Large Area Printed Piezosensors For Wearable Applications

Large Area Printed Piezosensors For Wearable Applications

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Description: Body motion detection via textiles, health, and sports applications, robust, affordable, easy to use. Technology: - Fabrication: Process - screenprinting of multiple layers, drying at low temperatures (120C), poling step necessary. Fabrication: Inks-electrode pastes commercial available, P(VDF-TrFE) ink own patented process [3], solvents nontoxic.

 
Author: Timo Grunemann  | Visits: 148 | Page Views: 218
Domain:  High Tech Category: Semiconductors 
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Contents:
Large area printed piezosensors
for wearable applications

Timo Grunemann

© Fraunhofer

Motivation

 body motion detection
via textiles

 health and sports
applications

 robust
 affordable
 easy to use

© Fraunhofer

!

Concept of Sensor
Flexible multilayer system

 piezoelectric layer between
electrodes

 bending  change in layer
thickness  voltage output

 no external voltage source
needed
U

© Fraunhofer

Technology

 electrodes: PEDOT:PSS

 piezoelectric: P(VDF-TrFE)
 flexible
 biocompatible (ISO 10993-5)

F F

[

C

δ-

C

F F

]

]

Materials

H H δ+

[1,2]

P (VDF

-

[1] Beloti, M. , et.al, J. Biomed. Mater. Res., 79A: 282–288 (2006).
© Fraunhofer

C

[2] R. M. Miriani, et al., 30th Annual International Conference of the IEEE
Engineering in Medicine and Biology Society, pp. 1841-1844 (2008).

C
F

TrFE)

]
H

Technology
Fabrication: Process

 screenprinting of multiple
layers

 drying at low temperatures
(120°C)

 poling step necessary
u(C=O)Ester= 1720-1740 cm-1

© Fraunhofer

Technology
Fabrication: Inks

 electrode paste
commercial available

 P(VDF-TrFE) ink own
patented process [3]

shear rates

10 1/s

100 1/s

 solvents non toxic

© Fraunhofer

[3] EP 2609142 A1

Sensor Design

 large area
 sensor array
 wrist and ellbow
 bending and twisting
 temperature calibration

© Fraunhofer

Sensors on PET
Prints

 prints on 125 µm PET foil
 4 layers
 silver lines for standard connector
 sensor thickness approx. 7µm

© Fraunhofer

Sensors on PET
Output

 bending tests with different
velocities

 mV output voltage
 output profile constant

© Fraunhofer

55
45
35
25
15
5
-5
-15
t/s 0

d/mm
U/mV

25

50

75

100

125 150
Hunderte

Sensors on PET
Bendtype
Output

15

5

U / mV

U / mV

determined
by bend direction

10

12

 voltage direction

14
10

0
-5 -4 -3 -2 -1 0
-5

8
6
4

-15

0
-2

0

20

40

d/mm

4

5

10

-6
-8
-10
-14

v / mm/s

15

-4

-12

Bendtype

-5

5

-4

-3

-2

0
-1 0
-5

1

-10
-15

v / mm/s

© Fraunhofer

3

60

U / mV

 linear output region

U / mV

-20

2

-10

2

1

2

3

4

5

Sensors on PET
Output

 Video

© Fraunhofer

Sensors on Textiles
R/ ~ 2500 Ω/sq
Raw printing

 protruding textile fibers 
breakdown

 use of cleanroom textiles

 electrode layer sheet resistance
very high

 PVDF layer adopts textile structure
after drying

 low reproducibility

© Fraunhofer

4 mm

Sensors on Textiles
Planarization layers

 several materials tested
 printing of electrodes difficult
 fluor based polymer worked
 planarization thickness ≈ 73 µm
Rq= 91 µm
© Fraunhofer

Rq= 8 µm

Sensors on Textiles
Sensors on planarized textiles

 sensors working
 still defects during electrode

 sensor evaluation has to be
optimized

 ongoing research

© Fraunhofer

3
2
1
0
-1
-2
-3
-4

U / mV

printing

0

5

10

15
Time [s]

20

25

Sensors on Textiles
Washing test

 machine wash 30 C° 1h
 standard laundry detergent
 spin dried

 uncoated sensors dissolve
partially sensor broken

 fluor polymer toplayer
 sensor still works

© Fraunhofer

Before

After

Outlook
Topics to address

 pyroelectric effect (nanoparticles)
 enhanced planarization
 advanced characterization

 enhance sensor output

 enable feedback

NP-PVDF films
Force (MPa)

 aging test (ongoing)

E = 1450  72 MPa
Elongation (mm)

© Fraunhofer