Manipulation Of Nano-objects Research Articles

Real-Time In Situ Observation of CsPbBr3 Perovskite Nanoplatelets Transforming into Nanosheets.

The manipulation of nano-objects through heating is an effective strategy for inducing structural modifications and therefore changing the optoelectronic properties of semiconducting materials. Despite its potential, the underlying mechanism of the structural transformations remains elusive, largely due to the challenges associated with their in situ observations. To address these issues, we synthesize temperature-sensitive CsPbBr3 perovskite nanoplatelets and investigate their structural evolution at the nanoscale using in situ heating transmission electron microscopy. We observe the morphological changes that start from the self-assembly of the nanoplatelets into ribbons on a substrate. We identify several paths of merging nanoplates within ribbons that ultimately lead to the formation of nanosheets dispersed randomly on the substrate. These observations are supported by molecular dynamics simulations. We correlate the various paths for merging to the random orientation of the initial ribbons along with the ligand mobility (especially from the edges of the nanoplatelets). This leads to the preferential growth of individual nanosheets and the merging of neighboring ones. These processes enable the creation of structures with tunable emission, ranging from blue to green, all from a single material. Our real-time observations of the transformation of perovskite 2D nanocrystals reveal a route to achieve large-area nanosheets by controlling the initial orientation of the self-assembled objects with potential for large-scale applications.

Nanometer-Sized Te Pistons in Carbon Cylinders as Nano-Motor Prototypes: Implications for Nano-Electromechanical Device Fabrication

Manipulation of nano-objects is fascinating as it not only facilitates the understanding of the essential properties of nanomaterials but also enlightens the design of future nano-devices beyond current micro-electromechanical systems. In this paper, a piston-cylinder-configured nano-motor prototype is designed and fabricated, in which nanometer-sized Te segments are electrically controlled to reciprocate inside the carbon cylinder serving as nano-pistons. The nano-motor prototype has a length of ∼550 nm, an outer diameter of ∼150 nm, and a piston diameter of ∼30 nm. Electron-wind and thermal expansion are two reciprocal forces that create a dynamic equilibrium on the Te pistons and enable the circulating motions. With bias control, a circulating rate of 0–4.3 counts per second has been achieved. This prototype is the smallest piston-cylinder-type nano-motor that has ever been reported and can provide new insights into investment casting-assisted nano-electromechanical device fabrication.

Hydrodynamic manipulation of nano-objects by optically induced thermo-osmotic flows

Manipulation of nano-objects at the microscale is of great technological importance for constructing new functional materials, manipulating tiny amounts of fluids, reconfiguring sensor systems, or detecting tiny concentrations of analytes in medical screening. Here, we show that hydrodynamic boundary flows enable the trapping and manipulation of nano-objects near surfaces. We trigger thermo-osmotic flows by modulating the van der Waals and double layer interactions at a gold-liquid interface with optically generated local temperature fields. The hydrodynamic flows, attractive van der Waals and repulsive double layer forces acting on the suspended nanoparticles enable precise nanoparticle positioning and guidance. A rapid multiplexing of flow fields permits the parallel manipulation of many nano-objects and the generation of complex flow fields. Our findings have direct implications for the field of plasmonic nanotweezers and other thermo-plasmonic trapping systems, paving the way for nanoscopic manipulation with boundary flows.

Visualization of Optical Vortex Forces Acting on Au Nanoparticles Transported in Nanofluidic Channels.

The optical manipulation of nanoscale objects via structured light has attracted significant attention for its various applications, as well as for its fundamental physics. In such cases, the detailed behavior of nano-objects driven by optical forces must be precisely predicted and controlled, despite the thermal fluctuation of small particles in liquids. In this study, the optical forces of an optical vortex acting on gold nanoparticles (Au NPs) are visualized using dark-field microscopic observations in a nanofluidic channel with strictly suppressed forced convection. Manipulating Au NPs with an optical vortex allows the evaluation of the three optical force components, namely, gradient, scattering, and absorption forces, from the in-plane trajectory. We develop a Langevin dynamics simulation model coupled with Rayleigh scattering theory and compare the theoretical results with the experimental ones. Experimental results using Au NPs with diameters of 80–150 nm indicate that our experimental method can determine the radial trapping stiffness and tangential force with accuracies on the order of 0.1 fN/nm and 1 fN, respectively. Our experimental method will contribute to broadening not only applications of the optical-vortex manipulation of nano-objects, but also investigations of optical properties on unknown nanoscale materials via optical force analyses.

Optoelectronic Manipulation, Trapping, Splitting, and Merging of Water Droplets and Aqueous Biodroplets Based on the Bulk Photovoltaic Effect

Optical and optoelectronic techniques for micro- and nano-object manipulation are becoming essential tools in nano- and bio-technology. A remarkable optoelectronic technique that has experimented a strong development in the last few years is the so called photovoltaic optoelectronic tweezers. It is based on the light-induced electric fields generated by the bulk photovoltaic effect in certain ferroelectrics such as LiNbO3. The technique is simple and versatile, enabling a successful manipulation of a large variety of micro- and nano-objects with only optical control, without the need of electrodes or power supplies. However, it is still a challenge for this tool, to handle objects immersed in aqueous solution due to the electric screening effects of polar liquids. This has hindered their application in biotechnology and biomedicine where most processes develop in aqueous solution. In this work, a new efficient route to overcome this problem has been proposed and demonstrated. It uses photovoltaic optoelectronic tweezers to manipulate aqueous droplets, immersed in a non-polar oil liquid, but hanging at the interface air-oil. In this singular configuration, the high electric fields generated in the photovoltaic substrate allow a simple and flexible manipulation of aqueous droplets controlled by the light. Droplet guiding, trapping, merging and splitting have been achieved and efficient operation with water and a variety of bio-droplets (DNA, sperm, and PBS solutions) have been demonstrated. The reported results overcome a main limitation of these tweezers to handle bio-materials and promises a high potential for biotechnological and biochemistry applications including their implementation in optofluidic devices.

Proposed method for highly selective resonant optical manipulation using counter-propagating light waves

Abstract Optical manipulation using electronic resonance can realize the selective manipulation of nano objects exhibiting quantum mechanical properties by confining electronic systems based on the characteristics of individual objects. This study theoretically proposes a method to actualize selective manipulation based on the resonant optical response. In this method, counter-propagating light waves are used to extract the pure contribution of the resonant optical response in the exerted force by regulating the balance between the two light waves. Furthermore, the selection of nanoparticles with particular resonance levels at room temperature and quantum dots with a particular size in the cryogenic condition is numerically demonstrated. An especially interesting aspect of this method is that it enables the examination of the absorption spectrum of a single nanoparticle by mapping the absorption efficiency to its mechanical motion. The results reveal an unconventional link between optical force technology and nanomaterials science.

Long-distance optical pulling of nanoparticle in a low index cavity using a single plane wave.

Optical pulling force (OPF) can make a nanoparticle (NP) move against the propagation direction of the incident light. Long-distance optical pulling is highly desired for nano-object manipulation, but its realization remains challenging. We propose an NP-in-cavity structure that can be pulled by a single plane wave to travel long distances when the spherical cavity wrapping the NP has a refractive index lower than the medium. An electromagnetic multipole analysis shows that NPs made of many common materials can receive the OPF inside a lower index cavity. Using a silica-Au core-shell NP that is encapsulated by a plasmonic nanobubble, we experimentally demonstrate that a single laser can pull the Au NP-in-nanobubble structure for ~0.1 mm. These results may lead to practical applications that can use the optical pulling of NP, such as optically driven nanostructure assembly and nanoswimmers.

Scanning probe microscopy cantilevers improvement for advanced research and manipulation at nano scale.

Scanning probe microscopy (SPM) is a widely used method for the different kind of objects investigation. It allows to obtain information about the surface topography including its mechanical and electromagnetic characteristics at nano scale. SPM also could be used for manipulation of nanoobjects. The most popular and widely used SPM methods are atomic force (AFM) and magnetic force microscopy (MFM). Both of them based on measuring interaction between sample and cantilever (probe). Type of cantilever its curvature radius, coating, resonant frequency, hardness and other parameters significantly influence on the SPM images. Scientist constantly improving process of probes producing to fit the current demands. It is important to keep in mind that collected AFM data could contain not only direct information about the sample but also it might be a convolution of the sample and cantilever in case then the tip size comparable with the studied object. Convolution effect limits the AFM resolution [1]. Thus one of the most important task for researchers is to minimize this effect by reducing tip size both for AFM and MFM methods.

2D Manipulation of Nanoobjects by Perpendicular Electric Fields: Implications for Nanofabrication

The capability of controlling the motion of nanoobjects on a surface would open perspectives in nanofabrication. Here, we show the proof of concept that the displacement of a 2D nanostructure on a surface can be controlled by means of two perpendicular electric fields. With a specifically designed sample holder, we displace a 2D negative island on Si(001) along a close loop, in a low-energy electron microscope. Our technique could be applied to other systems to assemble nanomaterials.

Two-state switchable plasmonic tweezers for dynamic manipulation of nano-objects.

In this work, we present a plasmonic platform capable of trapping nano-objects in two different spatial configurations. The switch between the two trapping states, localized on the tip and on the outer wall of a vertical gold nanochannel, can be activated by varying the focusing position of the excitation laser along the main axis of the nanotube. We show that the switching of the trapping site is induced by changes in the distribution of the electromagnetic field and of the trapping force. The "inner" and "outer" trapping states are characterized by a static and a dynamic behavior respectively, and their stiffness is measured by analyzing the positions of the trapped specimens as a function of time. In addition, we demonstrate that the stiffness of the static state is high enough to trap particles with diameter as small as 40 nm. These results show a simple, controllable way to generate a switchable two-state trapping regime, which could be used as a model for the study of dynamic trapping or as a mechanism for the development of nanofluidic devices.

Single-cell biomagnifier for optical nanoscopes and nanotweezers

Optical microscopes and optical tweezers, which were invented to image and manipulate microscale objects, have revolutionized cellular and molecular biology. However, the optical resolution is hampered by the diffraction limit; thus, optical microscopes and optical tweezers cannot be directly used to image and manipulate nano-objects. The emerging plasmonic/photonic nanoscopes and nanotweezers can achieve nanometer resolution, but the high-index material structures will easily cause mechanical and photothermal damage to biospecimens. Here, we demonstrate subdiffraction-limit imaging and manipulation of nano-objects by a noninvasive device that was constructed by trapping a cell on a fiber tip. The trapped cell, acting as a biomagnifier, could magnify nanostructures with a resolution of 100 nm (λ/5.5) under white-light microscopy. The focus of the biomagnifier formed a nano-optical trap that allowed precise manipulation of an individual nanoparticle with a radius of 50 nm. This biomagnifier provides a high-precision tool for optical imaging, sensing, and assembly of bionanomaterials.

Nonlocal effect on resonant radiation force exerted on semiconductor coupled quantum well nanostructures**Project supported by the Natural Science Foundation of Guangdong Province, China (Grant Nos. 2016A030313439 and 2018A030313480), GDUPS (2017), the Key Program of the Natural Science Foundation of Guangdong Province, China (Grant No. 2017B030311003), and the Science and Technology Program of Guangzhou City, China (Grant No. 201707010403).

Based on the microscopic nonlocal optical response theory, the resonant radiation force exerted on a semiconductor-coupled quantum well nanostructure (CQWN), induced by the nonlocal interaction between lasers and electrons in conduction bands, is investigated for two different polarized states. The numerical results show that the spatial nonlocality of optical response can cause a radiation shift (blue-shift) for the spectrum of the resonant radiation force, which is dependent on the CQWN width ratio, the barrier height, and polarized states sensitively. It is also confirmed that the resonant radiation force is steerable by the incident and polarized directions of incident light. This work may provide an advantageous method for detecting internal quantum properties of nanostructures, and open novel and raising possibilities for optical manipulation of nano-objects using laser-induced radiation force.

Recent Achievements on Photovoltaic Optoelectronic Tweezers Based on Lithium Niobate

This review presents an up-dated summary of the fundamentals and applications of optoelectronic photovoltaic tweezers for trapping and manipulation of nano-objects on the surface of lithium niobate crystals. It extends the contents of previous reviews to cover new topics and developments which have emerged in recent years and are marking the trends for future research. Regarding the theoretical description of photovoltaic tweezers, detailed simulations of the electrophoretic and dielectrophoretic forces acting on different crystal configurations are discussed in relation to the structure of the obtained trapping patterns. As for the experimental work, we will pay attention to the manipulation and patterning of micro-and nanoparticles that has experimented an outstanding progress and relevant applications have been reported. An additional focus is now laid on recent work about micro-droplets, which is a central topic in microfluidics and optofluidics. New developments in biology and biomedicine also constitute a relevant part of the review. Finally, some topics partially related with photovoltaic tweezers and a discussion on future prospects and challenges are included.

Soft electrostatic trapping in nanofluidics

Trapping and manipulation of nano-objects in solution are of great interest and have emerged in a plethora of fields spanning from soft condensed matter to biophysics and medical diagnostics. We report on establishing a nanofluidic system for reliable and contact-free trapping as well as manipulation of charged nano-objects using elastic polydimethylsiloxane (PDMS)-based materials. This trapping principle is based on electrostatic repulsion between charged nanofluidic walls and confined charged objects, called geometry-induced electrostatic (GIE) trapping. With gold nanoparticles as probes, we study the performance of the devices by measuring the stiffness and potential depths of the implemented traps, and compare the results with numerical simulations. When trapping 100 nm particles, we observe potential depths of up to Q≅24 kBT that provide stable trapping for many days. Taking advantage of the soft material properties of PDMS, we actively tune the trapping strength and potential depth by elastically reducing the device channel height, which boosts the potential depth up to Q~200 kBT, providing practically permanent contact-free trapping. Due to a high-throughput and low-cost fabrication process, ease of use, and excellent trapping performance, our method provides a reliable platform for research and applications in study and manipulation of single nano-objects in fluids.

Photothermal Transport of DNA in Entropy-Landscape Plasmonic Waveguides.

The ability to handle single, free molecules in lab-on-a-chip systems is key to the development of advanced biotechnologies. Entropic confinement offers passive control of polymers in nanofluidic systems by locally asserting a molecule's number of available conformation states through structured landscapes. Separately, a range of plasmonic configurations have demonstrated active manipulation of nano-objects by harnessing concentrated electric fields. The integration of these two independent techniques promises a range of sophisticated and complementary functions to handle, for example, DNA, but numerous difficulties, in particular, conflicting requirements of channel size, have prevented progress. Here, we show that metallic V-groove waveguides, embedded in fluidic nanoslits, form entropic potentials that trap and guide DNA molecules over well-defined routes while simultaneously promoting photothermal transport of DNA through the losses of plasmonic modes. The propulsive forces, assisted by in-coupling to propagating channel plasmon polaritons, extend along the V-grooves with a directed motion up to ≈0.5 μm·mW-1 away from the input beam and λ-DNA velocities reaching ≈0.2 μm·s-1·mW-1. The entropic trapping enables the V-grooves to be flexibly loaded and unloaded with DNA by variation of transverse fluid flow, a process that is selective to biopolymers versus fixed-shape objects and also allows the technique to address the challenges of nanoscale interaction volumes. Our self-aligning, light-driven actuator provides a convenient platform to filter, route, and manipulate individual molecules and may be realized wholly by wafer-scale fabrication suitable for parallelized investigation.

New system for manipulation of nanoobjects based on composite Ti2NiCu/Pt nanotweezers with shape memory effect

We report the new system for manipulation of nanoobjects based on composite Ti2NiCu/Pt nanotweezers with shape memory effect. The design consists of the bimetallic Ti2NiCu/Pt shape memory nanotweezers placed on a tip of electrochemically etched tungsten needle. The semiconductor diode placed on the tip of the needle plays both role of resistive element of the heater and temperature sensor for feedback control loop closing. The device is compatible with existing positioning systems like OmniProbe®, Kleindiek®, etc. and may find numerous practical applications in various tasks of nanotechnology connected with 3D manipulation.

Device for nanoobject manipulation based on two-layer composite with shape memory

A device for gripping of microand nanoobjects (nanotweezers) with a working body made of bimetal composite (fast-quenched Ti2NiCu alloy with shape memory and platinum layer) is developed and studied. A method for manufacturing of the composite material using local ion etching and ion-stimulated deposition from gas phase is proposed. A structure of nanotweezers based on such a composite and experiments on gripping and displacement of submicron objects are presented.

Photon-induced generation and spatial control of extreme pressure at the nanoscale with a gold bowtie nano-antenna platform.

Precise spatial and temporal control of pressure stimulation at the nanometer scale is essential for the fabrication and manipulation of nano-objects, and for exploring single-molecule behaviour of matter under extreme conditions. However, state-of-the-art nano-mechanical transducers require sophisticated driving hardware and are currently limited to moderate pressure regimes. Here we report a gold plasmonic bowtie (AuBT) nano-antennas array that can generate extreme pressure stimulus of ∼100 GPa in the ps (10-12 s) time scale with sub-wavelength resolution upon irradiation with ultra-short laser pulses. Our method leverages the non-linear interaction of photons with water molecules to excite a nano-plasma in the plasmon-enhanced near-field and induce extreme thermodynamic states. The proposed method utilizes laser pulses, which in contrast to micro- and nano-mechanical actuators offers simplicity and versatility. We present time-resolved shadowgraphic imaging, electron microscopy and simulation data that suggest that our platform can efficiently create cavitation nano-bubbles and generate intense pressure in specific patterns, which can be controlled by the selective excitation of plasmon modes of distinct polarizations. This novel platform should enable probing non-invasively the mechanical response of cells and single-molecules at time and pressure regimes that are currently difficult to reach with other methods.

LiNbO3: A photovoltaic substrate for massive parallel manipulation and patterning of nano-objects

The application of evanescent photovoltaic (PV) fields, generated by visible illumination of Fe:LiNbO3 substrates, for parallel massive trapping and manipulation of micro- and nano-objects is critically reviewed. The technique has been often referred to as photovoltaic or photorefractive tweezers. The main advantage of the new method is that the involved electrophoretic and/or dielectrophoretic forces do not require any electrodes and large scale manipulation of nano-objects can be easily achieved using the patterning capabilities of light. The paper describes the experimental techniques for particle trapping and the main reported experimental results obtained with a variety of micro- and nano-particles (dielectric and conductive) and different illumination configurations (single beam, holographic geometry, and spatial light modulator projection). The report also pays attention to the physical basis of the method, namely, the coupling of the evanescent photorefractive fields to the dielectric response of the nano-particles. The role of a number of physical parameters such as the contrast and spatial periodicities of the illumination pattern or the particle deposition method is discussed. Moreover, the main properties of the obtained particle patterns in relation to potential applications are summarized, and first demonstrations reviewed. Finally, the PV method is discussed in comparison to other patterning strategies, such as those based on the pyroelectric response and the electric fields associated to domain poling of ferroelectric materials.

A template-assisted self-organization process for the formation of a linear arrangement of pairs of metallic tips

ABSTRACTA novel process for the formation of pairs of opposing metallic nanotips within linear trenches on a silicon wafer is investigated in detail. The process is based on a spreading knife technique typically used in nanosphere lithography to generate monolayers of colloidal polystyrene beads. Here it is applied to initiate self-assembly of spheres in long linear trenches acting as a template for the sphere arrangement. The optimum blade velocity to deposit the spheres selectively and densely packed in the trench depends on the trench surface fraction and can be described by a modified Dimitrov model. It is demonstrated that the spheres can be used as a shadow mask to deposit metallic nanotips in a channel, which are electrically interconnected on each side of the trench, possibly enabling the control and manipulation of nanoobjects in the channel.