Ultrasonic Horn Research Articles

Intensification of catechin extraction from the bark of Syzygium cumini using ultrasonication: Optimization, characterization, degradation analysis and kinetic studies

Catechin is a prominent polyphenolic component that possesses various medicinal properties. Present work communicates the intensification and optimization of catechin extraction from the bark of Syzygium cumini tree using stirred reactor, soxhlet, ultrasonic bath, and ultrasonic horn technique. The optimization of several parameters such as type of solvent, solid to solvent ratio (1:100 w/v), speed of agitation (300 RPM), extraction temperature (40 °C), and amplitude (20%) has been done for the maximization of catechin extraction yield. The kinetic (second-order rate mechanism) and degradation analysis (based on LC-MS characterization) have been performed to understand the extraction mechanism, forecast extraction stability, and avoid unwanted catechin degradation during ultrasonication. The effectiveness of different extraction techniques was compared based on the yield of catechin per unit of power dissipated. These studies revealed that ultrasonic horn produced maximum extraction yield (13.8 mg/g) in a shorter time (5 min), consumed less energy (0.2974 kJ), and gave the highest extraction rate (0.0910 g/mg.min) as compared to other techniques. The effectiveness of extraction using the ultrasonic horn was 39.67 mg/g.kJ. A mathematical model using the linear regression method was investigated for the process, which shows numerical correlation and significance factor between the yield and all other parameters.

Ultrasonically assisted surface modified CeO2 nanospindle catalysts for conversion of CO2 and methanol to DMC

This study developed a facile and effective approach to engineer the surface properties of cerium oxide (CeO2) nanospindle catalysts for the direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol. CeO2 nanospindles were first prepared by a simple precipitation method followed by wet chemical redox etching with sodium borohydride (NaBH4) under high intensity ultrasonication (ultrasonic horn, 20 kHz, 150 W/cm2). The ultrasonically assisted surface modification of the CeO2 nanospindles in NaBH4 led to particle collisions and surface reduction that resulted in an increase in the number of surface-active sites of exposed Ce3+ and oxygen vacancies. The surface modified CeO2 nanospindles showed an improvement of catalytic activity for DMC formation, yielding 17.90 mmol·gcat−1 with 100 % DMC selectivity. This study offers a simple and effective method to modify a CeO2 surface, and it can further be applied for other chemical activities.

Characterization of cavitation under ultrasonic horn tip – Proposition of an acoustic cavitation parameter

Acoustic cavitation, generated by a piezo-driven transducer, is a commonly used technique in a variety of processes, from homogenization, emulsification, and intensification of chemical reactions to surface cleaning and wastewater treatment. An ultrasonic horn, the most commonly used acoustic cavitation device, creates unique cavitation conditions under the horn tip that depend on various parameters such as the tip diameter, the driving frequency of the horn, its amplitude, and fluid properties. Unlike for hydrodynamic cavitation, the scaling laws for acoustic cavitation are poorly understood. Empirical relationships between cavitation dynamics, ultrasonic horn operating conditions, and fluid properties were found through systematic characterization of cavitation under the tip. Experiments were conducted in distilled water with various sodium chloride salt concentrations under different horn amplitudes, tip geometries, and ambient pressures. Cavitation characteristics were monitored by high-speed (200,000 fps) imaging, and numerous relations were found between operating conditions and cavitation dynamics. The compared results are discussed along with a proposal of a novel acoustic cavitation parameter and its relationship to the size of the cavitation cloud under the horn tip. Similar to the classical hydrodynamic cavitation number, the authors propose for the first time an acoustic cavitation parameter based on experimental results.

Combining Ultrasound and Capillary-Embedded T-Junction Microfluidic Devices to Scale Up the Production of Narrow-Sized Microbubbles through Acoustic Fragmentation.

Microbubbles are tiny gas-filled bubbles that have a variety of applications in ultrasound imaging and therapeutic drug delivery. Microbubbles can be synthesized using a number of techniques including sonication, amalgamation, and saline shaking. These approaches can produce highly concentrated microbubble suspensions but offer minimal control over the size and polydispersity of the microbubbles. One of the simplest and effective methods for producing monodisperse microbubbles is capillary-embedded T-junction microfluidic devices, which offer great control over the microbubble size. However, lower production rates (∼200 bubbles/s) and large microbubble sizes (∼300 μm) limit the applicability of such devices for biomedical applications. To overcome the limitations of these technologies, we demonstrate in this work an alternative approach to combine a capillary-embedded T-junction device with ultrasound to enhance the generation of narrow-sized microbubbles in aqueous suspensions. Two T-junction microfluidic devices were connected in parallel and combined with an ultrasonic horn to produce lipid-coated SF6 core microbubbles in the size range of 1-8 μm. The rate of microbubble production was found to increase from 180 microbubbles/s in the absence of ultrasound to (6.5 ± 1.2) × 106 bubble/s in the presence of ultrasound (100% ultrasound amplitude). When stored in a closed environment, the microbubbles were observed to be stable for up to 30 days, with the concentration of the microbubble suspension decreasing from ∼2.81 × 109/mL to ∼2.3 × 106/mL and the size changing from 1.73 ± 0.2 to 1.45 ± 0.3 μm at the end of 30 days. The acoustic response of these microbubbles was examined using broadband attenuation spectroscopy, and flow phantom imaging was performed to determine the ability of these microbubble suspensions to enhance the contrast relative to the surrounding tissue. Overall, this approach of coupling ultrasound with microfluidic parallelization enabled the continuous production of stable microbubbles at high production rates and low polydispersity using simple T-junction devices.

Control of Acoustic Energy Input for Cleaning of Industrial Boilers

A non-intrusive cleaning method for boiler tubes at Sasol Synfuels power station at Secunda, in the Mpumalanga province of South Africa, is preferred over conventional methods that require boiler shutdown. The elected non-intrusive cleaning method utilizes sound energy waves, produced by an acoustic horn. Due to the nature of sound propagation and the effectiveness required, there is a requisite to control and operate the sonic horn. If the acoustic horn’s sound frequency is too low, it will produce higher sound energy waves that will resonate with the plant’s harmonious frequency and cause structural damage. Conversely, if the sonic horn’s sound frequency is too high, excessive noise levels may be reached and annoy plant personnel. To prevent these undesirable outcomes posed by adopting acoustic cleaning, there needs to be a regulatory system incorporated into the configuration to mitigate vibrations and limit noise. The regulatory system comprises a control system that drives the acoustic horn’s sound frequency as intended through a set point. The designed control system meets the anticipated requirements, such that it has an ideal transient response of 0.562 s, a steady-state error achieved in 1.05 s, with 0.201% overshoot, and most importantly the closed-loop system is stable.

Design and development of ultrasonic assisted-rotational magnetorheological abrasive flow finishing (UA-RMRAFF) process

The rotational-magnetorheological abrasive flow finishing (R-MRAFF) process, as one of the derivatives of the abrasive flow finishing (AFF) process, has a high potential for surface modification. However, the R-MRAFF process is a major challenge in terms of finishing time. The present study aims to propose ultrasonic vibration has been proposed as a technical solution to deal with the technological challenges of the R-MRAFF process. A new finishing method called the ultrasonic assisted-rotational magnetorheological abrasive flow finishing (UA-RMRAFF) process has been developed for the first time in which ultrasonic vibrations are applied to the workpiece perpendicular to the magnetorheological polishing (MRP) fluid flow direction. For this purpose, the workpiece was first kept in dynamic condition. Then, an ultrasonic horn was designed using the finite element method (FEM) to apply maximum amplitude to the workpiece. To evaluate the finishing efficiency of the UA-RMRAFF process, experiments were conducted on the internal finishing of Al2024 tubes at different finishing times for investigating and observing its effect on surface roughness (Ra) and material removal (MR). In addition, a comparative study was performed between the UA-RMRAFF and R-MRAFF processes in terms of % change in Ra (%ΔRa) and % improvement in MR. Experimental findings illustrate that the UA-RMRAFF process provides a uniform and fine surface finish without surface defects such as a mirror up to the range of 25.5 nm, in addition to increasing MR. Based on the results of the comparative study, the UA-RMRAFF process performs surface modification faster than that of the R-MRAFF process. While confirming these findings, the morphological and topographic analysis of the surface of the finished samples emphasizes that the main difference between the UA-RMRAFF and R-MRAFF processes is in the sinusoidal motion path of abrasive particles on the workpiece surface asperities, which clearly shows the effect of ultrasonic vibrations.

Acoustic and hydrodynamic cavitation-based combined treatment techniques for the treatment of industrial real effluent containing mainly pharmaceutical compounds

The current work investigates the effectiveness of hybrid treatment techniques involving cavitation combined with AOPs for treating real industrial effluent obtained from common effluent treatment plant (CETP), which contains dominantly recalcitrant pharmaceutical pollutants. A laboratory scale study was performed initially using ultrasonic horn to optimize the operating parameters to be used for combination schemes as AC/H2O2, AC/Fe(II)/H2O2, AC/KPS and AC/O3. The maximum extent of Chemical Oxygen Demand (COD) reduction was observed as 83.53% for AC/Fe(II)/H2O2 system at 1:5 ratio of Fe(II) and H2O2 under the best operating conditions of 125 W ultrasonic power, 22 kHz frequency, pH of 3 and time of 60 min. The scaleup possibility of AC has been explored by utilizing a novel US reactor for the treatment of 4000 mL of effluent at the optimized conditions. Large scale US reactor also showed the best results for AC/ Fe(II)/H2O2 system yielding 81.47% COD reduction. A comparison of the efficacy of HC and AC has also been established by performing a set of experiments using the combinations as HC/ H2O2, HC/Fe(II)/ H2O2, HC/KPS, and HC/O3 at same capacity. A maximum COD reduction of 87.4% was achieved for the HC/Fe(II)/ H2O2 system at pH 3 and inlet pressure of 4 bar. The study also established the comparison of kinetic rate constants and treatment costs for different approaches. Overall, the large scale potential for the treatment of real industrial effluent involving the pharmaceutical pollutants using combination of cavitation and AOPs has been demonstrated.

Multiphysics modeling of ultrasound-assisted biomass torrefaction for fuel pellets production

When an ultrasound wave propagates through a volume of biomass medium, the majority of the energy in the acoustic field is absorbed locally by the biomass, resulting in the generation of heat. This torrefaction effect results in a temperature increase of the biomass, converting biomass into a coal-like intermediate with upgraded fuel properties over the original biomass. However, few analyses can be found in the literature explaining the mechanism of ultrasound-assisted biomass torrefaction. This research aims to model an ultrasound-assisted biomass torrefaction system. The developed multiphysics model depicts the piezoelectric effect of a transducer, the vibration amplitude at the output end of the ultrasonic horn, and the acoustic intensity and temperature distributions in the biomass medium. The vibration amplitude and frequency of the ultrasonic horn were measured by a non-contact capacitive sensor, and it is verified the model can accurately simulate the ultrasonic vibration of the experimental system. The temperature at the center of the biomass was measured to validate the model’s temperature prediction. Both simulation and experiment showed that ultrasound-assisted biomass torrefaction can create torrefied fuel pellet within 60 seconds.

Modelling Nucleation during Electrodeposition By MODEL Method. Parametric Identification Considering Agitation By Rde or Ultrasound

Nowadays, 40% of the world wide used energy is provided by electric power and this share should reach about 60% by 2040. For environmental reasons, it is crucial to ensure low dissipation loss in power electronic devices by optimizing energy conversion. In the field of renewable energies and automotive electronics, possible energy savings are estimated to be between 20 and 35%. For that purpose, innovative power components and modules are required, with a growing interest for fast and simple joining processes in their fabrication management, in the case for example of the assembly of large-size double-side cooled modules. Several options are possible, including free sintering of metallic pastes or electroforming welding. In all cases, this requires a great control of both surfaces to be joined, mostly prepared by electrodeposition (microstructure, porosity, alloy composition). But the final properties of electrodeposited coatings are strongly dependent of the first nucleation steps, which influence the whole layer structure. In this frame, the modelling of a nucleation process followed by diffusion limited three dimensional growth is an area of promising interest. The study of potentiostatic current transients is a relevant methodology, allowing the determination of several parameters such as nucleation rate, nucleus density, and number of active sites. Different competing models are available, such as Scharifker and Hills [1] and Scharifker and Mostany [2]. By using the model method i.e. the identification of the model parameters by error minimization, it is possible to reach an accurate description of the first layer growth in the case of different metals such as silver and copper. Nevertheless, little attention have been paid to changes in hydrodynamic conditions, for example in the study of current response under forced convection [3]. The present work describes the extension of the model method to the modelling of the first steps of nucleation growth in the case of a sample exposed to an ultrasonic irradiation, which was compared to forced convection induced by a rotating disc electrode at the very same agitation level (equivalent velocity [4,5]. Eventually, the case of electrodeposited alloys was examined, as a function of their Brenner classifications (anomalous and normal codeposition [6]). The limitation of the data processing by the numerical approach are also discussed.[1] Scharifker, B. & Hills, G. Theoretical and experimental studies of multiple nucleation. Electrochimica Acta 28, 879–889 (1983).[2] Scharifker, B. R. & Mostany, J. Three-dimensional nucleation with diffusion controlled growth. J. Electroanal. Chem. Interfacial Electrochem. 177, 13–23 (1984).[3] Hyde, M. E. & Compton, R. G. Theoretical and experimental aspects of electrodeposition under hydrodynamic conditions. J. Electroanal. Chem. 581, 224–230 (2005).[4] Pollet B.G., Hihn J.-Y., Doche M.L, Mandroyan A., Lorimer J.P., Mason T.J “Transport limited currents close to an ultrasonic horn: equivalent flow velocity determination”, Journal of Electrochemistry Society, 154(10), E131-E138, (2007)[5] A. Nevers, L. Hallez, F. Touyeras, J.-Y. Hihn, Effect of ultrasound on silver electrodeposition: Crystalline structure modification, Ultrason. Sonochem. 40 (2018)[6] Brenner, A. Electrodeposition of alloys. Principles and practice Volume II, (1963).

Ultrasonic-assisted spray drying as a tool for improving the instant properties of egg white powder

The mechanism by which high-intensity (20 kHz) ultrasonic treatment affected the rehydration performance and microstructure of egg white powder (EWP) was explored in this study. The wettability and dispersibility of EWP prepared from high-intensity ultrasound treated egg white liquid were observed to have an exciting enhancement. Furthermore, the most excellent dispersibility (65.67 s), solubility (90.33 g/100 g) and stability (98 %) of EWP were detected when ultrasonic treatment (120 W, 20 kHz, 10 mm ultrasonic horn) was performed for 10 min. SDS-PAGE results showed that ultrasonic treatment promoted the depolymerization of the original protein macromolecular aggregates. The particle size and scanning electron microscopy results also indicated that the particle size of EWP tended to decrease. Additionally, the zeta potential and surface hydrophobicity analyses suggested a tendency to first increase and then decrease over time. Overall, the instant properties of EWP were improved due to the changes of protein microstructure and conformation caused by ultrasonic treatment. These results revealed the mechanism of high intensity ultrasound affecting the instant properties and microstructure of EWP, which provided a theoretical basis for improving the rehydration of other food protein powder. • Ultrasound treatment improved the instant solubility of egg white powder. • The contact angle of egg white powder decreased and the wettability increased. • The dry and wet methods showed the particle size of egg white powder decreased. • SEM revealed that the microstructure of ultrasound-treated EWP was altered.

A new design of wide blade ultrasonic horns using Non-Uniform Rational B-Spline shaped slots

In the present study, for the first time, the shapes of slots of wide blade horns are optimized using Non-Uniform Rational B-Spline (NURBS) curves. Here, two 20 kHz horns with different gain ratios (2.5 and 3.5) are designed. The amplitude uniformity and maximum stress of horns are regarded to design. Some control points are used to define the shape of slots, and the position and weight of these points are determined. The genetic algorithm with a link to Abaqus is applied for the optimization process. The simulation results show that the designed horns have high amplitude uniformity equal to 0.978, 0.965. Also, the maximum stresses are 73.08 MPa and 78.52 MPa, which are less than the fatigue strength with a safety factor of 2. It is found that the stress values in the bottom of NURBS-shaped slots are considerably lower than the simple slots, making it possible to design the horns with a higher gain ratio without fatigue failure. Finally, the performance of the present design is verified by doing some experiments on the fabricated horn, which confirms that the proposed design can be successfully utilized as a new method to design wide blade horns.

Improvements in crystallization of copper sulphate using ultrasound and comparison with conventional method

The present work aims to demonstrate the beneficial effect of using ultrasound on the metastable zone width (MSZW), induction time, yield and the crystal morphology for copper (II) sulphate pentahydrate. Effect of saturation temperature, initial concentration, stirring speed, cooling temperature, and cooling media on performance of crystallization process was investigated using conventional and US based method (both ultrasonic horn and ultrasonic bath). It was observed that the highest yield of 98.7% was obtained for US horn followed by 97.6% using US bath and 79.3% using conventional methods under optimized conditions. The metastable zone width and induction time significantly reduced due to ultrasound. Uniform and smaller size crystals were also seen in the case of ultrasound assisted approach whereas agglomeration of crystals appeared in the case of conventional approach. The energy requirement showed the trend of US horn < US bath < conventional approach. Overall, the application of ultrasound for crystallization of copper (II) sulphate pentahydrate was found promising to improve the process of crystallization in terms of MSZW, induction time, yield and the crystal behavior.

Numerical Investigation of the Effect of Uniform Cutout on Performance of Ultrasonic Horn for Machining Nomex Honeycomb Core Material

Ultrasonic horn is utilized in order to enhance the amplitude of vibration transmitted by the transducer in an ultrasonic machining system. It plays a vital role in vibration amplification to a magnitude suitable for efficient machining of materials. Ultrasonic machining system has to operate at a frequency of at least . Therefore, horn may be subjected to high magnitude of stresses leading to failure. Mechanical horn is designed to get optimum vibration amplification while keeping stresses in acceptable limits. In this research an ultrasonic compound horn was designed with through cutout of uniform diameter. The performance of ultrasonic horn was observed by varying the cutout diameter by modelling horns of four different materials: titanium, aluminum, steel and stainless steel respectively. Modal analysis was performed for computing modal frequencies in the axial direction, whereas harmonic analysis was carried out in order to determine vibration amplitude, stresses and factor of safety. The effect of varying frequency ratio on vibration magnification, stresses, and factor of safety were also investigated. The axial modal frequency was observed to increase, whereas amplitude of vibration and stresses were observed to decrease by increasing the cutout size. Titanium was found to be the most suitable material for ultrasonic horns, because it provided up to 159.4 % more amplitude of vibration and 3 times higher safety factor thus operating life as compared to other materials.

Effects of ultrasonication on the DBP formation and toxicity during chlorination of saline wastewater effluents

Chlorine disinfection of saline wastewater effluents rich in bromide and iodide forms relatively toxic brominated and iodinated disinfection byproducts (DBPs). Ultrasonication is a relatively new water treatment technology, and it is less sensitive to suspended solids in wastewaters. In this study, we examined the effects of ultrasonication (in terms of reactor type and combination mode with chlorination) on the DBP formation and toxicity in chlorinated primary and secondary saline wastewater effluents. Compared with the chlorinated wastewater effluent samples without ultrasonication, ultrasonic horn pretreatment of the wastewater effluent samples reduced the total organic halogen (TOX) levels in chlorination by ∼30%, but ultrasonic bath pretreatment of the wastewater samples did not significantly change the TOX levels in chlorination, which might be attributed to the higher energy utilization and decomposition extent of organic DBP precursors in the ultrasonic horn reactor. Moreover, the TOX levels in the chlorinated samples with ultrasonic horn pretreatment (USH–chlorination), simultaneous treatment (chlorination+USH) and subsequent treatment (chlorination–USH) were also significantly reduced, with the maximum TOX reductions occurring in the samples with ultrasonic horn pretreatment. A toxicity index was calculated by weighting and summing the levels of total organic chlorine, total organic bromine and total organic iodine in each treated sample. The calculated toxicity index values of the chlorinated wastewater effluent samples followed a descending rank order of “chlorination” > “chlorination+USH” > “chlorination–USH” > “USH–chlorination”, with the lowest toxicity occurring in the samples with ultrasonic horn pretreatment. Then, a developmental toxicity bioassay was conducted for each treated sample. The measured toxicity index values of the chlorinated wastewater samples followed the same descending rank order.

Nano sulfated zirconia over silica for highly effective nano sulfated zirconia

Sulfated zirconia over silica core (NSZS) was synthesised using an ultrasonic-irradiated sol-gel media in which zirconia nanoparticles were distributed on a silica core created by applying ultrasonic irradiation to the sol-gel medium. In order to produce a highly effective catalyst, it is important to have a high surface-to-volume ratio, which the synthesised core-shell catalytic system fully meets. An ultrasonic titanium horn in a sonochemical glass reactor was used for the synthesis. The generated catalyst's crystalline size was 8 nm using this procedure. XRD, N2 Physiosorption, TG-DTA, FTIR, and SEM were used to analyse the produced catalysts. Isobutane alkylation with butene-1 catalysed at 98 percent efficiency by the catalyst after 26 hours of speed of a person's response. A 94 percent activity level was achieved after four and two rounds of regeneration, respectively. Nanoparticles that are not agglomerated may be formed by ultrasonic irradiation, as shown by the NSZS's properties.

Development of a novel valve-based piezoelectric ultrasonic pump using a Langevin vibrator

In this study, a new principle valve-based piezoelectric ultrasonic pump (VPUP) consisting of a Langevin vibrator, compound ultrasonic horn (CUH) and valve was designed, fabricated and tested. The Langevin vibrator and CUH are cylindrical structures with a through-hole, which serves as a flow channel and a chamber. The valve is made of titanium alloy and fabricated by femtosecond laser direct writing technology. It has two types of cross-sectional shapes: bridge type (Valve-1) and double-bridge type (Valve-2). A model diagram of the pumping principle of the VPUP illustrates that the pumping principle is divided into two processes: stepping and dripping. Liquid shear and surface tension play important roles in liquid transport. In this study, the dripping process of liquid was filmed. Two VPUP prototypes respectively equipped with Valve-1 (VPUP-1) and Valve-2 (VPUP-2) were fabricated. Experimental results showed that the flow rate of VPUP-2 was about 125% of that of VPUP-1, which verified the correctness of the Valve-2 for more favourable stepping and dripping processes. VPUP-2 produced a maximum flow rate of 5.562 ml min−1 under sinusoidal excitation at 440 Vpp and 35.783 kHz.

An analytical approach to design horns and boosters of ultrasonic welding machines

This paper presents a new design approach for two main components of an ultrasonic plastic welding machine, booster and horn, based on an analytical model. The design procedure is developed due to the lack of a comprehensive and precise analytical model for rapid design and analysis of these components. The previous analytical models use the one-dimensional wave equation that causes significant errors in designing components with large lateral dimensions. Three-dimensional vibrations are considered for developing an analytical model using the apparent elasticity method. In this way, longitudinal frequency equations are coupled with radial frequency equations by mechanical coupling coefficients. Also, the damping of materials is taken into account. The model can be adapted to calculate the resonant length of the components or calculate the resonant frequency. To verify the model, the results are compared to a numerical simulation. The difference between analytical and numerical resonance frequency is less than 0.02%. Moreover, an experimental modal analysis is performed, which shows 0.9% error with analytical results.Article highlightsA new design approach for boosters and horns has been developed based on an analytical model.Three-dimensional vibrations are considered in the model using the apparent elasticity method.The accuracy of calculating resonant frequencies is more than one-dimensional design method.

Ultrasonic irradiation of nanoporous Au

We investigated the effects of ultrasonic irradiation (UI) on nanoporous (NP) Au structures fabricated by dealloying. To this aim, we leaned an ultrasonic horn against the sample surface and carried out experiments at different temperature. We found that UI induces coarsening, analogously to the process driven by annealing.

Sonoactivated polycrystalline Ni electrodes for alkaline oxygen evolution reaction

The development of cost-effective and active water-splitting electrocatalysts is an essential step toward the realization of sustainable energy. Its success requires an intensive improvement in the kinetics of the anodic half-reaction of the oxygen evolution reaction (OER), which determines the overall system efficiency to a large extent. In this work, we designed a facile and one-route strategy to activate the surface of metallic nickel (Ni) for the OER in alkaline media by ultrasound (24 kHz, 44 W, 60% acoustic amplitude, ultrasonic horn). Sonoactivated Ni showed enhanced OER activity with a much lower potential at + 10 mA cm−2 of + 1.594 V vs. RHE after 30 min ultrasonic treatment compared to + 1.617 V vs. RHE before ultrasonication. In addition, lower charge transfer resistance of 11.1 Ω was observed for sonoactivated Ni as compared to 98.5 Ω for non-sonoactivated Ni. In our conditions, ultrasound did not greatly affect the electrochemical surface area (Aecsa) and Tafel slopes however, the enhancement of OER activity can be due to the formation of free OH• radicals resulting from cavitation bubbles collapsing at the electrode/electrolyte interface.

Acoustic Processing of Fluidic Samples for Planetary Exploration

The search for life on other planetary bodies is driven by our quest to determine if Earth is unique with respect to harboring life. In order to answer this question, instrumentation with suitable sensitivity is required to measure biosignatures. In addition to accurate measurements by in-situ instruments, specialized sample acquisition and sample handling hardware is required to maximize the scientific information obtained from an acquired sample. This paper discusses a class of compact sample processing instrumentation using solid-state mechanisms that use acoustic waves to process samples prior to delivery to the instrument. Some of the acoustic sample processes that can be used to aid in preparation of liquid and liquid/solid mixtures include: mixing, milling, cavitating, lysing, heating, streaming, stirring, lofting, concentrating, segregating, and filtering. We will review these acoustic processes and show how they are generated using electromechanical systems. In addition to processing, these transduction systems could also use acoustics to interrogate physical properties such as the state of the sample, the acoustic velocity, and its attenuation. In order to generate these processes and sensing capabilities at these frequencies, a transduction mechanism is required to produce stress waves from electrical signals and vice versa. One commonly used technique is to use piezoelectric transducers that generate a stress that is linearly proportional to the voltage across the transducer and a voltage that is proportional to the stress on a transducer’s face. A variety of transducer modes are available to excite the sample, including thickness, transverse, radial, and shear extensional, and these can be used to build composite resonance structures including ultrasonic horns, tuning forks, bimorph, and unimorph benders to increase stress generated in the sample. We discuss how to model the acoustic interactions with the sample and the sample chamber in order to produce the required stress waves and illustrate the use of network models of piezoelectric transducers to accomplish this modeling. We demonstrate how to build up these models using Mason’s equivalent circuit for a piezoelectric and network models for acoustic layers in a design. Finally, to illustrate this acoustic processing ability, we will discuss a few systems that we have developed for sample handling systems for other planetary bodies like Mars and ocean worlds Enceladus and Europa.