Search Results (104)

To exploit ultra-low power logic and architectural design techniques for bio-sensors in the human body, wireless ultrasonic techniques have emerged as a strong candidate for intra-body power transmission, thanks to lower medium attenuation and higher permitted safe intensity levels. When sub-100 $\mathsf{\mu }$m dimensions are considered for the bio-sensor, most devices struggle to guarantee a suitable voltage and power for digital electronics due to additional scaling requirements. This study investigates three alternative piezoelectric micromachined ultrasonic transducers in aluminum nitride doped with scandium, as reported in the literature, operating in the range 1–10 MHz. Their respective advantages and limitations with regard to energy harvesting and signal transmission performance are analyzed. It is shown that devices with footprints of less than 100 × 100 $\mathsf{\mu }$m² can achieve voltage outputs of over 150 mV and average power greater than 100 nW. Full article

Multifrequency operation in micromachined ultrasonic transducers, enabled by targeted excitation of specific vibrational modes, has emerged as an attractive approach for achieving tunable performance and configurability, well-suited for advanced ultrasound imaging and therapeutic applications. This paper presents a dual-electrode rectangular piezoelectric micromachined ultrasonic transducer (PMUT) designed for efficient dual-frequency operation through mode-selective actuation. The proposed architecture employs segmented electrodes that are spatially aligned with the strain distributions of two distinct flexural modes, enabling selective excitation of Mode 1 (fundamental) and Mode 3 (higher order) through appropriate electrode actuation. Finite element simulations and impedance analysis were used to guide the electrode configuration and validate the mode-selective behavior. The dual-mode PMUT was fabricated alongside a conventional single-electrode PMUT using identical membrane dimensions and material stack for direct comparison. Comprehensive electrical and underwater acoustic characterization confirmed that the conventional PMUT is limited to single-frequency operation at the fundamental resonance. In contrast, the proposed design achieved a substantial improvement in higher-order performance, with a threefold increase in acoustic pressure at Mode 3 compared to the conventional device. These results demonstrate that mode-aligned electrode segmentation enables efficient dual-mode operation without added fabrication complexity, making the design highly suitable for multifrequency ultrasonic applications such as biomedical imaging and sensing. Full article

A bottom-up fabrication approach for flexible piezoelectric micromachined ultrasound transducer (PMUT) arrays on stainless-steel substrates was developed. Devices were fabricated using chemical solution deposition of a 700 nm-thick layer of Pb_0.99□_0.01(Zr_0.52Ti_0.48)Nb_0.02O₃, where □ denotes a vacancy on the Pb site, on 50 μm-thick LaNiO₃/HfO₂/stainless-steel foils. Lithography for definition of the electrode and piezoelectric layers was completed on the front of the wafer. Ni electroplating on the back side of the foil was used to create locally stiff areas to define the deflection area. PMUT devices were successfully fabricated using this method. The permittivity and loss tangent of the fabricated device at 1 kHz were 283 ± 9 and <1.5%, respectively. The remanent polarization was measured to be 38 ± 0.3 μC/cm². Full article

This study presents a high-frequency ultrasound lens system that uses simply fabricated and low-cost acoustic lenses made from PMMA and PDMS materials. These lenses are designed for higher-frequency operation around 20 MHz, providing suitability for demanding high-frequency ultrasonic applications. They were designed and fabricated specifically for integration with a PMUT array, ensuring proper compatibility with array-based high-frequency ultrasonic imaging. Both Fresnel and convex lens designs were evaluated through axial and lateral beam measurements, along with pulse–echo testing in the focal region. The results show that the PMMA and PDMS lenses can produce a well-defined focus and a stable echo response despite their simple and low-cost fabrication. This demonstrates the feasibility of low-cost materials for high-frequency ultrasonic focusing in PMUT array applications. Full article

High-performance piezoelectric micromachined ultrasonic transducers (PMUTs) are crucial for portable medical imaging and sensing. The efficiency of advanced PMUTs relies on high-quality piezoelectric thin films and optimized device designs. However, variability in common piezoelectric thin films like Sc_xAl_1−xN (ScAlN) and PbZr_1−xTi_xO₃ (PZT) often leads to inaccurate material parameters—especially those derived from thick ceramics. To enhance simulation accuracy in standard designs affected by these inconsistencies, this work introduces an optimization framework combining first-principles calculations with multiphysics simulations. First, the intrinsic properties of PZT and ScAlN are analyzed through atomistic calculations, confirming that PZT, with its higher electromechanical coupling coefficient, is better suited for actuation. The parameters obtained from these calculations calibrate the finite-element model, addressing issues of missing or inaccurate data in commercial software libraries. Next, an efficient analytical acoustic-field model is developed. Compared to full-wave simulations in COMSOL, this model significantly reduces computational cost while maintaining accuracy, allowing for quicker scanning and optimization of large-array topologies. Additionally, results demonstrate that each individual hexagonal PMUT element outperforms a comparable circular element, achieving a peak SPL of 90.4 dB at 4.9 MHz versus 89.7 dB at 2.8 MHz. This higher acoustic output and operating frequency enable improved spatial resolution and sensitivity. This modeling approach, based on intrinsic material properties, provides a solid theoretical foundation for designing high-precision, low-power ultrasonic devices. Full article

To mitigate acoustic beam drift, which degrades the signal-to-noise ratio (SNR) and limits the measurement range in ultrasonic gas flowmeters (USFMs), we present a miniaturized transit-time USFM that integrates a single piezoelectric micromachined ultrasonic transducer (PMUT) with a non-axisymmetric conical cavity. This design increases acoustic transmission gain and produces anisotropic directivity across orthogonal radiation planes, thereby broadening acoustic coverage along the flow direction and reducing beam steering. With an optimized cavity angle combination of (50°, 70°), the system achieves a 7.4 dB transmission gain and a half-power beamwidth (HPBW) of 29.1°. Experimental validation demonstrates a sound pressure attenuation of only 0.72 dB at 18.74 m/s. Within the 0.06–12 m³/h flow range, the USFM exhibits indication errors of ±2% (<1 m³/h) and ±1.5% (≥1 m³/h), with repeatability below 0.5%. The performance meets the Class 1.5 accuracy standard specified in CJ/T 477-2015, offering an innovative solution for wide-range miniaturized gas flow measurement. Full article

Blink monitoring has demonstrated significant application value in fields such as safety assessments, medical monitoring, and intelligent technologies. Traditional eye monitoring methods are limited by restricted adaptability, insufficient comfort, or potential risks. MEMS-based ultrasonic technology, as a non-contact approach, has garnered attention due to its strong environmental adaptability, privacy, and security. However, existing designs require high-sensitivity processing circuits and are incompatible with standard fabrication processes. This work proposes a dual-electrode piezoelectric micro-mechanical ultrasonic transducer (PMUT) design based on aluminum nitride (AlN) piezoelectric thin films, integrated into a glasses device to enable real-time blink activity monitoring. The design successfully identifies blink states through time-of-flight (TOF) pulse-echo technology and dynamic unsupervised learning methods. Fabricated using cost-effective standard multi-user MEMS processes, this device offers distinct merits in terms of wearability comfort, information security, biosafety, and reliability. Full article

Crosstalk between elements in ultrasonic transducer arrays significantly degrades image quality in medical ultrasound systems by introducing noise and reducing spatial resolution. This review provides a comprehensive overview of the origins of crosstalk—acoustic, mechanical, and electrical—and the main characterization methods used to analyze it, including direct measurements, impedance analysis, finite element modeling, and equivalent circuit approaches. Emphasis is placed on recent advances in passive and active mitigation strategies, such as material coatings, structural decoupling, phononic crystals, adaptive filtering, and impedance matching. A key finding is that the optimal crosstalk reduction method depends strongly on the transducer technology employed—whether CMUT, PMUT, or bulk PZT. The review highlights the importance of tailoring mitigation techniques to the physical properties and operating conditions of each technology. By synthesizing current knowledge and identifying remaining challenges—particularly the role of filler material losses—this work offers a solid foundation for the development of next-generation ultrasound arrays with enhanced imaging performance. Full article

Ultrasound transducers are fundamental components in medical imaging systems, impacting resolution, sensitivity, and penetration depth. A key challenge in designing high-performance ultrasound transducers is balancing bandwidth and sensitivity. This study focuses on optimizing the backing layer of a dual-frequency piezoelectric micromachined ultrasound transducer (PMUT) using polydimethylsiloxane (PDMS). COMSOL multi-physics version 6.2 finite element simulations and equivalent circuit modeling were employed to investigate the effects of PDMS backing layer thickness and geometry on frequency response characteristics, impedance matching, and acoustic sensitivity. The optimized PMUT structure demonstrated a significant enhancement in bandwidth, with the −6 dB bandwidth increasing to 92% at both 2.3 MHz and 6.8 MHz frequencies. The PDMS backing layer improved the matching of low- and high-frequency signals, enabling high sensitivity and reduced interface reflection losses. The incorporation of PDMS as the backing layer successfully expands the operational bandwidth of dual-frequency PMUTs while maintaining high sensitivity, offering promising potential for high-performance ultrasound imaging, particularly in medical applications requiring both deep penetration and high-resolution imaging. Full article

Air-coupled ultrasonic detection demands high transmission performance from piezoelectric micromachined ultrasonic transducers (PMUTs). However, existing microelectromechanical system (MEMS)-based PMUTs deliver limited output, which compromises measurement accuracy and constrains further development. This work proposes a novel PMUT design with a cantilevered, boundary-suspended diaphragm that relieves residual stress, relaxes edge constraints, increases the mechanical degrees of freedom, and enables larger vibration amplitudes. Additionally, this work develops an accurate air-coupling model to predict device performance and a streamlined micro-nanofabrication process for device realization. Experimental results show that under a 1 Vpp (−5 Voffset) drive, the device achieves a peak acoustic pressure of 4.004 Pa at 69.3 kHz, measured at 10 cm distance in air, corresponding to a maximum sound pressure level of 106.02 dB (re 2 × 10⁻⁵ Pa). Compared to a traditional PMUT at 98.45 dB, this represents a 7.57 dB improvement and, to our knowledge, the highest reported sound pressure level at 10 cm for a single PMUT operating near 70 kHz under a 1 Vpp excitation. These results validate the significant enhancement in transmission performance achieved by the proposed topological structure, offering a solution to overcome the common bottleneck of insufficient output in PMUTs, and indicate strong potential for broader air-coupled sensing applications. Full article

Microdevices with dimensions comparable to a blood cell, i.e., tens of micrometers, show great potential for use in the human body. They can be adopted to identify the source of diseases, track their evolution and enhance the effectiveness of therapies, significantly improving patients’ quality of life. A key challenge is how to power the devices, which should ideally be performed wirelessly from a remote source. Piezoelectric micromachined ultrasonic transducers (pMUTs) offer a solution thanks to their ability to generate and collect energy via acoustic waves. In this work, numerical simulations of transmitter pMUT arrays are performed with the aim of generating an acoustic wave synchronized with a single pMUT or pMUT array receiver. The latter is intended for insertion in the human body. The characteristics required to switch on and power nano-electronics, in terms of generated voltage and electrical power at the receiver, are studied in ballistic gel, a material that mimics human organs. The focus is on a bio-compatible material for the piezoelectric layer, i.e., aluminum nitride enriched with scandium. Coupled electromechanical and acoustic simulations show that, of the considered pMUT devices, an 8 × 8 transmitter array combined with a single-device receiver (with a 50 µm pitch) or a 2 × 2 receiver array provide alternative options, with each offering advantages in terms of voltage amplitude or power at a steady state. The overall dimensions of the receiver, at a maximum of only 100 × 100 µm², is compatible with a future proof-of-concept biosensing platform test chip. Full article

Background and objectives: Adducins are cytoskeletal proteins essential for membrane stability, actin–spectrin network organization, and cell signaling. Mutations in the genes ADD1, ADD2, and ADD3 have been linked to hypertension, neurodevelopmental disorders, and cancer. However, no comprehensive in silico saturation mutagenesis study has systematically evaluated the pathogenic potential and structural consequences of all possible missense mutations in adducins. This study aimed to identify high-risk variants and their potential impact on protein stability and function. Methods: We performed computational saturation mutagenesis for all possible single amino acid substitutions across the adducin proteins family. Pathogenicity predictions were conducted using four independent tools: AlphaMissense, Rhapsody, PolyPhen-2, and PMut. Predictions were validated against UniProt-annotated pathogenic variants. Predictive performance was assessed using Cohen’s Kappa, sensitivity, and precision. Mutations with a prediction probability ≥ 0.8 were further analyzed for structural stability using mCSM, DynaMut2, MutPred2, and Missense3D, with particular focus on functionally relevant domains such as phosphorylation and calmodulin-binding sites. Results: PMut identified the highest number of pathogenic mutations, while PolyPhen-2 yielded more conservative predictions. Several high-risk mutations clustered in known regulatory and binding regions. Substitutions involving glycine were consistently among the most destabilizing due to increased backbone flexibility. Validated variants showed strong agreement across multiple tools, supporting the robustness of the analysis. Conclusions: This study highlights the utility of multi-tool bioinformatic strategies for comprehensive mutation profiling. The results provide a prioritized list of high-impact adducin variants for future experimental validation and offer insights into potential therapeutic targets for disorders involving ADD1, ADD2, and ADD3 mutations. Full article

Traditional PMUT ultrasonic ranging systems usually possess a large measurement blind area under the integrated transmit–receive mode, dramatically limiting its distance measurement in confined spaces, such as when determining the clearance of large bearing components. Here, a broadband PMUT rangefinder was designed by integrating six types of different cells with adjacent resonant frequencies into an array. Through overlapping and coupling of the bandwidths from the different cells, the proposed PMUTs showed a wide –6 dB fractional bandwidth of 108% in silicon oil. Due to the broadening of bandwidth, the device could obtain the maximum steady state with less excitation (5 cycles versus 14 cycles) and reduce its residual ring-down (ca. 6 μs versus 15 μs) compared with the traditional PMUT array with the same cells, resulting in a small blind area. The pulse–echo ranging experiments demonstrated that the blind area was effectively reduced to 4.4 mm in air or 12.8 mm in silicon oil, and the error was controlled within ±0.3 mm for distance measurements up to 250 mm. In addition, a specific ultrasound signal processing circuit with functions of transmitting, receiving, and processing ultrasonic waves was developed. Combining the processing circuit and PMUT device, the system was applied to determine the axial clearance of the main bearing in a tunneling machine. This work develops broadband PMUTs with a small blind area and high resolution for distance measurement in narrow and confined spaces, opening up a new path for ultrasonic ranging technology. Full article

The motivation of this work is to enable the use of piezoelectric micromachined ultrasonic transducer (PMUT)-based implants within the human body for biomedical applications, particularly for power and data transfer for implanted medical devices. To protect surrounding tissue and ensure PMUT functionality over time, biocompatible and hermetic encapsulation is essential. This study investigates the impact of Parylene F-VT4 layers of various thicknesses as well as the effect of multilayer stacks of Parylene F-VT4 combined with atomic layer-deposited nanolayers of Al₂O₃ and HfO₂ on the mechanical and acoustic properties of PMUTs. PMUTs with various diameters (40 µm, 60 µm, and 80 µm) are fabricated and tested both as stand-alone devices and as arrays. The mechanical behavior of single stand-alone PMUT devices is characterized in air and in water using laser Doppler vibrometry (LDV), while the acoustic output of arrays is evaluated by pressure measurements in water. Experimental results reveal a non-monotonic change in resonance frequency as a function of increasing encapsulation thickness due to the competing effects of added mass and increased stiffness. The performance of PMUT arrays is clearly influenced by the encapsulation. For certain array designs, the encapsulation significantly improved the arrays’ pressure output, a change that is attributed to the change in the acoustic wavelength and inter-element coupling. These findings highlight the impact of encapsulation in modifying and potentially enhancing PMUT performance. Full article

Ultrasonic applications such as non-destructive testing, biomedical imaging or range measurements are currently based on piezoelectric bulk transducers. Yet, these kinds of transducers with their mm to cm dimensions are rather impractical in fields in which both frequencies in the kHz region and small-feature sizes are required. This fact mainly relates to the inverse relationship between the resonance frequency constant and the transducers’ dimension, yielding a higher frequency and attenuation with a decreasing size. Piezoelectric micromachined ultrasonic transducers (PMUTs), in comparison, incorporate a small-scale µm design while preserving the operating frequency in the desired kHz range. This contribution presents the detailed manufacturing of such a PMUT with a multiple ring electrode‑based structure to additionally adjust the sound pressure fields. The PMUT will be characterized by its deflection in air along with the characterization of the piezoelectric material lead zirconate titanate (PZT) itself. The measurements showed a maximum polarization of 21.8 µC/cm² at 50 kV/cm, the PMUT’s displacement of 30.50 nm/V in air when all electrodes are driven, and an adjustable deflection via different electrode excitations without the need for additional hardware. The ring design also offered the possibility to emit two distinct frequencies simultaneously. These results demonstrate the potential of the designs for small-feature-size applications as they are in high demand for implantable devices, miniaturized ultrasonic-based communication or drug delivery. Full article