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Pro-oxidant additive containing (PAC) plastics is a term that describes a growing number of plastics which are designed to degrade in the unmanaged natural environment (open-air, soil, aquatic) through oxidation and other processes. It is a category that includes ‘oxo-degradable’ plastics, ‘oxo-biodegradable’ plastics and those containing ‘biotransformation’ additives. There is evidence that a new standard PAS 9017 : 2020 is relevant to predicting the timescale for abiotic degradation of PAC plastic in hot dry climates under ideal conditions (data reviewed for South of France and Florida). There are no reliable data to date to show that the PAS 9017 : 2020 predicts the timescale for abiotic degradation of PAC plastics in cool or wet climatic regions such as the UK or under less ideal conditions (soil burial, surface soiling etc.). Most PAC plastics studied in the literature showed biodegradability values in the range 5–60% and would not pass the criteria for biodegradability set in the new PAS 9017 : 2020. Possible formation of microplastics and cross-linking have been highlighted both by field studies and laboratory studies. Systematic eco-toxicity studies are needed to assess the possible effect of PAC additives and microplastics on the environment and biological organisms.

In the UK waste management systems biodegradable and compostable packaging are not automatically detected and separated. As a result, their fate is generally landfill or incineration, neither of which is an environmentally good outcome. Thus, effective sorting technologies for compostable plastics are needed to help improve composting rates of these materials and reduce the contamination of recycling waste streams. Hyperspectral imaging (HSI) was applied in this study to develop classification models for automatically identifying and classifying compostable plastics with the analysis focused on the spectral region 950–1,730 nm. The experimental design includes a hyperspectral imaging camera, allowing different chemometric techniques to be applied including principal component analysis (PCA) and partial least square discriminant analysis (PLS-DA) to develop a classification model for the compostable materials plastics. Materials used in this experimental analysis included compostable materials (sugarcane-derived and palm leaf derived), compostable plastics (PLA, PBAT) and conventional plastics (PP, PET, and LDPE). Our strategy was to develop a classification model to identify and categorize various fragments over the size range of 50 x 50 mm to 5 x 5 mm. Results indicated that both PCA and PLS-DA achieved classification scores of 100% when the size of material was larger than 10 mm x 10 mm. However, the misclassification rate increased to 20% for sugarcane-derived and 40% for palm leaf-based materials at sizes of 10 x 10 mm or below. In addition, for sizes of 5 x 5 mm, the misclassification rate for LDPE and PBAT increased to 20%, and for sugarcane and palm-leaf based materials to 60 and 80% respectively while the misclassification rate for PLA, PP, and PET was still 0%. The system is capable of accurately sorting compostable plastics (compostable spoons, forks, coffee lids) and differentiating them from identical looking conventional plastic items with high accuracy.

Compostable and biodegradable plastics are growing in popularity but their environmental credentials need to be more fully assessed to determine how they can be a part of the solution to the plastic waste crisis. We present results and analysis on home compostable packaging. This type of packaging requires the citizen to be able to correctly identify the packaging as “home compostable,” to have composting facilities at home, and to successfully compost the plastic. Using a citizen science approach, we engaged with 9,701 UK citizens geographically spread across the UK to examine their capability, opportunity, and motivation to do this. Of this cohort 1,648 citizens performed home compost experiments to test the environmental performance of compostable plastics. We report on the type of plastics they tested and their disintegration under real home composting conditions. The results show that the public are confused about the meaning of the labels of compostable and biodegradable plastics. 14% of sampled plastic packaging items tested were certified “industrial compostable” only and 46% had no compostable certification. Of the biodegradable and compostable plastics tested under different home composting conditions, the majority did not fully disintegrate, including 60% of those that were certified “home compostable.” We conclude that for both of these reasons, home composting is not an effective or environmentally beneficial waste processing method for biodegradable or compostable packaging in the UK.

Compostable plastics have great potential environmental benefits, however, the damage caused by incorrect waste management offsets them. This study aims to develop a behavior change intervention aimed at improving compostable plastic disposal. We illustrate application of the Behaviour Change Wheel framework to design an intervention in this context. First, the target behavior was understood by specifying it and identifying potential behavioral influences. Second, behavioral influences were systematically linked to potential intervention strategies and refined by evaluating the likely affordability, practicability, effectiveness, acceptability, equity and potential for side-effects (APEASE criteria) in a UK implementation context. Finally, intervention content and implementation options were selected by systematically selecting specific Behavior Change Techniques and refining them by evaluating them against APEASE criteria. The target behavior was identified as UK citizens disposing of compostable plastic waste in the food waste bin meant for collection by local authorities. Influences on compostable plastic disposal were identified as “psychological capability” (i.e., attention and knowledge), “reflective motivation” (i.e., beliefs around environmental impact of compostable plastics) and “physical opportunity” (i.e., access to appropriate waste management). “Education” and “environmental restructuring” were the intervention types selected. “Communications/marketing”, “guidelines” and “restructuring the physical and social environment” were the policy options selected. Selected behavior change techniques were: instruction on how to perform the behavior, prompts/cues, adding objects to the environment and restructuring the physical environment. The resulting intervention is a disposal instruction label for compostable packaging, comprising of instructions and a logo. The next step is user testing the developed disposal instruction labels in terms of their effect on promoting the desired disposal behavior. The novelty of this study includes the development of an intervention to reduce compostable plastic waste and the explicit, step-by-step documentation of the intervention development process. The scientific significance is therefore both applied and theoretical. When evaluated, our intervention has the potential to yield insights relating to what improves compostable plastic disposal amongst citizens. This, in turn, has key policy implications for product and package labeling. By openly documenting our method, we demonstrate a systematic and transparent approach to intervention design, providing an adaptable template and model for others.

Prosthetic limbs (and orthotic devices) have been used as a paradigm for the treatment and rehabilitation of neuropathic pain, such as phantom limb pain. Long-term adoption of the devices for the continued use in rehabilitation remains low in part due to reduced embodiment and the high cognitive load associated with controlling the device. Previous research has shown that incorporating sensory feedback in prostheses can provide proprioceptive information, increase control and manipulation of objects, and improve embodiment. However, feedback experienced by the user varies daily and requires constant parameter adjustments to maintain accurate and intuitive sensory perception, further preventing long term adoption. Work therefore needs to be explored that correlate feedback modalities to perception of tactile information, such as texture and pressure. The work presented in this paper begins to explore this by utilizing a deep-learning algorithm to classify the dissipation of vibration artefacts found in the EMG signals of able-bodied individuals to specific texture patterns. Four texture patterns were applied to 7 participants using two vibration motors and repeated 3 times. In post processing, a RNN network identified the artefact features along equidistantly spaced EMG electrodes and correctly classified unseen data from each participant.

Elastomeric liners are commonly worn between the prosthetic socket and the limb. A number of improvements to the state of the art of liner technology are required to address outstanding problems. A liner that conforms to the residuum more accurately, may improve the skin health at the stump-socket interface. Previous work has shown that for effective thermal management of the socket environment, an active heat removal system is required, yet this is not available. Volume tracking of the stump could be used as a diagnostic tool for looking at the changes that occur across the day for all users, which depend on activity level, position, and the interaction forces of the prosthetic socket with the limb. We believe that it would be advantageous to embed these devices into a smart liner, which could be replaced and repaired more easily than the highly costly and labour-intensive custom-made socket. This paper presents the work to develop these capabilities in soft material technology, with: the development of a printable nanocomposite stretch sensor system; a low-cost digital method for casting bespoke prosthetic liners; a liner with an embedded stretch sensor for growth / volume tracking; a model liner with an embedded active cooling system.

From a monarch mystery unlocked with the help of Indigenous people to an environmental disaster averted by a chemist who was not afraid of a fight, this year's finalists for the AAAS/Subaru (SB&F) Prize for Excellence in Science Books highlight how diverse perspectives, grit, and a healthy dose of hope are essential to the effective practice of science. Read on for reviews of the finalists written by the staff of the Science family of journals, with help from a few friends.

From multiple studies conducted through the FCDO AT2030 Programme, as well as key literature, we examine whether Assistive Technology (AT) provision models could look towards more sustainable approaches, and by doing this benefit not only the environment, but also address the problems that the current provision systems have. We show the intrinsic links between disability inclusion and the climate crisis, and the particular vulnerability people with disabilities face in its wake. In particular, we discuss how localised circular models of production could be beneficial, facilitating context driven solutions and much needed service elements such as repair and maintenance. Key discussion areas include systems approaches, digital fabrication, repair and reuse, and material recovery. Finally, we look at what needs be done in order to enable these approaches to be implemented. In conclusion, we find that there are distinct parallels between what AT provision models require to improve equitable reliable access, and strategies that could reduce environmental impact and bring economic benefit to local communities. This could allow future AT ecosystems to be key demonstrators of circular models, however further exploration of these ideas is required to make sense of the correct next steps. What is key in all respects, moving forward, is aligning AT provision with sustainability interventions.

Cell migration is hypothesized to involve a cycle of behaviours beginning with leading edge extension. However, recent evidence suggests that the leading edge may be dispensable for migration, raising the question of what actually controls cell directionality. Here, we exploit the embryonic migration of Drosophila macrophages to bridge the different temporal scales of the behaviours controlling motility. This approach reveals that edge fluctuations during random motility are not persistent and are weakly correlated with motion. In contrast, flow of the actin network behind the leading edge is highly persistent. Quantification of actin flow structure during migration reveals a stable organization and asymmetry in the cell-wide flowfield that strongly correlates with cell directionality. This organization is regulated by a gradient of actin network compression and destruction, which is controlled by myosin contraction and cofilin-mediated disassembly. It is this stable actin-flow polarity, which integrates rapid fluctuations of the leading edge, that controls inherent cellular persistence.

The ever-growing urban population faces challenges of ageing infrastructure. The process for renewing the infrastructure is costly, and current practices for maintaining and repairing are often ineffective and labour intensive. Road networks, for instance, which act as the arteries of cities, suffer from reoccurring potholes (in the UK, a pothole is filled every 21 s). A more effective way of maintaining road networks is through a proactive approach, where condition assessment and intervention are conducted throughout the asset life cycle. However, there are barriers to a proactive approach, including budget constraints and the lack of effective technology for early defect detection (followed by a cheap yet effective repair). This paper puts forward an automated system, currently in development, based on cutting-edge robotic technologies to address these barriers and help achieve an effective proactive infrastructure maintenance and repair system. Technologies developed include automated condition assessment measures to detect road defects and repair technologies using a novel three-dimensional (3D) printing method to seal road cracks and potholes. Sealing small cracks by using 3D printing techniques has shown promising results by achieving superior mechanical properties.

Chainmail fabrics manufactured by selective laser sintering 3D printing have been magnetically functionalized to create a lightweight, 4D printed, actuating fabric. The post-processing method involves submerging the porous prints in commercial ferrofluid (oil-based magnetic liquid), followed by drying under heat. The actuation of the chainmail has been simulated using a rigid multi-body physics engine, and qualitatively matches experiment. Such magnetically actuating fabrics have potential to make thin, lightweight and comfortable wearable assistive devices.

Shape changing materials create a unique opportunity to design reconfigurable tactile display actuators. In this paper, we present a method that transforms a single thin monolithic sheet of Nitinol into a passive reconfigurable tactile pixel array at Braille resolution. We have designed a 27x27 tactile pixel array in which each pixel can be selectively actuated with an external source of heat. The pixels rise 0.4mm vertically with a peak blocked force of 0.28kg and have an average blocked force of 0.23kg at room temperature. After cooling, the pixels can be mechanically reconfigured back to their flat state for repeatable actuation. We demonstrate this actuator’s interactive capabilities through a novel erasable tactile drawing interface.

Due to the COVID-19 pandemic, the UK government has mandated the use of face masks in various public settings and recommends the use of reusable masks to combat shortages of medically graded single-use masks in healthcare. To assist decision-making on the choice of masks for future pandemics, where shortages may not be a contributing factor, the UCL Plastic Waste Innovation Hub has carried out a multidisciplinary comparison between single-use and reusable masks based on their anatomy, standalone effectiveness, behavioural considerations, environmental impacts and costs. Although current single-use masks have a higher standalone effectiveness against bacteria and viruses, studies show that reusable masks have adequate performance in slowing infection rates of respiratory viruses. Material Flow Analysis, Life Cycle Assessment and cost comparison show that reusable masks have a lower environmental and economic impact than single-use masks. If every person in the UK uses one single-use mask each day for a year, it will create a total of 124,000 tonnes of waste, 66,000 tonnes of which would be unrecyclable contaminated plastic waste (the masks), with the rest being the recyclable packaging typically used for transportation and distribution of masks.Using reusable masks creates >85% less waste, generates 3.5 times lower impact on climate change and incurs 3.7 times lower costs. Further behavioural research is necessary to understand the extent and current practices of mask use; and how these practices affect mask effectiveness in reducing infection rates. Wearing single-use masks may be preferred over reusable masks due to perceptions of increased hygiene and convenience. Understanding behaviour towards the regular machine-washing of reusable masks for their effective reuse is key to maximise their public health benefits and minimise environmental and economic costs.

Background: An estimated 2.5-5 billion single-use coffee cups are disposed of annually in the UK, most of which consist of paper with a plastic lining. Due to the difficulty of recycling poly-coated material, most of these cups end up incinerated or put in landfills. As drinking (take-away) hot beverages is a behaviour, behaviour change interventions are necessary to reduce the environmental impacts of single-use coffee cup waste. Basing the design of interventions on a theoretical understanding of behaviour increases the transparency of the development process, the likelihood that the desired changes in behaviour will occur and the potential to synthesise findings across studies. Aim: The present paper presents a methodology for identifying influences on using single-use use and reusable cups as a basis for designing intervention strategies. Method and application: Two behaviour change frameworks: The Theoretical Domains Framework and the Capability-Opportunity-Motivation-Behaviour model of behaviour, were used to develop an online survey and follow-up interviews. Research findings can inform the selection of intervention strategies using a third framework, the Behaviour Change Wheel. The application of the methodology is illustrated in relation to understanding barriers and enablers to single-use and reusable cup use across the setting of a London university campus. Conclusions: We have developed a detailed method for identifying behavioural influences relevant to pro-environmental behaviours, together with practical guidance for each step and a worked example. Benefits of this work include it providing guidance on developing study materials and collecting and analysing data. We offer this methodology to the intervention development and implementation community to assist in the application of behaviour change theory to interventions.

A new technique for additive manufacture of composites has been developed, capable of 3D printing different compositions of asphalt with magnetic nanoparticles. Variation of the material feed ratio combined with precise fabrication geometries offers a simple avenue to functional grading of the materials properties. The integration of nanomaterials into milli-scale particle feedstock offers a new modality of nanomaterials handling, mixing and processing. We use X-ray computed tomography to quantify the functional grading and magnetic hyperthermia experiments to illustrate the functionalisation of the 3D printed composites. The technique is general and can be applied to a wide variety of materials; it has immediate application for repairing cracks in asphalt roads to modulate their properties and improve the lifetime of the repair.

We resort to non-linear viscoelasticity to develop a truss element able to model reversible softening in lung epithelial tissues undergoing transient stretch. Such a Maxwell truss element is built by resorting to a three-noded element whose mid-node is kinematically constrained to remain on the line connecting the end-nodes. The whole mechanical system undergoes an additive decomposition of the strains along the truss direction where the total contribution of the mid-node is accounted for by using a null-space projection and static condensation techniques. Assembling of such line-elements in 3D networks allows us to model extended regions of living tissues as well as their anisotropies.

A new finite element model is proposed for the analysis of the mechanical aspects of morphogenesis and tested on the biologically well studied gastrulation phenomenon, in particular ventral furrow invagination of the Drosophila melanogaster embryo. A set of mechanisms are introduced in the numerical model, which lead to the observed deformed shapes. We split the total deformation into two parts: an imposed active deformation, and an elastic deformation superimposed onto the latter. The active deformation simulates the effects of apical constriction and apico-basal elongation. These mechanisms are associated with known gene expressions and so in this way we attempt to bridge the well explored signalling pathways, and their associated phenotypes in a mechanical model. While the former have been studied in depth, much less can be said about the forces they produce and the mechanisms involved. From the numerical results, we are able to test different plausible mechanical hypotheses that generate the necessary folding observed in the invagination process. In particular, we conclude that only certain ratios between both modes (apical constriction and apico-basal elongation) can successfully reproduce the invagination process. The model also supports the idea that this invagination requires the contribution of several mechanisms, and that their redundancy provides the necessary robustness.

The paper describes work to design, build and test an asphalt 3D printer. The main difficulty encountered is that asphalt behaves as a non-Newtonian liquid when moving through the extruder. Thus, the rheology and pressure in relation to set temperature and other operational parameters showed highly non-linear behaviour and made control of the extrusion process difficult. This difficulty was overcome through an innovative extruder design enabling 3D printing of asphalt at a variety of temperatures and process conditions. We demonstrate the ability to extrude asphalt into complex geometries, and to repair cracks. The mechanical properties of 3D printed asphalt are compared with cast asphalt over a range of process conditions. The 3D printed asphalt has different properties from cast, being significantly more ductile under a defined range of process conditions. In particular, the enhanced mechanical properties are a function of process temperature and we believe this is due to microstructural changes in the asphalt resulting in crack-bridging fibres that increase toughness. The advantages and opportunities of using 3D printed asphalt to repair cracks and potholes in roads are discussed. Keywords: Asphalt, Bitumen, 3D printing, Additive manufacture, Repair, Toughness

Background: Early failure of uncemented femoral stems associated with incorrect sizing is a known postoperative complication. Surgeons are often faced with the question of whether an uncemented stem of adequate stability or a larger-sized stem should be implanted, especially when the proximal femoral cancellous bone is adequate. The biomechanical effect of sub-optimal stem sizing in the femur remains unclear. This study investigated the mechanical behaviour of two sequential sized uncemented stems of the same type. Methods: Six laboratory models of synthetic non-osteoporotic femora were randomly divided into two groups and implanted with either a nominal or oversized uncemented hydroxyapatite-coated nonporous titanium collarless stem. Stiffness, uniaxial strain, and pattern of strain distribution were measured under an anatomical one-legged stance. Results: Oversized stems demonstrated a higher overall stiffness compared to nominal; however, this was not statistically significant. The nominal stem showed a higher strain in the neck and the proximal medial diaphyseal region. The oversized stem showed higher strains in the distal region around the implant tip. Conclusion: Opting to use a larger stem may potentially increase primary stability, thus allowing safer early mobility. However, higher stiffness may lead to stress shielding, bone loss, and thigh pain in the long term. In addition, strains in the diaphysis and the tip of the stem may predispose to periprosthetic fractures, especially in osteoporotic bones, making this a relatable aspect for users and biomechanical loading. Given the wide range of complex factors that need to be considered when choosing stem size in uncemented THA surgery, this study’s results should be interpreted cautiously.

Restoration of forested land represents an effective strategy to achieve net-zero target emissions by enhancing the removal of greenhouse gases from the atmosphere. The most common afforestation strategy envisages planting seedlings, which are germinated and grown to the desired age at tree nurseries, with plastic shelters to increase growth and survival of trees. This article presents a comprehensive Life Cycle Assessment (LCA) study that compares the environmental performance of current and prospective scenarios for shelter-aided seedling planting compared with a base case where shelters are not employed. The study focuses on the UK, but results and conclusions are valid for other temperate oceanic regions. The scenarios investigated are a combination of different shelters materials and end-of-life (EoL) strategies. Our analysis demonstrates that (i) planting seedling without shelters is the most preferable option across most environmental impact categories (including Climate Change), and in terms of weighted results, (ii) polypropylene shelters are preferable to bio-based alternatives, including polylactic acid-starch blends and bio-polypropylene, (iii) recycling is the most environmentally advantageous EoL treatment. Our study also showed that that the carbon emissions of the scenarios investigated are negligible when compared to the amount of carbon sequestered by a tree in 25 years.

Bespoke force sensors made with active polymer composites are inexpensive, thin and flexible, hence popular in wearable electronics, however their wider application is limited due to the lack of literature studying their voltage response related errors. We present the voltage response characterization of bespoke force sensors made with an active polymer composite, silver coated fabric, stainless steel thread, and silver epoxy. Characterization of the effects of static and dynamic loading was completed with a mechanical testing machine. Static tests consisted of loading and unloading at 0.01, 0.1, 0.5 and 1 N/s, and drift tests for 120 minutes up to 10 N every 1 N. Dynamic tests consisted of a sinusoidal load of 5 N ±1 N applied at 0.05, 0.1, and 0.5 Hz for 60 min. The force-voltage relationships were modeled using an exponential function. Maximum mean drift error was observed when applying different static loads for 120 minutes each. Drift error is minimal at 5 s (

Soft material robots offer a number of advantages over traditional rigid robots in applications including human-robot interaction, rehabilitation and surgery. These robots can navigate around obstacles, elongate, squeeze through narrow openings or be squeezed - and they are considered to be inherently safe. The ability to stiffen compliant soft actuators has been achieved by embedding various mechanisms that are generally decoupled from the actuation principle. Miniaturisation becomes challenging due to space limitations which can in turn result in diminution of stiffening effects. Here, we propose to hydraulically actuate soft manipulators with low-melting-point material and, at the same time, be able to switch between a soft and stiff state. Instead of allocating an additional stiffening chamber within the soft robot, one chamber only is used for actuation and stiffening. Low Melting Point Alloy is integrated into the actuation chamber of a single-compartment soft robotic manipulator and the interfaced robotic syringe pump. Temperature change is enabled through embedded nichrome wires. Our experimental results show higher stiffness factors, from 9–12 opposing the motion of curvature, than those previously found for jamming mechanisms incorporated in separate additional chambers, in the range of 2–8 for the same motion.

There is a growing need for flexible stretch sensors to monitor real time stress and strain in wearable technology. However, developing stretch sensors with linear responses is difficult due to viscoelastic and strain rate dependent effects. Instead of trying to engineer the perfect linear sensor we take a deep learning approach which can cope with non-linearity and yet still deliver reliable results. We present a general method for calibrating highly hysteretic resistive stretch sensors. We show results for textile and elastomeric stretch sensors however we believe the method is directly applicable to any physical choice of sensor material and fabrication, and easily adaptable to other sensing methods, such as those based on capacitance. Our algorithm does not require any a priori knowledge of the physical attributes or geometry of the sensor to be calibrated, which is a key advantage as stretchable sensors are generally applicable to highly complex geometries with integrated electronics requiring bespoke manufacture. The method involves three-stages. The first stage requires a calibration step in which the strain of the sensor material is measured using a webcam while the electrical response is measured via a set of arduino-based electronics. During this data collection stage, the strain is applied manually by pulling the sensor over a range of strains and strain rates corresponding to the realistic in-use strain and strain rates. The correlated data between electrical resistance and measured strain and strain rate are stored. In the second stage the data is passed to a Long Short Term Memory Neural Network (LSTM) which is trained using part of the data set. The ability of the LSTM to predict the strain state given a stream of unseen electrical resistance data is then assessed and the maximum errors established. In the third stage the sensor is removed from the webcam calibration set-up and embedded in the wearable application where the live stream of electrical resistance is the only measure of strain-this corresponds to the proposed use case. Highly accurate stretch topology mapping is achieved for the three commercially available flexible sensor materials tested.

Without our stuff, we would be naked, vulnerable, and, arguably, not very human. The question of how much of our humanity is due to this material wealth and how our cultural values are baked into the materials we create is the subject of Ainissa Ramirez9s fascinating new treatise, The Alchemy of Us.

Periprosthetic femoral fracture is a severe complication of total hip arthroplasty. A previous review published in 2011 summarised the biomechanical studies regarding periprosthetic femoral fracture and its fixation techniques. Since then, there have been several commercially available fracture plates designed specifically for the treatment of these fractures. However, several clinical studies still report failure of fixation treatments used for these fractures.The current literature on biomechanical models of periprosthetic femoral fracture fixation since 2010 to present is reviewed. The methodologies involved in the experimental and computational studies of periprosthetic femoral fracture fixation are described and compared with particular focus on the recent developments.Several issues raised in the previous review paper have been addressed by current studies; such as validating computational results with experimental data. Current experimental studies are more sophisticated in design. Computational studies have been useful in studying fixation methods or conditions (such as bone healing) that are difficult to study in vivo or in vitro. However, a few issues still remain and are highlighted.The increased use of computational studies in investigating periprosthetic femoral fracture fixation techniques has proven valuable. Existing protocols for testing periprosthetic femoral fracture fixation need to be standardised in order to make more direct and conclusive comparisons between studies. A consensus on the 'optimum' treatment method for periprosthetic femoral fracture fixation needs to be achieved.

Epithelial monolayers are one-cell thick tissue sheets that separate internal and external environments. As part of their function, they withstand extrinsic mechanical stresses applied at high strain rate. However, little is known about how monolayers respond to mechanical deformations. In stress relaxation tests, monolayers respond in a biphasic manner and stress dissipation is accompanied by an increase in monolayer resting length, pointing to active remodelling of cell architecture during relaxation. Consistent with this, actomyosin remodels at a rate commensurate with mechanical relaxation and governs the rate of monolayer stress relaxation – as in single cells. By contrast, junctional complexes and intermediate filaments form stable connections between cells, enabling monolayers to behave rheologically as single cells. Together, these data show actomyosin cytoskeletal dynamics govern the rheological properties of monolayers by enabling active, ATP-dependent changes in the resting length. These findings have far-reaching consequences for our understanding of developmental morphogenesis and tissue response to mechanical stress.

An electrohydrodynamic printer designed and constructed in our laboratory was used to fabricate polycaprolactone nasal septal scaffolds. Three different polymer concentrations (15 wt.%, 18 wt.% and 23 wt.%) were used. The generated scaffolds, each with a unique architecture, were evaluated using PeakForce Quantitative Nanomechanical Mapping (QNM) Atomic Force Microscopy (AFM) to measure Young's modulus using the Dejaguin–Müller–Toporov (DMT) model. In addition, this allowed estimation of adhesion forces, deformation and dissipation energy of the scaffolds. The degree of crystallinity and purity of the polymer in the scaffolds were characterized by differential scanning calorimetry and Fourier transform infrared spectroscopy. Keywords: Electrohydrodynamic, Direct-write, Polymer, Polycaprolactone, Scaffold, Nasal, Septal

Designers increasingly have the opportunity to influence the development of materials as they emerge from the laboratory. In order for this to be successful, designers need to be able to communicate effectively with materials scientists so that materials can be developed with desired functionalities and properties. This paper reviews evidence in favour of using isomorphic sets of material stimuli as tools to bridge the disciplinary gap between designers and materials scientists. We show how these isomorphic sets and their accompanying experiments can be used to translate between the two communities, and to systematically explore the relationship between the technical attributes of materials and subjective experiences of their sound, taste and feel. This paper also explores the limitations of psychophysical approaches and other quantitative techniques for elucidating material experience, and suggests new possibilities for interdisciplinary collaborations that draw on ethnographic approaches. Keywords: Design tools, Design-driven materials innovation, Materials selection, Interdisciplinary dialogue, Technical properties, Sensory perception, Aesthetics, Material experiences, Psychophysics, Ethnography, Haptic encounter

Background and aim: Thermal discomfort often affects prosthesis wearers and could be addressed by increasing liner thermal \ud conductivity. This note explores a liner made from thermally conductive silicone and two additional alternative liner designs.\ud Technique: Thermally conductive silicone was used to create a conductive liner and a hybrid liner. Additionally, one with open elements was made. These were compared with a plain silicone liner and a no liner scenario. Scaled down liner prototypes were used due to the high-cost of the thermally conductive silicone. Temperature decay profiles were \ud collected by attaching thermistors to a heated liner phantom and used to evaluate scenarios.\ud Discussion: No scenario performed much better than the plain silicone liner. Implementation of passive solutions may be easier, but alternative liner materials are unlikely to affect dissipation enough to address thermal discomfort. Based on this work, future research efforts may be better spent developing active thermal discomfort solutions.\ud Clinical relevance Thermal discomfort can increase the probability of skin damage, reduce prosthesis satisfaction and, \ud ultimately, the quality of life. The prosthesis-wearing experience could be improved if thermal discomfort can be \ud addressed by technological improvements.

This study investigates the effect of print head design on the electrohydrodynamic printed resolution of silk fibroin. Needles with large orifices measuring at 800 μm were used to build five different print heads. The print heads were manufactured, tested, and optimized using four different silk fibroin solution concentrations of 10 wt.%, 15 wt.%, 20 wt.%, and 22 wt.% at applied voltages that ranged from 10 to 20 kV with two different flow rates of 1.5 μl/min and 2.0 μl/min. Each print head design behaved in a unique manner in terms of printed line characteristics as the flow rate, voltage and concentration were varied. The highest printed resolution of the order of 1 μm was achieved using the pinhole reservoir print head. Possible explanations for each of the observed behaviors and design criteria for future print heads are discussed.

A new wearable device called the 'Ubi-Sleeve' is currently being developed that enables prosthesis wearers and other stakeholders to review temperature, humidity and prosthesis slippage behavior during everyday prosthesis wear. A combination of custom 3D printed strain sensors and off the shelf temperature and humidity sensors will be integrated into an unobtrusive sleeve to create a device that enables a deeper level of understanding of heat and sweat issues. To create the device, a series of experiments are in progress that will quantify changes in heat, humidity and slippage that negatively affect the prosthesis experience. Interviews and focus groups are also being conducted to gain a deeper understanding of the human side of prosthesis wear and to also ensure that data are presented in a way that is effective, useful and easy to understand.

The origin of the strong [100] fibre texture observed after the secondary recrystallisation of ODS MA754 has been investigated by FEG-SEM EBSP. The as-extruded material had a weak [100]-[111] fibre texture. It has been found that the as-received grain size is in fact bimodal, in contrast to the observed uniformity of initial grain size reported in other MA superalloys. The present SEM study has revealed occasional grains (embryos) that possess a 10-fold size advantage over the matrix grains. The orientation of these embryos includes that of the final texture, and their average misorientations with respect to the matrix grains have been calculated. The growing grains cannot be described in terms of a specific misorientation with the matrix, and it is concluded that the triggering of the [100] embryos must have its origin in the local (meso-) texture reducing the local solute pinning

This paper examines whether the physical properties of materials can be useful predictors of psychophysical properties of materials. In this study psychophysical methods were employed to study the link between the measured surface roughness, elastic modulus and thermal effusivity and the perceptual qualities of roughness, hardness and coldness, for a diverse set of materials (woods, polymers and metals). A strong positive correlation was found between the physical and the psychophysical properties of materials that determine touch perception. Furthermore, by analysing the data in which vision of the sample was controlled, it was found that in some cases there is a shift in touch perception between the sighted and unsighted condition that affects polymer samples most strongly.

Background Periprosthetic femoral fracture is a severe complication of total hip arthroplasty. A previous review published in 2011 summarised the biomechanical studies regarding periprosthetic femoral fracture and its fixation techniques. Since then, there have been several commercially available fracture plates designed specifically for the treatment of these fractures. However, several clinical studies still report failure of fixation treatments used for these fractures. Methods The current literature on biomechanical models of periprosthetic femoral fracture fixation since 2010 to present is reviewed. The methodologies involved in the experimental and computational studies of periprosthetic femoral fracture fixation are described and compared with particular focus on the recent developments. Findings Several issues raised in the previous review paper have been addressed by current studies; such as validating computational results with experimental data. Current experimental studies are more sophisticated in design. Computational studies have been useful in studying fixation methods or conditions (such as bone healing) that are difficult to study in vivo or in vitro. However, a few issues still remain and are highlighted. Interpretation The increased use of computational studies in investigating periprosthetic femoral fracture fixation techniques has proven valuable. Existing protocols for testing periprosthetic femoral fracture fixation need to be standardised in order to make more direct and conclusive comparisons between studies. A consensus on the ‘optimum’ treatment method for periprosthetic femoral fracture fixation needs to be achieved.

Lateral inhibition provides the basis for a self-organizing patterning system in which distinct cell states emerge from an otherwise uniform field of cells. The development of the microchaete bristle pattern on the notum of the fruitfly,Drosophila melanogaster, has long served as a popular model of this process. We recently showed that this bristle pattern depends upon a population of dynamic, basal actin-based filopodia, which span multiple cell diameters. These protrusions establish transient signalling contacts between non-neighbouring cells, generating a type of structured noise that helps to yield a well-ordered and spaced pattern of bristles. Here, we develop a general model of protrusion-based patterning to analyse the role of noise in this process. Using a simple asynchronous cellular automata rule-based model we show that this type of structured noise drives the gradual refinement of lateral inhibition-mediated patterning, as the system moves towards a stable configuration in which cells expressing the inhibitory signal are near-optimally packed. By analysing the effects of introducing thresholds required for signal detection in this model of lateral inhibition, our study shows how filopodia-mediated cell–cell communication can generate complex patterns of spots and stripes, which, in the presence of signalling noise, align themselves across a patterning field. Thus, intermittent protrusion-based signalling has the potential to yield robust self-organizing tissue-wide patterns without the need to invoke diffusion-mediated signalling.

SummaryThe organization of bristles on the Drosophila notum has long served as a popular model of robust tissue patterning. During this process, membrane-tethered Delta activates intracellular Notch signaling in neighboring epithelial cells, which inhibits Delta expression. This induces lateral inhibition, yielding a pattern in which each Delta-expressing mechanosensory organ precursor cell in the epithelium is surrounded on all sides by cells with active Notch signaling. Here, we show that conventional models of Delta-Notch signaling cannot account for bristle spacing or the gradual refinement of this pattern. Instead, the pattern refinement we observe using live imaging is dependent upon dynamic, basal actin-based filopodia and can be quantitatively reproduced by simulations of lateral inhibition incorporating Delta-Notch signaling by transient filopodial contacts between nonneighboring cells. Significantly, the intermittent signaling induced by these filopodial dynamics generates a type of structured noise that is uniquely suited to the generation of well-ordered, tissue-wide epithelial patterns.

A set of equilibrium equations is derived for the stress-controlled shape change of cells due to the remodelling and growth of their internal architecture. The approach involves the decomposition of the deformation gradient into an active and a passive component; the former is allowed to include a growth process, while the latter is assumed to be hyperelastic and mass-preserving. The two components are coupled with a control function that provides the required feedback mechanism. The balance equations for general continua are derived and, using a variational approach, we deduce the equilibrium equations and study the effects of the control function on these equations. The results are applied to a truss system whose function is to simulate the cytoskeletal network constituted by myosin microfilaments and microtubules, which are found experimentally to control shape change in cells. Special attention is paid to the conditions that a thermodynamically consistent formulation should satisfy. The model is used to simulate the multicellular shape changes observed during ventral furrow invagination of the Drosophila melanogaster embryo. The results confirm that ventral furrow invagination can be achieved through stress control alone, without the need for other regulatory or signalling mechanisms. The model also reveals that the yolk plays a distinct role in the process, which is different to its role during invagination with externally imposed strains. In stress control, the incompressibility constraint of the yolk leads, via feedback, to the generation of a pressure in the ventral zone of the epithelium that eventually eases its rise and internalisation.

The authors have performed a systematic set of experiments and corresponding computer simulations to investigate the microtexture evolution of non-oriented silicon steels. The experiments show that similar behaviour is observed during annealing at 800 and 900°C, grain growth occurs and the 〈110〉 fibre microtexture volume fraction decreases rapidly. The authors have imported the microstructures and grain orientations directly from the electron backscattered diffraction (EBSD) system into a Monte Carlo Potts model and used these to simulate the grain growth of the system. These simulations show that neither the residual size distributions of different microtexture fibres nor the presence of highly mobile high energy boundaries are responsible for the grain growth and 〈110〉 fibre microtexture decrease.

A Monte Carlo Potts model, including anisotropic boundary energies and mobilities, has been used to investigate cube texture evolution. The work is motivated by the post-recrystallization grain growth seen during annealing of highly cold-rolled nickel sheets. It is observed that during such grain growth the cube texture fraction increases from approx. 50% to more than 95%. Electron back-scatter diffraction orientation measurements of fully recrystallized samples have been used to provide starting microstructures for simulations examining the effect of the texture tightness on the development of the cube texture during grain growth. The texture evolution of a single texture component with an initial average size advantage is controlled predominantly by this size advantage once the initial texture spread of this component falls below some value. An additional set of simulations was also carried out to examine grain growth in systems with a quasi-binary texture. The simulations were used to examine cases of grain growth in where one component has a larger average grain size, but where there is still a significant overlap in the grain-size distribution of each component. The initial microstructures were constructed to give different fractions of each texture component, with a given value of both the mean size and the texture spread of each component. The simulations suggest that for such systems there is a well defined range of conditions for which a single texture component can grow to dominate the final texture.

The generation of initial microstructures for use in the investigation of grain growth in quasi-binary textured systems (i.e. one texture component plus an otherwise random texture) is described. For investigations of the effect of texture tightness the microstructural morphology (grain shapes/sizes) can be taken from electron back-scatter pattern orientation mapping data. The procedure consists of first aligning the data to an ideal orientation and then adjusting selectively those orientations belonging to the texture component of interest. For investigation of the effect of texture fraction and average grain size ratio, a method is described for constructing microstructures with different combinations of these parameters, by making use of a surface energy term in the Potts model Hamiltonian.

In ancient societies, there was no arts/science split. The development of materials was driven both by aesthetic and technological goals. At the end of the 19thcentury, things changed dramatically. Scientists started being able to analyze composition, detect structure, and make a link between structure and properties. The subsequent 20th-century revolution in new materials changed almost all aspects of human activity. However, it was not without serious side-effects, the first of which has been that the materials science community has willingly marginalized itself. The second is the eradication of interest in the sensual and aesthetic properties of materials, and thus the banishment of the creative urges that arrive via the senses. This paper discusses these issues, and suggests that collaboration with the materials arts community offers exciting new challenges and could create an intellectual community that is not just more culturally and ethically aware, but also nurtures more innovative science.

We compare the ability of three types of microstructural model to simulate particle pinning by performing simulations using the front tracking model, the phase field model and the Monte Carlo Potts model. The same three-dimensional test geometries are simulated using each method and compared with theory. The pinning force acting on the migrating curved grain boundary is calculated and compared with theoretical predictions for each model. All three simulation methods correctly capture the physics of pinning and the simulations confirm that for static spherically symmetric boundaries, a catenoid shape is produced during particle bypass, as predicted by theory. The presence of triple lines and quadruple points changes the equilibrium boundary shapes; this does not affect the pinning forces greatly, whereas the pinning force is a strong function of the particle shape.

The article describes work to bring together the topics of evolutionary computing and stereology and asks the reader to judge whether such an approach can be genuinely useful or just represents a clever application of computer science. The problem we address is that of constructing three-dimensional (3-D) microstructures from two-dimensional (2-D) micrographs. Our solution is a computer program called MicroConstructor that evolves 3-D discrete computer microstructures, which are statistically equivalent to the 2-D inputs in terms of the microstructural variables of interest. The core of Micro-Constructor is a genetic algorithm that evolves the 3-D microstructure so that its stereological parameters match the 2-D data. MicroConstructor uses a general method of pattern construction, the EmbryoCA, that does not require intervention from the user and is highly evolvable. This article presents initial results from successful experiments to evolve 3-D two-phase microstructures from 2-D input microstructures. The advantages and disadvantages of the method are discussed, and we conclude that the method, though delightfully elegant and full of potential, has yet to prove itself capable of constructing 3-D microstructures that would interest experimentalists and computer modelers.

A Monte Carlo Potts model has been used to investigate cube-texture strengthening during grain growth in rolled high-purity Ni-tapes. The initial conditions for the simulations have been taken from electron back-scatter pattern (EBSP) orientation maps of already fully recrystallized samples. Experimentally, grain growth leads to an increase in the cube volume fraction to >95% , accompanied by an approximately ten-fold increase in the grain size. High cube volume fractions can be predicted under a number of conditions, though a small surface energy advantage of just 2% for cube-oriented grains is required to match the texture strengthening to the grain size change. An additional issue of interest is the influence on the grain growth of the large area-fraction of twin boundaries in the fully recrystallized condition. The presence of boundaries with low energy has a strong influence on the simulated microstructural evolution.

A kinetic, three-dimensional Monte Carlo model for simulating grain growth in the presence of mobile pores is presented. The model was used to study grain growth and pore migration by surface diffusion in an idealized geometry that ensures constant driving force for grain growth. The driving forces, pore size, and pore mobilities were varied to study their effects on grain-boundary mobility and grain growth. The simulations captured a variety of complex behaviors, including reduced grain-boundary velocity due to pore drag that has been predicted by analytical theories. The model is capable of treating far more complex geometries, including polycrystals. We present the capabilities of this model and discuss its limitations.

We describe a general approach to obtaining 3D microstructures as input to computer simulations of materials properties. We introduce a program called MicroConstructor, that takes 2D micrographs and generates 3D discrete computer microstructures which are statistically equivalent in terms of the microstructural variables of interest. The basis of the code is a genetic algorithm that evolves the 3D microstructure so that its stereological parameters match the 2D data. Since this approach is not limited by scale it can be used to generate 3D initial multiscale microstructures. This algorithm will enable microstructural modellers to use as their starting point, experimentally based microstructures without having to acquire 3D information experimentally, a very time consuming and expensive process.