A soft piezoelectric elastomer with enhanced piezoelastic response

This work aims to study, develop, and validate a soft piezo-polymer with enhanced piezo-elastic response and easy castable in a free shape through a single and easy process. The work identified a novel formulation for soft piezopolymers based on ambient temperature polymerizable silicone rubber, easily fabricable in 3D printed plastic moulds. Combining polymerizable silicone with a barium titanate (BaTiO3) ceramic powder and defining a detailed fabrication procedure of casting, curing and high voltage poling, we defined how to obtain a promising soft piezoelectric elastomer for countless sensing applications. This study includes information about the mould design used to realize, cure and polarize cylindric elastomeric specimens. This piezopolymer stands out for its flexibility, softness, easy fabrication at ambient temperature and obtainability in multiple shapes and bulky 3D geometries. Finally, we investigated different configurations of the piezopolymer formulation analysing the powder concentration and voltage polarization effects over the mechanical, piezoelectric and morphological characteristics. The specimens exhibit a high induced polarization d33 with values up to 22.5 pC N−1 , comparable with poled β-phase polyvinylidene difluoride. We finally underlined limits encountered in the most extreme configurations

Thermal and mechanical characterization of complex electrospun systems based on polycaprolactone and gelatin

Nowadays, continuous development of soft-electronics and wearable devices opens to the development needs of stretchable and fexible materials able to interface with the human body. In this scenario, biopolymers are particularly intriguing materials given their biocompatibility and biodegradability. For the application in this specifc feld the material requires several properties such as biological and mechanical performance and thermal stability. In this study, membranes able to fulfll some of these requirements are described. The electrospun membranes, composed of a blend of polycaprolactone (PCL) and gelatin (GN), have been produced in various confgurations. The results show how blend or coaxial systems have diferent efects on both the interactions between the polymers and their thermal and mechanical properties. An important result of the chosen experimental conditions is the narrow dimensional distribution of the nanofber diameters constituting the electrospun membranes. Thermal and mechanical tests evidenced that, by properly choosing the material composition and the method of the electrospinning process, membranes capable of withstanding high strain values before the failure can be obtained. In particular, optimizing the electrospinning process and using a blend PCL/GN with a mass ratio of 80/20, it is possible to increase the thermal stability up to 310 °C and confer to the sample the ability to reach a percentage of strain up to 350%

evaluation of the spring in of cfrp thin laminates in dependence on process variation

Abstract The cure process of CFRP laminates induces residual stress inside the parts that causes geometrical unconformities. The most important unconformity is the spring-in that means the deviation of the flange-to-flange angle from the design angle. The spring-in value depends on some process parameters, such as the lay-up sequence of the plies, as demonstrated in previous works. The aim of this work is to study the dependence of the spring-in on the deviations in the orientation of the plies due to a hand process. A numerical tool was developed and experimentally tested

Studies of Lithium-Oxygen Battery Electrodes by Energy- Dependent Full-Field Transmission Soft X-Ray Microscopy

Energy‐dependent full‐field transmission soft X‐ray microscopy is a powerful technique that provides chemical information with spatial resolution at the nanoscale. Oxygen K‐level transitions can be optimally detected, and we used this technique to study the discharge products of lithium‐oxygen batteries, where this element undergoes a complex chemistry, involving at least three different oxidation states and formation of nanostructured deposits. We unambiguously demonstrated the presence of significant amounts of superoxide forming a composite with peroxide, and secondary products such as carbonates or hydroxide. In this chapter, we describe the technique from the fundamental to the observation of discharged electrodes to illustrate how this tool can help obtaining a more comprehensive view of the phenomena taking place in metal air batteries and any system involving nanomaterials with a complex chemistry

Chapter Studies of Lithium-Oxygen Battery Electrodes by Energy- Dependent Full-Field Transmission Soft X-Ray Microscopy

The employment of printing techniques as cost-effective methods to fabricate low cost, flexible, disposable and sustainable solar cells is intimately dependent on the substrate properties and the adequate electronic devices to be powered by them. Among such devices, there is currently a growing interest in the development of user-oriented and multipurpose systems for intelligent packaging or on-site medical diagnostics, which would greatly benefit from printable solar cells as their energy source for autonomous operation

In Vitro Reconstructed Human Epithelial Models for Microbial Infection Research: Why Do We Need them?

In the last 50 years, the Replacement, Reduction and Refinement principles have become a framework for conducting high quality academic, pre-clinical, clinical and industrial research experimentation studies, in order to respond to the European Union legislative demand of alternatives to animal-based experimentation, often difficult to translate to human applications, expensive and not ethically approved. Thanks to the improvement of cellular isolation protocols, culture and co-culture conditions, together with the increased clinical demand, several novel in vitro three-dimensional tissue engineered human epithelial models, able to create sophisticate pre-clinical tests and produce results more reliable than the traditional bi-dimensional flat cell culture systems, have been developing also for microbial infection research purposes

Design of self‑healing biodegradable polymers

A biodegradable thermoplastic polymer has been formulated by solubilizing Murexide (M) salts in a commercial biodegradable vinyl alcohol copolymer (HVA). The Murexide has been employed as a self-healing fller with the aim to impart the auto-repair ability to the formulated material. Three diferent percentages (1, 3, and 5 mass%) of fller have been solubilized in HVA to evaluate the efect of the fller concentration on the thermal and self-healing properties of the resulting polymeric materials. The samples have been thermally characterized by Diferential Scanning Calorimetry (DSC) and Thermogravimetric Analyses (TGA), while their self-healing ability has been evaluated through the estimation of the storage modulus recovery, measured by Dynamic Mechanical Analysis (DMA). The results of DSC analysis have highlighted that the increase of the amount of Murexide anticipates the thermal events such as glass transition, crystallization and melting. TGA measurements have evidenced that, although there is a reduction of thermal stability of the materials in the presence of a high concentration of M, the polymer still remains stable up to 270 °C. Healing efciency higher than 80%, at a temperature beyond 60 °C, has been detected for the samples loaded with 3 and 5 mass% of Murexide, thus confrming the efcacy of this compound as an auto-repair agent and the relationship between the self-healing efciency and its amount. For a temperature lower than 70 °C, the healing tests, carried out at diferent values of tensile deformation frequency, have highlighted a frequency-dependent healing efciency. This dependence becomes negligible at higher temperatures for which the healing efciency approaches the value of 100%

A Hardware-in-the-Loop Approach to Test Rotary Electromagnetic Shock Absorbers

Electromagnetic shock absorbers are mechatronic actuators designed to improve ride comfort and road holding in ground vehicles by introducing variable active and damping forces in the suspension. This feature difficults their testing, as the characterization test bench must adapt to this variable load feature. Moreover there is interest in testing them under realistic use scenarios. In this context, this work focuses on a hardware-in-the-loop implementation on a custom damper test bench to characterize rotary electromagnetic shock absorbers. First, the entire test bench is presented and described. The model of the plant is obtained together with a quarter car model of the target vehicle. Test bench bandwidth and instability issues are discussed. Then, a model following compensation method is proposed and simulated. Finally, the resulting approach is used to control a testbed, where the quarter car model is used to produce a realistic load duty cycle in real time. Experiments highlight the tracking performance of the test rig and its robustness against load variations