This study introduces a novel methodology for reconstructing full-field three dimensional strain and displacement fields in highly deformable soft solids, leveraging advanced particle tracking techniques. The approach utilises three dimensional displacement data acquired through volumetric particle tracking, specifically the Shake the Box (STB) technique, originally developed for fluid flow analysis, to enable accurate measurement over larger volumes (up to 50 ml) during indenter loading. Displacement vectors are binned to a voxel grid using a Gaussian-weighted scheme, forming the nodes of a hexahedral finite element mesh from which strain fields are computed. Synthetic particle datasets were employed to verify accuracy and quantify error and bias, achieving root mean square errors as low as 1.2% under ideal conditions. Application to experimental datasets demonstrated the method’s ability to capture detailed strain and displacement fields. Comparison with finite element models derived via inverse parameter identification showed strong agreement, confirming the technique’s validity. This integrated method shows significant promise for characterising internal mechanics of soft materials and tissue phantoms where conventional techniques fall short.

Introduction:Microneedles are minimally invasive devices, designed for pain-free drug delivery. Until now, the degree of strain exerted on the skin during microneedle insertion, in comparison to gold standard hypodermic needles, has not been quantified. Methods:This paper presents experimental results from a novel digital image correlation setup to quantify maximum normal strain exerted on a skin-mimicking membrane by hollow silicon microneedles and 25-gauge stainless steel hypodermic needles through contact, deformation, rupture, and device insertion. Results:Findings here have shown 1 × 5 hollow silicon microneedle arrays exert significantly lower maximum normal strain compared to 25-gauge hypodermic needles. There is an average of 75% decrease in the maximum normal strain experienced by the membrane when using microneedle devices in comparison to that of the 25-gauge hypodermic needles. This quantification of strain has been discretised to each individual needle in the microneedle device, allowing for informed design choices for future device iterations. Discussion:These findings suggest the hollow microneedle devices to be a gentler alternative for transdermal applications, potentially improving patient comfort and reducing tissue trauma when compared to the gold standard, traditional 25-gauge hypodermic needle.

In the United Kingdom, aortic valve stenosis is a common heart condition and the cause of morbidity within the elderly population. A common treatment for aortic valve stenosis is replacement with a prosthetic valve, either mechanical or bioprosthetic, each with its own advantages and limitations. Here, the aim is to introduce a workflow for the creation and testing of phantom or prosthetic aortic heart valves to verify computational models and test the effect of valve design parameters on strain profile within the valve leaflet. Three silicone valve geometries were created and inserted into a physiologically representative flow system. High-speed digital image correlation was used to measure displacement and calculate principal strain in a single leaflet. The leaflet free edge was tracked during coaptation while the transvalvular pressure was recorded. A two-stage closing process was established, the primary stage demonstrating geometry and material dependency, and secondary exhibiting solely material dependency. Areas of high principal strain were identified below the coaptation area with peaks near the commissures. This work highlights the importance of further research into the effect of valve parameters on the strain profile within the leaflets to minimise failure risk in new replacement heart valve designs.

This work proposes a modelling framework to analyse flow and pressure distributions throughout the lung of mechanically ventilated COVID-19 patients. The methodology involves: segmentation of the lungs and major airways from patient CT images; a volume filling algorithm that creates a dichotomous airway network in the remaining volume of the lung; an estimate of resistance and compliance within the lung based on Hounsfield unit values from the CT scan; and a computational fluid dynamics model to analyse flow, lung inflation, and pressure throughout the airway network. Mechanically ventilated patients with differing progression and severity of the disease were simulated. The results indicate that the flow distribution within the lung can be significantly affected when there are competing types of lung damage. These competing types are primarily fibrosis-like lung damage that creates higher resistance and lower compliance in that region; and emphysema, which causes a decrease in resistance and increase in compliance. In a patient with severe disease, the model predicted an increase in inflation by 33% in an area affected by emphysema-like conditions. This could increase the risk of alveolar rupture. The framework could readily be adapted to study other respiratory diseases. Early interventions in critical respiratory care could be facilitated through such efficient patient-specific modelling approaches.

Computational models can be at the basis of new powerful technologies for studying and classifying disorders like pre-eclampsia, where it is difficult to distinguish pre-eclamptic patients from non-pre-eclamptic based on pressure when patients have a track record of hypertension. Computational models now enable a detailed analysis of how pregnancy affects the cardiovascular system. Therefore, new non-invasive biomarkers were developed that can aid the classification of pre-eclampsia through the integration of six different measured non-invasive cardiovascular signals. Datasets of 21 pregnant women (no early onset pre-eclampsia, n = 12; early onset pre-eclampsia, n = 9) were used to create personalised cardiovascular models through computational modelling resulting in predictions of blood pressure and flow waveforms in all major and minor vessels of the utero-ovarian system. The analysis performed revealed that the new predictors PPI (pressure pulsatility index) and RI (resistance index) calculated in arcuate and radial/spiral arteries are able to differentiate between the 2 groups of women (t-test scores of p < .001) better than PI (pulsatility index) and RI (Doppler calculated in the uterine artery) for both supervised and unsupervised classification. In conclusion, two novel high-performing biomarkers for the classification of pre-eclampsia have been identified based on blood velocity and pressure predictions in the smaller placental vasculatures where non-invasive measurements are not feasible.

The study of lung mechanics is important to futureproof resilience against potential novel threats to lung health. Medical imaging provides insight to lung function. High-resolution, high-speed synchrotron radiation micro-CT imaging at SPring-8 (Japan) and in situ mechanics were used to characterize healthy and diseased airways. Synchrotron radiation was important to maximize speed and spatial resolution to map the lung architecture clearly. Links between global lung mechanical measurements (pressure-volume) and regional tissue strains were made. Tissue strains were computed from a sequence of tomograms during a respiratory cycle, demonstrating clear differences for the surfactant-free lungs compared to the controls. Poorly ventilated areas were identified within three-dimensional strain maps computed via digital volume correlation. Occluded pathways at low pressures were seen to be opened at higher pressures, augmenting the deformation pathways. The results will aid correlations between microscale and macroscale measurements and the potential impact on patient management guidelines for mechanical ventilation.

This study offers improved safety design guidelines for high explosives (HE), creating impact insensitive geometries, capitalising on the potential for additive layer manufacturing techniques. There are numerous safety concerns when considering energetic materials and HEs, the primary concern, subject of this work, is the risk of unplanned detonation from impact. There are multiple potential causes for unplanned detonation due to impact; one of which is the impact from a high-speed foreign object. Despite this substantial risk, the problem has not been publicly addressed by means of adjusting the design of the charge itself. Therefore, investigations into the internal design of the charge were executed, whereby the inclusion of various sized and shaped voids are assessed, to establish their effect upon the reactivity of the HE. Using computational modelling, allows for numerous designs to be assessed and developed, and the impact sensitivity of the charge to be tested across a range of scenarios. The proposed validated computational model enables designs to be optimised in a safe and efficient manner, reducing the number of physical tests required, and thus minimising time, cost and the environmental impact.

postpartum management of HDP in our unit in comparison to NICE guidelines.Method: We gathered data from maternity records on women who delivered in our unit between 1st January and 31st August 2022 and had a diagnosis of a hypertensive disorder of pregnancy at the time of delivery.Results: We identified 108 women who delivered in our unit within the study period and had a diagnosis of a hypertensive disorder of pregnancy at the time of delivery; this was 3% of our patient population over the period.Of the 108 women identified -26 women had chronic hypertension, 26 women had pregnancy-induced hypertension and 56 women had pre-eclampsia at the time of delivery.75 of the 108 women were on anti-hypertensive treatment in the postpartum period and were discharged on treatment.60 women were discharged on a single agent -48 women were on ß-blocker only, 11 women were on calcium channel blocker (CCB) only and 1 woman was discharged on an angiotensin receptor blocker (ARB).14 women were discharged on dual agent therapy -2 women were on a combination of an ACE-inhibitor and a ß-blocker; 2 women were on an ACE-inhibitor and a CCB, 10 women were on a combination of a CCB and a ß-blocker.In keeping with NICE guidelines -all women on Methyldopa in the antenatal period were switched to other anti-hypertensive agents within 48 h of delivery.13 women re-attended hospital with hypertension following discharge after delivery with 1 woman presenting on 2 separate occasions with poorly controlled hypertension.Women were more than twice as likely to represent back to hospital if they had essential hypertension compared to if they had pre-eclampsia.50% of the repeat presentations with hypertension occurred over 1 week post-delivery.Conclusions: Our audit identified variations in the postnatal management of hypertension within our unit with 12% of our cohort re-attending hospital with hypertension following discharge.We have updated our postnatal management of hypertension guideline in line with NICE guideline recommendations and will re-audit adherence to the guidelines in 1 years' time.

This research investigates the performance of interlaminar hybrid composites as the skins of composite sandwich panels under blast loading with the aim of promoting delamination between dissimilar plies for energy absorption. The deformation of the composite panels was captured using high-speed digital image correlation (DIC). High-speed full-field DIC enables failure to be captured at the moment it occurs across the entire panel. X-ray micro-CT imaging was used to assess the post-blast damage sustained by particular areas of interest from each panel, which were selected based on DIC results. The combination of full-field DIC and detailed X-ray micro-CT scanning enabled a unique comparison of both the global and localised blast resilience of hybrid and conventional composite sandwich panels to be performed. Following a single blast load, the extent of damage to the Hybrid-3B skinned sandwich panel was found to lie between that of GFRP and CFRP skinned sandwich panels. X-ray micro-CT scanning of these panels reveals that there is no continuous damage path through the skin thickness of Hybrid-3B, whereas the GFRP and CFRP panels sustain damage in every ply. Following repeat blast loading, the Hybrid-4 skinned sandwich panel suffered from a front skin crack spanning the length of the panel. Post-blast compressive strength testing reveals that this skin crack and resulting core crack acted as a stress relief, limiting the damage sustained elsewhere in the panel. It was concluded that Hybrid-3B results in a good trade-off between strength and stiffness and is advantageous over conventional CFRP and GFRP panels under a single blast load. Under repeated loading Hybrid-4 offers advantages over Hybrid-3B. Finally, the design of the support structure can significantly aid in blast resilience, and, a holistic approach considering both panels and support should be taken when designing for blast resilience.

Instrumented mouthguards have been used to detect head accelerations and record kinematic data in numerous sports. Each recording requires validation through time-consuming video verification. Classification algorithms have been posed to automatically categorise head acceleration events and spurious events. However, classification algorithms must be designed and/or validated for each combination of sport, sex and mouthguard system. This study provides the first algorithm to classify head acceleration data from exclusively female rugby union players. Mouthguards instrumented with kinematic sensors were given to 25 participants for six competitive rugby union matches in an inter-university league. Across all instrumented players, 214 impacts were recorded from 460 match-minutes. Matches were video recorded to enable retrospective labelling of genuine and spurious events. Four machine learning algorithms were trained on five matches to predict these labels, then tested on the sixth match. Of the four classifiers, the support vector machine achieved the best results, with area under the receiver operator curve (AUROC) and area under the precision recall curve (AUPRC) scores of 0.92 and 0.85 respectively, on the test data. These findings represent an important development for head impact telemetry in female sport, contributing to the safer participation and improving the reliability of head impact data collection within female contact sport.

Nanocelluloses have attracted significant interest in the field of bioprinting, with previous research outlining the value of nanocellulose fibrils and bacterial nanocelluloses for 3D bioprinting tissues such as cartilage. We have recently characterised three distinct structural formulations of pulp-derived nanocelluloses: fibrillar (NFC), crystalline (NCC) and blend (NCB), exhibiting variation in pore geometry and mechanical properties. In light of the characterisation of these three distinct entities, this study investigated whether these structural differences translated to differences in printability, chondrogenicity or biocompatibility for 3D bioprinting anatomical structures with human nasoseptal chondrocytes. Composite nanocellulose-alginate bioinks (75:25 v/v) of NFC, NCC and NCB were produced and tested for print resolution and fidelity. NFC offered superior print resolution whereas NCB demonstrated the best post-printing shape fidelity. Biologically, chondrogenicity was assessed using real time quantitative PCR, dimethylmethylene blue assays and histology. All biomaterials showed an increase in chondrogenic gene expression and extracellular matrix production over 21 days, but this was superior in the NCC bioink. Biocompatibility assessments revealed an increase in cell number and metabolism over 21 days in the NCC and NCB formulations. Nanocellulose augments printability and chondrogenicity of bioinks, of which the NCC and NCB formulations offer the best biological promise for bioprinting cartilage.

Microwave ablation therapy is a hyperthermic treatment for killing cancerous tumours whereby microwave energy is dispersed into a target tissue region. Modelling can provide a prediction for the outcome of ablation, this paper explores changes in size and shape of temperature and Specific absorption rate fields throughout the course of simulated treatment with different probe concepts. Here, an axisymmetric geometry of a probe embedded within a tissue material is created, solving coupled electromagnetic and bioheat equations using the finite element method, utilizing hp discretisation with the NGSolve library. Results show dynamic changes across all metrics, with different responses from different probe concepts. The sleeve probe yielded the most circular specific absorption rate pattern with circularity of 0.81 initially but suffered the largest reduction throughout ablation. Similarly, reflection coefficients differ drastically from their initial values, with the sleeve probe again experiencing the largest change, suggesting that it is the most sensitive the changes in the tissue dielectric properties in these select probe designs. These collective characteristic observations highlight the need to consider dielectric property changes and probe specific responses during the design cycle.

Microwave ablation (MWA) therapy is a hyperthermic treatment for cancerous tumors whereby microwave energy is dispersed into a target tissue region. Absorption of these waves leads to temperature rise through microwave heating with the aim of exposing cancerous cells to a thermal dose sufficient to kill them whilst minimizing the damage to the surrounding healthy tissue. Being able to predict the progression of ablation during a procedure is of high value when designing equipment and planning patient-specific care, as current dosimetry is given in guidelines by the equipment provider. From a modelling standpoint this poses a complex multi-physics problem coupling electro-magnetics and heat conduction. Added to this there are existence of multiple temperature sensitive properties of tissue, as well as physiological processes such as blood perfusion which are heavily influential in the overall temperature profile. Here, we create a two dimensional axisymmetric geometry of a probe embedded within a tissue material, solving the coupled electromagnetic and bioheat equation using the finite element method, utilizing hp discretisation and the NGSolve library. Temperature, electric field strength and energy absorption can be calculated and investigations into the effects of the highly temperature-sensitive properties of tissue on the distribution of temperature throughout ablation.

Accurate and precise analysis of head impact telemetry data is important for development of biomechanical models and methodologies to decrease the risk of traumatic brain injury. Systematic review suggests that much existing data lacks verification. Soft tissue artefact is a common problem that is not frequently addressed. This paper outlines a method of modelling the coupled, non-linear, skull-skin-sensor system. The model is based on a second order underdamped spring mass damper system that incorporates non-linear values to account for the complex dynamic nature of skin. MATLAB was used to simulate the estimated movement of a sensor mounted to the skin relative to measurements collected via a mouthguard sensor. The non-linear elastic and damping models were developed from descriptions in literature. The model assumed a sensor of 8 g, mounted behind the ear. Results were compared to a typical linear system. In small impacts, the linear and non-linear models provided similar accelerations to the skull. However, in large impacts, the acceleration of the sensor was estimated to be 158% greater than the skull acceleration when modelled non-linearly, while a linear model showed only a 0.7% increase. This implies that for small impacts, the nonlinearity of skin-skull dynamics is not an important char-acteristic for modelling. However, in large impacts, the non-linearity of the skin-skull dynamic can lead to drastic over-estimates of skull acceleration when using skin mounted accelerometers. In Brief: The system of an accelerometric sensor mounted to the skin is often used to assess the accelerations experienced by athletes during impacts. By developing a non-linear model of the skull-skin-sensor model, the importance of accounting for the non-linear nature of skin while taking telemetry measurements of head ac-celeration during impact is demonstrated.

The mechanics of breathing is a fascinating and vital process. The lung has complexities and subtle heterogeneities in structure across length scales that influence mechanics and function. This study establishes an experimental pipeline for capturing alveolar deformations during a respiratory cycle using synchrotron radiation micro-computed tomography (SR-micro-CT). Rodent lungs were mechanically ventilated and imaged at various time points during the respiratory cycle. Pressure-Volume (P-V) characteristics were recorded to capture any changes in overall lung mechanical behaviour during the experiment. A sequence of tomograms was collected from the lungs within the intact thoracic cavity. Digital volume correlation (DVC) was used to compute the three-dimensional strain field at the alveolar level from the time sequence of reconstructed tomograms. Regional differences in ventilation were highlighted during the respiratory cycle, relating the local strains within the lung tissue to the global ventilation measurements. Strains locally reached approximately 150% compared to the averaged regional deformations of approximately 80–100%. Redistribution of air within the lungs was observed during cycling. Regions which were relatively poorly ventilated (low deformations compared to its neighbouring region) were deforming more uniformly at later stages of the experiment (consistent with its neighbouring region). Such heterogenous phenomena are common in everyday breathing. In pathological lungs, some of these non-uniformities in deformation behaviour can become exaggerated, leading to poor function or further damage. The technique presented can help characterize the multiscale biomechanical nature of a given pathology to improve patient management strategies, considering both the local and global lung mechanics.

Pulmonary diseases, driven by pollution, industrial farming, vaping, and the infamous COVID-19 pandemic, lead morbidity and mortality rates worldwide. Computational biomechanical models can enhance predictive capabilities to understand fundamental lung physiology; however, such investigations are hindered by the lung’s complex and hierarchical structure, and the lack of mechanical experiments linking the load-bearing organ-level response to local behaviors. In this study we address these impedances by introducing a novel reduced-order surface model of the lung, combining the response of the intricate bronchial network, parenchymal tissue, and visceral pleura. The inverse finite element analysis (IFEA) framework is developed using 3-D digital image correlation (DIC) from experimentally measured non-contact strains and displacements from an ex-vivo porcine lung specimen for the first time. A custom-designed inflation device is employed to uniquely correlate the multiscale classical pressure-volume bulk breathing measures to local-level deformation topologies and principal expansion directions. Optimal material parameters are found by minimizing the error between experimental and simulation-based lung surface displacement values, using both classes of gradient-based and gradient-free optimization algorithms and by developing an adjoint formulation for efficiency. The heterogeneous and anisotropic characteristics of pulmonary breathing are represented using various hyperelastic continuum formulations to divulge compound material parameters and evaluate the best performing model. While accounting for tissue anisotropy with fibers assumed along medial-lateral direction did not benefit model calibration, allowing for regional material heterogeneity enabled accurate reconstruction of lung deformations when compared to the homogeneous model. The proof-of-concept framework established here can be readily applied to investigate the impact of assorted organ-level ventilation strategies on local pulmonary force and strain distributions, and to further explore how diseased states may alter the load-bearing material behavior of the lung. In the age of a respiratory pandemic, advancing our understanding of lung biomechanics is more pressing than ever before.

Digital volume correlation (DVC) in combination with high-resolution micro-computed tomography (mi-croCT) imaging and in situ mechanical testing is gaining popularity for quantifying 3D full-field strains in bone and biomaterials. However, traditional in situ time-lapsed (i.e., interrupted) mechanical testing cannot fully capture the dynamic strain mechanisms in viscoelastic biological materials. The aim of this study was to investigate the time-resolved deformation of bone structures and analogues via continu-ous in situ synchrotron-radiation microCT (SR-microCT) compression and DVC to gain a better insight into their structure-function relationships. Fast SR-microCT imaging enabled the deformation behaviour to be captured with high temporal and spatial resolution. Time-resolved DVC highlighted the relationship between local strains and damage initiation and progression in the different biostructures undergoing plastic deformation, bending and/or buckling of their main microstructural elements. The results showed that SR-microCT continuous mechanical testing complemented and enhanced the information obtained from time-lapsed testing, which may underestimate the 3D strain magnitudes as a result of the stress relaxation occurring in between steps before image acquisition in porous biomaterials. Altogether, the findings of this study highlight the importance of time-resolved in situ experiments to fully characterise the time-dependent mechanical behaviour of biological tissues and biomaterials and to further explore their micromechanics under physiologically relevant conditions. Statement of significance Time-resolved synchrotron X-ray tomography in combination with in situ mechanical testing provided the first four-dimensional analysis of the mechanical deformation of bone and bone analogues. To unravel the interplay of damage initiation and progression with local deformation, digital volume correlation was used to map the local strain field while microstructural changes were tracked with high temporal and spatial resolution. The results highlighted the importance of fast imaging and time-resolved in situ experiments to capture the real deformation of complex porous materials to fully characterize the lo-cal strain-damage relationship. The findings are notably improving the understanding of time-dependent mechanical behaviour of bone tissue, with the potential to be extend to highly viscoelastic biomaterials and soft tissues. (c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Globally, over three million women participate in rugby union, yet injury prevention and training strategies are predominantly based on androcentric data. These strategies may have limited generalisability to females, given the cervical spine is more susceptible to whiplash and less adept at resisting inertial loading. A total of 53 university rugby union players (25 female, 28 male, 20.7 ± 1.8 years) had their isometric neck strength measured. Bespoke instrumented mouthguards were used to record the magnitude of head impact events in six female and seven male competitive matches. Mean female maximal isometric neck strength was 47% lower than male. Independent samples Mann-Whitney U tests showed no significant differences for peak linear head acceleration (female: median 11.7 g, IQR 7.9 g; male: median 12.5 g, IQR 7.0 g p=.23) or peak rotational head acceleration (female: median 800.2 rad·s-2, IQR 677.7 rad·s-2; male: median 849.4 rad·s-2, IQR 479.8 rad·s-2; p=.76), despite the mean male body mass being 24% greater than female. Coded video analysis revealed substantial differences in head-impact mechanisms; uncontrolled whiplash dominated >50% of all recorded female impact events and <0.5% in males. Direct head-to-ground impacts comprised 26.1% of female and 9.7% of male impacts, with whiplash occurring in 78.0% and 0.5%, respectively. Overall, the data provided in this study do not support the generalisation of male-derived training and injury-prevention data to female rugby athletes. These results suggest a considerable research effort is required to identify specific weakness of female rugby players and derive appropriate training, injury prevention and return to play protocols.Highlights Video analysis revealed substantial differences in head-impact mechanisms, with uncontrolled whiplash dominating >50% of all recorded female impact events but rarely in males.Isometric neck strength was 47% lower in female players than males.Direct head-to-ground impacts accounted for 26.1% and 9.7% of female and male impacts, with whiplash occurring in 78.0% and 0.5%, respectively.