WP4/Sub Task. 4.2 Energy for autonomous systems

1. WP4/Sub Task.4.2 Energy for autonomous systems NanoElectronics Roadmap for Europe: Identification and DisseminationInterim Review meeting Brussels, July 2nd, 2018

2. 1. Introduction • Market growth on connected devices - 8.4B (2017) +30%, 20.4B (2020): IoT, healthcare, wearables, home automation, WSN, etc. • Energy supply is essential (<mW, tens of µW) Energy harvesting Autonomousdevice Objective: • Roadmap on energy harvesting technologies… • Identify material and technological issues, challenges, applications… Demonstration platform

3. 2. Selection of Technologies and Experts (1/2) • Experts were selected coming from Industries and Universities: • 2 Domain Workshops : Bertinoro, Italy, October 19th2016, Barcelona, Spain, December 15th 2017 • 9 technology experts : 6 present in the Domain Workshops. • Stephane Monfray– STMicroelectronics, Crolles, France Thermal energy harvesting,Electrostatic energy conversion • Anne Kaminski-Cachopo– Grenoble INP, France Solar Energy Harvesting • Aldo Romani – University of Bologna, Italy Circuits for energy management • Gustavo Ardila– Grenoble AlpesUniversity / Grenoble INP, France Mechanical energy harvesting (piezoelectric materials) • Alessandra Costanzo– University of Bologna, Italy RF energy harvesting/wireless power transfer • DhimanMallick/Saibal Roy – Tyndall Institute, Ireland Electromagnetic energy harvesters • James Rohan – Tyndall Institute, Ireland Energy storage devices : microbatteries • AndroulaNassiopoulou– IMEL/NCSR Demokritos, Greece Energy storage devices : micro capacitors

4. Concept #1: « Electrostatic conversion » • Applications are linked to mechanical • vibrations harvesting (movements) • Energydensityislow at macro level • but increases at micro scale • (relative capacitor variation increases) • Power isproportional to the surface potential • Main challenge isrelated to the reliability • of the material to keep the charges • CMOS compatibility • No commercial devices • Principle • Definition of FoMs (quantitive or qualitative) or planned evolution • Some recommendations • Enlarge frequency bandwidth (>50Hz) around low frequency target (<100Hz) • Reliability of materials is key (maintain charges over 10 years) • Develop flexible/low cost approaches (wearables) One electrode of the capacitor is charged (electret, tribolelectricity…) and the relative movement between the two electrodes causes a variation of electric capacity -> charges movement

5. Concept#2: « Piezoelectric conversion » • Principle Resonant cantilever covered by a piezoelectric layer and a inertial mass attached. As the cantilever is bent, strain is transferred to the piezo layer -> asymmetric charge distribution (Voltage) • Applications are linked to mechanical • Vibrations harvesting (movements) • Devices tuned at a specific vibration frequency • Devices are easy to fabricate • CMOS compatibility • Macro-devices and MEMS (new) are actually • on the market • Definition of FoMs (quantitive or qualitative) or planned evolution Surface/volume power density (µW/cm² or µW/cm3) - MEMS devices (research) (f < 300Hz, G<0.5) • Some recommendations • Consider new sustainable materials to avoid lead based piezoelectrics • Develop micro/nano piezo-composites could be a key for performance improvement

6. Concept#3: « Electromagnetic transduction » • Principle: Faraday’s Law • Definition of FoMs (quantitive or qualitative) or planned evolution Surface/volume power density (mW/cm² or mW/cm3), Miniaturized devices (f < 100Hz, G<0.5) • Some recommendations • CMOS compatible integration for rare-earth free magnets (e.g. NdFeB-neodymium) • 3D coil integration/development having low resistive loss/enhanced turn numbers. Relative motion – magnetic field & coil (or change in the flux linkage) -> Electromotive force • Applications are linked to mechanical • Vibrations harvesting (movements) • Devices tuned at a specific vibration frequency • Macro-devices are vastly developed and are • on the market • MEMS devices less explored due to drastic drop • in performance

7. Concept#4: « Thermal EH » • Principle • Fastthermalization (need for a bigheatsink) • Non-flexible • Bi2Te3Expensive/rare/toxicmaterial • Low output voltage • Power proportionnal to available • temperature gradient • Power proportionnal to available • temperature gradient • Definition of FoMs (quantitive or qualitative) or planned evolution ZT, output power vs available temperature difference (mW/K²/cm²) • Some recommendations • Consider new sustainable materials to avoid Bi2Te3. • Develop new thermal energy approaches (non Seebeck): Phase change, thermomechanical… Seebeck effect: generation of a voltage along a conductor when it is subjected to a temperature difference Low voltage : elevator circuit needed (working at Vteg>75mV)

8. Concept#5: « Photovoltaic EH » • A marketdominated by the Si (mature technology): • - For outdoor applications, crystalline Si solarcells • - For indoor applications, amorphous Si photovoltaiccells • Solar cells spectral sensitivity and efficiencydiffer • depending on the light spectrumwhichisvery • different for artificial and sun light • Indoor standard characterizationprocedures • and norms are not defined Principle : Photovoltaic effect: - Absorption of light by the semiconductor - Electron-hole pair generation, separation and collection - Power delivered • Definition of FoMs (quantitive or qualitative) or planned evolution (Commercialized) • Some recommendations • Define standard procedures for indoor photovoltaic cells characterization • Design and optimize structures for outdoor or/and indoor light (sensitivity to light sources, flexibility if necessary, cost…) Panasonic

9. Concept#6: « RF energy harvesting/wireless power transfer » 2 Principles : - Radiated far field RF source (High frequency 300MHz-GHz) -> Antennas (no interaction) • Near EM field – Capacitive coupling (lowfrequency 30kHz-MHz) ->coils, electrodes (strong interaction) • Far field : Used for low/ultra • low power (~µW-mW) • applications (harvesting) • Lowefficiency • No commercial applications • Near Field : medium to high • power app. (~mW-W-kW). • Medium to high efficiency • Commercial applications • Definition of FoMs • Some recommendations • Optimize rectenna components (minimize losses, maximize power transfer) • Design high efficient receiving antennas with miniaturization constraints (maximize received power)

10. Concept#7: « Energystorage - Microbatteries » • Si integrated • Lithium basedthin films: ~1 mWh/cm2, • capacityretention -> 1000 cycles • Electrode thicknesslimit < ~µm • Ionicconductivity of • solidelecrolyte << liquidbased • (commercial) • Size reduction, safer Principle : • Electrolyte : high ion conductivity, lowelectronic conductivity • Replacement of the classical Liquide electrolyte -> thin film • Definition of FoMs (quantitive or qualitative) or planned evolution • Some recommendations • Multilayer materials processing -> increase capacity/unit footprint • New materials: increase ionic (electrolyte) and electronic (electrodes) conductivity 10µm

11. Concept#8: « Energystorage - Microcapacitors » • Si integrated (integration compatibility) • Robustness of operation (lack of • electrolyte) • Higher voltage operation • (lowerleakagecurrent) • Environmental, healthfriendlymaterials • Disadvantage: lower capacitance • density -> energystorage 3 Parameters : • Capacitance density (Energystored) • Leakagecurrent (Operation voltage, energystored, retention) • Seriesresistance (Charging, discharging time thus power) • Definition of FoMs (quantitive or qualitative) or planned evolution • Some recommendations • Research on uniform thin high-k dielectrics with reduced leakage currents, 3D structures for high capacitance density, new electrode materials for decrease series resistance

12. Concept#9: « Micro-power management » • Principle • Essential to store and deliverthe harvestedenergy to circuits • Must consume lessthan theinput power • Efficiencymust betradedwithself-consumption • Shouldkeep sources in the MPP • Definition of FoMs (quantitive or qualitative) or planned evolution • Some recommendations • Define trade-offs (intrinsic power consumption, efficiency, performance): energy-aware power design of circuits. • Size reduction of inductors, planar alternatives (piezoMEMS), quality of switches (src: A. Romani et al., IEEE Computer 2017)

13. Application examples: • Application 1: Transports (automotive, railroad) • Power management circuits : 40-80% (<10µW), 90% (~100µW)

14. Conclusion: Main recommendations • Projects should mainly focus on the development and optimization of a complete application as a whole (from harvesting to the use case). • The improvement of the EH performance/efficiency is as important as the development of “green” materials. Replacing toxic/rare materials used nowadays (lead based piezoelectrics, Bi2Te3 for thermoelectrics, NdFeB - neodymium, for electromagnetic conversion). • The use of nanotechnologies is foreseen to increase the performance of all the concepts in general. • Flexible and low cost approaches for wearable applications should be developed as well. • Increase support to European industries who are very active in most of these concepts. Thank you for your attention!