Self-deployable contracting-cord metamaterials with tunable mechanical properties.

Recent advances in active materials and fabrication techniques have enabled the production of cyclically self-deployable metamaterials with an expanded functionality space. However, designing metamaterials that possess continuously tunable mechanical properties after self-deployment remains a challenge, notwithstanding its importance. Inspired by push puppets, we introduce an efficient design strategy to create reversibly self-deployable metamaterials with continuously tunable post-deployment stiffness and damping. Our metamaterial comprises contracting actuators threaded through beads with matching conical concavo-convex interfaces in networked chains. The slack network conforms to arbitrary shapes, but when actuated, it self-assembles into a preprogrammed configuration with beads gathered together. Further contraction of the actuators can dynamically tune the assembly's mechanical properties through the beads' particle jamming, while maintaining the overall structure with minimal change. We show that, after deployment, such metamaterials exhibit pronounced tunability in bending-dominated configurations: they can become more than 35 times stiffer and change their damping capability by over 50%. Through systematic analysis, we find that the beads' conical angle can introduce geometric nonlinearity, which has a major effect on the self-deployability and tunability of the metamaterial. Our work provides routes towards reversibly self-deployable, lightweight, and tunable metamaterials, with potential applications in soft robotics, reconfigurable architectures, and space engineering.

Compliant Intramedullary Stems for Joint Reconstruction.

The longevity of current joint replacements is limited by aseptic loosening, which is the primary cause of non-infectious failure for hip, knee, and ankle arthroplasty. Aseptic loosening is typically caused either by osteolysis from particulate wear, or by high shear stresses at the bone-implant interface from over-constraint. Our objective was to demonstrate feasibility of a compliant intramedullary stem that eliminates over-constraint without generating particulate wear. The compliant stem is built around a compliant mechanism that permits rotation about a single axis. We first established several models to understand the relationship between mechanism geometry and implant performance under a given angular displacement and compressive load. We then used a neural network to identify a design space of geometries that would support an expected 100-year fatigue life inside the body. We additively manufactured one representative mechanism for each of three anatomic locations, and evaluated these prototypes on a KR-210 robot. The neural network predicts maximum stress and torsional stiffness with 2.69% and 4.08% error respectively, relative to finite element analysis data. We identified feasible design spaces for all three of the anatomic locations. Simulated peak stresses for the three stem prototypes were below the fatigue limit. Benchtop performance of all three prototypes was within design specifications. Our results demonstrate the feasibility of designing patient- and joint-specific compliant stems that address the root causes of aseptic loosening. Guided by these results, we expect the use of compliant intramedullary stems in joint reconstruction technology to increase implant lifetime.

Self-care interventions for women's health and well-being.

The human right to health is universal and non-exclusionary, supporting health in full, and for all. Despite advances in health systems globally, 3.6 billion people lack access to essential health services. Women and girls are disadvantaged when it comes to benefiting from quality health services, owing to social norms, unequal power in relationships, lack of consideration beyond their reproductive roles and poverty. Self-care interventions, including medicines and diagnostics, which offer an additional option to facility-based care, can improve the autonomy and agency of women in managing their own health. However, tackling challenges such as stigma is essential to avoid scenarios in which self-care interventions provide more choice for those who already benefit from access to quality healthcare, and leave behind those with the greatest need. This Perspective explores the opportunities that self-care interventions offer to advance the health and well-being of women with an approach grounded in human rights, gender equality and equity.

The importance of insufficient national data on sexual and reproductive health and rights in international databases.

Looking at SRHR as an isolated set of elements, as is the current practice, does not do justice to the needs and rights of people and communities and may be one of the reasons why challenges remain in the attainment of SRHR for all. SRHR Infographic snapshots were developed for all 194 WHO Member States and included 120 indicators covering a broad range of policy, health systems and service delivery interventions. The snapshots were created using data less than 10 years old publicly available in data repositories maintained by international and global agencies. Data availability was not consistent across countries with low and lower-middle income countries having higher data availability (71%) compared to high income countries (40%). SRHR data that is easily accessible and consistently reported can improve accountability and opportunities for learning to improve people-centred approaches to accelerate the attainment of SRHR for all.

Factors associated with current substance use among a sample of homeless individuals in Cape Town, South Africa: a secondary data analysis.

Homelessness is a global issue that is often associated with substance use. Research on this relationship in low- to middle-income countries (LMIC) is limited. We aimed to explore which factors are associated with substance use through secondary data analysis of a sample of 472 adults who attended services for homeless individuals in Cape Town, South Africa. Logistic regression was utilized to investigate if length of homelessness was associated with current alcohol and drug use respectively, after accounting for other factors. Current drug use (44.9%) was higher than current alcohol use (22.7%) and the most prevalent lifetime drug was methamphetamine (32.6%). After adjusting for lifetime substance use, and source of income, length of homelessness was not significantly associated with current alcohol use (less than on year: OR = 2.60; 95% CI: 0.78-8.66; one or more years: OR = 0.90; 95% CI: 0.32-2.57) or current drug use (less than one year: OR = 0.78; 95% CI: 0.41-1.47; one year or more: OR = 1.04; 95% CI: 0.56-1.93). These results highlight the need to further investigate other factors that may influence current alcohol or drug use among populations at risk of being homeless, and to utilize validated measures of substance and other mental health conditions.

Mechanical neural networks: Architected materials that learn behaviors.

Aside from some living tissues, few materials can autonomously learn to exhibit desired behaviors as a consequence of prolonged exposure to unanticipated ambient loading scenarios. Still fewer materials can continue to exhibit previously learned behaviors in the midst of changing conditions (e.g., rising levels of internal damage, varying fixturing scenarios, and fluctuating external loads) while also acquiring new behaviors best suited for the situation at hand. Here, we describe a class of architected materials, called mechanical neural networks (MNNs), that achieve such learning capabilities by tuning the stiffness of their constituent beams similar to how artificial neural networks (ANNs) tune their weights. An example lattice was fabricated to demonstrate its ability to learn multiple mechanical behaviors simultaneously, and a study was conducted to determine the effect of lattice size, packing configuration, algorithm type, behavior number, and linear-versus-nonlinear stiffness tunability on MNN learning as proposed. Thus, this work lays the foundation for artificial-intelligent (AI) materials that can learn behaviors and properties.

Short Communication: Awareness of HIV Self-Care Interventions Across Global Regions: Results from a Values and Preferences Survey.

The high burden of HIV in sub-Saharan Africa places significant demands on health care services. Interventions such as HIV self-testing, and pre- and post-exposure prophylaxis (PrEP and PEP) could empower individuals to determine their HIV status and prevent HIV acquisition. In 2018, the World Health Organization disseminated an online, anonymous, global values and preferences survey to adults 18 years of age and older. The survey aimed to inform guidance on awareness, use, and preferences around self-care interventions for sexual and reproductive health. We conducted a cross-sectional analysis using Pearson's chi-squared test to compare awareness of HIV self-testing, PrEP and PEP across five global regions. Our analysis included 814 participants from 110 countries. We noted that respondents from Africa reported higher awareness of HIV interventions than participants from Europe, Latin America and the Caribbean, North America, and Asia. Our finding highlights an opportunity to expand self-care interventions for HIV prevention and management in Africa.

Sequential metamaterials with alternating Poisson's ratios.

Mechanical metamaterials have been designed to achieve custom Poisson's ratios via the deformation of their microarchitecture. These designs, however, have yet to achieve the capability of exhibiting Poisson's ratios that alternate by design both temporally and spatially according to deformation. This capability would enable dynamic shape-morphing applications including smart materials that process mechanical information according to multiple time-ordered output signals without requiring active control or power. Herein, both periodic and graded metamaterials are introduced that leverage principles of differential stiffness and self-contact to passively achieve sequential deformations, which manifest as user-specified alternating Poisson's ratios. An analytical approach is provided with a complementary software tool that enables the design of such materials in two- and three-dimensions. This advance in design capability is due to the fact that the tool computes sequential deformations more than an order of magnitude faster than contemporary finite-element packages. Experiments on macro- and micro-scale designs validate their predicted alternating Poisson's ratios.

The role of self-care interventions on men's health-seeking behaviours to advance their sexual and reproductive health and rights.

BACKGROUND: Self-care interventions are influencing people's access to, expectation and understanding of healthcare beyond formal health delivery systems. In doing so, self-care interventions could potentially improve health-seeking behaviours. While many men proactively engage in maintaining and promoting their health, the focus on men's health comes from the recognition, at least partially, that male socialization and social norms can induce men and boys to have a lower engagement in institutionalized public health entities and systems around their sexual and reproductive health and rights, that could impact negatively on themselves, their partners and children. MAIN TEXT: A research agenda could consider the ways that public health messaging and information on self care practices for sexual and reproductive health and rights could be tailored to reflect men's lived realities and experiences. Three examples of evidence-based self-care interventions related to sexual and reproductive health and rights that men can, and many do, engage in are briefly discussed: condom use, HIV self-testing and use of telemedicine and digital platforms for sexual health. We apply four core elements that contribute to health, including men's health (people-centred approaches, quality health systems, a safe and supportive enabling environment, and behaviour-change communication) to each intervention where further research can inform normative guidance. CONCLUSION: Engaging men and boys and facilitating their participation in self care can be an important policy intervention to advance global sexual and reproductive health and rights goals. The longstanding model of men neglecting or even sabotaging their wellbeing needs to be replaced by healthier lifestyles, which requires understanding how factors related to social support, social norms, power, academic performance or employability conditions, among others, influence men's engagement with health services and with their own self care practices.

Scanning two-photon continuous flow lithography for the fabrication of multi-functional microparticles.

In this work, we demonstrate the high-throughput fabrication of 3D microparticles using a scanning two-photon continuous flow lithography (STP-CFL) technique in which microparticles are shaped by scanning the laser beam at the interface of laminar co-flows. The results demonstrate the ability of STP-CFL to manufacture high-resolution complex geometries of cell carriers that possess distinct regions with different functionalities. A new approach is presented for printing out-of-plane features on the microparticles. The approach eliminates the use of axial scanning stages, which are not favorable since they induce fluctuations in the flowing polymer media and their scanning speed is slower than the speed of galvanometer mirror scanners.

Automated Optical-Tweezers Assembly of Engineered Microgranular Crystals.

In this work, a scalable automated approach for fabricating 3D microgranular crystals consisting of desired arrangements of microspheres using holographic optical tweezers and two-photon polymerization is introduced. The ability to position microspheres as desired within lattices of any configuration allows designers to engineer the behavior of new metamaterials that enable advanced applications (e.g., armor that mitigates or redirects shock waves, acoustic lens for underwater imaging, damage detection, and noninvasive surgery, acoustic cloaking, and photonic crystals). Currently, no self-assembly or automated approaches exist with the flexibility necessary to place specific microspheres at specific locations within a crystal. Moreover, most pick-and-place approaches require the manual assembly of spheres one by one and thus do not achieve the speed and precision required to repeatably fabricate practical volumes of engineered crystals. In this paper, the rapid assembly of 4.86 µm diameter silica spheres within differently packed 3D crystal-lattice examples of unprecedented size using fully automated optical tweezers is demonstrated. The optical tweezers independently and simultaneously assemble batches of spheres that are dispensed to the build site via an automated syringe pump where the spheres are then joined together within previously unattainable patterns by curing regions of photocurable prepolymer between each sphere using two-photon polymerization.

Translumbar Embolization of Type II Endoleaks: 12 Years of Experience at a Regional Vascular Centre.

BACKGROUND AND AIMS: The management of persistent type II endoleaks (T2E) is often problematic for the endovascular specialist, with a lack of clear evidence for the best approach for embolization. The aim of this study was to evaluate the safety and efficacy of translumbar embolization (TLE) for T2E following endovascular aneurysm repair (EVAR). METHODS: This retrospective review included 27 embolizations performed on 23 patients with a median age of 78 (range 67-94 years; male: female 15:9), during the period September 2006 to July 2018. Primary outcome was freedom from aneurysm sac growth defined as <2 mm sac diameter increase on subsequent computed tomography. RESULTS: The initial technical success rate was 100%, with complete "on table" embolization of the T2E on fluoroscopy; however, 4 (15%) patients needed repeat TLE due to persistent endoleak identified on follow-up computed tomography or because of further sac expansion. Satisfactory stasis was achieved in these 4 cases following a second embolization. The mean volume of embolic injected was 7.4 mL per case. Feeding vessels were identified on angiography in all cases; the nidus was supplied by lumbar branches in 21 cases, by the inferior mesenteric artery in 1 case and by both in a further 5 cases. Freedom from aneurysm sac growth (defined as < 2 mm) following 1 or 2 separate TLE was achieved in 18 (78%) and 20 (86%) patients, respectively. The major complication rate was <5% with one case of psoas abscess presenting 7 months following embolization; there were 2 minor complications in the form of intraprocedural transient abdominal pain. CONCLUSION: The translumbar approach is a safe and effective technique to treat T2E, as evidenced by the low complication and reintervention rate.

Abdominal Aortic Aneurysm Repair in Renal and Liver Transplant Recipients.

BACKGROUND: Abdominal aortic aneurysm (AAA) repair in patients with organ transplant remains a challenge. We looked at AAA repair in patients with organ transplants at our tertiary liver and kidney transplant unit. METHODS: A retrospective analysis of a prospectively maintained database was undertaken from January 2008 to July 2018. We looked at patient demographics, type of repair, and technical success including reinterventions, perioperative transplant organ function, and 30-day and 1-year survival rate. Eight of 662 patients who underwent AAA repair had a solid organ transplant. Of these, 5 were kidney transplants, 2 liver transplants, and 1 had kidney and liver transplant; 75% were male; and average age was 63.4 (range: 49-83). All patients had asymptomatic AAAs, and 6 were treated with standard endovascular repair, 1 standard repair with iliac branch device, and 1 open repair. Adjunctive techniques such as CO2 angiograms, deployment of main body through contralateral iliac, low-profile sheaths, custom-made stent grafts, and temporary axillo-femoral shunting were used to protect transplant organs. Thirty-day survival was 100% with 1 death at 5 months from liver failure, and 1 patient has a persistent type-2 endoleak 3 years after the procedure. CONCLUSION: Abdominal aortic aneurysm repair in patients with organ transplants can be undertaken using adjunctive endovascular and open surgical techniques.

All-Organic Semiconductors for Electrochemical Biosensors: An Overview of Recent Progress in Material Design.

Organic semiconductors remain of major interest in the field of bioelectrochemistry for their versatility in chemical and electrochemical behavior. These materials have been tailored using organic synthesis for use in cell stimulation, sustainable energy production, and in biosensors. Recent progress in the field of fully organic semiconductor biosensors is outlined in this review, with a particular emphasis on the synthetic tailoring of these semiconductors for their intended application. Biosensors ultimately function on the basis of a physical, optical or electrochemical change which occurs in the active material when it encounters the target analyte. Electrochemical biosensors are becoming increasingly popular among organic semiconductor biosensors, owing to their good detection performances, and simple operation. The analyte either interacts directly with the semiconductor material in a redox process or undergoes a redox process with a moiety such as an enzyme attached to the semiconductor material. The electrochemical signal is then transduced through the semiconductor material. The most recent examples of organic semiconductor biosensors are discussed here with reference to the material design of polymers with semiconducting backbones, specifically conjugated polymers, and polymer semiconducting dyes. We conclude that direct interaction between the analyte and the semiconducting material is generally more sensitive and cost effective, despite being currently limited by the need to identify, and synthesize selective sensing functionalities. It is also worth noting the potential roles of highly-sensitive, organic transistor devices and small molecule semiconductors, such as the photochromic and redox active molecule spiropyran, as polymer pendant groups in future biosensor designs.

Additively manufacturable micro-mechanical logic gates.

Early examples of computers were almost exclusively based on mechanical devices. Although electronic computers became dominant in the past 60 years, recent advancements in three-dimensional micro-additive manufacturing technology provide new fabrication techniques for complex microstructures which have rekindled research interest in mechanical computations. Here we propose a new digital mechanical computation approach based on additively-manufacturable micro-mechanical logic gates. The proposed mechanical logic gates (i.e., NOT, AND, OR, NAND, and NOR gates) utilize multi-stable micro-flexures that buckle to perform Boolean computations based purely on mechanical forces and displacements with no electronic components. A key benefit of the proposed approach is that such systems can be additively fabricated as embedded parts of microarchitected metamaterials that are capable of interacting mechanically with their surrounding environment while processing and storing digital data internally without requiring electric power.

Computationally efficient design of directionally compliant metamaterials.

Designing mechanical metamaterials is overwhelming for most computational approaches because of the staggering number and complexity of flexible elements that constitute their architecture-particularly if these elements don't repeat in periodic patterns or collectively occupy irregular bulk shapes. We introduce an approach, inspired by the freedom and constraint topologies (FACT) methodology, that leverages simplified assumptions to enable the design of such materials with ~6 orders of magnitude greater computational efficiency than other approaches (e.g., topology optimization). Metamaterials designed using this approach are called directionally compliant metamaterials (DCMs) because they manifest prescribed compliant directions while possessing high stiffness in all other directions. Since their compliant directions are governed by both macroscale shape and microscale architecture, DCMs can be engineered with the necessary design freedom to facilitate arbitrary form and unprecedented anisotropy. Thus, DCMs show promise as irregularly shaped flexure bearings, compliant prosthetics, morphing structures, and soft robots.

Compliant rolling-contact architected materials for shape reconfigurability.

Architected materials can achieve impressive shape-changing capabilities according to how their microarchitecture is engineered. Here we introduce an approach for dramatically advancing such capabilities by utilizing wrapped flexure straps to guide the rolling motions of tightly packed micro-cams that constitute the material's microarchitecture. This approach enables high shape-morphing versatility and extreme ranges of deformation without accruing appreciable increases in strain energy or internal stress. Two-dimensional and three-dimensional macroscale prototypes are demonstrated, and the analytical theory necessary to design the proposed materials is provided and packaged as a software tool. An approach that combines two-photon stereolithography and scanning holographic optical tweezers is demonstrated to enable the fabrication of the proposed materials at their intended microscale.

Improving the throughput of automated holographic optical tweezers.

The purpose of this work is to introduce three improvements to automated holographic-optical-tweezers systems that increase the number and speed of particles that can be manipulated simultaneously. First, we address path planning by solving a bottleneck assignment problem, which can reduce total move time by up to 30% when compared with traditional assignment problem solutions. Next, we demonstrate a new strategy to identify and remove undesired (e.g., misshapen or agglomerated) particles. Finally, we employ a controller that combines both closed- and open-loop automation steps, which can increase the overall loop rate and average particle speeds while also utilizing necessary process monitoring checks to ensure that particles reach their destinations. Using these improvements, we show fast reconfiguration of 100 microspheres simultaneously with a closed-loop control rate of 6, and 10 Hz by employing both closed- and open-loop steps. We also demonstrate the closed-loop assembly of a large pattern in a continuously flowing microchannel-based particle-delivery system. The proposed approach provides a promising path toward automatic and scalable assembly of microgranular structures.

Experimental characterization and modeling of optical tweezer particle handling dynamics.

We report a new framework for a quantitative understanding of optical trapping (OT) particle handling dynamics. We present a novel three-dimensional particle-based model that includes optical, hydrodynamic, and inter-particle forces. This semi-empirical colloid model is based on an open-source simulation code known as LAMMPS (large-scale atomic/molecular massively parallel simulator) and properly recapitulates the full OT force profile beyond the typical linear approximations valid near the trap center. Simulations are carried out with typical system parameters relevant for our experimental holographic optical trapping (HOT) system, including varied particle sizes, trap movement speeds, and beam powers. Furthermore, we present a new experimental method for measuring both the stable and metastable boundaries of the optical force profile to inform or validate the model's underlying force profile. We show that our framework is a powerful tool for accurately predicting particle behavior in a practical experimental OT setup and can be used to characterize and predict particle handling dynamics within any arbitrary OT force profile.