Flexible aeroelectric micro-generators for self-powering communicating sensors

L’avènement de l’Internet des Objets a fait de la récupération d’énergie ambiante un enjeu majeur dans le but d’alimenter les microsystèmes communicants. Dans ce contexte, les travaux réalisés dans cette thèse portent sur le développement d'un micro-générateur piézoélectrique flexible, capable de convertir l’énergie mécanique de faibles flux d’air. L’objectif est de rendre certains microsystèmes autonomes en énergie, ou du moins de permettre de prolonger leur durée d’utilisation avec la récupération d'énergie. Les micro-générateurs flexibles sont fabriqués à partir de films minces de zircono-titanate de plomb (PZT) de 3 μm d’épaisseur encapsulés entre des films de poly(téréphtalate d'éthylène) (PET). Le procédé de fabrication des micro-générateurs a été optimisé afin d’accroître leur rendement. Ainsi, l’optimisation de la structure d’électrodes et de la géométrie du générateur a permis de multiplier par 625 la puissance maximale récupérée. Dans cette étude, les micro-générateurs ont été soumis à différents types de sollicitations mécaniques (pot-vibrant, système de traction/compression et soufflerie) de manière à évaluer leur aptitude à la récupération d’énergie. Ainsi, les essais en soufflerie ont montré qu’il était possible de récupérer une puissance de 38 μW à 10 Hz lorsqu‘un générateur était soumis à un faible courant d'air (6 m/s). Ce générateur a permis d’alimenter un capteur de température communicant durant plusieurs cycles de mesures/envoi des données.The advent of the Internet of Things has rendered the ambient energy harvesting a major issue for powering communicating microsystems. In this context, this work focuses on the development of a flexible piezoelectric micro-generator able to convert the mechanical energy from low airflows. The objective is to develop autonomous microsystems, or at least to extend their lifespan with energy harvesting. To harvest ambient energy, the flexible micro-generators are made of 3 μm-thick lead zirconate titanate (PZT) thin films encapsulated between polyethylene terephthalate (PET) films. The manufacturing process of the micro-generators has been optimized in order to increase their energy efficiency. Both the optimization of the electrode structure and the geometry of the generator made the maximum harvested power increase by a factor of 625. In this work, to characterize the energy harvesting, the micro-generators were excited with different systems (shaker, traction/compression system and wind tunnel). Thus, wind tunnel tests have shown that it was possible to harvest a power of 38 μW at 10 Hz when the generator was subjected to a low airflow (6 m/s). This generator allowed to power a communicating temperature sensor during several measurement/data transmission cycles

Flexoelectric energy harvester based on soft semi-conducting polymer films

A flexoelectric micro generator able to harvest mechanical energy from large localized curvature variations along multilayer polymer films is proposed. The energy conversion is based on direct flexoelectricity, which is a universal effect in all solid dielectrics that corresponds to the appearance of an electrical polarization induced by a deformation gradient. This “flexoelectric technology” is a potential alternative to energy harvesting with piezoelectrics without the need for applying large electric field for inducing macroscopic piezoelectric effect and thus eliminates associated problems such as leakage and breakdown. The micro-generators are made from a solution of semi-conducting (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) deposited as a free-standing thin film. This material is lead-free and biocompatible, ideal for applications in the medical field. The developed thin films exhibit a very large flexoelectric coefficient > 50 μC/m (1000 times higher than insulating polymer films) and a high flexibility which allows them to withstand large deformation. The electrical characterization of the films was performed using a mechanical roller to apply a low frequency bending radius to the micro-generator and recovering the output flexoelectric current. We were able to obtain a current density of about 2.2 μA/cm2 at 2 Hz for a curvature of 62 m-1. The electrical characterization under slow air flow (< 6 m/s) was also carried out in wind tunnel in order to demonstrate the aero-electric potentialities of the micro-generators. The combination of flexibility and flexoelectricity allows the integration of these films into devices for low frequency (<20 Hz) mechanical energy conversion

High curvature sensors based on flexoelectric effect in soft semi-conducting polymer films

A sensor based on the flexoelectric effect capable of measuring large curvature variations is proposed. The flexoelectric effect is defined as the coupling between the strain gradient and polarization in solid dielectrics and semiconductors. It can be considered as an alternative transduction mechanism to the piezoelectric effect to directly measure curvature without the need to apply a large electric field to induce a macroscopic piezoelectric-like effect.In this study, the process for obtaining a bending sensor from a semiconducting solution of commercial (3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) deposited as a free standing thin film in the thickness range : 18 μm - 50 μm is presented. Owing to its specific properties, PEDOT:PSS films are mechanically fragile and sensitive to water. An encapsulation step in a polyethylene terephthalate (PET) polymer increases the robustness of the device while maintaining its flexibility.The flexoelectric characterization showed a coefficient much higher than those reported in the literature for PEDOT:PSS polymers with a coefficient that reaches 76 μC/m at 0.5 Hz (3 orders of magnitude higher than insulating polymers). In the case of PEDOT:PSS which is a mixed ionic/electronic semi-conductor, flexoelectric response might be mainly attributed to short range PEDOT+-PSS- dipole motion rather than pure ionic polarization mechanism (flexoionic effect).It was also demonstrated that with the acquisition of the output current signal at the sensor terminals it is possible to determine the curvature of the sensor used in cantilevered beam bending configuration. The demonstration of their efficiency in converting a strain gradient into electrical energy, combined with their robustness and flexibility, makes these devices very attractive for wide range curvature sensing

Flexoelectric energy harvester based on soft semi-conducting polymer films

International audienceA flexoelectric micro generator able to harvest mechanical energy from large localized curvature variations along multilayer polymer films is proposed. The energy conversion is based on direct flexoelectricity, which is a universal effect in all solid dielectrics that corresponds to the appearance of an electrical polarization induced by a deformation gradient. This “flexoelectric technology” is a potential alternative to energy harvesting with piezoelectrics without the need for applying large electric field for inducing macroscopic piezoelectric effect and thus eliminates associated problems such as leakage and breakdown. The micro-generators are made from a solution of semi-conducting (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) deposited as a free-standing thin film. This material is lead-free and biocompatible, ideal for applications in the medical field. The developed thin films exhibit a very large flexoelectric coefficient > 50 μC/m (1000 times higher than insulating polymer films) and a high flexibility which allows them to withstand large deformation. The electrical characterization of the films was performed using a mechanical roller to apply a low frequency bending radius to the micro-generator and recovering the output flexoelectric current. We were able to obtain a current density of about 2.2 μA/cm2 at 2 Hz for a curvature of 62 m-1. The electrical characterization under slow air flow (< 6 m/s) was also carried out in wind tunnel in order to demonstrate the aero-electric potentialities of the micro-generators. The combination of flexibility and flexoelectricity allows the integration of these films into devices for low frequency (<20 Hz) mechanical energy conversion

High curvature sensors based on flexoelectric effect in soft semi-conducting polymer films

International audienceA sensor based on the flexoelectric effect capable of measuring large curvature variations is proposed. The flexoelectric effect is defined as the coupling between the strain gradient and polarization in solid dielectrics and semiconductors. It can be considered as an alternative transduction mechanism to the piezoelectric effect to directly measure curvature without the need to apply a large electric field to induce a macroscopic piezoelectric-like effect.In this study, the process for obtaining a bending sensor from a semiconducting solution of commercial (3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) deposited as a free standing thin film in the thickness range : 18 μm - 50 μm is presented. Owing to its specific properties, PEDOT:PSS films are mechanically fragile and sensitive to water. An encapsulation step in a polyethylene terephthalate (PET) polymer increases the robustness of the device while maintaining its flexibility.The flexoelectric characterization showed a coefficient much higher than those reported in the literature for PEDOT:PSS polymers with a coefficient that reaches 76 μC/m at 0.5 Hz (3 orders of magnitude higher than insulating polymers). In the case of PEDOT:PSS which is a mixed ionic/electronic semi-conductor, flexoelectric response might be mainly attributed to short range PEDOT+-PSS- dipole motion rather than pure ionic polarization mechanism (flexoionic effect).It was also demonstrated that with the acquisition of the output current signal at the sensor terminals it is possible to determine the curvature of the sensor used in cantilevered beam bending configuration. The demonstration of their efficiency in converting a strain gradient into electrical energy, combined with their robustness and flexibility, makes these devices very attractive for wide range curvature sensing

Large Curvature Sensors Based on Flexoelectric Effect in PEDOT:PSS Polymer Films

International audienc

Foot-mounted pedestrian navigation reference with tightly coupled GNSS carrier phases, inertial and magnetic data

2017 International Conference on Indoor Positioning and Indoor Navigation (IPIN), SAPPORO, JAPON, 18-/09/2017 - 21/09/2017Many indoor navigation systems have been developed for pedestrians and assessing their performances is a real challenge. Benefiting from a reference solution that is accurate enough to evaluate other indoor navigation systems and assist novel research is of prime interest. The design and algorithms of a foot-mounted reference navigation system titled PERSY (PEdestrian Reference SYstem) are presented in this paper. Quasi static phases of the acceleration and the magnetic field are used to mitigate inertial sensor errors in indoor spaces. Differential indoor/outdoor GNSS phase measurements are added to the strapdown EKF to improve the positioning accuracy with a correlation between low and high frequency velocity estimates. Experiments conducted with four persons over a 1.4 km walking distance show a 0.22% positioning mean error

Frequency tunable, flexible and low cost piezoelectric micro-generator for energy harvesting

International audienceThe conversion of vibrations into electrical energy for powering low-power small electronic components has been investigated by researchers from different disciplines in the last decade. Among the possible mechanisms, piezoelectricity has received particular attention. In the field of low frequency cantileverbased vibration energy harvesters, the proof mass is essential in order to reduce the resonance frequency and increase the stress along the beam to increase the output power. In this work, a manufacturing process of a micro generator is proposed to easily modify and increase the dimensions of the cantilever, and thus tune its resonance frequency. The effect of the position of the mass on the performances of this flexible piezoelectric energy harvester is also studied. For a proof mass at 8 cm from clamping, we obtain a resonance frequency of 9.9 Hz, a maximum power of 127 W against a resonance frequency of 16 Hz and a maximum power of 72 W with a mass at 4 cm. This shows that the maximum power extracted varies in ?= 1/fR for a constant acceleration of 1 g (9.81 m/s2), as expected theoretically. These promising results show that the prototype can be considered for a low power application as an energy harvesting-based micro-generator

Low frequency flexible piezoelectric energy harvesters

International audienceThis research focuses on the development of flexible piezoelectric multi-layered 3 µm-thick films for air flow energy harvesting at low frequency (< 10 Hz)

Flexible piezoelectric micro-generator with interdigitated electrodes for energy harvesting

National audienceThis research work deals with the development of high performance flexible piezoelectric microgenerators, able to harvest low frequency (<10 Hz) mechanical energy from wind flows, for instance. Such hybrid microsystems are made of lead zirconate titanate (PZT) films easily transferred onto an insulating polymeric substrate. In order to optimize the output voltage and harvested power, an interdigitated electrode structure is adopted. By manually subjecting the micro device to a pseudo-sinusoidal excitation of about 2 Hz, an output voltage of 7.7 V and a power of 220 nW are obtained, using a resistive load of 100 MΩ. Owing to the IDE design, the optimum load resistance is found to be about 71 GΩ, yielding calculated huge maximum voltage values (6.2 kV) and power (137 µW). These results make the studied micro-generators promising candidates to electrically power miniature, autonomous wireless electronic micro devices, such as distributed sensor networks