Surface Acoustic Wave Technology Research Articles

Achieving consistency of flexible surface acoustic wave sensors with artificial intelligence

Flexible surface acoustic wave technology has garnered significant attention for wearable electronics and sensing applications. However, the mechanical strains induced by random deformation of these flexible SAWs during sensing often significantly alter the specific sensing signals, causing critical issues such as inconsistency of the sensing results on a curved/flexible surface. To address this challenge, we first developed high-performance AlScN piezoelectric film-based flexible SAW sensors, investigated their response characteristics both theoretically and experimentally under various bending strains and UV illumination conditions, and achieved a high UV sensitivity of 1.71 KHz/(mW/cm²). To ensure reliable and consistent UV detection and eliminate the interference of bending strain on SAW sensors, we proposed using key features within the response signals of a single flexible SAW device to establish a regression model based on machine learning algorithms for precise UV detection under dynamic strain disturbances, successfully decoupling the interference of bending strain from target UV detection. The results indicate that under strain interferences from 0 to 1160 με the model based on the extreme gradient boosting algorithm exhibits optimal UV prediction performance. As a demonstration for practical applications, flexible SAW sensors were adhered to four different locations on spacecraft model surfaces, including flat and three curved surfaces with radii of curvature of 14.5, 11.5, and 5.8 cm. These flexible SAW sensors demonstrated high reliability and consistency in terms of UV sensing performance under random bending conditions, with results consistent with those on a flat surface.

Research on particle separation microfluidic chip based on standing surface acoustic wave

Microparticle and cell separation is a key process in the study of cell properties, clinical diagnosis and disease treatment. In this paper, a particle separation method based on the combination of surface acoustic wave and microfluidic technology is proposed, which uses standing surface acoustic wave to achieve the separating of polystyrene microparticles of different sizes twice in a continuous flow. Through numerical simulation of the device model and particle trajectory simulation, the optimum particle separation parameters were determined. The particle separation microfluidic chip has successfully realized the particle separation. The separation yield of 5 μm particles is about 92.1%. The separation rate of 1 μm particles is about 83.3%.

Acoustic wave devices based on piezoelectric/ferroelectric thin films for high-frequency communication systems and sensing applications

Surface acoustic wave (SAW) and bulk acoustic wave (BAW) based radio-frequency (RF) filters dominate in handsets markets mainly because they have miniature size so multiple filters can be used but take up very small board area. Besides, due to their inherent advantages, such as low insertion loss, relatively high resonant frequency, and miniature size, their application in the physical and biochemical sensing fields has also gradually expanded. The successful implementation requires specific knowledge of acoustic wave properties, the working mechanisms, material properties, and device design. So, in this review, we survey the SAW and BAW filter technology by discussing the working principles and the comparison between the operation frequency band allocations. In addition, the approaches to enhance the performance including the selection of single crystal/ferroelectric materials for BAW and the structure design optimization for SAW are introduced with discussions for further improvement. Then, flexible SAW and BAW devices are also presented and their new application opportunities in the fields of skin-like electronics and wearable health monitoring devices can be foreseen. Finally, the potential challenges of high frequency, wide bandwidth, miniaturization, and compatibility with the integrated circuits (IC) manufacturing process are overviewed as well.

New Advances in Rapid Pretreatment for Small Dense LDL Cholesterol Measurement Using Shear Horizontal Surface Acoustic Wave (SH-SAW) Technology.

Atherosclerosis is an inflammatory disease of the arteries associated with alterations in lipid and other metabolism and is a major cause of cardiovascular disease (CVD). LDL consists of several subclasses with different sizes, densities, and physicochemical compositions. Small dense LDL (sd-LDL) is a subclass of LDL. There is growing evidence that sd-LDL-C is associated with CVD risk, metabolic dysregulation, and several pathophysiological processes. In this study, we present a straightforward membrane device filtration method that can be performed with simple laboratory methods to directly determine sd-LDL in serum without the need for specialized equipment. The method consists of three steps: first, the precipitation of lipoproteins with magnesium harpin; second, the collection of effluent from a 100 nm filter; and third, the quantification of sd-LDL-ApoB in the effluent with an SH-SAW biosensor. There was a good correlation between ApoB values obtained using the centrifugation (y = 1.0411x + 12.96, r = 0.82, n = 20) and filtration (y = 1.0633x + 15.13, r = 0.88, n = 20) methods and commercially available sd-LDL-C assay values. In addition to the filtrate method, there was also a close correlation between sd-LDL-C and ELISA assay values (y = 1.0483x - 4489, r = 0.88, n = 20). The filtration treatment method also showed a high correlation with LDL subfractions and NMR spectra ApoB measurements (y = 2.4846x + 4.637, r = 0.89, n = 20). The presence of sd-LDL-ApoB in the effluent was also confirmed by ELISA assay. These results suggest that this filtration method is a simple and promising pretreatment for use with the SH-SAW biosensor as a rapid in vitro diagnostic (IVD) method for predicting sd-LDL concentrations. Overall, we propose a very sensitive and specific SH-SAW biosensor with the ApoB antibody in its sensitive region to monitor sd-LDL levels by employing a simple delay-time phase shifted SH-SAW device. In conclusion, based on the demonstration of our study, the SH-SAW biosensor could be a strong candidate for the future measurement of sd-LDL.

Aerosol jet printing of surface acoustic wave microfluidic devices

The addition of surface acoustic wave (SAW) technologies to microfluidics has greatly advanced lab-on-a-chip applications due to their unique and powerful attributes, including high-precision manipulation, versatility, integrability, biocompatibility, contactless nature, and rapid actuation. However, the development of SAW microfluidic devices is limited by complex and time-consuming micro/nanofabrication techniques and access to cleanroom facilities for multistep photolithography and vacuum-based processing. To simplify the fabrication of SAW microfluidic devices with customizable dimensions and functions, we utilized the additive manufacturing technique of aerosol jet printing. We successfully fabricated customized SAW microfluidic devices of varying materials, including silver nanowires, graphene, and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). To characterize and compare the acoustic actuation performance of these aerosol jet printed SAW microfluidic devices with their cleanroom-fabricated counterparts, the wave displacements and resonant frequencies of the different fabricated devices were directly measured through scanning laser Doppler vibrometry. Finally, to exhibit the capability of the aerosol jet printed devices for lab-on-a-chip applications, we successfully conducted acoustic streaming and particle concentration experiments. Overall, we demonstrated a novel solution-based, direct-write, single-step, cleanroom-free additive manufacturing technique to rapidly develop SAW microfluidic devices that shows viability for applications in the fields of biology, chemistry, engineering, and medicine.

MXene-activated graphene oxide enhancing NO2 capture and detection of surface acoustic wave sensors

Surface acoustic wave (SAW) technology has been widely used in the field of harmful gas detection, but there remain a lot of challenges, such as long response/recovery time as well as poor selectivity and repeatability. Herein, we activate graphene oxide (GO) using MXene with excellent adsorption capacity (MXene/GO) to realize efficient NO2 gas detection. The SAW sensor assembled with the multilayered MXene/GO composite showcases an enhanced gas sensing performance to the NO2 gas (1–200 ppm) enabling high sensitivity (Δf=260 Hz/ppm), fast response/recovery time, excellent selectivity, and good repeatability at room temperature. The enhanced high sensitivity and selectivity detection of NO2 gas is attributed to the large pore size, hydrophilicity, and abundant surface functional groups of the multilayered MXene/GO composite. This elaborate design is expected to propel the development of next-generation acoustic gas phase sensors.

Research and experiment the wireless passive surface acoustic wave technology for conductor temperature monitoring of high voltage equipment

This paper presents the research and design of a passive thermal monitoring system using wireless temperature sensors based on the principle of surface acoustic wave (SAW). The monitoring system is employed on components that need to be monitored for heat generation, including switch contacts, busbars, and cable connections at switchgears or ring main units (RMUs). The basic impulse insulation level (BIL), or voltage spike tolerance, of the wireless SAW temperature sensor utilised in this study, means that it is not necessary to power it with sensors that meet the high criteria for equipment installed in closed cabinets or medium voltage cabinets. The research team’s activities in this study included software development, data transmission design and manufacture, and sensor selection. The system functions steadily, with a temperature error of no more than 2oC, according to the test findings under laboratory settings.

A High-Performance Weighing Sensor Based on Surface Acoustic Wave Technology

A High-Performance Weighing Sensor Based on Surface Acoustic Wave Technology

Acoustofluidic patterning in glass capillaries using travelling acoustic waves based on thin film flexible platform

Surface acoustic wave (SAW) technology has been widely used to manipulate microparticles and biological species, based on acoustic radiation force (ARF) and drag force induced by acoustic streaming, either by standing SAWs (SSAWs) or travelling SAWs (TSAWs). These acoustofluidic patterning functions can be achieved within a polymer chamber or a glass capillary with various cross-sections positioned along the wave propagating paths. In this paper, we demonstrated that microparticles can be aligned, patterned, and concentrated within both circular and rectangular glass capillaries using TSAWs based on a piezoelectric thin film acoustic wave platform. The glass capillary was placed at different angles along with the interdigital transducer directions. We systematically investigated effects of tilting angles and wave characteristics using numerical simulations in both circular and square shaped capillaries, and the patterning mechanisms were discussed and compared with those agitated under the SSAWs. We then experimentally verified the particle patterns within different glass capillaries using thin film ZnO SAW devices on aluminum (Al) sheets. Results show that the propagating SAWs can generate acoustic pressures and patterns in the fluid due to the diffractive effects, drag forces and ARF, as functions of the SAW device’s resonant frequency and tilting angle. We demonstrated potential applications using this multiplexing, integrated, and flexible thin film-based platform, including patterning particles (1) inside multiple and successively positioned circular tubes; (2) inside a solidified hydrogel in the glass capillary; and (3) by wrapping a flexible ZnO/Al SAW device around the glass capillary.

On-Chip Label-Free Sorting of Living and Dead Cells.

With the emergence of various cutting-edge micromachining technologies, lab on a chip is growing rapidly, but it is always a challenge to realize the on-chip separation of living cells from cell samples without affecting cell activity and function. Herein, we report a novel on-chip label-free method for sorting living and dead cells by integrating the hypertonic stimulus and tilted-angle standing surface acoustic wave (T-SSAW) technologies. On a self-designed microfluidic chip, the hypertonic stimulus is used to distinguish cells by producing volume differences between living and dead cells, while T-SSAW is used to separate living and dead cells according to the cell volume difference. Under the optimized operation conditions, for the sample containing 50% of living human umbilical vein endothelial cells (HUVECs) and 50% of dead HUVECs treated with paraformaldehyde, the purity of living cells after the first separation can reach approximately 80%, while after the second separation, it can be as high as 93%; furthermore, the purity of living cells after separation increases with the initial proportion of living cells. In addition, the chip we designed is safe for cells and can robustly handle cell samples with different cell types or different causes of cell death. This work provides a new design of a microfluidic chip for label-free sorting of living and dead cells, greatly promoting the multi-functionality of lab on a chip.

Velocity and Direction Adjustment of Actuated Droplets Using the Standing Wave Ratio of Surface Acoustic Waves (SAW)

Droplet actuation using surface acoustic wave (SAW) technology has recently been widely employed in “lab-on-a-chip” applications. In this article, SAWs generated by interdigital transducers (IDTs) were used to actuate microdroplets, where their velocity and direction could be adjusted by changing only the excitation phase shift, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">θ</i> , of the voltage applied to the two IDTs. Specifically, the equation of the vibration of the mixed traveling surface acoustic waves (TSAWs) and standing surface acoustic waves (SSAWs) formed on the substrate surface operating in the exciter–exciter mode has been reported by the authors. An analytical expression for the acoustic standing wave ratio has been derived and given as a function of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">θ</i> and the spatial phase difference. It can be seen from the expression that the directions of the TSAWs will be opposite to each other, in the range of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">θ</i> given by (0, π) and (π, 2π), and the component of the TSAWs can be adjusted by changing <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">θ</i> in each direction. Following the theoretical analysis discussed here, two IDTs have been excited to generate a mixture of TSAWs and SSAWs. A series of experiments was carried out to control the velocity and direction of the actuated droplets, by changing only <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">θ</i> . In addition, an experiment performed to compare the techniques shows that the upper limit of the velocity of the actuated droplets can be significantly increased using the exciter–exciter mode, showing that it has the potential to be an alternative method to the traditional exciter–absorber mode.

Versatile and effective design platform for surface acoustic wave accelerometers

Micro-electro-mechanical system (MEMS) accelerometers have great potentials for applications in aerospace, autonomous driving and consumer electronics. However, their working principles are mostly based on capacitive and resistance types, which cannot be easily and effectively used for wireless and passive sensing, while surface acoustic wave (SAW) technology is the key solution for this problem. Due to complex acoustic-electric-mechanical coupling during SAW accelerators’ operations, currently, there needs an accurate, reliable, and efficient design and simulation platform to improve their structure and performance. In this work, we proposed an accurate, reliable, and efficient modeling platform to optimize designs of SAW accelerometers, using a double-ended cantilever beam structure as an example. This model integrated the elastic acoustic effect and the coupled wave equations under both the mechanical and electrical loading using the finite element analysis, and effectively obtained acceleration-frequency responses of the SAW accelerators. We have systematically simulated effects of thickness of piezoelectric film, wavelength, and structural parameters of cantilever beams, and the simulation results are well consistent with the theoretical ones. Finally, using the developed model, we designed a high-G SAW accelerometer (up to 20000 g) with a high sensitivity (−41.8 Hz g−1) and excellent linearity (0.9999), and another one with a high sensitivity (3.02 KHz g−1) and a good linearity (0.9999) over a 100 g acceleration range.

Review of Surface Acoustic Wave Sensors for the Detectionand Identification of Toxic Environmental Gases/Vapours

Detection and identification of toxic environmental gases have assumed paramount importance precisely in the defense, industrial and civilian security sector. Numerous methods have been developed for the sensing of toxic gases in the environment ever since surface acoustic wave (SAW) technology came into existence. Such SAW sensors called electronic nose (E-Nose) sensor use the frequency response of a delay line/resonator. SAW device is focused and given importance. The selective coating between input and output interdigital transducers (IDTs) in the SAW device is responsible for corresponding changes in operating frequency of the device for a specific gas/vapour absorbed from the environment. A suitable combination of well-designed SAW delay lines with selective coatings not only help to improve sensor sensitivity and selectivity but also leads to the minimization of false frequency alarms in the E-Nose sensor. This article presents a comprehensive review of design, development, simulation and modelling of a SAW sensor for potential sensing of toxic environmental gases.

Ultrahigh frequency shear-horizontal acoustic wave humidity sensor with ternary nanocomposite sensing layer

Surface acoustic wave (SAW) technology is promising for humidity monitoring due to its digital output, small size, large-scale production and wireless passive capability, but there are major challenges to achieve ultra-high sensitivity and fast responses using the conventional SAW devices. Herein, ultrahigh frequency (4.7 GHz and 5.9 GHz) shear-horizontal (SH) SAW devices were developed and a ternary nanocomposite strategy of graphene quantum dots/polyethyleneimine/silicon dioxide nanoparticles (GQDs-PEI-SiO2 NPs) was proposed as a sensitive layer to achieve ultrahigh sensitivity and fast response. This ternary material system was constructed by modifying the surface of SiO2 NPs with the PEI through an electrostatic force, and then adsorbing the GQDs onto the PEI through hydrogen bonds. Compared with the conventional low frequency SAW devices, the ultrahigh frequency SH-SAW devices showed exceptionally ultra-high sensitivity (2.4 MHz/%RH, 1000 times as high as a 202 MHz SAW device), fast response (20 s/5 s), excellent linearity, and good repeatability in the range of 20–80% RH. These superior performances are attributed to ultrahigh frequency of SAW devices, large specific surface areas of the nanocomposite (which exposed multiple hydrophilic groups in PEI and GQDs), and high vapor pressure of convex spherical curved liquid surface (which accelerated the adsorption and desorption of water molecules).

Decoupling Acoustoelectric and Thermal Effects of Ultraviolet Responses for Acoustic Wave Sensing Mechanisms

Ultraviolet (UV) detectors based on surface acoustic wave (SAW) technology offer unique advantages of remote or wireless operation capability with a potential of zero power consumption. Frequency shift of SAW devices induced by UV irradiation is mainly caused by acoustoelectric and thermal effects, although mass-loading and photo-capacitive effect might also have minor influences. Currently the individual contribution from either acoustoelectric effect or thermal effect for UV sensing has not been thoroughly studied. In this work, we systematically investigated the contribution of acoustoelectric and thermal effects at different UV light intensities based on a LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> SAW device with its wavelength of 20 μm, and decoupled their individual contributions to the overall ultraviolet responses for acoustic wave sensing. We found that for the LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> SAW device without any surface treatment, the frequency shift was mainly caused by the thermal accumulation induced by UV radiation. Whereas for the LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> SAW devices coated with zinc oxide nanowires (ZnO NWs), the frequency shift is caused by the combined acoustoelectric and thermal effects. We found that the frequency shift caused by acoustic electric effect is dominant at a low UV intensity (< 30 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ). Whereas with the UV light intensity larger than 90 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , the photogenerated carriers generated by ZnO NWs became saturated, and then the thermal effect became dominant. This study clarifies the nature of individual influences of these two factors on the dominant mechanisms of the SAW based UV sensing at different conditions.

Integrated transparent surface acoustic wave technology for active de-fogging and icing protection on glass

There have been great concerns on poor visibility and hazardous issues due to fogging and ice/frost formation on glass surfaces of windshields, windows of vehicles/airplanes, and solar panels. Existing methods for their monitoring and removal include those active ones (such as using resistance heating) or passive ones (such as using surface icephobic treatments), which are not always applicable, effective or reliable. In this study, we proposed a novel strategy by implementing transparent thin film surface acoustic wave (SAW) devices by directly coating ZnO films onto glass substrate and studied their de-fogging, active anti-icing and de-icing mechanisms using the SAW technology. Effects of powers and wavelengths of SAW devices were investigated and influences of acousto-heating and surface hydrophobic treatments were evaluated. Results showed that de-fogging time was dramatically decreased with the increase of SAW powers when the thin film-based SAW devices were exposed to humid air flow for different durations. The icing accretion was significantly delayed under the applied SAW agitation, and SAW application has also effectively promoted de-icing on glass substrate, due to the interfacial nanoscale vibration and localized heating effect.

Surface Acoustic Wave Humidity Sensor: A Review.

The Growing demands for humidity detection in commercial and industrial applications led to the rapid development of humidity sensors based on different techniques. Surface acoustic wave (SAW) technology is one of these methods that has been found to provide a powerful platform for humidity sensing owing to its intrinsic features, including small size, high sensitivity, and simple operational mechanism. Similar to other techniques, the principle of humidity sensing in SAW devices is also realized by an overlaid sensitive film, which serves as the core element whose interaction with water molecules is responsible for overall performance. Therefore, most researchers are focused on exploring different sensing materials to achieve optimum performance characteristics. This article reviews sensing materials used to develop SAW humidity sensors and their responses based on theoretical aspects and experimental outcomes. Herein the influence of overlaid sensing film on the performance parameters of the SAW device, such as quality factor, signal amplitude, insertion loss, etc., is also highlighted. Lastly, a recommendation to minimize the significant change in device characteristics is presented, which we believe will be a good step for the future development of SAW humidity sensors.

Abstract 159: Vascularized 3D cancer organoid research platform using surface acoustic waves

Abstract Recently, organoids have been widely used in cancer research. However, cancer organoids have limitation in reflecting physicochemical microenvironments of tumor. In particular, vascular networks not only provide oxygen and nutrients to the tumor, but also play an important role as a channel through which drugs move in cancer. Vascularization occurs in an uncontrollable form and speed in conventional methods. Here, we regulate the directionality of the vascular bed using the surface acoustic waves(SAW) technology by which, vascular cells are locally aligned. Aligned cells exhibited an improved, cell-cell contact enhancing the vascular system maturation in a couple days. Organoids are constructed from gastric cancer patients with four molecular subtypes according to TCGA. Organoids were dissociated into a single cell to make a co-culture spheroid with HUVEC cells. Co-cultured spheroids were formed by adding fibronectin according to the characteristics of the patient sample. The SAW device is built with interdigitated transducer, NiNbO3 substrate, polydimethylsiloxane(PDMS) and coverglass. After putting co-culture spheroids and HUVEC cells mixed with fibrin gel into the device, patterning is performed using surface acoustic waves with shaking in EGM-2 media. After fixing the models, CD31 and F-actin are stained and imaged through immunofluorescent. Immunohistochemistry was performed to confirm the blood vessel cross section. The blood vessels patterned with SAW were well aligned in a straight line, and a lumen structure was formed in a couple days. When co-cultured spheroids were used compared to mono-cultured spheroids, the interaction with external HUVECs was improved, allowing for efficient vascular organism models. As evidence for this, it was confirmed that HUVEC inside the co-cultured spheroid and HUVEC outside were connected through interaction when PKH dyeing was done in a different color. We showed that blood vessels are formed faster and thicker in patterning models than in random models, and interactions with co-cultured spheroids are also high. Through immunofluorescent staining, we found that the number of vascular branches linked to spheroids was higher in the SAW model. In addition, in the H&amp;E results, it was confirmed that the blood vessels were arranged in a line, and that differentiation occurred appropriately to form a tubular structure. In addition, the number of blood formed inside the spheroid was higher. Currently, this model is used to test anti-cancer efficacy using FGFR inhibitors and ramucirumab in FGFR2-amplified patient-derived organoids. An efficient vascularized 3D cancer organoid model was constructed using acoustic waves. Our vascularized 3D cancer organoid research platform will be applied for specific drug screening platform that directly aid the treatment of the specific patients with various drugs including chemoagents, targeted drugs, and immune checkpoints inhibitors. Citation Format: Hyoyoung Kim, Yunam Lee, Byungjun Kang, Un-Jung Yun, Yunjung Choi, So Hui Kim, Hyunki Kim, Hyungsuk Lee, Minkyu Jung. Vascularized 3D cancer organoid research platform using surface acoustic waves [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 159.

A Composite Gas-Phase Explosives Sensor with Frequency-Resistance Dual-Signal Display Based on Surface Acoustic Wave

The surface acoustic wave (SAW) technology has been widely used for hazardous gas detection, but the low sensitivity, poor selectivity, long response/recovery time, and signal “false positives” of the sensors have limited its application for gas-phase explosives detection. In this paper, a composite gas-phase explosives sensor with frequency-resistance dual-signal display was designed by transferring 25 layers of graphene (rGO) in the sensing area of the SAW device and coupling p-aminothiophenol (PATP)-modified gold nanoparticles (AuNPs). The rGO:AuNP/PATP-SAW sensor shows signal response from two signal dimensions, frequency and resistance, to 0.1–80 ppm TNT gas with a low detection limit (DL) of 41.2 ppb. The composite sensor has a short response/recovery time (9.8 s/27.1 s) with good selectivity, repeatability, and stability. The excellent gas-sensitive performance of the rGO:AuNP/PATP-SAW sensor was attributed to the fact that PATP provides a large number of selective capture groups, which are enriched in the sensing area by the presence of multiple strong interactions with 2,4,6-trinitrotoluene (TNT) molecules. This work will provide scientific guidance for the engineering promotion of surface acoustic wave gas-phase explosives sensors.

Machine learning empowered thin film acoustic wave sensing

Thin film-based surface acoustic wave (SAW) technology has been extensively explored for physical, chemical, and biological sensors. However, these sensors often show inferior performance for a specific sensing in complex environments, as they are affected by multiple influencing parameters and their coupling interferences. To solve these critical issues, we propose a methodology to extract critical information from the scattering parameter and combine the machine learning method to achieve multi-parameter decoupling. We used the AlScN film-based SAW device as an example in which the highly c-axis orientated and low stress AlScN film was deposited on silicon substrate. The AlScN/Si SAW device showed a Bode quality factor value of 228 and an electromechanical coupling coefficient of ∼2.3%. Two sensing parameters (i.e., ultraviolet or UV and temperature) were chosen for demonstration, and the proposed machine learning method was used to distinguish their influences. Highly precision UV sensing and temperature sensing were independently achieved without their mutual interferences. This work provides an effective solution for decoupling of multi-parameter influences and achieving anti-interference effects in thin film-based SAW sensing.