Applied Air Pressure Research Articles

Layer-by-Layer-Assembled Laccase Enzyme on Stimuli-Responsive Membranes for Chloro-Organics Degradation.

Functionalized membranes provide versatile platforms for the incorporation of biocatalysts and nanostructured materials for efficient and benign environmental remediation. The existing techniques for remediating chloro-organics in water consist of both physical and chemical means mostly using metal oxide-based catalysts, despite associated environmental concerns. To offer bioinspired remediation as an alternative, we herein demonstrate a layer-by-layer approach to immobilize laccase enzyme onto pH-responsive functionalized membranes for the degradation of chloro-organics in water. The efficacy of these bioinspired membranes toward dechlorination of 2,4,6-trichlorophenol (TCP) is demonstrated under a pressure-driven continuous flow mode (convective flow) for the first time to the best of our knowledge. Over 80% of the initial TCP was degraded at an optimum flow rate under an applied air pressure of about 0.7 bar or lower. This corresponds to degradation of a substantial amount of the initial substrate in only 36 s residence time, whereas it takes hours for degradation in a batch reaction. This, in fact, demonstrates an energy efficient flow-through system with potentially large-scale applications. Comparison of the stability of the enzyme in the solution phase versus immobilized on the membrane phase showed a loss of some 65% of enzyme activity in the solution phase after 22 d, whereas the membrane-bound enzyme lost only a negligible percentage of the activity in a comparable time span. Finally, the membrane was exposed to rigorous cycles of TCP degradation trials to study its reusability. The primary results reveal a loss of only 14% of the initial activity after 4 cycles of use in a period of 25 d, demonstrating its potential to be reused. Regeneration of the functionalized membrane was also validated by dislodging the immobilized enzyme, followed by immobilization of fresh enzyme onto the membrane.

On-demand frequency tunability of fluidic antenna implemented with gallium-based liquid metal alloy

We investigated frequency tunability of a microfluidic-based antenna using on-demand manipulation of a gallium-based liquid metal alloy. The fluidic antenna was fabricated by polydimethylsiloxane (PDMS) and filled with the gallium-based liquid metal alloy (Galinstan ® ). It is composed of a digital number “7”-shaped feedline, and a square-shaped and a digital number “6”-shaped patterns, which are all implemented with the liquid metal. The gallium-based liquid metal was adhered to the channel surface due to its viscous oxide layer originating from the gallium oxide forming when it exposed to the air environment. We treated the liquid metal with hydrochloric acid solution to remove the oxide layer on the surface resulting in easy movement of the liquid metal in the channel, as the liquid metal surface has been transformed to be non-wettable. We controlled the physical length of the liquid metal slug filled in feedline with an applied air pressure, resulting in tuning the resonant frequency ranging from 2.2 GHz to 9.3 GHz. The fluidic antenna properties using the liquid metal’s electrical conductivity and mobility were characterized by measuring the return loss (S11), and also simulated with CST Microwave Studio.

Experimental characterization of the pore size distribution in fibrous reinforcements of composite materials

This study uses capillary flow porometry to investigate the porous structure of engineering fabrics used in high-performance polymer composites. This technique consists of applying air pressure to a previously wetted sample to progressively expel the liquid from the pores. A porometry testing device commonly employed to characterize filtration media was used as the principal tool for this investigation. Four types of fibrous fabrics made of glass and carbon fibers with different textile architectures have been experimentally characterized with a through-thickness setup. This allowed obtaining the pore size distribution inside the tested material. In all the cases studied, the porometry technique was able to detect in a reproducible way a bimodal pore size distribution reflecting the presence of both micropores (inside the fiber yarns) and mesopores (between the yarns). Moreover, experimental results indicate that the method can be used to study the influence of the textile pattern on the pore size distribution. Overall, the study shows that capillary flow porometry can give valuable information on the dual scale structure of fibrous reinforcements, which plays a critical role during the impregnation stage of Liquid Composite Molding processes. Because of its simplicity and speed of execution, the proposed approach appears to be a promising way to complement other sophisticated techniques already used for composites such as microscopy and X-ray microtomography.

Abrasive jet machining of glass: Experimental investigation with artificial neural network modelling and genetic algorithm optimisation

AbstractThe paper presents an experimental-based study of abrasive jet machining (AJM) considering the effect of changing process parameters. A series of drilling tests were carried out on glass workpieces using sand as the abrasive powder. The influence of each process parameter; applied air pressure, standoff distance, nozzle diameter, particle grain size and impact angle on the machining performance was determined in terms of the resultant material removal rate (MRR). The experimental results revealed that MRR was highly dependent on the kinetic energy of the abrasive particles, with the applied pressure the dominant parameter. The experimental results were compared with an erosion rate model previously published by Jafar et al. Though correct trends were predicted, there was a large discrepancy between model and measured values. An artificial neural network (ANN) was utilised to model the MRR more precisely, particularly to establish relationships between applied machining parameters and experimentall...

ENHANCEMENT OF HEAT TRANSFERRED RATE THROUGH HEAT EXCHANGERS DURING CONCENTRATION PROCESS OF MILK

Fouling problems of heat exchangers affect severely the performance of heat transfer process during the concentration of milk. In this investigation the strategy of anti-fouling is focused on investigate the optimal hydrodynamic flow. Two combined techniques, for resulting oscillating high values of shear stress on heat transfer surfaces, were applied in the current investigation. The two techniques are dissolved air flotation for microbubbles generation in the milk stream with pulsed flow for hydrodynamics conditions modifications. Four different applied air pressures of 0.1, 0.2, 0.3, and 0.6MPa for controlling the microbubbles discharge and three modes of pulsation were nominated as uniform pulsation, gradient pulsation and without pulsation. Plate heat exchanger used commonly in milk industry for thermal treatments. Commercial pilot scale of plate heat exchanger was operated at milk flow rate of 0.078 m3h-1 and heating level from 42 to 61°C. The results show that the application of air pressure for microbubbles generation and pulsation type have a significant effect on fouling layer prevention for more while 105 minutes (the experimented time). For these reasons, the use of the two integrated techniques can progress thermal process of the plate heat exchanger. The optimum treatment for fouling deterrence is at applied air pressure of 0.6MPa and gradient pulsation, frequency with 0.16Hz and two states of steadily, unsteady of 20 seconds and steady of 10 seconds, the fouling layer decreases by 76.5%, and the maximum value of the overall heat transfer coefficient obtained is 9688.4Wm-2K-1.

공압인공근육을 가진 내부형 연속체로봇의 기구식

This study presents the kinematics of an intrinsic continuum robot actuated by pneumatic artificial muscles. The single section of a developed continuum robot consisted of three muscles in parallel. The contraction of each muscle according to applied air pressure produced spatial motions of a distal plate with respect to a base plate. Based on the bending behaviors of artificial muscles, the orientation and position of the end-effector of a continuum robot were formulated using a transformation matrix. The orientation and position was also determined for a single section of the distal plate. A Jacobian matrix relating the contraction rate or the pressure rate of the muscles to the velocity vector of the end-effector was calculated considering the assembled position of actuators between neighboring sections of the robot. Experimental results showed that the motions of the intrinsic continuum robot were accurately estimated by the proposed kinematics.

Engineered biological structures by 3D printing of dual hydrogel inks

Event Abstract Back to Event Engineered biological structures by 3D printing of dual hydrogel inks Hagit Gilon1*, Yinfeng He1, Felicity Rose2, Jing Yang2 and Ricky D. Wildman1 1 University of Nottingham, Additive Manufacturing & 3D Printing, United Kingdom 2 University of Nottingham, Centre for Biomolecular Sciences, United Kingdom Introduction: Tissue engineering aims to replicate the architecture and function of human tissue for both treatment of disease and toxicity evaluation. One promising method of achieving this is 3D bioprinting, which aims to selectively print or deposit the constituent parts of structure in such as way to reproduce the main functions. 3D bioprinting has been mainly preformed using one of three major additive manufacturing techniques: inkjet, micro extrusion and laser assisted[1],[2]. Micro valve based printing offers a compromise between the fast printing of inkjet and the good handling of water based inks of micro extrusion. It could therefore potentially prove to be important for certain bioprinting applications but it has not been thoroughly tested so far. Mimicking blood vessels architecture is a major goal in tissue engineering as they are essential to provide the cells with a supply of oxygen and nutrients, especially for complex tissue architectures. Another example are attempts to reproduce stem cell crypt morphology in the large intestine[3], due to the importance of the intestine for functions such as drug administration, nutrients transport and cell differentiation. In this work, we use a Picodot jetting valve to ink jet two hydrogel based inks, one providing structure and the other a fugitive ink that is removed to create vascular and crypts-like structures[4],[5]. Materials and Methods: Ink formulations: 10%w/v gelatine (Type A, 300 bloom) ink solution was prepared by dissolving gelatine powder in DI water and was kept at 370C during printing process. Gelatine methacrylate (GelMA) was synthesized following a previously reported procedure[6]. GelMA ink was prepared by dissolving 15%w/v GelMA and 0.3% w/v photoinitiator (Irgacure 2959) in Phosphate Buffer Saline. 3D Printing system: Structures of intestinal crypts and vascular structures were fabricated by a jetting valve system Picodot LV (Nordson EFD). The Picodot print head jetting is synchronized with a 3-axis high performance linear stage (Aerotech). The ink was jetted through a 50 μm nozzle by an applied air pressure of 30 psi and a rod movement driven by two piezoelectric actuators. Two gelatine-based inks were used. Firstly, gelatine was used as a fugitive ink which was removed in a final step to create the vascular spaces, and secondly, photopolymerizable GelMA was used for the structural part of the scaffold. For printing intestinal crypts structures, we printed an array of pillars using gelatine as a sacrificial template. For vascular structure, we printed a branched 3D network of gelatine. In both cases, GelMA was casted onto the printed template and the gelatine was washed by DI water at 370 C. The vascular structure was perfused with red dye to prove the structure was able to support perfusion. Results and Discussion: Crypts structures were obtained after eliminating the sacrificial ink. The obtained vascular structure was perfused with red dye to test flow feasibility. In addition, red dye diffusion throughout the GelMA scaffold was observed. Conclusion: We demonstrated the feasibility of a simple fabrication process for recreating intestinal crypts and vascular structures using Picodot LV jetting valve embedded in a linear stage using gelatine as a fugitive ink and GelMA as a scaffold. As a next step, we plan to use cell laden GelMA for casting and monitor the viability of the cells.

Development of disc bending fatigue test technique for equi-biaxial loading

The disc bending fatigue test technique was developed to investigate the fatigue life under an equi-biaxial loading condition. In this test, a uniform thickness disc specimen was subjected to a bending load by applying air pressure on the specimen surface. Eleven specimens made of Type 316 stainless steel were tested in a room temperature ambient environment. The crack initiation and growth behaviors during the test were observed through a transparent window. The fatigue life was defined when the peak pressure measured near the specimen surface was reduced to 95% of the supplied air pressure. The fatigue life obtained by the disc bending fatigue test was shorter than that obtained by the uniaxial and plate bending fatigue tests for the same principal strain range. It was confirmed that the equi-biaxial loading condition reduced the fatigue life. The finite element analysis together with test results revealed that the crack was initiated at the edge of the specimen when the specimen thickness was less than 1.0mm. The specimen thickness should be 1.2mm in order to maximize the strain range at the specimen center. It was concluded that the disc bending fatigue test can derive the fatigue life under an equi-biaxial loading condition, for which strain range is measured at the specimen center.

Hydraulic traits of Norway spruce sapwood estimated by Fourier transform near-infrared spectroscopy (FT-NIR)

The potential of Fourier transform near-infrared (FT-NIR) spectroscopy to predict hydraulic traits in Norway spruce (Picea abies (L.) Karst.) sapwood was evaluated. Hydraulic traits tested were P50 (applied air pressure causing 50% loss of hydraulic conductivity) and RWL50 (applied air pressure causing 50% relative water loss). Samples came from 24-year-old spruce clones. FT-NIR spectra were collected from the axial (transverse) and radial surface of each solid wood sample for the prediction of P50 and RWL50. Partial least squares regression (PLS-R) models with cross validation were used to establish relationships between the FT-NIR spectra and the reference data from hydraulic properties analysis. The impact of the wavenumber range and the pretreatment during the PLS-R model development and the differences between the axial and radial surfaces were shown. Based on the values of the coefficient of determination (r2) and the root mean square error of cross validation, predicted results were evaluated as acceptable. The models from the axial surface gave better results than the models from the radial surface for P50 (r2 = 0.65), as well as for RWL50 (r2 = 0.77). The first approach to predict hydraulic properties such as P50 and RWL50 by FT-NIR spectroscopy can be regarded as successful. We conclude that the method has high potential to be put into practice as a rapid, reliable, and nondestructive method to determine P50 and RWL50.

PTH-191 In vitromodelling of reflux in the presence of the post-prandial acid pocket: validation of reflux supression by gaviscon products

Introduction The region of unbuffered acidity on top of the gastric contents after a meal, known as the post-prandial acid pocket, 1 is a chief aetiological factor responsible for the frequently experienced post-prandial reflux. We previously developed an in vitro model of the post-prandial acid pocket adhering to the physiological characteristics described in the clinical literature. 2 Here we further improve this in vitro model to simulate the occurrence of reflux events and also evaluate some anti-reflux products. Method A standard refluxogenic meal (McDonalds double sausage and egg McMuffin + black coffee) was blended with 40 ml 0.01 M HCl and transferred to the model stomach within a sealed water chamber. An acid pocket layer of 0.1 M HCl was applied to meet the established clinically measured parameters (70 ml and 2.5 cm depth). A reflux event was simulated by applying air pressure into the water chamber rapidly and the refluxate was captured in a syringe through the modelled lower oesophageal sphincter. The model was validated with two alginate-based anti-reflux products [UK manufactured Gaviscon Double Action (GDA) and USA manufactured Gaviscon Extra Strength (GES)]. Results Application of 50 ml of air to the in vitro post-prandial acid pocket model resulted in refluxate volume of 10 ml (SD 1.7 ml) which is a representative refluxate volume. 3 GDA suppressed reflux in the model in a dose dependent manner with 20 ml maximum GDA dose completely supressing 5 sequential reflux events. 10 ml GDA dose let through 2.7 ml of the reflux (mean of 5 events) and 2.5ml GDA dose let through 5.9 ml of the reflux (mean of 5 events). 20 ml maximum dose of GES did not supress reflux and 7.0 ml of the reflux was let through at maximum dose (mean of 5 events). Conclusion This in vitro model is representative of a fed stomach via introduction of a classic refluxogenic meal. The post-prandial acid pocket that is modelled represents that described in clinical studies and the model takes into account the pressure changes during a reflux event. Alginate raft forming anti-reflux products GDA and GES were chosen to validate the model and GDA was able to suppress reflux events in a dose dependent manner with maximum dose (20 ml) totally supressing all reflux events. In contrast GES that does not form a coherent buoyant raft 4 was a poor reflux suppressant. This in vitro model of reflux of the post-prandial acid pocket has potential to screen and evaluate test products without the need of clinical studies. Disclosure of interest None Declared. References Fletcher, et al . Gastroenterology 2001;121:775–783 Fisher, et al . UEG Journal 2014; 2 (Suppl 1):A578 Sifrim Gut 2005; 54 :175–178 Hampson, et al . Int J Pharm. 2005;294:137–147

Cell-encapsulating alginate microsized beads using an air-assisted atomization process to obtain a cell-laden hybrid scaffold.

The air-assisted atomization process is a method for straightforwardly spraying a liquid to obtain microsized capsules. In this study, we used the atomization process to obtain homogeneous cell-laden alginate-based microbeads for tissue regeneration. To achieve appropriate processing conditions, various weight fractions of alginate, various distances between the spraying nozzle and collector, and various applied air pressures were investigated. Through the selected conditions (3 wt% of alginate, 7 cm distance between the nozzle and collector, and 90 kPa air pressure), we prepared homogeneous microsized cell-laden beads (average diameter = 15.5 ± 6.1 μm) with reasonable cell viability (>90%). The feasibility of the sprayed microbeads was evaluated in terms of in vitro cellular activities, cell proliferation, and the morphology of the proliferating cells. In particular, the cell-sprayed microbeads showed 1.74-fold greater cell proliferation rate compared to the macro-sized cell-laden beads. Furthermore, the sprayed cell-laden alginate beads, prepared with the selected processing conditions, were combined with melt-plotted polycaprolactone struts to obtain a new hybrid scaffold. The cells in the hybrid scaffold were viable and proliferated well over several culture periods.

1P1-M02 液滴生成を目的とした分離構造を持つランジュバン型ねじり振動子の開発

In many fields, such as medicine and cosmetics production, it is an important proposition to generate small and uniform droplets of various liquids. In order to realize these droplets' generation, we have been using a bolt-clamped Langevin-type transducer and a micropore plate. The purpose of this study is to fabricate a bolt-clamped Langevin-type transducer having separated structure for cleaning, and to generate droplets by using this device. First, we have proposed a new structure, and designed a bolt-clamped Langevin-type transducer which consists of some separated parts. Next, we have generated and evaluated droplets in the air by using pure water. When the micro pore diameter, the applied air pressure and the resonance frequency were 50μm, 100kPa and 37kHz, the average diameter of pure water droplets and standard deviation of diameter were 169.1μm and 3.44, respectively.

Motion of an isolated liquid plug inside a capillary tube: effect of contact angle hysteresis

Dynamics of a single, small and isolated partially wetting liquid plug (of known length L and wettability), placed at rest inside a long, dry, circular capillary tube (D = 1.5 mm), and subsequently quasi-statically pushed from one end by applying air pressure, the other end being kept exposed to atmosphere, are reported. The air pressure first overcomes the ‘static’ friction manifested by the three-phase contact line at the advancing and receding menisci, and then, the plug motion gets initiated, eventually leading to a terminal velocity (Ca ~ 2.8 × 10−5), when pressure force balances net frictional resistance due to viscous and surface forces. It is seen that, under steady motion, the curvature profiles of the advancing and receding menisci of liquid plug, respectively, remain the same, independent of the plug length. Steady-state pressure drop is dominated by the contribution due to contact angle hysteresis, which is also independent of the plug length. Increasing the system wettability drastically decreased the contact angle hysteresis and the associated net pressure drop.

Automated heavy load lifting and moving system using pneumatic cushions

Abstract This article presents a new control method for a pneumatic cushion for transporting heavy payloads. Pneumatic cushions are particularly useful for moving structural or non-structural components over hard, smooth floors. They can be put directly under load, lifted to a small height by applying air pressure and moved. A thin, friction-reducing air film is formed under the cushion during lifting. Currently, pressure is usually controlled manually, which causes difficulty in establishing an appropriate pressure value, especially when the load is distributed unevenly between multiple cushions. In practice, the pressure is often set higher than is necessary to move the load. Excessive pressure does not reduce friction, but increases air consumption. Hence, in this article an effort is described to obtain the minimum allowable pressure. The first part of the article includes the theoretical background, detailed models of the proposed automatic controllers and the parameters of a test bench. Experiments were carried out with a typical manual control system and two automatic controllers, with PID and fuzzy logic algorithms. The results indicate that automation of the control system significantly reduces air consumption and shortens the time needed to obtain the correct pressure. Moreover, it improves the stability of the load by allowing more accurate vertical positioning of individual cushions.

Liquid metal actuation-based reversible frequency tunable monopole antenna

We report the fabrication and characterization of a reversible resonant frequency tunable antenna based on liquid metal actuation. The antenna is composed of a coplanar waveguide fed monopole stub printed on a copper-clad substrate, and a tunnel-shaped microfluidic channel linked to the printed metal. The gallium-based liquid metal can be injected and withdrawn from the channel in response to an applied air pressure. The gallium-based liquid metal is treated with hydrochloric acid to eliminate the oxide layer, and associated wetting/sticking problems, that arise from exposure to an ambient air environment. Elimination of the oxide layer allows for reliable actuation and repeatable and reversible tuning. By controlling the liquid metal slug on-demand with air pressure, the liquid metal can be readily controllable to connect/disconnect to the monopole antenna so that the physical length of the antenna reversibly tunes. The corresponding reversible resonant frequency changes from 4.9 GHz to 1.1 GHz. The antenna properties based on the liquid metal actuation were characterized by measuring the reflection coefficient and agreed well with simulation results. Additionally, the corresponding time-lapse images of controlling liquid metal in the channel were studied.

Soil water thermodynamic to unify water retention curve by pressure plates and tensiometer

The pressure plate method is a standard method for measuring the pF curves, also called soil water retention curves, in a large soil moisture range from saturation to a dry state corresponding to a tension pressure of near 1500 kPa. However, the pressure plate can only provide discrete water retention curves represented by a dozen measured points. In contrast, the measurement of the soil water retention curves by tensiometer is direct and continuous, but limited to the range of the tensiometer reading: from saturation to near 70-80 kPa. The two methods stem from two very different concepts of measurement and the compatibility of both methods has never been demonstrated. The recently established thermodynamic formulation of the pedostructure water retention curve, will allow the compatibility of the two curves to be studied, both theoretically and experimentally. This constitutes the object of the present article. We found that the pressure plate method provides accurate measurement points of the pedostructure water retention curve h(W), conceptually the same as that accurately measured by the tensiometer. However, contrarily to what is usually thought, h is not equal to the applied air pressure on the sample, but rather, is proportional to its logarithm, in agreement with the thermodynamic theory developed in the article. The pF curve and soil water retention curve, as well as their methods of measurement are unified in a same physical theory. It is the theory of the soil medium organization (pedostructure) and its interaction with water. We show also how the hydrostructural parameters of the theoretical curve equation can be estimated from any measured curve, whatever the method of measurement. An application example using published pF curves is given.

Fabrication of cell penetration enhanced poly (l-lactic acid-co-ɛ-caprolactone)/silk vascular scaffolds utilizing air-impedance electrospinning

In the vascular prosthetic field, the prevailing thought is that for clinical, long-term success, especially bioresorbable grafts, cellular migration and penetration into the prosthetic structure is required to promote neointima formation and vascular wall development. In this study, we fabricated poly (l-lactic acid-co-ɛ-caprolactone) P(LLA-CL)/silk fibroin (SF) vascular scaffolds through electrospinning using both perforated mandrel subjected to various intraluminal air pressures (0–300kPa), and solid mandrel. The scaffolds were evaluated the cellular infiltration in vitro and mechanical properties. Vascular scaffolds were seeded with smooth muscle cells (SMCs) to evaluate cellular infiltration at 1, 7, and 14 days. The results revealed that air-impedance scaffolds allowed significantly more cell infiltration as compared to the scaffolds fabricated with solid mandrel. Meanwhile, results showed that both mandrel model and applied air pressure determined the interfiber distance and the alignment of fibers in the enhanced porosity regions of the structure which influenced cell infiltration. Uniaxial tensile testing indicated that the air-impedance scaffolds have sufficient ultimate strength, suture retention strength, and burst pressure as well as compliance approximating a native artery. In conclusion, the air-impedance scaffolds improved cellular infiltration without compromising overall biomechanical properties. These results support the scaffold's potential for vascular grafting and in situ regeneration.

An AlN cantilever for a wake-up switch triggered by air pressure change

This research reports an AlN cantilever with an air chamber for a wake-up switch triggered by air pressure change. The proposed sensor is designed to fulfil both high sensitivity and low power consumption. By combining an air chamber to the one side of the AlN cantilever surface, the barometric pressure change generates a piezoelectric voltage. Thus, a wake-up switch triggered by air pressure change can be achieved using an AlN cantilever. The size of the fabricated AlN cantilever was 2000 μm × 1000 μm × 2 μm. The sensitivity to static differential pressure was 11.5 mV/Pa at the range of −20 Pa to 20 Pa. We evaluated the response of the sensor, which was composed of the AlN cantilever and the chamber of 60 ml in volume, when air pressure change was applied. The output voltage increased with increasing the applied air pressure change. It was observed that the maximum output voltage of 50 mV was generated when the air pressure change was 13 Pa.

Bending-induced electromechanical coupling and large piezoelectric response in a micromachined diaphragm

We investigated the dependence of electromechanical coupling and the piezoelectric response of a micromachined Pb(Zr0.52Ti0.48)O3 (PZT) diaphragm on its curvature by observing the impedance spectrum and central deflection responses to a small AC voltage. The curvature of the diaphragm was controlled by applying air pressure to its back. We found that a depolarized flat diaphragm does not initially exhibit electromechanical coupling or the piezoelectric response. However, upon the application of static air pressure to the diaphragm, both electromechanical coupling and the piezoelectric response can be induced in the originally depolarized diaphragm. The piezoelectric response increases as the curvature increases and a giant piezoelectric response can be obtained from a bent diaphragm. The obtained results clearly demonstrate that a high strain gradient in a diaphragm can polarize a PZT film through a flexoelectric effect, and that the induced piezoelectric response of the diaphragm can be controlled by adjusting its curvature.

Aeroelasticity-based fluid agitation for lab-on-chips

In this study, we report a robust agitation method for small-volume liquids. It utilizes an elastic diaphragm as the bottom of a liquid chamber, upon which an initial tension is also applied to enhance the aeroelasticity effects at small/micro scales. As a result, spontaneous vibration of the diaphragm can be induced by an external air flow, which further provides fluid agitations. The device structure is simple and can be easily fabricated at low cost. More importantly, the vibration amplitude is controllable and varies widely from several tens to several hundred micrometers depending on the applied air pressure. The resulting agitation is effective and applicable at high viscosities of up to 900 cSt. The influences of air pressure and liquid viscosity on the vibration frequency are discussed. Potential applications of this technique for solid particle agitation, focusing and fluid mixing are also demonstrated.