Claudia Pagano

Development of a gripping system based on capillary force

In this paper a new handling system, based on capillary force, is presented. The principle of the gripper mechanism is explained and a description of its main parameters and characteristics is given in order to model the system. Then, the theoretical and numerical models of the system are compared with experimental measurements and the reliability of the system is verified through a demonstration set-up

Handling and Manipulation of Microcomponents: Work-Cell Design and Preliminary Experiments

The paper introduces an experimental setup for the automatic manipulation of microcomponents, based on a 4 dof robot with Shoenflies motion and a two-camera vision system. The general architecture of the work-cell is presented. The work-cell functionality was tested via repeatability experiments using a set of vacuum grippers. Due to their intrinsic simplicity, vacuum grippers are very cheap and appear a promising solution for micromanipulation. An innovative nozzle for a vacuum gripper was designed, fabricated and tested, comparing its performance with traditional needles. The design was conceived to reduce the frequency of occlusions of the gripper and handle a wide range of particles. The performed tests evaluate the success and precision of the part release. Indeed, this is a crucial aspect of micromanipulation because microparts tend to stick to the gripper preventing the successful performance of manipulation tasks. The results confirm that adhesive effects prevent the release of components. For this reason different strategies were adopted in order to improve the efficiency in the release of stuck components. This solution increases the percentage of release and, setting appropriately the intensity of the pressure, it does not affect negatively the accuracy nor the repeatability of the positioning.

Micro-FDM process capability and comparison with micro-injection moulding

In recent years, fused deposition modelling technology (FDM) has become one of the most important additive manufacturing technology due to its capability to produce functional prototypes with complex shape in a cost effective way. Recently, the trend towards miniaturization invested also this technology, since the request of micro-component is rapidly growing due to the increasing number industrial sectors involved. Mechanical properties are fundamental in some sectors of high-quality micro-parts, so the knowledge of the influence of FDM process parameters on mechanical properties can be useful to extend its application and help the optimization of the parameter selection. In this context, the aim of this study is the analysis of the FDM capability and the room for improvement, through a comparison with a well-consolidated industrial process, such as the micro-injection moulding. Although FDM quality cannot compete with the technologies industrially used for final products, its low cost and short time are very attractive for some applications. Moreover, the comparison can be interesting since FDM is often used to manufacture prototypes eventually made with more performing industrial technologies, so that a measure of the quality and functionality of these prototypes can be extremely useful for product developers.In recent years, fused deposition modelling technology (FDM) has become one of the most important additive manufacturing technology due to its capability to produce functional prototypes with complex shape in a cost effective way. Recently, the trend towards miniaturization invested also this technology, since the request of micro-component is rapidly growing due to the increasing number industrial sectors involved. Mechanical properties are fundamental in some sectors of high-quality micro-parts, so the knowledge of the influence of FDM process parameters on mechanical properties can be useful to extend its application and help the optimization of the parameter selection. In this context, the aim of this study is the analysis of the FDM capability and the room for improvement, through a comparison with a well-consolidated industrial process, such as the micro-injection moulding. Although FDM quality cannot compete with the technologies industrially used for final products, its low cost and short time are...

Devices and Techniques for Contact Microgripping

The gripping and manipulation of microparts significantly differs from the handling and assembly of macroscopic components. In the macroworld gravity dominates, whereas in the microdomain, it becomes negligible, and superficial forces dominate pick and place operations. Releasing a part from the grasp of a microgripper is not a simple task as the part may stick to the gripper due to the presence of these adhesive forces. For this reason, beside the numerous attempts of downscaling traditional grippers also innovative actuation strategies have been proposed. The chapter critically reviews some of the most widely used micromanipulation techniques with contact, highlighting their advantages and disadvantages and describing some innovative solutions based on capillary forces.

Micro Injection Moulding Process and Product Characterization

Due to its high efficiency for the large scale production of polymeric parts, micro injection moulding is one of the key technologies of the new millennium. Although a lot of researches have been conducted to identify the most effective processing conditions for micro injection moulding, the comprehension of the influence of all parameters on the quality, the properties and the reliability of the moulded parts is still an issue. In this context, this study aims to evaluate the effects of the micro injection moulding process conditions on the tensile properties of micro parts, investigating the influence of three main process parameters: the injection speed, the mould temperature and the melt temperature. A full factorial plan has been applied to study the contributions of these parameters and a second study has been performed to understand the synergic interaction between the two temperatures on the tensile strength. Due to its high level of potential crystallinity, a typical semi-crystalline thermoplastic resin was used in the experiments. The results of the analysis showed a great influence of the mould temperature (Tmould ) on the ultimate tensile strength and of the melt temperature (Tmelt ) on the deformation at the point of breaking; whereas the injection speed was significant on the overall mechanical performance. A new studied factor (Tmelt -Tmould ) could affect the resulting molecular structure and consequently the mechanical behaviour, but itself is not sufficient to thoroughly explain the observed behaviour. Moreover, the visual inspection of the deformation mechanism at break shows three distinctive trends demonstrating the great variability of the mechanical properties of micro-injected specimens due to process conditions.Copyright

Mechanical characterisation and replication quality analysis of micro-injected parts made of carbon nanotube/polyoxymethylene nanocomposites

The increasing demand for small and cheap parts is boosting the development of reliable micro-system technologies. Fabrication process capabilities should expand to encompass a wider range of materials and geometric forms, which can satisfy the specific requirements of new emerging micro-products, and ensure the compatibility of new materials and processing technologies. Polymeric composites are very promising materials, since they offer new combinations of properties not available in traditional homogeneous materials. Because of their advantageous light weight, high strength, fatigue life, and corrosion resistance, they are forecast to replace conventional materials in several applications. Among the plastic process technologies, injection moulding is one of the key technologies for manufacturing miniaturised components due to its mass production capability and relatively low production cost. Micro-injection moulding allows to transfer micron and even submicron precision features to small products. Since final product properties strongly depend on materials and production processes and parameters, the process conditions of compounding as well as of product manufacturing have to be carefully studied and controlled. This is particularly important for the manufacturing of micro-products, since, at the micro-scale, some phenomena negligible at the macro-scale (as hesitation effect or capillarity forces for examples) can become important. However, only few studies concern the micro-injection of nanocomposites. Therefore, in this paper the micro-injection of two composites made of polyoxymethylene and carbon nanotubes has been studied. First, the electrical properties of the compounds have been measured; the fillers are dispersed in the matrix and form a network that dramatically increases the conductivity of the composites in comparison with the pristine resin. Then the compounds have been injected using a micro-injection machine and the components have been analysed. The mechanical analysis, based on tensile tests and dynamic-mechanical experiments on miniaturised dog-bone specimens, shows a slight reinforcing effect of the filler; however, the ductility is considerably reduced. This is likely due to a scarce adhesion of the carbon nanotubes and the polymer and the presence of some agglomerates. Moreover, as expected, the mould temperature affects the mechanical properties of the specimens, probably due to its effect on the internal structure of the solidified materials. The dimensional analyses carried out on micro-rib specimens show that replication capability is increased by the presence of the filler and using high values of the process parameters. Finally, microscopic analyses have been done in order to verify the dispersion and orientation of the fillers in the compounds. These effects have been observed only when high shear rates are involved.

Introduction to Miniaturisation

Miniaturisation of systems and devices is a trend that started a few decades ago, and which is becoming more and more relevant to our everyday lives. The concept of micro-manufacturing evolved as a direct result of manufacturing technologies used for integrated circuit fabrication. These allowed batch processing, but limited the range of materials and geometries. A range of micro-manufacturing technologies has been developed to overcome these limitations. The aim of this chapter is to review the main physical phenomena related to miniaturisation, in terms of scaling laws, forces, materials, processes and production systems. Indeed, when approaching the micro-scale, some physical phenomena considered negligible at the macro-scale, become significant and have to be taken into account in the design, manufacturing, and assembly of micro-devices.

Nanomechanical Property Analysis of Silica Aerogel

Aerogels (AGs) are open-cell nanofoams. AGs are lightweight and possess high thermal and acoustic insulation properties. Due to their ∼ 90% porosity, AGs are very brittle and fragile, which inhibits its use for load-bearing applications. For this reason an area of open research is the study and improvement of the mechanical properties of aerogels without altering their unique properties. Due to the extreme brittleness and low applied stress that AGs can support, direct mechanical measurements of AGs are challenging. To date very few experiments have been carried out to characterize the mechanical properties of aerogels; in particular at small contact dimensions and ultralow loads (nN-μN). In this paper, silica aerogel has been studied by nanoindentation using a diamond Berkovich indenter. We characterize the elasticity, stiffness, and hardness of the material as a function of contact depth (≤ 500 nm) at ultralow loads. The modulus and hardness are shown to change with depth with moduli and hardness ranging from 15–23 MPa and 3.5–6.8 MPa, respectively.Copyright

Monodirectional Positioning Using Dielectric Elastomers

The rationales for the use of microsystems are numerous, including the reduction of consumables, a faster response time, the enhanced portability, the higher resolution, and the higher efficiency; moreover their application sectors are numerous. Nevertheless microproducts have still great difficulty in penetrating the market, mainly due to the limits of the fabrication processes. The hybrid approach is suitable for the fabrication of three dimensional microscopic structures but often requires manual contributions, which are time consuming and expensive. In order to overcome these issues, new materials and new techniques for the manipulation of microcomponents, based on innovative principles, have been conceived and have to be further developed. In this paper polymeric smart materials, namely electroactive polymers, have been theoretically and experimentally investigated towards their implementation in the actuation and sensing of positioning and handling devices. The feasibility of a monodirectional positioner has been studied.

Basic Characterization of a Linear Elastomer Actuator

Innovative types of actuators are required for several applications, especially in the field of medicine, robotics and micro-systems. In this context, Electroactive Polymers represent a promising group among all smart materials. They can change their dimensions and shape when an external voltage is applied, and their mechanical flexibility and ease of processing offer advantages over traditional electroactive materials expanding the options for different mechanical configurations. Dielectric elastomers are among the most promising EAPs for many applications, including actuators and sensors for the microfactory: they work in a dry environment, can achieve great deformations and support high voltage. They can be represented by a parallel plate capacitor: under an electric field the elastomer is squeezed in the thickness causing expansion in the transverse direction. Dielectric EAP actuators require large electric fields (hundreds of kV/mm) but can produce very large strain (up to 400%). Due to their unique properties and potential applications, in this paper the study of the electromechanical behaviour of a dielectric elastomer and a possible application related with the microfabrication of hybrid microsystem is presented.Copyright