Tampere University of Technology

Nanocellulose based piezoelectric sensors

CitationTuukkanen, S., Viehrig, M., Rajala, S., & Kallio, P. (2016). Nanocellulose based piezoelectric sensors. 1-2.Paper presented at Advances in Functional Materials (AFM 2016), ICC , Korea, Republic of.

Year2016

Link to publicationTUTCRIS Portal (http://www.tut.fi/tutcris)

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Download date:16.12.2020

Nanocellulose based

piezoelectric sensors

Sampo TuukkanenAssistant Professor (tenure track),

BioMediTech,

Department of Automation Science and Engineering,

Tampere University of Technology (TUT)

Tampere,

FINLAND

Outline

• Nanocellulose fabrication

• Piezoelectricity of wood cellulose

• Nanocellulose film fabrication

• Piezoelectric sensitivity measurements

• Results and conclusions

09.08.2016Sampo Tuukkanen 2

Nanocellulose fabrication

09.08.2016Sampo Tuukkanen 3

[For more details see e.g.: Moon et al., Chemical Society Reviews 40(7) (2007) 3941]

Chemical structure of cellulose:

Cellulose nanocrystal (CNC)

• AFM (atomic force microscope) image

shows that CNCs are highly

crystalline, rigid, rod-like nanoparticles

(nanowhiskers) with a high aspect ratio

1.9.2015Sampo Tuukkanen, TUT, Tampere, Finland 4

[AFM images by S. Tuukkanen, in 2014 at Nanomicroscopy Center, Aalto University, Espoo, Finland]

Diameter

of 5-20 nm

Length of a

few 100 nm

“CNC

nanowhisker”

Piezoelectricity of CNCs

09.08.2016Sampo Tuukkanen 5

000000

00000

00000

25

14

d

d

dmn

[Zuluaga et al. (2013)]

• Piezoelectric effect = Electric charge

separation by applied mechanical force

• The piezoelectric tensor dmn is determined

by the symmetry of a crystal lattice

• The monoclinic C2 symmetry and the

cancellation effects result into

piezoelectric coefficient matrix:

[E. Fukada, J. Phys. Soc. Japan (1955)]

Cellulose crystal

[[C6H10O5]n] unit cell:

Chemical structure of cellulose:

Nanocellulose film fabrication

• Aqueous dispersion of CNF

material (bleached birch cellulose

mass) produced by a mechanical

homogenizing process (6 passes

through a microfibrillator)

• CNF film was prepared by

pressure filtering, followed by

pressing and drying in hot-press

(2 h @ 100 C), resulting a

bendable CNF film containing

amorphous areas and non-

aligned CNC crystals areas

09.08.2016Sampo Tuukkanen 6

[Described in details in: M. Pääkkö et al.

Biomacromolecules 8 (2007) 1934]1 cm

Cellulose

nanocrystals

(CNC)

Amorphous

nanocellulose

[S. Rajala et al, ACS Applied

Materials and Interfaces (2016)]

Permittivity and hysteresis

• Relative permittivity and loss tangent were

similar to typical dielectric polymers

• Polarization-voltage hysteresis curves for

CNF film showed has some level of

ferroelectric properties at high electric fields

09.08.2016Sampo Tuukkanen 7

[S. Rajala et al, ACS Applied Materials and Interfaces (2016)]

CNF sensor assembly

09.08.2016Sampo Tuukkanen 8

PET

Cu

Cu

PET

Nanocellulose film

125 µm

100 nm

100 nm

125 µm

CNF: 45 µm

• For piezoelectric sensitivity measurements, five nominally identical

CNF sensors were assembled

• Pieces of CNF films assembled between two evaporated copper

electrodes on polyethylene terephthalate (PET) substrate using

adhesive film

• Crimp connectors (Nicomatic Crimpflex) were used for getting a

reliable contacts to the copper electrode on flexible PET substrate

[S. Rajala et al, ACS Applied Materials and Interfaces (2016)]

Measurement setup

• Mini-Shaker (Brüel & Kjaer type 4810) used for sensitivity measurements

• Reference sensors for dynamic and static forces (normal direction)

• DUT (device-under-test) placed horizontally on the metal plate

• The sensor sensitivity measure here is closely related to transverse

piezoelectric coefficient d33 (from piezoelectric tensor)

09.08.2016Sampo Tuukkanen 9

[For details see: S. Tuukkanen et al., Synthetic

Metals (2012) or IEEE Sensors (2015)]

Sensitivity measurements

• Static force of ~3 N was used to keep

sample steady

• Excitation with 2 Hz sinusoidal input signal

of 1 V (peak to peak) results in a dynamic

force of ~1.3 N

• Excitation by applying the force in the middle

of the sensor; measurement repeated 3-9

times from both sides, resulting in a total of

6-18 excitations per sensor

• The sensor sensitivity by dividing the

generated charge by the dynamic force

• The unit of sensitivity is pC/N

09.08.2016Sampo Tuukkanen 10

Sensor

sample

Piezoelectric sensitivity

09.08.2016Sampo Tuukkanen 11

• Mean piezoelectric sensitivity

± standard deviation for

excitations from each side of the

CNF-sensors are shown in the

Table 1

• Sensitivity from different

excitation positions for the

CNF sensor and a

polyvinylidene fluoride (PVDF)

reference sensor shows only

small variations

• The average sensitivity for the

CNF sensor was 4.7 pC/N, while

for the reference PVDF sensor

was 27.5 pC/N

[S. Rajala et al, ACS Applied Materials and Interfaces (2016)]

Sensor linearity and hysteresis

• Plots show (a) nonlinearity and (b)

hysteresis curves for the CNF and

the PVDF reference sensor

• Nonlinearity (charge vs. force

curve by fitting a first degree

polynomial via least-squares

minimization) was found to be

(0.86 ± 0.48) pC for CNF and

(6.47 ± 3.76) pC for PVDF

• Sensor hysteresis (with

increasing vs. descreasing force)

was below 1 pC in maximum for

both sensors

09.08.2016Sampo Tuukkanen 12

[S. Rajala et al, ACS Applied Materials and Interfaces (2016)]

Nonlinearity

Sensor hysteresis

Conclusions and summary

09.08.2016Sampo Tuukkanen 13

• Prepared self-standing 45-μm-thick cellulose nanofibrils (CNF) showed piezoelectric

sensitivity of 4.7 ± 0.9 pC/N

Not (intentionally) oriented/polarized, organization by fabrication process possible

Sensitivity values align between quartz (2.3 pC/N) or PVDF (-30 pC/N)

• Nanocellulose is a promising solution-processable, renewable and disposable

piezoelectric material!!

• Ongoing work: Orientation/polarization & Flexibility by mixing with elastomer

[S. Rajala et al, ACS

Applied Materials and

Interfaces (2016)]

Acknowledgements

09.08.2016Sampo Tuukkanen 14

Nanocellulose and film preparation:

Aalto University, Department of Forest Products Technology &

Department of Materials Science and Engineering, Finland

• Maija Vuoriluoto, Dr. student: CNF-film preparation

• Orlando Rojas, Prof: Supervision

• Sami Franssila, Prof: Supervision

Permittivity and hysteresis measurements:

University of Oulu, Microelectronics Research Unit, Finland

• Tuomo Siponkoski, Dr. student: Hysteresis and permittivity

• Jari Juuti, D.Sc. (Tech.), Adj. Prof: Supervision

Film characterisation and sensitivity measurements:

Tampere University of Technology (TUT), Department of

Automation Science and Engineering, Finland

• Satu Rajala, D.Sc. (Tech.): Sensitivity measurements

• Essi Sarlin, D.Sc. (Tech.): SEM imaging

• Marja Mettänen, D.Sc. (Tech.): Image based analysis

• Arno Pammo, B.Sc. (Tech.): Sensor assembly

• Sampo Tuukkanen, Ph.D., Asst. Prof: Supervision

Funding from: