Lead zirconate titanate ceramics with aligned crystallite grains.

The piezoelectric properties of lead zirconate titanate [Pb(Zr,Ti)O3 or PZT] ceramics could be enhanced by fabricating textured ceramics that would align the crystal grains along specific orientations. We present a seed-passivated texturing process to fabricate textured PZT ceramics by using newly developed Ba(Zr,Ti)O3 microplatelet templates. This process not only ensures the template-induced grain growth in titanium-rich PZT layers but also facilitates desired composition through interlayer diffusion of zirconium and titanium. We successfully prepared textured PZT ceramics with outstanding properties, including Curie temperatures of 360°C, piezoelectric coefficients d33 of 760 picocoulombs per newton and g33 of 100 millivolt meters per newton, and electromechanical couplings k33 of 0.85. This study addresses the challenge of fabricating textured rhombohedral PZT ceramics by suppressing the otherwise severe chemical reaction between PZT powder and titanate templates.

Mechanically Activated Solid-State Radical Polymerization and Cross-Linking via Piezocatalysis.

Piezocatalysis offers a means to transduce mechanical energy into chemical potential, harnessing physical force to drive redox reactions. Working in the solid state, we show here that piezoelectric BaTiO3 nanoparticles can transduce mechanical load into a flux of reactive radical species capable of initiating solid state free radical polymerization. Activation of a BaTiO3 powder by ball milling, striking with a hammer, or repeated compressive loading generates highly reactive hydroxyl radicals (⋅OH), which readily initiate radical chain growth and crosslinking of solid acrylamide, acrylate, methacrylate and styrenic monomers. Control experiments indicate a critical role for chemisorbed water on the BaTiO3 nanoparticle surface, which is oxidized to ⋅OH via mechanoredox catalysis. The force-induced production of radicals by compressing dry piezoelectric materials represents a promising new route to harness mechanical energy for solid state radical synthesis.

Magnetic prestressing for a d32-mode single crystal ultrasonic transducer.

This work describes a 35.9 kHz ultrasonic transducer that incorporates a magnetic arrangement to apply a static-compressive prestress to a d32-mode relaxor ferroelectric single crystal drive-element. The magnetic arrangement produces a 22.5 N static-compressive force, inducing a static compression of ∼630 nm on the drive-element. Operating in air with a continuous-wave 10 V peak drive at ∼35.9 kHz, the measured resonant peak displacement of the transducers head-mass was 127 nm. This is well within the predicted static compression, thus, the drive-element is protected from damaging tensile stress. Under the same drive conditions and at an axial distance of 10 mm from the face of the head-mass, the measured acoustic pressure was ∼12 Pa. Analytical and finite element model predictions and the measured behaviour of a prototype device are presented and show good correlation, demonstrating that magnetic prestressing of the drive-element can be a viable alternative to the traditional bolt-clamp.

Management of Maxillofacial Gunshot Injuries With Emphasis on Damage Control Surgery During the Yemen Civil War. Review of 173 Victims From a Level 1 Trauma Hospital in Najran, Kingdom of Saudi Arabia.

Study Design: Studies on the concept of Damage Control Surgery (DCS) in the management of firearm injuries to the oral and maxillofacial region are still scarce, hence the basis for the current study. Objectives: The objectives of the current study is to share our experience in the management of maxillofacial gunshot injuries with emphasis on DCS and early definitive surgery. Methods: This was a retrospective study of combatant Yemeni patients with maxillofacial injuries who were transferred across the border from Yemen to Najran, Kingdom of Saudi Arabia. Demographics and etiology of injuries were stored. Paths of entry and exit of the projectiles were also noted. Also recorded were types of gunshot injury and treatment protocols adopted. Data was stored and analyzed using IBM SPSS Statistics for Windows Version 25 (Armonk, NY: IBM Corp). Results: A total of 408 victims, all males, were seen during the study period with 173 (42.4%) males sustaining gunshot injuries to the maxillofacial region. Their ages ranged from 21 to 56 years with mean ± SD (27.5 ± 7.6) years. One hundred and twenty-one (70.0%) victims had extraoral bullet entry, while 53 (30.0%) victims had intraoral entry route. Ocular injuries, consisting of 25 (14.5%) cases of ruptured globe and 6 (3.5%) cases of corneal injuries, were the most commonly associated injuries. A total of 78 (45.1%) hemodynamically unstable victims had DCS as the adopted treatment protocol while early definitive surgery was carried out in 47(27.2%) hemodynamically stable victims. ORIF was the treatment modality used for the fractures in 132 (76.3%) of the victims. Conclusions: We observed that 42.4% of the war victims sustained gunshot injuries. DCS with ORIF was the main treatment protocol adopted in the management of the hemodynamically unstable patients.

A Deep Learning Framework for Automatic Meal Detection and Estimation in Artificial Pancreas Systems.

Current artificial pancreas (AP) systems are hybrid closed-loop systems that require manual meal announcements to manage postprandial glucose control effectively. This poses a cognitive burden and challenge to users with T1D since this relies on frequent user engagement to maintain tight glucose control. In order to move towards fully automated closed-loop glucose control, we propose an algorithm based on a deep learning framework that performs multitask quantile regression, for both meal detection and carbohydrate estimation. Our proposed method is evaluated in silico on 10 adult subjects from the UVa/Padova simulator with a Bio-inspired Artificial Pancreas (BiAP) control algorithm over a 2 month period. Three different configurations of the AP are evaluated -BiAP without meal announcement (BiAP-NMA), BiAP with meal announcement (BiAP-MA), and BiAP with meal detection (BiAP-MD). We present results showing an improvement of BiAP-MD over BiAP-NMA, demonstrating 144.5 ± 6.8 mg/dL mean blood glucose level (-4.4 mg/dL, p< 0.01) and 77.8 ± 6.3% mean time between 70 and 180 mg/dL (+3.9%, p< 0.001). This improvement in control is realised without a significant increase in mean in hypoglycaemia (+0.1%, p= 0.4). In terms of detection of meals and snacks, the proposed method on average achieves 93% precision and 76% recall with a detection delay time of 38 ± 15 min (92% precision, 92% recall, and 37 min detection time for meals only). Furthermore, BiAP-MD handles hypoglycaemia better than BiAP-MA based on CVGA assessment with fewer control errors (10% vs. 20%). This study suggests that multitask quantile regression can improve the capability of AP systems for postprandial glucose control without increasing hypoglycaemia.

A Multitask Learning Approach to Personalized Blood Glucose Prediction.

Blood glucose prediction algorithms are key tools in the development of decision support systems and closed-loop insulin delivery systems for blood glucose control in diabetes. Deep learning models have provided leading results among machine learning algorithms to date in glucose prediction. However these models typically require large amounts of data to obtain best personalised glucose prediction results. Multitask learning facilitates an approach for leveraging data from multiple subjects while still learning accurate personalised models. In this work we present results comparing the effectiveness of multitask learning over sequential transfer learning, and learning only on subject-specific data with neural network and support vector regression. The multitask learning approach shows consistent leading performance in predictive metrics at both short-term and long-term prediction horizons. We obtain a predictive accuracy (RMSE) of 18.8 ±2.3, 25.3 ±2.9, 31.8 ±3.9, 41.2 ±4.5, 47.2 ±4.6 mg/dL at 30, 45, 60, 90, and 120 min prediction horizons respectively, with at least 93% clinically acceptable predictions using the Clarke Error Grid (EGA) at each prediction horizon. We also identify relevant prior information such as glycaemic variability that can be incorporated to improve predictive performance at long-term prediction horizons. Furthermore, we show consistent performance - ≤ 5% change in both RMSE and EGA (Zone A) - in rare cases of adverse glycaemic events with 1-6 weeks of training data. In conclusion, a multitask approach can allow for deploying personalised models even with significantly less subject-specific data without compromising performance.

Simultaneous Large Optical and Piezoelectric Effects Induced by Domain Reconfiguration Related to Ferroelectric Phase Transitions.

Electrical switching of ferroelectric domains and subsequent domain wall motion promotes strong piezoelectric activity, however, light scatters at refractive index discontinuities such as those found at domain wall boundaries. Thus, simultaneously achieving large piezoelectric effect and high optical transmissivity is generally deemed infeasible. Here, it is demonstrated that the ferroelectric domains in perovskite Pb(In1/2 Nb1/2 )O3 -Pb(Mg1/3 Nb2/3 )O3 -PbTiO3 domain-engineered crystals can be manipulated by electrical field and mechanical stress to reversibly and repeatably, with small hysteresis, transform the opaque polydomain structure into a highly transparent monodomain state. This control of optical properties can be achieved at very low electric fields (less than 1.5 kV cm-1 ) and is accompanied by a large (>10 000 pm V-1 ) piezoelectric coefficient that is superior to linear state-of-the-art materials by a factor of three or more. The coexistence of tunable optical transmissivity and high piezoelectricity paves the way for a new class of photonic devices.

A mask-based diagnostic platform for point-of-care screening of Covid-19.

Diagnostics of SARS-CoV-2 infection using real-time reverse-transcription polymerase chain reaction (RT-PCR) on nasopharyngeal swabs is now well-established, with saliva-based testing being lately more widely implemented for being more adapted for self-testing approaches. In this study, we introduce a different concept based on exhaled breath condensate (EBC), readily collected by a mask-based sampling device, and detection with an electrochemical biosensor with a modular architecture that enables fast and specific detection and quantification of COVID-19. The face mask forms an exhaled breath vapor containment volume to hold the exhaled breath vapor in proximity to the EBC collector to enable a condensate-forming surface, cooled by a thermal mass, to coalesce the exhaled breath into a 200-500 µL fluid sample in 2 min. EBC RT-PCR for SARS-CoV-2 genes (E, ORF1ab) on samples collected from 7 SARS-CoV-2 positive and 7 SARS-CoV-2 negative patients were performed. The presence of SARS-CoV-2 could be detected in 5 out of 7 SARS-CoV-2 positive patients. Furthermore, the EBC samples were screened on an electrochemical aptamer biosensor, which detects SARS-CoV-2 viral particles down to 10 pfu mL-1 in cultured SARS-CoV-2 suspensions. Using a "turn off" assay via ferrocenemethanol redox mediator, results about the infectivity state of the patient are obtained in 10 min.

Ultrahigh specific strength in a magnesium alloy strengthened by spinodal decomposition.

Strengthening of magnesium (Mg) is known to occur through dislocation accumulation, grain refinement, deformation twinning, and texture control or dislocation pinning by solute atoms or nano-sized precipitates. These modes generate yield strengths comparable to other engineering alloys such as certain grades of aluminum but below that of high-strength aluminum and titanium alloys and steels. Here, we report a spinodal strengthened ultralightweight Mg alloy with specific yield strengths surpassing almost every other engineering alloy. We provide compelling morphological, chemical, structural, and thermodynamic evidence for the spinodal decomposition and show that the lattice mismatch at the diffuse transition region between the spinodal zones and matrix is the dominating factor for enhancing yield strength in this class of alloy.

Maxillofacial Bone Fractures in Children and Adolescents: Overview of 247 Cases in a Major Referral Hospital, Najran, Kingdom of Saudi Arabia.

STUDY DESIGN: A retrospective study investigating maxillofacial bone fractures in the pediatric and adolescent population. OBJECTIVE: The aim of this study was to present our experience in the management of pediatric facial bone fractures. METHODS: This was a retrospective study of maxillofacial bone fractures in children and adolescents between the ages <1 year and 19 years in a Saudi Arabian subpopulation. Data collected include demographics, etiology, pattern, and treatment of maxillofacial bone fractures. Data were analyzed using IBM SPSS Statistics for Windows Version 25 (IBM Corp.). Results were presented as simple frequencies and descriptive statistics. RESULTS: Of the 1297 patients with maxillofacial bone fractures, 247 were cases involving children and adolescents giving a prevalence of 19.0% (247 patients, N = 1297). There were 233 males and 14 females with an M:F ratio of 16.6:1. The ages ranged from 9 months to 19 years with a mean ± SD of 14.4 ± 4.6. The age-group between 16 and 20 years had the highest frequency of patients (144 (58.4%)). In the 1- to 5-year group, falls accounted for most of the etiology (15 (6.1%)), while in the 16- to 20-year group, motor vehicular accident (MVA) was the main reason (120 (48.6%)). The majority of the fractures occurred in the mandible with 151(61.1%) cases. Open reduction and internal fixation (ORIF) were the main treatment modality in 171 (69.2%) patients. CONCLUSIONS: MVA was the main etiology of maxillofacial fractures in children and adolescents with male predominance, while the mandible had been the most frequently fractured bone. ORIF was the main treatment modality.

In situ X-ray diffraction investigation of electric-field-induced switching in a hybrid improper ferroelectric.

Improper ferroelectric mechanisms are increasingly under investigation for their potential to expand the current catalogue of functional materials whilst promoting couplings between ferroelectricity and other technologically desirable properties such as ferromagnetism. This work presents the results of an in situ synchrotron X-ray diffraction experiment performed on samples of Ca2.15Sr0.85Ti2O7 in an effort to elucidate the mechanism of hybrid improper ferroelectric switching in this compound. By simultaneously applying an electric field and recording diffraction patterns, shifts in the intensity of superstructure peaks consistent with one of the switching mechanisms proposed by Nowadnick & Fennie [Phys. Rev. B, (2016), 94, 104105] are observed. While the experiment only achieves a partial response, comparison with simulated data demonstrates a preference for a one-step switching mechanism involving an unwinding of the octahedral rotation mode in the initial stages of switching. These results represent some of the first reported experimental diffraction-based evidence for a switching mechanism in an improper ferroelectric.

Ultra-large electric field-induced strain in potassium sodium niobate crystals.

Electromechanical coupling in piezoelectric materials allows direct conversion of electrical energy into mechanical energy and vice versa. Here, we demonstrate lead-free (K x Na1-x )NbO3 single crystals with an ultrahigh large-signal piezoelectric coefficient d 33* of 9000 pm V-1, which is superior to the highest value reported in state-of-the-art lead-based single crystals (~2500 pm V-1). The enhanced electromechanical properties in our crystals are realized by an engineered compositional gradient in the as-grown crystal, allowing notable reversible non-180° domain wall motion. Moreover, our crystals exhibit temperature-insensitive strain performance within the temperature range of 25°C to 125°C. The enhanced temperature stability of the response also allows the materials to be used in a wider range of applications that exceed the temperature limits of current lead-based piezoelectric crystals.

Experience with Airway Management and Sequencing of Repair of Panfacial Fractures: A Single Tertiary Healthcare Appraisal in Najran, Kingdom of Saudi Arabia - A Retrospective Study.

INTRODUCTION: Special cooperation is required among surgeons and anesthetists in airway management during repair of panfacial fractures, due to problems of shared airway and occlusion. Several methods have been proposed for airway management and sequencing of repair of panfacial fractures. The main objective of the current study was to share our experience in the airway management and sequencing of repair of panfacial fractures. METHODS: This was a retrospective study of panfacial fractures in the Kingdom of Saudi Arabia from January 2008 to December 2018. Data collected included demographics, type of airway management, sequence of repair (as primary variables), and outcome of surgery (secondary variable), while surgeon and anesthetic expertise are confounders. Data were analyzed using IBM SPSS Statistics for Windows Version 25 (Armonk, NY, USA: IBM Corp). Results were presented as simple frequencies and descriptive statistics. Pearson Chi-square was used to compare categorical variables such as airway management and sequencing of repair with the panfacial fractures. Statistical significance was set at P ≤ 0.05. RESULTS: Overall, 1057 patients sustained different categories of maxillofacial bone fractures with 23 females and 1034 males (M:F of 46:1). A total of 43 male patients out of 1057 patients had panfacial fractures during the study period, giving a prevalence rate of 4.1%. Only the 43 male patients with panfacial fractures were analyzed. All cases were as a result of motor vehicular accident. Six (13.9%) patients had tracheostomy while 37 (86.1%) patients had submental intubation. "Bottom-up" and "outside-in" approach was used in 33 (76.7%) patients, while "top-bottom" and "inside-out" approach was used in 10 (23.3%) patients. DISCUSSION: Submental intubation was the major airway management of panfacial fracture, and "bottom-up" and "outside-in" approach was the main sequence of repair in our series. These approaches have been mentioned in the literature. CONCLUSION: From our study, victims of pan-facial fractures were found to be exclusively male with MVA as the sole etiological factor. Barring severe head injuries, which may necessitate the use of tracheostomy to sustain breathing over a longer period, submental intubation is extremely reliable as a mode of airway management during surgical treatment of panfacial fractures. The sequencing of repair of panfacial fractures can only be determined according to the case presentation rather than a predetermined one.

Convolutional Recurrent Neural Networks for Glucose Prediction.

Control of blood glucose is essential for diabetes management. Current digital therapeutic approaches for subjects with type 1 diabetes mellitus such as the artificial pancreas and insulin bolus calculators leverage machine learning techniques for predicting subcutaneous glucose for improved control. Deep learning has recently been applied in healthcare and medical research to achieve state-of-the-art results in a range of tasks including disease diagnosis, and patient state prediction among others. In this paper, we present a deep learning model that is capable of forecasting glucose levels with leading accuracy for simulated patient cases (root-mean-square error (RMSE) = 9.38  ± 0.71 [mg/dL] over a 30-min horizon, RMSE = 18.87  ± 2.25 [mg/dL] over a 60-min horizon) and real patient cases (RMSE = 21.07  ± 2.35 [mg/dL] for 30 min, RMSE = 33.27  ± 4.79% for 60 min). In addition, the model provides competitive performance in providing effective prediction horizon ([Formula: see text]) with minimal time lag both in a simulated patient dataset ([Formula: see text] = 29.0 ± 0.7 for 30 min and [Formula: see text] = 49.8  ± 2.9 for 60 min) and in a real patient dataset ([Formula: see text] = 19.3  ± 3.1 for 30 min and [Formula: see text] = 29.3  ± 9.4 for 60 min). This approach is evaluated on a dataset of ten simulated cases generated from the UVA/Padova simulator and a clinical dataset of ten real cases each containing glucose readings, insulin bolus, and meal (carbohydrate) data. Performance of the recurrent convolutional neural network is benchmarked against four algorithms. The proposed algorithm is implemented on an Android mobile phone, with an execution time of 6 ms on a phone compared to an execution time of 780 ms on a laptop.

Bioanalytical Assessment of Plasma Concentrations of Angiotensin-Converting Enzyme II Inhibitors and Angiotensin Receptor Blockers: A Pilot Study Among Patients Hospitalized With Acute Heart Failure.

BACKGROUND: Although angiotensin-converting enzyme II inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) improve chronic heart failure (HF) outcomes, their potential harms and benefits in acute HF (AHF) is less clear. STUDY QUESTION: We explored the relationship between ACEI or ARB plasma concentrations among patients with AHF with in-hospital change in estimated glomerular filtration rate (eGFR). DATA SOURCES AND STUDY DESIGN: From August 2016-June 2017, patients with AHF prescribed an outpatient ACEI or ARB were enrolled before AHF treatment. All patients were given twice their home dose of diuretic intravenously and received clinical care at the discretion of the medical team. Of 61 patients in the parent study, saved plasma from 34 who were prescribed an outpatient ACEI or ARB was included in this substudy. MEASURES AND OUTCOMES: Liquid chromatography-tandem mass spectrometry was performed to assess ACEI or ARB plasma concentrations before AHF treatment. Change in eGFR was computed using the Chronic Kidney Disease Epidemiology Collaboration equation, which adjusts for age, sex, and race; diuretic dose and enrollment eGFR were used to adjust for HF severity. Multiple linear regression adjusting for enrollment eGFR and diuretic dose was performed to examine the relationship between drug concentration (undetectable/low vs. in/above-range) and in-hospital change in eGFR. RESULTS: Of 34 patients with AHF, median age was 63 years (interquartile range, 58-78 years), 19 (55.9%) were women, median eGFR at enrollment was 55.6 mL/min (interquartile range, 35.2-75.3 mL/min), and for 11 (32.4%), no ACEI or ARB was detectable in plasma. Medication concentrations in- or above-reference range were associated with in-hospital decrease in eGFR of 8.3 mL/min (95% confidence interval, 15.3-1.3 mL/min decrease), after adjusting for enrollment eGFR and diuretic treatment. CONCLUSIONS: Bioanalytical assessment of medication levels may be useful to guide in-hospital ACEI and ARB therapy for patients with AHF.

The Bio-inspired Artificial Pancreas for Type 1 Diabetes Control in the Home: System Architecture and Preliminary Results.

BACKGROUND: Artificial pancreas (AP) technology has been proven to improve glucose and patient-centered outcomes for people with type 1 diabetes (T1D). Several approaches to implement the AP have been described, clinically evaluated, and in one case, commercialized. However, none of these approaches has shown a clear superiority with respect to others. In addition, several challenges still need to be solved before achieving a fully automated AP that fulfills the users' expectations. We have introduced the Bio-inspired Artificial Pancreas (BiAP), a hybrid adaptive closed-loop control system based on beta-cell physiology and implemented directly in hardware to provide an embedded low-power solution in a dedicated handheld device. In coordination with the closed-loop controller, the BiAP system incorporates a novel adaptive bolus calculator which aims at improving postprandial glycemic control. This paper focuses on the latest developments of the BiAP system for its utilization in the home environment. METHODS: The hardware and software architectures of the BiAP system designed to be used in the home environment are described. Then, the clinical trial design proposed to evaluate the BiAP system in an ambulatory setting is introduced. Finally, preliminary results corresponding to two participants enrolled in the trial are presented. RESULTS: Apart from minor technical issues, mainly due to wireless communications between devices, the BiAP system performed well (~88% of the time in closed-loop) during the clinical trials conducted so far. Preliminary results show that the BiAP system might achieve comparable glycemic outcomes to the existing AP systems (~73% time in target range 70-180 mg/dL). CONCLUSION: The BiAP system is a viable platform to conduct ambulatory clinical trials and a potential solution for people with T1D to control their glucose control in a home environment.

Revealing phase boundaries by weighted parametric structural refinement.

Parametric Rietveld refinement from powder diffraction data has been utilized in a variety of situations to understand structural phase transitions of materials in situ. However, when analysing data from lower-resolution two-dimensional detectors or from samples with overlapping Bragg peaks, such transitions become difficult to observe. In this study, a weighted parametric method is demonstrated whereby the scale factor is restrained via an inverse tan function, making the phase boundary composition a refinable parameter. This is demonstrated using compositionally graded samples within the lead-free piezoelectric (BiFeO3)x(Bi0.5K0.5TiO3)y(Bi0.5Na0.5TiO3)1-x-y and (Bi0.5Na0.5TiO3)x(BaTiO3)1-x systems. This has proven to be an effective method for diffraction experiments with relatively low resolution, weak peak splitting or compositionally complex multiphase samples.

VU0810464, a non-urea G protein-gated inwardly rectifying K+ (Kir 3/GIRK) channel activator, exhibits enhanced selectivity for neuronal Kir 3 channels and reduces stress-induced hyperthermia in mice.

BACKGROUND AND PURPOSE: G protein-gated inwardly rectifying K+ (Kir 3) channels moderate the activity of excitable cells and have been implicated in neurological disorders and cardiac arrhythmias. Most neuronal Kir 3 channels consist of Kir 3.1 and Kir 3.2 subtypes, while cardiac Kir 3 channels consist of Kir 3.1 and Kir 3.4 subtypes. Previously, we identified a family of urea-containing Kir 3 channel activators, but these molecules exhibit suboptimal pharmacokinetic properties and modest selectivity for Kir 3.1/3.2 relative to Kir 3.1/3.4 channels. Here, we characterize a non-urea activator, VU0810464, which displays nanomolar potency as a Kir 3.1/3.2 activator, improved selectivity for neuronal Kir 3 channels, and improved brain penetration. EXPERIMENTAL APPROACH: We used whole-cell electrophysiology to measure the efficacy and potency of VU0810464 in neurons and the selectivity of VU0810464 for neuronal and cardiac Kir 3 channel subtypes. We tested VU0810464 in vivo in stress-induced hyperthermia and elevated plus maze paradigms. Parallel studies with ML297, the prototypical activator of Kir 3.1-containing Kir 3 channels, were performed to permit direct comparisons. KEY RESULTS: VU0810464 and ML297 exhibited comparable efficacy and potency as neuronal Kir 3 channel activators, but VU0810464 was more selective for neuronal Kir 3 channels. VU0810464, like ML297, reduced stress-induced hyperthermia in a Kir 3-dependent manner in mice. ML297, but not VU0810464, decreased anxiety-related behaviour as assessed with the elevated plus maze test. CONCLUSION AND IMPLICATIONS: VU0810464 represents a new class of Kir 3 channel activator with enhanced selectivity for Kir 3.1/3.2 channels. VU0810464 may be useful for examining Kir 3.1/3.2 channel contributions to complex behaviours and for probing the potential of Kir 3 channel-dependent manipulations to treat neurological disorders.

Frequency-dependent decoupling of domain-wall motion and lattice strain in bismuth ferrite.

Dynamics of domain walls are among the main features that control strain mechanisms in ferroic materials. Here, we demonstrate that the domain-wall-controlled piezoelectric behaviour in multiferroic BiFeO3 is distinct from that reported in classical ferroelectrics. In situ X-ray diffraction was used to separate the electric-field-induced lattice strain and strain due to displacements of non-180° domain walls in polycrystalline BiFeO3 over a wide frequency range. These piezoelectric strain mechanisms have opposing trends as a function of frequency. The lattice strain increases with increasing frequency, showing negative piezoelectric phase angle (i.e., strain leads the electric field), an unusual feature so far demonstrated only in the total macroscopic piezoelectric response. Domain-wall motion exhibits the opposite behaviour, it decreases in magnitude with increasing frequency, showing more common positive piezoelectric phase angle (i.e., strain lags behind the electric field). Charge redistribution at conducting domain walls, oriented differently in different grain families, is demonstrated to be the cause.