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This letter proposes a procedure for the rapid prototyping and on-demand manufacturing of thin film flexible electro-adhesive devices (EADs) made with a commercial polyimide dielectric layer, inkjet printed interdigitated silver electrodes and blade coated silicone elastomer encapsulation backing. As a proof demonstration, flexible thin-film EADs featuring 9.6 cm2 active area, 315 μm thickness and 0.7 g weight have been manufactured and tested over different adhering substrates showing peak adhesive shear stresses of up to 56.67 kPa, fast response time (11 ms for initial activation and 0.3 s for full electrification) and little energy requirements (from 1.3 mJ for initial activation to 20 mJ for full electrification and with a subsequent power consumption of about 1 mW for long-term grasp holding). Practical application of the manufactured EADs within a gripper for the grasping and handling of real objects that include a glass bottle, a hollow carbon fiber tube, a cardboard box, a box with thin polypropylene envelope and a polypropylene bottle is also demonstrated.

In the last decade, additive manufacturing technologies (AMT) have spread widely in the industrial field, mostly for fast prototyping but also for the production of finished parts that need a high level of customization. With respect to the well-established material subtractive technologies (MST), some limitations due to component shape can be overcome with AMT. Topology optimization (TO) combined with AMT is a powerful tool capable of realizing components characterized by similar stiffness but smaller inertia concerning those realized with MST. This tool can be very useful in automatic machinery design in order to reduce the required motor torque. In fact, in this realm, the mechanisms are usually subjected to predominant inertial loads. Moreover, since the introduction of fuse filament deposition modeling (FDM) of continuous fiber-reinforced thermoplastics (CFRT), mechanical characteristics comparable to highperformance metal materials can be reached. Thus, rigidity and precision can be achieved as well. In addition to TO, with FDM and size optimization (SO), the designer can easily realize components characterized by a proper stiffness to be included in mechanisms to tune their dynamic mechanical characteristics. In fact, due to their ability to passively store and release mechanical energy, elastic elements can be introduced in a mechanism in order to compensate for kinetic energy variations, which drastically reduce motor torque requirements. The required elasticity can be easily introduced in the mechanism by replacing standard kinematic pairs with Compliant Joints (CJ) in the form of flexible lamina, also assuring lightness, precision and ease of realization. This paper analyzes the potentiality of FDM in combination with TO and CJ design (CJD) for the realization of automated machinery mechanisms subjected to inertial loads. A pusher mechanism is considered: the pros and cons of adopting the procedure are shown with respect to the standard procedure.

Dielectric elastomer generators (DEGs) are a promising option for the implementation of affordable and reliable sea wave energy converters (WECs), as they show considerable promise in replacing expensive and inefficient power take-off systems with cheap direct-drive generators. This paper introduces a concept of a pressure differential wave energy converter, equipped with a DEG power take-off operating in direct contact with sea water. The device consists of a closed submerged air chamber, with a fluid-directing duct and a deformable DEG power take-off mounted on its top surface. The DEG is cyclically deformed by wave-induced pressure, thus acting both as the power take-off and as a deformable interface with the waves. This layout allows the partial balancing of the stiffness due to the DEG’s elasticity with the negative hydrostatic stiffness contribution associated with the displacement of the water column on top of the DEG. This feature makes it possible to design devices in which the DEG exhibits large deformations over a wide range of excitation frequencies, potentially achieving large power capture in a wide range of sea states. We propose a modelling approach for the system that relies on potential-flow theory and electroelasticity theory. This model makes it possible to predict the system dynamic response in different operational conditions and it is computationally efficient to perform iterative and repeated simulations, which are required at the design stage of a new WEC. We performed tests on a small-scale prototype in a wave tank with the aim of investigating the fluid–structure interaction between the DEG membrane and the waves in dynamical conditions and validating the numerical model. The experimental results proved that the device exhibits large deformations of the DEG power take-off over a broad range of monochromatic and panchromatic sea states. The proposed model demonstrates good agreement with the experimental data, hence proving its suitability and effectiveness as a design and prediction tool.

The present invention relates to a laparoscopic surgical instrument. More particularly, the invention deals with a hand-held instrument equipped with a highly dexterous extremity, making the execution of very precise surgical intervention as in the robotic system while keeping very low costs as for all the hand-held surgical instrument. The present invention relates also to a kit comprising said laparoscopic surgical instrument and an instrument holder (e.g. a trocar) for the insertion of said instrument through an incision into a patient cavity.

This paper presents a design concept for affordable exoskeletons without renouncing to advanced interaction control modalities based on force control technologies. Affordability is reached by (1) lowering the motor requirements, thanks to a smart mechanical design, (2) lowering the sensing requirements, thanks to extensive use of microprocessor DMA, and (3) using low-cost computational platforms. A main finding of this work is that by lowering the motor requirements the exoskeleton improves its inherent force controllability.

Actuators driven by electrostatic force represent a very promising opportunity for the development of advanced robotic systems. Dielectric elastomer actuators have been long investigated and more recently devices based on fluid dielectric have been proposed as a possible alternative that shows remarkable performance. Here, we present a novel electrostatic actuator that is made of thin polyimide films and liquid dielectric, combined with rigid plates assembled to form a circular actuation unit that undergoes to out-of-plane expansion/contraction. Prototypes of these actuation units have been tested showing a contraction of up to 40%, a maximum power density during contraction of 100 W/kg, a maximum strain rate of 1000% per second, a bandwidth of approximately 10 Hz, and the ability to lift hundreds of times their weight. Additionally, these units resulted easy to manufacture in different dimensions and can be assembled in arrays and stacks to form an electrostatic bellow muscles (EBM) that can be effectively employed as a contractile artificial muscle, as pump and as electrostatic generator. EBM demonstrated their flexibility in matching a wide range of requirements and scales in terms force-displacement combinations and bandwidth. The compact 2-D shape, the low-cost of components, the simple assembling procedure, the high level of reliability and the relevant performance make the EBM a possible enabling technology for a variety of high-performance robotic and mechatronic systems.

In the last decade composite materials, previously almost exclusively used in aerospace and automotive industries, are becoming widespread thanks to the introduction of the fused filament fabrication (FFF) process in the additive manufacturing technology. With respect to the standard and more widely used material subtractive technologies, the FFF layer-by-layer construction process is capable of manufacturing parts featuring very complex geometry. Moreover, the deposition of reinforcing filaments provides components with highperformance mechanical characteristics. Since FFF is a relatively new technology, studies are still needed to fully understand the mechanical behavior of composite materials realized with FFF and how all the process parameters (e.g., layer thickness, filament deposition direction, type of matrix and reinforcement, the interaction between matrix and reinforcement) affect the final result. This paper deals with the preliminary experimental analysis of straight beams realized in carbon-fiber-reinforced Nylon White composite material with the MarkForged MarkTwo three-dimensional printer. Envisaged application of the considered straight beams is as flexible elements in compliant mechanisms. In particular, tensile and bending tests are performed on nine different straight beam specimens in order to provide a first understanding on how the filament disposition within the sample affects its mechanical response. From the results it is found that the proper position of the reinforcement filaments provides a very effective means to tune the selective compliance of beam flexures.

Flexible thin-film Electro-Adhesive Devices (EADs) represent a promising technology with great potential for gripper applications. Generally, the gripping action of an EAD is due to the electrostatic force induced by an electric field produced by applying a voltage across a couple of electrodes that are embedded between dielectric substrates. This paper presents a novel manufacturing process and the experimental characterization of a multilayer electro-adhesive gripper. The proposed device employs highly elastic silicone (PDMS) thin-film as the grasping layer, i.e., the dielectric layer that comes in contact with the grasped object, a carbon-black mixture in a silicone compound for the electrodes, and a rigid polyimide thin-film as the backing layer, i.e., the dielectric layer on the backside of the EAD. A fabrication methodology is illustrated, which starts from a casting of thin conductive electrodes on a polyimide film, followed by a laser-cutting operation to shape the electrodes and a blade casting process to encapsulate the overall system in a PDMS compound. Different prototypes obtained through this manufacturing procedure have been experimentally evaluated through a testing campaign conducted on three groups of specimens, each composed of five identical samples, with a different electrode thickness per group. Samples are tested for electrostatic shear stress and electrical breakdown during the grasping of paper substrates, identifying the best performing EAD group.

Scientific article published (with gold open access option) onthe journal Meccanica (Springer). The present file contains the published version (with no further modifications) of the paper. Abstract: Dielectric elastomer generators (DEGs) are soft electrostatic generators based on low-cost electroactive polymer materials. These devices have attracted the attention of the marine energycommunity as a promising solution to implement economically viable wave energy converters (WECs). This paper introduces a hardware-in-the-loop (HIL) simulation framework for a class of WECs that combines the concept of the oscillating water columns (OWCs) withthe DEGs. The proposed HIL system replicates in a laboratory environment the realistic operating conditions of an OWC/DEG plant, while drastically reducing the experimental burden compared to wave tank or sea tests. The HIL simulator is driven by a closed-loop real-time hydrodynamic model that is based on a novel coupling criterion which allows rendering arealistic dynamic response fora diversity of scenarios, including large scale DEG plants, whose dimensions and topologies are largely different from those available in the HIL setup. A case study is also introduced, whichsimulates the application of DEGs on an OWC plant installed in a mild real sea laboratory test-site. Comparisons with available real sea-test data demonstrated the ability of the HIL setup to effectively replicate a realistic operating scenario. The insights gathered on the promising performance of the analysed OWC/DEG systems pave the way to pursue further sea trials in the future.

Future robotic systems will be pervasive technologies operating autonomously in unknown spaces that are shared with humans. Such complex interactions make it compulsory for them to be lightweight, soft, and efficient in a way to guarantee safety, robustness, and long-term operation. Such a set of qualities can be achieved using soft multipurpose systems that combine, integrate, and commute between conventional electromechanical and fluidic drives, as well as harvest energy during inactive actuation phases for increased energy efficiency. Here, we present an electrostatic actuator made of thin films and liquid dielectrics combined with rigid polymeric stiffening elements to form a circular electrostatic bellow muscle (EBM) unit capable of out-of-plane contraction. These units are easy to manufacture and can be arranged in arrays and stacks, which can be used as a contractile artificial muscle, as a pump for fluid-driven soft robots, or as an energy harvester. As an artificial muscle, EBMs of 20 to 40 millimeters in diameter can exert forces of up to 6 newtons, lift loads over a hundred times their own weight, and reach contractions of over 40% with strain rates over 1200% per second, with a bandwidth over 10 hertz. As a pump driver, these EBMs produce flow rates of up to 0.63 liters per minute and maximum pressure head of 6 kilopascals, whereas as generator, they reach a conversion efficiency close to 20%. The compact shape, low cost, simple assembling procedure, high reliability, and large contractions make the EBM a promising technology for high-performance robotic systems.

This paper presents a capacitive Goniometer Dielectric Elastomers Sensor (GDES), capable of measuring the movement of human joints. The model and fabrication steps of such an innovative compliant device are reported along with the results of a preliminary validation experimental campaign. Application for the measurement of human elbow flexion is also presented, showing the promises of the proposed GDES as an alternative solution to the standard option of Inertial Measurement Units (IMUs) to compute the relative orientation between two body segments., https://youtu.be/Fw0C3Xs-1HI

Series Elastic Actuators (SEAs) are multi-degree-of-freedom spring-mass-damper systems that employ elastic transmission elements to reduce mechanical impedance and buffer energy from motor (input) to load (output). This work deals with the mathematical modeling of SEAs and their sizing for given application requirements. In designing traditional actuation systems a common approach is to optimize the speed ratio of the transmission with respect to a given figure of merit, such as the motor rated torque or power, once the output load torque and motion trajectories are given. Taking inspiration from existing techniques developed for the sizing of traditional actuators having just one degree of freedom, a new approach is presented here for two degrees of freedom SEAs, which enables the designer to optimally select at the same time both the ratio and the compliance of the elastic transmission.

Dielectric Elastomers (DEs) are deformable dielectrics that can be used as active materials in mechatronic transducers, such as actuators, sensors and generators. Focusing on actuation systems, several kinds of DE actuators have been proposed in the literature, being characterized by various shapes/sizes and disparate performances in terms of efficiency, force/power densities and reliability. In any case, up to date, these devices are mostly based on either silicone or acrylic elastomers. On the other hand, actuator prototypes, which exploit the electromechanical properties of styrenic rubber, have been scarcely considered. Therefore, in this paper, a styrene-based-rubber Lozenge-Shaped DE Actuator (LS-DEA) is proposed and its performance are empirically evaluated. In particular, after material characterization and on the basis of a design procedure previously proposed by the authors, it is practically shown how it is possible to optimize the LS-DEA elastic response in order to tailor the application requirements and also (if needed) to obtain a nearly-zero mechanical stiffness. Several experimental results are henceforth provided, as a basis to highlight advantages and disadvantages of styrenic rubber LS-DEA over similar acrylic or silicone-based devices

Up to date, Dielectric Elastomer Actuators (DEA) have been mostly based on either silicone or acrylic elastomers, whereas the potential of DEAs based on inexpensive, wide-spread natural and synthetic rubbers has been scarcely investigated. In this paper, a DEA based on a styrene-based rubber is demonstrated for the first time. Using a Lozenge-Shaped DEA (LS-DEA) layout and following a design procedure previously proposed by the authors, we develop prototypes featuring nearly-zero mechanical stiffness, in spite of the large elastic modulus of styrenic rubber. Stiffness compensation is achieved by simply taking advantage of a biaxial pre-stretching of the rubber DE membrane, with no need for additional stiffness cancellation mechanical elements. In the paper, we present a characterization of the styrene rubber-based LS-DEA in different loading conditions (namely, isopotential, isometric, and isotonic), and we prove that actuation strokes of at least 18% the actuator side length can be achieved, thanks to the proposed stiffness-compensated design.