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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Plasma-Assisted Epitaxy of Piezoelectric Sc x Al 1-x N Films on Sapphire for Use in Harsh-Environment Microwave Acoustic Sensors

The Sc x Al 1-x N wurtzite structure has been shown theoretically and experimentally to exhibit significantly higher piezoelectric coupling compared to pure AlN. In this work, a plasma-assisted epitaxial growth method has been used to synthesize epitaxial (0002) Sc x Al 1-x N films on c-sapphire substrates from x = 0.07 to 0.30 by co-evaporating high-purity Sc and Al sources in the presence of a nitrogen plasma generated by an RF plasma source. Epitaxial Sc x Al 1-x N films with highly oriented (0002) grains and in-plane registry were produced on c-sapphire substrates that were pre-exposed to the nitrogen plasma to form an oxynitride seed layer. Growth of Sc x Al 1-x N films was carried out at 930°C under both metal-rich and N-rich conditions using precisely controlled Sc, Al, and N-plasma fluxes. Metal-rich depositions yielded non-(0002)-oriented Sc x Al 1-x N grains and intermetallic ScAl grains. Nitrogen-rich growth with a Sc/Al flux ratio of 1/3 produced the best (0002) epitaxy as determined by x-ray diffraction analysis. Surface acoustic wave resonator (SAWR) devices were fabricated from 500-nm-thick Sc x Al 1-x N and AlN films to extract their electromechanical coupling coefficients, k 2 . As the Sc concentration in the films increases, the degree of (0002) epitaxy is reduced, yet the value of k 2 increases becasue there is more Sc in the wurzite lattice despite the decreased level of (0002) grain alignment. As a result, the use of a 10-nm-thick Si x N y capping layer on top of the Sc x Al 1-x N films aids in preventing etching during SAWR device photolithography and also helps hinder film oxidation up to 800°C.

36 MATERIALS SCIENCE↗
DOE OSTI2023

TEAMER - Acoustic Particle Velocity Measurements - CRADA 601 (Abstract)

With relatively few deployments of tidal turbines, the extent and effect of underwater sounds generated from these turbines is not well understood. The University of Washington (UW) is deploying a cross-flow turbine system, the Turbine Lander, in the entrance channel to Sequim Bay. The deployment of this system provides an opportunity to understand the noise radiated by the turbine and its sources. There are three hypothesized sound sources associated with operation of the turbine: 1) a continuous tone associated with energized power electronics; 2) sound associated with the generator when the turbine is rotating; and 3) sound associated with the bearing pack that supports the rotor. PNNL is collaborating with UW and Integral Consulting Inc. (Integral) to simultaneously measure sound sources using three different devices. The NoiseSpotter®, an acoustic sensor system designed by Integral, measures acoustic pressure and a three-dimensional particle velocity vector. The NoiseSpotter, along with a commercial-off-the-shelf acoustic particle motion and pressure sensor (M20-105, Geospectrum Technologies Inc.) owned by PNNL will be deployed on the seabed approximately 50-100 m from the Turbine Lander. UW will concurrently deploy Drifting Acoustic Instrumentation SYstems (DAISYs) to characterize acoustic pressure near the Turbine Lander and localize sounds using a Time Delay of Arrival (TDOA) algorithm. Integral, UW, and PNNL will collaborate on data analysis and interpretation, with the intention of jointly authoring an archival paper on the results. The noise generated from the Turbine Lander is not expected to be significant, yet this experiment will help to evaluate the efficacy of combining technologies to characterize noise and provide insights for approaches to consider for future turbine deployments at other locations.

16 TIDAL AND WAVE POWER↗
DOE OSTI2023

Vertical Etching of Scandium Aluminum Nitride Thin Films Using TMAH Solution

A wide bandgap, an enhanced piezoelectric coefficient, and low dielectric permittivity are some of the outstanding properties that have made Sc x Al 1-x N a promising material in numerous MEMS and optoelectronics applications. One of the substantial challenges of fabricating Sc x Al 1-x N devices is its difficulty in etching, specifically with higher scandium concentration. In this work, we have developed an experimental approach with high temperature annealing followed by a wet etching process using tetramethyl ammonium hydroxide (TMAH), which maintains etching uniformity across various Sc compositions. The experimental results of etching approximately 730 nm of Sc x Al 1-x N (x = 0.125, 0.20, 0.40) thin films show that the etch rate decreases with increasing scandium content. Nevertheless, sidewall verticality of 85°~90° (±0.2°) was maintained for all Sc compositions. Based on these experimental outcomes, it is anticipated that this etching procedure will be advantageous in the fabrication of acoustic, photonic, and piezoelectric devices.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Generation and enhancement of surface acoustic waves on a highly doped p-type III-V semiconductor substrate

A device employing the generation and enhancement of surface acoustic waves on a highly doped p-type III-V semiconductor substrate (e.g., GaAs, GaSb, InAs, or InGaAs). The device includes two SiO 2 /ZnO islands, each including a SiO 2 buffer layer deposited on the doped p-type III-V semiconductor substrate and a ZnO layer deposited on the SiO 2 buffer layer. An input interdigital transducers (IDT) and an output IDT are each patterned on one of the SiO 2 /ZnO islands. The IDTs generates surface acoustic waves along an exposed surface of the highly doped p-type III-V semiconductor substrate. The surface acoustic waves improve the photoelectric and photovoltaic properties of the device. The device is manufactured using a disclosed technique for propagating strong surface acoustic waves on weak piezoelectric materials. Also disclosed is a photodetector developed using that technique.

Dong, Boqun↗
DOE OSTI2020

Chapter 10 Supplement. Environmental Monitoring Technologies and Techniques for Detecting Interactions of Marine Animals with Marine Renewable Energy Devices

The Chapter 10 Supplementary Material provides information on instrument classes used for monitoring marine renewable energy devices such as passive acoustics, active acoustics, and video cameras. It also describes the applications and challenges of video cameras, and provides a technical glossary related to monitoring terminologies.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Conducting metal oxides integrated with the surface acoustic wave (SAW) sensor platform

One or more embodiments relates a single port surface acoustic wave sensor (SAW) device adapted for use in a wide range of operational temperatures and gas phase chemical species. The device includes a piezoelectric crystal substrate; at least one interdigitated electrode/transducer (IDT) positioned on the piezoelectric crystal substrate; and at least one conducting metal oxide film positioned on the piezoelectric crystal substrate and in communication with at least the IDT.

Ohodnicki, Jr., Paul R.↗
DOE OSTI2023

Cloud Atlas: An Interactive Apparatus for Air Quality Awareness

This paper introduces a research project of a kinetic apparatus that translates collected air quality data to users. The kinetic mechanical skeleton is embedded with processors and electronics, and constantly changes its form according to air quality data collected online via a web crawler. By translating invisible environmental conditions, such as air quality data into morphological, colorful, and acoustic changes for the device, the participants can be aware of the phenomenon of air pollution in real time. The interac- tions between participants' movements and the changes of the device imply how human behaviors can affect the state of the atmosphere. As a result, the device evokes public awareness and participation in environmental issues through tangible experiences. This research aims to explore a new kind of responsive architecture that acts as a medium between invisible environments and inhabitants.

Zhao, Xiaoxiao↗
DOE OSTI2022

An implantable biomechanical energy harvester for animal monitoring devices

Insufficient service life and the resulting need for battery replacements have been a great challenge for implantable electronic devices. This is particularly true for animal tracking applications, because recapturing animals is often unlikely once they are released to the wild. To tackle this problem, we developed a biomechanical energy harvester that uses a Macro Fiber Composite™ (MFC) piezoelectric beam to harvest the mechanical energy from animals’ body bending movements as the power source for implantable and wearable devices. Prototypes of an underwater acoustic transmitter using this technology were subdermally implanted into juvenile white sturgeon and their energy harvesting performance was evaluated through the device’s transmissions. Additionally, the fish successfully recovered from the implantation surgery and freely swam inside a tank. The transmitter prototypes in the fish continually transmitted signals for a period up to 5 weeks. A benchtop test setup was also created to emulate the fish’s body bending, estimate the device’s energy harvesting performance in the live fish, and perform accelerated fatigue testing of the energy harvester by applying test parameters learned from a video study of the fish’s body movement and behavior characteristics. The gradual depolarization of the piezoelectric ceramic material in the MFC under cyclic mechanical loading was the main limiting factor for the life span of the energy harvester. Pathways for improvement are proposed to achieve long-term efficacy of powering implantable and wearable electronic devices.

42 ENGINEERING↗
DOE OSTI2021

Surface Acoustic Wave Sensors for Refrigerant Leak Detection: Compact, Inexpensive, Selective and Sensitive Sensors

Pacific Northwest National Laboratory (PNNL), in collaboration with Parker and Hannifin, is developing a compact, inexpensive, and highly sensitive and selective surface acoustic wave sensor coated with fluorophillic sorbent for detecting fluorocarbon leaks from HVAC systems. Having a highly effective sorbent sensitive to fluorocarbon refrigerant vapors provides a means to develop a sensing device for leak detection. Surface acoustic wave (SAW) sensors with a gas sensing film deposited between the delay lines or on the interdigital transducer have been used to detect gas and vapor molecules in harsh environments with high sensitivity. As part of this project, PNNL screened several sorbent materials that are shown to be selective towards fluorocarbon refrigerant (R32) molecule. The identified sorbent materials were synthesized, characterized, and tested towards R32 using various spectroscopic technique. Next, the sorbent material was coated on a SAW sensor as a thin film using vapor deposition and drop coating methods. The coated thin film was further characterized and tested towards the detection of pure R32 and R32 in ambient air at room temperature to demonstrate the SAW response towards R32 in presence of other competing gases and vapors in air.

42 ENGINEERING↗
DOE OSTI2020

Non-reciprocal transmission of microwave acoustic waves in nonlinear parity–time symmetric resonators

Acoustic waves are versatile on-chip information carriers that can be used in applications such as microwave filters and transducers. Nonreciprocal devices, in which the transmission of waves is non-symmetric between two ports, are desirable for the manipulation and routing of phonons, but building acoustic non-reciprocal devices is difficult because acoustic systems typically have a linear response. Here, we report non-reciprocal transmission of microwave surface acoustic waves using a nonlinear parity–time symmetric system based on two coupled acoustic resonators in a lithium niobate platform. Furthermore, owing to the strong piezoelectricity of lithium niobate, we can tune the gain, loss and nonlinearity of the system using electric circuitry. Our approach can achieve 10 dB of non-reciprocal transmission for surface acoustic waves at a frequency of 200 MHz, and we use it to demonstrate a one-way circulation of acoustic waves in cascading non-reciprocal devices.

42 ENGINEERING↗
DOE OSTI2021

Focusing transformers/filters in isotropic/anisotropic piezoelectrics

A focusing interdigital transducer (IDT) and corresponding single- and dual-port piezoelectric devices are disclosed. The focusing interdigital transducer, which generates Lamé acoustic waves, permits operation at significantly higher frequencies than those possible with traditional IDTs. The focusing IDT employs multiple arced fingers formed both above and below the piezoelectric layer to improve coupling efficiency by coupling through both the e31 and e33 piezoelectric coefficients to the piezoelectric layer. By optimizing both anchor design and location, acoustic wave losses are minimized, thereby improving the device's quality factor Q. Through proper bus design and selection of the number of IDT fingers, a device's impedance can be tuned for a given application. The focusing IDTs may be used in single-port filter devices and dual-port transformer devices. The single- and dual-port devices may operate at a single frequency, at two frequencies, or over a band of frequencies.

Siddiqui, Aleem↗
DOE OSTI2024

Wireless Frequency‐Multiplexed Acoustic Array‐Based Acoustofluidics

Abstract Acoustofluidics has shown great potential in enabling on‐chip technologies for driving liquid flows and manipulating particles and cells for engineering, chemical, and biomedical applications. To introduce on‐demand liquid sample processing and micro/nano‐object manipulation functions to wearable and embeddable electronics, wireless acoustofluidic chips are highly desired. This paper presents wireless acoustofluidic chips to generate acoustic waves carrying sufficient energy and achieve key acoustofluidic functions, including arranging particles and cells, generating fluid streaming, and enriching in‐droplet particles. To enable these functions, the wireless acoustofluidic chips leverage mechanisms, including inductive coupling‐based wireless power transfer (WPT), frequency multiplexing‐based control of multiple acoustic waves, and the resultant acoustic radiation and drag forces. For validation, the wirelessly generated acoustic waves are measured using laser vibrometry when different materials (e.g., bone, tissue, and hand) are inserted between the WPT transmitter and receiver. Moreover, the wireless acoustofluidic chips successfully arrange nanoparticles into different patterns, align cells into parallel pearl chains, generate streaming, and enrich in‐droplet microparticles. This research is anticipated to facilitate the development of embeddable wireless on‐chip flow generators, wearable sensors with liquid sample processing functions, and implantable devices with flow generation and acoustic stimulation abilities for engineering, veterinary, and biomedical applications.

Li, Jiali↗
DOE OSTI2025

A Computational Framework to design 3D stiffness gradient acoustic metamaterials for impedance matching

Acoustic waves play a crucial role in various applications, including medical imaging, non-destructive testing, and sonar systems. One of the significant challenges in these applications is impedance matching, which is essential for minimizing reflections and maximizing the transfer of acoustic energy between different media. Acoustic metamaterials offer a promising solution to this challenge. In addition to impedance control, gradient stiffness can enhance structural efficiency and enable spatial control of wave propagation, making it a valuable feature in acoustic metamaterial design. In this pa- per, we present our developed computational method to design 3D stiffness gradient acoustic metamaterials for impedance matching. The key steps in our approach include generating initial designs using a periodic covariance function to provide unit cells that are both periodic on the boundaries and randomly formed inside the unit cell. Furthermore, we integrated manufacturing constraints into the design process, ensuring that the structures are interconnected for fabrication. We propose two computational optimization algorithms: GenUnit, based on a non-dominated sorting genetic algorithm (NSGA-II), and MLMatch, which leverages differentiable machine learning. The two approaches are not separate contributions but complementary com- ponents of a unified framework. GenUnit requires no training data and directly interfaces with physics-based simulations, making it highly accurate but slower for large-scale exploration. In contrast, MLMatch is data-hungry during training but, once trained, enables near-instantaneous inference and broad design-space coverage. Together, they form a hybrid strategy: ML- Match rapidly explores the global design space, and GenUnit provides local refinement with high-fidelity accuracy. This balance between training cost, inference time, and precision is the motivation for including both methods in the same study. We applied this dual-algorithm framework to generate two metallic-based metamaterial designs that match the acoustic impedance of water while exhibiting a controlled gradient in stiffness (from stiff to soft). The stiffness gradient is particularly advantageous in applications where one side of the structure must interface with soft or sensitive surfaces, such as human tissue or delicate components. Here, this work paves the way for improved materials in various acoustic applications, particularly in ultrasound devices, by providing better impedance.

Metamaterial↗
DOE OSTI2021

A Fabrication Strategy for Reconfigurable Millimeter–Scale Metamaterials

Rather than depending on material composition to primarily dictate performance metrics, metamaterials can leverage geometry to achieve specific properties of interest. For example, reconfigurable metamaterials have enabled programmable shape transformations, tunable mechanical properties, and energy absorption. While several methods exist to fabricate such structures, they often place severe restrictions on manufacturing materials, or require significant manual assembly. Moreover, these arrays are typically composed of unit cells that are either macro–scale or micro–scale in dimension. Here, the fabrication gap is bridged, and laminate manufacturing is used to develop a method for designing reconfigurable metamaterials at the millimeter–scale, that is compatible with a wide range of materials, and that requires minimal manual assembly. In addition to showing the versatility of this fabrication method, how the use of laminate manufacturing affects the behavior of these multi–component arrays is also characterized. To this end, a numerical model that captures the deformations exhibited by the structures is developed, and an analytic model that predicts the strain of the structure under compressive stress is built. Overall, this approach can be leveraged to develop millimeter–scale metamaterials for applications that require reconfigurable materials, such as in the design of tunable acoustics, photonic waveguides, and electromagnetic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2020

In-situ measurement of irradiation behavior in LiNbO 3

In-situ measurement of LiNbO 3 based surface acoustic wave (SAW) crystal resonator device under irradiation was demonstrated and used to characterize the impact of radiation on physical properties of this material. The resonant frequency of the SAW device was monitored as the output power of the reactor was varied. Upon step increase of the reactor power, a gradual shift in the device’s resonant frequency was observed. This frequency shift initially exhibits a linear growth and eventually reaches an equilibrium value proportional to the reactor power. The observed behavior can be attributed to two competing processes: increase of temperature due to gamma heating or accumulation of irradiation induced defects. In both cases, the response is attributed to changes in the physical properties of LiNbO 3 , particularly the elastic constants. This demonstrated ability to measure materials properties under irradiation is attractive for development of sensors and performing materials science under irradiation.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Dynamic Carrier Modulation via Nonlinear Acoustoelectric Transport in van der Waals Heterostructures

Dynamically manipulating carriers in van der Waals heterostructures could enable solid-state quantum simulators with tunable lattice parameters. A key requirement is the formation of deep potential wells to reliably trap excitations. Here, we report the observation of nonlinear acoustoelectric transport and dynamic carrier modulation in boron nitride-encapsulated graphene devices coupled to intense surface acoustic waves (SAWs) on LiNbO 3 substrates. SAWs generate strong acoustoelectric current densities ( J AE ), transitioning from linear to nonlinear regimes with increasing SAW intensity. In the nonlinear regime, periodic carrier (electrons, holes, or their mixtures) stripes emerge. Using counter-propagating SAWs, we create standing SAWs (SSAWs) to dynamically manipulate charge distributions without static gates. The saturation of J AE , attenuation transitions, and tunable resistance peaks confirms strong carrier localization. Finally, these results establish SAWs as a powerful tool for controlling carrier dynamics in two-dimensional (2D) materials, paving the way for the development of time-dependent quantum systems and acoustic lattices for quantum simulation.

2D materials↗
DOE OSTI2026

Linking international technical specifications for acoustic characterization of marine energy converter sounds with environmental compliance criteria

As new ocean energy technologies emerge and are deployed for testing and operations, sound emissions are a potential concern for environmental effects to marine life. Consistent acoustic measurement and data analysis methods can help promote comparisons of technologies and transferability between project sites. In 2022, acoustic emissions from a prototype scale wave energy converter (WEC) were characterized for a range of environmental conditions and power generation states in the coastal waters off southern California using a set of international technical specifications. Results from the international technical specification analyses were applied to United States regulatory threshold criteria for acoustic impacts to marine mammals and examined in the context of European underwater noise monitoring guidelines. Weighted 24 hour cumulative sound exposure levels SEL24h calculated from the highest power generation state WEC sound pressure levels were often more than 20 dB below threshold criteria for temporary threshold shifts in five relevant marine mammal hearing groups. Following European Union recommendations for analyses and reporting, WEC sound characterization in third octave bands centered at 63 Hz and 125 Hz show clear spatial decay of WEC-generated noise, with more pronounced attenuation at 63 Hz, and a less marked but still detectable gradient at 125 Hz, collectively suggesting a relatively confined acoustic footprint under the observed conditions. The value of the international technical specification approach is highlighted by the isolation of WEC sounds from the surrounding soundscape. This allows for a robust characterization of acoustic emissions through a range of device power generation and sea states. Furthermore, in threshold-based regulatory contexts like the U.S., this facilitates direct evaluation of source contributions, while in broader monitoring frameworks used in the E.U. it provides a reproducible foundation for assessing the contribution of emerging ocean energy technologies to the underwater acoustic environment.

Haxel, Joseph H. (ORCID:0000000273864761)↗
DOE OSTI2021

Separation of nanoparticles via acoustofluidic flow relocation

The present disclosure describes a method of separating particles using a combination of acoustophoresis and acoustic fluid relocation. The disclosure also describes a microfluidic device that can be used to separate particles using a combination of acoustophoresis and acoustic fluid relocation. The disclosure describes methods of separating nanoparticles, microparticles, nanoparticles from microparticles, and micron-sized particles from sub-micron-sized particles.

Piyasena, Menake E.↗