Study on the Influencing Factors of the Atomization Rate in a Piezoceramic Vibrating Mesh Atomizer

Cavitation is the determining mechanism for the atomization of high-viscosity liquid

Piezoelectric atomization is becoming mainstream in the field of inhalation therapy due to its significant advantages. With the rapid development of high-viscosity gene therapy drugs, the demand for piezoelectric atomization devices is increasing. However, conventional piezoelectric atomizers with a single-dimensional energy supply are unable to provide the energy required to atomize high-viscosity liquids. To address this problem, our team has designed a flow tube internal cavitation atomizer (FTICA). This study focuses on dissecting the atomization mechanism of FTICA. In contrast to the widely supported capillary wave hypothesis, our study provides evidence in favor of the cavitation hypothesis, proving that cavitation is the key to atomizing high-viscosity liquids with FTICA. In order to prove that the cavitation is the key to atomizing in the structure of FTICA, the performance of atomization is experimented after changing the cavitation conditions by heating and stirring of the liquids.

Aerosolization Performance of Immunoglobulin G by Jet and Mesh Nebulizers

Recently, many preclinical and clinical studies have been conducted on the delivery of therapeutic antibodies to the lungs using nebulizers, but standard treatment guidelines have not yet been established. Our objective was to compare nebulization performance according to the low temperature and concentration of immunoglobulin G (IgG) solutions in different types of nebulizers, and to evaluate the stability of IgG aerosols and the amount delivered to the lungs. The output rate of the mesh nebulizers decreased according to the low temperature and high concentration of IgG solution, whereas the jet nebulizer was unaffected by the temperature and concentration of IgG. An impedance change of the piezoelectric vibrating element in the mesh nebulizers was observed because of the lower temperature and higher viscosity of IgG solution. This affected the resonance frequency of the piezoelectric element and lowered the output rate of the mesh nebulizers. Aggregation assays using a fluorescent probe revealed aggregates in IgG aerosols from all nebulizers. The delivered dose of IgG to the lungs in mice was highest at 95 ng/mL in the jet nebulizer with the smallest droplet size. Evaluation of the performance of IgG solution delivered to the lungs by three types of nebulizers could provide valuable parameter information for determination on dose of therapeutic antibody by nebulizers.

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.

Research on the Machinability of Micro-Tapered Hole Group in Piezoelectric Atomizer and the Improvement Method

A metal atomizing sheet with a group of micro-tapered holes is the core constituent of a piezoelectric atomizer. However, the diameters of large-end and small-end micro-tapered holes in industrial applications deviate from the design values by 15.25% and 15.83%, respectively, which adversely impacts the effect of atomizers. In this study, two main factors that influence the machining quality of tapered holes, the external vibration disturbance and the internal system errors inside the laser processor, were explored; consequently, the vibration model of the machining device and the laser drilling model were established, respectively. Based on the models and the experimental results, it was found that the errors in diameter caused by these two factors accounted for 20% and 67.87% of the total deviation, respectively. Finally, an improved method was proposed, where a damping system was added to the machining device, and the diameter of the initial laser spot was corrected. The measurement results of tapered holes machined by the improved method showed that the deviation of the large diameters and the small diameters from the design values declined to 4.85% and 4.83%, respectively. This study lays a foundation for the high-precision and large-scale industry of atomizing sheets, and provides a new research direction for enhancing the performance of atomizers.

Numerical simulation and experimental verification of a valveless piezoelectric pump based on heteromorphic symmetric bluff body

To improve the output performance of valveless piezoelectric pumps, this paper designed a heteromorphic symmetrical bluff body based on the Karman vortex street principle, to optimize the flow direction and velocity of the liquid. The bluff body dome height, trapezoidal unilateral angle, and rounded corner structure height at different dimensional parameters and their relationship with the pump performance were studied. The pump pressure in both positive and negative directions was simulated and analyzed. At last, a prototype of the pump was made and the output performance was tested. The experimental results show that the maximum flow rate reaches 220.6 ml/min at 190 V, 45 Hz when the bluff body dome is 8 mm, the trapezoidal unilateral angle is 5°, and the rounded corner structure is 6 mm. Moreover, when the driving voltage is 190 V and the driving frequency is 130 Hz, the maximum output pressure reaches 670 Pa.

Spray characteristics of an ultrasonic microdroplet generator with a continuously variable operating frequency

Droplet spraying is utilized in diverse industrial processes and biomedical applications, including nanomaterial synthesis, biomaterial handling, and inhalation drug delivery. Ultrasonic droplet generators transfer energy into bulk liquids using acoustic waves to disrupt the free liquid surface into fine microdroplets. We previously established a method combining ultrasonic actuation, resonant operation, and acoustic wave focusing for efficient spraying of various liquids (e.g., low surface tension fuels, high viscosity inks, and suspensions of biological cells). The microfabricated device comprises a piezoelectric transducer, sample reservoir, and an array of acoustic horn structures terminated by microscale orifices. Orifice size roughly dictates droplet diameter, and a fixed reservoir height prescribes specific device resonant frequencies of operation. Here, we incorporate a continuously variable liquid reservoir height for dynamic adjustment of operating parameters to improve spray efficiency in real-time and potentially tune the droplet size. Computational modeling predicts the system harmonic response for a range of reservoir heights from 0.5 to 3 mm (corresponding to operating frequencies from ∼500 kHz to 2.5 MHz). Nozzle arrays with 10, 20, and 40 μm orifices are evaluated for spray uniformity and stability of the active nozzles, using model predictions to explain the experimental observations.

Research and experimental verification of the characteristics of asymmetric multi-stage fluid guiding body piezoelectric pump

Valveless piezoelectric pumps usually have less flow than valve piezoelectric pumps, but the valve piezoelectric pumps have some limitations, such as high cost, complex structure, and difficult installation. In order to solve the problem of the low flow rate of the valveless piezoelectric pump, a valveless piezoelectric pump with multi-stage fluid guiding bodies is proposed. Based on the structure and working principle of the piezoelectric pump, the forward energy loss equation is established, and analysis on parameters affecting the energy loss of the pump is then conducted. COMSOL Multiphysics is adopted to construct a two-dimensional model of velocity and von Mises stress distribution. The valveless piezoelectric pumps were then fabricated based on 3D printing technologies, and the prototypes were tested. The results show that the output performance of the pump is the best when the working voltage is 220 V, the frequency is 95 Hz, the length of the oblique arm of the fluid guiding body is 3.5 mm, the spacing is 9.05 mm, and the thickness is 0.1 mm. The maximum flow rate is 520.6 ml/min. In addition, the experimental results prove that the asymmetric fluid guiding body placed in the center of the pump chamber can improve the performance of piezoelectric pumps. This study extends the application of piezoelectric valveless pumps in micromechanical cooling.

Parametric analysis of the output performance of a valveless piezoelectric pump with a bullhorn-shaped structure

In response to the serious problem of backflow in valveless piezoelectric pumps, this paper proposes a valveless piezoelectric pump with a bullhorn-shaped structure. In this paper, we analyze the flow guide by using the "tail flow space pressure comparison method" and "fluid unit dynamic analysis method," revealing the working principle of the flow guide in the valveless piezoelectric pump. The effects of the height, sharp angle, and filter angle of the bullhorn-shaped structure on the output flow were investigated separately by the experiment. The experimental results show that the output flow rate is best when the height of the bullhorn structure is 2 mm, the choke of the bullhorn-shaped structure is 2, and the sharp angle and fillet angle are 180°. The output flow rate of this valveless piezoelectric pump can reach 170.6 ml/min at a drive voltage of 210 V and a drive frequency of 45 Hz, indicating that the valveless piezoelectric pump has good pumping capability and can effectively alleviate the backflow phenomenon. This study offers some valuable insights into improving its performance and practical application.

Advances in Piezoelectric Jet and Atomization Devices

In recent years, the piezoelectric jet and atomization devices have exhibited tremendous advantages including their simple construction, and the fact that they are discreet and portable as well as low cost. They have been widely used in cell printing, spray cooling, drug delivery, and other industry fields. First, in this paper, two different concepts of jet and atomization are defined, respectively. Secondly, based on these two concepts, the piezoelectric jet and atomization devices can be divided into two different categories: piezoelectric micro jet device and piezoelectric atomization device. According to the organizational structure, piezoelectric micro jet devices can be classified into four different models: bend mode, push mode, squeeze mode, and shear mode. In addition, their development history and structural characteristics are summarized, respectively. According to the location of applied energy, there are two kinds of piezoelectric atomization devices, i.e., the static mesh atomization device and the vibration mesh atomization device, and both their advantages and drawbacks are discussed. The research achievements are summarized in three aspects of cell printing, spray cooling, and drug delivery. Finally, the future development trends of piezoelectric jet and atomization devices are prospected and forecasted.

Effects of Vibration Characteristics on the Atomization Performance in the Medical Piezoelectric Atomization Device Induced by Intra-Hole Fluctuation

Oral inhalation of aerosolized drugs has be widely applied in healing the affected body organs including lesions of the throat and lungs and it is more efficient than those conventional therapies, such as intravenous drip, intramuscular injection and external topical administration in the aspects of the dosage reduction and side effects of drugs. Nevertheless, the traditional atomization devices always exhibit many drawbacks. For example, non-uniformed atomization particle distribution, the instability of transient atomization quantity and difficulties in precise energy control would seriously restrict an extensive use of atomization inhalation therapy. In this study, the principle of intra-hole fluctuation phenomenon occurred in the hole is fully explained, and the produced volume change is also estimated. Additionally, the mathematical expression of the atomization rate of the atomizing device is well established. The mechanism of the micro-pump is further clarified, and the influence of the vibration characteristics of the atomizing film on the atomization behavior is analyzed theoretically. The curves of sweep frequency against the velocity and amplitude of the piezoelectric vibrator are obtained by the Doppler laser vibrometer, and the corresponding mode shapes of the resonance point are achieved. The influence of vibration characteristics on atomization rate, atomization height and atomization particle size are also verified by experiments, respectively. Both the experimental results and theoretical calculation are expected to provide a guidance for the design of this kind of atomization device in the future.