Materials as Machines McCracken, Joselle M.; Donovan, Brian R.; White, Timothy J.
Advanced materials,
05/2020, Letnik:
32, Številka:
20
Journal Article
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Machines are systems that harness input power to extend or advance function. Fundamentally, machines are based on the integration of materials with mechanisms to accomplish tasks—such as generating ...motion or lifting an object. An emerging research paradigm is the design, synthesis, and integration of responsive materials within or as machines. Herein, a particular focus is the integration of responsive materials to enable robotic (machine) functions such as gripping, lifting, or motility (walking, crawling, swimming, and flying). Key functional considerations of responsive materials in machine implementations are response time, cyclability (frequency and ruggedness), sizing, payload capacity, amenability to mechanical programming, performance in extreme environments, and autonomy. This review summarizes the material transformation mechanisms, mechanical design, and robotic integration of responsive materials including shape memory alloys (SMAs), piezoelectrics, dielectric elastomer actuators (DEAs), ionic electroactive polymers (IEAPs), pneumatics and hydraulics systems, shape memory polymers (SMPs), hydrogels, and liquid crystalline elastomers (LCEs) and networks (LCNs). Structural and geometrical fabrication of these materials as wires, coils, films, tubes, cones, unimorphs, bimorphs, and printed elements enables differentiated mechanical responses and consistently enables and extends functional use.
Advances in the development and integration of responsive materials are comprehensively surveyed with a particular emphasis on robotics, spanning shape‐memory alloys, piezoelectrics, electroactive polymers, shape‐memory polymers, hydrogels, and liquid crystalline polymer networks and elastomers.
Scientific models are like tools, and like any tool they can be evaluated according to how well they achieve the chosen goals of the task at hand. In the science of treatment development for chronic ...pain, we might say that a good model ought to achieve at least 3 goals: 1) integrate current knowledge, 2) organize research and treatment development activities, and 3) create progress. In the current review, we examine models underlying current cognitive behavioral approaches to chronic pain with respect to these criteria. A relatively new model is also presented as an option, and some of its features examined. This model is called the psychological flexibility model. This model fully integrates cognitive and behavioral principles and includes a process-oriented approach of treatment development. So far it appears capable of generating treatment applications that range widely with regard to conditions targeted and modes of delivery and that are increasingly supported by evidence. It has led to the generation of innovative experiential, relationship-based, and intensive treatment methods. The scientific strategy associated with this model seeks to find limitations in current models and to update them. It is assumed within this strategy that all current treatment approaches will one day appear lacking and will change.
This Focus Article addresses the place of theory and models in psychological research and treatment development in chronic pain. It is argued that such models are not merely an academic issue but are highly practical. One potential model, the psychological flexibility model, is examined in further detail.
Over 30 years ago, treatments based broadly within cognitive behavioral therapy (CBT) began a rise in prominence that eventually culminated in their widespread adoption in chronic pain treatment ...settings. Research into CBT has proliferated and continues today, addressing questions very similar to those addressed at the start of this enterprise. However, just as it is designed to do, the process of conducting research and analyzing evidence reveals gaps in our understanding of and shortcomings within this treatment approach. A need for development seems clear. This article reviews the progress of CBT in the treatment of chronic pain and the challenges now faced by researchers and clinicians interested in meeting this need for development. It then focuses in greater detail on areas of development within CBT, namely acceptance and commitment therapy (ACT) and mindfulness-based approaches, areas that may hold potential for future progress. Three specific recommendations are offered here to achieve this progress.
Whether a person with chronic pain avoids activity, persists with activity, or overexerts himself or herself is considered important to the quality of his or her daily functioning. However, results ...from studies of these activity patterns have not always yielded clear and consistent findings. It is suggested that applying the psychological flexibility model to activity patterns may clarify and integrate research in this area. Psychological flexibility is defined as the ability to persist or to change behavior in a setting of competing psychological influences, guided by goals and dependent on what the situation at hand affords. One aspect of psychological flexibility that appears pertinent to chronic pain is called committed action. Committed action is essentially goal-directed, flexible persistence. The purpose of the current study was to develop a measure of committed action, the committed action questionnaire (CAQ), in people seeking treatment for chronic pain (N = 216), to examine preliminary reliability and validity, and to test how well a summary score from the measure is able to predict patient health and functioning. Results generally support the internal consistency of the CAQ and show that it is correlated with another established component of psychological flexibility. In regression analyses the CAQ was able to account for significant variance in depression, social functioning, mental health, vitality, and general health, beyond the contributions of pain and acceptance of pain.
The psychological flexibility model may be useful for understanding patterns of behavior in relation to chronic pain. It appears possible to assess a process in this model called committed action, and this process appears related to important aspects of functioning.
The Patient Global Impression of Change (PGIC) measure has frequently been used as an indicator of meaningful change in treatments for chronic pain. However, limited research has examined the ...validity of PGIC items despite their wide adoption in clinical trials for pain. Additionally, research has not yet examined predictors of PGIC ratings following psychologically based treatment for pain. The purpose of the present study was to examine the validity, factor structure, and predictors of PGIC ratings following an interdisciplinary psychologically based treatment for chronic pain. Patients with chronic pain (N = 476) completed standard assessments of pain, daily functioning, and depression before and after a 4-week treatment program based on the principles of acceptance and commitment therapy. Following the program, patients rated 1 item assessing their impression of change overall and several items assessing their impression of more specific changes: physical and social functioning, work-related activities, mood, and pain. Results indicated that the global and specific impression of change items represent a single component. In the context of the acceptance and commitment therapy-based treatment studied here, overall PGIC ratings appeared to be influenced to a greater degree by patients' experienced improvements in physical activities and mood than by improvements in pain. The findings suggest that in addition to a single overall PGIC rating, domain-specific items may be relevant for some treatment trials.
This article reports on the validity and predictors of patients' impression of change ratings following interdisciplinary psychologically based treatment for pain. In addition to a single overall PGIC rating, domain-specific items may be important for clinicians and researchers to consider depending on the focus of treatment.
The 2019 coronavirus disease (COVID-19) pandemic, with its associated restrictions on daily life, is like a perfect storm for poor mental health and wellbeing. The purpose of this study was therefore ...to examine the impacts of COVID-19 on mental health and wellbeing during the ongoing pandemic in Sweden.
Standardized measures of depression, anxiety, and insomnia as well as measures of risk and vulnerability factors known to be associated with poor mental health outcomes were administered through a national, online, cross-sectional survey (n = 1,212; mean age 36.1 years; 73% women).
Our findings show significant levels of depression, anxiety, and insomnia in Sweden, at rates of 30%, 24.2%, and 38%, respectively. The strongest predictors of these outcomes included poor self-rated overall health and a history of mental health problems. The presence of COVID-19 symptoms and specific health and financial worries related to the pandemic also appeared important.
The impacts of COVID-19 on mental health in Sweden are comparable to impacts shown in previous studies in Italy and China. Importantly, the pandemic seems to impose most on the mental health of those already burdened with the impacts of mental health problems. These results provide a basis for providing more support for vulnerable groups, and for developing psychological interventions suited to the ongoing pandemic and for similar events in the future.
Liquid crystalline elastomers (LCEs) are crosslinked polymer networks that combine the elastic properties of rubber with the anisotropic properties of liquid crystals. Multifunctionality and ...responsivity can be programmed into LCEs by patterning their local orientation, which is difficult to achieve in other monolithic material systems. Advances in the synthesis and alignment of LCEs have paved the way for their functional integration in robotics, optics, consumer products, energy and healthcare devices. In this Review, we discuss recent advances in materials chemistry and processing that have contributed to the resurgence in LCE research. We examine the mechanical response of LCEs to stimuli and survey approaches for mechanical alignment, surface-enforced alignment, field-induced alignment and rheological alignment. The Review concludes with an over-the-horizon outlook discussing current challenges and emerging research opportunities.Liquid crystalline elastomers are stimuli-responsive polymeric materials whose mechanical properties can be programmed by patterning their local orientation, making them promising candidates to serve as low-density actuators and functional elements in various applications. This Review discusses the synthesis and processing of liquid crystalline elastomers, with a focus on alignment methods and potential applications.
There are now numerous studies of Acceptance and Commitment Therapy (ACT) for chronic pain. These studies provide growing support for the efficacy and effectiveness of ACT in this context as well as ...for the role of ACT-specific therapeutic processes, particularly those underlying
psychological flexibility. The purpose of the present study was to continue to build on this work with a broader focus on these processes, including acceptance of pain, general psychological acceptance, mindfulness, and values-based action. Participants included 168 patients who completed an ACT-based treatment for chronic pain and a three-month follow-up. Following treatment and at follow-up, participants reported significantly reduced levels of depression, pain-related anxiety, physical and psychosocial disability, medical visits, and pain intensity in comparison to the start of treatment. They also showed significant increases in each of the processes of psychological flexibility. Most uncontrolled effect sizes were medium or large at the follow-up. In correlation analyses changes in the four processes measures generally were significantly related to changes in the measures of depression, anxiety, and disability. In regression analyses the combined processes were related to changes in outcomes above and beyond change in pain intensity. Although in some ways preliminary, these results specifically support the unique role of general psychological acceptance in relation to improvements achieved by treatment participants. The current study clarifies potential processes of change in treatment for chronic pain, particularly those aiming to enhance psychological flexibility.
Liquid crystalline elastomers (LCE) are stimuli‐responsive materials with a distinguished mechanical response. LCE have been subject to numerous recent functional examinations in robotics, health ...sciences, and optics. The liquid crystallinity of the elastomeric polymer networks of LCE are largely derived from liquid crystalline monomer precursors. Recent reports have utilized commercially available liquid crystalline diacrylate monomers in chain extension reactions to prepare LCE. These reactions have been largely based on monomeric precursors originally to enhance the and thermal stability of optical films. Here, it is demonstrated that preparing LCE via a liquid crystalline diacrylate with reduced mesogen–mesogen interaction enhances and sharpens the thermotropic actuation of these materials. Robust composition‐response correlations are demonstrated in LCE prepared by three common synthetic methods. The enhanced thermotropic response of LCE prepared from this precursor increases the thermomechanical efficiency by sixfold. Accordingly, this work addresses important limitations in utilizing the thermal response of LCE in robotics, health care, and consumer goods.
Numerous reports document liquid crystalline elastomers (LCE) based on commercially available liquid crystalline monomers containing three phenyl rings that demonstrate exceptional stimuli‐induced mechanical response in functional applications in robotics, health care, aerospace, and consumer goods. Here, a LCE monomer with reduced intermolecular coupling is incorporated to lower actuation onset temperature and enhance the thermomechanical efficiency of LCE sixfold.
Under normal physiological conditions, tissue remodeling in response to injury leads to tissue regeneration without permanent damage. However, if homeostasis between synthesis and degradation of ...extracellular matrix (ECM) components is altered, fibrosis - or the excess accumulation of ECM - can disrupt tissue architecture and function. Several organs, including the heart, lung and kidney, exhibit age-associated fibrosis. Here we investigated whether fibrosis underlies aging in the ovary - an organ that ages chronologically before other organs. We used Picrosirius Red (PSR), a connective tissue stain specific for collagen I and III fibers, to evaluate ovarian fibrosis. Using bright-field, epifluorescence, confocal and polarized light microscopy, we validated the specific staining of highly ordered PSR-stained fibers in the ovary. We next examined ovarian PSR staining in two mouse strains (CD1 and CB6F1) across an aging continuum and found that PSR staining was minimal in ovaries from reproductively young adult animals, increased in distinct foci in animals of mid-to-advanced reproductive age, and was prominent throughout the stroma of the oldest animals. Consistent with fibrosis, there was a reproductive age-associated increase in ovarian hydroxyproline content. We also observed a unique population of multinucleated macrophage giant cells, which are associated with chronic inflammation, within the ovarian stroma exclusively in reproductively old mice. In fact, several genes central to inflammation had significantly higher levels of expression in ovaries from reproductively old mice relative to young mice. These results establish fibrosis as an early hallmark of the aging ovarian stroma, and this altered microenvironment may contribute to the age-associated decline in gamete quality.
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