This article presents the optimisation of an electromagnetic actuator composed of a toroidal coil and a cylindrical magnet positioned along the coil’s axis that may be used for non-contact measurement of excitation of structures, for vibration testing, electromagnetic shunts or energy harvesting. The originality of this work lies in proposing a generalised optimisation of such electromagnetic systems to maximise the axial force for a given volume or mass, while aiming for the most linear behaviour possible. A semi-analytical and dimensionless computation method is introduced and compared with existing approaches. The influence of each geometric parameter of the coil and the magnet on the axial force is investigated. Furthermore, the non-linearities induced by the displacement of the magnet in the coil’s magnetic field are quantified, and the effect of design parameters on limiting these non-linearities is analysed to identify optimal geometries. The axial force and non-linearity computations are validated through finite element simulations and experimental measurements. Finally, a study on the influence of the coil wire diameter on the force output and allowable current is also presented.

During cochlear implant surgery, standard electrode arrays are inserted into the scala tympani to stimulate the spiral ganglion cells and rehabilitate hearing in deaf patients. However, conventional electrode arrays' stiffness and passive nature lead to potential trauma or incomplete insertion during the procedure. To overcome these limitations, an original steerable thin film electrode array (TFEA) has been developed. First, the twenty gold electrodes, distributed over a 25 mm length, with an average surface area of 0.16 mm2, are significantly larger than those of existing TFEAs. These larger electrode surface areas enable safe neural stimulation within charge density limits below the Shannon threshold. By adjusting the material thicknesses, the proposed TFEA offers tunable stiffness, enabling safer and more flexible insertion. The microfabrication process, using SU-8 negative photoresist thin films, is both cost-effective and straightforward. In addition, the ability to dynamically adjust the curvature of the TFEA during insertion into a 3D printed cochlea model using low voltage conducting polymer based micro-actuator has been demonstrated. This marks the first instance of electrode array insertion with adaptive curvature, minimizing contact with cochlear walls. Successful insertion was achieved, with a curvature angle close to 360° This active TFEA has the potential to improve insertion control and reduce the risk of trauma during cochlear implantation.

In this paper, a novel piezoelectric actuator-based inchworm motor and its driving mechanism has been proposed for high speed linear application. Three high voltage positive square pulses with appropriate phase sequence amongst them have been applied to the two clamps and one extender of IM to achieve the desired linear translation. Isolated mosfet-based switching and oscillation circuits have been designed to operate the motor at high switching frequencies by dynamically reducing the capacitive reactance of the piezoelectric stack actuators. Consequently, experiments on the characterization of the piezo-actuators have been performed to identify the pre stress on the motor rail. Geometric model of the system has been developed using finite element analysis to determine displacement distribution in Clamping Mechanism and Extending Mechanism before physically fabricating the motor prototype to verify the driving mechanism. Performance evaluation has been carried out under varying duty cycles, switching frequencies and loads. The motor is observed to achieve a maximum no load speed of 60 mm/s under the 80-90 V positive square pulse at a frequency of 3 kHz with a 20 % duty cycle. A relatively high electrical driver efficiency of 42 % is experimentally achieved which makes the proposed mechatronic system highly suitable for low-size, high torque industrial applications.

This article presents the design of a microfabricated bio-inspired flapping-wing Nnano Aaerial Vvehicle (NAV), driven by an electromagnetic system. Our approach is based on artificial wings composed of rigid bodies connected by compliant links, which optimise aerodynamic forces though replicating the complex wing kinematics of insects. The originality of this article lies in a new design methodology based on a triple equivalence between a 3D model, a multibody model, and a mass/spring model (0D) which reduces the number of parameters in the problem. This approach facilitates NAV optimisation by using only the mass/spring model, thereby simplifying the design process while maintaining high accuracy. Two wing geometries are studied and optimised in this article to produce large-amplitude wing motions (approximately 40^∘ ), and enabling flapping and twisting motion in quadrature. The results are validated thanks to experimental measurements for the large amplitude and through finite element simulations for the combined motion, confirming the effectiveness of this strategy for a NAV weighing less than 40 mg with a wingspan of under 3 cm.

Insects are characterized by their agility in flight, including hovering, backward and forward movements. Studies on insect flight have revealed that the lifting force generated by vibrating wings is most effectively produced when flapping and twisting movements are in phase quadrature, i.e. one being maximal when the other is zero. Based on these results, Nano Air Vehicles (NAV) that replicate insect wing motion using a fully flexible structure were fabricated through microfabrication using lithography methods. In this article, we will show that it is possible to design more efficient vibrating wings by replacing their fully flexible ribs with an assembly of thin and thick parts, the former constituting the compliant links and the latter composing the rigid bodies. The first advantage of this concept is that the wing optimisation can be carried out on a simple mass/spring vibrating systems with very few degrees of freedom. Another advantage is that these prototypes are more resistant because the thinness of the structure is concentrated at the compliant link. This means that very high vibration amplitudes can be achieved without damaging the structure.

When developing a flying robot on the insect scale, all process must be developed from scratch as usual macroscale solutions for the design and fabrication would not satisfy the extreme mass and power limitations. In this context, the aims of this work are to outline the proposed bioinspired approach and to present the different original concepts deployed to tackle such an issue, before analyzing carefully the simulated and experimental results. More precisely, the presented nano air vehicle is inspired from the diptera order and consists of two pairs of wings micromachined using MicroElectroMechanical Systems technologies and an electromagnetic actuator added to the thorax to control the kinematics of the wings. The prototypes weigh as little as 22 mg with a 25 mm wingspan and 15 mm length and demonstrate a lift force equivalent to their weight.

Conducting polymer (CP) actuator has nonlinear dynamic characteristics during its charge process. In this study, we proposed an electromechanic model and an optimal controller for a type of ionic electroactive polymer (IEPA) actuator with submillimeter scale, which can produce large deformation under low actuation voltage. The electronic model is to describe the evolution of charge state in time domain. The mechanic model is to calculate the deformation of CP actuator under the actuation force and external force. Based on the electromechanic coupling model, a parameter identification method is proposed to estimate the nonlinear parameter of CP actuator. The experiments show that our electromechanic model successfully predicts the deformation of actuator under different input voltages with the identified parameters. In the last step, an optimal controller is designed to control the orientation of IEAP actuator, which achieves at a high control performance in our experiments. The success of the modeling and control lays the foundation work for the subsequent biomedical applications.

In this paper, the design and experimental analysis of a piezo-motor for applications requiring compact size, high blocking and driving forces are presented. Mechanical design addresses difficulties associated with high integration flexibility and high blocking force for the motor. The technology is inspired from a real inchworm motion and is based on Piezoelectric Actuators (PAs). The proposed Inchworm Motor (IM) consists of an extending mechanism (EM) and two doubled clamping mechanisms (CMs). Theoretically and by using Finite Element Analysis (FEA), the CM is designed in order to obtain high clamping forces between rotor and stator (2500N), while the EM is designed for large displacement (free stroke of 0.01mm) and high force (500N) using PAs. Practically and by using a preliminary low power supply (80V, 1Hz), the working principle of the motor is validated under testing conditions of 300N as a clamping force and 5N as a driving force. The fabricated IM achieves speed of 2.25 μm/s. Experimental methods for verifying the theoretical force, calibrating the pre-stressing force and measuring the friction coefficient between the stator and the rotor are proposed. A motor with a weight of 78g and dimensions of 100mm×16mm×7mm ensures full clamping ability when not electrically activated.

Conducting polymer-based micro-actuators are of great interest in soft MEMS as they exhibit large strains and forces in response to electrical stimulation. To date, these micro-actuators have very often been characterized by applying low frequency voltage to extract the electromechanical characteristics. However, many applications require maintaining the actuator's position for several minutes. A micro-camera tracking the displacements of an object, the actuation of a cochlear implant during surgery, or closing micro-tweezers to manipulate objects are potential applications for which actuation is achieved by applying a direct current (DC) voltage. Knowledge of the behavior of micro-actuators under and after a DC voltage is crucial for modeling and future control. Consequently, the kinetics to reach the maximum strain followed by back-relaxation are identified. It is shown that it is the result of competition between an elastic restoring force and the backflow of the ions inside the actuator. A residual strain is observed after a short circuit and studied as a function of the DC voltage applied. It is demonstrated that the voltage and the chronology of the power-ups affect the actuator position and strain amplitude. The interpretation of the experimental results linked directly to the intrinsic operation of micro-actuators is presented.

Cochlear implants made of standard silicone electrode array (EA) are currently used to stimulate the auditory nerve of patients’ cochlea. The implants have a proximal diameter of 0.5mm and 2~3cm long composed of 20 bulk platinum electrodes and connection wires (Ø 25µm). Due to their stiffness and passive nature, the most difficult task during implant surgery is inserting the EA properly into the tympanic ramp of the patient's cochlea, often leading to trauma or incomplete insertion. In this work, we developed an original smart EA for efficient insertion. This prototype has a lower stiffness and functionalized with an electronic conducting polymer based micro-actuators able to bend under low electrical voltage stimulation. This prototype is expected to reduce the friction forces during insertion, allow better control of the insertion process, facilitate the work of the surgeon and decrease the probability of trauma.

In this paper, a model to describe the electrochemomechanical behavior of conducting polymer (CP) based tri-layer transducer is proposed. This model will be used for simulation, control and estimation purposes. Energetic Macroscopic Representation (EMR) has been investigated in order to provide a displacement estimator and an inversion-based control for position feedback of the CP based actuator (CPBA). This work is illustrated with experimental and simulation results.

Conducting polymers have interested many research groups as they exhibit a large strain in response to electrical stimulation, which is promising for materials used in MEMS. To date, these micro-actuators have very often been characterized by applying an AC voltage to extract the produced strains and forces. However, many applications require subjecting the actuators to an electrical voltage threshold for about 10 seconds or until several minutes. A micro-camera tracking the displacements of an object, the actuation of a cochlear implant during surgery, or the closing of micro-tweezers for manipulation objects are potential applications for which actuation is achieved by applying a DC voltage. In this way, the kinetics to reach the maximum strain are identified and compared. The application of a DC voltage to the conducting polymer-based micro-actuator for an extended period of time results in the emergence of a "memory effect". In particular, the actuator does not return to its initial position promptly after a short-circuit. In addition, the electromechanical measurements conducted show that the deformation obtained depends on the DC voltage used for the previous actuation. The memory effect is directly related to the intrinsic operation of micro-actuator trilayers where the separator (NBR/PEO) is filled with an ionic liquid electrolyte that is involved during oxidation and reduction of the conductive polymer electrodes (PEDOT:PSS/PEO). An explanation of the physico-chemical phenomena involved will be proposed. These results are needful for the modeling and future control of these conjugated polymer micro-actuators integrated into microsystems devices for real-life applications.

Modelling trilayer conducting polymer is still challenging as it exhibits interrelated coupled multiscale and non-linear characteristics. Therefore, this work proposes to review the underlying electro-chemo-mechanical principles in ultrathin PEDOT trilayer ionic conducting polymers based upon internal ion charge transport, conduction phenomena, redox process and elastic deformation. Microscale governing equations are first analyzed and the choice of appropriate assumptions depending of the used material is discussed. Since exact analytical solutions can be so far given only for some limited conditions, numerical solutions are developed to solve the problem. Then simulations in both sensing and actuating are successfully compared with experiments.