Mechanical Fatigue on Gold MEMS Devices: Experimental Results

The effect of mechanical fatigue on structural performances of gold devices is investigated. The pull-in voltage of special testing micro-systems is monitored during the cyclical load application. The mechanical collapse is identified as a dramatic loss of mechanical strength of the specimen. The fatigue limit is estimated through the stair-case method by means of the pull-in voltage measurements. Measurements are performed by means of the optical interferometric technique.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/16838

Comparison Between Damping Coefficients of Measured Perforated Micromechanical Test Structures and Compact Models

Measured damping coefficients of six different perforated micromechanical test structures are compared with damping coefficients given by published compact models. The motion of the perforated plates is almost translational, the surface shape is rectangular, and the perforation is uniform validating the assumptions made for compact models. In the structures, the perforation ratio varies from 24% - 59%. The study of the structure shows that the compressibility and inertia do not contribute to the damping at the frequencies used (130kHz - 220kHz). The damping coefficients given by all four compact models underestimate the measured damping coefficient by approximately 20%. The reasons for this underestimation are discussed by studying the various flow components in the models.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/16838

Experimental analysis of viscous and material damping in microstructures through the interferometric microscopy technique with climatic chamber

This study describes an experimental analysis of energy dissipation due to damping sources in microstructures and micro electro-mechanical systems (MEMS) components using interferometric microscopy techniques. Viscous damping caused by the surrounding air (squeeze film damping) and material damping are measured using variable geometrical parameters of samples and under different environmental conditions. The equipment included a climatic chamber designed (built ad hoc) which was used to modify the surrounding air pressure. Results show the relationship between damping coefficients and sample geometry caused by variation in air flow resistance and the relationship between quality factor and air pressure. The experimental results will provide a useful data source for validating analytic models and calibrating simulations. A thorough discussion about interferometry applied to experimental mechanics of MEMS will also contribute to the reduction of the knowledge gap between specialists in optical methods and microsystem designer

Development and integration of AM lattice structures to reliable technological solutions

Additive manufacturing is allowing since several years the fabrication of metal lattice structures with high resolution, especially thanks to the increasing performances of DMLS (direct metal laser sintering) processes. The mechanical behavior of lattice structures depends primarily to the parent material, however it can be significantly modified or adjusted by means of the design of single cell and the 3D cells stacking. The most known advantages associated to engineered cellular structures are lightweight and thermal exchange, although advanced functionalities are appearing in the fields of materials joints and energy absorption. The applications of these properties are wide and include biomechanics/bioengineering, micromechanics, human-machines interfaces (HMI), sport and traditional mechanics (machines, vehicles, plants, etc.) The most recent projects released by the “Smart Structures and Systems” Lab. include the AM processes optimization for qualified and repeatable production of lattices at industrial quality level, the design methodologies linked to reduced-order modeling, the testing for reliability, and the development of patented technologies exploiting metal AM lattice structures

Lattice structures with stiffness gradient for loads transfer at bone-prosthesis interface

The fabrication of prostheses for orthopedic implants exploits additive technologies based on powder micromelting. The shape modularity, the biocompatibility of materials and the qualification procedures required by normative motivated the application of additive manufacturing since several years. The bone-prosthesis interface has great importance in implant integration, preventing prosthesis rejection and limiting time-scheduled prosthesis replacements. The load transfer between metal structures and bone requires precise modulation to stimulate the strength of new tissues. The design of lattice structures based on modular 3D stiffness variation is described in this paper, with special focus on the modeling methods based on homogenization approach

Strain-based method for fatigue failure analysis of truss lattice structures: modeling and experimental setup

Lattice structures, as a subclass of cellular solids, are nowadays among the most promising materials when it comes to lightweight engineering: their excellent mechanical properties, together with their functionality and reduced mass, make them the perfect candidates for many applications in the aerospace and automotive fields. Such sectors require though demanding specifications for their components: among all, fatigue resistance is extremely important. A simplified method for the fatigue analysis of lattice structures, based on finite element method (FEM) is proposed: through linear homogenization of the lattice structure, a lighter FEM model employed for the fatigue failure analysis is developed. Second step of the model is the application of de-homogenization on the most critical cell and therefore the recovery of the true state of the lattice. In this investigation, the method is employed in the case of a 4-point bending cyclic load, together with the presentation of a validating experimental setup

electro mechanical endurance tests on smart fabrics under controlled axial and friction forces

Abstract The design, building and validation of machine for endurance tests on fabrics are described in this paper. The system is addressed to the reliability testing of smart fabrics with electrical conductivity. The development of e-textiles, in fact, requires innovative test benches for the evaluation of performances decay with load cycles accumulation; the proposed system is able to monitor the electro-mechanical parameters of fabric sample in the same time in order to support industrial development and predict failures on final applications

integrated sensing system for upper limbs in neurologic rehabilitation

Abstract Wearable sensing devices for monitoring physiological parameters have proved their benefits in reducing the recovery time of mobility and in restoring the neuro-cognitive processes underlying the movement of the body. This is particularly evident in neurological patients from trauma or degenerative diseases. This kind of devices are generally wired sensors fixed on flexible supports, with complicated configuration and calibration. The work presented here has the goal to provide the design and implementation of a training system for rehabilitation including seven types of sensors, dedicated areas for data transmission in wireless mode, power management and signal multiplexing

Integration of Strain Sensors on Additively Manufactured Implantable Devices

The development of personalized healthcare is rapidly growing thanks to the support of low-power electronics, advanced fabrication processes and secured data transmission protocols. Long-acting drug delivery systems able to sustain the release of therapeutics in a controllable manner can provide several advantages in the treatment of chronic diseases. Various systems under development control drug release from an implantable reservoir via concentration driven diffusion through nanofluidic membranes. Given the high drug concentration in the reservoir, an inward osmotic fluid transport occurs across the membrane, which counters the outward diffusion of drugs. The resulting osmotic pressure buildup may be sufficient to cause the failure of implants with associated risks to patients. Confidently assessing the osmotic pressure buildup requires testing in vivo. Here, using metal and polymer AM (additive manufacturing) processes, we designed and developed implantable drug reservoirs with embedded strain sensors to directly measure the osmotic pressure in drug delivery implants in vitro and in vivo

Glove-based systems for medical applications: review of recent advancements

Human hand motion analysis is attracting researchers in the areas of neuroscience, biomedical engineering, robotics, human-machines interfaces (HMI), human-computer interaction (HCI), and artificial intelligence (AI). Among the others, the fields of medical rehabilitation and physiological assessments are suggesting high impact applications for wearable sensing systems. Glove-based systems are one of the most significant devices in assessing quantities related to hand movements. This paper provides updated survey among the main glove solutions proposed in literature for hand rehabilitation. Then, the process for designing glove-based systems is defined, by including all relevant design issues for researchers and makers. The main goal of the paper is to describe the basics of glove-based systems and to outline their potentialities and limitations. At the same time, roadmap to design and prototype the next generation of these devices is defined, according to the results of previous experiences in the scientific community