Principle and experimental study of a combined teardrop and heart-shaped channel bluffbody valveless piezoelectric pump.

In this study, we have developed a piezoelectric pump with a combined teardrop- and heart-shaped channel based on the Coanda effect and bionics principle. The bluffbody consists of teardrop- and heart-shaped channels. The vibration and the pump flow rate are evaluated theoretically, and the flow conditions under different bluffbody heights and different main channel widths are simulated. The theoretical and simulation results show that the pump has uneven resistance to flow in forward and reverse directions, and the height of the teardrop bluffbody and the width main channel affect the flow in the channel. Test data show that under the same pressure, when the main channel is 5 mm and the bluffbody height is 8 mm, the pump flow rate is 460.8 ml/min. The pump alleviates the serious backflow problem through the fluid blocking structure and is expected to become an active driver of microfluidic devices.

Recent developments in wearable piezoelectric energy harvesters.

Wearable piezoelectric energy harvesters (WPEHs) have gained popularity and made significant development in recent decades. The harvester is logically built by the movement patterns of various portions of the human body to harvest the movement energy and immediately convert it into usable electrical energy. To directly power different microelectronic devices on the human body, a self-powered device that does not require an additional power supply is being created. This Review provides an in-depth review of WPEHs, explaining the fundamental concepts of piezoelectric technology and the materials employed in numerous widely used piezoelectric components. The harvesters are classed according to the movement characteristics of several portions of a person's body, such as pulses, joints, skin, and shoes (feet). Each technique is introduced, followed by extensive analysis. Some harvesters are compared, and the benefits and drawbacks of each technique are discussed. Finally, this Review presents future goals and objectives for WPEH improvement, and it will aid researchers in understanding WPEH to the point of more efficient wireless energy delivery to wearable electronic components.

Increasing the angle between caudal screw and the transverse plane may aggravate the risk of femoral head necrosis by deteriorating the fixation stability in patients with femoral neck fracture.

Necrosis of the femoral head is the main complication in femoral neck fracture patients with triangle cannulated screw fixation. Instant postoperative fixation instability is a main reason for the higher risk of femoral head necrosis. Biomechanical studies have shown that cross screw fixation can effectively optimize fixation stability in patients with proximal humerus fractures and pedicle screw fixation, but whether this method can also effectively optimize the fixation stability of femoral neck fractures and reduce the corresponding risk of femoral head necrosis has yet to be identified. In this study, a retrospective review of imaging data in femoral neck fracture patients was performed. The cross angle between the femoral neck and the caudal cannulated screw was reported; if the angle between the screw and the transverse plane increased, it was recorded as positive; otherwise, it was recorded as negative. Angle values and their corresponding absolute values were compared in patients with and without femoral head necrosis. Regression analysis identified potential risk factors for femoral head necrosis. Moreover, the biomechanical effect of the screw-femoral neck angle on fixation stability was also verified by numerical mechanical simulations. Clinical review presented significantly larger positive angle values in patients with femoral head necrosis, which was also proven to be an independent risk factor for this complication. Moreover, fixation stability progressively deteriorated with increasing angle between the caudal screw and the transverse plane. Therefore, increasing the angle between the caudal screw and the transverse plane may aggravate the risk of femoral head necrosis by deteriorating the fixation stability in patients with femoral neck fracture.

Bioinformatics analysis and experimental validation of key genes associated with lumbar disc degeneration and biomechanics.

Background: Lumbar disc degeneration (LDD) is an important pathological basis for the development of degenerative diseases of the lumbar spine. Most clinical patients have low back pain as their main symptom. The deterioration of the biomechanical environment is an important cause of LDD. Although there is a large amount of basic research on LDD, there are fewer reports that correlate biomechanical mechanisms with basic research. Our research aims to identify 304 key genes involved in LDD due to biomechanical deterioration, using a bioinformatics approach. We focus on SMAD3, CAV1, SMAD7, TGFB1 as hub genes, and screen for 30 potential target drugs, offering novel insights into LDD pathology and treatment options. Methods: The Gene Cards, GenCLip3, OMIM and Drugbank databases were explored to obtain genes associated with biomechanics and LDD, followed by making veen plots to obtain both co-expressed genes. GO enrichment analysis and KEGG pathway analysis of the co-expressed genes were obtained using the DAVID online platform and visualised via a free online website. Protein interaction networks (PPI) were obtained through the STRING platform and visualised through Cytoscape 3.9.0. These genes were predicted for downstream interaction networks using the STITCH platform. Then, the GSE56081 dataset was used to validate the key genes. RT-PCR was used to detect mRNA expression of core genes in the degenerated nucleus pulposus (NP) samples and western bolt was used for protein expression. Lastly, the obtained hub genes were searched in the drug database (DGIdb) to find relevant drug candidates. Results: From the perspective of biomechanics-induced LDD, we obtained a total of 304 genes, the GO functional enrichment and KEGG pathway enrichment analysis showed that the functions of these genes are mostly related to inflammation and apoptosis. The PPI network was constructed and four Hub genes were obtained through the plug-in of Cytoscape software, namely SMAD3, CAV1, SMAD7 and TGFB1. The analysis of key genes revealed that biomechanical involvement in LDD may be related to the TGF-ß signaling pathway. Validation of the GSE56081 dataset revealed that SMAD3 and TGFB1 were highly expressed in degenerating NP samples. RT-PCR results showed that the mRNA expression of SMAD3 and TGFB1 was significantly increased in the severe degeneration group; Western blot results also showed that the protein expression of TGFB1 and P-SMAD3 was significantly increased. In addition, we identified 30 potential drugs. Conclusion: This study presented a new approach to investigate the correlation between biomechanical mechanisms and LDD. The deterioration of the biomechanical environment may cause LDD through the TGF-ß signaling pathway. TGFB1 and SMAD3 are important core targets. The important genes, pathways and drugs obtained in this study provided a new basis and direction for the study, diagnosis and treatment of LDD.

Energy harvesting from water impact using piezoelectric energy harvester.

Energy, as an indispensable part of human life, has been a hot topic of research among scholars. The water kinetic energy generated by ocean currents, as a kind of clean energy, has high utilization rate, high power generation potential, and a broad prospect of powering microelectronic devices. As a result, the water kinetic piezoelectric energy harvester (WKPEH) has made significant progress in powering ocean sensors by harvesting ocean currents. This paper provides a comprehensive review of technologies that have been used in recent years to harvest energy from marine fluids using WKPEH. Detailed study of the energy harvesting mechanism of WKPEH. WKPEH can use the flutter-induced vibrations, vortex-induced vibrations, and wake oscillation principles to harvest water kinetic energy. The structural characteristics and output performance of each mechanism are also discussed and compared, and finally, a prospect on WKPEH is given.

Research on the performance of a valveless piezoelectric pump with a herringbone bluffbody.

Aiming to improve the output performance of a valveless piezoelectric pump, this article presents a valveless piezoelectric pump with a herringbone bluffbody. The bluffbody is herringbone shaped and distributed in a tapered chamber. The tapered chamber and the bluffbody create a large reverse resistance in the chamber, thus effectively mitigating the backflow problem of the valveless pump. The theoretical analysis determined the relationship between the flow rate and the flow resistance coefficient as well as the variation of the pump chamber volume. It was also concluded that the piezoelectric pump has the best output flow at intrinsic frequencies. Through simulation calculations, the effectiveness of the bluffbody structure in mitigating backflow in piezoelectric pumps is analyzed to provide a reference for experimental prototype design parameters. Finally, a range of prototypes is produced for experimentation. The experimental results show that the designed bluffbody shape can increase the return energy loss to effectively mitigate the return flow issues of the valveless piezoelectric pump, thus improving the output performance. The optimum output flow rate is 158.5 ml/min at 200 V and 52.5 Hz and the tapered chamber angle of 6°, and the bluffbody height, angle, and quantities are 2 mm, 40°, and 2, respectively. The construction of the valveless piezoelectric pump proposed in this research can be used as a reference for subsequent improvements in the performance of valveless piezoelectric pumps, and due to the high output performance, experimental studies can be carried out in applications such as dispensing and heat dissipation in electronic products.

Design and study of an eccentric wheel drive-based rotating piezoelectric energy harvester.

A nonlinear rotating piezoelectric energy harvester (N-RPEH) driven by eccentric wheels is proposed to collect rotational energy in the environment. Driven by external rotational motion, an eccentric wheel converts rotational motion into linear motion and realizes electrical energy output through magnetic coupling. To increase the effectiveness of the equipment's energy conversion process, this article aims to transform the rotational motion of an eccentric wheel into a linear motion of a motion board. The effects of the motion board's length L, the cylindrical magnet's height H, and the mass block M at the piezoelectric patch's end on the output performance of N-RPEH are explained by theoretical modeling and simulation. Through theoretical analysis, simulation, and experiment, it is found that when L = 120 mm, H = 6 mm, and M = 5.0 g (medium mass), the output voltage reaches the maximum of 14.16 V. Under this parameter, N-RPEH can produce a maximum power of 7.0688 mW when the external resistance value is 2 kΩ. Application experiments show that N-RPEH can light up 60 light-emitting diodes. Therefore, the proposed N-RPEH can effectively collect rotational energy and has a wide range of potential applications in wireless sensor networks.

Performance analysis of a novel flat lay-type synthetic jet pump with Y-shaped jet chamber.

Recently, synthetic jet pumps have been expected to be used in electronic heat dissipation devices due to the vortex suction phenomenon for transporting fluids. Aiming to improve the delivery ability of the jet pump to output fluid continuously, a novel flat lay-type synthetic jet pump (FLTSJP) with a Y-shaped jet chamber is proposed in this paper. Based on the synthetic jet effect, the pump chamber continuously outputs fluid in one cycle. The output performance of FLTSJP is theoretically analyzed to be affected by the outlet cone angle. The one-cycle flow mechanism of the fluid in the Y-shaped jet chamber is simulated. FLTSJP is manufactured, and a test system is built. Experiments show that the Y-shaped jet chamber effectively improves the output performance. The optimum flow rate and outlet pressure were both reached at 160 V and 40 Hz, which were 20.63 ml/min and 333.43 Pa, respectively. This FLTSJP effectively improves the output performance of synthetic jet pumps and provides a new research concept of water-cooled devices for electronic heat dissipation.

A review of piezoelectric-electromagnetic hybrid energy harvesters for different applications.

Social progress is inseparable from the utilization of energy, signals of extreme consumption of fossil energy and energy crisis appear frequently around the world. Human beings are paying more and more attention to new technologies and the sustainable development of energy collection and conversion. The emergence of piezoelectric, electromagnetic, electrostatic, and triboelectric mechanisms provides a variety of effective methods for new environmental energy collection and conversion technologies. Among them, the piezoelectric-electromagnetic hybrid energy harvester (P-EHEH) has been widely studied due to its high output power, simple structure, and easy miniaturization. Continuous progress has been made in the research of P-EHEH through theoretical exploration, structural optimization, and performance improvement. This Review focuses on the review of P-EHEH at the application level. A detailed introduction summarizes the research status of P-EHEH applied to human body devices, monitoring sensors, and power supply devices, as well as the development status of back-end electronic modules and interface circuits. The future challenges and development prospects of P-EHEH are anticipated.

Design and research of piezoelectric energy harvesting device applicable to wireless mouse.

This paper presents a piezoelectric energy harvesting device applicable to wireless mouse (WM-PEH). Adding magnetic force to the excitation piezoelectric generating unit makes the impact better and more pronounced. The polygonal roller can increase the excitation frequency of the piezoelectric generating unit and broaden the energy collection range and capability of the WM-PEH. The theoretical and simulation analysis of WM-PEH was carried out in this paper. The effects of the length ratio of the exciter rod to the support frame and the circular impact area on the output characteristics of the prototype were discussed in the experiment. When the length ratio of the exciter rod and the support rod is 3:1, the activity increment of the exciter rod is the largest, and the maximum output voltage can reach 42 V and the maximum output power is 22.43 mW when it acts on a circular generator set with a radius of 1.5 mm. The design of the device is highly integrated with the wireless mouse that is widely used, and the piezoelectric energy harvesting mechanism and the wireless mouse are perfectly combined, which provides a scientific basis for the subsequent development of a self-powered wireless mouse.

Performance study of a valveless piezoelectric pump with built-in semi-arc bluffbody antique tower channel.

According to the bluffbody bypass effect, the irregular bluffbody can be used to improve the valveless piezoelectric pump. This paper designs a semi-arc bluffbody based on the bluffbody bypassing principle to alleviate the phenomenon of fluid backflow. The fluid passes through the shape of the antique tower to further enhance pumping efficiency. A positive fluid flow mechanism in the pump cavity is theoretically derived. The simulation of the velocity and pressure distribution in the tower-shaped channel of the pump cavity leads to the conclusion that the forward flow has better performance than the reverse flow, and the correctness of the theory is also verified. Experiments further proved that the volume of fluid in the forward direction was reduced by 10.8% when compared to the reverse direction. The study of the height of different semi-arc bluffbody and the angle of the tower trough shows that as the height and angle increase, the flow rate grows first and then reduces. The maximum flow rate is 243.83 ml/min when the bluffbody height is 4 mm and the channel angle is 20° (220 V, 85 Hz).

Sequential self-assembly of calix[4]resorcinarene-based heterobimetallic Cd8Pt8 nano-Saturn complexes.

A rational molecular design strategy is introduced for selective metal-ligand coordination, enabling the quantitative self-assembly of heterobimetallic nano-Saturn complexes. During the sequential multicomponent self-assembly, the CdII ions and organometallic trans-PtII motifs demonstrate preferential binding to specific ligands. The pre-designed directive interactions allow for precise control over the structural characteristics.

Nucleus high intensity in the T2-weighted MRI is a potential predictor of annulus tear in cervical injured patients: a case comparative study.

BACKGROUND: Segmental fusion operations assume paramount significance for individuals afflicted by full layers of annulus tears as they avert the perils of rapid disc degeneration and segmental instability. Structures with high signal intensity in the T2-weighted MRI can predict potential damage to the injured segment. Since local structures are shortly related biomechanically, this may be an effective predictor for annulus tears. METHODS: A retrospective analysis of the clinical data of 57 patients afflicted by cervical injuries and subjected to single-segment ACDF has been performed in this study. The surgeon performed intraoperative exploration to assess the integration status of the annulus. The signal intensity of the prevertebral space, nucleus, and injured vertebral bodies were judged in the T2-weighted imaging data. Regression analyses identified independent predictors for annulus tears, and the area under the receiver operating characteristic curve (AUC) was computed to evaluate the predictive performance of potential independent predictors. RESULTS: The occurrence of nucleus high intensity was significantly higher among individuals with annulus tears, and the nucleus high intensity was deemed an independent predictor for determining the presence of intraoperative visible annulus tears in patients with cervical injuries. AUC for nucleus high intensity was calculated as 0.717, with a corresponding p-value less than 0.05. CONCLUSIONS: In the realm of diagnosing annulus tears in injured cervical patients, nucleus high intensity in the T2-weighted MRI emerges as a promising predictive factor. Notably, this applies specifically to patients devoid of fracture and visible annulus tears in their MRI scans. Such positive outcomes should be regarded as prospective indications for ACDF.

A novel energy harvester based on dual vibrating mechanisms with self-actuation.

This paper introduced a novel energy harvester with a tunnel and drop-shaped bluffbody for self-actuation and wind speed sensing. The harvester exhibits dual vibrating mechanisms of vortex-induced vibration (VIV) and galloping. Theoretical and numerical analyses were conducted to study the energy conversion relationship and fluid field of the harvester, and the conclusions were verified by controlled variable experiments. The optimal design values of inlet angle I 40°, polyvinylidene fluoride (PVDF) angle P 10°, and exit angle E 10° were demonstrated with the highest output of 10.42 Vp-p at the wind speed of 18 m/s. The output voltage of the PVDF energy harvester has a reliable relationship with the wind speed as a function of wind speed sensor, which could be applied for meteorological information collection and fluid flow rate monitoring with further study conducted underwater.

Piezoelectric energy harvesting systems using mechanical tuning techniques.

In this review, we review the recent research progress and results of piezoelectric energy harvesters applying mechanical tuning techniques in terms of literature background, methods of mechanical tuning, and practical applications. In the past few decades, piezoelectric energy harvesting techniques and mechanical tuning techniques have received increasing attention and made significant progress. Mechanical-tuning techniques are those that allow the resonant vibration energy harvesters the mechanical resonant frequency values to be adjusted to coincide with the excitation frequency. According to the different tuning methods, this review classifies mechanical-tuning techniques based on magnetic action, different piezoelectric materials, axial load, the variable center of gravity, various stresses, and self-tuning and summarizes the corresponding research results, comparing the differences between the same methods. In addition, the current application of the mechanical-tuning techniques is introduced, and the future development of mechanical tuning techniques is analyzed, facilitating the reader to better understand how mechanical-tuning techniques can improve the output performance of energy harvesters.

A review of recent studies on valve-less piezoelectric pumps.

Due to the advantages of small size, low power consumption and price, no wear, and reliable performances of valve-less piezoelectric pumps, which academics have studied and gained excellent consequences for, valve-less pumps are applied in the following fields: fuel supply, chemical analysis, biological fields, drug injection, lubrication, irrigation of experiment fields, etc. In addition, they will broaden the application scope in micro-drive fields and cooling systems in the future. During this work, first, the valve structures and output capabilities of the passive valve and active valve piezoelectric pumps are discussed. Second, the various forms of symmetrical structure, asymmetrical structure, and drive variant structure valve-less pumps are introduced, the working processes are illustrated, and the advantages and disadvantages of pump characteristics with the flow rate and pressure are analyzed under different driving conditions. In this process, some optimization methods with theoretical and simulation analysis are explained. Third, the applications of valve-less pumps are analyzed. Finally, the conclusions and future development of valve-less piezoelectric pumps are given. This work attempts to provide some guidance for enhancing output performances and applications.

A composite energy harvester based on human reciprocating motion.

In this paper, a piezoelectric electromagnetic composite energy harvester is studied. The device consists of a mechanical spring, upper and lower base, magnet coil, etc. The upper and lower bases are connected by struts and mechanical springs and secured by end caps. The device moves up and down under the vibration of the external environment. As the upper base moves downward, the circular excitation magnet moves downward, and the piezoelectric magnet is deformed under a non-contact magnetic force. Traditional energy harvesters have the problems of a single form of power generation and inefficient energy collection. This paper proposes a piezoelectric electromagnetic composite energy harvester to improve energy efficiency. Through theoretical analysis, the power generation trends of rectangular, circular, and electric coils are obtained. Simulation analysis yields the maximum displacement of the rectangular and circular piezoelectric sheets. The device uses piezoelectric power generation and electromagnetic power generation to achieve compound power generation, improve the output voltage and output power, and can provide power supply to more electronic components. By introducing the nonlinear magnetic action, the mechanical collision and wear of the piezoelectric elements during the work are avoided, so that the service life and service life of the equipment is extended. The experimental results show that the highest output voltage of the device is 13.28 V when the circular magnets mutually repel rectangular mass magnets and the tip magnet of the piezoelectric element is 0.6 mm from the sleeve. The external resistance is 1000 Ω, and the maximum power output of the device is 5.5 mW.

Research on a rotary piezoelectric wind energy harvester with bilateral excitation.

This paper describes a rotary piezoelectric wind energy harvester with bilateral excitation (B-RPWEH) that improves power generation performance. The power generating unit in the current piezoelectric cantilever wind energy harvester was primarily subjected to a periodic force in a single direction. The B-RPWEH adopted a reasonable bilateral magnet arrangement, thus avoiding the drawbacks of limited piezoelectric cantilever beam deformation and unstable power generation due to unidirectional excitation force. The factors affecting the power generation were theoretically analyzed, and the natural frequency and excitation force of the piezoelectric cantilever have been simulated and analyzed. A comprehensive experimental research method was used to investigate the output performance. The B-RPWEH reaches a maximum output voltage of 20.48 Vpp when the piezoelectric sheet is fixed at an angle of 30°, the Savonius turbine number is 3, and the magnet diameter is 8 mm. By adjusting the fixed angle of the piezoelectric sheet, the number of Savonius wind turbine blades, and the magnet diameter, the maximum voltage is increased by 52.38%, 4.49%, and 245.95%, respectively. The output power is 24.5 mW with an external resistor of 8 kΩ, and the normalized power density is 153.14 × 10-3 mW/mm3, capable of powering light-emitting diodes (LEDs). This structure can drive wireless networks or low-power electronics.

Study on Micro-Displacement Mechanism and Reservoir Compatibility of Soft Dispersed Microgel.

Polymer flooding is a key technology for improving reservoir heterogeneity around the world, and it has made great progress. However, the traditional polymer has many shortcomings in the theory and application, which causes the efficiency of polymer flooding to gradually decrease and secondary reservoir damage after a long period of polymer flooding. In this work, a novel polymer particle (soft dispersed microgel, SMG) is used as the research object to further investigate the displacement mechanism and reservoir compatibility of SMG. The visualization experiments of the micro-model prove that SMG has excellent flexibility and can be highly deformable to realize deep migration through the pore throat smaller than SMG itself. The visualization displacement experiments of the plane model further show that SMG has a plugging effect, which makes the displacing fluid flow into the middle and low permeability layers, improving the recovery of these layers. The compatibility tests show that the optimal permeability of the reservoir for SMG-µm is 250-2000 mD, and the corresponding matching coefficient range is 0.65-1.40. For SMG-mm-, its corresponding optimal permeabilities of reservoir and matching coefficient are 500-2500 mD and 1.17-2.07, respectively. The comprehensive analysis demonstrates that the SMG has excellent ability of the water-flooding swept control and compatibility with reservoirs, having the potential to solve the problem of traditional polymer flooding.

Research on Adaptability Evaluation Method of Polymer by Nuclear Magnetic Resonance Technology.

In order to study the matching relationship between polymer(HPAM) molecular weight and reservoir permeability, in this paper, the injection performance of polymers with different molecular weights in rock cores with different permeability is studied. Using nuclear magnetic resonance technology combined with conventional core displacement equipment, the change law of the displacement process was analyzed from three aspects of nuclear magnetic resonance T2 spectrum, core layering, and imaging. Finally, the fluidity of the polymer solution in the core was analyzed by injection pressure control features. The experimental results show that the polymer solution with a molecular weight of 25 million has the best retention effect in the core flooding experiment and can stay in the dominant channel of the core for a long time to control the water flooding mobility. In rocks with a permeability of 500, 1000, and 2000 mD, subsequent water flooding can expand the swept volume by about 25% compared with polymer flooding. This method can effectively establish the adaptability matching relationship between the polymer molecular weight and the reservoir permeability.