Set Of Nanostructures Research Articles

Dispersion-engineered metasurfaces reaching broadband 90% relative diffraction efficiency

Dispersion results from the variation of index of refraction as well as electric field confinement in sub-wavelength structures. It usually results in efficiency decrease in metasurface components leading to troublesome scattering into unwanted directions. In this letter, by dispersion engineering, we report a set of eight nanostructures whose dispersion properties are nearly identical to each other while being capable of providing 0 to 2π full-phase coverage. Our nanostructure set enables broadband and polarization-insensitive metasurface components reaching 90% relative diffraction efficiency (normalized to the power of transmitted light) from 450 nm to 700 nm in wavelength. Relative diffraction efficiency is important at a system level – in addition to diffraction efficiency (normalized to the power of incident light) – as it considers only the transmitted optical power that can affect the signal to noise ratio. We first illustrate our design principle by a chromatic dispersion-engineered metasurface grating, then show that other metasurface components such as chromatic metalenses can also be implemented by the same set of nanostructures with significantly improved relative diffraction efficiency.

Effect of cell-nanostructured substrate interactions on the capture efficiency of HeLa cells

Circulating tumor cells (CTCs) are regarded as an effective biomarker for cancer detection, diagnosis and prognosis monitoring. CTCs capture based on nanostructured substrates is a powerful technique. Some specific adhesion molecule antibody coated on the surface of nanostructured substrates, such as EpCAM, is commonly used to enhance the CTCs capture efficiency. Substrate nanotopographies regulate the interaction between the substrates and captured cells, further influencing cell capture efficiency. However, the relationship between cell capture efficiency and cell–substrate interaction remains poorly understood. Here, we explored the relationship between cell capture efficiency and cell–substrate interaction based on two sets of nanostructures with different nanotopographies without antibody conjugation. Given the urgent demand for improving the capture efficiency of EpCAM-negative cells, we used HeLa (EpCAM-negative) cells as the main targets. We demonstrated that HeLa cells could be more effectively captured by two nanostructural substrates, especially by double-layer composite nanoforests. Therefore, the morphological and migrating interaction between HeLa cells and distinct substrates was associated with cell capture efficiency. Our findings demonstrated the potential mechanism for optimizing the nanotopography for higher capture efficiency, and provide a potential foundation for cancer detection, diagnosis and treatment.

Stepwise nanosphere lithography: an alternate way of fabricating nanostructures

This work demonstrates a new nanosphere lithography technique, termed stepwise nanosphere lithography, to create matrices of novel two- and three-dimensional nanostructures. Different sets of nanostructures are placed at desired locations through step-by-step deposition during thermal evaporation onto a substrate surface. Three deposition parameters: (1) number of deposition steps; (2) angle of deposition; and (3) nanosphere mask orientation angle were investigated. By changing these parameters, the ordering, shape, and size of nanostructures were modified accordingly. Two- and three-dimensional nanostructure matrices with different arrangements and symmetries were successfully simulated and fabricated experimentally through a combination of multiple stationary deposition stages with different parameters.

Nuclear microprobe performance in high-current proton beam mode for micro-PIXE

The performance of a nuclear microprobe is dominantly determined by the brightness of the injected ion beam. At Jožef Stefan Institute (JSI), negative hydrogen ion beams are created in a multicusp ion source and injected into a 2MV tandetron accelerator. The output characteristics of the multicusp ion source were tuned in order to obtain matching proton beam intensities for the ion accelerator and for the object slits as well. For the optimal focusing of the proton beam in a high-current mode (I>100pA) to the sub-micrometer dimensions, dedicated thin nanostructures with sharp edges have been manufactured. Set of nanostructures was micromachined by focused ion beam (FIB) at film reference material, produced by Institute for Reference Materials and Measurements (IRMM) and constituted of 57μg/cm2 of titanium on vitreous carbon substrate. The proton beam profiles were measured by beam scans across the nanostructures over long measuring times, indicating eventual slow drifts of the sample from a reference beam direction. Overall, proton beam dimensions of 600nm were obtained, demonstrating appropriate stability for micro-PIXE (micro-Particle Induced X-ray Emission) at sub-micrometer resolution for elemental analysis of biological tissue samples prepared in a freeze-dried state or in a frozen-hydrated state. The resulting performance required for micro-PIXE analysis in a high current mode with a 3MeV proton beam is presented.

High-throughput drawing and testing of metallic glass nanostructures.

Thermoplastic embossing of metallic glasses promises direct imprinting of metal nanostructures using templates. However, embossing high-aspect-ratio nanostructures faces unworkable flow resistance due to friction and non-wetting conditions at the template interface. Herein, we show that these inherent challenges of embossing can be reversed by thermoplastic drawing using templates. The flow resistance not only remains independent of wetting but also decreases with increasing feature aspect-ratio. Arrays of assembled nanotips, nanowires, and nanotubes with aspect-ratios exceeding 1000 can be produced through controlled elongation and fracture of metallic glass structures. In contrast to embossing, the drawing approach generates two sets of nanostructures upon final fracture; one set remains anchored to the metallic glass substrate while the second set is assembled on the template. This method can be readily adapted for high-throughput fabrication and testing of nanoscale tensile specimens, enabling rapid screening of size-effects in mechanical behavior.

Fabrication Of 3D Nanostructured Multielectrode Arrays By Using Thermal Nanoimprint Lithography To Improve Cell Coupling For Low Signaling Neurons

Event Abstract Back to Event Fabrication Of 3D Nanostructured Multielectrode Arrays By Using Thermal Nanoimprint Lithography To Improve Cell Coupling For Low Signaling Neurons Dominique Decker1*, Sven Ingebrandt1, Holger Rabe1, Karl-Herbert Schäfer1 and Monika Saumer1 1 University of Applied Sciences Kaiserslautern, Department of Informatics and Microsystems Technologie, Germany Motivation Recently a lot of effort was done in optimizing MEA technology in order to enhance signal qualities and to improve the coupling with cells in a culture. Recording performances can be improved by either coating the MEA with artificial or biological polymers or by adding three dimensional nanostructures on top of the sensing pad, thus increasing the surface area and ensuring a tight cell electrode coupling by partly engulfing the nanosized MEA features by the cells [1, 2]. Here we present a fabrication process of nanostructured MEA chips based on nanoimprint lithography (NIL) and electroplating. Compared to other nanostructuring techniques, NIL offers the possibility to fabricate a whole set of nanostructures on several chips at the same time in a fast, simple and inexpensive full wafer process. The nanostructured MEA devices will later be used for action potential measurements and drug testing with neurons with relative weak signals, such as those from the enteric nervous system. Materials and Methods Silicon or glass wafers are vapor-deposited with 20 nm titanium and 200 nm gold layers, followed by a 200 nm thin spin-coated layer of a thermal resist. Nanoimprint lithography is performed (figure 1) with a customized silicon master stamp including a broad range of nanostructures with different geometries, diameters and arrangements. After removing the residual layer with reactive ion etching the nanostructures are filled with gold by electroplating. Microfabrication techniques including photolithography, wet chemical etching and chemical vapor deposition steps are needed to define the leads, the sensing areas and the contact pads of the MEA chips. Subsequently the wafer is cut. The separated chips are bonded to a PCB, encapsulated and prepared for cell culture experiments. Results and Discussion Different nanostructures like meanders, lines, pillars and tubes with diameters from 50 nm up to 800 nm, different heights up to 500 nm and variable distances between the structures have successfully been fabricated on gold-coated substrates. By means of overelectroplating it is also possible to create mushroom-like or muffin-like structures. AFM and SEM pictures show a good structure transfer during NIL and a high uniformity of the electroplated nanostructures over the whole wafer (figure 2). Electrochemical characterization of the fabricated structures is done with cyclic voltammetry and electrochemical impedance spectroscopy. As expected the measurements show an increase of the electrochemical active surface area and a reduction of the impedance compared to planar electrodes. First biocompatibility tests with P19 cells also show a good cell electrode coupling. Conclusion The presented fabrication process incorporates an alternative, high throughput, time saving and thus cost-efficient method for the integration of nanostructures on MEA chips. Different nanostructures are investigated to find an ideal combination of shape, dimension and arrangement for enhancing the signal-to-noise ratio. Future work will be based on recordings with living cells where we intend to work with neurons from the enteric nervous system. These experiments will explore which nanostructures are best suited for cell electrode coupling and thus signal detection from this particular cell type.

Cell adhesion and migration on nanopatterned substrates and their effects on cell-capture yield

With scanning electron microscopy analysis, we investigated the role of nanoscale topography on cellular activities; e.g. cell adhesion and spreading by culturing A549 cells (human lung carcinoma cell line cells) for 1–48 h on three sets of nanostructures; quartz nanopillars (QNPs), silicon nanopillars and silicon nanowire (SiNW) arrays, along with planar glass substrates. We found that cells on QNP arrays developed a longer shape than those on SiNW arrays. In addition, we studied how cell morphologies influence the cell-capture yield on the three sets of nanostructures. This research showed that the filopodial formations were directing the cell-capture yield on nanostructured substrates. This finding implies the possibility of using nanoscale topography features to control the filopodial formation including extension and migration from the cells. Using streptavidin-functionalized SiNW substrate, we further demonstrated a substantially higher yield (∼91.8 ± 5.9%) than the planar glass wafers (∼24.1 ± 7.5%) in the range of 200–3000 cells.

Organic Materials Science

AbstractThe following article is based on the presentation given by George M. Whitesides, recipient of the 2000 MRS Von Hippel Award, the Materials Research Society's highest honor, at the 2000 MRS Fall Meeting in Boston on November 29, 2000. Whitesides was cited for “bringing fundamental concepts of organic chemistry and biology into materials science and engineering, through his pioneering research on surface modification, self-assembly, and soft lithography.” The article focuses on the growing role of organic chemistry in materials science. Historically, that role has been to provide organic polymers for use in structures, films, fibers, coatings, and so on. Organic chemistry is now emerging as a crucial part of three new areas in materials science. First, it provides materials with complex functionality. Second, it is the bridge between materials science and biology/medicine. Building an interface between biological systems and electronic or optical systems requires close attention to the molecular level of that interface. Third, organic chemistry provides a sophisticated synthetic entry into nanomaterials. Organic molecules are, in fact, exquisitely fabricated nanostructures, assembled with precision on the level of individual atoms. Colloids are a related set of nanostructures, and organic chemistry contributes importantly to their preparation as well.