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LORENZO NICOLINI
Dottorando
Dipartimento di Scienze e Metodi dell'Ingegneria
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Pubblicazioni
2024
- A biomimetic chiral auxetic vertebral meta-shell
[Articolo su rivista]
Sorrentino, A; Genovese, K; Nicolini, L; Castagnetti, D
abstract
The work presents a novel thin-walled biomimetic auxetic meta-shell for patient-specific
vertebral orthopedic implants. The proposed design stemmed from the concept of an intrinsically multiple curved auxetic meta-structure, which is created by folding a two-dimensional bio-inspired chiral geometry according to the morphology of human vertebral
cortical bones. Through a multi-view stereo digital image correlation system, we investigated the mechanical response of a bio-grade titanium (Ti6Al4V ELI) additively manufactured prototype of the meta-structure under compressive loadings. In addition, we analyzed the morphology of the prototype using a scanning electron microscopy and an optical image dimension measurement system both before and after compressive tests. An accurate Finite Element model, which exactly reproduced the geometry of the three-dimensional printed meta-shell, was implemented and calibrated against experimental results, obtaining a precise prediction tool of its mechanical response. The findings of this work demonstrate that the designed meta-shell shows a peculiar auxetic behavior, a targeted stiffness matching to that of human vertebral bone tissues and a higher global elastic strain capability compared to those of monolithic traditional vertebral body replacements.
2024
- A wideband low frenquency 3D printed electromagnetic energy harvester based on orthoplanar springs
[Articolo su rivista]
Nicolini, Lorenzo; Castagnetti, Davide
abstract
Electromagnetic energy harvesters are commonly known for their high performances in terms of power output
conversion, and they are suitable for low frequency environmental vibrations.
This work reports the study, design, development and experimental validation of a new extremely compact,
low frequency, electromagnetic energy harvester based on two stacked ortho-planar springs, which exploits a
promising magnets disposition.
The device is composed by two stacked ortho-planar springs connected externally by a rigid frame. The two
internal moving parts are connected to each other by a central pivot where an array of magnets is fixed on in a
peculiar disposition: a half has a magnetic field directed upward, while the other half directed downward. A
copper coil is wound into a housing fixed on the external frame. It comes a central massive cursor that axially
moves, exploiting the springs compliance, relatively to the external frame.
The prototype was almost completely realized by using Filament Fused Fabrication (FFF) additive
manufacturing process in Onyx material, carbon fibre reinforced nylon.
In the experimental assessment an oscillating excitation was applied on the external frame in multiple linear
sweep frequency tests with different amplitude signals. The experimental validation shows a large bandwidth,
from 10 to 30 Hz, and consistent output voltage and power signals.
2024
- Dispositivo antivibrante comprendente un elemento
elastomerico deformabile elasticamente con
proprieta’ piezoelettriche
[Brevetto]
Nicolini, L.; Castagnetti, D.; Sorrentino, A.
abstract
La presente invenzione riguarda l’ambito dei dispositivi antivibranti e in particolare un dispositivo antivibrante comprendente un elemento elastomerico deformabile elasticamente e avente proprietà piezoelettriche. L’invenzione riguarda, inoltre, un metodo di fabbricazione di tale dispositivo antivibrante.
2023
- A SOFT FREE SHAPE CASTED PIEZOELECTRIC ELASTOMER
[Relazione in Atti di Convegno]
Nicolini, Lorenzo; Sorrentino, Andrea; Castagnetti, Davide
abstract
Piezoelectric materials are largely used for sensing and energy harvesting
applications as simple and reliable solutions from piezoelectric accelerometers to vibration
energy harvesters. Most of the applications utilize either piezoceramic materials, exploiting
their high piezoelectric coefficients, or piezoelectric polymers, thanks to their soft response, in
applications where finite displacements are needed.
Actual piezoceramic materials are expensive, brittle and available only in standard and flat
shapes. On the other hand, piezoelectric polymers, like PVDF, are too stiff for many
applications that need softer solutions.
This work presents the study, development and validation of a new soft piezoelectric elastomer,
which can be designed in free shape through a casting process. This study identified a novel
formulation of a cold polymerizable silicone-based elastomer, enhanced with BaTiO3 (barium
titanate) powder.
A detailed procedure of fabrication was defined involving the mixture preparation, curing and
polarization phases of the solution. To obtain disk specimen, we designed and used a dedicated
3D printed acrylonitrile butadiene styren (ABS) mold with a cylindrical cavity. The mold
houses two steel electrodes for the polarization through a high voltage DC converter. This
allows to perform the polarization process at the same time of the polymerization in order to
easily orientate polar BaTiO3 particles in the liquid solution until the polymerization is
completed.
To experimentally evaluate the effect of the main variables on the fabrication procedure and
the piezopolymer response, we conducted a systematic test plan. Specifically, we investigated
both the effect of barium titanate powder concentration and voltage polarization level on the
morphological appearance of the specimen and on its piezoelectric properties. Two quasistatic
cyclic compression tests at different strain levels were performed on small cylindrical samples
cut by the specimens, registering the mechanical behaviours and electric voltage output signals.
The piezoelectric coefficient d33, calculated for all the configurations and for both strain levels,
highlights a remarkable performance of the proposed piezoelectric polymer.
2023
- A soft piezoelectric elastomer with enhanced piezoelastic response
[Articolo su rivista]
Nicolini, Lorenzo; Sorrentino, Andrea; Castagnetti, Davide
abstract
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.
2023
- RULLO SENSORIZZATO CON RIVESTIMENTO IN ELASTOMERO PIEZOELETTRICO
[Relazione in Atti di Convegno]
Nicolini, Lorenzo; Castagnetti, Davide
abstract
This study reports the realization of a sensed roller with a solid piezoelectric elastomer tread, realized and studied in a previous work of the authors. The device consists in a dedicated metallic rim externally covered by a thick layer of solid elastomer with piezoelectric properties, based on liquid polymerizable silicone combined with 50% by weight of piezoelectric ceramic powder BaTiO3. This application exploits the characteristics of the studied material to provide a voltage signal between the rim wheel and an electrically conductive rolling plain, in order to achieve information about position, velocity and vertical load index applied on the roller. This study describes the device’s working conceptual model, the realization procedure through casting in a dedicated mould and curing process of the external tread, and the testbench set up and working tests of the device.
2023
- Un guscio vertebrale in meta-biomateriale auxetico chirale
[Relazione in Atti di Convegno]
Sorrentino, A.; Genovese, K.; Nicolini, L.; Castagnetti, D.
abstract
Il lavoro si focalizza sulla progettazione, simulazione, prototipazione e convalida sperimentale di un’innovativa struttura a guscio in metamateriale auxetico chirale, realizzata in lega di titanio in stampa 3D. La struttura presenta una morfologia simile a quella delle ossa vertebrali corticali umane e un valore del coefficiente di Poisson negativo. Mediante un sistema di correlazione digitale di immagini (stereo-DIC), il lavoro misura il campo di spostamento e di deformazione del metamateriale sottoposto ad una prova di compressione quasi-statica, e confronta i risultati con quelli ottenuti da un modello 3D agli elementi finiti della struttura. La microstruttura della superficie del prototipo è stata analizzata utilizzando un microscopio elettronico a scansione SEM. L’architettura di metamateriale proposta si distingue per un elevato comportamento auxetico, rimane elastica fino ad uno schiacciamento della struttura del 3%, e si caratterizza per una rigidezza simile a quella dell’osso vertebrale umano.
2023
- 3D printed passive end-effector for industrial collaborative robotic arms
[Articolo su rivista]
Nicolini, L.; Sorrentino, A.; Castagnetti, D.; Spaggiari, A.
abstract
The work focuses on the design and prototyping of a novel end-effector for a collaborative robotic arm allowing to grab
and drag industrial packages without lifting them. The proposed solution consists of a passive 3D-printed end-effector
manufactured using carbon fibre reinforced Onyx material. Thanks to the entirely passive mechanical actuation that
exploits the compliance of the main chassis, this end-effector features a simple, scalable, and inexpensive structure.
This lightweight end-effector is specifically designed for small and low payload collaborative robotic arms. Specifically,
the proposed end-effector includes three main parts. First, a thin blade, with the main function of separating boxes
that are close to each other. Second, a rocker arm - rod mechanism, which allows an opposable bracket to be moved
in order to grab the correspondent package. This is proportionally and passively actuated by the contact pressure
between the package, during its grip, and a paddle (third part), which is composed of a flat leverage and three flexural
springs to counterbalance the pushing force. This paddle and the main body of the gripper were designed as a single
part exploiting 3D printing manufacturing capabilities. Moreover, we implemented a Simscape dynamic model that pre-
dicts the functionality of the end-effector during standard operations. The work shows how to design, develop and val-
idate a new low cost, passive end-effector mainly oriented to collaborative robots. The final prototype demonstrates its
entire functionality, and proves fabricability through 3D printing, thus minimizing production costs, weight, and time.
2022
- A tunable multi-arm electromagnetic pendulum for ultra-low frequency vibration energy harvesting
[Articolo su rivista]
Nicolini, Lorenzo; Castagnetti, Davide; Sorrentino, Andrea
abstract
Autonomous electronic devices and sensors are essential to reduce expensive maintenance,
increasing job security and reliability, avoiding battery replacements and wired systems.
Industrial systems and civil structures vibrate dissipating an important amount of energy that
can be harvested to power small devices. This work continues and extends a previous work from
the authors (Castagnetti 2019 Meccanica 54 749–60). Here we improved that initial
configuration by proposing a tunable multi-arm electromagnetic pendulum for ultra-low
frequency vibrations energy harvesting. This configuration features five electromagnetic
converters and a magnetic spring, each supported by a pendulum arm with different length:
when excited by external vibrations, this six arms frame is free to oscillate around a central
pivot. The paper starts from conceptual design, includes a detailed multiphysics dynamic
simulation implemented with Matlab Simscape software, presents the prototype development
through three-dimensional printing and experimental validation. Systematic experimental tests
investigated different pendulum configurations for three stiffness levels of the magnetic spring
and confirmed both the ultra-low frequency response (from 2 to 10 Hz), as predicted by the
dynamic simulation, and the good voltage and power outputs. Specifically, for the higher
stiffness of the magnetic spring, corresponding to an oscillation frequency of about 9.5 Hz, the
power output was up to 8.4 mW and the output voltage of about 2 Volt.
2022
- Modello multifisico di un convertitore elettromagnetico a pendolo per il recupero di energia da vibrazioni ambientali
[Relazione in Atti di Convegno]
Nicolini, Lorenzo; Castagnetti, Davide; Sorrentino, Andrea
abstract
Il lavoro presenta lo sviluppo di un modello multi-fisico che simula il funzionamento di un pendolo per il recupero di energia dalle vibrazioni ambientali a bassa frequenza mediante convertitori elettromagnetici. La dinamica del dispositivo può essere associata a quella di un sistema massa-molla-smorzatore rotante. La molla è caratterizzata da magneti che si attraggono con una legge fortemente non lineare e lo smorzamento è causato dalla conversione di energia. Il modello simulativo è descritto in due parti principali: la dinamica sviluppata in un modello multi-body che include anche la sorgente delle vibrazioni e i segnali di output, e l’analisi EF del campo magnetico generato dai magneti permanenti dei convertitori. Combinando il modello multi-body con i risultati ottenuti nell’analisi agli elementi finiti si ottiene una descrizione completa e accurata del funzionamento del dispositivo, confermata dal confronto con il prototipo reale durante una campagna di test sperimentali.
2022
- Modello multi-fisico di un convertitore elettromagnetico di energia con architettura a pendolo per basse frequenze
[Relazione in Atti di Convegno]
Nicolini, L.; Castagnetti, D.; Sorrentino, A.
abstract
2022
- 3D printed passive end-effector for industrial collaborative robotic arms
[Poster]
Nicolini, Lorenzo; Sorrentino, Andrea; Castagnetti, Davide; Spaggiari, Andrea
abstract