Repetitive Mechanical Stress Research Articles

Small-Sided-Game-Induced Mechanical Load in Adolescent Soccer: The Need for Care and Consideration for Athlete Preservation.

The logistical efficiency and flexibility of small-sided games (SSG) to develop various soccer-specific attributes simultaneously make them a staple component of contemporary training programs in youth soccer. Their high ecological validity and consequential high utilization mean that if not considerately prescribed, players may be exposed to frequent repetitive mechanical stress that may induce maladaptation in skeletally and/or load-naïve or sensitive athletes. The purpose of this clinical review is to summarize mechanical load adaptations associated with the manipulation of area per player in SSG to outline the mechanistic pathway of load-related injuries in skeletally maturing athletes and to offer practical guidelines for coaches for the preservation of athlete health. A nonsystematic search of computerized databases of peer-reviewed articles in English between 2010 and the present was used, and a critical appraisal of existing literature was subsequently conducted. Clinical review. Level 4. The temporary relative strength deficit and inefficiency of the musculotendinous system associated with accelerated growth increase the mechanical cost of activity. As a result, the load tolerance (ie, tolerant, naïve, or sensitive) of athletes is transiently reduced as the musculoskeletal system struggles to attenuate force absorption adequately. Repeated exposure to submaximal mechanical loads that stimulate the accumulation of "microdamage" in structural tissue may lead to aggravation and/or tissue failure at connective sites in skeletally fragile athletes. Coaches and practitioners need to individualize exposure to mechanical load for load-tolerant, naïve, and sensitive athletes during adolescence. Subtle changes to SSG prescription including modifying the area per player, inclusion of goalkeepers, constrained floaters, and management of work; rest ratios can offer practical and efficient methods to mitigate risk without derailing the development process. This, in turn, should contribute to reducing injury burden in this population and enhance developmental opportunities for young players. A. Recommendation based on consistent and good-quality evidence published from 2010 onwards.

A Case Study on the Therapeutic Efficacy of <i>Suttigai</i> (Thermal Cauterization) in the Management of <i>Kaalani</i> (Corn Foot)

A 45-year-old, moderately built female presented with complaints of a thickened layer of skin in the foot with severe pain for over three years. She was diagnosed to be affected by Corn foot which is equated to Kaalani in the Siddha system of medicine. Corn is a well-defined focal region of hyperkeratosis. As a result of repetitive mechanical stress from friction or pressure forces, corns are formed as thickened skin lesions. Suttigai is one of the treatment modalities indicated for Kaalani in Siddha. Uloga suttigai is superior among all suttigai procedures and an effective treatment for Kaalani which prevents recurrence was chosen to treat corn foot. A Visual Analogue Scale(VAS) was used for the criteria of assessment of pain. The patient was treated successfully by uloga suttigai with the total repair of corn without any unsightly scar or discoloration. No other complications and remissions were found.

Comparative analysis of meningeal transcriptomes in birds: Potential pathways of resilience to repeated impacts.

The meninges and associated vasculature (MAV) play a crucial role in maintaining cerebral integrity and homeostasis. Recent advances in transcriptomic analysis have illuminated the significance of the MAV in understanding the complex physiological interactions at the interface between the skull and the brain after exposure to mechanical stress. To investigate how physiological responses may confer resilience against repetitive mechanical stress, we performed the first transcriptomic analysis of avian MAV tissues using the Downy Woodpecker (Dryobates pubescens) and Tufted Titmouse (Baeolophus bicolor) as the comparison species. Our findings reveal divergences in gene expression profiles related to immune response, cellular stress management, and protein translation machinery. The male woodpeckers exhibit a tailored immune modulation strategy that potentially dampens neuroinflammation while preserving protective immunity. Overrepresented genes involved in cellular stress responses suggest enhanced mechanisms for mitigating damage and promoting repair. Additionally, the enrichment of translation-associated pathways hints at increased capacity for protein turnover and cellular remodeling vital for recovery. Our study not only fills a critical gap in avian neurobiology but also lays the groundwork for research in comparative neuroprotection.

Evaluation under loading detects medial meniscus extrusion in patients with reconstructed anterior cruciate ligament and restricted knee extension.

Some patients who undergo anterior cruciate ligament (ACL) reconstruction experience abnormal mechanical stress in the meniscus. Medial meniscal extrusion (MME) is reflected in the pathological condition of the meniscus, which expands owing to repetitive mechanical stress. Thus, the effect of the reconstructed ACL on increasing MME under weight-bearing conditions remains unclear. This study investigated the effect of ACL reconstruction on meniscal extrusion under non-weight-bearing and weight-bearing conditions. Seventeen patients who underwent unilateral ACL reconstruction (ACL group) and 20 age-matched healthy volunteers (control group) were enrolled. Ultrasonography was performed in the supine, standing, and walking positions in preoperative and postoperative ACL patients. MME during walking was evaluated based on the dynamic behavior of extrusion, and kinetic and kinematic data were synchronously obtained. Moreover, the ACL group underwent magnetic resonance imaging (MRI) evaluation at two points: preoperatively and 12months postoperatively, and the ultrasound findings were compared. MME in the supine position measured using both ultrasonography and MRI was not significantly different preoperatively and postoperatively in the ACL group. However, postoperative MME and dynamic behavior of extrusion under standing and walking conditions were significantly higher than those in the preoperative state (dynamic behavior: 0.9 ± 0.4mm preoperatively, 1.2 ± 0.4mm postoperatively). Moreover, the deficits in knee extension during walking persisted postoperatively and were significantly higher than those in the control group. MME in patients with ACL reconstruction including meniscus repair was different under mechanical stress compared to the non-weight bearing condition.

Elastogenesis in Focus: Navigating Elastic Fibers Synthesis for Advanced Dermal Biomaterial Formulation.

Elastin, a fibrous extracellular matrix (ECM) protein, is the main component of elastic fibers that are involved in tissues' elasticity and resilience, enabling them to undergo reversible extensibility and to endure repetitive mechanical stress. After wounding, it is challenging to regenerate elastic fibers and biomaterials developed thus far have struggled to induce its biosynthesis. This review provides a comprehensive summary of elastic fibers synthesis at the cellular level and its implications for biomaterial formulation, with a particular focus on dermal substitutes. The review delves into the intricate process of elastogenesis by cells and investigates potential triggers for elastogenesis encompassing elastin-related compounds, ECM components, and other molecules for their potential role in inducing elastin formation. Understanding of the elastogenic processes is essential for developing biomaterials that trigger not only the synthesis of the elastin protein, but also the formation of a functional and branched elastic fiber network.

Leaflet Mechanical Stress in Different Designs and Generations of Transcatheter Aortic Valves: An in Vitro Study

BackgroundIt is unknown whether bioprostheses used for transcatheter aortic valve implantation will have similar long-term durability as those used for surgical aortic valve replacement. Repetitive mechanical stress applied to the valve leaflets, particularly during diastole, is the main determinant of structural valve deterioration. Leaflet mechanical stress cannot be measured in vivo. The objective of this in vitro/in silico study was thus to compare the magnitude and regional distribution of leaflet mechanical stress in old vs new generations of self-expanding (SE) vs balloon expandable (BE) transcatheter heart valves (THVs). MethodsA double activation simulator was used for in vitro testing of two generations of SE THV (Medtronic CoreValve 26 mm and EVOLUT PRO 26 mm) and two generations of BE THV (Edwards SAPIEN 23 mm vs SAPIEN-3 23 mm). These THVs were implanted within a 21-mm aortic annulus. A noncontact system based on stereophotogammetry and digital image correlation with high spatial and temporal resolution (2000 img/sec) was used to visualize the valve leaflet motion and perform the three-dimensional analysis. A finite element model of the valve was developed, and the leaflet deformation obtained from the digital image correlation analysis was applied to the finite element model to calculate local leaflet mechanical stress during diastole. ResultsThe maximum von Mises leaflet stress was higher in early vs new THV generation (p < 0.05) and in BE vs SE THV (p < 0.05): early generation BE: 2.48 vs SE: 1.40 MPa; new generation BE: 1.68 vs SE: 1.07 MPa. For both types of THV, the highest values of leaflet stress were primarily observed in the upper leaflet edge near the commissures and to a lesser extent in the mid-portion of the leaflet body, which is the area where structural leaflet deterioration most often occurs in vivo. ConclusionsThe results of this in vitro/in silico study suggest that: i) Newer generations of THVs have ∼30% lower leaflet mechanical stress than the early generations; ii) For a given generation, SE THVs have lower leaflet mechanical stress than BE THVs. Further studies are needed to determine if these differences between new vs early THV generations and between SE vs BE THVs will translate into significant differences in long-term valve durability in vivo.

Treatment and Rehabilitation Approaches for Stress Fractures in Long-Distance Runners: A Literature Review.

Stress fractures (SFs) result from repetitive mechanical stress on bones, leading to an imbalance in osseous tissue adaptation and resulting in cortical fractures. The majority of SFs occur in the lower limb due to excessive mechanical loads. Long-distance runners are highly susceptible to SFs, especially when there is a significant increase in the load or intensity of their activity. Various intrinsic and extrinsic factors contribute to the development of SFs. Common SF locations in long-distance runners include the tibial shaft, femur, metatarsal, and pelvic region. Diagnosis may be delayed due to mild symptoms and unremarkable imaging tests. However, the chronicity and recurrence of misdiagnosed SFs may lead to debilitating complete fractures that are even more challenging to treat. In this review, we present data revealed from published case reports and case series studies obtained through PubMed and Embase databases focusing on the management of SFs in long-distance runners and correlate treatment outcomes with rehabilitation and return to high-level athletic performance.

The Inflammasome-Dependent Dysfunction and Death of Retinal Ganglion Cells after Repetitive Intraocular Pressure Spikes.

The dysfunction and selective loss of retinal ganglion cells (RGCs) is a known cause of vision loss in glaucoma and other neuropathies, where ocular hypertension (OHT) is the major risk factor. We investigated the impact of transient non-ischemic OHT spikes (spOHT) on RGC function and viability in vivo to identify cellular pathways linking low-grade repetitive mechanical stress to RGC pathology. We found that repetitive spOHT had an unexpectedly high impact on intraocular homeostasis and RGC viability, while exposure to steady OHT (stOHT) of a similar intensity and duration failed to induce pathology. The repetitive spOHT induced the rapid activation of the inflammasome, marked by the upregulation of NLRP1, NLRP3, AIM2, caspases -1, -3/7, -8, and Gasdermin D (GSDMD), and the release of interleukin-1β (IL-1β) and other cytokines into the vitreous. Similar effects were also detected after 5 weeks of exposure to chronic OHT in an induced glaucoma model. The onset of these immune responses in both spOHT and glaucoma models preceded a 50% deficit in pattern electroretinogram (PERG) amplitude and a significant loss of RGCs 7 days post-injury. The inactivation of inflammasome complexes in Nlrp1-/-, Casp1-/-, and GsdmD-/- knockout animals significantly suppressed the spOHT-induced inflammatory response and protected RGCs. Our results demonstrate that mechanical stress produced by acute repetitive spOHT or chronic OHT is mechanistically linked to inflammasome activation, which leads to RGC dysfunction and death.

Scratching increases epidermal neuronal branching and alters psychophysical testing responses in atopic dermatitis and brachioradial pruritus.

Chronic scratching imposes a major stress on the skin and can lead to itch intensity worsening, and consequently, patients may enter an itch-scratch cycle. This repetitive mechanical stress can result in lichenification, worsening of epidermal barrier function, and enhanced cutaneous inflammation. Furthermore, a reduction of intraepidermal nerve fibers was previously described in lichenification. The aim of this study was to investigate the influence of chronic scratching on the epidermal neuroanatomy and on sensory changes, in particular the prevalence of hyperknesis and alloknesis in patients after mechanical, chemical, and electrical stimuli. Analyses were performed on pruritic lichenified (chronically scratched), pruritic non-lichenified (not chronically scratched), and non-pruritic non-lesional (unaffected) skin areas of patients with inflammatory pruritus, i.e., atopic dermatitis (n = 35), and neuropathic pruritus, i.e., brachioradial pruritus (n = 34) vs. healthy matched controls (n = 64). Our fine-grained spatial skin characterization enabled specifically studying the differential effects of chronic scratching in inflammatory and neuropathic itch. Analysis of intraepidermal nerve fiber density showed rarefaction of fibers in all three skin areas of patients compared with healthy controls in both diagnoses. Even more, the two pruritic areas had significantly less nerve fibers than the unaffected skin, whereas electrically induced itch was massively increased. Epidermal branching of the remaining nerve fibers in lichenified/chronically scratched skin was increased, particularly in patients with brachioradial pruritus, which may contribute to the pronounced local neuronal sensitivity. Hyperknesis and alloknesis were found to increase independently of lichenification. Our results indicate that chronic scratching may not affect intraepidermal nerve fiber density but leads to a stronger branching pattern of intraepidermal nerve fibers, which may contribute to local hypersensitivity. The increased sensitivity in the pruritic areas suggests mechanisms of peripheral sensitization, whereas the increased sensation of electrically and chemically induced itch in unaffected skin indicates central sensitization for itch.

Softening of PEO-LiTFSI/LLZTO Composite Polymer Electrolytes for Solid-State Batteries under Cyclic Compression.

Composite polymer electrolytes (CPEs) strike an effective balance between ionic conductivity and mechanical flexibility for lithium-ion solid-state batteries. Long-term performance, however, is limited by capacity fading after hundreds of charge and discharge cycles. The causes of performance degradation include multiple contributing factors such as dendrite formation, physicochemical changes in electrolytes, and structural remodeling of porous electrodes. Among the many factors that contribute to performance degradation, the effect of stress specifically on the composite electrolyte is not well understood. This study examines the mechanical changes in a poly(ethylene oxide) electrolyte with bis(trifluoromethane) sulfonimide. Two different sizes of Li6.4La3Zr1.4Ta0.6O12 particles (500 nm and 5 μm) are compared to evaluate the effect of the surface-to-volume ratio of the ion-conducting fillers within the composite. Cyclic compression was applied to mimic stress cycling in the electrolyte, which would be caused by asymmetric volume changes that occur during charging and discharging cycles. The electrolytes exhibited fatigue softening, whereby the compressive modulus gradually decreased with an increase in the number of cycles. When the electrolyte was tested for 500 cycles at 30% compressive strain, the compressive modulus of the electrolyte was reduced to approximately 80% of the modulus before cycling. While the extent of softening was similar regardless of particle size, CPEs with 500 nm particles exhibited a significant reduction in ionic conductivity after cyclic compression (1.4 × 10-7 ± 2.3 × 10-8 vs 1.1 × 10-7 ± 2.0 × 10-8 S/cm, mean ± standard deviation, n = 4), whereas there was no significant change in ionic conductivity for CPEs with 5 μm particles. These observations -performed deliberately in the absence of charge-discharge cycles -show that repetitive mechanical stresses can play a significant role in altering the performance of CPEs, thereby revealing another possible mechanism for performance degradation in all-solid-state batteries.

"Biofeedback-based return to sport": individualization through objective assessments.

Elite athletes are regularly exposed to high and repetitive mechanical stresses and impacts, resulting in high injury rates. The consequences of injury can range from time lost from training and competition to chronic physical and psychological burden, with no guarantee that the athlete will return to preinjury levels of sport activity and performance. Prominent predictors include load management and previous injury, highlighting the importance of the postinjury period for effective return to sport (RTS). Currently, there is conflicting information on how to choose and assess the best reentry strategy. Treating RTS as a continuum, with controlled progression of training load and complexity, seems to provide benefits in this process. Furthermore, objectivity has been identified as a critical factor in improving the effectiveness of RTS. We propose that assessments derived from biomechanical measurements in functional settings can provide the objectivity needed for regular biofeedback cycles. These cycles should aim to identify weaknesses, customize the load, and inform on the status of RTS progress. This approach emphasizes individualization as the primary determinant of RTS and provides a solid foundation for achieving it.

Ultra-flexible semitransparent organic photovoltaics

Ultra-flexible organic photovoltaics (OPVs) are promising candidates for next-generation power sources owing to their low weight, transparency, and flexibility. However, obtaining ultra-flexibility under extreme repetitive mechanical stress while maintaining optical transparency remains challenging because of the intrinsic brittleness of transparent electrodes. Here, we introduce strain-durable ultra-flexible semitransparent OPVs with a thickness below 2 μm. The conformal surface coverage of nanoscale thin metal electrodes (< 10 nm) is achieved, resulting in extremely low flexural rigidity and high strain durability. In-depth optical and electrical analyses on ultrathin metal electrodes showed that the devices maintain over 73% of their initial efficiency after 1000 cycles of repetitive compression and release at 66% compressive strain, and the average visible light transmittances remain higher than 30%. To our knowledge, this is the first systematical study on mechanical behaviors of strain-durable ultra-flexible ST-OPVs through precise adjustment of each ultrathin electrode thickness toward the emergence of next-generation flexible power sources.

Diabetic Pedal Osteomyelitis and Its Treatment.

Diabetes is a fast-growing chronic metabolic disorder that is widely associated with foot ulcers. The major challenge among these ulcers is wound infections, altered inflammatory responses, and a lack of angiogenesis that can complicate limb amputation. The foot, because of its architecture, becomes the part most prone to complications and the infection rate is higher mainly between the toes due to the humid nature. Therefore, the infection rate is significantly higher. Wound healing in diabetes is a dynamic process usually delayed due to poor immune function. Diabetes-related pedal neuropathy and perfusion disturbances can lead to a loss of sensation in the foot. This neuropathy can further be a risk factor for ulcer development due to repetitive mechanical stress that later might get infected by the invasion of microorganisms extending to the bone and causing an infection called pedal osteomyelitis. This review details the pathophysiology, the biomaterials aiding in the infection cure and regeneration of bone along with their limitations, as well as their future prospects.

Intra-articular hyaluronic acid plus sorbitol injections for the management of severe glenohumeral osteoarthritis in a former female volleyball player

The glenohumeral joint is the third most common joint to be affected by osteoarthritis (OA). Practising volleyball can lead to shoulder arthritis due to repetitive mechanical stress on the shoulder joint. The first step of management of primary glenohumeral OA usually is the non-operative treatment, with intra-articular injections representing one of the most utilized treatments. The aim of this study is to report the outcomes of a series of three injections of hyaluronic acid (HA) plus sorbitol in a patient with severe glenohumeral OA. An 81-year-old female former volleyball player presented to our Rehabilitation Unit with more than 15 years history of shoulder pain and functional limitation. Since she refused to undergo surgery, we proposed her intra-articular injections of HA plus sorbitol. Outcome evaluation was made up to 12 months from the last injection by means of the Constant-Murley score and the Disability of the Arm, Shoulder and Hand questionnaire. Three injections of HA plus sorbitol for three weeks in a row in a patient with severe glenohumeral OA led to important improvements in pain reduction and better functionality at all follow-ups. Larger studies including more patients and with longer follow-ups are needed to confirm the consistency of these findings.

Piezoelectric Response and Substrate Effect of ZnO Nanowires for Mechanical Energy Harvesting in Internet-of-Things Applications

Recently, an unprecedented growth in the internet of things (IoT) is being observed, which is becoming the main driver for the entire semiconductor industry. Reliable maintenance and servicing of the IoT is becoming challenging, knowing that the IoT nodes outnumber the human population by a factor of seven. Energy harvesting (EH) can overcome those difficulties, delivering the energyautonomous IoT nodes to the market. EH converts natural or waste energies (vibrations, heat losses, air flows, light, etc.) into useful energy. This article explores the performance of ZnO nanowires under mechanical actuation to characterize their piezoelectric performance. ZnO nanowires were fabricated using ALD and a subsequent chemical bath growth. AISI 301 steel was used as a substrate of the EH device to better fit the mechanical requirements for the piezoelectric generator. We determined that a thin layer of another oxide below ZnO provides outstanding adhesion. The samples were submitted under repetitive mechanical stress in order to characterize the output piezovoltage for different conditions. They exhibited a piezoelectric signal which was stable after hundreds of actuations. This shows good promise for the use of our device based on ZnO, an Earth-abundant and non-toxic material, as an alternative to the conventional and popular but harmful and toxic PZT. The designed measurement setup demonstrated that a AISI 301 steel substrate coated with ZnO deposited by ALD and grown in a chemical bath has promising performance as a piezoelectric material. Characterized ZnO samples generate up to 80 nJ of energy during 55 s runs under matched load conditions, which is sufficient to supply a modern IoT node.

Management of lumbar spondylolysis in the adolescent athlete: a review of over 200 cases

BACKGROUNDSpondylolysis is a defect of the pars interarticularis of vertebrae, most commonly seen at L5 and L4. The etiology of spondylolysis and isthmic spondylolisthesis is generally considered to be a result of repetitive mechanical stress to the weak portion of the vertebrae. A higher incidence of spondylolysis is observed in young athletes. Symptomatic spondylolysis can be successfully treated conservatively, but there is currently a limited consensus on treatment modalities and a lack of large-scale clinical trials. PURPOSEThe purpose of the present study was to investigate the optimal treatment algorithm for symptomatic spondylolysis in adolescent athletes and evaluate the functional outcomes of those undergoing the nonoperative treatment. STUDY DESIGNA retrospective review. PATIENT SAMPLETwo hundred one adolescent patients ranging from age 10 to 19 involved in athletics OUTCOME MEASURESInjury characteristics (age, mechanism, time), sports played, bone stimulator use, bony healing at 3 months on computed tomography (CT) scans, return to sports, corticosteroid injection use. METHODSTwo hundred one adolescent athlete patients (62 females and 139 males) diagnosed with spondylolysis between 2007 and 2019 were retrospectively reviewed. Diagnosis was based on plain radiography followed by magnetic resonance imaging. All patients were treated conservatively with cessation of sports activity, thoracolumbosacral orthosis, and external bone stimulator for three months after diagnosis. CT scans were obtained for the 3-month follow-up visits to assess bony healing. Subsequently the patients received 6 weeks of rehabilitation focused on core strengthening. Symptomatic patients after the treatment were referred for steroid injections and continued with the rehabilitation protocol. RESULTSThe most common age of injury was 15 years old, following a strong normal distribution. The most commonly played sport was football, followed by baseball/softball. The primary mechanism of injury was weight training closely followed by a football injury. The first quarter of the calendar year had the highest incidence of injuries with the most injuries occurring in March and the least occurring in December. One hundred fifty-two athletes reported using bone stimulators as prescribed, and these patients showed a significantly higher rate of bony healing on follow-up CT scans than those who did not use bone stimulators. One hundred ninety-seven patients (98%) returned to sports or similar level of activities. Thirty-seven patients (18%) received facet or epidural steroid injections due to continued pain and one patient underwent a surgical procedure. Follow-up CT scans showed 49.8% bony healing. CONCLUSIONSConservative treatment of spondylolysis in adolescent athletes with cessation of sports, thoracolumbosacral orthosis, and bone stimulator followed by rehabilitation was associated with excellent outcomes in terms of return to sports.

Painful and oozing bullous lesions in a 74‐year‐old woman

Painful and oozing bullous lesions in a 74‐year‐old woman

Effect of U-Flex-to-Install and Dynamic U-Flexing on Li-Ion Battery State of Health Degradation Subjected to Varying Fold Orientations, Folding Speeds, Depths of Charge, C-Rates, and Temperatures

Abstract The demand for wearable consumer electronics, fitness accessories, and biomedical equipment has led to the growth research and development of thin flexible batteries. Wearable equipment and other asset monitoring applications require conformal installation of power sources on nonplanar surfaces. For power sources in wearable electronics, durability to sustain repetitive mechanical stresses induced by human body motion is paramount along with the usual desirable power source characteristics. Previous research documenting the reliability of statically and dynamically folded power sources is scarce and does not follow standardized test protocols. Particularly, the use of manual stressing for mechanical folding of the power sources instead of a mechanical test setup is a key shortcoming in existing literature. Data are lacking on battery life cycling and in situ mechanical stress-testing of the power sources including their impact of performance and reliability. This study aims to overcome these deficiencies by testing a commercial Li-ion power source under static as well as dynamic folding. Furthermore, the fold orientation and its fold speed are varied to evaluate the effect of different mechanical stress topologies on the power source. Finally, a regression model was developed to capture the effect of these use parameters on battery capacity degradation.

Graphene oxide incorporated flexible and free-standing PVDF/ZnO composite membrane for mechanical energy harvesting

Here we report the comparative study of mechanical energy harvesting properties of highly flexible, stretchable and free-standing poly (vinylidene fluoride) (PVDF) membranes loaded with various nanofillers like zinc oxide (ZnO), graphene oxide (GO) and ZnO/GO composites. Composite polymer membranes with dominating β-crystalline phase have been synthesized by effectively simpler and low-cost chemical synthesis method. The mechanical to electrical energy conversion is observed by measuring output voltage and current signal while repetitive mechanical stress is applied to the composite membranes in different modes like tapping, bending and stretching. Sufficient increment in open circuit voltage and short circuit current is observed in each mode of mechanical vibrations applied to both ZnO and GO loaded composite membranes compared to the pristine PVDF host matrix. The enhancement in output deliverable electrical power is attributed to the polar nature of ZnO and the formation of GO conduction network in composite membranes. The self-poled β-crystalline tri-phase PVDF/ZnO/GO composite membranes demonstrate the best energy harvesting performances among all the composites in each mode of mechanical stresses, making them suitable for flexible nanogenerators.

Electrical characteristics of flexible amorphous indium–tin–gallium–zinc oxide thin-film transistors under repetitive mechanical stress

In this study, we investigated the effect of repetitive mechanical stress on the electrical characteristics of amorphous indium–tin–gallium–zinc oxide (a-ITGZO) thin-film transistors (TFTs). The degradation of the electrical characteristics of an a-ITGZO TFT with a curvature radius of 2 mm is minimal even after the TFT undergoes bending 105 times. Our technology computer-aided design simulation reveals that the electrical characteristics degraded by the repeated bending cycles are due to the increase in the acceptor-like Gaussian states (N GA) related with the generation of oxygen interstitial defects.