Ultrasonic Nozzle Research Articles

Development of Droplets Penetrating Roots Performance Test Device and Tests Applied this Device in Ultrasonic Aeroponic System

Extremely flourishing roots of aeroponic plant lead droplets difficult to penetrate into the core of roots. This phenomenon is so-called “external is wet but internal is dry” and seriously affects areoponic efficiency, even result in aeroponic culture failure. In order to research droplets penetrating roots performance in ultrasonic aeroponic system, an intelligent test device was developed. This device included two ultrasonic nozzles whose working frequencies were 1.7MHz and 40kHz respectively, nozzles’ drive circuit, acquisition system of humidity and temperature based on ARM 9.0 and axial flow fan. The following conclusions were suggested: under the mature cherry tomatoes root system density cultured in aeroponic system, droplets generated by 1.7MHz ultrasonic atomizing nozzle were easier to penetrate into the core of the root; both size and concentration of droplets influenced droplets penetrating into the root; when 1.7MHz nozzle was used to atomization, the best penetrating condition was found in supply air rate 0.021and spray volume 0.4L/h; for 40kHz atomizing nozzle , the best penetrating condition was found in supply air rate 0.021and spray volume 1.2L/h; for 1.7MHz nozzle the worst work conditions of penetrating into the root were that supply air rate was 0.014and spray volume was 0.8L/h and for 40kHz nozzle that was supply air rate 0.033and spray volume 1.2L/h.

Fabrication of composite particles by liquid–liquid interfacial crystallization using an ultrasonic spray nozzle

The purpose of this study was to produce composite particles, consisting of core starch particles coated with glycine, by liquid–liquid interfacial crystallization with an ultrasonic spray nozzle and to investigate the effect of operating conditions on glycine particle morphology. We confirmed that ultrasonic irradiation could improve the coating efficiency of the core starch particles during the crystallization process. We also investigated the transformation between different polymorphs of glycine crystals that covered the starch surface. The coating efficiency of the fine glycine crystals on the starch particles was improved by using an ultrasonic spray nozzle rather than anti-solvent crystallization without an ultrasonic spray nozzle. The glycine crystals on the surface of starch particles transformed from unstable to stable forms according to the solution-mediated mechanism and Ostwald rule of stages. The interaction between the core particles and guest particles was found to be a key factor in producing the composite particles. The results indicate that this crystallization process using the ultrasonic spray nozzle is promising for efficiently producing composite particles.

Handheld and automated ultrasonic spray deposition of conductive PEDOT:PSS films and their application in AC EL devices

In this contribution we explore the spray deposition technique to achieve smooth films based on the conductive polymer PEDOT:PSS. Two different spray systems were used and compared namely: (a) handheld airbrush and (b) automated ultrasonic spray system. For each system a number of parameters were pre-adjusted during coating control experiments such as spray head distance, angle and cone for airbrush as well as flow rate, power and focus for ultrasonic nozzle. Water-based solutions of PEDOT:PSS having 20% of N-methylpyrrolidone (NMP) were sprayed on glass substrates at temperatures ranging from 75 to 150°C. The resulting films were further chemically treated with ethylene glycol (EG) and evaluated with respect to their morphological, electrical and optical properties. Before EG-treatment the ultrasonic spraying resulted in smoother films with conductivity up to 2–3.9 times higher than their airbrushed counterparts. Deposition temperature proved to have minor effect on the morphological and electro-optical properties of PEDOT:PSS films. On the other hand, the film conductivity was enhanced, peaking at 610.1Scm−1 for ultrasonic spraying, when further chemically modified by EG. IR microspectroscopy mapping analysis, Raman spectroscopy and XRD data indicated a phase-separation between PEDOT and PSS chains and increasing crystallinity in the ultrasonically sprayed films. The application of such PEDOT:PSS films as transparent electrode in flexible AC EL devices is demonstrated.

Faraday instability-based micro droplet ejection for inhalation drug delivery.

We report here the technology and the underlying science of a new device for inhalation (pulmonary) drug delivery which is capable of fulfilling needs unmet by current commercial devices. The core of the new device is a centimeter-size clog-free silicon-based ultrasonic nozzle with multiple Fourier horns in resonance at megahertz (MHz) frequency. The dramatic resonance effect among the multiple horns and high growth rate of the MHz Faraday waves excited on a medicinal liquid layer together facilitate ejection of monodisperse droplets of desirable size range (2-5 µm) at low electrical drive power (<1.0 W). The small nozzle requiring low drive power has enabled realization of a pocket-size (8.6 × 5.6 × 1.5 cm3) ultrasonic nebulizer. A variety of common pulmonary drugs have been nebulized using the pocket-size unit with desirable aerosol sizes and output rate. These results clearly provide proof-of-principle for the new device and confirm its potential for commercialization.

Performance of propellant for ultrasonically aided electric propulsion

Ultrasonically aided electric propulsion (UAEP) is a new type of colloid thruster which uses ultrasonic nozzle instead of the traditional capillary or needle emitter. This paper focuses on the effects of propellant upon the performance of UAEP system. Multiple solutions, such as doped formamide, water and tributyl-phosphate were employed and tested as the propellant. The relationships between the spray current and several characteristic parameters of the propellant, such as surface tension coefficient, electrical conductivity, viscosity and doped solute, were experimentally investigated. The experimental results showed that the operation state of UAEP system was greatly influenced by the physical properties of the propellant. The solution of LiCl/tributyl phosphate was selected as the propellant for UAEP.

Thin films of carbon nanotubes via ultrasonic spraying of suspensions in N-methyl-2-pyrrolidone and N-cyclohexyl-2-pyrrolidone

Described is a method for ultrasonically spraying thin films of carbon nanotubes that have been suspended in organic solvents. Nanotubes were sonicated in N-methyl-2-pyrrolidone or N-cyclohexyl-2-pyrrolidone (CHP) and then sprayed onto a heated substrate using an ultrasonic spray nozzle. The solvent was quickly evaporated, leaving a thin film of randomly oriented nanotubes. Unlike other methods of spraying nanotube films, this does not require removal of surfactant after spraying and is compatible with creating films of functionalized nanotubes. Film thickness was controlled by the spray time and films were sprayed with thicknesses between 10 and 500 nm. Single-walled, multiwalled, and functionalized multiwalled nanotubes were sprayed. Transparent conducting thin films prepared by spraying single-walled carbon nanotubes dispersed in CHP demonstrated similar sheet resistance (for a given optical transmittance) as those prepared by spraying aqueous polymer-based dispersions that required postdeposition polymer removal.

Linear theory on temporal instability of megahertz faraday waves for monodisperse microdroplet ejection.

A linear theory on temporal instability of megahertz Faraday waves for monodisperse microdroplet ejection based on mass conservation and linearized Navier-Stokes equations is presented using the most recently observed micrometer- sized droplet ejection from a millimeter-sized spherical water ball as a specific example. The theory is verified in the experiments utilizing silicon-based multiple-Fourier horn ultrasonic nozzles at megahertz frequency to facilitate temporal instability of the Faraday waves. Specifically, the linear theory not only correctly predicted the Faraday wave frequency and onset threshold of Faraday instability, the effect of viscosity, the dynamics of droplet ejection, but also established the first theoretical formula for the size of the ejected droplets, namely, the droplet diameter equals four-tenths of the Faraday wavelength involved. The high rate of increase in Faraday wave amplitude at megahertz drive frequency subsequent to onset threshold, together with enhanced excitation displacement on the nozzle end face, facilitated by the megahertz multiple Fourier horns in resonance, led to high-rate ejection of micrometer- sized monodisperse droplets (>10(7) droplets/s) at low electrical drive power (<;1 W) with short initiation time (<;0.05 s). This is in stark contrast to the Rayleigh-Plateau instability of a liquid jet, which ejects one droplet at a time. The measured diameters of the droplets ranging from 2.2 to 4.6 μm at 2 to 1 MHz drive frequency fall within the optimum particle size range for pulmonary drug delivery.

Concurrently pumped ultrasonic spray coating for donor:acceptor and thickness optimization of organic solar cells

We assess the utility of concurrent spray coating to efficiently screen and optimize solutions for organic solar cells. With this technique two independent solutions are coaxially pumped to the ultrasonic nozzle tip of the spray coater, where a micron-scale mist of droplets, each consisting of one of the two respective solutions with negligible mixing, is ejected toward the substrate. Concurrent spray coating is shown to allow the scanning of two important photoactive layer parameters: thickness, by concurrently diluting concentrated donor:acceptor (D:A) solution with pure solvent, and D:A ratio by concurrently spraying independent solutions of donor and acceptor. The assessment is done using the archetypal poly(3-hexylthiophene) (P3HT):(6,6)-phenyl C61-butyric acid methyl ester (PCBM) system. By allowing the droplets to coalesce on the substrate prior to drying, the resulting film realizes a favorable morphology, confirmed via high-performance OSC devices, with a peak efficiency of 4.1%, 72% fill factor, 9.3mA/cm2 short circuit current density, and a 620mV open circuit voltage.

Properties of acoustic resonance in double-actuator ultra-sonic gas nozzle: numerical study

The ultra-sonic gas atomization (USGA) nozzle is an important apparatus in the metal liquid air-blast atomization process. It can generate oscillating supersonic gas efflux, which is proved to be effective to enforce the atomization and produce narrow-band particle distributions. A double-actuator ultra-sonic gas nozzle is proposed in the present paper by joining up two active signals at the ends of the resonance tubes. Numerical simulations are adopted to study the effects of the flow development on the acoustic resonant properties inside the Hartmann resonance cavity with/without actuators. Comparisons show that the strength and the onset process of oscillation are enhanced remarkably with the actuators. The multiple oscillating amplitude peaks are found on the response curves, and two kinds of typical behaviors, i.e., the Hartmann mode and the global mode, are discussed for the corresponding frequencies. The results for two driving actuators are also investigated. When the amplitudes, the frequencies, or the phase difference of the input signals of the actuators are changed, the oscillating amplitudes of gas efflux can be altered effectively.

Size Control of Particles with Changing Concentration of TIP used as a Precursor for Synthesis of TiO2 by Ultra-Sonic Spray and Pyrolysis Method

The nano sized titanium dioxide was synthesized by the ultra-sonic spray method and pyrolysis of TIP (titanium iso-propoxide), which was employed as the precursor solution. The fine liquid drop of the TIP sprayed by the ultra-sonic spray nozzle was conversed into TiO2 nano particles by pyrolysis through the hot tubular reactor. The concentration of TIP solution was controlled in the range of 0.1∼1.0 M and the morphology, the particle size, the crystal structure, and the surface area of synthesized TiO2 were investigated by SEM, TEM, XRD and N2-adsorption method, respectively. DSSC (dye sensitized solar cells) was also prepared by employing the synthesized TiO2 nano powder as the electrode and the photo-electrical property of TiO2 was compared in terms of efficiency of solar cells. It was further confirmed that the particle size of TiO2 was controlled with changing concentration of TIP solution. When 0.1 M TIP was used as the precursor solution, the size, the surface area and the crystal structure of synthesized TiO2 were approximately 10 nm (by TEM), 56 m2/g and the anatase structure, respectively. The particle size of TiO2 decreased with decreasing concentration of TIP solution. Therefore, it was concluded that the efficiency of DSSC's can be improved by employing high surface area and nano-sized TiO2 as the electrode.

Effect of Thickness on the Film Properties of Spray Deposited Copper Indium Sulfide Thin Films by Ultrasonic Impact Nozzle

In this study, copper-indium-sulfide (CuInS 2 ) thin films were deposited on soda lime glass substrates using ultrasonic spray pyrolysis (USP) technique from the aqueous solution of Copper(II)chloride-dehydrate (CuCl 2 ), indium(III)chloride (InCl 3 ) and thiourea (NH 2 CSNH 2 ). To investigate the effect of film thickness, different solution amounts were sprayed. As expected, the thickness of the films increased with increasing the amount of solution used. It has been obtained that thickness of the CuInS 2 absorber layer is critical for structural, morphological and optical properties. Crystal structure of the spray-deposited films was confirmed using X-ray Diffraction (XRD) analysis. The crystallite size of the films was ranging between 68 and 147 nm. X-ray photoelectron spectroscopy (XPS) study revealed that Cu concentration in the films increased by increasing the solution amount. Surface morphology of the films was investigated via scanning electron microscope (SEM). All sprayed films were defect free. Moreover, Cu rich-island formation was observed on the surface of CuInS 2 films sprayed using solutions more than 20 ml. Optical band gap energy of the films decreased from 2.85 to 1.40 eV with increasing the solution amount. As a result, thin films deposited using 30 ml solution was superior to others in terms of structural and optical properties. Moreover, it is very important to mention here that the ultrasonic impact nozzle used in this study enabled using very little amount of solution (0.015 ml/mm 2 ), which is approximately 10 times lower than solution reported previously. This promising result can be the key for large-area manufacturing of CuInS 2 based solar cells.

미세직경 얼음을 이용한 CO2하이드레이트 제조특성 연구

가스 하이드레이트는 순수한 물이 이루는 격자구조 내에 다양한 가스분자들이 선택적으로 포획되어진 고체상의 화합물로, 최근 이산화탄소를 포집, 수송, 저장 하는 CCS (Carbon Capture and Storage)기술에 이를 응용하려는 연구가 활발히 진행되고 있다. 가스 하이드레이트를 적용한 CCS 기술의 핵심은 효과적으로 <TEX>$CO_2$</TEX> 하이드레이트를 제조하는 기법의 개발이며, 본 연구에서는 초음파 노즐을 이용하여 수십 나노미터 직경의 미세수적을 통해 고속의 <TEX>$CO_2$</TEX> 하이드레이트 제조기술 개발하였고, 이 과정의 특성을 파악해 보았다. 주파수 2.4 MHz의 초음파 노즐을 이용하여 미세직경의 수적을 분무하고 이송가스(carrier gas)로 <TEX>$CO_2$</TEX>를 적용, 미세 수적과 <TEX>$CO_2$</TEX>가 동시에 급속 냉각되는 저온 반응기에 도입되어 다공질 얼음입자가 직접 평균 <TEX>$10.7{\mu}m$</TEX> 직경의 <TEX>$CO_2$</TEX> 하이드레이트로 생성되는 연속공정을 개발하였다. 미세직경 얼음입자를 시작물로 하여 정압조건에서 <TEX>$CO_2$</TEX> 하이드레이트가 생성되도록 하며 가스포집량을 측정, 그의 가스 포집속도를 알아본 결과, 미세직경이며 동시에 다공 얼음이 제공하는 높은 기-고 접촉면적으로 인해 가스 하이드레이트 생성에 매우 적합한 것을 알 수 있었으며, 제조된 <TEX>$CO_2$</TEX> 하이드레이트의 자기보존효과(self-preservation effect)를 실험으로 확인함으로서 <TEX>$CO_2$</TEX> 가스의 수송에도 이용 가능함을 알 수 있었다. Gas hydrate is an inclusion compound consisting of water and low molecular weight gases, which are incorporated into the lattice structure of water. Owing to its promising aspect to application technologies, gas hydrate has been widely studied recently, especially <TEX>$CO_2$</TEX> hydrate for the CCS (Carbon Capture and Storage) issue. The key point of <TEX>$CO_2$</TEX> hydrate technology for the CCS is how to produce gas hydrate in an efficient and economic way. In this study, we have tried to study the characteristic of gas hydrate formation using micro-sized ice through an ultrasonic nozzle which generate 2.4 MHz frequency wave. <TEX>$CO_2$</TEX> as a carrier gas brings micro-sized mist into low-temperature reactor, where the mist and carrier gas forms <TEX>$CO_2$</TEX> hydrate under <TEX>$-55^{\circ}C$</TEX> and atmospheric pressure condition and some part of the mist also remains unreacted micro-sized ice. Formed gas hydrate was average 10.7 of diameter at average. The starting ice particle was set to constant pressure to form <TEX>$CO_2$</TEX> hydrate and the consumed amount of <TEX>$CO_2$</TEX> gas was simultaneously measured to calculate the conversion of ice into gas hydrate. Results showed that the gas hydrate formation was highly suitable because of its extremely high gas-solid contact area, and the formation rate was also very high. Self-preservation effect of <TEX>$CO_2$</TEX> hydrate was confirmed by the measurement of <TEX>$CO_2$</TEX> hydrate powder at normal and at pressed state, which resulted that this kind of gas storage and transport could be feasible using <TEX>$CO_2$</TEX> hydrate formation.

Ejection of Uniform Micrometer-Sized Droplets from Faraday Waves on a Millimeter-Sized Water Drop

This Letter reports the first observation and theoretical analysis of a new phenomenon: one large spherical water drop ejecting simultaneously a very large number of monodisperse microdroplets. An ultrasonic nozzle with multiple-Fourier horns in resonance enables controlled excitation of megahertz Faraday waves on the free water surface. The temporal instability of such waves leads to the ejection of 3.5-4.4 μm monodisperse droplets at a high rate (>4.0×10(7) droplets/sec). This is in stark contrast to the Rayleigh-Plateau instability, which ejects one droplet at a time.

Condensation of Acetol and Acetic Acid Vapor and Nitrogen Using Sprayed Aqueous Liquid

A cellulose-derived fraction of biomass pyrolysis vapor was simulated by evaporating acetol and acetic acid with heated nitrogen. After generating the vapor/nitrogen mixture, it was superheated in a tube oven and condensed by contact with an aqueous mist created by an ultrasonic spray nozzle. The rates of condensation and fractions of vapor condensed were determined for various fluid flow rates to estimate liquid flow rates necessary to obtain complete acetol vapor condensation. The effect of noncondensible gas on the condensation was determined by varying the ratio of nitrogen to acetol vapor. For standard conditions, no effect of nitrogen content on rate was seen for vapor contents greater than 10 mol %, which would include any practical fast pyrolysis vapor. Increasing the concentration of condensed vapor in the aqueous solution spray, up to 30 wt %, had little effect on the condensation rate.

Water spray cooling of polymers

AbstractThe cooling process in conventional rotomolding is relatively long due to poor thermal conductivity of plastics. The lack of internal cooling is a major limitation although rapid external cooling is possible. Various internal cooling methodologies have been studied to reduce the cycle time. These include the use of compressed air, cryogenic liquid nitrogen, chilled water coils, and cryogenic liquid carbon dioxide, all of which have limitations. However, this article demonstrates the use of water spray cooling of polymers as a viable and effective method for internal cooling in rotomolding. To this end, hydraulic, pneumatic, and ultrasonic nozzles were applied and evaluated using a specially constructed test rig to assess their efficiency. The effects of nozzle type and different parametric settings on water droplet size, velocity, and mass flow rate were analyzed and their influence on cooling rate, surface quality, and morphology of polymer exposed to spray cooling were characterized. The pneumatic nozzle provided highest average cooling rate while the hydraulic nozzle gave lowest average cooling rate. The ultrasonic nozzle with medium droplet size traveling at low velocity produced satisfactory surface finish. Water spray cooling produced smaller spherulites compared to ambient cooling whilst increasing the cooling rate decreases the percentage crystallinity. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers

Numerical Analysis and Experimental Results by Silicon-Based MHz Ultrasonic Nozzles to Product of Monodisperse Droplets

Monodisperse de-ionized water droplets 4.5 μm in diameter have been produced in ultrasonic atomization using micro electro-mechanical system (MEMS)-based three-Fourier horn 1 MHz silicon nozzles. The required electrical drive power and voltage are 15 mW and 6.5 V, respectively. The nozzles measure 1.80 x 0.21 x 0.11 cm3 and can accommodate flow rate of 2 to 300 μl/min. As liquid enters the 200 μm x 200 μm central channel of the nozzle, a curved thin liquid film is maintained at the nozzle tip that vibrates longitudinally at the nozzle resonance frequency, resulting in formation of standing capillary waves on the free surface of the liquid film. As the tip vibration amplitude exceeds a threshold (critical or onset amplitude), the standing capillary waves become unstable (temporal instability) and a spray of monodisperse droplets (mist) is produced. The experimental results of resonance frequency, droplet diameter, voltage requirement and critical or onset amplitude support the predictions of the three-dimensional finite element simulation and the linear theory of capillary wave atomization mechanism.

Polycarbonate nanoparticles spray coated on silicon substrate using micro-electromechanical-systems-based high-frequency ultrasonic nozzle

Mono-disperse polycarbonate (PC) nanoparticles 20 nm in diameter was spray coated on silicon substrate using a novel high-frequency ultrasonic nozzle. Specifically, Bisphenol-A polycarbonate with a molecular weight ( M w ) of approximately 6.4 × 10 4 g/mol was first dissolved in pyridine. The resulting solution was sprayed into surfactant-containing de-ionized (DI) water using a 300 kHz silicon-based multiple-Fourier horn nozzle (MFHN). As pyridine was extracted into the water, PC nanoparticles formed but remained dispersed. This suspension of PC nanoparticles was then sprayed onto a silicon substrate using a 500 kHz 3-Fourier horn nozzle. Scanning electron microscopy (SEM) of the dried substrate revealed that PC nanoparticles were spread uniformly with no aggregation.

Resonant behaviors of ultra-sonic gas atomization nozzle with zero mass-flux jet actuator

The resonant behaviors of an ultra-sonic gas atomization nozzle with a zero mass-flux jet actuator were numerically investigated with FLUENT software by using a double precision unsteady two-dimensional pressure-based solver. The Spalart-Allmaras turbulence model was adopted in the simulations. Numerical results indicated that the oscillation properties of the gas efflux were effectively improved. Several resonatory frequencies corresponding to different vibration modes of gas were distinguished in the nozzle. With the changing of nozzle geometric parameters, different characters among those modes were elucidated by analyzing the propagations of pressure waves.

An Experimental Study of Atomization Characteristics of the Ultrasonic Spray Nozzle

The recent development in advanced packaging and MEMS applications has created a need for high aspect ratio lithography processes, ultrasonic spray coating is a very appropriate method to meet this requirement, the parameters of atomization are greatly affected the spray quality. By using a laser-phase Doppler analyzer (PDA), an experimental study was conducted of the atomization characteristics of the ultrasonic spray nozzle, water was used as the liquid to be atomized instead of photoresist and air was used as the auxiliary gas instead of nitrogen, the parameters of atomization characteristics under different operating conditions were measured, such as mean diameter D10 and diameter distribution of atomized droplet particles etc. The experimental measurement results indicate that the flow rate of atomized liquid and auxiliary gas have a significant impact on the spray characteristics, the nozzle can achieve a comparatively good atomization state under the condition of a relatively small flow rate of atomized liquid or a relatively high flow rate of auxiliary gas, the mean diameter D10 of droplets can be 18.39μm. The research findings can provide an underlying basis for the application of the ultrasonic spray nozzle.

Spray coating of PMMA for pattern transfer via electron beam lithography on surfaces with high topography

Spray coating of polymethylmethacrylate (PMMA) as electron beam resist on non planar surfaces is presented as a reliable technique for deposition of uniform resist layers with adjustable thickness at wafer scale. In the experiments a commercial spray coating system with an ultrasonic spray nozzle was used. Parameters which influence the quality of the resist layer with respect to uniformity across a 4in Si wafer, such as ultrasonic power and dispensed volume, were evaluated. The suitability of spray coated PMMA for the pattern transfer on surfaces with high topography was proven by PMMA spray coating of 8μm deep trenches etched into Si wafers. The PMMA was then electron beam exposed and chromium line patterns were transferred on the Si surface via a lift-off process.