Collective electronic effects in scanning probe microscopy

The surface plasmon dispersion relations are calculated for a metal coated dielectric probe above a dielectric half space with and without metal coating. Employing prolate spheroidal coordinate system this configuration was modeled as confocal single-sheeted hyperboloids of revolution superimposed on planar domains. The involved media are characterized by frequency dependent, spatially local dielectric functions. Due to subwavelength dimensions of the region of interest, nonretarded electrodynamics is utilized to derive exact analytical expressions describing the resonant surface modes. The dis-persion relations are studied as functions of the parameter that defines the hyperboloidal boundaries of the tip and the corresponding coating, and as functions of the involved coating thicknesses. Both parallel and perpendicular polarizations are considered. The results are simulated numerically and limiting cases are discussed with comparison to the Cartesian thin foil case. Using this new type of probe-substrate configuration, the surface plasmon coupling mechanism is investigated experimentally utilizing a scanning probe microscope, and the signal strength acquired by the probe is measured as a function of the distance between the probe and the sample. This is repeated at three different wavelengths of the incident p-polarized photons used to stimulate surface plasmons in the thin metal foil. The results are compared with the theory. Utilizing the prolate spheroidal coordinate system, the related and relevant problem of the Coulomb interaction of a dielectric probe tip with a uniform field existing above a semiinfinite, homogeneous dielectric substrate was studied. This is of interest in atomic force microscopy when the sample surface is electrically charged. The induced polarization surface charge density and the field distribution at the bounding surface of the dielectric medium with the geometry of a single-sheeted hyperboloid of revolution located above the dielectric half space interfaced with a uniform surface charge density is calculated. The force density on the hyperboloidal probe medium is calculated as a function of the probe tip shape. The potential and the field distributions are calculated in the neighborhood of the apex of the tip. The calculation is based on solving Laplace\u27s equation and employing a newly derived integral expansion for the vanishing dielectric limit of the potential. The integral expansion is analytically proved and numerically verified. The involved numerical simulations comprise the evaluation of infinite double integrals involving conical functions similar to those arising in the Mehler-Fock integral transform

Optically assisted trapping with high-permittivity dielectric rings: Towards optical aerosol filtration

Controlling the transport, trapping, and filtering of nanoparticles is important for many applications. By virtue of their weak response to gravity and their thermal motion, various physical mechanisms can be exploited for such operations on nanoparticles. However, the manipulation based on optical forces is potentially most appealing since it constitutes a highly deterministic approach. Plasmonic nanostructures have been suggested for this purpose, but they possess the disadvantages of locally generating heat and trapping the nanoparticles directly on surface. Here, we propose the use of dielectric rings made of high permittivity materials for trapping nanoparticles. Thanks to their ability to strongly localize the field in space, nanoparticles can be trapped without contact. We use a semi-analytical method to study the ability of these rings to trap nanoparticles. Results are supported by full-wave simulations. Application of the trapping concept to nanoparticle filtration is suggested.Comment: 5 figure

Nanometrology of Biomass for Bioenergy: The Role of Atomic Force Microscopy and Spectroscopy in Plant Cell Characterization

Ethanol production using extracted cellulose from plant cell walls (PCW) is a very promising approach to biofuel production. However, efficient throughput has been hindered by the phenomenon of recalcitrance, leading to high costs for the lignocellulosic conversion. To overcome recalcitrance, it is necessary to understand the chemical and structural properties of the plant biological materials, which have evolved to generate the strong and cohesive features observed in plants. Therefore, tools and methods that allow the investigation of how the different molecular components of PCW are organized and distributed and how this impacts the mechanical properties of the plants are needed but challenging due to the molecular and morphological complexity of PCW. Atomic force microscopy (AFM), capitalizing on the interfacial nanomechanical forces, encompasses a suite of measurement modalities for nondestructive material characterization. Here, we present a review focused on the utilization of AFM for imaging and determination of physical properties of plant-based specimens. The presented review encompasses the AFM derived techniques for topography imaging (AM-AFM), mechanical properties (QFM), and surface/subsurface (MSAFM, HPFM) chemical composition imaging. In particular, the motivation and utility of force microscopy of plant cell walls from the early fundamental investigations to achieve a better understanding of the cell wall architecture, to the recent studies for the sake of advancing the biofuel research are discussed. An example of delignification protocol is described and the changes in morphology, chemical composition and mechanical properties and their correlation at the nanometer scale along the process are illustrated

Nanosystems, Edge Computing, and the Next Generation Computing Systems

It is widely recognized that nanoscience and nanotechnology and their subfields, such as nanophotonics, nanoelectronics, and nanomechanics, have had a tremendous impact on recent advances in sensing, imaging, and communication, with notable developments, including novel transistors and processor architectures. For example, in addition to being supremely fast, optical and photonic components and devices are capable of operating across multiple orders of magnitude length, power, and spectral scales, encompassing the range from macroscopic device sizes and kW energies to atomic domains and single-photon energies. The extreme versatility of the associated electromagnetic phenomena and applications, both classical and quantum, are therefore highly appealing to the rapidly evolving computing and communication realms, where innovations in both hardware and software are necessary to meet the growing speed and memory requirements. Development of all-optical components, photonic chips, interconnects, and processors will bring the speed of light, photon coherence properties, field confinement and enhancement, information-carrying capacity, and the broad spectrum of light into the high-performance computing, the internet of things, and industries related to cloud, fog, and recently edge computing. Conversely, owing to their extraordinary properties, 0D, 1D, and 2D materials are being explored as a physical basis for the next generation of logic components and processors. Carbon nanotubes, for example, have been recently used to create a new processor beyond proof of principle. These developments, in conjunction with neuromorphic and quantum computing, are envisioned to maintain the growth of computing power beyond the projected plateau for silicon technology. We survey the qualitative figures of merit of technologies of current interest for the next generation computing with an emphasis on edge computing

Measurement of Mechanical Properties of Cantilever Shaped Materials

Microcantilevers were first introduced as imaging probes in Atomic Force Microscopy (AFM) due to their extremely high sensitivity in measuring surface forces. The versatility of these probes, however, allows the sensing and measurement of a host of mechanical properties of various materials. Sensor parameters such as resonance frequency, quality factor, amplitude of vibration and bending due to a differential stress can all be simultaneously determined for a cantilever. When measuring the mechanical properties of materials, identifying and discerning the most influential parameters responsible for the observed changes in the cantilever response are important. We will, therefore, discuss the effects of various force fields such as those induced by mass loading, residual stress, internal friction of the material, and other changes in the mechanical properties of the microcantilevers. Methods to measure variations in temperature, pressure, or molecular adsorption of water molecules are also discussed. Often these effects occur simultaneously, increasing the number of parameters that need to be concurrently measured to ensure the reliability of the sensors. We therefore systematically investigate the geometric and environmental effects on cantilever measurements including the chemical nature of the underlying interactions. To address the geometric effects we have considered cantilevers with a rectangular or circular cross section. The chemical nature is addressed by using cantilevers fabricated with metals and/or dielectrics. Selective chemical etching, swelling or changes in Young’s modulus of the surface were investigated by means of polymeric and inorganic coatings. Finally to address the effect of the environment in which the cantilever operates, the Knudsen number was determined to characterize the molecule-cantilever collisions. Also bimaterial cantilevers with high thermal sensitivity were used to discern the effect of temperature variations. When appropriate, we use continuum mechanics, which is justified according to the ratio between the cantilever thickness and the grain size of the materials. We will also address other potential applications such as the ageing process of nuclear materials, building materials, and optical fibers, which can be investigated by monitoring their mechanical changes with time. In summary, by virtue of the dynamic response of a miniaturized cantilever shaped material, we present useful measurements of the associated elastic properties

Behind the paper; "In situ plant materials hyperspectral imaging by multimodal scattering near-field optical microscopy"

Post regarding the impact of near field optical microscopy for plant cell walls investigation