Showing papers by "Elie Lefeuvre published in 2020"

Maximum power point of piezoelectric energy harvesters: a review of optimality condition for electrical tuning

Abstract: This paper is a review and synthetic overlook of existing energy harvesting circuits and techniques for piezoelectric energy scavengers. We provide a hierarchical presentation based on functional analysis to distinguish between existing solutions which may look superficially similar but prove to perform very differently in practice. Based on this hierarchical presentation, definitions of topologies, architectures and techniques are given in order to avoid redundancy among existing and future solutions. Then, after a thorough and unified mathematical analysis of the general problem to address, we present a comparison of the conditions for each technique to maximize the power flow from an external vibration source to an electrical load. This analysis is meant to help researchers and engineers make optimal choices for effective implementation of Maximum Power Point Tracking (MPPT).

Large-bandwidth piezoelectric energy harvesting with frequency-tuning synchronized electric charge extraction

Abstract: This paper reports, for the first time, experimental evidence of the effectiveness of the frequency-tuning synchronized electrical charge extraction technique (FTSECE) with a strongly-coupled generator. The ratio between the system bandwidth (7 Hz) and the natural bandwidth of the transducer (0.688 Hz) is 1017 %, surpassing previous demonstrations of synchronized charge extraction methods by a large extent. We prove that the bandwidth of the FTSECE system is only limited by the unideal characteristics of the circuit components and generator. This is a major advantage of FTSECE as opposed to other competitive methods where the bandwidth is intrinsically mathematically limited, even in the hypothetical presence of ideal components. We also propose a new circuit for the implementation of FTSECE, which allows the piezoelectric generator to be connected to the same ground as the control circuit. Our experimental setup based on the combination of a strongly-coupled piezoelectric generator and a FTSECE architecture allows operation at a maximum power plateau on a +/-3.5 % interval around the resonance frequency. The resulting full width at half maximum (FWHM) is +/-10 % around the resonance frequency, which corresponds to +200 % compared to most up-to-date architectures designed for bandwidth enhancement, with the advantage of suppressing local minima in the power responses.

Autonomous Energy Harvester Based on Textile-Based Enzymatic Biofuel Cell for On-Demand Usage

Abstract: This paper presents an autonomous energy harvester based on a textile-based enzymatic biofuel cell, enabling an efficient power management and on-demand usage. The proposed biofuel cell works by an enzymatic reaction with glucose in sweat absorbed by the specially designed textile for sustainable and efficient energy harvesting. The output power of the textile-based biofuel cell has been optimized by changing electrode size and stacking electrodes and corresponding fluidic channels suitable for following power management circuit. The output power level of single electrode is estimated less than 0.5 μW and thus a two-staged power management circuit using intermediate supercapacitor has been presented. As a solution to produce a higher power level, multiple stacks of biofuel cell electrodes have been proposed and thus the textile-based biofuel cell employing serially connected 5 stacks produces a maximal power of 13 μW with an output voltage of 0.88 V when load resistance is 40 kΩ. A buck-boost converter employing a crystal oscillator directly triggered by DC output voltage of the biofuel cell makes it possible to obtain output voltage of the DC-DC converter is 6.75 V. The efficiency of the DC-DC converter is estimated as approximately 50% when the output power of the biofuel cell is tens microwatts. In addition, LT-spice modeling and simulation has been presented to estimate power consumption of each element of the proposed DC-DC converter circuit and the predicted output voltage has good agreement with measurement result.

Fabrication and mechanical study of a titanium micro-membrane for in vivo pressure monitoring

Abstract: We herein introduce the fabrication and characterization of 22 Ti micro-membranes with an embossed structure. To date, this is the first titanium membrane micromachined in bulk Ti wafer ever reported in literature. This membrane will further be a part of an implantable MEMS capacitive sensor used for in vivo pressure monitoring in the human body. While pressure is known to be one of the most relevant parameters to help doctors monitoring patient health, in the case of active medical implants this has long been an unachievable goal until recently. In this context, the development of Ti-based microsensors appears as a promising way to overcome current issues related to the use of nonbiocompatible materials such as silicon and its complex, bulky and costly packaging.

Long-range Planar Conveyance Device Based On A Digital Electromagnetic Actuator Array

Abstract: Smart surfaces for micro-conveyance are planar motion devices that transport objects between specific positions. The solutions in this research topic have mainly used analog/continuous actuators with distributed sensors and feedback control schemes to accomplish high precision. Examples of these analog actuators are pneumatic (non-contact) and electrostatic (contact) conveyance systems, but their drawbacks are: complex modeling, control and air feeding logistics for the pneumatic solutions; and pull-in failures and high voltages for the electrostatic solutions. As an alternative, digital electromagnetic actuators offer sensor-less operation, simple control schemes and high precision but require precisely fabricated designs. In this article, we analyze the long-range capability of a digital electromagnetic actuator array prototype. We present the array’s operation principle and electromagnetic model, from which we derive the positives of expanding its active area. We perform experimental tests to demonstrate the long-range capability of the prototype and, based on the model and experimental results, we present and fabricate a modular and scalable design of the array for large active area applications.

Mechanical comparison between two titanium micro membranes for in vivo pressure monitoring

Abstract: We report the fabrication and characterization of two kinds of titanium membranes made of bulk titanium. Both membrane designs are compared mechanically to define the most suited for the targeted application. These membranes are future parts of Ti-based MEMS pressure sensors for active biomedical implants. As pressure is known to be linked to patient’s health for numerous diseases (glaucoma, heart failure, hydrocephalus...), in vivo pressure monitoring appears as a promising way to help medical doctors to define their treatments. Yet, most of current methods used to monitor pressure are still routinely invasive, which increases the risk of infection. The use of Ti as a mechanical transducer appears as a promising approach to tackle the lack of biocompatibility of standard semiconductor materials such as silicon, which requires a complex, bulky and costly packaging.

Synchronous conditioning circuits for piezo- and triboelectric harvesters in CMOS technologies

Abstract: This focus paper proposed for the track “Energy Harvesting and Power Efficient Electronics” addresses the new generation of conditioning circuits based on active energy extraction techniques, designed by the term “synchronous conditioning circuits”. Initially proposed for enhancing energy yield of piezoelectric transducers having intrinsic poor quality, these techniques are now a part of the established method not only for piezoelectric devices, but also for triboelectric transducers. Their recent success is due to intensive use of integrated CMOS technologies optimized for low-energy power converters, which allowed to build highly efficient systems even in the case when the input energy is of few microwatts. This paper shortly reviews the synchronous energy extraction technique and their applications, and then discusses recent successful implementations in CMOS technologies.