Piezoelectric Micropump Research Articles

Enhancing boiling heat transfer by high-frequency pulsating jet with piezoelectric micropump

Two-phase jet impingement provides a compact cooling solution capable of dissipating high heat flux at a low pressure drop, making it favorable for electronic cooling. However, there is still a limited understanding of the boiling characteristics of high-frequency pulsating jets. To address this knowledge gap, experiments are conducted using a piezoelectric micropump to study the boiling heat transfer characteristics. The frequency of the pulsating jet was controlled by adjusting the applied signal of the piezoelectric micropump, ranging from 10 Hz to 40 Hz. Both steady jet boiling and pulsating jet boiling were investigated using two nozzle configurations, with the flow rate varying from 30 to 120 ml/min. It is found that the high-frequency pulsating jet can significantly improve the critical heat flux (CHF) to 245.2 W/cm2 at the flow rate of 60 ml/min, 84% higher than that of the steady jet. But the high-frequency pulsating jet shows no markable effects on the heat transfer coefficient within the studied parameters. This research also discussed the mechanism behind the CHF enhancement, which provides valuable insight into jet impingement boiling under flow pulsation. Furthermore, the proposed two-phase cooling system is suitable for high-power-density electronics owing to its compactness and high thermal performance.

A Universal Piezoelectric Micropump With Capabilities of Self-Cleaning, Stable Filtration and Precise Pumping

The micro liquid supply system based on piezoelectric micropump has been deeply studied. However, it is difficult to realize stable and efficient filtration in quantitative liquid supply due to the blockage of filter membrane. In this work, we propose a self-cleaning filtration and pumping system based on piezoelectric micropump, which can realize stable and long-term directional quantitative filtration and pumping at the same time. The self-cleaning of the filter membrane is realized by using its reflux characteristics and the blockage problem of the current microfiltration system is solved. The key structure size of the system is optimized to realize continuous self-cleaning of filter membrane and high efficiency transportation of micro fluid. The control methods of pumping and filtration performance are proposed. Experiments results shows that the transmembrane pressure tends to be stable after about 4 pulse voltages which proves that the continuous self-cleaning is achieved. The reflux rate can be reduced to 25%, and the minimum pumping volume control accuracy is about 40 nL per cycle. This work can be used as a reference for microanalysis systems that need stable filtration and on-demand liquid supply.

Microscale damper prototype: A preliminary study on suppressing air flow oscillations within microchannels

This research introduces a novel micro-damper designed to mitigate pressure and velocity oscillations from a piezoelectric micropump in microfluidic environments. Unlike existing research focusing on damping in incompressible liquid flows with methods like elastic films and PDMS membranes, this study proposes a novel micro-damper prototype. Integrated into a microdevice for particle granulometric separation and detection, the damper connects to a piezoelectric micropump outlet and to a focusing microchannel inlet, followed by a capacitive sensor for size-based particle counting. Preliminary analysis determined an optimal airflow velocity at w = 0.5 m/s for accurate focusing and counting under laminar conditions. The micro-damper, constrained by the piezoelectric pump’s geometry, features a 27 µm high and 1000 µm wide cross section. Its outlet supports two potential focusing microchannel inlet configurations of 30 µm or 40 µm. Distinctively, it incorporates two symmetrical backward micro-channels connecting to the atmosphere, allowing direct piezometric contact between the main flow and an infinite compliant volume. OpenFOAM simulations confirm the damper’s effectiveness in maintaining laminar outlet flow and suppressing micropump disturbances. Thus, the proposed micro-damper ensures optimal inlet conditions for subsequent microchannel processes, enabling stable particle separation and detection in controlled airflow samples.

Silicon-Based Piezo Micropumps Enable Fully Flexible Drug Delivery Patterns

Drug release plays a crucial role in drug delivery. While current formulation approaches are capable of coarse-tuning the release profile, their precision and reproducibility are limited by the physicochemical properties of the excipients and active pharmaceutical ingredient (API). Innovative and advanced approaches are urgently needed, especially for site-specific targeting of drugs and to address their pharmacological requirements for optimal therapy. The 5 × 5 × 0.6 mm3 piezoelectric micropump developed by Fraunhofer EMFT was designed to enable precise drug delivery in a low volume format. In this study, we investigated the ability of the micropump to deliver solutions of highly soluble APIs using a wide range of customized pump profiles. Additionally, we examined the ability of the micropump to deliver suspensions containing various defined particle sizes. While results for suspensions indicate that pumping performance is highly dependent on the size and concentration of the suspended particles, results with API solutions demonstrate high precision and reproducibility of release, coupled with maximum flexibility in the release profile of the API. The piezoelectric micropump thus lays the cornerstone in the development of a wide range of innovative drug delivery profiles, enabling customized release profiles to be programmed and thus paving the way to fully personalized medicine.

Low-cost 3D printed inertial flow microfluidic devices for cellular isolation in liquid biopsies

Microfluidic devices for biomedical applications manufactured by conventional lithography often lack flexibility in design integration. Limitations in aspect ratio or in the ability to integrate microfluidic elements located in different planes reduce the available design options. Regarding this, 3D printing offers several advantages over traditional fabrication techniques. However, 3D printing technologies indeed show some limitations in the resolution of the microstructures obtained in comparison with standard lithography. We have optimized a low-cost multi-system combining standard lithography and 3D printing to design inertial flow microfluidic devices with different channels dimensions for cell concentration or isolation in blood, which are adaptable to cancer tumor cell (CTC) detection in liquid biopsies. CTC separation from complete blood using microfluidic devices often faces the challenge of leukocyte contamination due to their similar size with CTC. However, with 3D printing, we can create larger channels than those produced through lithography, enabling the use of beads coated with antibodies that bind to leukocytes expressing the CD45+ receptor. This binding results in larger particles that could be separated from the CTCs in the microfluidic devices, providing a more purified CTC sample. Microfluidic spiral structures were obtained with standard lithography for a first purification step using rectangular channel of 152 µm height and 500 µm width channels. The blood samples after processingE were analyzed by flow cytometry and revealed a recovery efficiency using two different CTC models of 80% ± 4% and 95% ± 4%. Also, the system enables 97.5% ± 1.89% and 83.4% ± 3.6% depletion of erythrocytes and leukocytes respectively. In addition, single or double microfluidic spiral structures to reduce leukocyte contamination using beads were directly fabricated using stereolithography 3D printing. In the single device with a channel of 600 μm and 1.4 mm of height and width respectively, and in the case of the device with two spirals placed on different planes, with a channel of 800 μm and 1.4 mm of height and width respectively. In addition, a read-out system based on an electronic circuit with piezoelectric micropumps, and a low-cost optical microscope was designed and adapted. This configuration avoids usual limitations when using syringe pumps and big microscopes, such as lack of sample recirculation, loss of CTCs during stabilization, blood sedimentation in the syringe, and reduced portability. Finally, combining a microfluidic spiral to separate red blood cells and partially leucocytes with the 3D microfluidic spiral to separate particles as the beads coated with CD45+ antibodies, could be possible to achieve a total leukocyte depletion up to 91%, and a maximum recovery of cancer cells up to 95%.

Internal flow characteristics of the valveless piezoelectric micropump with the diffusion/nozzle tube

A simulation was conducted to research the unsteady flow properties of the valveless piezoelectric micropump with diffusion/nozzle tube at different angles in the case of various driving frequencies using CFX software in this study. The purpose was to obtain the factors that affect the performance of the micropump under unsteady conditions. The results show that the rate of flow of the valveless piezoelectric micropump with different diffusion angles increases with the increase of frequency. The micropump with a diffusion angle of 10° has the best performance and the maximum rate of flow within the frequency range of 100 Hz~500 Hz, and the efficiency of the micropump can be reached 16.98%. The vortex motion generated due to flow separation has a notable effect on the performance of the micropump.

P(VDF/TrFE) Thin‐Film Piezoelectric Actuators Sealed Parylene C for Medical Micropumps

Wearable piezoelectric micropumps may contribute to improving drug delivery in the field of medicine. Poly(vinylidene fluoride/trifluoroethylene) (P(VDF/TrFE)), an organic ferroelectric polymer, is a desirable material for fabricating the piezoelectric layer of medical micropumps owing to its biocompatibility and flexibility. However, a large voltage is required to drive the micropumps because the piezoelectric response of P(VDF/TrFE) is small compared with that of inorganic materials, such as lead zirconate titanate. In this study, thin films (P(VDF/TrFE)) are focused that can reduce applied voltage and improve the flexibility of entire actuators. In addition, actuators sealed with poly(monochloro‐paraxylene) (Parylene C) are considered, which has excellent chemical resistance, flexibility, and biocompatibility. The calculated piezoelectric constant |e31| of the fabricated P(VDF/TrFE) thin films is 42 mC m−2. A large deformation of 1 mm is observed in the fabricated cantilever‐type actuators sealed with Parylene C when a voltage of 160 V is applied. Furthermore, the vibration of the actuators by the reverse piezoelectric effect on the water surface is observed. It is indicated in these results that a low voltage can safely drive P(VDF/TrFE) thin‐film piezoelectric actuators sealed with Parylene C in medical micropumps.

Design and simulation of a MEMS-based piezoelectric micropump for bio-medical applications

PurposeThe purpose of this paper is to design and simulate a piezoelectric micropump using microelectromechanical systems technology for drug delivery applications.Design/methodology/approachTwo piezoelectric actuators are used to actuate and bend the diaphragms in the proposed structure. In this micropump, the liquid flow is rectified by two silicon check valves.FindingsThe use of two piezoelectric transducer (PZT) actuators in the parallel mod not only reduces dead volume but also increases stroke volume as well. In addition to increasing the flow rate, this phenomenon enhances the operation of the micropump to have self-priming as smoothly as possible.Originality/valueThis actuating method results in a 22% increase in flow rate and compression ratio, as well as a 15% reduction in function voltage. The fluid-solid interaction is simulated using COMSOL Multiphysics 5.3a.

Flow Ripple Reduction in Reciprocating Pumps by Multi-Phase Rectification.

Reciprocating piezoelectric micropumps enable miniaturization in microfluidics for lab-on-a-chip applications such as organs-on-chips (OoC). However, achieving a steady flow when using these micropumps is a significant challenge because of flow ripples in the displaced liquid, especially at low frequencies or low flow rates (<50 µL/min). Although dampers are widely used for reducing ripples in a flow, their efficiency depends on the driving frequency of the pump. Here, we investigated multi-phase rectification as an approach to minimize ripples at low flow rates by connecting piezoelectric micropumps in parallel. The efficiency in ripple reduction was evaluated with an increasing number (n) of pumps connected in parallel, each actuated by an alternating voltage waveform with a phase difference of 2π/n (called multi-phase rectification) at a chosen frequency. We introduce a fluidic ripple factor (RFfl.), which is the ratio of the root mean square (RMS) value of the fluctuations present in the rectified output to the average fluctuation-free value of the discharge flow, as a metric to express the quality of the flow. The fluidic ripple factor was reduced by more than 90% by using three-phase rectification when compared to one-phase rectification in the 2-60 μL/min flow rate range. Analytical equations to estimate the fluidic ripple factor for a chosen number of pumps connected in parallel are presented, and we experimentally confirmed up to four pumps. The analysis shown can be used to design a frequency-independent multi-phase fluid rectifier to the desired ripple level in a flow for reciprocating pumps.

Drive simulation analysis of piezoelectric valveless micropump based on ZnO nanorod array

In this paper, ZnO nanorods are combined with the driving mechanism of a piezoelectric micropump to design a valveless piezoelectric micropump. The ZnO nanorods were prepared by the magnetron sputtering method to grow the ZnO seed crystal layer on the silicon surface and then by hydrothermal method. The growth of ZnO nanorods under different solution concentrations, solution temperatures, and growth times was investigated, and analytical methods for analyzing the surface morphology and elemental content of ZnO nanorods. Then, the simulation of the valveless micropump using ZnO nanorods prepared under optimal conditions as piezoelectric oscillators were carried out using COMSOL finite element analysis software, and the maximum output flow rate of about 14.40 μL/s was achieved at 100 V50 Hz.

Performance Optimization of Nozzle-Diffuser Piezoelectric Micropump with Multiple Vibrating Membranes by Design of Experiment (DOE) Method

During recent years, microfluidics based microelectromechanical systems (MEMSs) have found multiple applications in biomedical engineering. One of their most important implementations is fluid transfer in microliter and nanoliter scales. Nowadays, micropumps are extensively used in various medical applications such as drug delivery. In this study, the performance of a piezoelectric micropump is investigated and optimized. This micropump consists of a pump chamber and three deformable walls in a nozzle-diffuser shape, which are used to create pressure gradient between the inlet and outlet. The performance of the micropump is evaluated by transient Computational Fluid Dynamics (CFD) simulation using dynamic mesh. Then its performance is optimized using the Design of Experiment (DOE) method based on mean net outlet mass flow rate and flow reversibility at the pump outlet. The results indicate an improvement of 34.5% in mean net outlet mass flow rate and a significant decrease in reversibility. The maximum mean net outlet mass flow rate and the minimum reversibility corresponding to the optimum geometries are 95.82 mL/min and 0.05%, respectively.

Self‐Powered Piezoelectric Actuation Systems Based on Triboelectric Nanogenerator

AbstractSustainable power supply via triboelectric nanogenerator (TENG) is attractive for self‐powered actuation systems in the era of the Internet of Things (IoTs). Herein, a low‐power actuation scheme enabled by the multilayered TENG for piezoelectric actuators, including the stack, unimorph, and micro‐fiber composite (MFC) actuator, is reported. The working principles of TENG‐powered piezoelectric actuators and their displacement characteristics in direct current (DC) and alternating current (AC) modes are theoretically investigated. Compared with conventional high‐voltage power sources, the multilayered TENG delivers a maximum power of only 10.17 mW, providing a low‐power alternative for piezoelectric actuator with self‐powered capability and operational safety. Meanwhile, the hysteresis of the stack actuator that is critical in precise positioning control is reduced by 58.1%. A precise positioning system is demonstrated by utilizing the TENG‐powered stack actuator as an object stage for microscope focusing applications. The feasibility of vibration control with a 76.7% reduction in vibration amplitude is also verified via two TENG‐powered MFC actuators. A rectifying control circuit comprising the rectifier and gas discharging tube is established to implement AC–DC conversion and discharging control, achieving a larger displacement of the unimorph actuator. The TENG‐powered piezoelectric micropump demonstrates its potential application in liquid transport through straightforward operation.

Analytical and experimental study of a valveless piezoelectric micropump with high flowrate and pressure load

Miniaturized gas pumps based on electromagnetic effect have been intensively studied and widely applied in industries. However, the electromagnetic effect-based gas pumps normally have large sizes, high levels of noises and high power consumption, thus they are not suitable for wearable/portable applications. Herein, we propose a high-flowrate and high-pressure load valveless piezoelectric micropump with dimensions of 16 mm*16 mm*5 mm. The working frequency, vibration mode and displacement of the piezoelectric actuator, the velocity of gas flow, and the volume flowrate of the micropump are analyzed using the finite element analysis method. The maximum vibration amplitude of the piezoelectric actuator reaches ~29.4 μm. The output gas flowrate of the pump is approximately 135 mL/min, and the maximum output pressure exceeds 40 kPa. Then, a prototype of the piezoelectric micropump is fabricated. Results show that performance of the micropump is highly consistent with the numerical analysis with a high flowrate and pressure load, demonstrated its great potential for wearable/portable applications, especially for blood pressure monitoring.

Multistage Micropump System towards Vacuum Pressure

Fraunhofer EMFT’s research and manufacturing portfolio includes piezoelectrically actuated silicon micro diaphragm pumps with passive flap valves. Research and development in the field of microfluidics have been dedicated for many years to the use of micropumps for generating positive and negative pressures, as well as delivering various media. However, for some applications, only small amounts of fluid need to be pumped, compressed, or evacuated, and until now, only macroscopic pumps with high power consumption have been able to achieve the necessary flow rate and pressure, especially for compressible media such as air. To address these requirements, one potential approach is to use a multistage of high-performing micropumps optimized to negative pressure. In this paper, we present several possible ways to cascade piezoelectric silicon micropumps with passive flap valves to achieve these stringent requirements. Initially, simulations are conducted to generate negative pressures with different cascading methods. The first multistage option assumes pressure equalization over the piezo-actuator by the upstream pump, while for the second case, the actuator diaphragm operates against atmospheric pressure. Subsequently, measurement results for the generation of negative gas pressures down to −82.1 kPa relative to atmospheric pressure (19.2 kPa absolute) with a multistage of three micropumps are presented. This research enables further miniaturization of many applications with high-performance requirements for micropumps, achievable with these multistage systems.

Fluid-structure interaction and experimental studies of passive check valve based piezoelectric micropump for biomedical applications

ABSTRACT The piezoelectric micropump can be a prominent component of drug delivery systems due to its high performance, low cost, and faster response. However, backpressure remains to be the most common problem in micropump technology. Thus, microvalves or the passive check valve based piezoelectric micropump can be used to prevent the backpressure. However, the complex structure of the passive check valve based micropump limits the investigations of Fluid-Structure Interaction (FSI) due to the intricate Multiphysics involved. This paper presents the investigations on the flow behaviour and performance of a passive check valve based piezoelectric micropump using numerical analysis. The simulation study comprising FSI depicts the performance of a piezoelectric micropump using a fluid-structure coupling, fluid selection, structural modelling, and piezoelectric equations. The simulation results illustrate the micropump performance characteristics such as piezoelectric actuator displacement, micropump flow rate, backpressure, and Von Mises stress. Experiments are conducted to validate simulation results by studying the effect of voltage and frequency on the micropump flow and pressure characteristics. The experimental study demonstrated that the passive check valve based piezoelectric micropump delivers a maximum flow rate of 32 ml/min at zero backpressure. The micropump can pump the fluid against maximum backpressure up to 35 kPa.

Experimental study on performance evaluation of passive valved piezoelectric micropumps with series, parallel and hybrid series-parallel configuration

ABSTRACT To overcome the flow deficit in high pumping flow applications, a parametric study is presented involving three Multiple Micropump system (MMS) configurations: Series Multiple Micropump System (SMMS), Parallel Multiple Micropump System (PMMS) and hybrid Series-Parallel Multiple Micropump System (SPMMS). The performance of the MMS configurations was investigated using analytical and experimental approach. The MMS operating at ‘in-phase’ mode (0° phase difference) was observed to exhibit flow pulsations. Therefore, the MMS was operated at ‘out-of-phase’ mode (90° phase difference) to minimise the flow pulsations. The maximum flow rate at the ‘in-phase’ mode was observed to be 37.58 ml/min, 112.32 ml/min and 51.81 ml/min for SMMS, PMMS and SPMMS configurations respectively. Whereas the flow pulsation results indicate that the degree of flow pulsation for SMMS, PMMS and SPMMS configurations was decreased by 13.4%, 13.5% and 13.3% respectively when operated at ‘out-of-phase’ mode. The maximum back pressure of 140 kPa, 40 kPa and 100 kPa was recorded for SMMS, PMMS and SPMMS configurations respectively. It was found that the flow rate and backpressure vary significantly with the actuation frequency and series-parallel modes for MMS. The proposed series-parallel MMS configurations can be used in biomedical, thermal management and fuel cell applications.

Unsteady characteristics of the diffusion/nozzle tube for valveless piezoelectric micropumps at a lower frequency

In this study, transient flow performance of the diffusion/nozzle tube with diffusion angle of 10° under different Wo numbers was studied using ANSYS CFX software. The purpose of this work is to obtain the factors which influence the flow characteristics of the diffusion/nozzle tube for valveless piezoelectric micropumps under unsteady conditions. A time-dependent sinusoidal pressure is exerted for the entrance as the boundary condition, and the pressure amplitudes P0 are 50Pa, 100Pa, 500Pa, 1000Pa and 5000Pa. The simulation results show that the change of flow lags behind the variation of pressure under unsteady flow conditions. The greater the Wo numbers, the smaller the pressure amplitude P0 , and the greater the phase difference. Both the loss coefficient of pressure in the diffusion ξd , and the nozzle ξn increase with increasing Wo numbers, and decrease with increasing P0 . The vortex has a great influence on the flow characteristics of the valveless piezoelectric micropumps.

A compact jet array impingement cooling system driven by integrated piezoelectric micropump

Thermal management has become a bottleneck for high-power electronics due to high heat flux. Liquid cooling has been developed as an effective way to dissipate the heat of electronic devices. However, the existing liquid cooling systems are mostly too bulky to be applied in the miniaturized devices with very limited installation space. In this work, by integrating jet impingement cooling with piezoelectric micropump, we proposed a compact liquid cooling system that simultaneously enables high heat removal capability and tiny volume. The functions of jet array impingement cooling and coolant pumping are realized in a single component with an external dimension of 40 mm × 40 mm × 10 mm. The thermal performance of the system was investigated by experiments. The results show that the convective heat transfer coefficient achieves 20572 W·m−2·K−1 at a heat flux of 91.5 W/cm2. And the electric power consumption of the system is only 0.023 W under a heat load of 200 W (50 W/cm2). Simulations, which agree well with experiments, were further employed to study the transient heat transport process. This novel jet impingement cooling system driven by integrated piezoelectric micropump is compact and efficient, which provides a promising solution for the thermal management of high-power, miniaturized electronic devices.

A bi-directional valveless piezoelectric micropump based on the Coanda effect

A bi-directional valveless piezoelectric micropump based on the Coanda effect

Design and simulation of a piezoelectric micropump for drug delivery systems

Design and simulation of a piezoelectric micropump for drug delivery systems