Incomplete decapitation in suicidal vehicle-assisted ligature strangulation: A case report and a review of the literature.

Vehicle-assisted ligature strangulation is an extremely rare suicide method. We report a case of a 43-year-old man who secured one end of a nylon rope to a tree and the other end around his neck, then got inside his vehicle and stepped on the gas, leading to an incomplete decapitation. A sharply demarcated encircling ligature mark was found upon external examination, along with a deep laceration in the anterior region of the neck. The severance plane passed between the third and fourth cervical vertebrae, with diffuse haemorrhagic infiltration of the cervical muscles, in accordance with autopsy findings reported in the literature. The lung histological examination described a large amount of red blood cells and pulmonary oedema. A review of the literature concerning suicidal vehicle-assisted ligature strangulation cases allowed us to investigate some common autopsy findings, as well as the rope features relevant to the beheading.

Thermal Imaging of Block Copolymers with Sub-10 nm Resolution.

Thermal silicon probes have demonstrated their potential to investigate the thermal properties of various materials at high resolution. However, a thorough assessment of the achievable resolution is missing. Here, we present a probe-based thermal-imaging technique capable of providing sub-10 nm lateral resolution at a sub-10 ms pixel rate. We demonstrate the resolution by resolving microphase-separated PS-b-PMMA block copolymers that self-assemble in 11 to 19 nm half-period lamellar structures. We resolve an asymmetry in the heat flux signal at submolecular dimensions and assess the ratio of heat flux into both polymers in various geometries. These observations are quantitatively compared with coarse-grained molecular simulations of energy transport that reveal an enhancement of transport along the macromolecular backbone and a Kapitza resistance at the internal interfaces of the self-assembled structure. This comparison discloses a tip-sample contact radius of a ≈ 4 nm and identifies combinations of enhanced intramolecular transport and Kapitza resistance.

Exploring Strategies to Contact 3D Nano-Pillars.

This contribution explores different strategies to electrically contact vertical pillars with diameters less than 100 nm. Two process strategies have been defined, the first based on Atomic Force Microscope (AFM) indentation and the second based on planarization and reactive ion etching (RIE). We have demonstrated that both proposals provide suitable contacts. The results help to conclude that the most feasible strategy to be implementable is the one using planarization and reactive ion etching since it is more suitable for parallel and/or high-volume manufacturing processing.

Grain-Boundary-Induced Alignment of Block Copolymer Thin Films.

We present and discuss the capability of grain boundaries to induce order in block copolymer thin films between horizontally and vertically assembled block copolymer grains. The system we use as a proof of principle is a thermally annealed 23.4 nm full-pitch lamellar Polystyrene-block-polymethylmetacrylate (PS-b-PMMA) di-block copolymer. In this paper, grain-boundary-induced alignment is achieved by the mechanical removal of the neutral brush layer via atomic force microscopy (AFM). The concept is also confirmed by a mask-less e-beam direct writing process. An elongated grain of vertically aligned lamellae is trapped between two grains of horizontally aligned lamellae. This configuration leads to the formation of 90° twist grain boundaries. The features maintain their orientation on a characteristic length scale, which is described by the material's correlation length ξ. As a result of an energy minimization process, the block copolymer domains in the vertically aligned grain orient perpendicularly to the grain boundary. The energy-minimizing feature is the grain boundary itself. The width of the manipulated area (e.g., the horizontally aligned grain) does not represent a critical process parameter.

Towards molecular electronic devices based on 'all-carbon' wires.

Nascent molecular electronic devices based on linear 'all-carbon' wires attached to gold electrodes through robust and reliable C-Au contacts are prepared via efficient in situ sequential cleavage of trimethylsilyl end groups from an oligoyne, Me3Si-(C[triple bond, length as m-dash]C)4-SiMe3 (1). In the first stage of the fabrication process, removal of one trimethylsilyl (TMS) group in the presence of a gold substrate, which ultimately serves as the bottom electrode, using a stoichiometric fluoride-driven process gives a highly-ordered monolayer, Au|C[triple bond, length as m-dash]CC[triple bond, length as m-dash]CC[triple bond, length as m-dash]CC[triple bond, length as m-dash]CSiMe3 (Au|C8SiMe3). In the second stage, treatment of Au|C8SiMe3 with excess fluoride results in removal of the remaining TMS protecting group to give a modified monolayer Au|C[triple bond, length as m-dash]CC[triple bond, length as m-dash]CC[triple bond, length as m-dash]CC[triple bond, length as m-dash]CH (Au|C8H). The reactive terminal C[triple bond, length as m-dash]C-H moiety in Au|C8H can be modified by 'click' reactions with (azidomethyl)ferrocene (N3CH2Fc) to introduce a redox probe, to give Au|C6C2N3HCH2Fc. Alternatively, incubation of the modified gold substrate supported monolayer Au|C8H in a solution of gold nanoparticles (GNPs), results in covalent attachment of GNPs on top of the film via a second alkynyl carbon-Au σ-bond, to give structures Au|C8|GNP in which the monolayer of linear, 'all-carbon' C8 chains is sandwiched between two macroscopic gold contacts. The covalent carbon-surface bond as well as the covalent attachment of the metal particles to the monolayer by cleavage of the alkyne C-H bond is confirmed by surface-enhanced Raman scattering (SERS). The integrity of the carbon chain in both Au|C6C2N3HCH2Fc systems and after formation of the gold top-contact electrode in Au|C8|GNP is demonstrated through electrochemical methods. The electrical properties of these nascent metal-monolayer-metal devices Au|C8|GNP featuring 'all-carbon' molecular wires were characterised by sigmoidal I-V curves, indicative of well-behaved junctions free of short circuits.

Quantification of nanomechanical properties of surfaces by higher harmonic monitoring in amplitude modulated AFM imaging.

The determination of nanomechanical properties is an intensive topic of study in several fields of nanophysics, from surface and materials science to biology. At the same time, amplitude modulation force microscopy is one of the most established techniques for nanoscale characterization. In this work, we combine these two topics and propose a method able to extract quantitative nanomechanical information from higher harmonic amplitude imaging in atomic force microscopy. With this method it is possible to discriminate between different materials in the stiffness range of 1-3 GPa, in our case thin films of PS-PMMA based block copolymers. We were able to obtain a critical lateral resolution of less than 20 nm and discriminate between materials with less than a 1 GPa difference in modulus. We show that within this stiffness range, reliable values of the Young's moduli can be obtained under usual imaging conditions and with standard dynamic AFM probes.

Identifying the nature of surface chemical modification for directed self-assembly of block copolymers.

In recent years, block copolymer lithography has emerged as a viable alternative technology for advanced lithography. In chemical-epitaxy-directed self-assembly, the interfacial energy between the substrate and each block copolymer domain plays a key role on the final ordering. Here, we focus on the experimental characterization of the chemical interactions that occur at the interface built between different chemical guiding patterns and the domains of the block copolymers. We have chosen hard X-ray high kinetic energy photoelectron spectroscopy as an exploration technique because it provides information on the electronic structure of buried interfaces. The outcome of the characterization sheds light onto key aspects of directed self-assembly: grafted brush layer, chemical pattern creation and brush/block co-polymer interface.

Suspended tungsten-based nanowires with enhanced mechanical properties grown by focused ion beam induced deposition.

The implementation of three-dimensional (3D) nano-objects as building blocks for the next generation of electro-mechanical, memory and sensing nano-devices is at the forefront of technology. The direct writing of functional 3D nanostructures is made feasible by using a method based on focused ion beam induced deposition (FIBID). We use this technique to grow horizontally suspended tungsten nanowires and then study their nano-mechanical properties by three-point bending method with atomic force microscopy. These measurements reveal that these nanowires exhibit a yield strength up to 12 times higher than that of the bulk tungsten, and near the theoretical value of 0.1 times the Young's modulus (E). We find a size dependence of E that is adequately described by a core-shell model, which has been confirmed by transmission electron microscopy and compositional analysis at the nanoscale. Additionally, we show that experimental resonance frequencies of suspended nanowires (in the MHz range) are in good agreement with theoretical values. These extraordinary mechanical properties are key to designing electro-mechanically robust nanodevices based on FIBID tungsten nanowires.

Functional dependence of resonant harmonics on nanomechanical parameters in dynamic mode atomic force microscopy.

We present a combined theoretical and experimental study of the dependence of resonant higher harmonics of rectangular cantilevers of an atomic force microscope (AFM) as a function of relevant parameters such as the cantilever force constant, tip radius and free oscillation amplitude as well as the stiffness of the sample's surface. The simulations reveal a universal functional dependence of the amplitude of the 6th harmonic (in resonance with the 2nd flexural mode) on these parameters, which can be expressed in terms of a gun-shaped function. This analytical expression can be regarded as a practical tool for extracting qualitative information from AFM measurements and it can be extended to any resonant harmonics. The experiments confirm the predicted dependence in the explored 3-45 N/m force constant range and 2-345 GPa sample's stiffness range. For force constants around 25 N/m, the amplitude of the 6th harmonic exhibits the largest sensitivity for ultrasharp tips (tip radius below 10 nm) and polymers (Young's modulus below 20 GPa).

Assessing the Local Nanomechanical Properties of Self-Assembled Block Copolymer Thin Films by Peak Force Tapping.

The mechanical properties of several types of block copolymer (BCP) thin films have been investigated using PeakForce quantitative nanomechanical mapping. The samples consisted of polystyrene/poly(methylmethacrylate) (PS/PMMA)-based BCP thin films with different pitches both randomly oriented and self-assembled. The measured films have a critical thickness below 50 nm and present features to be resolved of less than 22 nm. Beyond measuring and discriminate surface elastic modulus and adhesion forces of the different phases, we tuned the peak force parameters in order to reliably image those samples, avoiding plastic deformation. The method is able to detect the changes in mechanical response associated with the orientation of the PMMA cylinders with respect to the substrate (parallel versus vertical). The nanomechanical investigation is also capable of recognizing local stiffening due to the preferential growth of alumina deposited by atomic layer deposition on BCP samples, opening up new possibilities in the field of hard mask materials characterization.

Boosting the local anodic oxidation of silicon through carbon nanofiber atomic force microscopy probes.

Many nanofabrication methods based on scanning probe microscopy have been developed during the last decades. Local anodic oxidation (LAO) is one of such methods: Upon application of an electric field between tip and surface under ambient conditions, oxide patterning with nanometer-scale resolution can be performed with good control of dimensions and placement. LAO through the non-contact mode of atomic force microscopy (AFM) has proven to yield a better resolution and tip preservation than the contact mode and it can be effectively performed in the dynamic mode of AFM. The tip plays a crucial role for the LAO-AFM, because it regulates the minimum feature size and the electric field. For instance, the feasibility of carbon nanotube (CNT)-functionalized tips showed great promise for LAO-AFM, yet, the fabrication of CNT tips presents difficulties. Here, we explore the use of a carbon nanofiber (CNF) as the tip apex of AFM probes for the application of LAO on silicon substrates in the AFM amplitude modulation dynamic mode of operation. We show the good performance of CNF-AFM probes in terms of resolution and reproducibility, as well as demonstration that the CNF apex provides enhanced conditions in terms of field-induced, chemical process efficiency.

Sub-10 nm resistless nanolithography for directed self-assembly of block copolymers.

The creation of highly efficient guiding patterns for the directed self-assembly of block copolymers by resistless nanolithography using atomic force microscopy (AFM) is demonstrated. It is shown that chemical patterns consisting of arrays of lines defined on a brush layer by AFM allow the alignment of the blocks of lamella-forming polymers. The main advantage of this method relies on the capability to create high-resolution (sub-10 nm line-width) guiding patterns and the reduction of the number of process steps compared to the state-of-the-art methods for creating guiding patterns by chemical surface modification. It is found that the guiding patterns induce the block alignment very efficiently, allowing the achievement of a density multiplication factor of 7 for block copolymers of 14 nm half-pitch, which is attributed to the combined effect of topographical and chemical modification.

Simple and effective graphene laser processing for neuron patterning application.

A straightforward fabrication technique to obtain patterned substrates promoting ordered neuron growth is presented. Chemical vapor deposition (CVD) single layer graphene (SLG) was machined by means of single pulse UV laser ablation technique at the lowest effective laser fluence in order to minimize laser damage effects. Patterned substrates were then coated with poly-D-lysine by means of a simple immersion in solution. Primary embryonic hippocampal neurons were cultured on our substrate, demonstrating an ordered interconnected neuron pattern mimicking the pattern design. Surprisingly, the functionalization is more effective on the SLG, resulting in notably higher alignment for neuron adhesion and growth. Therefore the proposed technique should be considered a valuable candidate to realize a new generation of highly specialized biosensors.

Oxidative and carbonaceous patterning of Si surface in an organic media by scanning probe lithography.

A simple top-down fabrication technique that involves scanning probe lithography on Si is presented. The writing procedure consists of a chemically selective patterning in mesitylene. Operating in an organic media is possible to perform local oxidation or solvent decomposition during the same pass by tuning the applied bias. The layer deposited with a positively biased tip with sub-100-nm lateral resolution consists of nanocrystalline graphite, as verified by Raman spectroscopy. The oxide pattern obtained in opposite polarization is later used as a mask for dry etching, showing a remarkable selectivity in SF6 plasma, to produce Si nanofeatured molds.