrated for imaging with atomic
force microscopy, scanning electron microscopy (SEM), optical microscopy and
profilometry. Moreover, the performance of the InSn DIC patterns and their
robustness to large deformations is validated in two challenging case studies
of in-situ micro-mechanical testing: (i) self-adaptive isogeometric digital
height correlation of optical surface height profiles of a coarse, bimodal InSn
pattern providing microscopic 3D deformation fields (illustrated for
delamination of aluminum interconnects on a polyimide substrate) and (ii) DIC
on SEM images of a much finer InSn pattern allowing quantification of high
strains near fracture locations (illustrated for rupture of a Fe foil). As
such, the high controllability, performance and scalability of the DIC patterns
offers a promising step towards more routine DIC-based in-situ micro-mechanical
testing.Comment: Accepted for publication in Strai
Improving the Resolution and Throughput of Achromatic Talbot Lithography
High-resolution patterning of periodic structures over large areas has
several applications in science and technology. One such method, based on the
long-known Talbot effect observed with diffraction gratings, is achromatic
Talbot lithography (ATL). This method offers many advantages over other
techniques, such as high resolution, large depth of focus, high throughput,
etc. Although the technique has been studied in the past, its limits have not
yet been explored. Increasing the efficiency and the resolution of the method
is essential and might enable many applications in science and technology. In
this work, we combine this technique with spatially coherent and
quasi-monochromatic light at extreme ultraviolet (EUV) wavelengths and explore
new mask design schemes in order to enhance its throughput and resolution. We
report on simulations of various mask designs in order to explore their
efficiency. Advanced and optimized nanofabrication techniques have to be
utilized to achieve high quality and efficient masks for ATL. Exposures using
coherent EUV radiation from the Swiss light source (SLS) have been performed,
pushing the resolution limits of the technique for dense hole or dot patterning
down to 40 nm pitch. In addition, through extensive simulations, alternative
mask designs with rings instead of holes are explored for the efficient
patterning of hole/dot arrays. We show that these rings exhibit similar aerial
images to hole arrays, while enabling higher efficiency and thereby increased
throughput for ATL exposures. The mask designs with rings show that they are
less prone to problems associated with pattern collapse during the
nanofabrication process and therefore are promising for achieving higher
resolution
- …