Helical Nanosprings Research Articles

Microstructure and Magnetic Properties of CoFe Nanowires and Helical Nanosprings

Magnetic nanosprings have applications in various fields, e.g., in sensors, actuators, and biomedical applications. However, it is difficult to synthesize them due to their complicated structure. Here, we report the synthesis of CoFe nanosprings by electrodeposition using vanadium oxide ions and ascorbic acid. The nanosprings have a helical structure and exist in the form of the Co53Fe47 alloy. Hysteresis curves of CoFe nanowire and nanospring arrays show soft ferromagnetic characteristics. The CoFe nanowires have shape anisotropy with an easy axis parallel to the array direction, whereas the CoFe nanosprings exhibit an isotropic behavior.

Estimation of anisotropic properties of nano-structured arrays by modal vibration control at microscale

ABSTRACTNano-structured arrays are engineered to meet the requirements of a variety of applications such as microfilters, sensors, and structural interface due to their unique mechanical characteristics, which cannot be achieved by conventional solid materials. However, it is hard to evaluate the elastic properties of nano-structured arrays owing to the discrete structure, sample size, and availability of suitable techniques. To facilitate this, we develop an advanced three-dimensional microscale vibration testing process. In the test, a specially designed three-dimensional microspecimen with tuned mass is excited by a piezoelectric actuator, and the resonance frequencies are detected by a laser device successfully. The anisotropic elastic moduli of nano-structured array composed of helical nano-springs are identified from a single spectrum. This array shows so strong characteristic anisotropy that the solid one hardly can attain. The microscale testing technique can be extended to other materials and microstructures.

The vibration of nanosprings affected by van der Waals interactions.

The vibration of tightly helical nanosprings affected by van der Waals (vdW) interactions is investigated based on continuum modelling. Explicit solutions are derived to clarify the influence of initial pitch, stiffness and the number of nanosprings on the period, frequency and amplitude of the vibration. Unlike classic linear/nonlinear springs, the waveform of the vibration is always asymmetric for tightly helical nanosprings due to the asymmetry of vdW attraction and repulsion. The at most three equilibrium positions for the nanosprings strongly depend on the deformation due to competition between the vdW interactions and the elastic energy of the nanosprings. This study provides physical insights into the origin of the novel dynamic properties of such nanosprings.

Anisotropic Elastic Properties of Chiral Sculptured Thin Films at Micro-Scale Evaluated by Resonance Frequency Spectra

Chiral sculptured thin films (STFs) Glancing-angle deposition (GLAD) thin films are nanoengineered to meet the requirements of a variety of applications such as micro filters, sensors, and waveguides due to their unique frequency characteristics which cannot be achieved by conventional solid materials. For the design, it is necessary to understand the elastic properties of STFs. To facilitate this, we report on our newly developed advanced micro-scale vibration testing process. In the testing, specially designed micro-specimens with surface areas of tens by tens of microns are excited using a piezoelectric (PZT) actuator and the resonance frequencies are detected by a laser device in the vertical or lateral directions successfully. The anisotropy elastic modulus of STFs composed of helical nanosprings are identified on the basis of vibration testing. The thin film shows strong characteristic anisotropy that the solid one hardly can attain. The micro-scale testing technique can be extended to other materials and microstructures.

Does Hooke's law work in helical nanosprings?

Hooke's law is a principle of physics that states that the force needed to extend a spring by some distance is proportional to that distance. The law is always valid for an initial portion of the elastic range for nearly all helical macrosprings. Here we report the sharp nonlinear force-displacement relation of tightly wound helical carbon nanotubes at even small displacement via a molecular mechanics model. We demonstrate that the van der Waals (vdW) interaction between the intertube walls dominates the nonlinear relation based on our analytical expressions. This study provides physical insights into the origin of huge nonlinearity of the helical nanosprings.

Anisotropic elastic properties of chiral sculptured thin films at micro-scale evaluated by resonance frequency spectra

Abstract Chiral sculptured thin films (STFs) are nano-engineered to meet the requirements of a variety of applications such as micro filters, sensors, and waveguides due to their unique frequency characteristics which cannot be achieved by conventional solid materials. For the design, it is necessary to understand the elastic properties of STFs. To facilitate this, we developed an advanced micro-scale vibration testing process. In the testing, specially designed micro-specimens with surface areas of tens by tens of microns are excited using a piezoelectric (PZT) actuator and the resonance frequencies are detected by a laser device in the vertical or lateral directions successfully. The anisotropy elastic modulus of STFs composed of helical nano-springs are identified on the basis of vibration testing. The thin film shows strong characteristic anisotropy that the solid one hardly can attain. The micro-scale testing technique can be extended to other materials and microstructures.

Elastic properties of array films at submicron-scale evaluated by resonance frequency spectra

Submicron array films are nano-engineered to meet the requirements of a variety of applications such as micro filters, sensors, and waveguides due to their unique frequency characteristics which cannot be achieved by conventional solid materials. For the design, it is necessary to understand the elastic properties of submicron array films. To facilitate this, we developed an advanced micro-scale vibration testing process. In the testing, specially designed micro-specimens with surface areas of tens by tens of microns are excited using a piezoelectric (PZT) actuator and the resonance frequencies are detected by a laser device in the vertical or lateral directions successfully. The elastic modulus of submicron array films composed of helical nano-springs are identified on the basis of vibration testing.

The Interesting Influence of Nanosprings on the Viscoelasticity of Elastomeric Polymer Materials: Simulation and Experiment

AbstractAmong all carbon nanostructured materials, helical nanosprings or nanocoils have attracted particular interest as a result of their special mechanical behavior. Here, carbon nanosprings are used to adjust the viscoelasticity and reduce the resulting hysteresis loss (HL) of elastomeric polymer materials. Two types of nanospring‐filled elastomer composites are constructed as follows: system I is obtained by directly blending polymer chains with nanosprings; system II is composed of the self‐assembly of a tri‐block structure such as chain‐nanospring‐chain. Coarse‐grained molecular dynamics simulations show that the incorporation of nanosprings can improve the mechanical strength of the elastomer matrix through nanoreinforcement and considerably decrease the hysteresis loss. This finding is significant for reducing fuel consumption and improving fuel efficiency in the automobile tire industry. Furthermore, it is revealed that the spring constant of nanosprings and the interfacial chemical coupling between chains and nanosprings both play crucial roles in adjusting the viscoelasticity of elastomers. It is inferred that elastomer/carbon nanostructured materials with good flexibility and reversible mechanical response (carbon nanosprings, nanocoils, nanorings, and thin graphene sheets) have both excellent mechanical and low HL properties; this may open a new avenue for fabrication of high performance automobile tires and facilitate the large‐scale industrial application of these materials.

M2-4 らせん型ナノ要素配列薄膜の変形と破壊(M2 材料評価)

M2-4 らせん型ナノ要素配列薄膜の変形と破壊(M2 材料評価)

Disappearance of stress singularity at interface edge due to nanostructured thin film

The purpose of this study is to examine the stress distribution near the interface between a nanostructured thin film and a solid body. We focus on a nanostructured thin film that consists of Ta 2O 5 helical nanosprings fabricated on a Si substrate by dynamic oblique deposition. The mechanical properties of the thin film are obtained by vertical and lateral loading tests using a diamond tip built into an atomic force microscope. The apparent shear and Young’s moduli, G′ and E′, of the thin film are 2–3 orders of magnitude lower than those of a conventional solid Ta 2O 5 film. Moreover, the thin film shows strong anisotropy. A finite element analysis for two types of components with different interface edges between the thin film and an elastic solid body is conducted under uniform displacement. One has a free edge where the surface-interface angle is 90°–90°, and the other has a short interface crack. These analyses indicate the absence of not only stress singularity but also high stress concentration near the free edge and the interface crack tip. The characteristic stress distributions near the interface are due to the nanoscopically discrete structure of the thin film.

535 ナノ構造薄膜/均質体界面端近傍における応力分布解析(OS7-1 微視構造を有する材料の変形と破壊,OS7 微視構造を有する材料の変形と破壊)

The purpose of this study is to examine the stress distribution near the interface edge between a nanostructured thin film and a solid body. A nanostructured thin film consists of Ta_2O_5 helical nanosprings is fabricated by dynamic oblique deposition. The mechanical properties of the thin film are obtained by vertical and lateral loading tests using a diamond tip built into an atomic force microscope. A finite element analysis for a component, which has the free edge of the interface between the thin film and an elastic solid body, is conducted under uniform displacement. The analysis indicates the absence of not only stress singularity but also high stress concentration near the free edge. The characteristic stress distribution near the interface is due to the nanoscopically discrete structure of the thin film.

Anisotropic deformation of thin films comprised of helical nanosprings

We investigate the mechanical anisotropy of thin films that consist of tantalum oxide (Ta 2O 5) helical nanosprings fabricated by dynamic oblique deposition. Not only the vertical but also the lateral stiffness of thin films is evaluated using specimens in which nanosprings are sandwiched between solid Ta 2O 5 layers. Lateral or vertical force is applied to the upper solid layer by a diamond tip built into an AFM. In particular, the lateral stiffness of a nanospring has never been reported before. Apparent shear and Young’s moduli, G′ and E′, of the thin films are 2–3 orders smaller than those of solid Ta 2O 5 film. Ratio E′/ G′ of the two different nanosprings is 3.4 and 6.2, and about 2.5 for the solid film. The thin films show strong characteristic anisotropy that the solid one could hardly attain. The stiffness and its anisotropy strongly depend on nanospring shape.

Preparation of Silica Nanosprings Using Cationic Gelators as Template

Abstract Cationic cyclo(dipeptide) gelators 10mimClO4, 11mimClO4, and 11pyClO4 were synthesized as templates for the sol–gel transcription reaction of alkoxysilanes. They were able to cause physical opaque gels in alcohols such as methanol, ethanol, and 1-propanol. Three-dimensional fibrous networks responsible for physical gelation were found in SEM images of gels. Sol–gel transcription reactions using the self-assemblies of three gelators as the templates were carried out in the presence of propylamine as a catalyst. When tetraethoxysilane (TEOS) was selected as a precursor, three kinds of morphologies, such as inner-helical nanotubes, right-handed nanobundles, and right-handed helical nanosprings were observed by electron microscopy. The helical nanosprings were preferentially formed as compared with nanotubes and nanobundles. On the other hand, the sol–gel polymerization of bis(triethoxysilyl)methane, 1,2-bis(triethoxysilyl)ethane, and 1,4-bis(triethoxysilyl)benzene as precursors gave nanoballs instead of tubular structures. When tetrabutylammonium fluoride (TBAF) was used as a catalyst, a helical tubular structure coated by silica nanoballs was identified.

Mechanical properties of nanosprings.

Nanostructures (nanotubes, nanowires, etc.) have been the object of intense theoretical and experimental investigations in recent years. Among these structures, helical nanosprings or nanocoils have attracted particular interest due to their special mechanical properties. In this work, we investigated structural properties of nanosprings in the Kirchhoff rod model. We derived expressions that can be used experimentally to obtain nanospring Young's modulus and Poisson's ratio values. Our results also might explain why the presence of catalytic particles is so important in nanostructure growth.

Synthesis, Characterization, and Manipulation of Helical SiO2 Nanosprings

Amorphous helical SiO2 nanosprings (80 to 140 nm in diameter and up to 8 microns long) were synthesized with a chemical vapor deposition technique, characterized and manipulated by scanning (SEM) and transmission (TEM) electron microscopy and atomic force microscopy (AFM). The helical nanosprings were observed in the middle of a straight nanowire and were formed by a perturbation during the growth of the straight nanowire. Contraction and expansion of the helical nanosprings were observed under in situ electron beam heating during TEM, as well as bending induced by an AFM tip, suggesting that the helical nanosprings are highly flexible and may have potential applications in nanomechanical, nanoelectronmagnetic devices, and composite materials.