Valveless Micropump Research Articles

Achieving Full Forward Flow of Valveless Piezoelectric Micropump Used for Micro Analysis System

The valveless piezoelectric micropump has the advantages of simple structure, high precision and low cost, which can realize the directional transport of micro-fluid and wildly be applied in a micro analysis system. However, backflow at the outlet cannot be avoided due to the limitation of its working mechanism. Large reflux rate can increase the volume control accuracy per cycle, but reduces the stability of the micro analysis system. In order to achieve a full forward flow, which reduce the influence of backflow on the system’s stability, the reflux characteristics of the designed valveless piezoelectric micropump were studied. The condition proposed, which should be satisfied for obtaining full forward flow, is that the reflux rate should be less than 50%. The influence of relations between the size of the key structures and pumping characteristics are established, and the references for structural parameter selection to reduce backflow and achieve full forward flow are given. This paper highlights the methods of controlling the pumping performance and achieving full forward flow, based on structural parameter selection analysis and adjusting excitation. The reflux rate can be reduced to 5% when the inlet angle is increased to 9°. The experimental results verify the validity of the obtained results and the proposed methods of control. This work provides important references for applying valveless piezoelectric micropumps in micro analysis and precision-driven systems.

Fabrication and flow rate characterization of a DRIE process based valveless piezoelectric micropump

Micropumps have become one of the major research topics in the field of microfluidics. Different actuators have been used in active micropumps including piezoelectric ones, which convert electrical energy to mechanical energy. In this study, a piezoelectric disc was designed as an actuator and was integrated into a fabricated piezoelectric micropump. Unlike wet etching methods, which is generally used to etch layers of relatively high thickness in the silicon wafer, dry etching was used in this study. Aluminum was used as a mask material during the fabrications-steps, and the fabrication process was shortened with the use of the masking steps. The etching process of the slot, in which the piezoelectric disc was placed, and etching of the inlet/outlet channels were performed simultaneously. Thus, the processing time was significantly shortened. The fabrication of this silicon-based valveless micropump was accomplished by using the DRIE (deep reaction-ion etching) technique, which provided controlled etching. Experiments were conducted on the fabricated micropump with the use of the bulk micromachining technology to deliver the desired pumping action. The leakage and the air entrapment between the consecutive micropump structural layers were satisfactorily eliminated. This micropump is capable of delivering a promising flow rate of 52 (µl min−1) for deionized water, which corresponds to a 150 [Hz] square wave type and a peak-to-peak voltage of 60 (V) Vp -p . No moving mechanical valves were included so that the risks of clogging, reduced performance, and reduced reliability due to wear and fatigue were minimized. Not only gases and liquids but also fluids containing particles could be used as the working fluid for this micropump. The piezoelectric micropump design was optimized to achieve a high time-averaged flow rate (>50 (µl min−1)) with a relatively low excitation voltage (<100 (V) Vp -p ) as opposed to the use of a high excitation voltage.

Fabrication and Testing of PDMS Micropump Actuated by Piezoelectric Polymer Composite

Appropriate technological solutions to healthcare can cause huge impact on medical processes and practices leading to sustainable future. Prevalence of diabetes and other chronic diseases has been steadily increasing for which self-attention and healthcare procedure is a logical solution. This paper proposes a piezoelectric polymer composite based micropump that is biocompatible and inexpensive. Lead Zirconate Titanate (PZT) powder is dispersed in polyvinyledene difluoride (PVDF) to form a novel PZT/PVDF composite material. The PZT/PVDF composite material is sonicated, cast, and cured to form a film which is used as the actuator. The polydimethylsiloxane (PDMS) based micropump is designed and fabricated using soft lithography technique. Once the master mold is prepared in clean room, other fabrication steps can be accomplished in a normal environment and multiple PDMS replicas can be prepared with ease. The proposed processing and fabrication steps are simple and inexpensive leading to substantial reduction in the device cost. The piezoelectric polymer based valveless micropump thus fabricated is subjected to performance testing. The micropump is found to deliver fluid in small quantities in a controlled manner and sufficient back pressure and flow rate can be achieved at low applied voltage and frequency.

Simulation and Experiments on a Valveless Micropump With Fluidic Diodes Based on Topology Optimization

Micropumps are microelectromechanical system (MEMS) devices that pump small quantities of liquids. They are used in many applications such as electronics cooling and drug delivery. Valveless fluid diode micropumps with no moving parts have recently attracted great interest in the MEMS community. In this paper, topology optimization is used to design two-dimensional, fixed-geometry, fluidic diodes of high diodicity, which is the ratio of pressure drops of forward to reverse flows. One of the fluidic diodes, of the Tesla type, shows a diodicity of over five. Another is of the nozzle-diffuser type. Both are experimentally and computationally demonstrated herein. Then the numerical simulation was applied to simplify the structures, and the two-dimensional geometry was converted into three-dimensional model for micropumps. Three-dimensional and unsteady numerical analyses of micropump fluid flow with optimized diodes were conducted for pumps of each of the two diode designs. The micropump with the Tesla-type fluidic diode reached a measured flow rate of 34 ml/h, consistent with the computed results and 2.2 times that of the nozzle-diffuser type micropump. The performance results show a high dependence on internal channel geometry. The two types show highest flow rates with an internal channel thickness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200 ~\mu \text{m}$ </tex-math></inline-formula> . Demonstrated good repeatability and precise flow control show positive prospects for application. [2021-0144]

Research on Valveless Piezoelectric Micropump Based on COMSOL and 3D Printing Technology

In order to make the output flow of the valveless micropump larger and obtain continuous pumping capacity, a valveless piezoelectric micropump with a combination of V-shaped structure inlet and Y-shaped structure outlet is designed, which saves the design and installation of microvalve and makes the structure relatively simple and easy to process. In this paper, first, the operating principle of the valveless piezoelectric micro pump is analyzed; secondly, COMSOL simulation software was used to perform modal analysis on the drive and the appropriate vibration mode was obtained. The displacement trend of the piezoelectric vibrator was simulated and tested at the frequency of 40 Hz and different voltages; finally, 3D printing technology was used to produce an experimental prototype of the micro-pump, and t the specific size of the micro pump is 20 mm×20 mm×6 mm. The test results show that, driven by AC voltage, the discharge liquid of the valveless piezoelectric micropump can reach 658.8μl/min.

Performance comparison of piezo actuated valveless micropump with central excitation and annular excitation for biomedical applications

In recent years, microfluidic devices, particularly micropumps, are extensively utilized in biomedical applications. The micropump used in biomedical applications needs to possess precise delivery of fluids at requires rate and pressure. The present work proposes a valveless mechanical micropump with a disposable chamber integrated with a novel concept of annular excitation of the diaphragm to fulfil the need for precise delivery of fluids in biomedical applications. The proposed design of the micropump involves a reusable configuration of the amplified piezoelectric actuator (APA) for micropump actuation and a disposable pump chamber. The pumping of the fluids occurs through the oscillation of the silicone rubber bossed diaphragm. The performance of a mechanical micropump depends on the oscillation amplitude of the diaphragm. Thus, the conventional approach of central excitation of the bossed diaphragm is replaced by a novel approach of annular excitation intended to enhance the deflection range, thus the volumetric performance of the micropump. An experimental comparative study is carried out to assess the deflection characteristics of central excitation and annular excitation of the bossed diaphragm. The maximum deflection measured with the annularly excited configuration of the bossed diaphragm is about 1953.4 ± 8.00 µm at 150 V, 43.5 Hz, which is superior to the maximum deflection of centrally excited configuration delivering 717.99 ± 4.00 µm at 150 V, 9.5 Hz. Further, the experimental studies aimed to fabricate and characterize the micropump with central and annular excitation approaches. The proposed micropump with central excitation delivered the maximum water flow rate of about 7.192 ± 0.147 ml min−1 and backpressure of 0.294 kPa at 150 V, 5 Hz. However, the enhancement of the deflection characteristics of the bossed diaphragm under annular excitation leads to performance enhancement of the micropump with the flow rate of 95.10 ± 0.444 ml min−1 and backpressure of 1.472 kPa at 150, 30 Hz

System modeling and characterization of enhanced valveless micropumps

This article provides a comprehensive analytical and numerical modeling procedure for characterizing the dynamics of flow fields in both the traditional circular and the new, efficiency- enhanced chambers of valveless micropump systems. The flow dynamics of the traditional circular valveless micropump system are analytically modeled and experimentally verified by comparing the results with data measured directly from a real-world system that has been discussed in the literature. The validated comprehensive modeling procedure is then extended to model the efficiency- enhanced micropump system in order to increase net flow rate and expanding the operational working range of the back pressure for possible micro devices aimed at applications for many high-performance industrial applications. A comparison of the associated system frequencies in both micropump systems shows, that the resonance frequency of the efficiency- enhanced micropump system is increased from 31 Hz to 38 Hz. The maximum net flow rate of the new system is also increased dramatically to a level of 1.74 ml/min, which is approximately 50% higher than that of the conventional setup. As long as the same input driving power is applied to both systems, the overall operating efficiency of the proposed micropump system is increased by approximately 58%. Meanwhile, the best- efficiency point (BEP) is stepped up from 0.56 ml/min to 1.1 ml/min. The enhancement of the BEP thus makes it possible for the back pressure to be operate more effectively in the range of 64 ∼ 100 Pa.

Research and verification of similar laws in valveless piezoelectric micropumps

Research and verification of similar laws in valveless piezoelectric micropumps

Valveless flow reversal by a pH responsive supramolecular micropump.

A valveless micropump was designed via dynamic supramolecular interaction between beta-cyclodextrin (β-CD) and benzimidazole (BzI). It shows flow reversal in response to the pH change. An L-shaped microchannel was used to demonstrate the flow reversibility over long distances.

A novel valve-less piezoelectric micropump generating recirculating flow

ABSTRACT Microfluidic devices or systems to generate recirculating flow are increasingly utilized in the fields of chemistry, biomedicine, biology, with bottlenecks in integration and miniaturization needed a breakthrough. Here, a concept for a highly integrated valve-less piezoelectric micropump generating recirculating flow (VPMGRF) is proposed, simultaneously realizing innovation in theory and method. Based on fluid inertiaand energy dissipation of vortexes, a novel double-loop tube was designed to achieve fluid flow in different directions along various paths, with the flow characteristics at different cross-sectional areas explored through computational fluid dynamics (CFD). Afterwards, as valve bodies, the double-loop tubes were connected with a piezoelectric-actuated chamber to constitute the VPMGRF, which was followed by establishing a theoretical model of the vibration, fluid dynamics, and net flow rate. Eventually, experimental results showed that VPMGRFs could generate internal recirculating flow and had a pump effect. The maximum net flow rate reached 5.19 mL/min at 8 Hz, corresponding to a vibrator amplitude of 35 μm and an output pressure amplitude of 4.27 kPa. Furthermore, the larger the characteristic length of the cross section, the greater the amplitude of the vibrators, the larger the amplitude of output pressure, and the slower the flow rate.

A new structure of Tesla coupled nozzle in synthetic jet micro-pump

Synthetic jet pump is a potential technique to improve the pumping performance by introducing a smart structure which can enhance counter-rotating vortexes. Aligning with this approach, a new structure of valveless micro-pump is developed in this work. The mechanism of the present micro-pump is based on the combination of the nozzle and a tesla element to rectify the synthetic jet. The new structure of “ace of spades” nozzle, named Tesla coupled nozzle, creates series of vortexes at the orifice of the pump chamber that allows to attenuate the reversed flows while fluid is drawn through the pump. The present micro-pump is simple but robust and can perform at rather low voltages.

Modeling and Simulation of a Micro pump and Its Performance. (Dept. M ( Power ) )

A transient 2D model of Valve-less micro-pump is constructed and used to study pump performance under different conditions through numerical simulation. Operating conditions, design parameters and fluid properties effect on the micro pump net flow rate have been investigated. The operating frequency was found to be a critical operating parameter. Therefore, the effect of other design and operating conditions on the resonance frequency (optimum operating frequency) has been studied. Also, general correlations for the micro pump dimensionless performance characteristics have been deduced with sufficient accuracy, within the studied range.

Performance analysis of valveless micropump with disposable chamber actuated through Amplified Piezo Actuator (APA) for biomedical application

The precise manipulation of fluid through pumping systems has been the technological challenge in microfluidic applications. The biomedical applications call for precise and accurate delivery of fluid through miniaturized pumping systems. This paper presents a novel valveless micropump for biomedical applications operated by the Amplified Piezo Actuator. Integrating the disposable chamber and reusable actuator with the proposed micropump allows the actuator to be reused and eliminates the possibility of infection or contagion. The micropump was fabricated using low-cost polymeric materials like Polymethylmethacrylate (PMMA), Silicone rubber through CNC milling, Laser Cutting, conventional moulding operation. The micropump chamber, nozzle/diffusers, and a bossed diaphragm constituted disposable part and Amplified Piezo Actuator with structural support formed the reusable part of the micropump. The bossed diaphragm of the pump chamber consists of a central cylindrical protrusion to reduce the force of adhesion on the diaphragm and transmit force required for micropump actuation. A theoretical analysis was performed to assess the effect of diaphragm thickness and the bossed region on the effective stiffness of the diaphragm, which in turn influences the deflection achieved. Besides, an analytical approach has been presented to address the effect of adhesive force on the diaphragm surface due to the residual fluid and chamber depth. The experimental characterization of the micropump was carried out to determine the optimal performance parameters with water, fluids mimicking blood plasma, and whole blood. Based on the experimental results, the pumping rate and head developed by the micropump have been significantly affected by factors such as bossed ratio, diaphragm thickness, depth of the micropump chamber, and viscosity of the fluid. The optimum configuration of the micropump cosidered silicone rubber diaphragm with thickness of 0.20 mm having a bossed ratio of 0.33 and a chamber depth of 1.25 mm. With the optimal operating parameters of 150 V sinusoidal input of frequency 5 Hz, the proposed micropump was capable of delivering 7.192 ml/min, 6.108 ml/min, and 5.013 ml/min of water and blood plasma, whole blood mimicking fluid with the maximum backpressure of 294.00 Pa, 226.243 Pa, and 204.048 Pa respectively. The corresponding resolution, i.e., pumping volume/stroke of the micropump was about 23.972 µl, 20.358 µl, and 16.708 µl, respectively.

A Minimized Valveless Electromagnetic Micropump for Microfluidic Actuation on Organ Chips

In recent years, organ chips have become an ideal alternative for physiological and pathological studies as well as drug screening. To more realistically simulate the in vivo physiological environment, micropumps are often needed as power sources to achieve dynamic culture in organ chips. In this study, we present a valveless electromagnetic micropump that can be used in organ chips. Fluid flow is actuated by the vibration of a PDMS membrane through a varying magnetic field. This micropump uses a nozzle/diffuser structure instead of valves, which simplifies the structure. By reducing the volume of the coil and magnet, the size of the electromagnetic micropump is minimized so that it can be integrated on a microfluidic chip. The micropump and the chip can be portably packaged by using a small signal generation module and a dry battery to supply the coil with a square wave, reducing the dependence on external devices. In addition, multiple electromagnetic micropumps can be integrated on a single chip. These micropumps can be connected in series or in parallel, which can achieve complicated flow conditions and can simulate physiological fluid flow more realistically in different types of organ chips. The flow rate was measured to characterize the actuating performance of the micropump. We established the dynamic coculture of a liver and breast cancer model on the chip, with medium actuated by the electromagnetic micropump. Cell viability, albumin and IL-6 were analyzed. The results indicated that dynamic coculture, which was actuated by the electromagnetic micropump, was beneficial for cell growth and function compared with the static control group.

Form follows function: estimation of CSF flow in the third ventricle-aqueduct-fourth ventricle complex modeled as a diffuser/nozzle pump.

In the last 20 years, researchers have debated cerebrospinal fluid (CSF) dynamics theories, commonly based on the classic bulk flow perspective. New hypotheses do not consider a possible hydraulic impact of the ventricular morphology. The present study investigates, by means of a mathematical model, the eventual role played by the geometric shape of the "third ventricle-aqueduct-fourth ventricle" complex in CSF circulation under the assumption that the complex behaves like a diffuser/nozzle (DN) pump. DN pumps are quite recent devices introduced as valveless micropumps in various industrial applications given their property of driving net flow when subjected to rhythmic pulsations. A novel peculiar DN pump configuration was adopted in this study to mimic the ventricular complex, with two reservoirs (the ventricles) and one tube provided with a conical reach (the aqueduct-proximal fourth ventricle). The flow was modeled according to the classic equations of laminar flow, and the external rhythmic pulsations forcing the system were reproduced as a pulsatile pressure gradient between the chambers. Several physiological scenarios were implemented with the integration of data acquired by MRI in 10 patients with no known pathology of CSF dynamics, and a quantitative analysis of the effect of geometric and hydraulic parameters (diverging angle, sizes, frequency of pulsations) on the CSF net flow was performed. The results showed a craniocaudal net flow in all the given values, consistent with the findings of cine MRI studies. Moreover, the net flow estimated for the analyzed cohort of patients ranged from 0.221 to 0.505 ml/min, remarkably close to the values found on phase contrast cine MRI in healthy subjects. Sensitivity analysis underlines the pivotal role of the DN configuration, as well as of the frequency of forcing pressure, which promotes a relevant net flow considering both the heart and respiration rate. This work suggests that the geometry of the third ventricle-aqueduct-fourth ventricle complex, which resembles a diverter, appears to be functional in the generation of a net craniocaudal flow and potentially has an impact on CSF dynamics. These conclusions can be drawn by observing the analogies between the shape of the ventricles and the geometry of DN pumps and by recognizing the basis of the mathematical model of the simplified third ventricle-aqueduct-fourth ventricle complex proposed.

Experimental analysis of a valve-less piezoelectric micropump with crescent-shaped structure

This study presents a high-performance valve-less piezoelectric micropump with crescent-shaped structure. This micropump was designed by finite element analysis (FEA) and fabricated through 3D printing technology. Different configurations of the micropump with different distances from inlet to the crescent-shaped structure (δ = 0.3, 0.6, 0.9, 1.2, and 1.5 mm) and numbers of crescent-shaped structures (from one up to four stages) were tested. The sound pressure level (SPL) characteristics were experimentally investigated and evaluated at 0.6, 1.5, 2.0, 2.5, and 3.0 mm. The results gave a maximum flow rate of 219.4 ml min−1 at 0.6 mm under 220 V and 45 Hz. Moreover, the flow rate for the quadruple crescent-shaped structure was 286 ml min−1 at 220 V and 82 Hz. Besides, the difference of the SPL was 3.2 dB at 0.6 m, making this pump better than others; the difference was kept at about 18 dB when the gap exceeded 2.0 mm. The results suggest that the structure with the best configuration is that with δ = 0.6 mm and four stages, and the SPL fluctuation is smaller as the output performance becomes better. The study offers some valuable insights into improving its performance and practical application.

Fully coupled modeling and design of a piezoelectric actuation based valveless micropump for drug delivery application

The precise control over the drug delivery involved in several vital applications including healthcare is required for achieving a therapeutic effect. For such precise control/manipulation of the drugs, micropumps are used. These micropumps are basically of two types viz. check valve-based and valveless micropumps. The valveless micropumps are preferable due to the congestion-free operation of diffuser/nozzle valves. In this paper, design optimization of a valveless piezo-electric actuation based micropump is carried out using COMSOL Multiphysics 5.0 by coupling two Multiphysics interface modules namely fluid–structure interaction and piezoelectric physics modules. Using simulation studies, the influence of pump design parameters including diffuser angle, diffuser length, neck width, chamber depth, chamber diameter and diaphragm thickness on net flow rate is studied. An optimal set of design parameters for the proposed micropump is identified. Further, the influence of actuation frequency on the flow rate is analysed. It is found that the proposed micropump is capable to deliver a net flow rate of 20 µl/min and a maximum back pressure attainable is 200 Pa.

Investigations on performance of valveless piezoelectric micropump with concave tuning diffuser/nozzle elements in transient flow

A diffuser/nozzle is one of the most frequently-used channels in a valveless piezoelectric micropump, but its efficiency has not been satisfactory. Hence, optimisation of the channel structure is of great significance. The concave tuning diffuser/nozzle element can obtain steady flow rectification under different Reynolds numbers, and its efficiency is much higher than the conventional diffuser/nozzle element whose diverging angle is >25°. Therefore, the application of concave tuning on the micropump is promising and worth anticipating. In this work, the experiment and numerical simulation were carried out under the conditions of voltage (50–250 vpp), excitation frequency (10–1000 Hz) and Rec (100–1000). The results show that the performance of a micropump with concave tuning is better than that with a straight sidewall, as the pump efficiency is improved significantly. The position and size of vortexes are of great significance to the pump efficiency of the micropumps. The distribution of pressure in the micropumps with concave tuning and straight sidewall was displayed. With the increase of characteristic Reynolds number, the adverse pressure gradient occurred. Compared with the straight sidewall, the concave tuning structure can better withstand adverse pressure gradient and delay the boundary layer separation in the channel.

Experimental investigation on performance of disposable micropump with retrofit piezo stack actuator for biomedical application

Extensive researches are being conducted to develop miniaturized pumping systems to fulfill the need for accurate delivery of fluids at required rates, particularly in the biomedical field. This paper presents the design, fabrication, and testing of novel valveless micropump actuated through an amplified piezo actuator. The proposed model of the micropump pump has the unique feature of a disposable chamber and employs low-cost polymeric materials, conventional molding and machining operations for fabrication. The disposable part of the pump consists of a laser-cut pump chamber with nozzle/diffuser made of Polymethyl methacrylate (PMMA) and conventionally molded silicone rubber diaphragm. The retrofit part includes the amplified piezo actuator and support structures build from PMMA. Systematic characterization of the pump was carried with water and blood mimicking fluid to understand the effect of operating parameters such as driving frequency and actuation voltage on flow rate and back pressure of the micropump. Experimental results show that the proposed design was capable of pumping 3.3–3.4 ml/min of dye solution and 1.7–1.75 ml/min of blood mimicking fluid at a driving frequency of 5 Hz and actuation voltage of 150 V. The corresponding computed volume resolution/stroke of the pump was found to about 5.75 µl and 11.25 µl of blood mimicking fluid and dye solution, respectively. The proposed pump was found to work effectively against a maximum back pressure of 156 Pa with blood mimicking fluid and 250 Pa with the dye solution as the working fluid under the same operating condition of 5 Hz and 150 V.

A Valveless Piezoelectric Micropump Based on Projection Micro Litho Stereo Exposure Technology

At present, the micropumps are usually adopted in microelectromechanical systems (MEMS) process, which is characterized by high technical complexity and expense, to obtain micro-scale internal channels. Moreover, the MEMS process is more suitable for the 2.5-dimensional channels. This paper presents a 3-dimensional vortex tube-based valveless piezoelectric micropump with low cost and high accuracy, and the projection micro litho stereo exposure (PμLSE) technology is applied to manufacture the prototype of the micropump. The working principle of the piezoelectric micropump is analyzed, and the flow resistance of the vortex diode is calculated numerically. Then, the performance and 3D morphology measurement of the micropump are conducted. The results demonstrate that the inner surface of the channel is uniform and the surface roughness is small. By comparing and analyzing the output performances between two prototypes manufactured by the PμLSE technology, the stability of the PμLSE technology is confirmed. This paper provides a fast and cheap method for manufacturing a 3D micropump, and the proposed approach can also be further adopted in fabricating such micro-stereoscopic structure devices.