Capillary Vibration Research Articles

Impact of a nanodroplet on liquid surfaces

The present study investigates impact of nanodroplets on liquid films with varied film thicknesses over hydrophilic to hydrophobic surfaces via molecular dynamics simulations. A new crown pattern, hollow crown, is observed on medium liquid films for nanodroplets, whereas it is not reported for millimeter-sized droplets. Holes (or hollows) are attributed to capillary vibration of a nanometer-thick liquid film. The occurrence of holes is inhibited effectively for deep liquid films because the cavity thickness is much larger than the amplitude of capillary vibration. Surface wettability has a significant influence on thin and medium liquid films for nanodroplets, whereas it only affects thin liquid films for macrodroplets because the range of solid–liquid intermolecular forces is comparable to the size of droplets when the size of droplets reduces to the nanoscale. Subsequently, the accuracies of the existing macroscale models for predicting the time-dependent crown radius of nanodroplets are tested by simulated results. The results show that the macroscale models cannot capture the time-dependent crown radius of nanodroplets. On the basis of energetics analysis, we prove that the failure of macroscale models is attributed to the distinct difference in viscous dissipation mechanisms between macroscale and nanoscale droplets.

Generation of Surface Liquid Flow in Channels by Capillary Vibrations and Waves

Generation of Surface Liquid Flow in Channels by Capillary Vibrations and Waves

Light Metal Alloys Local Reactivity, from AFM Based Scanning Kelvin Probe Force Microscopy (AFM-SKPFM) to Scanning Electrochemical Nanocapillary (SEN)

Materials surface heterogeneities obviously plays a crucial role in reactivity issues and generate various types of detrimental localized corrosion attacks. In corrosion science, a first question to be addressed is how these various materials microstructure affect oxidation / passivation and localized corrosion initiation mechanisms. A methodology for microscale characterization of initial stage of surface reactions has been developed based on the Atomic Force Microscopy (AFM) Scanning Kelvin Probe Force Microscopy (AFM-SKPFM). In very early work, potential mapping with micrometer lateral resolution (lateral detection limit of materials surface heterogeneities is better but the signal has to be deconvoluted) allowed to clearly identify "cathodic" and anodic sites on Al- alloys [1]. Careful potential calibration and surface conditioning with solution exposure generating the formation of an electrochemical double layer allow obtaining local thermodynamic information closely linked to "practical electrochemical potential series" measured in bulk solution conditions. This contribution will start by revisiting some "historical" examples of AFM-SKPFM characterization (a tribute to Jerry Frankel's activities) of aluminum and magnesium alloys [1,2]. These materials surfaces will further be used to show how reaction kinetic information on corrosion processes can be obtained with similar lateral resolution by means of the newly developed Scanning Electrochemical Nanocapillary (SEN) technique. After introducing the SEN technique and methodology, the presentation will focus on showing how the combination of these two approaches allows refining the local corrosion mechanism assessment of heterogeneous materials. The SEN technique is very versatile and allows various types of electrochemical measurements to be performed with constant tracking of the topography. The technique is based on a nanocapillary glass tip (< 100 nm) excited laterally by a piezoelectric element. A control of the capillary vibration damping when approaching the surface and a feedback loop (like the tapping mode in AFM) allows a very precise control of the approach and electrolyte contact on the surface. The glass capillary filled with the electrolyte of interest integrates a reference and Pt counter electrodes to perform electrochemical measurements exposing only the area of interest to aggressive electrolytes. Using its "hopping" mode (a scan with electrochemical characterization of successive individual nanoscale areas), corrosion initiation susceptibility can be addressed. This will be illustrated through the surface reactivity study of model Al-Cu-Mg microscale intermetallics and Mg-based alloys, using SEN OCP linescans. In addition information about extend of the attack can be subsequently retrieved from SEM observations. Using the precise positioning ability of the SEN setup with X, Y and Z direction piezos, potentiodynamic polarization measurements can furthermore be performed on selected area of interest. The example of an Mg-Fe composite material will be used to discuss its local electrochemical behavior.After the presentation of the SEN characterization results, additional aspects of the measured potential by AFM-SKPFM will also be discussed as adsorbed species, especially strong dipolar molecules, can significantly contribute to the measured signal [3]. Modification of the AFM-SKPFM setup towards atmospheric corrosion investigation will finally be presented. This environmental AFM/SKPFM bridges the gap between the full electrochemical local characterizations that can be offered by the SEN technique and an "electrochemical reaction" diagnostic obtained by SKPFM in thin water layer. The example of a very reactive WC-Co composite will be presented to demonstrate the reactivity issue, galvanic coupling controlling local dissolution processes [4].AcknowledgementsGerald Frankel for the great time I spent at Ohio State University in the Fontana Corrosion Center developing the AFM-based SKPFM methodology. Empa for internal project financial support of the SEN instrument.

Keyhole-induced Porosity in Laser Manufacturing Processes: Formation Mechanism and Dependence on Scan Speed

Laser welding and laser-based powder-bed fusion additive manufacturing in the deep penetration (keyhole) mode are promising technologies for the synthesis of metal components. The significant potential of these technologies remains latent because of structural defects (porosity), which significantly degrade the structural integrity and performance of the end products. Practical strategies for reducing those defects are addressed through fundamental understanding of their formation. In this study, pore formation of hydrodynamic origin is investigated, including the dynamics and mechanisms of the formation based on the above mentioned technologies. The pore volume and frequency of pore appearance, depending on the amplitude and frequency of capillary vibrations, are considered. Physical analysis is performed to obtain the scanning velocity values for the maximum and zero amplitudes and the frequency of capillary waves. A comparison between calculated curves and experimental data confirms both the capillary origin of the pores and the estimated scanning speeds at which the parameters of the pores exhibit their maximum values or vanish. The results obtained may facilitate in the selection of the optimal scanning speed when designing a pore-free technology.

Spectrally tunable liquid resonator based on electrowetting.

We present a tunable on-chip liquid resonator in conjunction with a tapered fiber coupling scheme. The resonator consists of a glycerol droplet submerged within an immiscible liquid bath, which mitigates the effects of environmental fluctuations. The platform is fabricated using standard semiconductor techniques, which enable the future integration of photonic components for an on-chip liquid resonator device. The liquid resonator maintains its high Q-factor on chip (105) due to surface tension forming an atomically smooth liquid-liquid interface. Higher Q-factor resonance modes experienced linewidth broadening due to the random excitation of thermal capillary vibrations. Spectral tuning is demonstrated using the electrowetting effect, increasing the surface's wettability and an expansion in the droplet diameter. A maximum spectral tuning of 1.44 nm ± 5 pm is observed by applying 35 V. The tuning range is twice the free spectral range (FSR) of 0.679 nm measured at a pumping wavelength range of 770-775 nm. A 2D axisymmetric finite-element simulation shows resonance modes in good agreement with experimentally measured spectra and with predicted tuning speeds of 20 nm/s.

Capillary-wave warp-drive

The generation of surface water flow in channels with sources and resonators of capillary oscillations is detected and investigated. Moving devices with a capillary-wave accelerator of the surface fluid flow are demonstrated. The surface flow of liquid in the channel is generated due to the local deformation of the liquid surface by capillary vibrations and the formation of an excess liquid surface on average near the source and the transport of this surface by waves. Keywords: capillary oscillations and waves, surface liquid flow, channel.

Generation of surface liquid flow in channels by capillary vibrations and waves

The generation of a directed flow on the water surface in channels with sources and resonators of capillary oscillations is detected and investigated. The surface flow is caused by the movement of the liquid through the gaps between the resonators, as well as between the resonator and the channel walls, under a curved surface that is locally deformed by the sources of capillary vibrations, the transfer of energy of the locally curved surface of the liquid by capillary waves, and the transmission of wave momentum to the particles of the liquid surface in one direction. It is shown that capillary waves together with the energy transfer an excess surface, the flux density of which is equal to the flux of the surface deformation. Moving devices with a capillary-wave accelerator of the surface liquid flow are demonstrated. Keywords: capillary oscillations and waves, surface liquid flow, channel, flux of surface deformation.

Генерация поверхностного потока жидкости в каналах капиллярными колебаниями и волнами

The generation of a directed flow on the water surface in channels with sources and resonators of capillary oscillations is detected and investigated. The surface flow is caused by the movement of the liquid through the gaps between the resonators, as well as between the resonator and the channel walls, under a curved surface that is locally deformed by the sources of capillary vibrations, the transfer of energy of the locally curved surface of the liquid by capillary waves, and the transmission of wave momentum to the particles of the liquid surface in one direction. It is shown that capillary waves together with the energy transfer an excess surface, the flux density of which is equal to the flux of the surface deformation. Moving devices with a capillary-wave accelerator of the surface liquid flow are demonstrated.

Капиллярно-волновой варп-двигатель

The generation of surface water flow in channels with sources and resonators of capillary oscillations is detected and investigated. Moving devices with a capillary-wave accelerator of the surface fluid flow are demonstrated. The surface flow of liquid in the channel is generated due to the local deformation of the liquid surface by capillary vibrations and the formation of an excess liquid surface on average near the source and the transport of this surface by waves.

Low frequency of a deforming capillary vibration, part 1: Mathematical model

The capillary effect has wide applications from biology and textile engineering to nanotechnology especially the micro-electromechanical systems and microfluidics device. The capillary vibration si...

Electrochemical Motion Tracking of Microorganisms Using a Large‐Scale‐Integration‐Based Amperometric Device

AbstractMotion tracking of microorganisms is useful to investigate the effects of chemical or physical stimulation on their biological functions. Herein, we describe a novel electrochemical imaging method for motion tracking of microorganisms using a large‐scale integration (LSI)‐based amperometric device. The device consists of 400 electrochemical sensors with a pitch of 250 μm. A convection flow caused by the motion of microorganisms supplies redox species to the sensors and increases their electrochemical responses. Thus, the flow is converted to electrochemical signals, enabling the electrochemical motion tracking of the microorganisms. As a proof of concept, capillary vibration was monitored. Finally, the method was applied to monitoring the motion of Daphnia magna. The motions of these microorganisms were clearly tracked based on the electrochemical oxidation of [Fe(CN)6]4− and reduction of O2.

Electrochemical Motion Tracking of Microorganisms Using a Large-Scale-Integration-Based Amperometric Device.

Motion tracking of microorganisms is useful to investigate the effects of chemical or physical stimulation on their biological functions. Herein, we describe a novel electrochemical imaging method for motion tracking of microorganisms using a large-scale integration (LSI)-based amperometric device. The device consists of 400 electrochemical sensors with a pitch of 250 μm. A convection flow caused by the motion of microorganisms supplies redox species to the sensors and increases their electrochemical responses. Thus, the flow is converted to electrochemical signals, enabling the electrochemical motion tracking of the microorganisms. As a proof of concept, capillary vibration was monitored. Finally, the method was applied to monitoring the motion of Daphnia magna. The motions of these microorganisms were clearly tracked based on the electrochemical oxidation of [Fe(CN)6 ]4- and reduction of O2 .

Ultrasonic Vibration in Leadframe for the Bondability for Au Wedge Bond

The in-situ inspection of ultrasonic vibration of wire bonder capillary was carried out using laser interferometer in order to analyze the formation of Au wedge bond. It was observed that the changes in ultrasonic vibration can be used to describe process of bonding formation. The loss of ultrasonic energy was exhibited in ultrasonic vibration waveform of wire bonding on leadframe A. This observation is due to the low frictional energy and high deformation of Au wedge bond on leadframe A. The lower pull strength obtained by Au wedge bond further confirms the reduction of bond formation on leadframe A.

와이어 본딩용 초음파 혼의 진동 특성

본 논문은 상용화된 와이어 본딩용 초음파 혼 시스템에서 발생하는 와이어 본딩 불량의 원인을 진동해석을 통하여 파악하고자 한다. 먼저 링 형상의 압전 구동기와 초음파 혼 그리고 캐필러리 등 각 부품의 진동 특성과 136kH의 가진 주파수 근처에서 발생하는 전체 초음파 혼 시스템의 주요 진동 모드들을 유한요소해석을 이용하여 구하였다. 136kHz에서 공진되는 전체 트랜스듀서 시스템의 진동 모드가 종진동 모드가 아닌 굽힘 진동 모드임을 조화 가진 해석과 실험으로 확인하였다. 136kHz에서 발생하는 굽힘 진동 모드는 캐필러리 끝단의 움직임이 종방향 뿐만 아니라 좌우 횡방향으로도 큰 변위가 발생하기 때문에 정밀 작업 시 본딩 불량의 원인이 될 수 있다. 가진 주파수 대역 근처인 119kHz에서 발생하는 종진동 모드는 캐필러리의 횡방향 진동이 감소하기 때문에 본딩 성능의 향상을 위해서 이러한 종진동 모드를 이용하도록 설계 변경이 필요함을 제시하였다.

Hysteresis Heat Build-up and Low Temperature Processing of Polymer under the Vibration Force Field

By using dynamic capillary and multi-dimensional vibration experiment desktop, isotactic polypropylene ( iPP ) is selected for the objective material to investigate the effect of the vibration parameters on the viscoelastic properties of polymer and its molding process. And a series conclusions can be draw that: The phase angle of polymer tends to decrease after a increase with vibration frequency increasing. The phase angle reach maximum value of 90° when the vibration frequency equals to the material natural frequency. Which polymer experience as pure viscous materials, also hysteresis heat build-up rate goes up to the peak. The plasticizing rate of polymer increase as the vibration amplitude, but the higher requirement for the equipment leveled up as well. The polymer plasticizing rate display the same law with that of phase angle against vibration frequency. When the vibration frequency equals to the material natural frequency, the plasticizing rate reach maximum. The investigation of this study will offers valuable theoretical references for polymer processing and novel equipment design in low-temperature.

Hysteresis thermogenous process of polymer material under vibrational force field

A thorough analysis of the mechanism of vibrational force field on polymer processing was carried out to investigate the effect of vibration parameters on polymer viscoelasticity and plastic forming processing. The relationship between phase angle and lagging heat generation rate as well as the expression of polymer plasticizing rate under vibrational force field was obtained. To verify the theory, PET was adopted for example calculation and in expriments with dynamic capillary rheometer and mlti-dimentional vibration induced plastic forming equimpment. The result from calculation agrees well with that from experiment. Besides, it can be concluded that the plasticizing rate of PET increases at first and decreases afterwards with increasing vibration frequency. It reaches the peak at vibration frequency equivalent to the natural frequency of PET of about 15 Hz. The value remains at 22 g/min with the natural vibration frequency when the vibration amplitude is 6 MPa, being 1.75 fold that with vibration frequency of 10 Hz. Therefore, the plasticizing rate of polymer can be significantly improved by increasing the vibration amplitude. The exploration in this paper supplies reliable thoeretical reference for novel polymer low temperature moulding technique and equipments.

Vibration characteristics of the capillary in ultrasonic wire bonders

Currently ultrasonic wire bonders with precision capillary tips are widely used in the packaging industry for bonding wires to ICs and circuits. However, the quality and strength of a bond are affected significantly by the vibration of the bonding capillary. It is, therefore, necessary to study the vibration characteristics of the capillary for better understanding and for developing a non-perturbative and low-cost monitoring device for improving bonding quality control. In this paper, the vibration characteristics of the capillary are presented in terms of natural frequency and vibration modes using finite-element models. The predicted displacement profile along the capillary is compared with the measurement using a non-contact laser interferometer. In general, a good agreement between the prediction and measurement is obtained, and it shows that the interferometer may be a good monitoring tool for characterization of capillary tip vibration, as well as providing a reference for other monitoring devices.

Nonlinear capillary vibration of a charged bubble in an ideal dielectric liquid

The problem of nonlinear radial pulsations and surface vibrations of a charged bubble placed in an ideal incompressible dielectric liquid is asymptotically solved up to the second order of smallness by the method of many scales. It is shown that, in the case of nonlinear vibrations, resonance energy exchange may take place not only between surface modes but also between the radial mode and a surface mode. A new type of instability (other than Rayleigh instability against the self-charge), instability against the excess vapor pressure in the bubble, is discovered. The new type of instability shows up as energy transfer from the centrosymmetric pulsation mode to all initially excited surface vibration modes simultaneously.

Impact of Geometric Parameters of Capillary Design on Quality of Gold Ball Bonding

0.13μm or smaller critical dimension of integrated circuits has driven the bonding pad pitch down to 50μm or even smaller. It has also had quite an impact on the adhesive force between the bonding pad and the gold ball. This study focuses on the correlation between the capillary geometric parameters (i.e. tip diameter, chamfer diameter, inner chamfer angle, and cone angle) and the bonding quality (i.e. ball size, ball thickness, ball shear force, specific ball shear force, and capillary vibration). An experimental design is utilized and the response is analyzed statistically. The results show that as the tip diameter and ball size increase, the ball thickness decreases, and the ball shear force increases first and then decreases afterward. As the cone angle decreases, the ball size increases, the ball thickness decreases, and the ball shear force increases. Therefore, both tip diameter and cone angle are significant factors that affect the bond quality. The empirical model, i.e. the correlation between the capillary geometric parameters and the bonding quality is also derived, and is quite useful in predicting the bonding pad size or bonding pad pitch required during process development. The predicted values and the experimental results are shown to have good agreement.

On nonlinear resonant four-mode interaction between capillary vibrations of a charged drop

Energy transfer from higher modes of capillary vibrations of an incompressible liquid charged drop to the lowest fundamental mode under four-mode resonance is studied. The resonance appears when the problem of nonlinear axisymmetric capillary vibration of a drop is solved in the third-order approximation in amplitude of the multimode initial deformation of the equilibrium shape of the drop. Although the resonant interaction mentioned above builds up the fundamental mode even in the first order of smallness, its amplitude turns out to be comparable to a quadratic (in small parameter) correction arising from nonresonant nonlinear interaction, since the associated numerical coefficients are small.