The aim of this publication is to conclude on the interest of vibratory energy harvesting on classic quadcopter drone for autonomous applications (battery charging in real time, autonomous sensors), monitoring or even vibration control applications. A complete dynamic analysis allows to quantify the amount of electrical power that is possible to produce during the hovering flight of a quadcopter drone. These results have been obtained by substitution of the inert parts of the drone by piezoelectric components. For that purpose, different types of piezoelectric structures have been tested, including some commercial transducers (DuraAct from Piezoelectric Instrument and Murata buzzers) and some home-made such as a piezoelectric paint. Our original piezoelectric smart arms have been able to scavenge up to 5.35 mW during a stationary flight which remains quite enough to supply low-consumption sensors for monitoring applications.

Since 1995, Magnetic Resonance Elastography (MRE) has been constantly developed as a non-invasive diagnostic tool for quantitative mapping of mechanical properties of biological tissues. Indeed, mechanical properties of tissues vary over five orders of magnitude (the shear stiffness is ranging from 10² Pa for fat to 10⁷ Pa for bones). Additionally, these properties depend on the physiological state which explains the granted benefit of MRE for staging liver fibrosis and its potential in numerous medical and biological domains. In comparison to the other modalities used to perform such measurement, Magnetic Resonance (MR) techniques offer the advantages of acquiring 3D high spatial resolution images at high penetration depth. However, performing MRE tissue characterization requires low frequency shear waves propagating in the tissue. Inducing them is the role of a mechanical actuator specifically designed to operate under Magnetic Resonance Imaging (MRI) specific restrictions in terms of electromagnetic compatibility. Facing these restrictions, many different solutions have been proposed while keeping a common structure: a vibration generator, a coupling device transmitting the vibration and a piston responsible for the mechanical coupling of the actuator with the tissue. The following review details the MRI constraints and how they are shaping the existing actuators. An emphasis is put on piezoelectric solutions as they solve the main issues encountered with other actuator technologies. Finally, flexible electroactive materials are reviewed as they could open great perspectives to build new type of mechanical actuators with better adaptability, greater ease-of-use and more compactness of dedicated actuators for MRE of small soft samples and superficial organs such as skin, muscles or breast.

This work details the design and experimental characterization of a 2D rectenna for scavenging radio frequency energy at 2.45 GHz (WiFi band), fabricated on polylactic acid polymer (PLA) using a plastronics approach. PLA is the RF substrate of both antenna and rectifier. The two transmission line (TTL) approach is used to characterize the substrate properties to be considered during design. A linearly polarized patch antenna with microstrip transmission feeding is connected to a single series diode rectifier through a T-matching network. The antenna has simulated and measured gain of 7.6 dB and 7.5 dB, respectively. The rectifier has a measured DC output power of 0.96 $\mathsf{\mu }$W at an optimal load of 2 k$\Omega$ under RF input power of −20 dBm at 2.45 GHz. The power conversion efficiency is 9.6% in the latter conditions for a 54 × 36 mm patch antenna of a 1.5 mm thick PLA substrate obtained from additive manufacturing. The power conversion efficiency reaches a value of 28.75% when the input power is −10 dBm at 2.45 GHz. This corresponds to a peak DC power of 28.75 $\mathsf{\mu }$W when the optimal load is 1.5 k$\Omega$. The results compare significantly with the ones of a similar rectenna circuit manufactured on preferred RF substrate.

Harvesting of ambient radio-frequency energy is largely covered in the literature. The RF energy harvester is considered most of the time as a standalone board. There is an interest to add the RF harvesting function on an already-designed object. Polymer objects are considered here, manufactured through an additive process and the paper focuses on the rapid prototyping of the harvester using a plastronic approach. An array of four antennas is considered for circular polarization with high self-isolation. The RF circuit is obtained using an electroless copper metallization of the surface of a 3D substrate fabricated using stereolithography printing. The RF properties of the polymer resin are not optimal; thus, the interest of this work is to investigate the potential capabilities of such an implementation, particularly in terms of freedom of 3D design and ease of fabrication. The electromagnetic properties of the substrate are characterized over a band of 0.5–2.5 GHz applying the two-transmission-line method. A circular polarization antenna is experimented as a rapid prototyping vehicle and yields a gain of 1.26 dB. A lab-scale prototype of the rectifier and power management unit are experimented with discrete components. The cold start-up circuit accepts a minimum voltage of 180 mV. The main DC/DC converter operates under 1.4 V but is able to compensate losses for an input DC voltage as low as 100 mV (10 $\mathsf{\mu }$W). The rectifier alone is capable of 3.5% efficiency at −30 dBm input RF power. The global system of circularly polarized antenna, rectifier, and voltage conversion features a global experimental efficiency of 14.7% at an input power of −13.5 dBm. The possible application of such results is discussed.

The development of environmentally friendly electronic circuits offers a sustainable alternative to conventional printed circuit board (PCB) manufacturing, which relies on chemically intensive and polluting processes. Screen printing of conductive inks is an effective and widely used method for fabricating flexible printed electronics (FPEs), and particularly well-suited for in-mold electronics (IMEs) applications. Screen printing of electronic circuits can be carried out on nearly all types of substrates, including recyclable and biodegradable polymers, thereby reducing the environmental impact. This paper presents the formulation of a silver conductive ink with stretchable properties, using poly(lactic acid) as the binder and Cyrene as the solvent, which are both biobased and biodegradable. Inks were formulated using silver flakes of different sizes (2.2 µ m–5.6 µ m) at a fixed content of 60%. Rheological behavior of the inks was measured to determine their printability, and resolution of printed patterns was tested using a scanning electron microscope. Thermal curing and photonic curing were used on the inks to study their electrical characteristics as functions of curing temperature and conditions. Among the latter tested formulations, the ink with a mixture of fine and large particles featured the best performance with an electrical resistivity of 34.77 ± 3.29 μ Ω · cm after heat treatment at 120 °C and 9.39 ± 0.17 μ Ω cm after photonic curing. This ink was also highly stretchable, with bending cycle tests showing an increase of electrical resistance only 8% after 1000 cycles, and the electrical continuity still intact even after 5000 cycles. Thermoforming tests confirmed electrical continuity at strains exceeding 30%. Demonstrators in FPEs and IME highlight the potential of these inks. This work shows that the developed ink exhibits electrical and stretchability properties equivalent to or even better than those of inks from previous research or commercial products, while reducing the environmental impact and enhancing user safety.