Manipulation Of Nanowires Research Articles

Ion‐beam‐assisted fabrication and manipulation of metallic nanowires

Metallic nanowires (NWs) are the key performers for future micro/nanodevices. The controlled manoeuvring and integration of such nanoscale entities are essential requirements. Presented is a discussion of a fabrication approach that combines chemical etching and ion beam milling to fabricate metallic NWs. The shape modification of the metallic NWs using ion beam irradiation (bending towards the ion beam side) is investigated. The bending effect of the NWs is observed to be instantaneous and permanent. The ion beam-assisted shape manoeuvre of the metallic structures is studied in the light of ion-induced vacancy formation and reconfiguration of the damaged layers. The manipulation method can be used for fabricating structures of desired shapes and aligning structures at a large scale. The controlled bending method of the metallic NWs also provides an understanding of the strain formation process in nanoscale metals.

Dynamics of ferromagnetic nanowires in a rotating magnetic field

Manipulating nanowires with external magnetic fields has emerged as a powerful tool in various engineering applications, which prompts an urgent need to better understand the dynamics of nanowire rotation under different control conditions. In this article, the motion of ferromagnetic nickel (Ni) nanowires under a rotating magnetic field was investigated both theoretically and experimentally. The synchronous and asynchronous rotations were characterized in detail. Analytical models were developed for the major modes of motion by solving the governing equations of rotation. Particularly, a selection of theoretical formula for fluid viscous torque on nanowires of large aspect ratios was made based on the computational fluid dynamics simulation results. The comparisons of the theoretical prediction and the experimental data showed very good agreement. The effects of various system variables, such as the strength and rotating frequency of the magnetic field and the nanowire aspect ratio, were examined. Hence, the insights gained from this work can be applied to future exploration of magnetic manipulation of nanowires.

Wall effects on the electrical manipulation of metal nanowires.

The rotation induced by AC electric fields on metal nanowires has been studied theoretically and experimentally. In the experiments, the nanowires rotate close to the bottom of the device. The present work studies the effects of the wall on the electrorotation and electro-orientation of a metal nanowire numerically. The induced electrical rotation of a metal nanowire in solution is originated by both the electrical torque on the induced dipole and the induced charge EOF around the particle. The theoretical analysis presented here only considers the effects of the wall on the nanowire rotation originated by the torque on the induced dipole. Two methods are employed in the analysis in order to obtain the electrical and viscous torques acting on the nanowire: (i) the 3D electrical and hydrodynamic equations are simulated using the finite element method and (ii) hydrodynamic and electrical slender-body approximations are used to obtain, respectively, line distributions of Stokeslets and charge that take into account the proximity of a plane wall. The numerical results obtained from the two methods are totally in agreement. The main wall effects are that the electrical torque is reduced, the viscous torque is increased, and an electric repulsive force from the wall appears.

Motion Control, Planning and Manipulation of Nanowires Under Electric-Fields in Fluid Suspension

Automated manipulation of nanowires and nanotubes would enable the scalable manufacturing of nanodevices for a variety of applications, including nanoelectronics and biological applications. In this paper, we present an electric-field-based method for motion control, planning, and manipulation of nanowires in liquid suspension with a simple, generic set of electrodes. We first present a dynamic model and a vision-based motion control of the nanowire motion in dilute suspension with a set of $N\times N$ controllable electrodes. Since the motion planning of a nanowire from one position to the target location is NP-hard, two heuristic algorithms are presented to generate near-optimal motion trajectories. We compare the heuristic motion planning algorithms with other existing algorithms such as the rapidly exploring random tree (RRT) and $A^{\ast}$ algorithms. The comparisons show that the proposed heuristic algorithms obtain near-optimal minimum time trajectories. Finally, we demonstrate a single, integrated process to position, orient, and deposit multiple nanowires onto the substrate. Extensive experimental and numerical results are presented to confirm the motion control and planning algorithms.

Single nanowire manipulation within dielectrophoretic force fields in the sub-crossover frequency regime.

This paper presents the quantitative relationship between the control parameters of a dielectrophoretic (DEP) force field and the resulting electrokinetic region of influence experienced by individual nanowires (NWs) in colloidal suspensions. Our results show that DEP operation at sub-crossover frequencies, which are defined as frequencies slightly below the transition from positive-to-negative DEP, offers a suitable but previously unexplored performance regime for single NW manipulation and assembly. The low-magnitude DEP forces at these frequencies, which are estimated to be 8 orders of magnitude smaller as compared to near-DC frequencies, provide an efficient avenue to controllably extend electrokinetic influence on suspension volumes that present isolated NWs. These results are demonstrated using α-phase manganese dioxide NWs as a model one-dimensional construct. Based on experimentally extracted values for the NW intrinsic conductivity and dielectric permittivity, we employ computational models to explain each of the performance regimes observed in this nanoassembly system. In addition, we use a new approach to estimate the concentration of a NW suspension from experimentally observed data for deposition yields.

Set-up for an optically induced dielectrophoresis platform and its application to micro- and nanoscale material manipulation

In this study, we set-up an optically induced dielectrophoresis platform, which can be used to manipulate micro- and nanoscale particles. A commercially available liquid-crystal-display–based projector was used as a light source to produce a variety of optical patterns and project them onto a photoconductive material. The optical patterns illuminating the photoconductive material can be used as configurable virtual electrodes, which will induce dielectrophoretic forces on particles. Thus, the particles can be manipulated by dynamic optical patterns. Manipulation of silver nanowires was demonstrated using this platform by forming a specific pattern of nanowires through illumination of the photoconductive chip with an optical pattern. In addition, polystyrene beads with diameters of 10 and 20 μm were also successfully manipulated using this system. By combining the optically induced dielectrophoretic force and the hydrodynamic force, particles of two different sizes can be continuously separated into two different microchannels. Furthermore, the microparticles were collected and concentrated by virtual electrode traps. We believe that this flexible platform can be applied to investigations of a variety of fields.

Effect of size on fracture and tensile manipulation of gold nanowires

The fracture of metallic nanowires has attracted much attention owing to its reliability of application in nanoelectromechanical system. In this paper, we studied the fracture of [100] single-crystal gold nanowire subjected to uniaxial tension. The statistical breaking position distributions showed that the size effects had dominated the deformation and fracture of nanowires, and the quasi-static tensile deformations are insensitive to the styles of tensile rates. Furthermore, it was observed that the small-sized nanowire broke in the middle with disordered crystalline structure; for the middle-sized nanowire, although slippage plane had maintained the lattice degree, the fracture also happened in the middle due to symmetric tension; for the large-sized nanowire, the slippage was destroyed by symmetric tension, which induced the broken neck at one end of the nanowire. When the nanowire width is less than 5a (“a” means lattice constant, 0.408 nm for gold), the mechanical strength is relatively strong with obvious uncertainty, which can be attributed to the surface atom effect; when the width is larger than 5a, the influence of size on the mechanical property is more obvious at the constant strain rate than that at the absolute rate. Finally, the mechanical strength of the nanowire decreases with the size increasing.

Design and implementation of shape memory alloy-actuated nanotweezers for nanoassembly

Reliable and accurate tools for nanoscale manipulation are constantly sought to complement new breakthroughs in nanomaterials and nanotechnology. In this study, a new design of electrically actuated nanotweezers was developed for manipulation of individual nanowires. The design featured two chemically etched tungsten tips attached to a carbon fiber-reinforced polymer and two shape memory alloy actuators. The shape recovery effect of the spring actuators was exploited as a control mechanism for the bending and relaxation modes of the nanotweezers. This was activated by driving a potential difference of less than 1 V across the coils, which was considerably lower than for electromechanical micro/nanotweezers previously developed. To demonstrate the pick-and-place capability of the system, experiments were implemented inside the vacuum chamber of a JEOL-JSM 6300 SEM. Individual Au nanowires averaging 5–10 µm in length and 200 nm in diameter were assembled on silicon substrates using the tungsten tips to draw initials out of various nanowire shapes such as curls, loops, crosses, and zigzags. With such capability, the nanotweezers may find applications in the manufacturing of complex nanostructures or modification of surface properties of materials.

Single CdS nanowire photodetector fabricated by FIB

In this paper, a photodetector based on single cadmium sulfide (CdS) nanowire was fabricated using focused ion beam (FIB) technique. The nanowire manipulation, transferring and electrode fabrication process by the FIB and its influence on the photodetector performance were studied. CdS nanowire was synthesized by Vapor–Phase–Transport (VPT) method. CdS powder was thermally evaporated at 950°C in the Argon (Ar) gas as the source material. High Resolution Transmission Electron Microscope (HRTEM) and X-ray Diffraction (XRD) experiment results showed that the nanowire presented wurtzite CdS structure and good crystal quality. The photoresponse time and recovery time of the photodetector were 150ms and 53ms, respectively. The photosensitivity was 2.83, and the low sensitivity was caused by the deposition of Ga on the surface of the nanowire and electrode gap during the FIB fabricating process.

Manipulation and assembly of ZnO nanowires with single holographic optical tweezers system

ZnO nanowires, characterized with high melting points, are hard to assemble together with laser fusion. In order to build micro-nano structures with ZnO nanowires, a polymer film with a low melting point and high optical transparency is introduced as a substrate for ZnO nanowires to be deposited. A holographic optical tweezers system is used not only to manipulate ZnO nanowires, but also to melt the polymer film for the fixation of ZnO nanowires. By this method, micro-nano structures composed of ZnO nanowires are produced, which can be utilized as subwavelength optical waveguides.

Manipulation of ZnO nanowires using a tapered fiber probe

Manipulating ZnO nanowires with high precision and flexibility is of great importance for fabrication of semiconductor-based optoelectronic devices. Here, we report the manipulation of ZnO nanowires using a tapered fiber probe. With a light of 980 nm launched into the probe, ZnO nanowires were trapped and manipulated by the probe through optical forces. Migration and alignment were also realized. Experiments were interpreted by numerical simulations.

Fast, effective manipulation of nanowires for electronic devices

Fast, effective manipulation of nanowires for electronic devices

Optical Vortex Induced Rotation of Silver Nanowires

Optical manipulation of metal nanowires offers the possibility to control the position, orientation, and associated motions of individual nanowires, particularly by utilizing their plasmonic properties. Here, we demonstrate that the orbital angular momentum of photons in Laguerre–Gauss (optical vortex) beams can induce rotation of single silver (Ag) nanowires with lengths of over 10 μm that are lying on (in molecular proximity to) a dielectric surface. We show that the rotation dynamics are governed by plasmonic interactions of the Ag nanowires with linearly polarized light, which yield a sinusoidal optical torque that causes angular acceleration. These results provide important information to understand the angular dependence of plasmonic nanowire–light interactions and extend the repertoire to realize applications in plasmonic lab-on-a-chip systems.

Thermally Induced Shape Modification of Free-standing Nanostructures for Advanced Functionalities

Shape manipulation of nanowires is highly desirable in the construction of nanostructures, in producing free-standing interconnect bridges and as a building block of more complex functional structures. By introducing asymmetry in growth parameters, which may result in compositional or microstructural non-uniformity in the nanowires, thermal annealing can be used to induce shape modification of free-standing nanowires. We demonstrate that such manipulation is readily achieved using vertically grown Pt-Ga-C composite nanowires fabricated by focused-ion-beam induced chemical vapor deposition. Even and controllable bending of the nanowires has been observed after a rapid thermal annealing in a N2 atmosphere. The mechanisms of the shape modification have been examined. This approach has been used to form electrical contacts to freestanding nano-objects as well as nano-‘cages' for the purpose of securing ZnO tubs. These results suggest that thermally induced bending of nanowires may have potential applications in constructing three-dimensional nanodevices or complex structures for the immobilization of particles and large molecules.

Directed transport and location-designated rotation of nanowires using ac electric fields

The motion control of individual nanowires is essential for effective nanowire manipulation strategies. In this paper, we demonstrate a simple and general method to dynamically control the motion of a chemically untreated nanowire in a quadrupole electrode structure. The motion of single nanowires was determined by positive dielectrophoresis and orientational torque, which were induced by optionally exerting ac signals onto specific electrodes for regulating the electric field distribution in real time. A silver nanowire was guided to transform postures and transport directionally in a working regime of about 115 μm × 115 μm. The selected nanowire was then transported to a region of weak gradients and forced to rotate at the designated location subsequently. The behavior of the nanowires, including their posture, cornering time, linear displacement and location-designated rotation, was dynamically monitored and regulated. A simple analytical model was developed to derive the driving forces and torques on the nanowire.

Rapid, One‐Step, Digital Selective Growth of ZnO Nanowires on 3D Structures Using Laser Induced Hydrothermal Growth

AbstractFor functional nanowire based electronics fabrication, conventionally, combination of complex multiple steps, such as (1) chemical vapor deposition (CVD) growth of nanowire, (2) harvesting of nanowire, (3) manipulation and placement of individual nanowires, and (4) integration of nanowire to circuit are necessary. Each step is very time consuming, expensive, and environmentally unfriendly, and only a very low yield is achieved through the multiple steps. As an alternative to conventional complex multistep approach, original findings are presented on the first demonstration of rapid, one step, digital selective growth of nanowires directly on 3D micro/nanostructures by developing a novel approach; laser induced hydrothermal growth (LIHG) without any complex integration of series of multiple process steps such as using any conventional photolithography process or CVD. The LIHG process can grow nanowires by scanning a focused laser beam as a local heat source in a fully digital manner to grow nanowires on arbitrary patterns and even on the non‐flat, 3D micro/nano structures in a safer liquid environment, as opposed to a gas environment. The LIHG process can greatly reduce the processing lead time and simplify the nanowire‐based nanofabrication process by removing multiple steps for growth, harvest, manipulation/placement, and integration of the nanowires. LIHG process can grow nanowire directly on 3D micro/nano structures, which will be extremely challenging even for the conventional nanowire integration processes. LIHG does not need a vacuum environment to grow nanowires but can be performed in a solution environment which is safer and cheaper. LIHG can also be used for flexible substrates such as temperature‐sensitive polymers due to the low processing temperature. Most of all, the LIHG process is a digital process that does not require conventional vacuum deposition or a photolithography mask.

Photoconductive study and carrier dynamics of vertically aligned GaAs nanowires

Single wire devices are generally fabricated to study the electrical and photoelectric behaviors of semiconductor nanowires (NWs); however detriment or contamination can hardly be avoided during manipulation of NWs under focused ion and electron beams. This could not be a trivial factor for III-V NWs which are candidates for high efficiency solar energy harvesting and sensitive photodetection. In this study an alternative way to probe the photoconductive property of individual epitaxial GaAs NWs is presented. For the sample preparation, a uniform spin-coated layer of polymer was selected to be the supporting medium for the vertically aligned NWs structure; then the adequate thinning and polishing of the sample exposed the NW tip and also achieved the required height of NW. An external power adjustable laser was introduced as the excitation source, and the dark and photoconductive current-voltage properties of individual NW were measured by the conductive atomic force microscopy. The typical Schottky style photoconductive behavior was observed in the vertically aligned GaAs NW, and its photoresponsivity has been found to be much higher than that of the reported for single NW photodetector. Finally, a numerical model based on the experimental setup was established to simulate the photoelectric behavior of individual NW. The minority hole lifetime has been found to dominate the photoconductive current-voltage properties of NW under the positive sample bias, and can be derived from the quantitative fitting of experimental photo-IV curves.

Repositioning technique in nanowire manipulation by oscillating gripper

In this study, a manipulation device is developed that is able to pick up and reposition a nanomaterial. In the device, the gripper, composed of two silicon microcantilevers, is actuated by XYZ stages on a rotational stage and has eight degrees of freedom. One of the microcantilevers can be vibrated at a resonant frequency by an acoustic oscillator mounted on the gripper base. We successfully picked up a copper (II) oxide NW grown on a substrate and then repositioned the NW. During the picking-up process, the NW was statically bent to break at the root by the gripper motion, or cyclically bent using the acoustic oscillator to induce a fatigue fracture. During the repositioning process, natural adhesion between the NW and the gripping surface often presented a challenge when removing the NW. This difficulty was overcome by vibrating the gripping surface, which resulted in the reduction of the adhesion effects. The mechanism of the reduction of the adhesion effects is discussed concerning the relationship between the adhesion energy and the peeling force acting on the NW. Another technique of repositioning using an inertia force generated by the oscillator is also discussed.

7AM2-C-1 ダイナミック光渦による金属ナノワイヤーの3次元操作(7AM2-C マニピュレーションとパイオデバイス)

Recently practical micro/nano devices using nanomaterials such as nanoparticles and nanowires have been developed in various fields including nanophotonics and nanoelectronics. Manipulation of nanowires is indispensable for constructing the microdevices. Here we propose and experimentally demonstrate a novel method of three-dimensional optical manipulation of a metallic nanowire using an optical vortex. In our method, a metallic nanowire can be grasped by optical repulsive force and simultaneously rotated by total angular momentum of an optical vortex. In addition, the posture of a metallic nanowire can be horizontally or vertically fixed in any direction by high-speed switching of the helical phase shift of an optical vortex. The aligned nanowire can be translated to the desired position by moving the stage supporting a sample.

Manipulating ZnO nanowires for field-effect device integration by optical-fiber grip coated with thermoplastic copolymer

We report a novel method to precisely manipulate nanowires in air, using a tapered optical fiber tip and thermoplastic ethylene–vinyl acetate copolymer. For an application of such nanowire manipulation, we attempted to fabricate logic circuits with two ZnO nanowires aligned in series and parallel, choosing ∼50 μm-long ZnO nanowires for field-effect transistors and load resistors.