Nanosystems For Applications Research Articles

Manipulating electrokinetic conductance of nanofluidic channel by varying inlet pH of solution

The electrokinetic conductivity of micro-/nanofluidic systems, which strongly depends on the local solution properties (e.g., pH and ionic strength), has wide applications in nanosystems to control the system performance and ion rectification. Accurate and active manipulation of this parameter is proven to be very challenging since, in nanoscale, the ion transport is particularly dominated by the acquired surface charge on the solid–liquid interfaces. In this study, we propose an approach to manipulate the nanochannel electrokinetic conductivity by changing the pH value of the solution at the inlet in order to impose asymmetrical conditions inside nanochannel. The variable surface charge of walls is determined by considering the chemical adsorption on the solid–liquid interface and the electrical double layer interaction. The presented numerical model, which couples Poisson–Nernst–Planck and Navier–Stokes equations, can fully consider the electro-chemo-mechanical transport phenomena and predict the electrokinetic conductivity of nanofluidic channels with good accuracy. Modeling results show that the electrokinetic conductivity of the nanofluidic systems can be regulated by varying the solution pH at the inlet. It is revealed that the stronger electric double layers interaction can enhance the sensitivity of the nanochannel electrokinetic conductance to the inlet pH. This unique behavior of the nanochannel electrokinetic conductivity could broaden potential applications in biomedical, energy, and environmental systems using nanofluidic devices.

Exogenous vitamin C boosts the antitumor efficacy of paclitaxel containing reduction-sensitive shell-sheddable micelles in vivo

Slow drug release at the tumor tissue and poor tumor penetration are two big challenges for the successful application of nanosystems in tumor therapy. Here, we report that a high concentration of the natural reducing agent vitamin C (VC) triggers rapid extracellular PTX release from PTX-loaded shell-sheddable PEG-SS-PCL micelles (SSM) in tumors in vivo. An in vivo tolerance study showed that VC at a blood concentration of 40mM had little toxicity to nude mice. Notably, SSM rapidly disassembled and released the payloads (Cy5 or PTX) in response to 40mM VC. In vivo near-infrared imaging of tumor-bearing mice showed that with post-injection of VC to establish a blood concentration of 40mM, Cy5 was quickly released from the micelles and diffused deep into the tumor tissue. Biodistribution studies revealed that 6h after the injection of PTX-loaded micelles the highest tumor accumulation was reached, which was set as the injection time for VC. The antitumor efficacy of a combination therapy of PTX-loaded micelles and VC was evaluated in both MCF-7 and U87MG tumor models. In both tumor models, single injections of VC didn't show any antitumor effect, while sequential administration of PTX-loaded SSM and VC exhibited significantly higher tumor inhibition effects and better survival rates as compared to single treatment with PTX-loaded micelles, demonstrating that exogenous administration of VC effectively triggered the release of PTX from SSM in vivo. The combination of reduction-sensitive nanomedicines with exogenous VC appears a promising approach to achieve potent treatment of malignant tumors.

The Mechanical and Electrical Properties of a Single Carbon Nanofiber Induced by Applying Tensile Strain.

Carbon nanofibers (CNFs) are good candidates for nano-system applications because they have the excellent mechanical and the electrical properties. The mechanical and electrical properties of a single CNF were measured. A tensile test and a measurement of the electrical resistance of CNFs during elongation were performed inside a scanning electron microscope. We confirmed that the CNFs used in this experiment consisted of a polycrystalline structure and an amorphous phase by a result of Raman. Additionally, we observed that the crystal structure in nanofibers exhibits brittle fracture behavior and the amorphous phase make them relatively ductile. The elastic moduli of the CNFs were 9.57 to 13.6 GPa in the elastic section. The electrical resistance of the CNFs exhibited unusual behavior during elongation. The electrical resistance of the CNFs exhibited stable resistance increase like as the tensile results in the initial region. But the electrical resistance exhibited generally irregular increase after initial region because of the polycrystalline structure and amorphous phase. The strain sensitivity of the CNFs exhibited a much lower value.

AlGaN/GaN HEMTs with very thin buffer on Si (111) for nanosystems applications

In the present work, AlGaN/GaN high electron mobility transistors (HEMTs) have been grown with very thin buffer layers on silicon substrates in view of developing nano electromechanical systems (NEMS) for sensors applications. To ensure transducer operation in the MHz range together with low mechanical stiffness, epitaxial structures with thickness below 1 μm have to be developed. We report on the evolution of the material and electrical properties of AlGaN/GaN HEMTs with thicknesses varying from 2 μm to 0.5 μm. The set of parameters obtained includes in-plane Young modulus of 250 GPa in association with carrier density of 6 × 1012 cm−2 and mobility above 1000 cm2 V−1 s−1. The resulting behavior of demonstration transistors validates these epilayers for electromechanical resonators operation.

Mechanical assessment of suspended ALD thin films by bulge and shaft-loading techniques

We assessed mechanical properties of free-standing atomic-layer-deposited (ALD) Al2O3 thin films, mixed oxide (AlxTiyOz) films and Al2O3/TiO2 nanolaminates (75 and 200nm). Using bulge and microelectromechanical system shaft-loading techniques, we evaluated the Young’s modulus, residual stress and ultimate tensile stress of these films and laminates. Fits to the load–displacement curves provided estimates for the residual stress and Young’s modulus. We extracted a residual stress of 347–403MPa for Al2O3, 365–389MPa for AlxTiyOz and 450–455MPa for the nanolaminate. The Young’s modulus was 164–165GPa for Al2O3, 151–154GPa for mixed oxide and 148–169GPa for the nanolaminate. Thin membranes exhibited an ultimate tensile strength of 1.57–2.56GPa for Al2O3, 1.17–2.09GPa for AlxTiyOz and 1.23–2.26GPa for the nanolaminate. The ability to make thin, yet mechanically strong, suspended membranes is useful in micro- and nanosystem applications ranging from thermally insulated devices to large stroke mechanical actuators.

Ball milling effect on structural and magnetic properties of Ni–Mn–Ga ferromagnetic nanoparticles

The off-stoichiometric Ni2MnGa ferromagnetic alloys are one of the active materials that are of great interest when they are ball milled into nanopowder. These powders are prospective materials for nanosystem applications. However, the properties of the nano-crystalline Ni–Mn–Ga alloys depend strongly on their structure and internal stress, which develop during the milling process. Ni–Mn–Ga nanoparticles were prepared by ball-milling method, and characterized by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) techniques. The powders are found to be a disordered mixture structure of austenite and martensite. We calculated that an average internal stress is 0.28 to 2.05 MPa stored in the distorted lattice due to milling. Reduction in particle sizes is accompanied by increase of the lattice strain level when the milling time increases. The VSM reveals that magnetic saturation and coercivity decrease with increase of the milling duration. This phenomenon causes deterioration in the hard magnetic properties.

Engineering of an Idealized WD Repeat as NanoBuilding Block for β‐propeller Protein Scaffolds

The great diversity in the structure and function of proteins has stimulated interest in using them for potential applications in nanosystems and nanodevices. This diversity has been further enhanced by protein engineering, which provides the capability to modify existing molecules or create entirely new ones. By using tandem repeated sequences that form the structural building blocks in a group of β‐propeller proteins; we have used a consensus design approach and structural considerations to engineer modular and relatively large scaffolds. An idealised WD repeat was designed from a structure‐based sequence alignment and considering a set of structural guidelines. Using a plasmid sequential ligation strategy, artificial concatemeric genes with up to 10 copies of idealised repeat were then constructed. Corresponding proteins with 4 through to 10 WD repeats were found to be soluble when over‐expressed in E. coli. The designed modular proteins obtained could be further evolved by random mutagenesis similarly to those proteins in nature which have arisen through events of gene duplication and fusion, followed by divergence of sequence repeats. The results show that the β‐propeller scaffold proves to be an attractive platform for future engineering work, particularly in experiments in which directed evolution techniques might improve the stability of the molecules and/or tailor them for a specific function.

Patterned L10-FePt for polarization of magnetic films

In various micro and nanosystems applications comprising magnetic films, the polarizing field still needs to be integrated. We hereby present a solution for the self biasing of magnetic films using micropatterned permanent magnets. Micromagnetic simulations were used as a designing and optimization tool to create a biasing structure. The samples were fabricated with varying geometric parameters using classical silicon microfabrication techniques. Nanostructured TbCo/FeCo magnetostrictive thin films were sputtered over coercive FePt filled trenches etched in silicon. Magnetic and magneto-elastic characterizations confirmed the numerical simulations. In particular, nonlinear actuation of a self-biased magnetostrictive cantilever has been obtained at a zero external polarizing field.

Editorial

It is a great pleasure to welcome you to Biointerface Research in Applied Chemistry, a new open access journal, which is dedicated to innovative, practically oriented original research on the fabrication, characterization, functionalization, and manipulation of biomaterials and nanomaterials, hybrid nanosized structures and nanocomposites, with a strong emphasis on the ecological and biomedical applications of nanosystems, new strategies for fighting antibiotic resistance and biofilms’ development in natural, medical and industrial environments, design of new synthetic compounds and the discovery of new natural bioactive compounds. The prime aim of Biointerface Research in Applied Chemistry is to publish first-class, original research articles under an open access policy with minimal fees for the authors. The quality of the published articles will be assured by a fast yet rigorous peer-review process. The editors will usually reject papers outside the scope of the journal with an immediate decision. Authors who wish to withdraw their manuscript (at any stage of the process) should contact the editorial board. Biointerface Research in Applied Chemistry is published as an online journal, distinguishing between different types of publications: reviews, which are expected to produce a coherent argument about a topic or a focused description of a field, full articles presented as comprehensive reports on original research of the highest quality and short communications, which should be concise, usually no longer than 2500 words and not intended to publish preliminary results, but an independent report representing a significant contribution to the field of interest. Short communications are also send to peer review. For reviews and full articles there will be no page restrictions in place. Our editorial policy inquires that all submitted papers should be complete in themselves and adequately supported by experimental details. We are looking forward to receiving some of your very best manuscripts for publication in Biointerface Research in Applied Chemistry and to participate to an increased international dissemination of scientific information in fully-searchable electronic formats.

Microstructural, mechanical and magnetic properties of shape memory alloy Ni 55Mn 23Ga 22 thin films deposited by radio-frequency magnetron sputtering

The near-stoichiometric Ni 2MnGa ferromagnetic alloys are one of the smart materials, that are of a great interest when they are deposited as a thin film by r.f. sputtering. These thin films of shape memory alloys are prospective materials for micro and nanosystem applications. However, the properties of the shape memory polycrystalline thin films depend strongly on their structure and internal stress, which develop during the sputtering process as well as during the post-deposition annealing treatment. In this study, about 1 μm Ni 55Mn 23Ga 22 thin films were deposited in the range 0,45 to 1,2 Pa of Ar pressure and P = 40 to 120 W. Their composition, crystallographic structure, internal stress and stress gradient, indentation modulus, hardness, deflection induced by magnetic field and magnetic properties were systematically studied as a function of the temperature of the silicon substrate ranging from 298 to 873 K and the vacuum annealing treatment at 873 K for 21,6 ks and 36 ks. A silicon wafer having a native amorphous thin SiO x buffer layer was used as a substrate. This substrate influences the microstructure of the films and blocks the diffusion process during the heat treatment. The crystal structure of the martensitic phase in each film was changed systematically from bct or 10 M or 14 M. In addition, the evolution of the mechanical properties such as mean stress, stress gradient, roughness, hardness and indentation modulus with the temperature (of substrate or of heat treatment) were measured and correlated to crystal structure and morphology changes. Moreover, it has been shown that it is necessary to associate a high temperature (873 K) annealing during a long time (21 ks and 36 ks) to obtain good ferromagnetic properties. Thus, for the well annealed films (36 ks at 873 K) the magnetostrain is about - 170 ppm for a magnetic field of 1 MA m - 1 applied along the beams. As a conclusion, the response of free-standing magnetic shape memory films to a magnetic field of 0,2 MA m - 1 depends strongly on the martensitic structure, internal mechanical stress (mean and gradient) and magnetic properties. The free-standing annealed film at 873 K for 36 ks points out a considerable magnetic actuation associated with bct or 10 M or 14 M martensitic structures.

Ion energy distribution near a plasma meniscus for multielement focused ion beams

The axial ion energy spread near a plasma meniscus for multielement focused ion beams is investigated experimentally in atomic and molecular gaseous plasmas of krypton, argon, and hydrogen by tailoring the magnetic field in the region. In the case of magnetic end plugging, the ion energy spread reduces by ∼50% near the meniscus as compared to the bulk plasma, thereby facilitating beam focusing. A quadrupole filter can be used to control the mean energy of the ions. Comparison with standard Maxwellian and Druyvesteyn distributions with the same mean energy indicates that the ion energy distribution in the meniscus is deficient in the population of low and high energy tail ions, resulting in a Gaussian-like profile with a spread of ∼4 and ∼5 eV for krypton and argon ions, respectively. By carefully tuning the wave power, plasma collisionality, and the magnetic field in the meniscus, the spread can be made lower than that of liquid metal ion sources, for extracting focused ion beams of other elements with adequate current density, for research and applications in nanosystems

Structural and Mechanical Characterizations of Ni-Mn-Ga Thin Films Deposited by R.F. Sputtering and Heat-Treated

The near-stoichiometric Ni2MnGa ferromagnetic alloys are one of these smart materials, that show a great interest when they are deposited as a thin film by rf sputtering. These thin films of shape memory alloys (SMAs) are prospective materials for micro and nanosystem applications. However, the properties of the SMAs polycrystalline thin films depend strongly on their structure and internal stress, which develop during the sputtering process and also during the post-deposition annealing treatment. In this study, 1μm Ni55Mn23Ga22 thin films were deposited at 0.45 and 1 Pa of Ar and their composition, crystallographic structure, internal stress, indentation modulus, hardness and deflection induced by magnetic field were systematically studied as a function of the temperature of the silicon substrate ranging from 298 to 873 K and the vacuum annealing treatment at 873 K for 21 and 36 ks. A silicon wafer having a native amorphous thin SiOx buffer layer was used as a substrate. This substrate influences the microstructure and blocks the diffusion process during the heat treatment. The crystal structure of the martensitic phase in each film was changed systematically from bct or 10M or 14M. In addition, the evolution of the mechanical properties such as means stress, roughness, hardness and indentation modulus with the temperature (of substrate or of heat treatment) were measured and correlated to crystal structure and morphology changes. It is concluded that the response of a free-standing magnetic SMAs films to a magnetic field of 200 kA/m depends strongly on the martensitic structure, internal mechanical stress (mean and gradient) and magnetic properties. The free-standing annealed film at 873 K for 36 ks demonstrates a considerable magnetic actuation associated with bct or 10M or 14M martensitic structures.

System approach to metrology of quantum multiparticle systems

Features of the metrology of quantum multiparticle systems in connection with general system theory and representational theory are considered. Quantitative characteristics of the periodic system of elements (PSE) are introduced and studied, including property correlation, and also system hierarchies are considered leading to its analysis and possible application of nanosystems and quantum computers.

Nanoparticles-chemistry, new synthetic approaches, gas phase clustering and novel applications

In this paper, an overview of the synthesis, chemistry and applications of nanosystems carried out in our laboratory is presented. The discussion is divided into four sections, namely (a) chemistry of nanoparticles, (b) development of new synthetic approaches, (c) gas phase clusters and (d) device structures and applications. In ‘chemistry of nanoparticles’ we describe a novel reaction between nanoparticles of Ag and Au with halocarbons. The reactions lead to the formation of various carbonaceous materials and metal halides. In ‘development of new synthetic approaches’ our one-pot methodologies for the synthesis of core-shell nanosystems of Au, Ag and Cu protected with TiO2 and ZrO2 as well as various polymers are discussed. Some results on the interaction of nanoparticles with biomolecules are also detailed in this section. The third section covers the formation of gas phase aggregates/clusters of thiol-protected sub-nanoparticles. Laser desorption of H2MoO4, H2WO4, MoS2, and WS2 giving novel clusters is discussed. The fourth section deals with the development of simple devices and technologies using nanomaterials described above.

DRY AND WET ETCHING WITH (111) SILICON FOR HIGH-PERFORMANCE MICRO AND NANO SYSTEMS

Etching with (111) silicon is relatively new, but it represents very exciting opportunities in micro and nano system applications. By combining wet and dry anisotropic etching, high-precision, actuatable micro and nano structures can be fabricated in single-crystalline silicon. This paper reviews several relevant (111) microfabrication results reported in the literature. Among these, a single-mask process that we call sacrificial bulk micromachining (SBM) is reviewed in detail. Various electrical isolation methods as well as a number of applications to micro and nano systems are presented.