Showing papers on "Interdigital transducer published in 2021"

Investigation of Surface Acoustic Wave Propagation Characteristics in New Multilayer Structure: SiO2/IDT/LiNbO3/Diamond/Si.

Abstract: Surface acoustic wave (SAW) devices are widely used in many fields such as mobile communication, phased array radar, and wireless passive sensor systems. With the upgrade of mobile networks, the requirements for the performance of SAW devices have also increased, and high-frequency wideband SAW devices have become an important research topic in communication systems and other application fields. In this paper, a theoretical study for the realization of a layered SAW filter based on a new SiO2/IDT/128°YX-LiNbO3/diamond/silicon layered structure using the modeling software COMSOL Multiphysics is presented. The effects of lithium niobate (LiNbO3), an interdigital transducer (IDT), and SiO2 thin films on the evolution of the phase velocity, electromechanical coupling coefficient (k2), and temperature coefficient of frequency were studied by employing a finite element method simulation. Furthermore, a longitudinal coupling resonator filter was designed. To investigate the SAW characteristics of the filter, a transient analysis was conducted to calculate the electrical potential and particle displacement under the resonance condition and to analyze the frequency response. The study concluded that this new multilayer structure can be applied to design and manufacture a variety of high-frequency and wideband SAW filters with a temperature compensation function, for operation above the GHz range.

A reconfigurable and portable acoustofluidic system based on flexible printed circuit board for the manipulation of microspheres

Abstract: Acoustofluidic devices based on surface acoustic waves (SAWs) have been widely applied in biomedical research for the manipulation and separation of cells. In this work, we develop an accessible manufacturing process to fabricate an acoustofluidic device consisting of a SAW interdigital transducer (IDT) and a polydimethylsiloxane (PDMS) microchannel. The IDT is manufactured using a flexible printed circuit board (FPCB) pre-patterned with interdigital electrodes (IDEs) that is mechanically coupled with a piezoelectric substrate. A new microchannel moulding technique is realised by 3D printing on glass slides and is demonstrated by constructing the microchannel for the acoustofluidic device. The flexible clamping mechanism, used to construct the device, allows the reconfigurable binding between the IDT and the microchannel. This unique construction makes the acoustofluidic device capable of adjusting the angle between the microchannel and the SAW propagation, without refabrication, via either rotating the IDT or the microchannel. The angle adjustment is demonstrated by setting the polystyrene microsphere aggregation angle to -5°, 0°, 6°, and 15°. Acoustic energy density measurements demonstrate the velocity of microsphere aggregation in the device can be accurately controlled by the input power. The manufacturing process has the advantages of reconfigurability and rapid-prototyping to facilitate preparing acoustofluidic devices for wider applications.

Research on the Progress of Interdigital Transducer (IDT) for Structural Damage Monitoring

Abstract: In the application of Structural Health Monitoring (SHM) methods and related technologies, the transducer used for electroacoustic conversion has gradually become a key component of SHM systems because of its unique function of transmitting structural safety information. By comparing and analyzing the health and safety of large-scale structures, the related theories and methods of Structural Health Monitoring (SHM) based on ultrasonic guided waves are studied. The key technologies and research status of the interdigital guided wave transducer arrays which used for structural damage detection are introduced. The application fields of interdigital transducers are summarized. The key technical and scientific problems solved by IDT for Structural Damage Monitoring (SHM) are presented. Finally, the development of IDT technology and this research project are summarised.

Measurement of defects in a plate using dry-coupled interdigital transducer–based scanning laser Doppler vibrometer:

Abstract: The interdigital transducer–based scanning laser Doppler vibrometer has recently been introduced to efficiently generate the symmetric mode for damage detection of shallow defects in thick plates. ...

Additive manufacturing of flexible nanocomposite SAW sensor for strain detection

Abstract: The development of a flexible surface acoustic wave (SAW) sensor as microelectromechanical systems (MEMS) device has been gradually emerged due to its unobtrusive size, passive, and wireless competencies. The concept behind this work is to additively develop a flexible surface acoustic wave (SAW) device with enhanced electromechanical properties capable of detecting mechanical strain occurring in aerospace applications. The nanocomposite substrate is made of polyvinylidene fluoride (PVDF) owing to its flexibility, piezoelectricity, long-term stability, and easy processing incorporated with carbon nanotubes (CNTs) as nanofillers. Adding CNTs to the polymer matrix for electromechanical properties enhancement is investigated through additive manufacturing (AM) process. Both the thin substrate and the interdigital transducer (IDT) are fabricated through direct digital manufacturing (DDM), exhibiting favorable piezoelectric and electrical properties. Various device characteristics of fabricated SAW sensor, including the generation and propagation of Rayleigh waves and the changes in wave characteristics, such as frequency, admittance, and impedance, are discussed in this paper. The effects of IDT dimensions and the resonant frequency response of the developed SAW device are also examined with numerical analysis.

Separation of particles using the focused acoustic sorting chip based on the wettability treatment

Abstract: Combining the focusing energy characteristics of the focused interdigital transducer with the self-cleaning function of the wettability surface, a focused acoustic sorting chip based on the surface wettability treatment is proposed in this work. In the laboratory, two kinds of focused acoustic sorting chips based on the hydrophilic and hydrophobic wall characteristics were designed and fabricated separately. The corresponding separation experiments were carried out using polystyrene microparticles with diameters of 1 and 10 µm. Moreover, the particle adhesion characteristics based on different surface wettability and the effects of average velocity (Va) and input power (P) on particle deflection were investigated. The relevant optimum separation conditions were confirmed, namely under the hydrophilic treatment of the micro-channel surface, when the work frequency (f) was 131.83 MHz, Va = 4 mm/s, and P = 320 mW. Under these conditions, the optimal separation efficiency can reach 99.17%. The proposed chip has the advantages of simple structure, high separation accuracy, self-cleaning, and focusing energy.

2–8 GHz Range High Harmonic SAW Resonator with Grooved Electrodes in LiNbO 3

Abstract: This paper reports simulation and experimental study to strongly excite high harmonic SAW using a grooved interdigital transducer (IDT). The grooved IDT is made by etching LiNbO 3 (LN) and filling the grooves with metal. Simulation was done to find promising designs. Then, SAW resonators with wavelengths (λ) of 5.2 µm and 1.3 µm were fabricated on 26°YX LN using Al for IDTs. Strong excitation of high harmonic SAW was confirmed. The SAW resonator with λ of 1.3 µm generated the 3rd harmonic SAW at 8.1 GHz with an impedance ratio of 32 dB.

Finite element simulation and characterization of one-port heterostructured surface acoustic wave resonator

Abstract: The research work presents the study of a heterostructured surface acoustic wave (SAW) resonator consisting of an interdigital transducer (IDT), lithium niobate (LN), and silicon (Si) substrate. In...

SH 1 Mode Plate Wave Resonator on LiTaO 3 Thin Plate with Phase Velocity over 13,000 m/s

Abstract: In this study, a first shear horizontal mode (SH 1 mode resonator) for high-frequency filters were investigated. From FEM simulation, it was confirmed that the SH 1 mode plate wave had a high phase velocity of 20 km/s and a high electro-mechanical coupling factor (k2) of 14% on (0°, 60°-70°, 0°) LiTaO 3 (LT) with a thickness of 0.1λ (λ: wavelength). The high k2 was achieved by forming an electrically shorted plane on the bottom LT surface (opposite side of an interdigital transducer electrode, IDT). The SH 1 mode plate wave resonator was fabricated on a 0.5 µm thick LT film supported with a Si substrate. The IDT had a λ of 4.5 µm and a thickness of 100 nm (0.02λ). The fabricated SH 1 mode plate wave resonator showed a resonance frequency (f r ) of 2.78 GHz, anti-resonance frequency (f a ) of 2.92 GHz, a bandwidth (BW) of 5%, and an impedance (Z) ratio of 38 dB. The anti-resonant phase velocity was calculated as high as 13,050 m/s, which showed a potential for high frequency filters. The poor impedance ratio was caused by the low mechanical quality factor (Q m ) of Cu IDT used in the fabrication and the not optimized fabrication process.

The Peculiarities of the Acoustic Waves of Zero-Order Focusing in Lithium Niobate Plate.

Abstract: In this research, beam focusing in lithium niobate plate was studied for fundamental anti-symmetric (A0) and symmetric (S0) Lamb waves, and the shear-horizontal (SH0) wave of zero-order. Using the finite element method, appropriate configuration of the interdigital transducer with arc-like electrodes was modeled accounting for the anisotropy of the slowness curves and dispersion of the modes in the plate. Profiles of the focalized acoustic beams generated by the proposed transducer were theoretically analyzed. Based on the result of the analysis, relevant delay lines were fabricated and transfer functions (insertion loss) of the line were measured for SH0 wave in YX-lithium niobate plate. Using an electron scanning microscope, distribution of the electric fields of the same wave were visualized. The results of this study may be useful for hybrid devices and sensors combining nano and acoustoelectronic principles.

The Temperature Coefficients of Frequency of Surface Acoustic Wave Devices With SiO x N y Passivation Films on LiTaO 3 Substrates

Abstract: This work assessed the possible correlation between the refractive index of a SiO x N y passivation film on a surface acoustic wave (SAW) device and the temperature coefficient of frequency (TCF) of the device itself. The data demonstrate that the refractive index does correlate with the TCF as well as the frequency of the one-port resonator. SiO x N y passivation films having an optimal refractive index can potentially suppress the frequency shifts caused by the deposition of such layers, and can change the TCF from that for a Si3N4 film to that for SiO2. The results also show that the coupling coefficient of the one-port resonator increases when using a SiO x N y film with a lower refractive index, which changes the TCF such that this value approaches that for a SiO2 film. Finite-element method spectral domain analyses established that the frequency responses of the one-port resonators were affected by the velocity and temperature coefficient of velocity of the dielectric films deposited on the interdigital transducer electrodes. Thus, adjusting the refractive index of the SiO x N y film can be used to control the properties of an SAW device, including the TCF.

AlN/Pt/LN-Y128 Packageless Acoustic Wave Temperature Sensor

Abstract: Batteryless, wireless, and packageless acoustic wave sensors are particularly desirable for harsh high-temperature environments In this letter, an acoustic wave sensor based on a lithium niobate (Y + 128° cut, abbreviated LN-Y128) substrate with a buried platinum interdigital transducer (IDT) in an aluminum nitride (AlN) overlayer is investigated Previously, it was demonstrated theoretically that due to the specific properties of LN-Y128, Rayleigh-type guided waves can propagate at the AlN/IDT(Pt)/LN-Y128 interface Here, this structure is, for the first time, studied experimentally, including the growth and properties of the AlN layer onto irregular platinum IDTs Both Shear Horizontal and Rayleigh-type waves have been identified after the AlN deposition and the velocities are consistent with the fitted SDA-FEM-SDA (a combination of finite element modeling with spectral domain analysis) simulations Electrical measurements with a surface perturbation and temperature measurements show that the AlN/IDT(Pt)/LN-Y128 bilayer structure is promising as a packageless high-temperature sensor

Direct Monitoring of Battery SOC Utilizing GMI-IDT Magnetic Sensor

Abstract: A novel micromagnetic sensor is designed and optimized for direct and non-invasive measurement of the State of Charge (SOC) (via magnetic properties) of Li-ion batteries. Potential applications include (Hybrid) Electric Vehicles (EV) and other electric battery-driven systems. A single surface acoustic wave (SAW) interdigital transducer (IDT) is used as the sensing platform shunt loaded with amorphous microwires based on Giant Magnetoimpedance (GMI) effect. The sensor design has been optimized to achieve maximum sensitivity, linearity, and repeatability required for battery cell measurement, and for the first time, the response of the proposed sensor in monitoring of actual EV cell properties is presented. The results are a promising first step towards a sensor device for direct battery SOC measurement and open an opportunity in gaining information about the remaining charge capacity and battery performance.

Scattering Matrix Approach to Design of One-Port Surface Acoustic Wave Resonator Sensors Utilizing Reflectors as Sensing Element

Abstract: It has been recently demonstrated that one-port surface acoustic wave (SAW) resonators known for their high ${Q}$ value and relatively small device footprint could be utilized for in-liquid mass loading sensing applications where only the reflectors of the device are coated with the sensing film, while the interdigital transducer (IDT) is isolated from the sensing environment. The sensor relies on changes induced in reflectivity and phase velocity of SAW in the region of the reflectors upon detection of the measurand and is particularly advantageous for SAW resonator-type sensors as any contact of the sensing film with the IDT could change its static capacitance during sensing and thereby introduce serious instability in the sensor response. Accordingly, in the present work, the existing scattering matrix approach to the design of one-port SAW resonator filters, which does not cater to the integration of sensing film on the resonator surface, is adapted to develop a method to design one-port SAW resonator sensors utilizing reflectors as sensing element. The reflector block of the one-port SAW resonator is readily split into sensing-active and sensing-inactive parts using the SAW grating transmission matrix in order to study the changes introduced in input admittance of the device for varying level of coverage of the sensing film. The theoretical design approach presented in this work could be used to fabricate high-performance one-port SAW resonator sensors operating at its point of highest sensitivity while utilizing one of the device reflectors as sensing element, without the use of additional impedance matching circuit elements.

Research On Optimal Design Of Actuating Performance Based On Annular Dielectric Elastomer Interdigital Transducer

Abstract: Interdigital transducer (IDT), it is widely used in structural health monitoring of large-scale projects, due to its excellent designability. However, for the implementation of structural health monitoring of large-scale complex projects, the existing conventional piezoelectric transducers have some shortcomings, such as poor flexibility, poor mechanical and electrical performance, while the flexible transducer based on polyvinylidene fluoride (PVDF) is difficult to achieve efficient actuating performance. Based on the multi-physical coupling theory, the electrode width, electrode spacing, substrate size and other parameters of IDT was optimized by piezoelectric module. The orientation and the interval of IDT was determined, so as to realize the excellent electromechanical conversion efficiency. Firstly, the annular Dielectric Elastomer Interdigital Transducer (DE-IDT) model with different electrode width, electrode spacing, substrate thickness and substrate size is constructed. Under the piezoelectric plate, the strain of different electrode width, electrode spacing, substrate thickness and substrate size is analyzed. According to the strain, the piezoelectric effect is judged, and the optimal size of DE-IDT is obtained on the basis. The azimuth and distance of DE-IDT are simulated to obtain the optimal actuating distance. The circular DE-IDT has good omnidirectional characteristics and the optimal electrode width, electrode spacing, substrate thickness and substrate size are determined.

Simulation and optimization of geometrical structure of one-port SAW resonator using FEM

Abstract: In this article a one-port surface acoustic wave (SAW) resonator is simulated using COMSOL Multiphysics. The effect of geometrical structure of the piezoelectric substrate and interdigital transducer (IDT) on the resonance frequency is demonstrated and subsequently optimized the height and width of the electrode through simulation. The selection of depth of substrate has been done after a rigorous analysis by varying the length of depth and observing its effect over the nature of resonance frequency. Lithium Niobate has been used as substrate and Al is opted as material for the electrode. Finally one-port SAW resonator has been simulated with the optimized geometry and the mechanical deformation as well as electric potential distribution have been noted, which is very useful for the modelling of any SAW devices.

Capacitive Sensors Integrated in SIW Structures – A Proof of Concept

Abstract: The paper presents a circuit technique aimed to integrate interdigital transducer (IDT) based sensors, provided with either coplanar waveguide (CPW) or microstrip ports, into substrate integrated waveguide (SIW) structures for operation as transmission-type sensors. Therefore, two electromagnetically coupled SIW sections are specifically configured to make possible this conversion. In order to demonstrate the validity of the proposed sensing concept, capacitors of different values, and fully compatible with surface-mounting technology, were assembled at the CPW port of the coupled SIW section to simulate various IDT capacitive sensors. Deviation of the maximum rejection frequency from 4.32 GHz to 7.56 GHz was obtained using capacitance values from 4.7 pF down to 0 pF (i.e. open ended CPW).

mm-Wave Surface Acoustic Wave Filter based on Hexagonal Boron Nitride

Abstract: We show that the operating frequency of surface acoustic wave filter can be significantly improved by adopting an emerging two-dimensional material: hexagonal boron nitride. Electromechanical properties estimated from first principles' analysis revealed that the material has the potential to realize RF filters in mm-Wave. The following piezoelectric simulation demonstrated an operation frequency as high as 36 GHz, which corresponds to Ka-band (from 26.5 to 40 GHz), with the insertion loss of 3 dB. This was achieved with the 150 nm period interdigital transducer on hexagonal boron nitride. Fabricating this scale of metal gratings is not very difficult with advanced lithography technology. As such, a low-power RF filter for 5G and beyond can be realized with the surface acoustic wave of hexagonal boron nitride.

Coupled resonance type surface acoustic wave micro-fluidic chip and manufacturing method thereof

Abstract: The invention discloses a coupled resonance type surface acoustic wave micro-fluidic chip and a manufacturing method thereof, and belongs to the technical field of micro-fluidic chips. The chip comprises a piezoelectric substrate, an interdigital transducer and a cavity top cover, a side wall is arranged between the piezoelectric substrate and the cavity top cover, and a fluid cavity channel is defined by the piezoelectric substrate, the cavity top cover and the side wall. The method comprises the following steps: selecting a material of a cavity top cover according to a piezoelectric substrate, determining the thickness of the cavity top cover according to a working frequency, and manufacturing the cavity top cover; calculating the cross section width and the cross section height of the fluid cavity according to the piezoelectric substrate and the fluid in the fluid cavity, selecting the material of the side wall according to the fluid in the fluid cavity and the piezoelectric substrate, and manufacturing the side wall; and manufacturing the chip according to the piezoelectric substrate, the cavity top cover and the side wall. The invention aims to overcome the defect of low energy of the surface acoustic wave micro-fluidic device in the prior art, and can improve the energy efficiency of the surface acoustic wave micro-fluidic chip.

XBAR resonators with non-rectangular diaphragms

Abstract: Acoustic resonator devices, filter devices, and methods of fabrication are disclosed. An acoustic resonator includes a substrate having a surface and a single-crystal piezoelectric plate having front and back surfaces. The back surface is attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is formed on the front surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm. The IDT is configured to excite a primary acoustic mode in the diaphragm in response to a radio frequency signal applied to the IDT. At least a portion of an edge of the diaphragm is at an oblique angle to the fingers.

Excitation Features of Surface Acoustic Waves by Interdigital Transducer in Piezoelectric Crystals

Abstract: The mathematical models of a long electrode with finite cross-section dimensions, an electrode pair and an interdigital transducer in the excitation mode of surface acoustic waves in Z-sections of piezoelectric crystals of the 6mm crystallographic class are proposed in this article. The accounting of finite dimensions of the electrodes cross-section makes corrections in the numerical values of the synchronism frequency and the level of radiated surface waves. The analytical expressions are obtained and the effect of the electrode cross-section dimensions in electrode pair on the synchronism frequency, the amplitude of the surface acoustic wave, and the module of wave characteristic of interdigital transducer are investigated. We prove that at zero electrode thickness, the maximum displacement level in surface acoustic wave is of 9.75%, and for the square electrode section is 37.25% less than the value obtained by the δ-sources method. At the same time, the synchronism frequency decreases by 9% in the first case. With the electrode thickness equal to the half-width, the real value of synchronism frequency is of 21.7%, and the surface wave amplitude is 33.1% less than in the case of the δ-sources method.

Integrated phononic-photonic circuits on GaAs as a platform for microwave to optical signal transduction

Abstract: Efficient conversion between microwave and optical frequency signals plays an important role in classical and quantum information processing. Recent advances in superconducting devices for quantum technologies have put significant constraints on conversion frequency, power and efficiency between phononic and photonic domains. Here, we demonstrate an acousto-optic modulator (AOM) for conversion of microwave signals up to 2.5 GHz to optical signals in the telecom wavelength range. The modulator is fabricated on a suspended Gallium Arsenide (GaAs) integrated photonic circuit platform, where an unsuspended interdigital transducer (IDT) drives surface acoustic waves to modulate the light travelling in a suspended photonic micro-ring resonator, Fig. 1(a) .

Micro-droplet operating system based on surface acoustic wave chip array

Abstract: A micro-droplet operating system based on a surface acoustic wave chip array comprises a plurality of interdigital transducer array units arranged on a lithium niobate substrate. Each interdigital transducer array unit comprises four independent interdigital transducer arrays evaporated above the lithium niobate substrate, the interdigital transducer arrays are arranged in a bilateral and longitudinal symmetry mode, and a central reaction tank is arranged in the middle. The upper portions of the interdigital transducer arrays are covered with inert carrier liquid in a soaking mode to serve asdiaphragm layers, liquid drops are arranged on the diaphragm layers, and the interdigital transducer arrays are connected with a signal control circuit through an electrode circuit. The signal controlcircuit comprises a signal generation module, the signal generation module generates sine wave signals, four paths of signals with adjustable frequency amplitudes are output through a parallel processing circuit, and a power amplification module acts the amplified four paths of signals on the interdigital transducer arrays to realize driving, mixing and splitting of liquid drops. Free movement ofliquid drops on the surfaces of the diaphragm layers is achieved, repeatability and integration are high, and large-scale application can be achieved.

Thin film material surface acoustic wave device with gs layered electrode, preparation method therefor and use thereof

Abstract: Disclosed are a thin film material surface acoustic wave device with a GS layered electrode, a preparation method therefor and the use thereof. The device sequentially comprises a substrate, a first layer of interdigital transducer, a silica thin film, a piezoelectric thin film and a second layer of interdigital transducer from bottom to top. The preparation method therefor comprises the following steps: 1) using a photoetching technique and an electron beam evaporation method to prepare the first layer of interdigital transducer on the surface of the substrate; 2) growing a silica thin film on the first layer of interdigital transducer and substrate by using a magnetron sputtering method; 3) leveling the surface of the silica thin film, and then growing a piezoelectric thin film on the surface thereof by using the magnetron sputtering method; and 4) preparing the second layer of interdigital transducer on the piezoelectric thin film by using the method in step 1), and aligning the second layer of interdigital transducer with the first layer of interdigital transducer according to settings, and exposing the electrode PAD area of the first layer of interdigital transducer by using the photoetching technique so as to obtain the device. The present invention has a higher frequency and a higher temperature stability, and also has a stronger integration performance.

A resonator and a filter and a duplexer using the resonator

Abstract: A resonator includes an interdigital transducer provided with a main electrode area formed to a shape of a comb on a piezoelectric substrate by a reference pitch in such a manner as to have a unit length along a longitudinal direction thereof and one pair of first electrode areas constituted of one side first electrode area formed to a shape of a comb on the piezoelectric substrate by a first increment pitch obtained by increasing the reference pitch by a first value in such a manner as to have the unit length along the longitudinal direction and the other side first electrode area formed to a shape of a comb on the piezoelectric substrate by a first decrement pitch obtained by decreasing the reference pitch by almost the same value as the first value.

Real-time sensing of trace TNT with acoustic surface wave method based on the modified interdigital transducer electrodes

Abstract: 2,4,6-trinitrotoluene (TNT) has a strong explosive force and environmental toxicity, with the increasing threat of terrorist attacks worldwide, the high sensitivity detection of nitroaromatic explosives has become an urgent problem to be solved, and now the commonly used detection method is to use the optical principle, combined with large and expensive equipment to detect it. In order to detect the content of TNT in bad environment quickly and in real time, surface acoustic wave technology was proposed to detect different concentrations of TNT. In this paper, an ultra-sensitive TNT sensor was fabricated based on the surface acoustic wave technique. Specific detection of TNT was achieved by recognizing the shift of resonance frequency. Moreover, the whole process for the detection was done in 30 min, dedicating the rapid/real-time application of the sensor. This study focused on the transfer characteristics of resonance frequencies at different concentrations. The frequency of surface sound waves varies greatly at high concentration because the modified IDT (interdigital transducers) electrodes were utilized, which is easy to work under different concentrations of TNT. The proposed sensor has the advantages of real-time, simple and convenient detection, which provides a valuable method for the real-time detection of TNT.

Variable-frequency surface acoustic wave e-cigarette

Abstract: A variable-frequency surface acoustic wave e-cigarette, comprising an atomizer (2). An atomization chamber (213) is provided inside the atomizer (2), a variable-frequency surface acoustic wave atomization chip (203) is arranged in a lower portion of the atomization chamber (213), and an inverted trapezoidal interdigital transducer (2037) is provided on the variable-frequency surface acoustic wave atomization chip (203). An oil storage chamber (205) is provided inside the atomization chamber (213), and a porous ceramic piece (204) is arranged between the oil storage chamber (205) and the atomization chip (203). The variable-frequency surface acoustic wave e-cigarette allows for arbitrary adjustment of an operating frequency within a set range, thus making possible autonomous control of e-liquid vapor particle size.