Lead-free dual-frequency ultrasound implants for wireless, biphasic deep brain stimulation.

Ultrasound-driven bioelectronics could offer a wireless scheme with sustainable power supply; however, current ultrasound implantable systems present critical challenges in biocompatibility and harvesting performance related to lead/lead-free piezoelectric materials and devices. Here, we report a lead-free dual-frequency ultrasound implants for wireless, biphasic deep brain stimulation, which integrates two developed lead-free sandwich porous 1-3-type piezoelectric composite elements with enhanced harvesting performance in a flexible printed circuit board. The implant is ultrasonically powered through a portable external dual-frequency transducer and generates programmable biphasic stimulus pulses in clinically relevant frequencies. Furthermore, we demonstrate ultrasound-driven implants for long-term biosafety therapy in deep brain stimulation through an epileptic rodent model. With biocompatibility and improved electrical performance, the lead-free materials and devices presented here could provide a promising platform for developing implantable ultrasonic electronics in the future.

Flexible, biodegradable ultrasonic wireless electrotherapy device based on highly self-aligned piezoelectric biofilms.

Biodegradable piezoelectric devices hold great promise in on-demand transient bioelectronics. Existing piezoelectric biomaterials, however, remain obstacles to the development of such devices due to difficulties in large-scale crystal orientation alignment and weak piezoelectricity. Here, we present a strategy for the synthesis of optimally orientated, self-aligned piezoelectric γ-glycine/polyvinyl alcohol (γ-glycine/PVA) films via an ultrasound-assisted process, guided by density functional theory. The first-principles calculations reveal that the negative piezoelectric effect of γ-glycine originates from the stretching and compression of glycine molecules induced by hydrogen bonding interactions. The synthetic γ-glycine/PVA films exhibit a piezoelectricity of 10.4 picocoulombs per newton and an ultrahigh piezoelectric voltage coefficient of 324 × 10-3 volt meters per newton. The biofilms are further developed into flexible, bioresorbable, wireless piezo-ultrasound electrotherapy devices, which are demonstrated to shorten wound healing by ~40% and self-degrade in preclinical wound models. These encouraging results offer reliable approaches for engineering piezoelectric biofilms and developing transient bioelectronics.

Unveiling the Pivotal Role of dx2-y2 Electronic States in Nickel-Based Hydroxide Electrocatalysts for Methanol Oxidation.

The anodic methanol oxidation reaction (MOR) plays a crucial role in coupling with the cathodic hydrogen evolution reaction (HER) and enables the sustainable production of the high-valued formate. Nickel-based hydroxide (Ni(OH)2) as MOR electrocatalyst has attracted enormous attention. However, the key factor determining the intrinsic catalytic activity remains unknown, which significantly hinders the further development of Ni(OH)2 electrocatalyst. Here, we found that the d x 2 - y 2 ${{d}_{{x}^{2}-{y}^{2}}}$ electronic state within antibonding bands plays a decisive role in the whole MOR process. The onset potential depends on the deprotonation ability (Ni2+ to Ni3+), which was closely related to the band center of d x 2 - y 2 ${{d}_{{x}^{2}-{y}^{2}}}$ orbital. The closer of d x 2 - y 2 ${{d}_{{x}^{2}-{y}^{2}}}$ orbital to the Fermi level showed the stronger the deprotonation ability. Meanwhile, in the high potential region, the broadening of d x 2 - y 2 ${{d}_{{x}^{2}-{y}^{2}}}$ orbital would facilitate the electron transfer from methanol to catalysts (Ni3+ to Ni2+), further enhancing the catalytic properties. Our work for the first time clarifies the intrinsic relationship between d x 2 - y 2 ${{d}_{{x}^{2}-{y}^{2}}}$ electronic state and the MOR activities, which adds a new layer of understanding to the methanol electrooxidation research scene.

Realization of the Giant Pyroelectric Response via Modulated Polar Structures.

Among pyroelectric materials, Bi0.5 Na0.5 TiO3 (BNT)-based relaxors are particularly noteworthy due to their significant polarization fluctuation near the depolarization temperature (Td ), resulting in a large pyroelectric response. What has been overlooked is the dynamic behavior of inherent polar structures, particularly the temperature-dependent evolution of polar nanoregions (PNRs), which significantly impacts the pyroelectric behavior. Herein, based on the large pyroelectric response origination (the ferroelectric-relaxor phase transition), the mixed nonergodic and ergodic relaxor (NR+ER) critical state is constructed, which is believed to trigger the easily fluctuating polarization state with excellent pyroelectric response. Composition engineering (with Li+ , Sr2+ , and Ta5+ ) strategically controls the relaxor process and modulates the dynamic behavior of inherent polar structures by the random field effect. The pyroelectric coefficient of more than 1441 µCm-2 K-1 at room temperature (RT), more than 9221 µCm-2 K-1 (RT), and ≈107911 µCm-2 K-1 (Td ) are achieved in the Li+ -doped sample, the Sr2+ -doped sample, and the (Li+ +Ta5+ ) co-doped sample, respectively. This work earns the highest RT pyroelectric coefficient in BNT-based relaxors, which is suitable for pyroelectric applications. Furthermore, it provides a strategy for modulating the pyroelectric performance of BNT-based relaxors.

Reversible Multimode Luminescence Modulations in Photochromic-Translucent Yb3+/Eu3+ Codoped K0.5Na0.5NbO3 Ceramics.

Luminescent tunable materials have promising application potential in optical switches, optical information storage, and so on. Although europium (Eu) is a good downconversion red luminescent rare earth element, there are few studies on the upconversion luminescence and photochromism of Eu-doped potassium sodium niobate (KNN) ferroelectrics. In this paper, Eu3+ and Yb3+ codoped KNN translucent ferroelectric ceramics were synthesized and the effect of Yb3+ content on the luminescence and photochromism is studied. Both the up- and downconversion luminescence intensity and decay rate before and after photochromism can be well controlled by Yb3+ content. That is, an upconversion luminescent translucent ceramic that can be completely discolored by 405 nm light illumination for 10 s was obtained. The luminescence modulations are closely related to the evolution of oxygen vacancy and crystal field around the luminescence center, which can be verified by the illumination-induced electron paramagnetic resonance (EPR) signal and local piezoresponse switching behavior variation as well as the discovery of energy level splitting and spectral line shift. We believe that this work shows a paradigm for designing high-performance reversible multimode luminescence modulation ferroelectric ceramics.

Understanding the Origin of Reconstruction in Transition Metal Oxide Oxygen Evolution Reaction Electrocatalysts.

Electrochemical water splitting to generate hydrogen energy fills a gap in the intermittency issues for wind and sunlight power. Transition metal (TM) oxides have attracted significant interest in water oxidation due to their availability and excellent activity. Typically, the transitional metal oxyhydroxides species derived from these metal oxides are often acknowledged as the real catalytic species, due to the irreversible structural reconstruction. Hence, in order to innovatively design new catalyst, it is necessary to provide a comprehensive understanding for the origin of surface reconstruction. In this review, the most recent developments in the reconstruction of transition metal-based oxygen evolution reaction electrocatalysts were introduced, and various chemical driving forces behind the reconstruction mechanism were discussed. At the same time, specific strategies for modulating pre-catalysts to achieve controllable reconfiguration, such as metal substituting, increase of structural defect sites, were summarized. At last, the issues for the further understanding and optimization of transition metal oxides compositions based on structural reconstruction were provided.

Establishing a Relationship between the Piezoelectric Response and Oxygen Vacancies in Lead-Free Piezoelectrics.

BiFeO3-BaTiO3 (BF-BT)-based lead-free piezoceramics are desired materials for high-temperature applications of piezoelectric sensors with a high Curie temperature and good piezoelectric properties. Recent studies have shown that oxygen vacancies have a significant effect on electrostrain and piezoelectric properties. Interestingly, two different phenomena exist, i.e., the increase in piezoelectric properties is often associated with a decrease in the concentration of oxygen vacancies, while the increase in electrostrain is often associated with an increase in the concentration of oxygen vacancies. Especially, for BF-based ceramics, the physical mechanisms related to property differences caused by oxygen vacancies are rarely reported, which needs further exploration. Here, two ceramics with differences in their oxygen vacancy concentrations are designed. Based on Rayleigh analysis, thermal/electric field-induced domain response (ferroelectric scaling), and macro-microstructural characterization, we can conclude that the transient piezoelectric response and the aging process are significantly affected by the oxygen vacancy concentration. In other words, the increasing concentration of oxygen vacancies in BF-BT ceramics enhances the reversible piezoelectric response contributed by lattice distortion and strengthens the response of domain switching and domain wall motion to electric and thermal fields but deteriorates their aging behavior, which leads to the degradation of piezoelectric performance. Besides, polarization saturation and defect pegging significantly improve the temperature stability of the strain.

Mechanochemical Synthesis of Aryl Fluorides by Using Ball Milling and a Piezoelectric Material as the Redox Catalyst.

Aryl fluorides are important structural motifs in many pharmaceuticals. Although the Balz-Schiemann reaction provides an entry to aryl fluorides from aryldiazonium tetrafluoroborates, it suffers from drawbacks such as long reaction time, high temperature, toxic solvent, toxic gas release, and low functional group tolerance. Here, we describe a general method for the synthesis of aryl fluorides from aryldiazonium tetrafluoroborates using a piezoelectric material as redox catalyst under ball milling conditions in the presence of Selectfluor. This approach effectively addresses the aforementioned limitations. Furthermore, the piezoelectric material can be recycled multiple times. Mechanistic investigations indicate that this fluorination reaction may proceed via a radical pathway, and Selectfluor plays a dual role as both a source of fluorine and a terminal reductant.

Accelerated Surface Reconstruction through Regulating the Solid-Liquid Interface by Oxyanions in Perovskite Electrocatalysts for Enhanced Oxygen Evolution.

A comprehensive understanding of surface reconstruction was critical to developing high performance lattice oxygen oxidation mechanism (LOM) based perovskite electrocatalysts. Traditionally, the primary determining factor of the surface reconstruction process was believed to be the oxygen vacancy formation energy. Hence, most previous studies focused on optimizing composition to reduce the oxygen vacancy formation energy, which in turn facilitated the surface reconstruction process. Here, for the first time, we found that adding oxyanions (SO4 2- , CO3 2- , NO3 - ) into the electrolyte could effectively regulate the solid-liquid interface, significantly accelerating the surface reconstruction process and enhancing oxygen evolution reaction (OER) activities. Further studies indicated that the added oxyanions would adsorb onto the solid-liquid interface layer, disrupting the dynamic equilibrium between the adsorbed OH- ions and the OH- ions generated during surface reconstruction process. As such, the OH- ions generated during surface reconstruction process could be more readily released into the electrolyte, thereby leading to an acceleration of the surface reconstruction. Thus, it was expected that our finding would provide a new layer of understanding to the surface reconstruction process in LOM-based perovskite electrocatalysts.

The hypertension and hyperlipidemia status among type 2 diabetic patients in the community and influencing factors analysis of glycemic control.

OBJECTIVE: To understand the prevalence of hypertension and hyperlipidaemia as well as the current status of glycaemic control and its influencing factors among type 2 diabetes mellitus patients in the community in South China, and to provide recommendations for the prevention and control of diabetes. METHODS: Questionnaires, physical examinations and laboratory tests were conducted on patients with type 2 diabetes mellitus who participated in the National Basic Public Health Service Programme in Guangzhou in 2020. The chi-square test, t-test and multi-factor unconditional logistic regression analysis were performed using R 4.1.2 software. RESULT: Among 127,423 type 2 diabetic patients in Guangzhou, 57,695 achieved glycemic control standards, with a glycemic control rate of 45.28%.In this study, the proportion of T2DM patients with hypertension and hyperlipidaemia together was 27.79%, The percentage of T2DM patients with hypertension alone and hyperlipidaemia alone was 28.34% and 20.53% respectively, and the rate of no complications was 23.34%. There was a statistically significant difference in the rate of glycaemic control between the different disease combination states (P < 0.05). The glycaemic control rate was 47.67% in diabetic patients without hypertension and hyperlipidaemia, 52.54% and 37.24% in those with combined hypertension alone and hyperlipidaemia alone respectively, compared to 41.80% in diabetic patients with hypertension and hyperlipidaemia. After adjusting for all covariates, multivariate analysis showed that combined hypertension alone was associated with good glycaemic control (OR 0.817, 95% CI 0.791, 0.843, P < 0.001),when using comorbid T2DM as a control group, combined hyperlipidaemia alone, combined hypertension and hyperlipidaemia were associated with poor glycaemic control (OR 1.521, 95% CI 1.470,1.574, P < 0.001 and OR 1.250, 95% CI 1.211,1.291, P < 0.001), Subgroup analyses as well as multifactorial unconditional logistic regression analyses showed that patients with type 2 diabetes who were overweight and obese, smoked, drank alcohol, had a diagnosis of diabetes for ≥ 6 years, had fair or poor adherence and had a family history of diabetes had lower rates of glycaemic control. CONCLUSION: The results of this study showed that the co-morbidity of hypertension and hyperlipidaemia was high and prevalent among diabetic patients in Guangzhou. Moreover, glycaemic control of T2DM patients with hyperlipidaemia was lower than other diabetic patients. Obesity and overweight, poor lifestyle and dietary habits are also major factors affecting the treatment and control of T2D patients in this region. Therefore, comprehensive measures should be actively taken to control blood glucose levels in type 2 diabetic patients by also incorporating lipid management into the community and strictly controlling lipid levels.

Origin of Surface Reconstruction in Lattice Oxygen Oxidation Mechanism Based-Transition Metal Oxides: A Spontaneous Chemical Process.

A fundamental understanding of surface reconstruction process is pivotal to developing highly efficient lattice oxygen oxidation mechanism (LOM) based electrocatalysts. Traditionally, the surface reconstruction in LOM based metal oxides is believed as an irreversible oxygen redox behavior, due to the much slower rate of OH- refilling than that of oxygen vacancy formation. Here, we found that the surface reconstruction in LOM based metal oxides is a spontaneous chemical reaction process, instead of an electrochemical reaction process. During the chemical process, the lattice oxygen atoms were attacked by adsorbed water molecules, leading to the formation of hydroxide ions (OH- ). Subsequently, the metal-site soluble atoms leached from the oxygen-deficient surface. This work also suggests that the enhancement of surface hydrophilicity could accelerate the surface reconstruction process. Hence, such a finding could add a new layer for the understanding of surface reconstruction mechanism.

Defect-Modified nano-BaTiO3 as a Sonosensitizer for Rapid and High-Efficiency Sonodynamic Sterilization.

Multidrug-resistant bacteria caused by the unlimited overuse of antibiotics pose a great challenge to global health. An antibacterial method based on reactive oxygen species (ROS) is one of the effective strategies without inducing bacterial resistance. Owing to the ability of generating ROS, piezocatalytic material-mediated sonodynamic therapy (SDT) has drawn much attention. However, its major challenge is the low ROS generation efficiency in the piezocatalytic process due to the poor charge carrier concentration of piezoelectric materials. Vacancy engineering can regulate the charge density and largely promote ROS generation under ultrasound (US) irradiation. Herein, a US-responsive self-doped barium titanate with controlled oxygen vacancy (Vo) concentrations was successfully synthesized through a facile thermal reduction treatment at different temperatures (i.e., 350, 400, and 450 °C), and the corresponding samples were named as BTO-350, BTO-400, and BTO-450, respectively. Then, the effect of Vo concentrations on ROS generation efficiency during the piezocatalytic process was systematically studied. And BTO-400 was found to possess the highest piezocatalytic activity and excellent sonodynamic antibacterial performance against Escherichia coli and Staphylococcus aureus. Furthermore, its antibacterial mechanism was confirmed that the ROS generated under US could damage bacterial cell membrane and cause considerable leakage of cytoplasmic components and irreversible death of bacteria. Notably, the in vivo results illustrated that the BTO-400 could serve as an effective antibacterial agent and accelerate skin healing via SDT therapy. In all, the Vo defect-modified nano-BaTiO3 has a noticeable potential to induce a rapid and efficient sterilization as well as skin tissue repair by SDT.

Optimizing electro-strain via manipulating the oxygen octahedral structure in BF-BT-based ceramics.

Much attention has been paid to the electrical performance caused by doping, while the property regulation mechanism of intrinsic contributions such as symmetry and tilt of the oxygen octahedron is still deficiently understood in bismuth ferrite-barium titanate (BF-BT) ceramics. To establish the correlation between the evolution of the intrinsic structure and electro-strain, three doping systems of BF-BT-xLiNbO3/xNaNbO3/xKNbO3 are designed, in which Li+, Na+, and K+ have similar chemical properties but different ionic radii. Macro-property characterization suggests that the largest electro-strain (S ∼ 0.25%) could be achieved in the BF-BT-xNaNbO3 system when x = 0.02. Microscopic crystal structure analysis manifests that Na+ can enhance the symmetry of O-O and Fe-O bond lengths and maintain a certain degree of oxygen octahedron tilt, while smaller (Li+) and larger (K+) ionic radii can induce the asymmetry of O-O and/or Fe-O bond lengths. The real-space domain images indicate that the domain configuration of ceramics with improved strain exhibit similar miniaturized maze-like structures. Therefore, the synergic contributions, including symmetry of the bond length and appropriate oxygen octahedron tilt as well as miniaturized maze-like domain structure, were the origin of the improved electro-strain in BF-BT-0.02NaNbO3. We believe that understanding the effect of the intrinsic crystal structure on the electro-strain is meaningful for tailoring BF-BT electrical properties.

Achieving High Piezoelectricity and Excellent Temperature Stability in Pb(Zr,Ti)O3-Based Ceramics via Low-Temperature Sintering.

Developing piezoelectric ceramics with high piezoelectric properties and broad temperature usage ranges via low-temperature sintering is one of decisive importance for flourishing developments for emerging electromechanical applications. However, these properties are usually mutually exclusive, such as low-temperature sintering and high piezoelectricity as well as high piezoelectricity and temperature stability. Here, we report high piezoelectricity (i.e., piezoelectric constant d33 ≈ 744 pC/N, electromechanical coupling factor kp ≈ 75%, and Curie temperature TC ≈ 201 °C) and superior temperature stability (d33 varies less than 10% within 25-160 °C) in Pb0.905Ba0.095(Zr0.54Ti0.46)O3 + 1 mol % Nb2O5 + 1 wt % Bi2O3 + x wt % CdCO3 (PBZTNB-xCd) ceramics that are fabricated at a sintering temperature of as low as 960 °C, superior to those of other reported random and textured ceramics. Good piezoelectricity is attributed to the remaining rhombohedral-tetragonal (R-T) phase coexistence and the high ceramic density. Excellent temperature stability is related to the stable crystal structure and domain structure. These properties confer to the produced materials attractive characteristics for further consideration in several advanced applications, especially for piezoelectric transducer applications requiring constant structures over a broad temperature range.

Deciphering the atomic-scale structural origin for large dynamic electromechanical response in lead-free Bi0.5Na0.5TiO3-based relaxor ferroelectrics.

Despite the extraordinary electromechanical properties of relaxor ferroelectrics, correlating their properties to underlying atomic-scale structures remains a decisive challenge for these "mess" systems. Here, taking the lead-free relaxor ferroelectric Bi0.5Na0.5TiO3-based system as an example, we decipher the atomic-scale structure and its relationship to the polar structure evolution and large dynamic electromechanical response, using the direct atomic-scale point-by-point correlation analysis. With judicious chemical modification, we demonstrate the increased defect concentration is the main driving force for deviating polarizations with high-angle walls, leading to the increased random field. Meanwhile, the main driving force for deviating polarizations with low-angle walls changes from the anti-phase oxygen octahedral tilting to the multidirectional A-O displacement, leading to the decreased anisotropy field. Benefiting from the competitive and synergetic equilibrium of anisotropic field versus random field, the facilitated polarization rotation and extension versus facilitated domain switching are identified to be responsible for the giant electromechanical response. These observations lay a foundation for understanding the "composition-structure-property" relationships in relaxor ferroelectric systems, guiding the design of functional materials for electromechanical applications.

A Novel Strategy for Excellent Piezocatalytic Activity in Lead-Free BaTiO3-Based Materials via Manipulating the Multiphase Coexistence.

Piezocatalysis is regarded as a fascinating technology for water remediation and possible disease treatment. A high piezoelectric coefficient (d33) is one of the most important parameters to determine piezocatalytic performance, which can be manipulated via phase boundary design. Herein, a novel strategy for excellent piezocatalytic activity in lead-free BaTiO3-based materials via manipulating the multiphase coexistence is proposed. The piezocatalyst of 0.82Ba(Ti0.89Sn0.11)O3-0.18(Ba0.7Ca0.3)TiO3 (0.82BTS-0.18BCT) with multiphase coexistence is prepared, and a large d33 can be obtained. As a result, 0.82BTS-0.18BCT exhibits excellent piezocatalytic performance for the degradation of Rhodamine B (RhB). Furthermore, the removal rate of RhB could reach more than 90% after vibration for 30 min, and the reaction rate constant (k) could reach 0.0706 min-1, which is much superior to that of most other representative perovskite-structured piezoelectric materials. Excellent piezocatalytic performance can be attributed to the strong local ferro-/piezoelectric response induced by the multiphase coexistence, as confirmed by the in situ piezoresponse force microscopy (PFM). Finally, the piezocatalytic degradation mechanism is analyzed systemically and proposed. This work not only provides a high-efficiency piezocatalyst but also sheds light on developing efficient BT-based piezocatalysts by manipulating the multiphase coexistence.

Robust Piezoelectricity with Spontaneous Polarization in Monolayer Tellurene and Multilayer Tellurium Film at Room Temperature for Reliable Memory.

Robust neuromorphic computing in the Big Data era calls for long-term stable crossbar-array memory cells; however, the elemental segregation in the switch unit and memory unit that inevitably occurs upon cycling breaks the compositional and structural stability, making the whole memory cell a failure. Searching for a novel material without segregation that can be used for both switch and memory units is the major concern to fabricate robust and reliable nonvolatile cross-array memory cells. Tellurium (Te) is found recently to be the only peculiar material without segregation for switching, but the memory function has not been demonstrated yet. Herein, apparent piezoelectricity is experimentally confirmed with spontaneous polarization behaviors in elementary 2D Te, even in monolayer tellurene (0.4 nm), due to the highly oriented polarization of the molecular structure and the non-centrosymmetric lattice structure. A large memory window of 7000, a low working voltage of 2 V, and high on switching current up to 36.6 µA µm-1 are achieved in the as-fabricated Te-based memory device, revealing the great promise of Te for both switching and memory units in one cell without segregation. The piezoelectric Te with spontaneous polarization provides a platform to build robust, reliable, and high-density logic-in-memory chips in neuromorphic computing.

Flexible lead-free piezoelectric arrays for high-efficiency wireless ultrasonic energy transfer and communication.

Implantable medical electronics (IMEs) are now becoming increasingly prevalent for diagnostic and therapeutic purposes. Despite extensive efforts, a primary challenge for IMEs is reliable wireless power and communication to provide well-controlled, therapeutically relevant effects. Ultrasonic energy transfer and communication (UETC) employing traveling ultrasound waves to transmit energy has emerged as a promising wireless strategy for IMEs. Nevertheless, conventional UETC systems are rigid, bulky, and based on toxic lead-based piezoelectric materials, raising efficiency and safety concerns. Here, we present a novel transcutaneous UETC system based on a two-dimensional flexible lead-free piezoelectric array (f-LFPA) that hybridizes high-performance (piezoelectric coefficient d33 ≈ 503 pC N-1) (K,Na)NbO3-based eco-friendly piezo-units with soft structural components. The newly developed lead-free piezo-unit exhibits submicron ferroelectric domains and superior energy harvesting figures of merit (d33g33 ≈ 20 000 × 10-15 m2 N-1), resulting in the prepared f-LFPA demonstrating a high output voltage of 22.4 V, a power density of 0.145 W cm-2, and a signal-to-noise ratio of more than 30 dB within the FDA safety limits, while maintaining the flexibility for wide-angle receiving. Further ex vivo experiment demonstrates the adequate power supply capabilities of the f-LFPA and its possible application in future implantable eco-friendly bioelectronics for diagnostics, therapy, and real-time monitoring.