Liquid Cavity Research Articles

Highly-sensitive fiber-optic F-P salinity sensor based on vernier effect

A new reflective fiber-optic Fabry-Perot (F-P) salinity sensor is proposed with a section of open liquid cavity, which ensures that the seawater flows in and out freely, and the seawater can directly participate in optical transmission. Variation of seawater salinity will cause change of the effective refractive index in the optical path, which in turn affects the output spectrum. By controlling the length of the spliced fiber to form a reflection spectrum with Vernier effect, the sensitivity of the sensor to salinity changes is greatly improved. The results show that the sensor can reach a salinity sensitivity of 2.50883 nm/‰ (11511.07 nm/RIU) in the salinity range of 0 ‰–26.15 ‰, which is approximately 13.17 times higher than that of the sensor without combining Vernier effect. The sensor has good robustness, high sensitivity, and is easy to fabricate to package, which can be applied in the marine monitoring field.

Study on Single Crystal Holmhertz Underwater Acoustic Transducer

According to the theoretical calculation and finite element simulation, a Holm-Hertz transducer is designed. When the resonant frequency of the outer liquid cavity of the transducer is consistent with the resonant frequency of the piezoelectric ceramic stack, the maximum transmit voltage response(TVR) is obtained. After the electrical material was replaced with a new relaxation ferroelectric single crystal piezoelectric material PIN-PMN-PT, the resonant frequency of the transducer was reduced, and the liquid cavity structure was redesigned. Single crystal, can significantly reduce the resonant frequency of the transducer, while significantly increasing the transmit voltage response.

Flexible Wire Electrode Driving Focus-Tunable Electrowetting Optofluidic Lens

An electrowetting-on-dielectrics (EWOD) liquid lens, based on a flexible wire electrode, is proposed to avoid the defects prone to occur in the large area coating dielectric layer inside the cavity. A liquid lens cavity is formed by winding the flexible conductive wire with a thin dielectric layer (named EWOD wire) along the direction of light transmission in a circular wall uniformly. A tubular double-liquid electrowetting lens with a clear aperture of 7 mm is fabricated to demonstrate the practicality of this fabrication process. It can reach a focal length variation range of (<inline-formula> <tex-math notation="LaTeX">$-\infty $ </tex-math></inline-formula>, &#x2212;30 mm] <inline-formula> <tex-math notation="LaTeX">$\cup $ </tex-math></inline-formula> [69 mm, <inline-formula> <tex-math notation="LaTeX">$+\infty $ </tex-math></inline-formula>) at a voltage of 0&#x2013;190 V_rms and shows the other performance not inferior to those of liquid lenses fabricated by traditional methods. The EWOD wire can be assembled into any shape, performing the potential to produce other optofluidic components.

Magneto-turbulent natural convection and entropy generation analyses in liquid sodium-filled cavity partially heated and cooled from sidewalls with circular blocks

Liquid sodium is a promising candidate working fluid in the new solar system and high-density heat sources in industrial applications. In this study free convective flow, heat transfer, and entropy generation of liquid sodium in a hot square enclosure with 16 and 64 cylindrical solid blocks are studied. The cavity is partially heated and cooled from sidewalls with three different locations of heater and cooler named CONF1–3. The effects of the magnetic field in the form of Hartmann number (Ha = 0 and 100), and flow condition in the form of the Rayleigh number (Ra = 106, and 107) are investigated. For tuning the CFD code primitive parameter, the dimensionless forms of the governing equations are used. The ANSYS Fluent equations solver conjugated with a nondimesionlization scheme are used in the turbulent region due to the behavior of liquid metal. The grid verification and validation tests are carried out to ensure the accuracy of the data. Two correlations for average Nusselt number and entropy generation are proposed to simplify calculations. The results discovered that the average Nusselt number and entropy generation increase with increasing the Rayleigh number for each value of the Hartmann number.

Radial oscillation and translational motion of a gas bubble in a micro-cavity

According to classical nucleation theory, a gas nucleus can grow into a cavitation bubble when the ambient pressure is negative. Here, the growth process of a gas nucleus in a micro-cavity was simplified to two “events”, and the full confinement effect of the surrounding medium of the cavity was considered by including the bulk modulus in the equation of state. The Rayleigh–Plesset-like equation of the cavitation bubble in the cavity was derived to model the radial oscillation and translational motion of the cavitation bubble in the local acoustic field. The numerical results show that the nucleation time of the cavitation bubble is sensitive to the initial position of the gas nucleus. The cavity size affects the duration of the radial oscillation of the cavitation bubble, where the duration is shorter for smaller cavities. The equilibrium radius of a cavitation bubble grown from a gas nucleus increases with increasing size of the cavity. There are two possible types of translational motion: reciprocal motion around the center of the cavity and motion toward the cavity wall. The growth process of gas nuclei into cavitation bubbles is also dependent on the compressibility of the surrounding medium and the magnitude of the negative pressure. Therefore, gas nuclei in a liquid cavity can be excited by acoustic waves to form cavitation bubbles, and the translational motion of the cavitation bubbles can be easily observed owing to the confining influence of the medium outside the cavity.

Machine learning identifies liquids employing a simple fiber-optic tip sensor.

We proposed an extremely simple fiber-optic tip sensor system to identify liquids by combining their corresponding droplet evaporation events with analyses using machine learning techniques. Pendant liquid droplets were suspended from the cleaved endface of a single-mode fiber during the experiment. The optical fiber-droplet interface and the droplet-air interface served as two partial reflectors of an extrinsic Fabry-Perot interferometer (EFPI) with a liquid droplet cavity. As the liquid pendant droplet evaporated, its length diminished. A light source can be used to observe the effective change in the net reflectivity of the optical fiber sensor system by observing the resulting optical interference phenomenon of the reflected waves. Using a single-wavelength probing light source, the entire evaporation event of the liquid droplet was precisely captured. The measured time transient response from the fiber-optic tip sensor to an evaporation event of a liquid droplet of interest was then transformed into image data using a continuous wavelet transform. The obtained image data was used to fine-tune pre-trained convolution neural networks (CNNs) for the given task. The results demonstrated that machine learning-based classification methods achieved greater than 98% accuracy in classifying different liquids based on their corresponding droplet evaporation processes, measured by the fiber-optic tip sensor.

Critically coupled Fabry\u2013Perot cavity with high signal contrast for refractive index sensing

Perfect absorption at a resonance wavelength and extremely low absorption at the wavelength range of off-resonance in a one-port optical cavity is required for refractive index (RI) sensing with high signal contrast. Here, we propose and analyze an absorption-enhanced Fabry–Perot (MAFP) cavity based on a critical coupling condition in a near-infrared wavelength range. For a one-port cavity, a thick bottom Au is used as a mirror and an absorber. To achieve the critical coupling condition, a top dielectric metasurface is employed and tailored to balance the radiation coupling and the absorption coupling rates, and the one-port cavity is theoretically analyzed using temporal coupled-mode theory. We investigate two types of MAFP structures for gas and liquid. The gas MAFP cavity shows a sensitivity of ~ 1388 nm/RIU and a full-width at half-maximum of less than 0.7 nm. This MAFP cavity resolves the RI change of 5 × 10−4 with a reflectance signal margin of 50% and achieves a signal contrast of ~ 100%. The liquid MAFP cavity shows a sensitivity of ~ 996 nm/RIU when RI of liquid changes from 1.30 to 1.38. With tailoring the period of the metasurface maintaining its thickness, a signal contrast of ~ 100% is achieved for each specific RI range.

Mechanism of Electromagnetic Field in the Sub-RapidSolidification of High-Strength Al-Cu-Li Alloy Produced by Twin-Roll Casting

In this work, a Al-Cu-Li alloy plate with outstanding mechanical properties was successfully prepared with electromagnetic twin-roll casting (TRC) technology. The microstructure of Al-Cu-Li alloy manufactured by conventional mold casting, TRC, and electromagnetic TRC was studied in detail. The action mechanism of electromagnetic oscillation field (EOF) in the TRC process was studied by systematic experimental characterization and numerical simulation. The results show that the EOF will enlarge the circumfluence area in the cast-rolling zone, accelerate the mass transfer and heat transfer in the molten pool, and make the solute field and flow field in the liquid cavity tend to be evenly distributed. Further, the introduction of the EOF will produce the electromagnetic body force F with the maximum strength of 14 N/m3. The F acting on the solidification front will eliminate the accumulation and deposition of Cu2+, Li+, Mg2+, Zn2+, Mn2+ at the dendrite tip and inhibit the growth of dendrites. At the same time, the F can refine the microstructure of the TRC plate, promote the formation of equiaxed crystals, improve the supersaturated solid solubility of solute elements in the α(Al) matrix, and avoid the appearance of obvious solute segregation area or the formation of excessive solute enrichment area. Therefore, the macro-segregation in TRC plate was significantly reduced, the solidification structure was dramatically refined, and the comprehensive properties of the alloy were remarkably improved.

Phononic-fluidic cavity sensors for high-resolution measurement of concentration and speed of sound in liquid solutions and mixtures

A phononic-fluidic cavity sensor is a new type of acoustic fluid sensor to measure volumetric liquid properties. In our work, it consists of solid-air 3D phononic crystal (PnC) layers confining a fluidic cavity resonator to generate a strong, well separated cavity resonance within the phononic band gap. This allows for the measurement of changes in speed of sound of a liquid analyte with very high, linear sensitivity. In this work, we present theoretical and experimental results for very sensitive determination of sodium chloride and glucose concentrations in aqueous solutions. The 3D-printed measurement cell consists of a rectangular liquid chamber surrounded by an optimized PnC with a simple cubic ball and beam design acting as a metamaterial combining Bragg and local resonance scattering to create optimal boundary conditions for the liquid cavity resonator. Analytical transmission line modeling is used to illustrate the working principle of the sensor. Numerical finite element models describe the phononic band structure and transmission behavior, as well as the frequency response of the sensor element at different mass fractions of the sample solutions as validation for our experiments. A high sensitivity of concentration and subsequently speed of sound is demonstrated over a very large concentration range of 0%–30%.

Photonic Berry curvature in double liquid crystal microcavities with broken inversion symmetry

We investigate a photonic device consisting of two coupled optical cavities possessing Rashba-Dresselhaus spin-orbit coupling, TE-TM splitting, and linear polarization splitting that opens a tunable energy gap at the diabolic points of the photon dispersion; giving rise to an actively addressable local Berry curvature. The proposed architecture stems from recent advancements in the design of artificial photonic gauge fields in liquid crystal cavities [K. Rechci\ifmmode \acute{n}\else \'{n}\fi{}ska et al., Science 366, 727 (2019)]. Our study opens perspectives for topological photonics, room-temperature spinoptronics, and studies on the quantum geometrical structure of photonic bands in extreme settings.

Dynamics of bubbles in spherical liquid cavity wrapped by elastic medium

The cavitation effects occur in the ultrasound therapy technology. With the development of ultrasound therapy technology, cavitation effect in biological tissues has attracted more and more attention. The aim of the present study is to discuss the factors affecting cavitation nucleation and dynamics in tissues, and to provide a theoretical reference for the application of cavitation effects to ultrasound therapy. A model is developed for the cavitation inception in a spherical liquid cavity wrapped by an elastic medium. The Blake threshold value and the critical radius of the liquid cavity for the generation of spherical bubbles are obtained by the pressure equilibrium relationship. The effects of the excitation frequency, the volume modulus of the medium and the volume of the liquid in the cavity on the bubble vibration behavior are analyzed by deriving a bubble dynamic equation that consider the elastic effect of the medium outside the cavity using Lagrange equation. It is shown that the volume modulus, initial radius of bubble nucleus and surface tension can affect the Blake threshold pressure and bubble size, and those form a parameter reference for the control conditions that trigger or inhibit cavitation. The gas core can rapidly grow to a new equilibrium radius and oscillate under the action of an acoustic wave, and the bubble equilibrium radius is independent of the external field, but it can affect the bubble dynamic behavior. When the frequency of the ultrasonic signal is equal to the natural oscillation frequency of the bubble, the bubble collapses after several periods of intense vibration, and the pressure fluctuation in the liquid in the cavity is obvious. The response of bubbles under high frequency ultrasonic driving is relatively weak, and the oscillations of bubbles are dominated by free oscillation.

Liquid crystal tunable vertical cavity surface emission laser with inner cavity sub-wavelength grating

With the rapid development of information technology, a wavelength-tunable vertical cavity surface emitting laser (VCSEL) is urgently needed as an optical signal source in dense wavelength division multiplexing (DWDM). Liquid crystal tunable VCSEL realized by utilizing the birefringence characteristics of liquid crystal has the advantages of stable polarization, high reliability, continuous wavelength tuning. In this paper, a liquid crystal tunable VCSEL structure based on intracavity sub wavelength grating is designed, and the influence of liquid crystal layer and sub wavelength grating on the wavelength tuning characteristics of VCSEL are analyzed and studied in depth. The results show that the thickness of the liquid crystal layer in the tunable VCSEL structure not only affects the wavelength tuning range, but also determines the mode hopping in the tuning process. In addition, an effective refractive index antireflection layer is formed by designing the subwavelength grating structure, and the refractive index difference between the liquid crystal layer and the semiconductor layer is optimized to further improve the wavelength tuning range and tuning efficiency. When the center wavelength is 980 nm, the tuning range is increased by 42%, reaching 41 nm, and the wavelength tuning efficiency is increased by 41%. It provides a new method of designing the VCSEL laser with high beam quality and continuous wavelength tuning.

Dynamic analysis of bubble in liquid cavity wrapped by viscoelastic medium

Ultrasonic wave with higher intensity will directly cavitate in soft tissue. It is an important issue in ultrasonic therapy that the cavitation bubbles in soft tissues are driven in the ultrasonic field. It is assumed that the medium inside the bubble is gas, the cavity is filled with the incompressible viscous liquid, and the medium surrounding the cavity is viscoelastic solid. To introduce the effect of the surrounding tissue, it is assumed that the tissue is incompressible, linear and Voigt viscoelastic solid. The motion of a cavitation bubble can be affected by many factors, such as acoustic pressure, acoustic frequency, tissue elasticity and cavity size. Numerical simulation shows that the resonance frequency and amplitude of the bubbles decrease with cavity radius decreasing. It is also shown that the amplitude of the radial motion for bubbles decreases with the increase of the tissue shear modulus and the frequency, when the ratio of bubble radius to the cavity radius is constant. The effect of the elasticity is very obvious, which reduces the amplitude greatly. The effect of elasticity will be less when the driving pressure is strong. It is found that the inertial cavitation threshold of bubble is relatively low in a range of 1–5 μm. The inertial cavitation threshold of bubble increases with the increase of shear modulus and driving frequency. The smaller the cavity radius, the higher the inertial cavitation threshold of the bubble is. This report aims to provide a firm theoretical basis for the future study of bubbles in a liquid-filled cavity surrounded by a viscoelasticity tissue.

Deformable Liquid Metal Patch Antenna for Air Pressure Detection

For the first time, a deformable liquid metal patch, which is loaded with an air cavity underneath, is proposed for designing an air pressure-detecting antenna. Both the liquid metal (EGaIn) and air cavity of the antenna structure are constructed inside a soft and deformable polydimethylsiloxane (PDMS) substrate. Since liquid metal is highly dense, a PDMS pillar is tactfully embedded into the air cavity region for supporting the liquid patch. Due to the use of such structural support, the liquid metal patch can now be made into one whole piece and it does not cause the antenna structure to collapse. The proposed antenna structure does not require the use of microfluidic channels, which usually compromise the radiation performances, for designing the liquid metal patch. As a result, it is able to attain a high antenna gain of 8.02 dBi. The existence of the air cavity has been proven to be crucial for making the antenna structure deformable so that it is useable for detecting ambient air pressure.

1550 nm infrared/visible light switchable liquid optical switch.

In this paper, a liquid optical switch is proposed, and the 1550 nm infrared/visible switching function based on hydraulic control can be realized. An infrared light switch cavity, a visible light cavity and a liquid control cavity are stacked to form the main framework of the device. The glycerol, dyed liquid, and transparent liquid are filled in the cavities, respectively. Two elastic films are fabricated between the cavities for controlling the liquid volume of the cavities. With such a structure, in the initial state, the 1550 nm infrared light and visible light are absorbed by the glycerol and dyed liquid, respectively. The device shows infrared light-off and visible light-off states. When the elastic film is actuated by the liquid pressure, the shape of the elastic film can be changed. Once the elastic film touches to the substrate, a light channel can be formed so that the infrared light or visible light can pass through it. It shows infrared light-on or visible light-on states. In this way, the device can be worked as an infrared light and visible light switchable optical switch. The experiments show that the device can obtain the optical attenuation from ∼1.02 dB to ∼18.24 dB for 1550 nm infrared light optical switch and ∼0.66 dB to ∼8.70 dB @ λ=450 nm; ∼0.62 dB to ∼8.74 dB @ λ=532 nm; ∼0.77 dB to ∼9.00 dB @ λ=633 nm for visible light optical switch. The device has potential applications in the fields of optical fiber communications, variable optical attenuators, and light shutters.

Interaction between bubble and particle in spherical liquid cavity surround by an elastic medium

A theory is developed to model the dynamic of bubble and particle inside a spherical liquid-filled cavity surrounded by an elastic medium. The aim of this work is to study how the outer elastic medium affects the interaction between bubble and particle. Starting from the theory of velocity potential distribution, combined with Lagrangian equations, the motion equations of bubbles and particles in the cavity are obtained. The resonance frequency of the bubbles and influence of the interaction between particle and bubble on the translational behavior under the action of sound waves are analyzed. The results show that the properties of medium elasticity and density can change the resonance frequency of the bubble in the cavity. As the radius of the spherical cavity increases, the resonance frequency of the bubble has a tendency to first decrease and then increase, and gradually tends to the resonance frequency of a single bubble in an unbounded liquid. The translation of bubble and particle in the spherical liquid cavity is affected by factors such as acoustic field parameters, the characteristics of the outer elastic medium, and the characteristics of the bubble and particle themselves. The overall characteristic is that the particle has a tendency to move to the cavity wall, and the translation of bubble is closely related to the interaction characteristics between bubble and particle.

Multifunction reflector controlled by liquid piston for optical switch and beam steering.

This paper presents a multifunction reflector controlled by liquid piston for optical switch and beam steering. The multifunction reflector consists of two liquid cavities that are designed with microchannels. Two holes covered with elastic membranes are fabricated on the upper surface of the liquid cavities. When the liquid cavity is injected with liquid, the shape of the elastic membrane changes to form a liquid piston in the position of the holes accordingly. The magnetic base covered with a reflector is fixed on the surface. We can adjust the active number and height of the liquid pistons to drive the reflector deflecting to different directions. Our experiments show that the multifunction reflector can realize the function of 2×2 optical switch. It can also deflect the light beam through an angle of 0°∼72° in two directions. The multifunction reflector has potential applications of free-space optical communications, laser detections and variable optical attenuators.

The Use of Carnoy’s Solution and Its Modifications for Reducing the Number of Recurrences after Surgical Removal of Keratocystic Odontogenic Tumors and Ameloblastomas: A Systematic Review

The paper is a systematic review of using the pharmaceutical substance, Carnoy’s solution, to reduce the number of recurrences of such tumors as keratocystic odontogenic tumor and ameloblastoma. These are benign yet aggressive jaw tumors with a high percentage of recurrences (up to 60–80%). Surgical treatment of the above-described lesions can be performed using: (1) marsupialization (recurrence rate up to 24.8%); (2) enucleation with or without adjunct therapy; therapy may include cryotherapy with liquid nitrogen (recurrence rate up to 23.1%), peripheral ostectomy (recurrence rate up to 20%), and bone cavity treatment with Carnoy’s solution (recurrence rate up to 6.6%); (3) marginal/segmental resection of the jaw (recurrence rate up to 2.5%). Despite the low percentage of recurrences when using marginal/segmental resection, this method requires a longer and more expensive anesthetic and surgical intervention as well as longer postoperative and rehabilitation periods. With the use of Carnoy’s solution, it became possible to reduce the risks of recurrence of keratocystic odontogenic tumors and ameloblastomas from 60–80 to 6.6‒11.5%. Worldwide today, not only Carnoy’s solution recommended by Cutler and Zollinger in 1933 is applied but also its modifications that are not inferior to the original substance in terms of removal efficiency of the remaining cystic cells. The safety of the use of the solution near the vessels and nerves is confirmed by works of a number of authors. It is concluded that, despite the large number of surgical treatments of both keratocystic odontogenic tumors and ameloblastomas, enucleation with the use of Carnoy’s solution is the optimal method of choice for these diseases.

Effects of electromagnetic field on physical behaviors during low-frequency electromagnetic casting of Mg alloy AZ31

A numerical model was established for the simulation of the multiple physics fields during the low-frequency electromagnetic casting (LFEC) process of AZ31 alloy by using ANSYS (FE commercial package) and FLUENT (finite volume package). The electromagnetic field was calculated in the former and the latter was aimed at analyzing the fluid flow driven by magnetic, heat transfer and solidification. Overall physical parameters, including magnetic flux density, Lorentz force, flowing velocity, temperature field and liquid cave feature were discussed. Results show that the electromagnetic field can significantly affect the flow field and temperature field of the melt during the LFEC process of AZ31 alloy by inducing the effect of Lorentz force. Different electromagnetic frequencies have different effects. In the experimental frequency range of 5 ∼ 35 Hz, a higher frequency can intensify the flowing of the melt near the cooled wall of the crystallizer, resulting in an increase in heat transfer intensity and further a decrease in liquid cavity depth.

Two-Stream Numerical Simulation of a New Type Drum Dryer

In recent years, the new type of tumble waste dryer has been promoted and developed. Heat generation through phase transition is an environmental, friendly and efficient heat transfer drying method. In order to know under what conditions the water vapor has higher heat transfer efficiency in the semi-circular cylinder and more sufficient liquid phase transition, and under what conditions the quantity of heat transferred can be exactly controlled, we carried out relevant work. Based on the analysis of two-phase heat transfer of rotating body, a three-dimension model of garbage dryer is established. Then, the commercial CFD software ANSYS Fluent is used to simulate the two-phase flow in the semi-circular cylinder, and the simulation calculation is carried out. Finally, the theoretical calculation results are verified by experiments. Calculated by the simulation results analysis: according to the industrial use of setting conditions, simulation calculation results can achieve convergence, namely water vapor through the pipe wall heat conduction. Finally condense into liquid water, and to ensure that the liquid cavity in the body has a higher volume fraction, water vapor phase change rate is of more than 90%, the Nusselt number of the heat transfer surface is 60 to 300.