This document summarizes research on developing stretchable and wearable ultrasound transducers using piezoelectric materials. It discusses using piezoelectric effects to generate ultrasound pulses for imaging and sensing applications. The goal is to create soft, flexible transducers that can conform to the body. Challenges include matching acoustic impedance between layers and achieving high stretchability. Experiments tested prototype devices on aluminum blocks and investigated copper wire designs and stretchability up to 68.5% strain. Future work will optimize wire designs and test different wire thicknesses to achieve the target of 100% strain for truly wearable and stretchable ultrasound transducers.

1. Wearable/ Stretchable
Ultrasound Transducers
Using Piezoelectric Material
by Melissa Nguyen
University of California, San Diego
Summer Research Conference

2. Ultrasound transducers
In 1880, Jacques and Pierre Curie
discovered piezoelectricity.
➢ Used in applications, such as eye
imaging, intravascular imaging,
blood flow measurement…
➢ Applied many concepts: piezoelectric
effect, magnetostriction and
photoacoustic effect.

3. Piezoelectric Effect: Polarization charges are induced in
response to an external mechanical stress
nec-tokin.com

4. Electronic pulse → Transducer → Ultrasound Pulse
Ultrasound pulse is reflected by human tissues, bones
→ Echo Pulse → Electric signal → Image
www.sprawks.org

5. Problem with Current Ultrasound Devices:
Rigid Transducer Probes
cdn2.kevinmd.com/www.news-medical.net
amerisoundmedical.com

6. Goal: Develop a piezoelectric material based soft
ultrasound transducers which can be integrated
with the human body
Wearable/
Stretchable devices
nanowerk.com

7. Challenges: Acoustic Impedance
- Backing layer: mechanical support and
allows acoustic energy flowing into the
sample to be absorbed.
- Front matching layer: improve the
energy transmission between active
layer and load medium.
ndk.com

8. Device Fabrication: ACF cable vs. Copper wire
Lin Zhang, “Fabrication steps for soft ultrasound
devices” [Presentation slides], 2016
Active Layer
Backing Layer
Ecoflex
Wire
Device cross sectional area

9. Test on Aluminum block
Pulser/Receiver
T/R R
Oscilloscope
Al block
Ch 1
Ch 2
Transmitter Receiver
Velocity of sound in aluminum
= 6100 m/s

10. Test on Aluminum block
Top view: Sample ultrasound
device was placed on Al block
Front view: The defect on
Al block
Velocity of sound in aluminum
= 6100 m/s

11. Fabrication of Copper Wire
Laser cut on Cu layer (5 µm
thick) and PDMS 1:20
Peel off the outside layer to
reveal the wire patterns

12. Fabrication of Copper Wire
PDMS part A : B Adhesion
1:10 Poor
1:20 Good
1:30 Too high
- Copper foil (5 µm thick) and PDMS layer
were activated using UV ozone at for 2
mins.
- The adhesion between Cu foil and PDMS
depending on PDMS adhesion.

13. Copper wire designs
❖ Considerations:
➢ Stress
➢ Strain
❖ Tests:
➢ In planar
➢ Bending/ stretching configuration

14. Stretchability Test
Break pointBefore stretching

15. Stretchability Test
Serpentine
+ Ecoflex
Serpentine
L 39 7
L’ 61.6 11.8
ΔL 22.6 4.8
Strain 57.9% 68.5%
Acceptable: 60% Strain
Goal: 100% Strain
⇒ Test using different thicknesses
of Cu wires (10, 15, 20 µm)
Unit: mm

16. Future Work
- Optimize a design for copper
wire
- Stretchability test on different
thicknesses of Cu wires
- Eliminate noise and
interference for better signals
THANK YOU FOR LISTENING!
QUESTIONS?

17. Thank you...
Professor Xu Sheng
Post-graduate: Lin Zhang
AEP Advisor: Sophia Tsai
Academic Enrichment Program (AEP)
New Scholarship Donor
...for making this research opportunity possible!