Maximum Pump Pressure Research Articles

Chip-integrated non-mechanical microfluidic pump driven by electrowetting on dielectrics.

A microfluidic pump is presented that generates its pumping action via the EWOD (electrowetting-on-dielectric) effect. The flow is generated by the periodic movement of liquid-vapor interfaces in a large number (≈106) of microcavities resulting in a volume change of approx. 0.5 pl per cavity per pump stroke. The total flow resulting from all microcavities adds up to a few hundred nanolitres per cycle. Passive, topologically optimized, non-mechanical Tesla valves are used to rectify the flow. As a result, the micropump operates without any moving components. The dimensioning, fabrication, and characterization process of the micropump are described. Device fabrication is done using conventional manufacturing processes from microsystems technology, enabling cost-effective mass production on wafer-level without additional assembly steps like piezo chip-level bonding, etc. This allows for direct integration into wafer-based microfluidic or lab-on-a-chip applications. Furthermore, first measurement results obtained with prototypes of the micropump are presented. The voltage- and frequency-dependent pump performance is determined. The measurements show that a continuous flow rate larger than 0.2 ml min-1 can be achieved at a maximum pump pressure larger than 12 mbar.

Intra-abdominal Fluid Extravasation: Is Endoscopic Deep Gluteal Space Exploration a Risk Factor?

Background:The extravasation of fluid into the intra-abdominal space is recognized as a possible complication of hip arthroscopic surgery/endoscopy. The exposure of anatomic areas to elevated pump pressures and high volumes of irrigation fluid increases the risk of fluid leakage into anatomic spaces around the hip joint, especially to the abdomen and pelvis.Purpose:To estimate the incidence and risk factors related to intra-abdominal fluid extravasation (IAFE) after hip endoscopy or arthroscopic surgery.Study Design:Cohort study; Level of evidence, 2.Methods:A prospective study was carried out between June 2017 and June 2018. A total of 106 hip procedures (endoscopy or arthroscopic surgery) performed for extra- or intra-articular abnormalities were included. Before and after surgery, in the operating room, ultrasound was performed by a trained anesthesiologist to detect IAFE. The hepatorenal (Morison pouch), splenorenal, retroaortic, suprapubic (longitudinal and transverse), and pleural spaces were examined. Patients were monitored for 3 hours after surgery to assess for abdominal pain. The data collected included maximum pump pressure, duration and volume of irrigation fluid (Ringer lactate), total surgical time, and traction time.Results:The incidence of IAFE was 31.1% (33/106; 95% CI, 23.1%-40.5%). The frequency of IAFE was 52.9% (9/17) in cases with isolated extra-articular abnormalities and 15.9% (7/44) in cases with isolated femoroacetabular impingement; in cases with both extra- and intra-articular abnormalities, the frequency was 37.8% (17/45). An intervention in the subgluteal space was identified as a risk factor for IAFE (odds ratio, 3.62 [95% CI, 1.47-8.85]). There was no statistically significant difference between groups (with vs without IAFE) regarding total surgical time, maximum pump pressure, or fluid volume. Postoperative abdominal pain was found in 36.4% (n = 12) of cases with IAFE compared with 2.7% (n = 2) of cases without extravasation (P < .001). No patient with IAFE developed abdominal compartment syndrome.Conclusion:IAFE was a frequent finding after hip arthroscopic surgery/endoscopy in patients with extra-articular abnormalities. Exploration of the subgluteal space may increase the risk of IAFE. Pain and abdominal distension during the immediate postoperative period were early warning signs for IAFE. These results reinforce the need for careful intraoperative and postoperative monitoring by the surgeon and anesthesiologist to identify and avoid complications related to IAFE.

Erosion of dune sands stabilised by grouting with lime–silica fume mix

Dune sands are often an environmental hazard during strong winds and sand storms, particularly in the summer months. Wherever a granular soil surface is left unprotected, it can be subjected to wind erosion and dune formation. In this study, an attempt was made to stabilise sand dunes by grouting with a slurry of lime–silica fume (L–SF) material. Dune sand samples were collected from northern Iraq. In situ field density of the soil was determined by sand-cone tests for moisture content, classification, compaction, relative density, direct shear and chemical tests. Erosion tests were conducted using centrifugal fans, with wind applied to the soil at a speed of 90 km/h for 11 min. Silica fume (SF) and a L–SF mix were used for stabilisation and their effects on the dune sands were investigated. For grouting, a 1000 ml grout pump was used to stabilise a liquid tank of the L–SF mix; the maximum pumping pressure was about 25 kPa. It was found that when the dune sand was with a slurry of L–SF, there was a reduction in erosion by about 70% for a stabiliser grout of 33% (Lime to SF ratio, 3L : 4SF) with 67% water of the total mixture weight. The stabilisation effect increased with increases in the number and depth of grouting holes around the stabilised area. When wind was applied at a rate of about 90 km/h for 11 min, the eroded natural sand dune surface was about 66 mm, while for soil stabilised by grouting with L–SF, the erosion was 17–36 mm. An increase in the number of injection points and a reduction in the distances between them reduced the amount of soil erosion.

Lessons Learned from Stimulation of Dibei Tight Gas Reservoir with Strong Heterogeneity in Tarim Basin

The Dibei gas field is a naturally fractured tight sandstone gas reservoir in the Tarim Basin, West China. It is characterized by large depth (4600–5200 m), huge thickness (100–200 m), low abundance, low matrix permeability, high pressure (80–95 MPa), high temperature (140 – 150°C) and strong heterogeneity. Different stimulation techniques were applied to improve well production. For the wells with good development of natural fractures, matrix acidizing, acid fracturing or conventional hydraulic fracturing is used. For the wells with low fracture density and huge thickness, separate-layer acid-fracturing, massive separate-layer hybrid fracturing or composite diverting agent is applied to improve stimulation efficiency. The low-damage high-temperature weighted fracturing fluids are used to reduce the effect of reservoir sensitivity and the treatment pressure, and high-strength proppant is used at the same time to keep high fracture conductivity. Meanwhile, large-diameter fracturing string with 3-1/2″ and 4-1/2″ connections is used to decrease pump pressure and increase pump rate. The above technologies were applied in more than twenty treatments in seven wells, of which more than half witnessed production increase. The matrix acidizing or conventional hydraulic fracturing is well performed for the wells with natural fractures, but inefficient for the extremely tight gas wells. In Well A without fractures, the massive separate-layer hybrid fracturing was used. In the treatment, a total of 1,328 m3 fracturing fluid was used, with 50 m3 proppant; the pump rate was 8 m3/min and the maximum pump pressure was 92 MPa. Unfortunately, the post-frac production was not as expected, mainly due to the damage of killing well. In Well B with fractures, high gas production was achieved by acid fracturing, but the gas rate dropped from 258,000 m3 to 51,000 m3 after killing well, and the gas rate never recovered even by acid fracturing, hydraulic fracturing and relieving damage with methanol. The development of natural fractures is the key controlling factor for gas production. Well C, less than 800 m from well B, The development of natural fractures is quite different from Well B, and 98,000 m3 gas rate was acquired after hydraulic fracturing with more than 1,000 m3 low damage high-temperature weighted fracturing fluid and 30 m3 proppant. The development of natural fractures is the key controlling factor for gas production and killing well damage is the fatal blow to the gas production, so the stimulation techniques and working fluid system should be prudently optimized.

Modeling and simulation of a wirelessly-powered thermopneumatic micropump for drug delivery applications

This paper presents modeling and finite element analysis of a thermopneumatic micropump with a novel design that does not affect the temperature of the working fluid. The micropump is operated by activating a passive wireless heater using wireless power transfer when the magnetic field is tuned to match the resonant frequency of the heater. The heater is responsible for heating an air-heating chamber that is connected to a loading reservoir through a microdiffuser element. The solution inside the reservoir is pumped through a microchannel that ends with an outlet hole. The thermal and pumping performances of the micropump are analyzed using finite element method over a low range of Reynold’s number ⩽ 10 that is suitable for various biomedical applications. The results demonstrate promising performance with a maximum flow rate of ∼ 2.86 μL/min at a chamber temperature of 42.5 ºC, and a maximum pumping pressure of 406.5 Pa. The results show that the developed device can be potentially implemented in various biomedical areas, such as implantable drug delivery applications.

Modeling and simulation of a wirelessly-powered thermopneumatic micropump for drug delivery applications

This paper presents modeling and finite element analysis of a thermopneumatic micropump with a novel design that does not affect the temperature of the working fluid. The micropump is operated by activating a passive wireless heater using wireless power transfer when the magnetic field is tuned to match the resonant frequency of the heater. The heater is responsible for heating an air-heating chamber that is connected to a loading reservoir through a microdiffuser element. The solution inside the reservoir is pumped through a microchannel that ends with an outlet hole. The thermal and pumping performances of the micropump are analyzed using finite element method over a low range of Reynold’s number ⩽ 10 that is suitable for various biomedical applications. The results demonstrate promising performance with a maximum flow rate of ∼ 2.86 μL/min at a chamber temperature of 42.5 ºC, and a maximum pumping pressure of 406.5 Pa. The results show that the developed device can be potentially implemented in various biomedical areas, such as implantable drug delivery applications.

Constitutively Enhanced Lymphatic Pumping in the Upper Limbs of Women Who Later Develop Breast Cancer-Related Lymphedema.

It has previously been shown that the lymph drainage rate in both upper limbs is greater in women destined to develop breast cancer-related lymphedema (BCRL) than in those who do not develop BCRL, indicating a constitutive predisposition. We explored constitutive differences further by measuring the maximum lymphatic pump pressure (Ppump) and the rate of (99m)Tc-Nanocoll transport generated by the contractile upper limb lymphatics before and after breast cancer surgery in a group of women who were followed for 2 years to determine their eventual BCRL or non-BCRL status. Ppump and tracer transport rate were measured by lymphatic congestion lymphoscintigraphy in the ipsilateral upper limb in 26 women pre- and post-breast cancer surgery. BCRL occurred in 10/26 (38.5%) cases. Ppump in the women who later developed BCRL (40.0 ± 8.2 mmHg) was 1.7-fold higher than in those who did not develop BCRL (23.1 ± 10.8 mmHg, p = 0.001). Moreover, the rate of lymph tracer transport into the forearm was 2.2-fold greater in the women who later developed BCRL (p = 0.052). Surgery did not significantly reduce Ppump measured 21 weeks postsurgery, but impaired forearm tracer transport in pre-BCRL women by 58% (p = 0.047), although not in those who did not develop BCRL. Women destined to develop BCRL have higher pumping pressures and lymph transport, indicating harder-working lymphatics before cancer treatment. Axillary lymphatic damage from surgery appears to compromise lymph drainage in those women constitutively predisposed to higher lymphatic pressures and lymph transport.

초고층 압송계측을 통한 고성능 콘크리트의 유동특성과 압송성능과의 상관관계

본 연구에서는 초고층 구조물 시공에 사용되는 80MPa의 고성능 콘크리트를 대상으로 높이가 200m부터 350m인 지점까지 압송계측 결과를 근거로 하여 압송성능과 고성능 콘크리트의 유동특성과의 상관관계를 분석하였다. 굳지 않은 콘크리트의 물성과 초기강도 및 기준 재령에서의 압축강도 및 탄성계수는 모두 품질기준을 만족함이 확인되었다. 또한, 높이별 최대 압송압력은 약 10~15%씩 증가하였으며, 시간당 토출량은 최소 <TEX>$25m^3$</TEX>를 만족하는 것으로 나타났다. 또한, 압송압력과 마찰계수는 슬럼프 플로우의 크기에 반비례하는 것으로 나타났으며, 압송압력과 마찰계수는 T-500이 높을수록 증가하는 경향을 보였다. In this study, the evaluation and the analysis of the correlation between rheological properties and pumpability of high performance concrete, C80A which was applied to the height of from 200 m to 350 m in a super tall building, was carried out by measuring pumping pressure and flow rate, testing concrete properties at before and after pumping. As the results, C80A had satisfactory properties of fresh and hardened concrete to the requirements even after pumping and the maximum pumping pressure showed increase of 10~15% at every 50m higher pumping and the average flow rate showed the above <TEX>$25m^3$</TEX> per hour which means proper productivity. Additionally it was verified that pumping pressure and friction factor in pipeline are inversely proportional to slump flow and showed a tendency to increase according to the higher T-500 value.

Working fluid selection for a two-phase thermofluidic oscillator: Effect of thermodynamic properties

The Non-Inertive-Feedback Thermofluidic Engine (NIFTE) is a device capable of utilising low-grade heat to produce pumping work. An investigation on the applicability of different working fluids for the NIFTE is presented, with emphasis on the effects of key thermodynamic properties of the working fluid on: (i) the maximum thermal efficiency of an idealised two-phase positive-displacement cycle, and (ii) a prediction of the exergy efficiency of the NIFTE. The properties with the most dominant role in determining these efficiency measures were the change in specific volume due to vapourisation and the maximum saturation pressure in the cycle (linked to the pumping head during operation). Thirty-one pure working fluids were studied using a model of the NIFTE that features a dynamic heat exchanger description and a mechanism to account for thermal losses, presented in earlier work. For the scenario where the maximum cycle pressure was defined by the pumping application, higher efficiencies were predicted for wet and isentropic fluids. For the scenario where the hot and cold heat exchanger temperatures were set by the external heat source and sink, higher efficiencies were predicted for dry and isentropic fluids. The maximum pumping pressure and heat source temperature had non-monotonic effects on the efficiencies exhibited by different working fluids, which were linked to the role of molecular weight and polarity in determining the saturated vapour pressure during evaporation. For a particular NIFTE arrangement, setting and application, an optimum efficiency (and also pumping power output) was attained by selecting a working fluid with a particular maximum cycle (saturation) pressure; in the cases investigated here: 6% at 3.5bar. Upper bound thermal efficiencies of 14–15% were predicted for the ‘best’ working fluid undergoing an ideal generalised two-phase positive-displacement cycle, whereas valve and thermal losses in the NIFTE allowed values no higher than 1–2%.

Numerical simulation of a thermal-bubble actuated diffuser-nozzle valveless pump

A valveless micropump actuated by thermal bubbles which are generated by an electrode heater mounted with a pair of diffuser nozzles has been numerically studied by commercial CFD software FLUENT. The relationships between the net flow rate and the superheating and heat supplying frequency have been investigated. The depth of the diffuser-nozzle micropump is 200 μm, the diameter of the actuating chamber is 1 mm, and a pair of diffuser nozzles whose gap has been expanded from 30 μm to 274 μm with an open angle of 7° are connected to the actuating chamber. The working fluid is methanol. In the numerical simulation, the flow pattern is laminar. The results show that the pump has different optimal driving frequencies at different superheating. A cycle resulting from bubble growth and shrinking costs more time at higher superheating temperature; different superheating has different optimal driving frequency; when the superheating increases, the maximum volume flow rate and the maximum pump pressure will increase simultaneously, and the optimal driving frequency decreases as well, the maximum volume flow rate and pump pressure also have the same tendency; in the condition of uncontrolled condensing, the bubble shrinking process is longer than the growth process, thus it is the determining factor to affect the pump performance. The maximum volume flow rate is 9.02 μL/min at ΔT = 15°C, and the maximum pump pressure is 680 Pa. With the increase of wall superheat, cycle including the bubble growth and condensation will become longer, resulting in a significant impact on the pumping flow; different wall superheat has different optimized frequency, increasing superheat will bring increased pumping flow and pump pressure, the optimized driving frequency will be reduced; liquid supply phase is longer than pumping phase.

Numerical Investigation of a Periodic Heating Thermal-Bubble Actuated Diffuser–Nozzle Valveless Pump

A valveless micropump actuated by thermal bubbles which generated by an electrode heater mounted with a pair of diffuser nozzles has been numerically studied by commercial CFD software FLUENT. The relationship between the net flow rate and the superheating and heat supplying frequency has been investigated. The depth of the diffuser–nozzle micropump used in current numerical simulation model is 200 μm, and the diameter of micropump chamber is 1 mm. The pair of diffuser–nozzles are with gaps expanding from 30 to 274 μm and open angles of 7°. The working fluid is methanol in present study. The results show that the pump has different optimal driving frequency with different superheating. The cycle composed of bubble growth and shrinking costs more time at higher superheating. The maximum volume flow rate and the maximum pump pressure will increase with increasing superheating, simultaneously; and the optimal pulse duty, the maximum volume flow rate and pump pressure decrease with increasing superheating. The maximum volume flow rate and the maximum pump pressure are 29.6 μL/min and 680 Pa at ΔT = 15°C, respectively.

A self-priming, high performance, check valve diaphragm micropump made from SOI wafers

In this paper, we describe a self-priming high performance piezoelectrically actuated check valve diaphragm micropump. The micropump was fabricated from three wafers: two silicon-on-insulator (SOI) wafers and one silicon wafer. A process named ‘SOI/SOI wafer bonding and etching back followed by a second wafer bonding’ was developed in order to make the core components of this device which included an inlet check valve, an outlet check valve, a diaphragm and a chamber. The movable structures of this device, i.e. the check valves and the diaphragm, were fabricated from the device layers of the two bonded SOI wafers. Taking advantages of SOI wafer technology and etch-stop layers, the vertical parameters of the movable structures were precisely controlled in fabrication. The micropump was self-priming without any pre-filling process. The pumping rate of the micropump was linearly adjustable from 0 to 650l µm min−1 by adjusting frequency. The maximum pumping rate was 860 µl min−1 and the maximum pumping pressure was approximately 10.5 psi. The power consumption of the device was less than 1.2 mW.

Effective High-Density Wellbore Cleaning Fluids: Brine-Based and Solids-Free

Summary Displacing drilling mud with clear solids-free completion brine is a critical step during well completion. As we move into deeper waters and drill to deeper depths (greater than 25,000 feet MD), conventional methods and cleaning fluids become a limiting factor in this phase of the operation. Conventional cleaning fluids use fresh water or seawater treated with surfactants to remove wellbore solids and water-wet tubulars. Using low-density cleaning fluids creates a negative differential pressure between the working kill weight fluid and the formation, casing, and cement liners. In many situations, the negative differential pressure cannot be tolerated, and the risk of failure at the liner top, etc., is increased—especially, if the wellbore has not been pressure-integrity tested. Additionally, with increasing rig/spread costs, high pump rates are necessary to decrease the time it takes to perform these operations. The pump rate is indirectly proportional to the pump pressures required. Weighted spacers decrease the overall pressure differential, which allows for higher pumping rates. To overcome the density limitation of these cleaning fluids, conventional techniques, such as additional hydraulic horsepower, backpressure schedules, the addition of solids to lighter cleaning fluids (e.g., water, seawater), or balancing the weight of the low-density cleaning fluid with a matching higher-density fluid is used. However, each of these "fixes" has inherent limitations and is accompanied with reduced cleanup efficiency. Furthermore, conventional surfactants are not active or effective in high-density brines. New brine-compatible surfactant chemistry and the corresponding balanced-displacement engineering design were developed to overcome limitation of conventional displacement technology. This paper describes the field applications of new brine-based, high-density, solids-free cleaning fluids in balanced-displacements in deepwater and offshore shelf wells. The new high-density fluids were based on new surfactant technology developed to ensure effective wellbore cleaning, wellbore design parameters, and displacement modeling. In addition, weighted spacers aid in reducing high pump pressures and wellbore pressure differentials. In one case history, a maximum pumping pressure of more than 9,000 psi was expected for conventional water-based displacement but was reduced to a little more than 3,000 psi with the new design. High-density cleaning fluids, with densities up to and greater than 17.5 ppg, have been formulated and used successfully without compromising cleanup efficiency and significantly reducing differential pressures. Results from laboratory development and field applications are presented.

A design of a miniature ultrasonic pump using a bending disk transducer

If a pipe end is faced at a piston-vibrating surface with a small gap in liquid, the liquid is suctioned into the pipe. The present ultrasonic pump is based on this phenomenon to induce flow. For a low-profile configuration, we introduce a 30-mm-diameter bending disk driven by a ring-shaped PZT element bonded on the back of the disk. The disk vibrator is softly supported by frames via O-rings at its circumference, and is worked at the fundamental resonance frequency of 19 kHz of the bending mode. A pipe is installed perpendicularly to the center of the disk vibrator with a small gap. To improve the pump performance, we seek for the optimum vibration distribution of the disk vibrator. When the thickness around the disk center becomes large, the shape of the vibration distribution near the center approaches to a piston vibrator. If the flatness of the vibration distribution is defined as the vibration amplitude just under the pipe edge divided by the vibration amplitude at the disk center, it is 92.0% for the original bending disk. The flatness of the new design became 98.1% as a result of the optimization of the thickness profile of the disk. The pump pressure became high as the flatness became large when the gap size was small enough. The maximum pump pressure of 20.6 kPa was achieved when the vibration velocity at the disk center was 1.0 m/s and the gap size was 10 μm, while the maximum flow rate of 22.5 ml/min. was obtained with the input electrical power of 3.8 W.

Analysis of electrokinetic pumping efficiency in capillary tubes

A mathematical model for predicting the maximum pumping efficiency and pressure difference generation by an electrokinetic-driven fluid pumping system through a capillary tube is presented in this study. Both the maximum pumping efficiency and optimum pressure difference generation are found to depend on a single variable. This single variable is termed as the figure of merit since it determines the performance of electrokinetic pumping. The figure of merit is found to depend on three dimensionless parameters, the normalized Debye length, zeta potential, and Levine number indicating the nominal ratio of convective current to conductive current. All three parameters can be related to the pH value and concentration of aqueous salt solution by the introduction of concentration-dependent electrical conductivity and pH-dependent zeta potential. By presenting the maximum pumping efficiency and optimum pressure difference generation as functions of pH value, salt concentration, and capillary tube radius, it is found that both maximum pumping efficiency and optimum pressure difference generation increase with the decrease in capillary radius and salt concentration. The optimum pH values at which the maximum pumping efficiency and optimum pressure difference generation occur are found to be in the range between 6 and 9. For the salt concentration of 10(-6) M, pH 6.9, and a capillary tube radius value of 0.5 micro m, the predicted maximum pumping efficiency is 5.4% which is close to the experimental measurement reported in the literature.

Modeling and performance evaluation of an ultrasonic pump

This paper describes a low‐profile miniature ultrasonic pump consisting of a disk‐bending vibrator and a pipe‐end located vertically to the disk center via a small gap. First, we explored the relationships between the pump performance and the geometrical conditions of the pump experimentally: the pipe diameter, the gap, and vibration distributions. Based on those results, the thickness distribution of the bending disk was designed using finite‐element simulations so that the vibration distribution near the pipe might become uniform. Maximum pump pressure of 20.6 kPa was obtained with a 30‐mm‐diam bending disk and electrical power consumption of 3.8 W. For optimization, we constructed a model of the pump operation in this study. Nonlinearity in the elastic constant of the working fluid was introduced into the model because the temporal change rate of the gap caused by the ultrasonic vibration of the disk vibrator considerably affects the pump’s pressure generation. Results show that the calculated pump pressure well simulates the measured dependence of the gap on the pressure. The acoustic pressure was measured using a fiber optic pressure probe and was compared to the calculated pressure value.

Electrokinetic pumping effects of charged porous media in microchannels using the lattice Poisson–Boltzmann method

The electrokinetic pumping characteristics of nanoscale charged porous media packed in microchannels are investigated using a mesoscopic evolution method. When the pore size of porous media is comparable to the thickness of electric double layer, the effects of particle surface potentials on the bulk electric potential distribution will not be negligible. The lattice Poisson–Boltzmann method provides an accurate numerical solution for such problems, which combines two sets of lattice evolution methods solving the nonlinear Poisson–Boltzmann equation for electric potential distribution and the Navier–Stokes equations for fluid flow, respectively. The effects of the finite particle size, the bulk ionic concentration, the external electric field strength and the surface potentials on the electroosmotic micropump performances are therefore studied. The results show that for a certain porosity the maximum pumping pressure is inversely proportional to the particle diameter and the flow rate under zero pressure drop increases with the particle size. The pumping flow rate decreases with the backpressure yet increases with the external electric field strength, linearly respectively. The averaged flow rate increases with the bulk ionic concentration and the particle surface potential, but is slightly influenced by the surface potentials of channel walls. The numerical results agree with the published experimental data while some results deviate from the predictions based on the macroscopic linear assumptions.

A miniature ultransonic pump using a bending disk transducer and a gap

It is known that if a pipe end is faced at a vibrating surface in liquid with a small gap, liquid is suctioned into the pipe. As a miniature configuration, we introduce a bending disk transducer 30 mm in diameter using a ring-shaped PZT element. The disk vibrator is worked at the fundamental resonance frequency of 19 kHz of the bending mode. To optimize the pipe geometry, we experimentally investigated the effect of the outer diameter on the pump performance. As a result, the outer/inner diameter ratio of 3:2 is optimum for the gap smaller than 20 μm. We achieved the maximum pump pressure of 14.8 kPa and the maximum flow rate of 10 ml/min. using the prototype pump.

Micropump based on PZT unimorph and one-way parylene valves

This paper describes a micropump composed of a piezoelectric PZT unimorph and one-way parylene valves. Two different designs of the valves (cantilever- and bridge-type) are studied, fabricated and tested. The micropump (13 × 13 × 1.2 mm3 in size) is capable of pumping liquid up to 700 μL min−1 with its pumping speed being insensitive to a backpressure up to 2.5 kPa. The flow rate of 700 μL min−1 is obtained when the micropump is driven with square pulses at 6 kHz with 50% duty cycle and 100 V peak-to-peak. The maximum static pumping pressure is measured to be 4 kPa.

A surface-tension driven micropump for low-voltage and low-power operations

In this paper, we first report a micropump actuated by surface tension based on continuous electrowetting (CEW). We have used the surface-tension-induced motion of a mercury drop in a microchannel filled with an electrolyte as actuation energy for the micropump. This allows low voltage operation as well as low-power consumption. The micropump is composed of a stack of three wafers bonded together. The microchannel is formed on a glass wafer using SU-8 and is filled with electrolyte where the mercury drop is inserted. The movement of the mercury pushes or drags the electrolyte, resulting in the deflection of a membrane that is formed on the second silicon wafer. Another silicon wafer, which has passive check valves and holes, is stacked on the membrane wafer, forming inlet and outlet chambers. Finally, these two chambers are connected through a silicone tube forming the complete micropump. The performance of the fabricated micropump has been tested for various operation voltages and frequencies. We have demonstrated actual liquid pumping up to 70 /spl mu/l/min with a driving voltage of 2.3 V and a power consumption of 170 /spl mu/W. The maximum pump pressure is about 800 Pa at the applied voltage of 2.3 V with an operation frequency of 25 Hz.