ENERGY HARVESTER DESIGNS INSPIRED from FRACTAL GEOMETRIES

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Gothenburg, Sweden ** Chalmers University of Technology, Electronics

1 ENERGY HARVESTER DESIGNS INSPIRED from FRACTAL GEOMETRIES Cristina Rusu*, Agin Vyas**, Fredrik Ohlsson* * RISE Acreo AB, Sensor Systems, Gothenburg, Sweden ** Chalmers University of Technology, Electronics Materials and Systems LaboratoryGothenburg, Sweden Research Institutes of Sweden

2 smart-memphis H2020 project - Vision From traditional to leadless, implant and forget pacemaker LivaNova Reproduced with permission Wireless sensor network for structural health monitoring

3 smart-memphis project - pacemaker

Data for EH requirements - Epicardial LV Heart Motion in human 6 mm diameter, 20-40 mm capsule length,

5 years 10-20 years power autonomy Placing accelerometers onto / into heart - vibration energy at lower

4 Data for EH requirements - Epicardial LV Heart Motion in human 6 mm diameter, mm capsule length, titanium. 5 years 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. Epicardial LV Heart Motion in human SeismoCardioGram (SCG) in human

Energy sources inside the body / near the heart Heartbeat waveform Mechanical Substantial, Permanent Vibrations

Med. Biol. Eng. Comput., vol. 37, no. 3, pp. 377 380, 1999. [2] R. Tashiro et al.

J. Artif. Organs, vol. 5, no. 4, pp. 0239 0245, 2002. [3] M. A. Karami et al.

, vol. 100, no. 4, pp. 042901-1 042901-4, 2012. [4] M. Deterre et al.

5 Energy sources inside the body / near the heart Heartbeat waveform Mechanical Substantial, Permanent Vibrations Heart movements Blood pressure Pressure variations Muscle contraction Transducer [5] Transducer [1-3] 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 , [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 , [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 , [4] M. Deterre et al., Micro Blood Pressure Energy Harvester formicro Intracardiac Energy Pacemaker, 2017, 3 7 JMEMS July, Gubbio VOL. 23, NO. 3, JUNE 2014, p [5] G-T. Hwang et al., Self-Powered Cardiac Pacemaker Enabled by Flexible Single Crystalline PMN-PT Piezoelectric Energy Harvester, Adv. Mater. 2014, 26,

6 Assumption for EH requirements Calculated MECHANICAL ENERGY z = deflection m = proof mass 1g k = spring constant Γ = acceleration due to pulse

7 Energy estimates f = 10 Hz Excitation - 60 BPM (literature sinusoidal continuous) Conventional design & MEMS PZT not an easy option

8 Literature Reference Active area [mm 2 ] Active volume [mm 3 ] Accel [g] Frequency [Hz] Excitation - 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); Power [μw] Vibration driving Design specifications require much heavier proof mass than silicon; Proof-mass has to be quite large (ca. 3mm x 3mm x 1-3mm); Manufacturing Morimoto harmonic Stainless steel sheet + 2mm pzt; no mass Fang harmonic S.B. Kim harmonic M. Kim harmonic Si harvester +Si mass + 1.2mm PZT E.E. Aktakka - 27 (7x7x0.55) harmonic Si structure + W mass (5x7x0.5) + 20mm PZT ~100 H. Dorou harmonic Si structure + W mass (15x5) + 200mm PZT Smart- Memphis pulse Conventional design & MEMS PZT not an easy option

$A fractal curve is a fractured line formed by connected segments, obtained by a specific iteration algorithm that has the property of increasing the length of the curve towards the infinity when$

9 Fractals definitions. 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 selfsimilarity Ex. - our pulmonary system is a fractal surface that has a surface equal to a tennis-court. Mathematical (Koch curve) Natural 1 D Koch curve D = D Corrosion front 2D D = 1.33

$operate efficiently at smaller sizes of ordinary antenna [1] Fractus Photodiode for energy harvesting fractal-based$ design perimeter, peripheral response photoactive area [2] [1] Rusu et al.

design perimeter, peripheral response photoactive area [2] [1] Rusu et al.

10 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] Fractus Photodiode for energy harvesting fractal-based design perimeter, peripheral response photoactive area [2] [1] Rusu et al., Minkowski Fractal Microstrip Antenna for RFID Tags, Proc. European Microwave Conference 2008 (EuMC), p , Amsterdam, Netherlands. [2] Ghosh et al., A Fractal-Based Photodiode for On-Chip Energy Harvesting, IEEE SENSORS 2010 Conference, /10.

11 Fractals vibration energy harvester Broad band operation Our wishes Multiple frequencies in the low range If possible to obtain low frequencies without proof-mass Higher strain / better efficiency due to multiple segments resonances Koch fractal design t_si = 10 um L = 12 mm, w = 0.5 mm Single support Double support Mode Frequency [Hz] Mode Frequency [Hz]

12 Fractals vibration energy harvester L = 15mm 1E E10 F [Hz] F [Hz] E10

Fractals vibration energy harvester 30-1 1E10 30-1.

13 Fractals vibration energy harvester E E E9 F [Hz] 8E10 F [Hz] 6E10 F [Hz] 2E10 7E

14 Fractals vibration energy harvester Symmetric tree fractal t_si = 10 um L_0 = 5 mm, w = 0.5 mm alpha = 60, delta = 1.4 Asymmetric tree fractal t_si = 10 um L_0 = 5 mm, w = 0.5 mm alpha = 60, delta = 1.4 (1.8) Mode Frequency [Hz] Symmetric tree fractal Mode Frequency [Hz] Asymmetric tree fractal

15 Fractals Symmetric tree resonances Mode 1 (43 Hz) Mode 2 (103 Hz) Mode 3 (330 Hz)

16 Fractals Symmetric tree stress N=3 N=1 N=2 N=0 Mode 1 (Syy) Pure bending Mode 2 (Syy) Bending in N=1 branches and Shear in N=0 branch Mode 3 (Syy) Combination of bending and shear

17 Multiple Dipole- next to be tested 3E9 Mode #1 Mode #2 4E10 2E10 1E10 10E10 Mode Frequency [Hz] Mode #5 Mode #3 Mode #4

18 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

19 RISE ACREO - Expertise

20 Sensor Systems MEMS ELECTROMAGNETIC BIO & CHEMICAL IMAGING WIRELESS / Low power sensors

21 Thank you! Prof. Cristina Rusu RISE Acreo, Sensor Systems, Gothenburg, Sweden This work has received funding from The European Union s Horizon 2020 research and innovation programme under grant agreement No

7. CONCLUSIONS & SCOPE

7. CONCLUSIONS & SCOPE ENERGY harvesting is a critical technology for the expansion of self-governing, self-powered electronic devices. As the energy requirements of low-power electronics reduction, the