Atomic Force Microscope Manipulation Research Articles

AFM Manipulation of EGaIn Microdroplets to Generate Controlled, On-Demand Contacts on Molecular Self-Assembled Monolayers.

Liquid metal droplets, such as eutectic gallium-indium (EGaIn), are important in many research areas, such as soft electronics, catalysis, and energy storage. Droplet contact on solid surfaces is typically achieved without control over the applied force and without optimizing the wetting properties in different environments (e.g., in air or liquid), resulting in poorly defined contact areas. In this work, we demonstrate the direct manipulation of EGaIn microdroplets using an atomic force microscope (AFM) to generate repeated, on-demand making and breaking of contact on self-assembled monolayers (SAMs) of alkanethiols. The nanoscale positional control and feedback loop in an AFM allow us to control the contact force at the nanonewton level and, consequently, tune the droplet contact areas at the micrometer length scale in both air and ethanol. When submerged in ethanol, the droplets are highly nonwetting, resulting in hysteresis-free contact forces and minimal adhesion; as a result, we are able to create reproducible geometric contact areas of 0.8-4.5 μm2 with the alkanethiolate SAMs in ethanol. In contrast, there is a larger hysteresis in the contact forces and larger adhesion for the same EGaIn droplet in air, which reduced the control over the contact area (4-12 μm2). We demonstrate the usefulness of the technique and of the gained insights in EGaIn contact mechanics by making well-defined molecular tunneling junctions based on alkanethiolate SAMs with small geometric contact areas of between 4 and 12 μm2 in air, 1 to 2 orders of magnitude smaller than previously achieved.

Applications of atomic force microscope manipulator operating in hybrid mode

The topography images by atomic force microscope (AFM) operating in a new hybrid mode with nanometre scale noise are obtained. Using the improved feedback of the AFM hybrid mode, the possibility of the manipulations of the microdrops by microscope tip is shown. Additionally, we introduce a method of an extra gentle movement of nanowires by liquid flow organized by the AFM tip.

Atomic force microscope manipulation of Ag atom on the Si(111) surface

We present first-principles total-energy electronic-structure calculations that provide the microscopic mechanism of the Ag atom diffusion between the half unit cells (HUCs) on the Si(111)-(7x7) surface with and without the tip of the atomic force microscope (AFM). We find that, without the presence of the AFM tip, the diffusions between the two HUCs are almost symmetric with the energy barrier of about 1 eV in the both directions. The diffusion is a two-step process with an intermediate metastable configuration in which the Ag atom is at the boundary of the HUCs. With the presence of the tip, we find that the reaction pathways are essentially the same, but the energy barrier in one direction is substantially reduced to be 0.2 - 0.4 eV by the tip, while that of the diffusion in the reverse direction remains larger than 1 eV. The Si tip reduces the energy barrier more than the Pt tip due to the flexibility of the tip apex structure. In addition to the reduction of the barrier, the tip traps the diffusing adatom preventing the diffusion in the reverse direction. Also we find that the shape of the tip apex structure is important for the trapping ability of the adatom. When the tip apex structure is blunt, the adatom interacts with the tip atom other than the tip apex atom. The bond formation between the AFM tip atom and the surface adatom is essential for the atom manipulation using the AFM tip. Our results show that the atom manipulation is possible with both the metallic and semiconducting AFM tips.

Nanoscale rippling on polymer surfaces induced by AFM manipulation.

Nanoscale rippling induced by an atomic force microscope (AFM) tip can be observed after performing one or many scans over the same area on a range of materials, namely ionic salts, metals, and semiconductors. However, it is for the case of polymer films that this phenomenon has been widely explored and studied. Due to the possibility of varying and controlling various parameters, this phenomenon has recently gained a great interest for some technological applications. The advent of AFM cantilevers with integrated heaters has promoted further advances in the field. An alternative method to heating up the tip is based on solvent-assisted viscoplastic deformations, where the ripples develop upon the application of a relatively low force to a solvent-rich film. An ensemble of AFM-based procedures can thus produce nanoripples on polymeric surfaces quickly, efficiently, and with an unprecedented order and control. However, even if nanorippling has been observed in various distinct modes and many theoretical models have been since proposed, a full understanding of this phenomenon is still far from being achieved. This review aims at summarizing the current state of the art in the perspective of achieving control over the rippling process on polymers at a nanoscale level.

Mechanical properties of suspended individual carbon nanotube studied by atomic force microscope

This paper is a short review on the mechanical properties of individual carbon nanotubes (CNTs), which were studied by atomic force microscope (AFM). AFM force–distance measurements were applied to three different nano structures based on the suspended CNTs, those are a straight suspended CNT, a coiled CNT, and a torsional CNT. Force–distance measurements were done on the pick and valley position of the coiled CNT and the estimated elastic moduli was compared with the straight one. Nanoscale metal plate was fabricated on the middle part of the suspended CNT structure using conventional lithography and etching procedure. The torsional modulus of the suspended CNT was estimated from the force–distance measurement using AFM manipulation on top of the metal plate. The paper covers synthesis and preparation method of various suspended CNT structure and the analysis of the force–distance measurements appropriate to each CNT structure. Prospects of the AFM force–distance measurements on emergent nano scale materials as well as CNT are suggested in the end of this paper.

Investigation of shear force of a single adhesion cell using a self-sensitive cantilever and fluorescence microscopy

In this paper, we describe a measurement system based on an atomic force microscope (AFM) for the measurement of the shear force and detachment energy of a single adhesion cell on a substrate. The shear force was quantitatively measured from the deflection of a self-sensitive cantilever that was employed for the simple configuration of the AFM manipulator. The shear force behavior of a single cell detaching from the substrate was observed. By staining cells with a fluorescence dye, the deformation shape of the cell being pushed with the cantilever could be clearly observed. The shear force and detachment energy of the cell increased with the size of the cell. The difference in the shear force of single cells on different substrates with different surface energies was quantitatively evaluated. The loading force applied to a single cell increased with the feed speed of the cantilever. The viability of cells after measurement under different feed speeds of the cantilever was also evaluated.

Complementary Microscopy Platform for Investigations of Hybrid Nanostructures Comprising Quantum Dots and Plasmonic Particles

ABSTRACTNanoscale systems combining colloidal quantum dots with plasmonic antennas will pioneer the development of novel nanodevices with tailored optical features for a wide range of applications. The interactions between such nanoparticles strongly depend on the particular distance. We propose the use of an atomic force microscope (AFM) to image and to position quantum dots with respect to plasmonic particles. Additionally, we analyze the arrangements with several optical characterization methods, such as confocal microscopy, fluorescence microscopy and superresolution optical fluctuation imaging (SOFI). These methods support each other and improve the AFM manipulation technique. The AFM tip is perfectly aligned to a focused laser by detecting the Raman signal of the silicon tip. Thus ultimately, we can simultaneously use the topography information with a spatial resolution in the range of the nanoparticle sizes and cross-correlate it with the optical characterization methods.

THEORETICAL STUDY OF THE EFFECT OF PROBE SHAPE ON ADHESION FORCE BETWEEN PROBE AND SUBSTRATE IN ATOMIC FORCE MICROSCOPE EXPERIMENT

Abstract The quantitative description of adhesion force dependence on the probe shape is of importance in many scientific and industrial fields. We performed a theoretical study on the influences of the probe shape (the sphere and parabolic probe) on the adhesion force at different humidity in order to elucidate how the adhesion force varied with the probe shape in atomic force microscope manipulation experiment. We found that the combined action of the triple point and the Kelvin radius is the guiding trend of the adhesion force, and these two fundamental parameters are closely related to the probe shape. Meanwhile, the theoretical results demonstrated that the adhesion force are in a good agreement with the experiment data if the van der Waals force is take into account.

A compact nano manipulator based on an atomic force microscope coupling with a scanning electron microscope or an inverted optical microscope

In this paper, we describe a novel nano manipulator based on an atomic force microscope (AFM). The body of the manipulator is enough compact to be operated inside the sample chamber of a scanning electron microscope (SEM). In order to realize the compact body, we employed a self-detection type cantilever for AFM observation. The cantilever includes strain resistance element, which can easily detect a deflection signal of the cantilever without other sensing devices such as optical lever systems. It is possible to observe the manipulation situation in the real time observation by using the SEM. The AFM manipulator is coupled with a haptic device for human interface. Thus, by using this system, the operator can move the AFM probe at any position on the surface with feeling the interaction force detected by the cantilever on the sample surface according to the cantilever deflection. As a performance of the system, biological samples were controllably manipulated under the SEM observation. Furthermore, in order to deal with biological samples in liquid condition, the manipulator can be coupled with an inverted optical microscope. By using the system, we successfully demonstrated manipulation of biological samples in liquid condition. Two AFM manipulators could be used for dissection of biological samples like a knife and fork.

Atomic force microscope manipulation of multiwalled and single walled carbon nanotubes with reflux and ultrasonic treatments

We are reporting the atomic force microscope (AFM) nanomanipulation of ultrasonically dispersed and reflux-oxidized multiwalled carbon nanotubes (MWCNT) and single walled carbon nanotubes (SWCNT) by con- trolling the AFM tip with a NanoManipulator on a silicon substrate. The structure and the morphology of the carbon nanotubes (CNT) were confirmed with AFM interfaced with NanoManipulator and transmission electron micro- scope. The modifying parameter, which controls the force exerted by AFM tip, was set to be 0.5 nA in each case (0.5 nA = 20 nN). Bending was observed in ultrasonically dispersed MWCNTs, whereas, cutting was observed for reflux-oxidized MWCNTs along with the lateral move- ments. Similar observations were found for SWCNTs with sharp cuts and lateral displacements. The results show that CNTs deform by combining bending and distortion when subjected to large mechanical forces exerted by the tip of the AFM. The magnitude of the force, required to deform the reflux-oxidized CNTs is less than that for the ultra- sonically dispersed CNTs, for both MWCNTs and SWCNTs.

Nonlinear displacement of ventral stress fibers under externally applied lateral force by an atomic force microscope

Actin-based stress fibers (SFs) have fundamental importance in the maintenance of mechanical stability of living cells. Several in vitro measurements of their elastic properties have therefore been made, but direct mechanical manipulation of individual SFs in vivo for the determination of their mechanical properties has not been attempted. No less important is a search for the possible formation of a global mechanical network involving SFs and other intracellular filamentous components. In this article, we present an application of atomic force microscopy to probe into a live cell and laterally push selected SFs in a fibroblast cells (VNOf 06 fibroblast-like cells derived from rat vomeronasal tissue) transfected with a green fluorescent protein-β-actin gene. The transfected cells were transferred to a serum-depleted medium before the atomic force microscope manipulation. The lateral displacement of the SFs under a point loading condition recorded on a fluorescence microscope revealed both linear and nonlinear displacements against the contour distance from the point of force loading. The nonlinear displacements of the SFs were attributed to their association with a cortical actomyosin-cell membrane complex that effectively pulled them back as a 2D thin plate.

Controlled AFM manipulation of small nanoparticles and assembly of hybridnanostructures

We demonstrate controlled manipulation of semiconductor and metallic nanoparticles(NPs) with 5–15 nm diameters and assemble these NPs into hybrid structures. Themanipulation is accomplished under ambient environment using a commercial atomic forcemicroscope (AFM). There are particular difficulties associated with manipulating NPs thissmall. In addition to spatial drift, the shape of an asymmetric AFM tip has to be takeninto account in order to understand the intended and actual manipulation results.Furthermore, small NPs often attach to the tip via electrostatic interaction and modify theeffective tip shape. We suggest a method for detaching the NPs by performing apseudo-manipulation step. Finally, we show by example the ability to assemble these smallNPs into prototypical hybrid nanostructures with well-defined composition and geometry.

In Situ Chemical Functionalization of a Single Carbon Nanotube Functionalized AFM Tip using a Correlated Optical and Atomic Force Microscope

ABSTRACTWe present a method for performing nanoscale wet chemistry on single carbon nanotubes as well as spectroscopic characterization of the functionalized molecules using a coupled atomic force microscope (AFM) and optical microscope. An AFM probe was functionalized with a single multiwalled carbon nanotube and then locally oxidized by dipping it into nitric acid (HNO3) in situ using AFM manipulation. Raman scattering was collected from the carbon nanotube functionalized probe before and after the oxidation reaction. An increase in the Raman D band was observed after the acid treatment, demonstrating that oxidation had occurred. This is the first step towards developing a real-time technique for dynamic studies of chemical reactions on single nanoparticles/molecules.

AFM tip characterization by Kelvin probe force microscopy

Reliable determination of the surface potential with spatial resolution is key for understanding complex interfaces that range from nanostructured surfaces to molecular systems to biological membranes. In this context, Kelvin probe force microscopy (KPFM) has become the atomic force microscope (AFM) method of choice for mapping the local electrostatic surface potential as it changes laterally due to variations in the surface work function or surface charge distribution. For reliable KPFM measurements, the influence of the tip on the measured electrostatic surface potential has to be understood. We show here that the mean Kelvin voltage can be used for a straightforward characterization of the electrostatic signature of neutral, charged and polar tips, the starting point for quantitative measurements and for tip-charge control for AFM manipulation experiments. This is proven on thin MgO(001) islands supported on Ag(001) and is supported by theoretical modeling, which shows that single ions or dipoles at the tip apex dominate the mean Kelvin voltage.

A study on AFM manipulation of single-wall carbon nanotube

As single-wall carbon nanotube (SWCNT) has special electrical and physical property, it can be used as excellent material to construct various nano electronic device. However, in the fabrication process, the modification of size, shape and even the electronic property, especially to the metallic SWCNT, is a key problem to be overcome. Here a modified nanomanipulation technology based on atomic force microscope (AFM) is utilized to perform various kinds of SWCNT manipulation, such as SWCNT separation, catalyst remove, continual nano buckles fabrication and even stretch to break, thus to modify the size, shape and eventually the electrical property of the SWCNT. In addition, the manipulation results are analyzed based on the mechanical mechanism.

Measurement of the Mechanical Stability of Semiconductor Line Structures in Relevant Media

Enhanced particle removal processes in wet cleaning of semiconductor wafers can cause significant lateral forces on surface structures. These forces have to be limited to below the stability of the (nano) structures on the surface to prevent damage. A mechanical fracture test based on atomic force microscope manipulation was used in liquid media (deionized water, isopropanol, and propylene carbonate) to measure the lateral stability of polysilicon line structures. The results are compared to previously reported results in air. All liquid media investigated here showed a stabilizing effect. Maximum stability was found for immersion in isopropanol. The size of the damage generated was mainly influenced by the viscosity of the liquids. The results do not support a stress corrosion cracking process.

Development of a nano manipulator based on an atomic force microscope coupled with a haptic device: a novel manipulation tool for scanning electron microscopy

We developed a novel nano manipulator based on an atomic force microscope (AFM) that can be operated inside the sample chamber of a scanning electron microscope (SEM). This AFM manipulator is also coupled with a haptic device, and the nanometer-scale movement of the AFM cantilever can be scaled up to the millimeter-scale movement of the pen handle of the haptic device. Using this AFM manipulation system, we were able to observe the AFM cantilever and samples under the SEM and obtain topographical images of the AFM under the SEM. These AFM images contained quantitative height information of the sample that is difficult to obtain from SEM images. Our system was also useful for positioning the cantilever for accurate AFM manipulation because the manipulation scene could be directly observed in real time by SEM. Coupling of the AFM manipulator with the haptic device was also useful for manipulation in the SEM since the operator can move the AFM probe freely at any position on the sample surface while feeling the interaction force between the probe and the sample surface. We tested two types of cutting methods: simple cutting and vibration cutting. Our results showed that vibration cutting with probe oscillation is very useful for the dissection of biological samples which were dried for SEM observation. Thus, cultivated HeLa cells were successfully micro-dissected by vibration cutting, and the dissection process could be observed in real time in the SEM. This AFM manipulation system is expected to serve as a powerful tool for dissecting various biological samples at the micro and nanometer-scale under SEM observation.

Pulse gas alignment and AFM manipulation of single-wall carbon nanotube

In the fabrication process of nanoelectronic device arrays based on single-wall carbon nanotube (SWCNT), oriented alignment of SWCNTs and property modification of metallic SWCNTs in the array are the key problems to be solved. Pulse gas alignment with substrate downward tilt is proposed to realize the controllable alignment of SWCNTs. Experimental results demonstrate that 84% SWCNTs are aligned in −15°−15° angular to the pulse gas direction. A modified nanomanipulation technology based on atomic force microscope (AFM) is utilized to perform various kinds of SWCNT manipulation, such as SWCNT separation from the “Y” CNT, catalyst removal from the SWCNT end, continual nano buckles fabrication on SWCNT and even stretching to break, which provides a feasible way to modify the size, shape and the electrical property of SWCNTs.

Atomic force microscope manipulation of gold nanoparticles for controlled Raman enhancement

We report on the controlled manipulation of two, three and four gold nanoparticles (AuNPs) using an atomic force microscope (AFM) for use as surface-enhanced Raman scattering substrates. For each arrangement, the interparticle electromagnetic (EM) coupling between adjacent AuNPs is studied at different polarization angles. It is found that the strength of EM coupling strongly depends on the arrangement of the AuNPs. In particular, the highest enhancement and the most pronounced polarization dependence is found for linear arrangement of closely spaced particles. Our results show that AFM manipulation has great potential for fabrication and investigation of controlled arrangements of nanoscale objects.

Manipulation of freestanding Au nanogears using an atomic force microscope

We have fabricated freestanding nanogears by selectively etching single crystalline Aunanoplates and assembled them tooth to tooth using an atomic force microscope (AFM).The nanogears, with one center hole surrounded by six teeth, are smaller than 500 nm inoverall size and 60–70 nm in thickness. We demonstrate that blunt AFM tips on stiffcantilevers are effective for the nondestructive manipulation of ductile and flat nano-objectshaving large contact areas with the substrate, and we discuss the results on the basis ofnanomechanical aspects. We expect that the precise AFM manipulation combined with theetch-based fabrication techniques for the freestanding nanocomponents will be useful in thedevelopment and post-repair of sophisticated nanoelectromechanical systems.