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Wearable/ Stretchable Ultrasound Transducers
Using Piezoelectric Material
by Melissa Nguyen
University of California, San Diego
Summer Research Conference
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.
Piezoelectric Effect: Polarization charges are induced in response to an external mechanical stress
nec-tokin.com
Electronic pulse → Transducer → Ultrasound Pulse Ultrasound pulse is reflected by human tissues, bones
→ Echo Pulse → Electric signal → Image
www.sprawks.org
Problem with Current Ultrasound Devices:Rigid Transducer Probes
cdn2.kevinmd.com/www.news-medical.net amerisoundmedical.com
Goal: Develop a piezoelectric material based soft ultrasound transducers which can be integrated
with the human body
Wearable/ Stretchable devices
nanowerk.com
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
Device Fabrication: ACF cable vs. Copper wire
Lin Zhang, “Fabrication steps for soft ultrasound devices” [Presentation slides], 2016
Active Layer
Backing Layer
EcoflexWire
Device cross sectional area
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
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
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
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.
Copper wire designs
❖ Considerations:➢ Stress➢ Strain
❖ Tests: ➢ In planar ➢ Bending/ stretching configuration
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% StrainGoal: 100% Strain
⇒ Test using different thicknesses of Cu wires (10, 15, 20 µm)
Unit: mm
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?