Photonic Crystals for Plasmonics: From Fundamentals to Superhydrophobic Devices

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A combined ElectroWetting on Dielectrics superhydrophobic platform based on silicon micro-structured pillars

A simple and ready to use approach for combining silicon superhydrophobic surfaces with ElectroWetting On Dielectrics (EWOD) phenomenon is presented. The substrate is fabricated using a two-phases process, where a first optical lithography step is used to define the position of the micro-pillars and a second one exploits the characteristics of reactive ion etch Bosch technique. The fabricated substrate has been then coupled with a micro-manipulator tip to show the local changes mechanism of contact angle by applying very low DC voltages in the range from 5 to 30 V. The device can be of interest for a wide variety of microfluidics applications related to the biomedical field

In situ X-ray scattering studies of protein solution droplets drying on micro- and nanopatterned superhydrophobic PMMA surfaces

Superhydrophobic poly(methyl methacrylate) surfaces with contact angles of ∼170° and high optical and X-ray transparencies have been fabricated through the use of optical lithography and plasma etching. The surfaces contain either a microscale pattern of micropillars or a random nanofibrillar pattern. Nanoscale asperities on top of the micropillars closely resemble Nelumbo nucifera lotus leaves. The evolution of the contact angle of water and lysozyme solution droplets during evaporation was studied on the micro- and nanopatterned surfaces, showing in particular contact-line pinning for the protein solution droplet on the nanopatterned surface. The microstructural evolution of lysozyme solution droplets was studied on both types of surfaces in situ under nearly contact-free conditions by synchrotron radiation microbeam wide-angle and small-angle X-ray scattering revealing the increasing protein concentration and the onset of precipitation. The solid residuals show hollow sphere morphologies. Rastermicrodiffraction of the detached residuals suggests about a 1/3 volume fraction of ≥17 nm lysozyme nanocrystalline domains and about a 2/3 short-range-order volume fraction. About 5-fold larger nanocrystalline domains were observed at the attachment points of the sphere to the substrates, which is attributed to particle growth in a shear flow. Such surfaces represent nearly contact-free sample supports for studies of inorganic and organic solution droplets, which find applications in biochips

Ultrahydrophobic PMMA micro- and nano-textured surfaces fabricated by optical lithography and plasma etching for X-ray diffraction studies

Polymeric (PMMA) ultrahydrophobic surfaces with contact angles up to about 170° have been fabricated and used in the context of synchrotron radiation experiments on biological droplets. The different microfabrication processes included either an optical lithography phase followed by a plasma texturing one or a single step deep reactive ion etch attack. The drying of several biological solution droplets has been monitored. Room temperature evaporation experiments (lysozyme, lactalbumin, cytochrome C, doxorubicin and synthesized peptides) finally result in the formation of easily detachable hollow residuals because of the low interaction between the ultrahydrophobic substrate and the aqueous droplet while pilot experiments (bovine insulin) in a sitting-drop environment bring to the formation of well defined crystals. Recent results about in situ X-ray diffraction experiments by SAXS & WAXS (Small and Wide Angle X-ray Scattering) μ-beam techniques confirm that the presence of such surfaces influences the formation of crystal or fibril structures. These substrates represent indeed a suitable support to study biological and inorganic droplets in a near contact-free environment exploiting the homogeneous evaporation rate induced by the ultrahydrophobicity of the system

Low Concentration Protein Detection Using Novel SERS Devices

We report, herein, novel processes of nanofabrication techniques for few molecules detection by generating surface plasmons, thus giving a giant electric field in a controllable and reproducible manner. Surface enhanced Raman scattering (SERS) measurements are performed for different proteins, namely, lysozyme, ribonuclease-B, bovin serum albumin, ferritin, and myoglobin in the temperature range between –65°C and 90°C, using “Device1”, which is fabricated by means of e-beam and electro-plating technique. The calculation shows the possible detection of myoglobin concentration down to attomole. The in-depth analysis even for small conformational changes is performed using 2D Raman correlation analysis and difference Raman analysis in order to gain straightforward understanding of proteins undergoing thermodynamical perturbation. “Device2” is fabricated by e-beam and metal electroless techniques to investigate the Rhodamine 6G (R6G) of different concentrations. Modifying this device by using bimetal (Ag and Au) electroless deposition permits us the further enhancement in Raman signal and better durability

Nano-patterned SERS substrate: application for protein analysis vs. temperature

We have illustrated the fabrication of nano-structures as a surface enhanced Raman scattering (SERS) substrate using electro-plating and electron-beam lithography techniques to obtain an array of gold nanograin-aggregate structures of diameter ranging between 80 and 100 nm with interstitial gap of 10-30 nm. The nanostructure based SERS substrate permits us to have better control and reproducibility on generation of plasmon polaritons. The calculation shows the possible detection of myoglobin concentration down to attomole. This SERS substrate is used to investigate the structural changes of different proteins; lysozyme, ribonuclease-B, bovin serum albumin and myoglobin in the temperature range between -65 and 90 degrees C. The in-depth analysis even for small conformational changes is performed using 2D Raman correlation analysis and difference Raman analysis in order to gain straightforward understanding of proteins undergoing thermodynamical perturbation

Silver-based surface enhanced Raman scattering (SERS) substrate fabrication using nanolithography and site selective electroless deposition

In this work active SERS (surface enhanced Raman scattering) substrates are obtained by electron beam lithography and site selective electroless deposition technique. The combination of these two techniques allows to obtain well-defined metal structures, with a considerable advantage in Raman signal enhancement and in device reproducibility. The active-substrates are composed of silver, gold or a combination of the two metals, with different nanoparticles characteristics, obtained by varying metal deposition time. Rhodamine 6G was used as probe molecules for SERS experiments, showing that this new active substrate has high sensitivity to SERS response and allows to give Raman scattering also for diluted solutions (10−20 M)

Superhydrophobic surfaces as smart platforms for the analysis of diluted biological solutions

The aim of this paper is to expound on the rational design, fabrication and development of superhydrophobic surfaces (SHSs) for the manipulation and analysis of diluted biological solutions. SHSs typically feature a periodic array or pattern of micropillars; here, those pillars were modified to incorporate on the head, at the smallest scales, silver nanoparticles aggregates. These metal nanoclusters guarantee superior optical properties and especially SERS (surface enhanced Raman scattering) effects, whereby a molecule, adsorbed on the surface, would reveal an increased spectroscopy signal. On account of their two scale-hybrid nature, these systems are capable of multiple functions which are (i) to concentrate a solution, (ii) to vehicle the analytes of interest to the active areas of the substrate and, therefore, (iii) to measure the analytes with exceptional sensitivity and very low detection limits. Forasmuch, combining different technologies, these devices would augment the performance of conventional SERS substrates and would offer the possibility of revealing a single molecule. In this work, similar SHSs were used to detect Rhodamine molecules in the fairly low atto molar range. The major application of this novel family of devices would be the early detection of tumors or other important pathologies, with incredible advances in medicine