A question re: piezoelectric materials and resonators

AI Thread Summary
The discussion centers on the differences between thin-film bulk acoustic resonators (TFBARs) and piezoelectric micromachined ultrasound transducers (PMUTs), both made from AlN and approximately 1 um thick. Despite their similar structures, TFBARs operate at resonance frequencies of 10-100 MHz, while PMUTs function at 0.5-1 MHz. The conversation highlights the importance of understanding whether a device is specified as a resonator or a transducer, as this can influence its operational mode and frequency characteristics. The mode of operation, including the direction of the electric field and wave propagation, may also contribute to the differences in resonance frequency. Further examination of relevant literature is suggested for deeper insights.
Dishsoap
Messages
1,016
Reaction score
308
TL;DR Summary
Why do bulk acoustic resonators have higher resonant frequencies than PMUTs?
I'm new to the world of acoustics, and I've been reading up on various methods for wireless communication/sensing through ultrasound, especially with piezoelectric materials such as AlN. Fundamentally, I can't seem to find a difference between thin-film bulk acoustic resonators (1 um thick) and PMUTs, which are also about 1 um thick in AlN. They have similar structures (top and bottom electrode, sometimes suspended), and yet the resonance frequency of a PMUT is about 0.5-1 MHz and 10-100 for a TFBAR. I think I am missing something fundamental but I cannot figure out what.
 
Engineering news on Phys.org
PMUT = Piezoelectric micromachined Ultrasound Transducer. 0.5-1 MHz.
TFBAR = thin-film bulk acoustic resonators. 10-100 MHz. Both 1 um thick.

Is the device being specified as a resonator or a transducer?
Maybe the resonant frequency of TFBAR is being compared with the bandwidth of the loaded PMUT.
 
  • Informative
Likes berkeman
Baluncore said:
Is the device being specified as a resonator or a transducer?

I think that is where I am misunderstanding - I don't see why it matters. The geometry, thickness etc. can be the same, but why would the resonance frequency change depending on whether it is being used as a resonator or a transducer? In both cases, an acoustic wave is being converted into an AC voltage, right?
 
Dishsoap said:
In both cases, an acoustic wave is being converted into an AC voltage, right?
Yes, or vice versa.
It is also possible that the mode of operation might be different.
See; http://mems.usc.edu/fbar.htm
"A bulk-micromachined FBAR with Thickness Field Excitation () uses a z-directed electric field to generate z-propagating longitudinal or compressive wave. In an LFE-FBAR, the applied electric field is in y-direction, and the shear acoustic wave (excited by the lateral electric field) propagates in z-direction, as illustrated ()"
 
Baluncore said:
Yes, or vice versa.
It is also possible that the mode of operation might be different.
See; http://mems.usc.edu/fbar.htm
"A bulk-micromachined FBAR with Thickness Field Excitation () uses a z-directed electric field to generate z-propagating longitudinal or compressive wave. In an LFE-FBAR, the applied electric field is in y-direction, and the shear acoustic wave (excited by the lateral electric field) propagates in z-direction, as illustrated ()"

Oh, that could be - I'll have to examine these papers further. Thank you!
 
  • Like
Likes berkeman

Thread 'Bubble formation in 4 mm gap vessel'

How did you find PF?: Via Google search Hi, I have a vessel I 3D printed to investigate single bubble rise. The vessel has a 4 mm gap separated by acrylic panels. This is essentially my viewing chamber where I can record the bubble motion. The vessel is open to atmosphere. The bubble generation mechanism is composed of a syringe pump and glass capillary tube (Internal Diameter of 0.45 mm). I connect a 1/4” air line hose from the syringe to the capillary The bubble is formed at the tip...
View full post »
Thread 'Physics of Stretch: What pressure does a band apply on a cylinder?'

Thread 'Physics of Stretch: What pressure does a band apply on a cylinder?'

Scenario 1 (figure 1) A continuous loop of elastic material is stretched around two metal bars. The top bar is attached to a load cell that reads force. The lower bar can be moved downwards to stretch the elastic material. The lower bar is moved downwards until the two bars are 1190mm apart, stretching the elastic material. The bars are 5mm thick, so the total internal loop length is 1200mm (1190mm + 5mm + 5mm). At this level of stretch, the load cell reads 45N tensile force. Key numbers...
View full post »

Thread 'Find 3D Printer & Software Resources for Prototype Creation'

I'd like to create a thread with links to 3-D Printer resources, including printers and software package suggestions. My motivations are selfish, as I have a 3-D printed project that I'm working on, and I'd like to buy a simple printer and use low cost software to make the first prototype. There are some previous threads about 3-D printing like this: https://www.physicsforums.com/threads/are-3d-printers-easy-to-use-yet.917489/ but none that address the overall topic (unless I've missed...
View full post »

Similar threads

Resonant frequency of Piezoelectric material
Replies
10
Views
3K
Relation between electrical and mechanical resonant frequency
Replies
11
Views
13K
A In light of new evidence, what might be behind the Casimir Effect?
Replies
46
Views
4K
I Are Evanescent Gravitational Waves Measurable
Replies
20
Views
2K
Could New Materials Propel China's Industry to Bill Gates-Level Success?
Replies
4
Views
10K
Experimental demonstration of existence of atoms
Replies
7
Views
3K
Birefringence and Automotive Window Tinting
Replies
9
Views
8K
Civilization of millions of rings.
Replies
3
Views
4K

Hot Threads

Recent Insights

Back
Top