skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Spatial Distribution of Acoustic Radiation Force for Non-Contact Modal Excitation
In modal testing, a common excitation method is a transducer in mechanical contact with the object under test. However, for some structures it is desirable to excite vibrations without physical contact. One promising excitation technique is the acoustic radiation force. However, a challenge in using this technique is that the acoustic radiation force is spread out over a finite-diameter focal region. We describe a method to directly measure the spatial distribution of this force. An ultrasound transducer emitted sine waves with frequencies of, for example f1 = 600.610 kHz and f2 = 600 kHz; the resulting radiation force had a component at the difference frequency f1-f2 = 610 Hz. A MicroAcoustic Instruments BAT6 ultrasound transducer was focused to an approximately 2 mm diameter spot on a 19.6 by 8.1 by 0.37 mm clamped-free brass cantilever with a 610 Hz fundamental frequency. A vibrometer measured the response as this focus spot traversed the edge of the cantilever. This enabled determination of the distribution of the acoustic radiation force being delivered by the transducer. This may be helpful in future studies that involve modeling the force applied to a structure using the acoustic radiation force.  more » « less
Award ID(s):
1300591
PAR ID:
10036798
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
Topics in Modal Analysis & Testing, Volume 10
Volume:
10
Page Range / eLocation ID:
155-162
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; (, Communications Physics)
    Abstract Acoustic tweezers use ultrasound for contact-free manipulation of particles from millimeter to sub-micrometer scale. Particle trapping is usually associated with either radiation forces or acoustic streaming fields. Acoustic tweezers based on single-beam focused acoustic vortices have attracted considerable attention due to their selective trapping capability, but have proven difficult to use for three-dimensional (3D) trapping without a complex transducer array and significant constraints on the trapped particle properties. Here we demonstrate a 3D acoustic tweezer in fluids that uses a single transducer and combines the radiation force for trapping in two dimensions with the streaming force to provide levitation in the third dimension. The idea is demonstrated in both simulation and experiments operating at 500 kHz, and the achieved levitation force reaches three orders of magnitude larger than for previous 3D trapping. This hybrid acoustic tweezer that integrates acoustic streaming adds an additional twist to the approach and expands the range of particles that can be manipulated. 
    more » « less
  2. ; ; ; ; ; (, IEEE)
    This paper presents a mid-air thermal interface enabled by a piezoelectric micromachined ultrasonic transducer (pMUT) array. The two-stage thermal actuating process consists of an ultrasound-transmission process via a pMUT array and an ultrasound-absorption process via porous fabric. The pMUT design employs sputtered potassium sodium niobate (K,Na)NbO3 (KNN) thin film with a high piezoelectric coefficient (d31 ~ 8-10 C/m2) as piezoelectric layer for enhanced acoustic pressure. Testing results show that the prototype pMUT array has a resonant frequency around 97.6 kHz, and it can generate 1970 Pa of focal pressure at 15 mm away under the 10.6 Vp-p excitation. As a result, fabric temperature in the central focal area can rise from 24.2℃ to 31.7℃ after 320 seconds with an average temperature variation rate of 0.023℃/s. Moreover, thermal sensations on the human palms have been realized by the heat conduction through the fabric-skin contact. As such, this work highlights the promising application of pMUT array with high acoustic pressure for human-machine interface, particularly mid-air thermal display. 
    more » « less
  3. ; ; ; ; ; (, 22th International Conference on Solid-State Sensors, Actuators and Microsystems-Transducers 2023)
    This paper presents a mid-air haptic interface device enabled by a piezoelectric micromachined ultrasonic transducer (pMUT) array achieving an unprecedentedly high transmission pressure of 2900 Pa at a 15 mm distance for the first time. The structure is based on sputtered potassium sodium niobate (K,Na)NbO3 (KNN) thin film with a high piezoelectric coefficient (𝑒𝑒31 ~ 8-10 C/m2). A prototype KNN pMUT array composed of 15×15 dual-electrode circular-shape diaphragms exhibits a resonant frequency around 92.4 kHz. Testing results show a transmitting sensitivity of 120.8 Pa/cm2 per volt under only 12 Vp-p excitation at the natural focal point of 15 mm away, which is at least 3 times that of previously reported AlN pMUTs at a similar frequency. Furthermore, an instant non-contact haptic stimulation of wind-like sensation on human palms has been realized. As such, this work sheds light on a new class of pMUT array with high acoustic output pressure for human-machine interface applications, such as consumer electronics and AR/VR systems. 
    more » « less
  4. ; ; (, IEEE Sensors Letters)
    Langfelder, Giacomo (Ed.)
    In this letter, we report on a high-sensitivity whispering gallery mode (WGM) resonator-based air-coupled ultrasound sensor capable of detecting minute pressure variations across an ultrasound frequency spectrum of 0.6–3.5 MHz. The sensor comprises a microspherical glass shell of approximately 450 μm in radius and nonuniform shell thickness of 7–15 μm, which is optically coupled to a tunable laser for resonance excitation. The setup allows for the precise measurement of acoustic signals, benefiting from the high optical Q-factor of ∼2 million of the blown glass microspherical shells. A noise equivalent pressure as low as 40 μPa/ √Hz was obtained at 1.72-MHz ultrasound frequency. A very good correspondence between the simulated axisymmetric resonance frequencies measured using the WGM resonator and a 3D finite-element analysis model in COMSOL was established. The sensor showed an expected linear dependence on the drive voltage of the ultrasound transducer. The distortion of the microspherical shell under acoustic pressure was also independently confirmed using a laser Doppler vibrometer. The sensor’s capability to handle high-frequency ultrasonic waves with significantly better signal-to-noise ratio than conventional piezoelectric- or microphone-based systems is demonstrated, highlighting its suitability for advanced photoacoustic applications. 
    more » « less
  5. ; ; ; (, 2019 American Control Conference (ACC))
    Atomic force microscopes (AFMs) are used not only to image with nanometer-scale resolution, but also to nanofabricate structures on a surface using methods such as dip-pen nanolithography (DPN). DPN involves using the tip of the AFM to deposit a small amount of material on the surface. Typically, this process is done in open loop, leading to large variations in the amount of material transferred. One of the first steps to closing this loop is to be able to accurately and rapidly measure the amount of deposition. This can be done by measuring the change in the resonance frequency of the cantilever before and after a write as that shift is directly related to the change in mass on the cantilever. Currently, this is done using a thermal-based system identification, a technique which uses the natural Brownian excitation of the cantilever as a white noise excitation combined with a fast Fourier transform to extract a Bode plot. However, thermal-based techniques do not have a good signal to noise ratio at typical cantilever resonance frequencies and thus do not provide the needed resolution in the DPN application. Here we develop a scheme that iteratively uses a stepped-sine approach. At each step of the iteration, three frequencies close to the approximate location of the resonance are injected and used to fit a model of the magnitude of the transfer function. The identified peak is used to select three new frequencies in a smaller range in a binary search to reduce the uncertainty of the measured resonance peak location. The scheme is demonstrated through simulation and shown to produce an accuracy of better than 0.5 Hz on a cantilever with a 14 kHz resonance in a physically realistic noise scenario. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email