Focused Helium Ion and Electron Beam-Induced Deposition of Organometallic Tips for Dynamic Atomic Force Microscopy of Biomolecules in Liquid.

We demonstrate the fabrication of sharp nanopillars of high aspect ratio onto specialized atomic force microscopy (AFM) microcantilevers and their use for high-speed AFM of DNA and nucleoproteins in liquid. The fabrication technique uses localized charged-particle-induced deposition with either a focused beam of helium ions or electrons in a helium ion microscope (HIM) or scanning electron microscope (SEM). This approach enables customized growth onto delicate substrates with nanometer-scale placement precision and in situ imaging of the final tip structures using the HIM or SEM. Tip radii of <10 nm are obtained and the underlying microcantilever remains intact. Instead of the more commonly used organic precursors employed for bio-AFM applications, we use an organometallic precursor (tungsten hexacarbonyl) resulting in tungsten-containing tips. Transmission electron microscopy reveals a thin layer of carbon on the tips. The interaction of the new tips with biological specimens is therefore likely very similar to that of standard carbonaceous tips, with the added benefit of robustness. A further advantage of the organometallic tips is that compared to carbonaceous tips they better withstand UV-ozone cleaning treatments to remove residual organic contaminants between experiments, which are inevitable during the scanning of soft biomolecules in liquid. Our tips can also be grown onto the blunted tips of previously used cantilevers, thus providing a means to recycle specialized cantilevers and restore their performance to the original manufacturer specifications. Finally, a focused helium ion beam milling technique to reduce the tip radii and thus further improve lateral spatial resolution in the AFM scans is demonstrated.

Fabrication of Specimens for Atom Probe Tomography Using a Combined Gallium and Neon Focused Ion Beam Milling Approach.

We demonstrate a new focused ion beam sample preparation method for atom probe tomography. The key aspect of the new method is that we use a neon ion beam for the final tip-shaping after conventional annulus milling using gallium ions. This dual-ion approach combines the benefits of the faster milling capability of the higher current gallium ion beam with the chemically inert and higher precision milling capability of the noble gas neon ion beam. Using a titanium-aluminum alloy and a layered aluminum/aluminum-oxide tunnel junction sample as test cases, we show that atom probe tips prepared using the combined gallium and neon ion approach are free from the gallium contamination that typically frustrates composition analysis of these materials due to implantation, diffusion, and embrittlement effects. We propose that by using a focused ion beam from a noble gas species, such as the neon ions demonstrated here, atom probe tomography can be more reliably performed on a larger range of materials than is currently possible using conventional techniques.

Probing the Critical Nucleus Size in the Metal-Insulator Phase Transition of VO_{2}.

In a first-order phase transition, critical nucleus size governs nucleation kinetics, but the direct experimental test of the theory and determination of the critical nucleation size have been achieved only recently in the case of ice formation in supercooled water. The widely known metal-insulator phase transition (MIT) in strongly correlated VO_{2} is a first-order electronic phase transition coupled with a solid-solid structural transformation. It is unclear whether classical nucleation theory applies in such a complex case. In this Letter, we directly measure the critical nucleus size of the MIT by introducing size-controlled nanoscale nucleation seeds with focused ion irradiation at the surface of a deeply supercooled metal phase of VO_{2}. The results compare favorably with classical nucleation theory and are further explained by phase-field modeling. This Letter validates the application of classical nucleation theory as a parametrizable model to describe phase transitions of strongly correlated electron materials.

A realist evaluation of a multifactorial falls prevention programme in care homes.

BACKGROUND: falls in care homes are common, costly and hard to prevent.Multifactorial falls programmes demonstrate clinical and cost-effectiveness, but the heterogeneity of the care home sector is a barrier to their implementation. A fuller appreciation of the relationship between care home context and falls programme delivery will guide development and support implementation. METHODS: this is a multi-method process evaluation informed by a realist approach.Data include fidelity observations, stakeholder interviews, focus groups, documentary review and falls-rate data. Thematic analysis of qualitative data and descriptive statistics are synthesised to generate care home case studies. RESULTS: data were collected in six care homes where a falls programme was trialled. Forty-four interviews and 11 focus groups complemented observations and document review.The impact of the programme varied. Five factors were identified: (i) prior practice and (ii) training may inhibit new ways of working; (iii) some staff may be reluctant to take responsibility for falls; (iv) some may feel that residents living with dementia cannot be prevented from falling; and, (v) changes to management may disturb local innovation.In some care homes, training and improved awareness generated a reduction in falls without formal assessments being carried out. CONCLUSIONS: different aspects of the falls programme sparked different mechanisms in different settings, with differing impact upon falls.The evaluation has shown that elements of a multifactorial falls programme can work independently of each other and that it is the local context (and local challenges faced), which should shape how a falls programme is implemented.

A multidomain decision support tool to prevent falls in older people: the FinCH cluster RCT.

BACKGROUND: Falls in care home residents are common, unpleasant, costly and difficult to prevent. OBJECTIVES: The objectives were to evaluate the clinical effectiveness and cost-effectiveness of the Guide to Action for falls prevention in Care Homes (GtACH) programme. DESIGN: A multicentre, cluster, parallel, 1 : 1 randomised controlled trial with embedded process evaluation and economic evaluation. Care homes were randomised on a 1 : 1 basis to the GtACH programme or usual care using a secure web-based randomisation service. Research assistants, participating residents and staff informants were blind to allocation at recruitment; research assistants were blind to allocation at follow-up. NHS Digital data were extracted blindly. SETTING: Older people's care homes from 10 UK sites. PARTICIPANTS: Older care home residents. INTERVENTION: The GtACH programme, which includes care home staff training, systematic use of a multidomain decision support tool and implementation of falls prevention actions, compared to usual falls prevention care. OUTCOMES: The primary trial outcome was the rate of falls per participating resident occurring during the 90-day period between 91 and 180 days post randomisation. The primary outcome for the cost-effectiveness analysis was the cost per fall averted, and the primary outcome for the cost-utility analysis was the incremental cost per quality adjusted life-year. Secondary outcomes included the rate of falls over days 0-90 and 181-360 post randomisation, activity levels, dependency and fractures. The number of falls per resident was compared between arms using a negative binomial regression model (generalised estimating equation). RESULTS: A total of 84 care homes were randomised: 39 to the GtACH arm and 45 to the control arm. A total of 1657 residents consented and provided baseline measures (mean age 85 years, 32% men). GtACH programme training was delivered to 1051 staff (71% of eligible staff) over 146 group sessions. Primary outcome data were available for 630 GtACH participants and 712 control participants. The primary outcome result showed an unadjusted incidence rate ratio of 0.57 (95% CI 0.45 to 0.71; p < 0.01) in favour of the GtACH programme. Falls rates were lower in the GtACH arm in the period 0-90 days. There were no other differences between arms in the secondary outcomes. Care home staff valued the training, systematic strategies and specialist peer support, but the incorporation of the GtACH programme documentation into routine care home practice was limited. No adverse events were recorded. The incremental cost was £20,889.42 per Dementia Specific Quality of Life-based quality-adjusted life-year and £4543.69 per quality-adjusted life-year based on the EuroQol-5 dimensions, five-level version. The mean number of falls was 1.889 (standard deviation 3.662) in the GtACH arm and 2.747 (standard deviation 7.414) in the control arm. Therefore, 0.858 falls were averted. The base-case incremental cost per fall averted was £190.62. CONCLUSION: The GtACH programme significantly reduced the falls rate in the study care homes without restricting residents' activity levels or increasing their dependency, and was cost-effective at current thresholds in the NHS. FUTURE WORK: Future work should include a broad implementation programme, focusing on scale and sustainability of the GtACH programme. LIMITATIONS: A key limitation was the fact that care home staff were not blinded, although risk was small because of the UK statutory requirement to record falls in care homes. TRIAL REGISTRATION: This trial is registered as ISRCTN34353836. FUNDING: This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 26, No. 9. See the NIHR Journals Library website for further project information.

Falls in care home residents are common, unpleasant, costly and hard to prevent. We tested whether or not the Guide to Action for falls prevention in Care Homes (GtACH) programme was effective in preventing falls. In this programme, care home staff were systematically trained and supported in the assessment of residents' risk of falling and the generation of a falls reduction care plan. We undertook a randomised controlled trial comparing the GtACH programme with usual care, which does not involve this systematic attention to falls prevention. We also undertook a process evaluation, observing organisational and care processes, and an economic study to evaluate value for money. A total of 39 care homes were randomly allocated to the GtACH programme and 45 care homes were randomly allocated to usual care, involving a total of 1657 residents. The main comparison between the two arms was the rate of falls during months 4­6 after randomisation, when we expected any effect to be at its peak. We also assessed the falls rates before and 6 months after this period. We measured activity and dependency levels, as it was important to be sure that any reduction in the rate of falls was not achieved through restrictive care practices. We saw a 43% reduction in the falls rates of the GtACH programme participants during months 4­6, without observing any reduction in residents' activity or dependency. Care home staff and relatives were positive about the GtACH programme. The GtACH programme was good value for money, as it was likely to be cost-effective. The effect of the programme waned over months 6­12, which may be because some staff did not embed the GtACH programme in their usual practice routines, and awareness levels may have dropped.

A review of defect engineering, ion implantation, and nanofabrication using the helium ion microscope.

The helium ion microscope has emerged as a multifaceted instrument enabling a broad range of applications beyond imaging in which the finely focused helium ion beam is used for a variety of defect engineering, ion implantation, and nanofabrication tasks. Operation of the ion source with neon has extended the reach of this technology even further. This paper reviews the materials modification research that has been enabled by the helium ion microscope since its commercialization in 2007, ranging from fundamental studies of beam-sample effects, to the prototyping of new devices with features in the sub-10 nm domain.

Fast Grain Mapping with Sub-Nanometer Resolution Using 4D-STEM with Grain Classification by Principal Component Analysis and Non-Negative Matrix Factorization.

High-throughput grain mapping with sub-nanometer spatial resolution is demonstrated using scanning nanobeam electron diffraction (also known as 4D scanning transmission electron microscopy, or 4D-STEM) combined with high-speed direct-electron detection. An electron probe size down to 0.5 nm in diameter is used and the sample investigated is a gold­palladium nanoparticle catalyst. Computational analysis of the 4D-STEM data sets is performed using a disk registration algorithm to identify the diffraction peaks followed by feature learning to map the individual grains. Two unsupervised feature learning techniques are compared: principal component analysis (PCA) and non-negative matrix factorization (NNMF). The characteristics of the PCA versus NNMF output are compared and the potential of the 4D-STEM approach for statistical analysis of grain orientations at high spatial resolution is discussed.

Learning from a successful process evaluation in care homes.

INTRODUCTION: process evaluations (PE) are increasingly used in parallel with randomised controlled trials (RCT) to inform the implementation of complex health interventions. This paper explores the learning accrued from conducting a PE within the Falls in Care Homes Study (FinCH), a large UK RCT. METHODS: in the FinCH study, six purposively sampled care homes provided data for the PE, which followed a realist approach. In this study researchers kept written diaries of their experiences in completing the interviews, focus groups and observations. We have reflected on these and present the main themes for discussion. FINDINGS: care home staff were enthusiastic to participate in the PE but researchers found it difficult to collect data due to staff not having time to take part, environmental factors such as no space for focus groups and low levels of research understanding. Researchers found that the expectations of the PE protocol were often unrealistic due to these limitations. Flexible and pragmatic approaches such as interviews in place of focus groups enabled data collection but required a reduced sample size and length of data collection to be accepted by researchers. CONCLUSION: to enable care home staff to participate in successful PEs, researchers should build flexibility into research schedules, spend time building trust, collaborate with all levels of care home staff prior to data collection, increase research capacity in care home staff and co-design research projects.

Branched High Aspect Ratio Nanostructures Fabricated by Focused Helium Ion Beam Induced Deposition of an Insulator.

Helium ion beam induced deposition using the gaseous precursor pentamethylcyclopentasiloxane is employed to fabricate high aspect ratio insulator nanostructures (nanopillars and nanocylinders) that exhibit charge induced branching. The branched nanostructures are analyzed by transmission electron microscopy. It is found that the side branches form above a certain threshold height and that by increasing the flow rate of the precursor, the vertical growth rate and branching phenomenon can be significantly enhanced, with fractalesque branching patterns observed. The direct-write ion beam nanofabrication technique described herein offers a fast single-step method for the growth of high aspect ratio branched nanostructures with site-selective placement on the nanometer scale.

Selective Gas Permeation in Defect-Engineered Bilayer Graphene.

Defective graphene holds great potential to enable the permeation of gas molecules at high rates with high selectivity due to its one-atom thickness and resultant atomically small pores at the defect sites. However, precise control and tuning of the size and density of the defects remain challenging. In this work, we introduce atomic-scale defects into bilayer graphene via a decoupled strategy of defect nucleation using helium ion irradiation followed by defect expansion using hydrogen plasma treatment. The cotreated membranes exhibit high permeability and simultaneously high selectivity compared to those singly treated by ion irradiation or hydrogen plasma only. High permeation selectivity values for H2/N2 and H2/CH4 of 495 and 877, respectively, are achieved for optimally cotreated membranes. The method presented can also be scaled up to prepare large-area membranes for gas separation, e.g., for hydrogen purification and recovery from H2/CH4 and H2/N2 mixtures.

Structural color in Junonia butterflies evolves by tuning scale lamina thickness.

In diverse organisms, nanostructures that coherently scatter light create structural color, but how such structures are built remains mysterious. We investigate the evolution and genetic regulation of butterfly scale laminae, which are simple photonic nanostructures. In a lineage of buckeye butterflies artificially selected for blue wing color, we found that thickened laminae caused a color shift from brown to blue. Deletion of the optix patterning gene also altered color via lamina thickening, revealing shared regulation of pigments and lamina thickness. Finally, we show how lamina thickness variation contributes to the color diversity that distinguishes sexes and species throughout the genus Junonia. Thus, quantitatively tuning one dimension of scale architecture facilitates both the microevolution and macroevolution of a broad spectrum of hues. Because the lamina is an intrinsic component of typical butterfly scales, our findings suggest that tuning lamina thickness is an available mechanism to create structural color across the Lepidoptera.

From iridescent blues to vibrant purples, many butterflies display dazzling 'structural colors' created not by pigments but by microscopic structures that interfere with light. For instance, the scales that coat their wings can contain thin films of chitin, the substance that normally makes the external skeleton of insects. In slim layers, however, chitin can also scatter light to produce color, the way that oil can create iridescence at the surface of water. The thickness of the film, which is encoded by the genes of the butterfly, determines what color will be produced. Yet, little is known about how common thin films are in butterflies, exactly how genetic information codes for them, and how their thickness and the colors they produce can evolve. To investigate, Thayer et al. used a technique called Helium Ion Microscopy and examined the wings of ten related species of butterflies, showing that thin film structures were present across this sample. However, the different species have evolved many different structural colors over the past millions of years by changing the thickness of the films. Next, Thayer et al. showed that this evolution could be reproduced at a faster pace in the laboratory using common buckeye butterflies. These insects mostly have brown wings, but they can have specks of blue created by thin film structures. Individuals with more blue on their wings were mated and over the course of a year, the thickness of the film structures increased by 74%, leading to shiny blue butterflies. Deleting a gene called optix from the insects also led to blue wings. Optix was already known to control the patterns of pigments in butterflies, but it now appears that it controls structural colors as well. From solar panels to new fabrics, microscopic structures that can scatter light are useful in a variety of industries. Understanding how these elements exist and evolve in organisms may help to better design them for human purposes.

Ion Write Microthermotics: Programing Thermal Metamaterials at the Microscale.

Considerable advances in manipulating heat flow in solids have been made through the innovation of artificial thermal structures such as thermal diodes, camouflages, and cloaks. Such thermal devices can be readily constructed only at the macroscale by mechanically assembling different materials with distinct values of thermal conductivity. Here, we extend these concepts to the microscale by demonstrating a monolithic material structure on which nearly arbitrary microscale thermal metamaterial patterns can be written and programmed. It is based on a single, suspended silicon membrane whose thermal conductivity is locally, continuously, and reversibly engineered over a wide range (between 2 and 65 W/m·K) and with fine spatial resolution (10-100 nm) by focused ion irradiation. Our thermal cloak demonstration shows how ion-write microthermotics can be used as a lithography-free platform to create thermal metamaterials that control heat flow at the microscale.

Gallium, neon and helium focused ion beam milling of thin films demonstrated for polymeric materials: study of implantation artifacts.

Focused ion beam milling of ∼200 nm polymer thin films is investigated using a multibeam ion microscope equipped with a gallium liquid metal ion source and a helium/neon gas field-ionization source. The quality of gallium, neon, and helium ion milled edges in terms of ion implantation artifacts is analyzed using a combination of helium ion microscopy, transmission electron microscopy and light microscopy. Results for a synthetic polymer thin film, in the form of cryo-ultramicrotomed sections from a co-extruded polymer multilayer, and a biological polymer thin film, in the form of the base layer of a butterfly wing scale, are presented. While gallium and neon ion milling result in the implantation of ions up to tens of nanometers from the milled edge and local thinning near the edge, helium ion milling produces much sharper edges with dramatically reduced implantation. These effects can be understood in terms of the minimal lateral scatter and larger stopping distance of helium compared with the heavier ions, whereby due to the thin film geometry, most of the incident helium ions will pass straight through the material. The basic result demonstrated here for polymer thin films is also expected for thin films of hard materials such as metals and ceramics.

How People with Dementia and their Carers Adapt their Homes. A Qualitative Study.

The objective was to explore the ways in which people with dementia and their carers adapt their homes, including the barriers and use of available information. Semi-structured interviews were conducted with 10 people with dementia and their informal carer. The collected data were analysed using thematic analysis. Three core themes emerged: Maintaining familiarity and coping with change, Having knowledge and finding knowledge and Meeting challenges through home adaptation. The most significant barriers to making home adaptations were lack of knowledge and maintaining familiarity. Having more information and making home modifications earlier might enable individuals with dementia to adjust to their adapted environment.

Architecture-Guided Fluid Flow Directs Renal Biomineralization.

Nephrocalcinosis often begins on a calcium phosphate deposit, at the tip of the medullo-papillary complex (MPC) known as Randall's plaque (RP). Contextualizing proximally observed biominerals within the MPC has led us to postulate a mechanobiological switch that can trigger interstitial biomineralization at the MPC tip, remote from the intratubular biominerals. Micro X-ray computed tomography scans of human MPCs correlated with transmission and scanning electron micrographs, and X-ray energy dispersive spectrometry demonstrated novel findings about anatomically-specific biominerals. An abundance of proximal intratubular biominerals were associated with emergence of distal interstitial RP. The fundamental architecture of the MPC and mineral densities at the proximal and distal locations of the MPC differed markedly. A predominance of plate-like minerals or radially oriented plate-like crystallites within spheroidal minerals in the proximal intratubular locations, and core-shell type crystallites within spheroidal minerals in distal interstitial locations were observed. Based on the MPC anatomic location of structure-specific biominerals, a biological switch within the mineral-free zone occurring between the proximal and distal locations is postulated. The "on" and "off" switch is dependent on changes in the pressure differential resulting from changes in tubule diameters; the "Venturi effect" changes the "circumferential strain" and culminates in interstitial crystal deposits in the distal tubule wall in response to proximal tubular obstruction. These distal interstitial mineralizations can emerge into the collecting system of the kidney linking nephrocalcinosis with nephrolithiasis.

Campanile Near-Field Probes Fabricated by Nanoimprint Lithography on the Facet of an Optical Fiber.

One of the major challenges to the widespread adoption of plasmonic and nano-optical devices in real-life applications is the difficulty to mass-fabricate nano-optical antennas in parallel and reproducible fashion, and the capability to precisely place nanoantennas into devices with nanometer-scale precision. In this study, we present a solution to this challenge using the state-of-the-art ultraviolet nanoimprint lithography (UV-NIL) to fabricate functional optical transformers onto the core of an optical fiber in a single step, mimicking the 'campanile' near-field probes. Imprinted probes were fabricated using a custom-built imprinter tool with co-axial alignment capability with sub <100 nm position accuracy, followed by a metallization step. Scanning electron micrographs confirm high imprint fidelity and precision with a thin residual layer to facilitate efficient optical coupling between the fiber and the imprinted optical transformer. The imprinted optical transformer probe was used in an actual NSOM measurement performing hyperspectral photoluminescence mapping of standard fluorescent beads. The calibration scans confirmed that imprinted probes enable sub-diffraction limited imaging with a spatial resolution consistent with the gap size. This novel nano-fabrication approach promises a low-cost, high-throughput, and reproducible manufacturing of advanced nano-optical devices.

Nanoimprint of a 3D structure on an optical fiber for light wavefront manipulation.

Integration of complex photonic structures onto optical fiber facets enables powerful platforms with unprecedented optical functionalities. Conventional nanofabrication technologies, however, do not permit viable integration of complex photonic devices onto optical fibers owing to their low throughput and high cost. In this paper we report the fabrication of a three-dimensional structure achieved by direct nanoimprint lithography on the facet of an optical fiber. Nanoimprint processes and tools were specifically developed to enable a high lithographic accuracy and coaxial alignment of the optical device with respect to the fiber core. To demonstrate the capability of this new approach, a 3D beam splitter has been designed, imprinted and optically characterized. Scanning electron microscopy and optical measurements confirmed the good lithographic capabilities of the proposed approach as well as the desired optical performance of the imprinted structure. The inexpensive solution presented here should enable advancements in areas such as integrated optics and sensing, achieving enhanced portability and versatility of fiber optic components.