Bending Of Film Research Articles

Bending of polymer films: a method for obtaining a compressive modulus of thin films.

Due to the advent of various foldable electric devices, it is becoming increasingly important to understand the bending properties of film materials. Bending of isotropic materials may be trivial if elastic deformation is small within a range of linear elasticity, which is often the case for bending. However, bending of polymer films, often used in recent foldable devices, may not be the case. Polymer films are frequently fabricated with stretching, which induces anisotropic orientation of molecular chains. In addition, there are many studies on bimodulus materials, which suggest the importance of the difference in tensile and compressive elastic moduli, i.e., the importance of elastic asymmetry, considering that bending involves compression and extension. In this study, we extended the standard linear elastic theory to include elastic anisotropy and elastic asymmetry and developed a method for obtaining compressive moduli of films, which cannot be obtained by a simple compression test because thin films under compression buckle at small strains. Our method is based on a bending test combined with a uniaxial tension test, which allows the measurement of Poisson's ratio in addition to Young's modulus, which are both anisotropic and asymmetric. To test our theory and method, we further performed experiments on biaxially stretched poly(ethylene terephthalate) (PET) films. As a result, we found non-negligible anisotropy in Poisson's ratio and non-negligible asymmetry (bimodulus) in tensile and compressive moduli. We further justify our framework by demonstrating a clear data collapse to show agreement between experiment and theory, clarifying limitations. Our results suggest the importance of elastic anisotropy and elastic asymmetry in bending of industrial films and give fundamental knowledge on this subject, which would be useful for applications. Such applications include the control of the position of the neutral plane and precise measurements of elastic moduli and Poisson's ratio, which are crucial, e.g., for the development of tough flexible electric devices and for the structural designs using compliant mechanisms.

Severe Rigid Scoliosis Deformity Correction Using Extended Posterior Release and Instrumentation: A Retrospective Study.

Sever rigid scoliotic deformity (magnitude of the curve >80° and <25% correction on bending film) correction is a great challenge to spine surgeons. Severe scoliosis when untreated or not treated properly, may lead to severe complications due to curve progression. The aim of operative management is to achieve significant correction of sagittal, coronal, and rotational deformity to avoid neurodeficit, maintain sagittal balance, and improve cardiopulmonary function. In this retrospective study, eight patients with severe rigid scoliosis who underwent through single-staged extended posterior release and spinal fusion between March 2022 and November 2023. The surgical procedures were the excision of the posterior ligament and spinous process, laminectomy, excision of ligament flavum, facetectomy, and posterior spinal fusion utilizing pedicle screws, rods, and sub-laminar wires. Patients were evaluated radiologically using posteroanterior and lateral X-rays of the whole spine and computed tomography scans. Demographic data, pre- and post-operative cobbs angle, osteotomized segment, instrumentation segments, blood loss, operation duration, follow-up duration, and complications were recorded. Pre-operative mean cobbs angle was 94.1° (range 83-110°) and post-operative mean cobbs angle was 33.3° (range 28-42°) with 64.6% scoliosis correction. The mean estimated blood loss was 517 mL (range 300-580 mL). The mean operation duration was 272.5 min (210-340 min). Mean spinal fixation fusion segments were 11.1 (range 8-14). No major complications were noted. Our study concluded that extended posterior-only release, facetectomy, and posterior spinal fusion by utilizing pedicle screws and pre-contoured rods significantly corrected severe and rigid scoliosis with a high correction rate and avoid complications of anterior release. Hence, we can achieve remarkable correction in rigid scoliosis using the proper choice of levels, proper implant, and extended posterior release.

Exploring cyclic olefin copolymer (COC) for flexible silver nanowire electrode

The development of flexible electronic devices has been a primary focus in various fields, and silver nanowire (Ag NW) networks show significant promise due to their unique electrical and mechanical properties. However, achieving well-defined and stable nanowire coatings on polymer substrates remains challenging. This work presents a novel and simple approach for directly coating Ag NWs on cyclic olefin copolymer (COC) substrates utilizing ultraviolet/ozone (UVO) treatment, a method not previously demonstrated for this specific material system up to our knowledge. The compatibility of this approach with COC eliminates the need for complex pre- and post-treatment processes, making it a more straightforward and environmentally friendly way to improve adhesion between Ag NWs and COC. The Ag NWs/COC electrodes exhibited excellent optoelectrical performance, with a high optical transmittance of 84% and a low sheet resistance of 13 Ω/sq—metrics that compare favorably to industry standards for transparent conductive films. Additionally, the Ag NWs/COC electrodes displayed excellent mechanical stability, showing no changes in sheet resistance after both tape adhesion and film bending tests. The novelty of the presented Ag NW-COC system, combined with the simplicity and environmental benefits of the UVO coating approach, as well as the demonstrated performance and stability of the resulting electrodes, make this work a significant advancement towards realizing the commercial potential of flexible electronics for biocompatible and wearable device applications.

Collective control of a vortex array in a ferroelectric ultrathin film

Recently, the observation of ferroelectric vortex arrays has triggered the investigation of topological domain structures and their characteristics. Vortices are typical topological domain structures with chirality in nanoscale ferroelectric materials. The chirality of a single vortex in a nanodot can be easily manipulated, but the collective control of a vortex array is exceptionally difficult and has not yet been realized. This Letter proposes an effective scheme for the collective control of a vortex array and investigates it via phase-field simulations. The results indicate that the collective control of a vortex array with bidirectional switching can be realized by introducing a bending film with periodic large curvatures under alternative electric fields. Furthermore, a general rule for determining the electrically controllable chirality of ferroelectric vortices is proposed. This Letter demonstrates the feasibility of the collective control of vortex arrays and provides insights for developing ferroelectric nanoelectronic devices based on vortex arrays.

Radiological and Pulmonary Results of Surgical Treatment of Severe Idiopathic Scoliosis Using Preoperative Halo Gravity Traction Compared with Less Invasive Temporary Internal Distraction in Staged Surgery in Adolescents.

Background: Severe and rigid scoliosis represents a type of spinal deformity characterized by a Cobb angle exceeding 90° and a flexibility of less than 30%. Halo spinal traction remains the established standard for managing severe scoliosis, although alternative approaches such as temporary internal distraction rods and staged surgical correction exist. The primary objective of this investigation was to compare two cohorts of patients treated using these distinct methods to ascertain any divergences in terms of surgical and radiological outcomes, pulmonary function (PF), and quality of life (QoL). Methods: This study encompassed a total of 62 pediatric patients meeting the specified criteria, which included severe idiopathic scoliosis (major Cobb curve >90) and flexibility <30%. Group 1 (G1) underwent surgical intervention involving preoperative Halo gravity traction (HGT) succeeded by posterior spinal fusion (PSF). On the other hand, Group 2 (G2) underwent a two-stage procedure starting with a less invasive temporary internal distraction technique (LITID) prior to PSF. The radiological outcomes, PF, and QoL were documented and assessed over a monitoring period ranging from 2 to 5 years. Results: The average preoperative major curves (MCs) measured 124° and 122° in G1 and G2, respectively (p < 0.426). Initial flexibility, as observed in preoperative bending films, ranged from 18% in G1 to 21% in G2 (p < 0.001). Following the ultimate surgical intervention, the MCs were corrected to 45° and 37.4° in G1 and G2, respectively (p < 0.001). The percentage correction of the MCs was higher in G2 (63% vs. 70% in G1 and G2, respectively), with significant between-group disparities (p < 0.001). The mean preoperative thoracic kyphoses (TKs) were 96.5° in G1 and 92° in G2 (p = 0.782), which were rectified to 45.8° in G1 and 36.2° in G2 (p < 0.001), equating to correction rates of 55% and 60% in the respective groups. Initially, G2 exhibited lower values for the percentage of predicted lung volume (FVC) and predicted FEV1 compared with G1 (49% and 58% vs. 54.5% and 60.8%; N.S.). Nonetheless, both groups demonstrated enhancements in their FVC and FEV1 values over the follow-up period. Conclusions: The surgical management of severe and untreated spinal curvatures in the pediatric and adolescent population can be considered safe, with a tolerable incidence of minor complications. LITID emerges as a method offering improved QoL and pulmonary function, achieving notably substantial average corrections in deformity by 70% in the coronal plane and 60% in the sagittal plane, alongside a mean increase in trunk height of 10.8 cm. Furthermore, a typical reduction of 76% in rib humps and enhancements in respiratory function, as indicated by improvements in 1 s predicted forced expiratory volume (by 25-56%) and forced vital capacity (by 35-65%), were achieved, leading to a clinically and statistically significant enhancement in QoL when evaluated using SRS-22r, without resorting to more radical, high-risk procedures.

Mechanisms and control of bending of monocrystalline and polycrystalline films by gallium ion irradiation

The ion beam-induced bending of thin metal films represents a potent technique for fabricating three-dimensional structures using focused ion beam technology. This technique exhibits significant potential in the realm of micro and nano-scale structure fabrication for applications in various novel devices, such as plasmonic detectors. However, achieving greater control is imperative to ensure the reproducible fabrication of intricate structures. Here, we investigate mechanisms of bending and their dependence on conditions using molecular dynamics (MD) simulations for both monocrystalline and polycrystalline gold films. Our findings reveal the distinct differences in the bending behaviors between monocrystalline and polycrystalline films, as well as the significant dependence of bending on irradiation conditions that can be utilized for control purposes. The results show that mass transports are associated with defect formation and migrations, as well as migration of grain boundaries in the polycrystalline case, which play key roles. We observe a slow initial stage of film bending by following the commencement of irradiation, which is attributed to non-uniform stress fields from non-uniform defect generation; however, mass transport becomes increasingly important at higher doses. There is a strong interplay between this mass transport and grain boundaries, leading to differences in the behavior of monocrystalline and polycrystalline films.

FORMATION OF FUNCTIONAL AND TECHNOLOGICAL PROPERTIES OF THE FILM FROM INTESTINAL RAW MATERIALS DURING THE DRYING PROCESS

The purpose of the research is formation of the functional and technological properties of a multi-purpose film from intestinal raw materials during drying. Its hygroscopic properties after drying at temperatures ranging from 40 to 70°C were studied. It was established that the increase of the drying temperature leads to the decrease in the amount of moisture that the sample absorbs from the environment. Ranges of relative air humidity at which it is possible to store dried products in vapor-permeable packaging have been determined. It is noted that the storage of the multifunctional film is possible in a vapor-tight package with an increase in air humidity relative to the recommended ranges. The operations of packing dried film and making sausage casings from it, which follow after drying operation, are described. It was noted, that during these operations there are mechanical deformations of the film bending at angles up to 180°. It was established, that there is no violation of the integrity of the film, provided that it is bent to an angle of 180° during the packaging of finished products and the production of sausage casings from it. The integrity of the manufactured casings after their recovery during the production of sausage products has been proven. The elastic-plastic properties of the intestinal raw material film obtained at different drying temperatures were investigated. It was found, that strength of the film increases and its plasticity decreases in case of increasing the drying temperature. It is noted that, from the point of view of strength, the highest drying temperature from the range of 40–70°С. From the point of view of plastic properties, the minimum temperature should be chosen from the specified range. Studies of the drying process of a wet multifunctional film from intestinal raw materials have determined the rational values of the temperature and duration of the its drying. It is noted that during the selection of the drying temperature in the technology of obtaining a multifunctional film from intestinal raw materials, the determining factor is the functional and technological properties of the obtained semi-finished product, which depend on the drying temperature.

Giant Flexoelectricity in Bent Semiconductor Thinfilm.

We elucidate the flexoelectricity of semiconductors in the high strain gradient regime, the underlying mechanism of which is less understood. By using the generalized Bloch theorem, we uncover a strong flexoelectric-like effect in bent thinfilms of Si and Ge due to a high-strain-gradient-induced band gap closure. We show that an unusual type-II band alignment is formed between the compressed and elongated sides of the bent film. Therefore, upon the band gap closure, electrons transfer from the compressed side to the elongated side to reach the thermodynamic equilibrium, leading to a pronounced change of polarization along the film thickness dimension. The obtained transverse flexoelectric coefficients are unexpectedly high with a quadratic dependence on the film thickness. This new mechanism is extendable to other semiconductor materials with moderate energy gaps. Our findings have important implications for the future applications of flexoelectricity in semiconductor materials.

Polymer-Entangled Spontaneous Pseudo-Planar Heterojunction for Constructing Efficient Flexible Organic Solar Cells.

Flexible organic solar cells (FOSCs) have attracted considerable attention from researchers as promising portable power sources for wearable electronic devices. However, insufficient power conversion efficiency (PCE), intrinsic stretchability, and mechanical stability of FOSCs remain severe obstacles to their application. Herein, an entangled strategy is proposed for the synergistic optimization of PCE and mechanical properties of FOSCs through green sequential printing combined with polymer-induced spontaneous gradient heterojunction phase separation morphology. Impressively, the toughened-pseudo-planar heterojunction (Toughened-PPHJ) film exhibits excellent tensile properties with a crack onset strain (COS) of 11.0%, twice that of the reference bulk heterojunction (BHJ) film (5.5%), which is among the highest values reported for the state-of-the-art polymer/small molecule-based systems. Finite element simulation of stress distribution during film bending confirms that Toughened-PPHJ film can release residual stress well. Therefore, this optimal device shows a high PCE (18.16%) with enhanced (short-circuit current density) JSC and suppressed energy loss, which is a significant improvement over the conventional BHJ device (16.99%). Finally, the 1cm2 flexible Toughened-PPHJ device retains more than 92% of its initial PCE (13.3%) after 1000 bending cycles. This work provides a feasible guiding idea for future flexible portable power supplies.

Harnessing strong and asymmetric adhesion by combining film heterogeneity and substrate morphology

We use a combined theoretical and experimental approach to investigate the quasi-static peeling behaviors of heterogeneous films from corrugated substrates. The heterogeneity is involved in films through two different methods, i.e., local stiffening and kirigami patterning, and the substrate surface is assumed to adopt a sinusoidal profile. Our results show that the spatial variation in film's bending stiffness, caused by the elastic heterogeneity with period form, can significantly enhance the peak peel force and give rise to asymmetric adhesion performance. The substrate's roughness can further amplify such adhesion enhancement and asymmetry by affecting the local peel angle at the peel front. The adhesion performance depends sensitively on the relative position between the heterogeneous films and corrugated substrates, and our results show that a combination of film heterogeneity and substrate undulation can enhance the adhesive strength by more than 100 times, compared with the case of homogeneous film and flat substrate. This study provides a theoretical framework to reveal multiple peeling mechanisms in the problem and can guide the design of film-substrate systems with tunable and anisotropic adhesion.

Surgical Treatment of Adolescent Idiopathic Scoliosis with the ApiFix Minimal Invasive Dynamic Correction System-A Preliminary Report of a 24-Month Follow-Up.

Adolescent idiopathic scoliosis (AIS) is a three-dimensional growth disorder. Corrective surgical procedures are the recommended treatment option for a thoracic angle exceeding 50° and a lumbar major curve of 40°. Over the past few years, dynamic growth modulation implants have been developed as alternatives to permanent fusion. The ApiFix system was designed as a 2D "posterior dynamic device" for curve correction. After implantation in a minimally invasive procedure, it uses polyaxial joints and a self-adjusting rod to preserve the degree of motion and to accommodate the patient's growth. It provides an effective method of controlling deformity and fills the gap between the conservative treatment of major curves that are >35° and the fusion procedure. The objective of the two-center cohort study was the analysis of the correction results of patients, who underwent surgical intervention with the ApiFix system. The inclusion criteria were AIS, Lenke type 1 or type 5, a major curve on bending films of ≤30°, and an angle of the major curve of between 35° and 60°. Postoperative radiograph data were obtained longitudinally for up to 24 months of follow-up and compared to preoperative (preop) values. For comparisons of the different time points, non-parametric tests (Wilcoxon) or paired t-tests for normally distributed values were used to analyze repeated measures. Overall, 36 patients (25 female and 11 male) were treated with the ApiFix system from April 2018 to October 2020. Lenke type 1 was identified in 21 (58%) cases and Lenke type 5 was identified in 15 (42%) cases. The average angle of the thoracic major curve for Lenke 1 was 43°. The preoperative lumbar major curve (Lenke 5) was determined to be 43°. Over a follow-up of 24 months, a correction of the major curve to an average of 20° was observed for Lenke 1 and that to an average of 15° was observed for Lenke 5. Lenke type 1 and type 5 showed significant changes in the major curve over the individual test intervals in the paired comparisons compared to the starting angle (Lenke 1: preop-24 months, 0.002; Lenke 5: preop-24 months, 0.043). Overall, 11 events were recorded in the follow-up period, that required revision surgery. We distinguished between repeated interventions required after reaching the maximum distraction length of the implant due to the continued growth of the patient (n = 4) and complications, such as infections or problems associated with the anchorage of the implant (n = 7). The results from the present cohort revealed a statistically significant improvement in the postoperatively measured angles of the major and minor curves in the follow-up after 24 months. Consequently, the results were comparable to those of the already established vertebral body tethering method. Alignment in AIS via dynamic correction systems in combination with a possible growth modulation has been a treatment alternative to surgical fusing procedures for more than a decade. However, the long-term corrective effect has to be validated in further studies.

How well do we assess the adequacy of bending films in scoliosis?

To determine whether side-bending films in scoliosis are assessed for adequacy in clinical practice; and to introduce a novel method for doing so. Six surgeons and eight radiographers were invited to participate in four online surveys. The generic survey comprised erect and left and right bending radiographs of eight individuals with scoliosis, with an average age of 14.6 years. Respondents were asked to indicate whether each bending film was optimal (adequate) or suboptimal. In the first survey, they were also asked if they currently assessed the adequacy of bending films. A similar second survey was sent out two weeks later, using the same eight cases but in a different order. In the third survey, a guide for assessing bending film adequacy was attached along with the radiographs to introduce the novel T1-45B method, in which the upper endplate of T1 must tilt ≥ 45° from baseline for the study to be considered optimal. A fourth and final survey was subsequently conducted for confirmation. Overall, 12 (86%) of 14 respondents did not use any criteria to assess the bending film adequacy; the remaining two each described a different invalidated method. In total, 12 (86%) of the respondents felt T1-45B was easy to learn and apply. There was fair to substantial intra-rater reliability (k = 0.25 to 0.88) which improved to fair to almost perfect (k = 0.38 to 0.88) post-introduction of the guide. Inter-rater reliability varied considerably among the rater groups but similarly increased following introduction of the guide (kS1 = 0.19 to 0.34, kS2 = 0.33 to 0.43 vs kS3 = 0.49 to 0.5, kS4 = 0.35 to 0.43). Many surgeons and radiographers do not assess spinal bending films for adequacy. We propose that the change in the plane of the upper endplate of T1 on side-bending can be used in this evaluation. In the T1-45B method, a change of ≥ 45° on side bending qualifies as an adequate bend effort.

Highly hydrostable and flexible opal photonic crystal film for enhanced up-conversion fluorescence sensor of COVID-19 antibody

Efficient detection of related markers is significant for the early screening of COVID-19. Near infrared (NIR) light excited up-conversion fluorescence probes are ideal for biosensing but limited by the low luminescence efficiency. In this work, a novel highly stable opal photonic crystal (OPC) structure was designed to provide an OPC effect for up-conversion fluorescence enhancement, and sensitive Novel Coronavirus IgG up-conversion FRET-based sensor was further constructed. For the problems of water stability and mechanical stability of polymer OPC which cannot be solved for a long time, polymer spray combined with a flipped OPC film strategy is presented. Fragmented size OPC film was firmly fixed by polymer modification layer, which gave large size OPC film great water stability, mechanical stability and bending performance without affecting the fluorescence enhancement property. On this basis, the up-conversion emission intensity was enhanced significantly, and fluorescence resonant energy transfer (FRET) based Novel Coronavirus IgG antibody sensor was constructed. Monolayer up-conversion nanoparticles (UCNPs) on the surface of the polydopamine (PDA)/OPC film can make the fluorescent signal more sensitive, and effectively reduce the detection limit. The test device integrating NIR excitation and mobile phone realized the visual fast detection, showing remarkable sensing performance for COVID-19 antibodies with the limit of detection (LOD) of 0.1 ng mL−1. This detection platform will provide a more effective tool for early detection of the novel coronavirus.

Stress Analysis of Large Diameter Pipe Interface Structure of Boiler Main Steam Pipe

The “four tubes” safety of the boiler is related to the economic and safe operation of the boiler. In order to ensure the safety of boiler steam pipe large diameter nozzle welding place, the structural stress analysis of the special large-aperture nozzle pipeline designed in a boiler enterprise's design process is studied in this paper. In the case, the allowable angle of the pipeline exceeds the direct calculation range of JB4732-1995, therefore, the ANSYS finite element analysis method is used to calculate the structural stress of the pipeline, and the stress evaluation is carried out. The results show that the finite element method can effectively calculate the pipeline structure's stress calculation. In order to meet the requirements of JB 4732-1995 for the evaluation of various types of stress intensity step by step, the film bending stress is treated as S<SUB>III</SUB>, and the conservative treatment is controlled by 1.5Sm, therefore, the finite element analysis results of the pipeline show that the maximum equivalent stress is 176.22 MPa, which is located at the connection between the large nozzle and the main pipe, and the larger the diameter of the pipe nozzle, the higher the equivalent stress. The stress evaluation results of the pipeline are evaluated according to the third stress intensity, and the strength of the analyzed parts meets the standard requirements.

Effect of Phenoxyethanol and Sodium benzoate on the liquid crystal phase behavior of mixed surfactant system

Surfactants in a mixed concentrated (∼30 wt% and higher)-surfactant system self-assemble to form a variety of liquid crystal (lc) types depending the lc curvature determined by the surfactant chemistries and their relative compositions. Preservatives, fragrances and other minor additives present in an industrial formulation can either incorporate into the lc and/or influence the aqueous phase ionic strength to alter the spatial arrangements of the surfactants and the lc curvature. These mechanisms could additively or competitively determine the lc curvature and thereby the lc types formed. We report on the mechanisms for preservatives Phenoxyethanol (PE) and Sodium benzoate (NaB) governing the lc phase behavior for a mixed concentrated-surfactant system: 16 wt% zwitterionic Cocoamidopropyl betaine (CAPB), and 7 wt% each of anionic Sodium Lauroyl isethionate (SLI), Sodium Methyl Lauroyl Taurate (SMLT), and 6 wt% Lauric acid. The lc type(s), the lc dimensions including inter-lc distances were derived from SAXS and polarized microscopy images. The predominant lc phase without preservatives was H1lc, while anionic SLI and SLMT present in excess were insoluble to form dispersed crystals. The addition of PE molecules resulted in their incorporation in the lc surfactant film to cause a transition to micelles, and Lα lc due to incorporation-induced flattening of the film. NaB molecules prevented micelles formation and preserved the H1lc by serving as a hydrotropic agent. The NOESY spectra for the lc systems with PE or NaB at 0–3 wt% confirmed incorporation of PE in surfactant film as opposed to NaB. For both PE and NaB present in a lc system, the dominance of hydrotropic nature of NaB causing film bending rather than the film flattening effect of PE at low (∼1 wt%) PE levels resulted in H1lc as the predominant phase, and reduced dominance of film bending effect at a high PE level (≥ 2 wt%) led to the formation of Lα lc.

Study of the Power Generation Performance of Impact Piezoelectric Energy Capture Devices.

In order to solve the problem of conventional energy shortages, a non-resonant impact piezoelectric energy capture device using a (polyvinylidene fluoride) piezoelectric film at low frequency is proposed, and related theoretical analysis and experimental studies are conducted. The device has a simple internal structure, is green and easy to miniaturize, and is capable of harvesting energy at low frequencies to supply energy to micro and small electronic devices. First, to verify the feasibility of the device, the structure of the experimental device is modeled and dynamically analyzed. Then the modal, stress-strain, and output voltage of the piezoelectric film are simulated and analyzed using COMSOL Multiphysics simulation software. Finally, the experimental prototype is built according to the model, and the experimental platform is constructed to test the relevant performance. The experimental results show that the output power produced by the capturer varies within a certain range when the capturer is excited externally. With an external excitation force of 30 N, a piezoelectric film bending amplitude of 60°, and a piezoelectric film size of 45 × 80 mm, the resulting output power voltage is 21.69 V, the output current is 0.07 mA, and the output power is 1.5176 mW. This experiment verifies the feasibility of the energy capturer and provides a new idea for powering electronic components.

A Flexible Strain Sensor with High Electrical Conductivity, Rapid Electrothermal Response, and High Strain Sensitivity for Real‐Time Monitoring of Human Joint Movement

AbstractHerein, a flexible film, called PPA film, is designed as a multifunctional sensor with high electrical conductivity, rapid electrothermal response, and high strain sensitivity. The film contains polyvinyl alcohol (PVA), graphene nanosheets (GNs), nanocellulose crystals (CNCs), polydopamine (PDA), and silver nanoparticles (Ag NPs), symbolized as PPA film. The CNCs enhance the dispersion of the GNs during film formation; the stacked GNs change heat conduction and resistance during film bending; PDA serves as a linking agent; Ag NPs improve the conductivity (i.e., 2.65 × 103 S/m) of the film during electrothermal response measurement. A flexible strain sensor designed from PPA films is mounted on the skin surface of human joints to monitor human movement in real time. The sensor exhibited good stability and cycling durability, i.e., the resistance variation remained stable during the bend‐release repetitions for 600 cycles at 1.2 % strain. The flexible sensors exhibited highly sensitive to bending strain, i.e., 30.5 of the gauge factor (GF), and can be applied to monitor bending motions of human joints, such as finger, wrist, elbow, and knee joints.In addition, the PPA films exhibit very high joule heat generation ability and demonstrate its applicability as a joint or stomach warmer and sensor. The as‐designed flexible sensor is a promising candidate for application in environmentally friendly and multifunctional wearable devices.

Aluminum Nitride Based Film Bulk Acoustic Resonator With Anchor Column Structure

In order to reduce the lateral acoustic energy loss of thin film bulk acoustic resonators (FBARs), the trench structure for FBAR is generally designed to block the leakage of acoustic wave and help improving the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> -factor. One method the designers often used is etching the piezoelectric material around the active area of the FBAR to form the air-wall structure as a perfect reflection boundary condition. In this paper, the FBAR with trench structure is fabricated. The multilayer films in the FBAR with trench structure are easily warped due to excessive compressive stress. The numerical analysis and finite element simulation are used to verify the effects of different stresses on the devices. In order to avoid the degradation of FBAR performance caused by film warpage, the FBAR with anchor columns is proposed. The anchor columns are located on both sides of the FBAR, and they are designed to reduce film bending and the compressive stress of active area of the resonator. The measured results show that the Qs and Qp of the FBAR with anchor columns are increased by 55.8% and 21.1%, respectively, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k_{eff}{}^{2}$ </tex-math></inline-formula> improved from 5.6% to 6.7% compared with the FBAR without the anchor columns. [2022-0179]

Positive and Negative Changes in the Electrical Conductance Related to Hybrid Filler Distribution Gradient in Composite Flexible Thermoelectric Films Subjected to Bending

P-type multiwalled carbon nanotubes (MWCNTs), as well as heterostructures fabricated by direct deposition of inorganic thermoelectric materials as antimony and bismuth chalcogenides on MWCNT networks are known as perspective materials for application in flexible thermoelectric polymer-based composites. In this work, the electrical response of three types of Sb2Te3-MWCNT heterostructures-based flexible films-free standing on a flexible substrate, encapsulated in polydimethylsiloxane (PDMS), and mixed in polyvinyl alcohol (PVA) is studied in comparison with the flexible films prepared by the same methods using bare MWCNTs. The electrical conductance of these films when each side of it was subsequently subjected to compressive and tensile stress during the film bending down to a 3 mm radius is investigated in relation to the distribution gradient of Sb2Te3-MWCNT heterostructures or bare MWCNTs within the film. It is found that all investigated Sb2Te3-MWCNT films exhibit a reversible increase in the conductance in response to the compressive stress of the film side with the highest filler concentration and its decrease in response to the tensile stress. In contrast, free-standing and encapsulated bare MWCNT networks with uniform distribution of nanotubes showed a decrease in the conductance irrelevant to the bending direction. In turn, the samples with the gradient distribution of the MWCNTs, prepared by mixing the MWCNTs with PVA, revealed behavior that is similar to the Sb2Te3-MWCNT heterostructures-based films. The analysis of the processes impacting the changes in the conductance of the Sb2Te3-MWCNT heterostructures and bare MWCNTs is performed. The proposed in this work bending method can be applied for the control of the uniformity of distribution of components in heterostructures and fillers in polymer-based composites.

The Efficacy of a Posterior Approach to Surgical Correction for Neglected Idiopathic Scoliosis: A Comparative Analysis According to Health-Related Quality of Life, Pulmonary Function, Back Pain and Sexual Function

This study aimed to evaluate the treatment outcomes of severe idiopathic scoliosis (IS) and hypothesized that surgical treatment would have a superior impact on the health-related quality of life (HRQoL), pulmonary function (PF), back pain, and sexual function. We retrospectively reviewed 195 consecutive patients with IS classified into severe (SG) and moderate groups (MG) with a minimum follow-up of two years. The mean preoperative curve was 131° and 60° in the SG and MG, respectively. The mean preoperative flexibility in the bending films averaged between 22% in the SG and 41% in the MG. After definitive surgery, the main curve was corrected to 61° and 18° in the SG and MG, respectively. The mean preoperative thoracic kyphosis was 83° in the SG and 25° in the MG, which was corrected to 35° in the SG and 25° in the MG. At baseline, the percentage of predicted lung volume (FVC) was significantly lower in the SG than that in the MG (51.2% vs. 83%). The baseline percentage of the predicted FEV1 values was also significantly lower in the SG than in the MG (60.8% vs. 77%). During the two-year follow-up, the percentage of predicted FVC showed significant improvement in the SG (69.9%) (p < 0.001), and the percentage of predicted FEV1 values during the follow-up improved significantly in the SG (76.9%) (p < 0.001) compared with the MG (81%), with no statistical difference observed during the two-year follow-up. The SRS-22r showed a clinically and statistically significant improvement in the preoperative results to those of the final follow-up (p < 0.001). Surgical treatment of severe scoliosis can be safe. It provided a mean correction of the deformity for 59% of patients and significantly improved respiratory function, with the percentage of predicted forced expiratory volume in 1 s improving by 60% and the forced vital capacity improving by 50%, resulting in clinically and statistically significant improvements in the SRS-22r, HRQoL outcome scores, and back pain (reduced from 36% to 8%), as well as improved sexual function. The planned surgical treatment can achieve a very significant deformity correction with a minimal risk of complications. The surgical treatment has a superior impact on the quality of life patients with severe spinal deformities and significantly improves function in every sphere of life.