energy harvester designs inspired from fractal geometries · energy harvester designs inspired from...

Research Institutes of Sweden

ENERGY HARVESTER DESIGNS

INSPIRED from

FRACTAL GEOMETRIES

Micro Energy 2017, 3 – 7 July, Gubbio

* RISE Acreo AB, Sensor Systems, Gothenburg, Sweden

** Chalmers University of Technology, Electronics Materials and Systems LaboratoryGothenburg, Sweden

Cristina Rusu*, Agin Vyas**, Fredrik Ohlsson*


smart-MEMPHIS H2020 project - Vision

© LivaNova Reproduced with permission

From traditional to leadless, implant and forget pacemaker

Wireless sensor network for structural health monitoring


smart-MEMPHIS project - pacemaker


Data for EH requirements - Epicardial LV Heart Motion in human

• 6 mm diameter, 20 - 40 mm capsule length, titanium.

• 5 years → 10 - 20 years power autonomy

• Placing accelerometers onto / into heart - vibration energy at lower frequencies (5 to 50 Hz).

• Commonly assumed that about 2 - 5 μJ per beat are available & required for powering the

pacemaker functionalities.

SeismoCardioGram (SCG) in

human

Epicardial LV Heart Motion in human


Energy sources inside the body / near the heart

Substantial, Permanent

Mechanical

Vibrations

Transducer [1-3]

Heart movementsBlood pressure

Pressure variations

Heartbeat waveform

Transducer [5]

Transducer [4]

[1] H. Goto et al., Feasibility of using the automatic generating system for quartz watches as a leadless pacemaker power source, Med. Biol. Eng. Comput., vol. 37, no. 3, pp. 377–380, 1999.[2] R. Tashiro et al., Development of an electrostatic generator for a cardiac pacemaker that harnesses the ventricular wall motion,” J. Artif. Organs, vol. 5, no. 4, pp. 0239–0245, 2002.[3] M. A. Karami et al., Powering pacemakers from heartbeat vibrations using linear and nonlinear energy harvesters,” Appl. Phys. Lett., vol. 100, no. 4, pp. 042901-1–042901-4, 2012.[4] M. Deterre et al., Micro Blood Pressure Energy Harvester for Intracardiac Pacemaker, JMEMS VOL. 23, NO. 3, JUNE 2014, p.651-660.[5] G-T. Hwang et al., Self-Powered Cardiac Pacemaker Enabled by Flexible Single Crystalline PMN-PT Piezoelectric Energy Harvester, Adv. Mater. 2014, 26, 4880–4887.

Muscle contraction


Assumption for EH requirements

z = deflectionm = proof mass – 1gk = spring constantΓ = acceleration due to pulse

Calculated MECHANICAL ENERGY


Energy estimates

f = 10 Hz

Excitation - pulsed @ 60 BPM

(literature sinusoidal continuous)Conventional design & MEMS PZT not an easy option…


Excitation - pulsed @ 60 BPM, all literature references are sinusoidal continuous

Standard designs are associated with large out-of-plane displacements and/or low power yield;

Most promising design is transfer of inertial energy from proof mass responsive pulse (potential for bandwidth

increase);

Design specifications require much heavier proof mass than silicon;

Proof-mass has to be quite large (ca. 3mm x 3mm x 1-3mm);

Literature…

Conventional design & MEMS PZT not an easy option…

Reference Active area

[mm2]

Active volume

[mm3]

Accel

[g]

Frequency

[Hz]

Power

[𝜇W]

Vibration

driving

Manufacturing

Morimoto 2010 92.5 0.26 0.5 126 5.3 harmonic Stainless steel sheet + 2mm pzt; no mass

Fang 2006 2.65 0.78 1 608 2.16 harmonic

S.B. Kim 2013 - 1.063 0.5 243 2.33 harmonic

M. Kim 2013 - 0.608 0.5 78.7 0.34 harmonic Si harvester +Si mass + 1.2mm PZT

E.E. Aktakka2011

- 27 (7x7x0.55) 0.1

1

167

155

2.74

~100

harmonic Si structure + W mass (5x7x0.5) + 20mm PZT

H. Dorou 2010 - 1.9 0.1

0.2

77

76

3.2

14

harmonic Si structure + W mass (15x5) + 200mm PZT

Smart-

Memphis

21 0.6 0.5 10-30 1-5 pulse


Fractals – definitions….

Koch curve

1 D

D = 1.2619

Mathematical (Koch curve) Natural

Corrosion front 2D

D = 1.33

2 D

• A fractal curve is a fractured line formed by connected segments, obtained by a specific iteration algorithm that

has the property of increasing the length of the curve towards the infinity when iteration is continued to the

infinity. The overall curve is still bound in a limited space.

• A fractal structure (curve) has a geometrical dimension that differ from the well-known Euclidian dimension;

has a non-integer dimension, between 1 and 2.

• Geometrical characters, each part has the same statistical character as the whole - geometrical self-similarity

• Describing partly random or chaotic phenomena such as crystal growth and galaxy formation - statistical self-

similarity

• Ex. - our pulmonary system is a fractal surface that has a surface equal to a tennis-court.

http://en.wikipedia.org/wiki/Koch_curve

http://en.wikipedia.org/wiki/Image:Front_de_percolation.png

http://en.wikipedia.org/wiki/Image:Front_de_percolation.png

http://en.wikipedia.org/w/index.php?title=Corrosion_front_in_2D&action=edit&redlink=1


Fractals – examples….

Fractal antennas - very special properties attractive for the design of multi-band

• broad band operation

• gain is slow varying with frequency

• possible to use one single layout for more than one frequency for different applications

• can operate efficiently at smaller sizes of ordinary antenna

[1] Rusu et al., Minkowski Fractal Microstrip Antenna for RFID Tags, Proc. European Microwave Conference 2008 (EuMC), p. 666-670, Amsterdam, Netherlands.[2] Ghosh et al., A Fractal-Based Photodiode for On-Chip Energy Harvesting, IEEE SENSORS 2010 Conference, 978-1-4244-8168-2/10.

[1]

Photodiode for energy harvesting – fractal-based design perimeter, peripheral response

photoactive area

Fractus

[2]


Fractals – vibration energy harvester

Koch fractal designt_Si = 10 umL = 12 mm, w = 0.5 mm

Mode Frequency [Hz]

1 69

Single support

• Broad band operation

• Multiple frequencies in the low range

• If possible to obtain low frequencies without proof-mass

• Higher strain / better efficiency due to multiple segments resonances…

Double support

Mode Frequency [Hz]

1 302

Our wishes…



30 - 1

F [Hz]

100

510

8E10

1E10

F [Hz]

131

807

7E10

L = 15mm



30 - 1

F [Hz]

100

510

30 - 1.2

F [Hz]

95

583

30 - 1 - 2

8E10

1E10

6E10

7E9

7E10

2E10

3E9

F [Hz]

77

227



Symmetric tree fractal

t_Si = 10 umL_0 = 5 mm, w = 0.5 mmalpha = 60, delta = 1.4

Mode Frequency [Hz]

1 43

2 103

3 330

4 389

5 453

6 1161

Asymmetric tree fractal

t_Si = 10 umL_0 = 5 mm, w = 0.5 mmalpha = 60, delta = 1.4 (1.8)

Mode Frequency [Hz]

1 58

2 161

3 570

4 626

5 767

6 1701

Symmetric tree fractal

Asymmetric tree fractal


Fractals – Symmetric tree – resonances

Mode 3

(330 Hz)

Mode 1

(43 Hz)

Mode 2

(103 Hz)


Fractals – Symmetric tree – stress

Mode 2

(Syy)

Mode 1

(Syy)

Mode 3

(Syy)

Pure bending

N=0

N=1

N=2

N=3

Bending in N=1 branches and Shear in N=0 branch

Combination of bending and shear

Multiple Dipole- next to be tested

4E10

2E10

1E10

3E9

10E10

Mode Frequency

[Hz]

1 42

2 50

3 123

4 126

5 196

6 197

Mode #1 Mode #2

Mode #3 Mode #4

Mode #5


Conclusions

It is not yet properly measured the heart movement regarding vibrations / displacement

and the contribution of its radial, circumferential and longitudinal axes.

Fractal-inspired vibrational energy harvester are promising design because of the variety of forms and

structures that could be produce / found.

So far, we could see:

Possibility to get lower frequencies without addition of proof-mass ↔ extra mass → easier fabrication

Multiple frequencies with increasing number of iterations due to increase of number of branches.

Some correlation between the strain (efficiency) and number of iteration.

• Bending and torsion ↔ non-isotropic piezoelectric material

Continue detailed simulations on fractal structures & MEMS processing in progress

RISE ACREO - Expertise

Sensor Systems

• MEMS

• ELECTROMAGNETIC

• BIO & CHEMICAL

• IMAGING

• WIRELESS / Low power sensors

Micro Energy 2017, 3 – 7 July, Gubbio 21

This work has received funding from The European Union’s Horizon 2020

research and innovation programme under grant agreement No 644378

Thank you!

Prof. Cristina Rusu

RISE Acreo, Sensor Systems, Gothenburg, Sweden

[email protected] +46 709151826

mailto:[email protected]

energy harvester designs inspired from fractal geometries · energy harvester designs inspired from...

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