Jet Dispenser Research Articles

Gravitational effects on optical lens fabrication: First insides on Earth- and microgravity experiments

Abstract Understanding the effects of gravity on manufacturing processes is a pioneering extension of the process parameter space used to date. Until now, the improvement of manufacturing technologies has mainly focused on process parameters such as temperature, pressure, and material composition, as access to variable gravity environments is limited. The Einstein-Elevator opens up new possibilities for the variation of these process parameters and the development of in-space manufacturing technologies. Together with the research of innovative production processes for optical components within the PhoenixD Cluster of Excellence, this creates an entirely new field of research. The research presented here focuses on investigating gravity's effects on dispensed optical lens production. Using a jet dispenser, sessile droplets are produced during a flight phase in the Einstein-Elevator and cured directly by UV polymerization. As part of this study, optical lenses were produced and compared under microgravity and Earth's gravitational conditions. Geometric properties such as height and contact angle of the lenses produced were analyzed. It was found that lenses fabricated under microgravity have a larger contact angle than those fabricated under Earth gravity. Similarly, the height increases with decreasing gravity. These results are consistent with the theoretical assumptions described, although generalized theories to describe the morphology of a sessile droplet are not yet available. The case study findings on the influence of gravity as a process parameter on drop morphology represent a fundamental improvement for additive manufacturing technologies, especially for in-space manufacturing.

Design and performance analysis of an embedded amplified piezoelectric jetting dispensing valve

Abstract In order to satisfy the market's demand for high-consistency, micro-dispensing of colloids, an embedded lever-amplified piezoelectric dispensing valve based on flexure hinge is designed. This structure has stable jetting performance, strong reliability, and can achieve micro-dispensing of medium and low viscosity glue. Theoretical analysis shows that the output displacement of the piezoelectric stack can meet the displacement requirement of dispensing after being amplified by this amplification mechanism. And the output displacement and mode of the amplification mechanism are calculated and analyzed by simulation. The rationality of the simulation model is verified by experiments, and the effect law of driving voltage, signal duty cycle and working frequency on the mass of glue droplets is obtained. The results show that under the conditions of driving voltage 100 V, duty cycle 50%, glue supply pressure 0.6 MPa, working frequency 100 Hz, the consistency deviation of single dispensing amount is ± 2.01%, as a whole, 0.34-0.38 mg of uniform tiny glue dots can be obtained. The experimental results have verified the stability and micro-dispensing performance of the embedded lever amplification piezoelectric dispensing valve, providing reference for the subsequent application and research of jet dispensing.

Optimizing dispensing performance of needle-type piezoelectric jet dispensers: a novel drive waveform approach

The dispensing performance of needle-type piezoelectric jet dispenser constitutes a crucial factor that ensures the quality of additive manufacturing processes. In this paper, a novel approach is proposed to enhance the dispensing performance of needle-type piezoelectric jetting dispensers by introducing a more adaptable driving waveform based on Bézier curves. Initially, the approach considers the electromechanical coupling effect of the needle-type piezoelectric dispenser and constructs a high-precision fluid–solid coupling model of the dispensing process. Subsequently, a multi-physics field joint simulation platform combining Matlab and Fluent is established to systematically analyze control strategies in real service conditions. Next, a new driving waveform based on Bézier curves is introduced, and the control parameters are optimized using a genetic algorithm to address issues such as air bubbles in the droplets and instability of the dispensing process. The optimized waveform based on the Bézier curve reduces the volume of air suction during the dispensing process by over 20% compared to the traditional waveform and eliminates the uncontrolled vibration state of the needle in the fluid, ensuring the stability of the entire fluid refill process. Finally, the optimized control strategy is verified through experiments and compared with traditional methods. The experiment demonstrates its advantages in addressing issues with no air bubbles in the droplets and consistency of the droplets. This study provides valuable insights into optimizing the dispensing performance of needle-type piezoelectric jetting dispensers regarding control strategy.

Sealing Design of Piezoelectric Jetting Dispenser and Its Influence on Jetting Performance

Sealing Design of Piezoelectric Jetting Dispenser and Its Influence on Jetting Performance

Assessing the efficacy of jet dispenser versus direct syringe injection for calcium hydroxide paste placement in artificial root canals

This study aimed to evaluate the efficacy of a novel jet dispenser (JD) for filling simulated straight and curved canals with calcium hydroxide (Ca(OH)2) paste by comparing the level of intracanal medicament with traditional direct syringe delivery. The Ca(OH)2 paste was delivered into the canals using either a direct syringe with binding tip and unbinding tip or a JD. The analysis of the ratio of the canal filled area (RCFA) in the coronal, middle, and apical thirds was conducted using the Kruskal–Wallis and Mann–Whitney U tests (α = 0.05). The JD resulted in a significantly higher RCFA of 1.00 in the middle and apical thirds in both the straight and curved canals than the direct syringe method (p < 0.001). Voids were frequently observed in the direct syringe group, whereas JD showed no voids within the filled area. In the direct syringe groups, the apical area was more readily filled in both canal types when the tip was bound (p < 0.001). The JD was found to be more effective in filling the entire canal space than the binding and unbinding conditions of the direct injection method, particularly in the apical area.

Design and Analysis of a Hybrid Displacement Amplifier Supporting a High-Performance Piezo Jet Dispenser

In this study, a compliant amplifier powered by a piezoelectric stack is designed to meet high-performance dispensing operation requirements. By studying the issue of low frequency bandwidth on the traditional bridge-type amplifier mechanism, we propose a displacement amplifier mechanism, hybrid bridge-lever-bridge (HBLB), that enhances its dynamic performance by combining the traditional bridge-type and lever mechanism. A guiding beam is added to further improve its output stiffness with a guaranteed large amplification ratio. An analytical model has been developed to describe the full elastic deformation behavior of the HBLB mechanism that considers the lateral displacement loss of the input end, followed by a verification through a finite element analysis (FEA). Results revealed that the working principle of the HBLB optimizes the structural parameters using the finite element method. Finally, a prototype of the displacement amplifier was fabricated for performance tests. Static and dynamic test results revealed that the proposed mechanism can reach a travel range of 223.2 μm, and the frequency bandwidth is 1.184 kHz, which meets the requirements of a high-performance piezo jet dispenser.

Design and Research of a Novel Piezostack-Driven Jetting Dispenser With a Diamond Spring

A novel piezoelectric jetting dispenser is proposed for microelectronic packaging in this article. It adopts a piezoelectric drive, a lever displacement amplifier, and a recovery system with double springs in a staggered position. The automatic dynamic analysis of mechanical systems (ADAMSs) simulation model of the dispenser is established and first applied to the study of the high-frequency response performance. The displacement curve and the velocity curve of the impactor are obtained at the frequency of 200 and 500 Hz. The test results prove that the ADAMS model is feasible. Based on dispensing experiments, the volume and the volume error of a drop at different dispensing frequencies are studied. The volume of a drop is 8.5 nL at the frequency of 800 Hz. The maximum relative error of the droplet volume is less than ±7.2% at the frequency of 200, 300, and 400 Hz.

The jetting process and spreading characteristics of the power-law fluids for material jetting process

Materials jetting, known as one of the 3D printing technologies, is widely applied in microelectronics packaging, biology and ceramic 3D printing due to its ability to print multi-materials by drop-on-demand. However, most of the materials are power-law fluids in 3D printing applications, the generation of satellites during the jetting process and droplet spreading characteristics are unclear and they have a great effect on the quality of the printout. In this paper, a common electromechanical and fluid-solid coupling model of the jet dispenser and observation platform of the jetting process are established. This modeling method is also suitable for other needle-driven jet dispensers. A commercial UV resin is adopted to study the jetting process of power-law fluid. To reveal the mechanism of satellite generation, the effects of input signals (rising time and falling time) on the dynamic characteristics of the needle and the jetting process are analyzed. On the basis thereof, the effectiveness of the optimal control parameters is demonstrated to eliminate satellites. In addition, the simulation and experimental results show that the falling time and fluid pressure can be controlled to adjust the spreading diameter and height of the droplet. Subsequently, the minimum line width of 0.276 mm is successfully printed with a nozzle of 0.07 mm.

The Design and Evaluation of a High-Speed Jet Dispenser Driven by Single Piezoelectric Stack.

Droplet injection methods are widely used in the applications of microelectronic manufacturing, biological engineering, and 3-D printing. This work presents a new jet dispenser driven by a single piezoelectric stack that enables the capability of drop-on-demand patterning under a high working frequency (500 Hz). Due to the special designs of the jet dispenser, a broad range of liquids, whose viscosities span more than four orders of magnitude (21-665 320 cps), can be jetted. Moreover, a coupled Coulomb damping physical model is proposed, which includes an electromechanical and a dynamic model. Both the Coulomb and the fluid-solid damping are considered in the dynamic model. In order to validate the results obtained by using MATLAB/Simulink, the experiments were carried out. The injection performance of this jet dispenser has been tested by employing a self-made jetting platform. The minimum volume of a jetting droplet is about 14.4 nL with liquid wax. The error of volume uniformity among droplets does not exceed 8%, and the error of angle trajectory is about 0.17°. Furthermore, the versatility of the jet dispenser is demonstrated by printing liquid lubricant, food, glue, silver past, and a ceramic slurry in predefined patterns.

Rigid flexible coupling dynamic analysis of piezoelectric jetting dispenser based on ADAMS

As dispensing technology needs accurate flow control, high performance spray dispensing has become the mainstream of dispensing technology. In this paper, the rigid flexible coupling dynamic simulation of piezoelectric jetting dispenser is carried out by using the dynamic simulation software ADAMS. In this process, the displacement and velocity of the needle under certain conditions are obtained. Then, according to the simulation results, the jetting dispenser driven by piezoelectric stack and the experimental test system are established. The dispensing process of the piezoelectric jetting dispenser is studied. The displacement of the needle in the dispensing process of the piezoelectric jetting dispenser is obtained by laser sensor, and the needle speed is obtained by analyzing the displacement of the needle. The experimental results are in good agreement with the simulation results, which proves the accuracy and feasibility of the simulation, and provides a method for the design and research of piezoelectric jetting dispenser.

Design, modeling, and performance analysis of a new dispensing system based on compliant mechanism.

Jet dispenser is widely used in microelectronic packaging, semiconductor industry, life science, and rapid manufacturing fields. As the requirement for dispensing accuracy and speed become higher and higher, especially for viscous materials, the traditional mechanisms cannot meet the high precision dispensing. This paper presents a new jetting dispenser using the complaint mechanism with amplifier components to design the dispenser, which gain the motion and force from the elastic deformation of flexible hinges. To describe the mechanical property of the jetting dispenser, the model of the jetting dispenser was built by employing a pseudo-rigid-body method. To predict accurately droplet volume, we established the model by describing the forming process of droplet. Furthermore, the errors of the droplet volume were analyzed based on the model. The prototype of the dispenser was built and the effects of driving voltage, radius of spray chamber, glue supply pressure, glue viscosity, and turn-on time of hammer on the droplet were analyzed experimentally. The analytical results are in good agreement with experimental results, which the advantages of the presented jetting dispenser with a new design concept are validated. This research provided a new idea and modeling method for the future application of the dispensing system.

Design and Simulation of Electromagnetic Linear Actuators for Jet Dispensers

Three electromagnetic-based linear actuators, namely a solenoid actuator (SA), a moving coil actuator (MCA), and a moving magnet actuator (MMA), are proposed for driving the needle in a jet dispenser. The total resistance force acting on the needle during operation, including the damping force, the friction force, the inertia force, the compression spring force, and the backpressure, are measured by an experimental model. The thrust force required to overcome this resistance force is then predicted for each actuator using finite element analysis (FEA) simulations. Simple two-dimensional models of the SA, MCA, and MMA are constructed using the same coil dimensions in every case in order to facilitate an objective comparison between them. Simulations in ANSYS Maxwell software are then performed to adjust the specific dimensions of each actuator structure in such a way as to generate the thrust force required to drive the needle in the jet dispenser with the minimum excitation current possible. The simulation results show that for a maximum needle driving frequency of 250 Hz and a stroke length of 0.5 mm, the excitation current required to generate the necessary thrust force is equal to 1.8 A and 1.9 A for the MCA and MMA models, respectively, when a return spring is not used, and 2.2 A, 3.8 A, and 4.1 A for the SA, MCA, and MMA models, respectively, when a return spring is employed. It is additionally shown that the thrust force drop of the MCA and MMA models is far less than that of the SA model, about 0.7%, 1.8%, and 61% for three models, respectively. Three preliminary designs for jet dispensers incorporating the proposed actuators are also generated for reference purposes.

Development of a Piezo-Driven Liquid Jet Dispenser with Hinge-Lever Amplification Mechanism.

Owing to the quick response, compact structure, high precision, huge blocking force generation, and ease of operation, piezoelectric actuators are urgently being adopted in the field of advanced dispensing for jetting performance improvement and fulfillment of precision requirements in microelectronics packaging, adhesive bonding, and miniaturization industry. This research focuses on the fundamental design and development of a piezo-electrically driven compact fluid dispenser using the principle of a class-one lever for amplification of needle displacement, and enhancement of application areas of the developed jet dispenser. Using fundamental lever principle, geometry-based modelling is carried out to fabricate a working prototype of a normally closed hinge-lever type dispenser. Preliminary experiments are carried out to witness the workability of the fabricated dispenser to deliver 100 dots of working fluid per second that will provide a novel device for dispensing of various fluids, and the proposed amplification mechanism suits various other piezoelectric applications as well.

Fuzzy PID based temperature controller for jetting dispenser

In order to reduce the temperature fluctuation of adhesives on jet dispenser, a fuzzy PID temperature controller was designed. An experimental platform was built on the jetting dispenser. The experimental result shows that the stability of the new system is better than that of the classic PID controller, and the temperature fluctuation is reduced by 0.5°C.

How to manipulate droplet jetting from needle type jet dispensers

The needle-type inkjet dispenser has been widely used for various research and industrial purposes. The droplet jetting from the dispenser is closely related to the needle motion, which strikes against the nozzle seat. The strike of the needle on the nozzle seat often cause additional impact due to the bounce back, which may produce multiple droplets per jetting trigger. However, the needle motion is difficult to measure, and the actual behaviors have been known little. In this study, we measured the needle motion using an accelerometer and visualized jetting images to understand jetting behavior in relation to the needle motion. Then, we investigated various parameter effects on needle motion and jetting behaviors based on our proposed measurement methods. From the experimental results, we found that needle travel distance should be in the optimal range in order to produce single droplet per jetting trigger. In conclusion, we proposed an effective parameter selection method for the optimal jetting based on understanding of the jetting physics.

Cost-Effectiveness of Water Promotion Strategies in Schools for Preventing Childhood Obesity and Increasing Water Intake.

This study aimed to estimate the cost-effectiveness and impact on childhood obesity of installation of chilled water dispensers ("water jets") on school lunch lines and to compare water jets' cost, reach, and impact on water consumption with three additional strategies. The Childhood Obesity Intervention Cost Effectiveness Study(CHOICES) microsimulation model estimated the cost-effectiveness of water jets on USchildhood obesity cases prevented in 2025. Also estimated were the cost, number of children reached, and impact on water consumption of the installation of water jets and three other strategies. Installing water jets on school lunch lines was projected to reach 29.6 million children (95% uncertainty interval [UI]: 29.4million-29.8 million), cost $4.25 (95% UI: $2.74-$5.69) per child, prevent 179,550 cases of childhood obesity in 2025 (95% UI: 101,970-257,870), and save $0.31 in health care costs per dollar invested (95% UI: $0.15-$0.55). In the secondary analysis, installing cup dispensers next to existing water fountains was the least costly but also had the lowest population reach. Installating water jet dispensers on school lunch lines could also save almost half of the dollars needed for implementation via a reduction in obesity-related health care costs. School-based interventions to promote drinking water may be relatively inexpensive strategies for improving child health.

The effect of adjusting the stroke value of jet dispenser on the performance of glucose biosensor with gold-plated electrode.

This study investigates the effect of dispensing glucose oxidase enzyme onto the reaction zone of a golden electrode via a jetting dispenser. Each droplet of enzyme solution dispensed onto the reaction zone of golden electrode weighs exactly the same at around 0.4 mg. This study shows that the spring and needle assembly can be controlled by adjusting the stroke value of the stroke adjustment knob to generate different jet dispensing effects, thus affecting the change of droplets of glucose oxidase enzyme solution within the reaction zone of the golden electrode. This study performs experiments using three stroke values, which are 0.8, 1.2, and 1.6 mm. The experimental results show that adjusting the stroke value to change the droplet of the dispensing liquid will significantly affect the accuracy of the test strip reading value. When the stroke value is adjusted to 1.5 mm, the standard deviation of the test strip is 3.8 mg/dL and the coefficient of variation is 4.1%-6.1%. The study suggested that adjusting the stroke value can stabilize the dispensed droplet to increase the stability of test strip reading, improving the accuracy of the test strip reading. This adjustment method can also be applied to the process of other biochemical sensors.

Simulation and Experiment on Droplet Volume for the Needle-Type Piezoelectric Jetting Dispenser.

The needle-type piezoelectric jetting dispenser is widely applied in the microelectronics packaging field, and it is important to control the droplet size to ensure that the droplet jetting process is successful. In this study, we analyzed the influences of system parameters, such as air pressure, nozzle size, needle strokes, and liquid properties, on droplet size and morphology by considering the droplet formation and separation process through a numerical simulation. An experimental platform was also designed to verify the reliability of the simulations and further analyze strategies for controlling the droplet size. We found that the droplet volume can be increased with an increase in air pressure, needle strokes, and nozzle size until the flow-stream or satellite droplets appear. On the other hand, very small values of these parameters will lead to adhesion or micro-dots. A large nozzle and needle displacement should be chosen for the high-viscosity liquid in order to produce normal droplets. The results also show the recommended ranges of parameter values and suitable droplet volumes for liquids with different viscosities, and these findings can be used to guide the droplet volume control process for needle-type jetting dispensers.

Design and Experiment of a Moving Magnet Actuator Based Jetting Dispenser

Developing actuators to drive high-frequency jetting dispensers in the dispensing technology for electronic assembly applications has become a concern in recent years. This study proposed a new jetting dispenser without a displacement amplification mechanism directly actuated by a moving magnet actuator (MMA) to jet small fluid droplets. In this article, the main geometric dimensions of the dispensing cluster including the needle, chamber, and seat-nozzle follow those of previous studies and existing dispensers to reduce design time. The necessary root-mean-square force applied to the dispenser needle, which is the key value for the MMA design, is calculated in detail. An ANSYS Maxwell finite element analysis (FEA) is used to simulate the MMA thrust force and modify geometric dimensions. The droplet size produced by the proposed dispenser is empirically investigated under various backpressure, operating frequency, needle displacement, and fluid temperature conditions. The experimental results indicated that the jet dispenser driven by the moving magnet actuator stably operated at the maximal operating frequency of 80 Hz. Some errors, such as losing droplets and generating small satellite dots around the main dots, did not occur during the operating process. In addition, the size of the proposal dispenser without the displacement-magnifying mechanism was also significantly reduced. To conclude, the jetting dispenser driven by the proposal moving magnet actuator can operate well at a medium frequency and shows great potential for dispensing technologies.

Influence of needle impact velocity on the jetting effect of a piezoelectric needle-collision jetting dispenser

Many scholars have conducted in-depth analysis on relevant factors that affect the accuracy of jet dispensing. However, research on the influence of needle impact velocity on jetting performance is limited. Thus, a piezoelectric needle-collision dispenser for micro-droplet jetting is designed in this study, and the influence of the needle impact velocity on jetting effect is deeply analyzed. Initially, the principle of droplet formation and injection is analyzed by Fluent simulation. Thereafter, the mathematical model of the droplet velocity in the nozzle orifice is derived, and the influence of the needle impact velocity on the jetting performance is simulated and analyzed. Results show that the needle impact velocity has an influence on the jetting effect. A prototype of the jetting dispenser is subsequently fabricated, and the needle impact velocity is tested with laser micrometer. The relationship between the needle impact velocity and droplet weight and its corresponding ejected effect are obtained through experimental research. Finally, a UV glue with viscosity of 5,000 cps can be ejected with a minimum average diameter of 272.1 μm by using a needle with a radius of 0.5 mm, a nozzle with a diameter of 50 μm, a taper angle of 90°, a supply pressure of 0.2 Mpa, and a needle impact velocity of 0.13 m/s. The variation of the droplet diameter is within ±2.5%.