Abstract: The growing importance of state assessments in civil engineering has led to intensive research into the development of damage identification methods based on vibrations. Natural frequencies and modal shapes have garnered great interest because modal parameters are invariant of structure. Moreover, thanks to the global nature of modal parameters, their variations are not limited to the location of the damage. This is an important advantage that offers the opportunity to identify damage with sensors whose position does not have to coincide with the damaged area. The integration of MEMS sensors into structural health monitoring (SHM) systems offers a promising approach to long-term structural maintenance, especially in large-scale infrastructure. This paper presents an anomaly detection technique that analyzes raw sequential data within a statistical framework to detect damage that causes prestress loss of the tendon by exploiting a distributed monitoring system composed of six high-performance MEMS sensors. The proposed system is preliminarily evaluated to identify the frequency of the first mode, and then the proposed methodology is validated on acceleration data collected on a 240 cm beam in three different damage configurations, achieving a high detection accuracy and showing that its output can also evaluate the damage localization.

Keywords: anomaly detection | distributed monitoring system | frequency domain decomposition | MEMS | structural health monitoring

Abstract: Objectives: This study aimed to investigate the biocompatibility, osteogenic and antibacterial activity of biomedical devices based on Magnesium (Mg) Alloys manufactured by Superplastic Forming process (SPF) and subjected to Hydrothermal (HT) and Sol-Gel Treatment (Sol-Gel). Methods: Mg-SPF devices subjected to Hydrothermal (Mg-SPF+HT) and Sol-Gel Treatment (Mg-SPF+Sol-Gel) were investigated. The biocompatibility of Mg-SPF+Sol-Gel and Mg-SPF+HT devices was observed by indirect and direct cytotoxicity assays, whereas the colonization of sample surfaces was assessed by confocal microscopy. qRT-PCR analysis and microbial growth curve analyses were employed to evaluate the osteogenic and antibacterial activity of both SPF-Mg treated devices, respectively. Results: Mg-SPF+HT and Mg-SPF+Sol-Gel showed a high degree of biocompatibility. Analysis of mRNA expression of osteogenic genes in cells cultured on Mg-treated devices revealed a significant upregulation of the expression levels of BMP2 and Runx-2. Furthermore, the bacterial growth in strains developed in contact with both the Mg-SPF+HT and Mg-SPF+Sol-Gel devices was lower than that observed in the control. Significance: Hydrothermal and Sol-Gel Treatments of Mg alloys obtained through the SPF process demonstrated bioactive, osteogenic and antibacterial activity, offering a promising alternative to conventional Mg-based devices. The obtained Mg-based materials may have the potential to enhance the tunability of temporary devices in maxillary reconstruction, eliminating the need for second surgeries, and ensuring a good bone reconstruction and a reduced implant failure rate due to bacterial infections.

Keywords: Antibacterial materials | Bone tissue engineering | Metallic biomaterials | Mg alloys | Resorbable implants

Abstract: The design of advanced devices is a paramount goal in the biomedical field. Current challenges include the development of customized devices with improved and tailored properties according to the specific application. Accordingly, the aim of the study was to report some recent efforts in the design of advanced biomedical devices, especially focusing on dental implants and hybrid structures for cranioplasty.

Keywords: Additive Manufacturing | Biomedical Applications | Design for Additive Manufacturing

Abstract: Additive manufacturing (AM) allows to create complex shapes and to improve the performance of critical components in different fields. The characteristics of the as-built parts can be an obstacle in terms of satisfaction of the parts’ quality requirements. Concerning the manufacturing process, the relationship among the process parameters, microstructure and mechanical properties is crucial in different areas and involves innovative and traditional fabrication techniques. Fused Deposition Modeling (FDM) is widely employed to fabricate devices with tailored and enhanced properties. In this context, the process parameters clearly influence the quality of devices fabricated from different polymer-based materials, according to the specific AM technology. As reported in the literature, many theoretical models for the prediction of the surface quality focus on the concept of roughness. Furthermore, several parameters have also been proposed to assess the surface quality. Benefiting from advances in design strategies and methodologies of analysis, the aim of the current research was to provide further insight into the development of models for surface roughness prediction in FDM. The relationship among the layer height, printing speed, flow rate and extrusion width was considered and implemented in the model. Preliminary experimental analyses were also performed.

Keywords: Additive Manufacturing | Prediction Model | Surface Roughness

Abstract: Purpose: This study aims to integrate design methods and additive manufacturing with the use of a thermoplastic elastomer certified for medical use and reverse engineering towards a new concept of a customized buttress model with optimized features for the reconstruction of the osteo-dural opening after endoscopic endonasal transtuberculum-transplanum approach. Design/methodology/approach: Additive manufacturing allows making of cost-effective and useable devices with tailored properties for biomedical applications. The endoscopic endonasal approach to the suprasellar area enables the management of different intradural tumours, and the craniectomy at the skull base is generally wide and irregular. Defining an optimal strategy for osteodural defect closure at the preoperative stage represents a significant challenge. Findings: Using the results obtained from a computed tomography analysis, skull base defects were designed to plan the surgical approach. Several concepts of customized buttress models were first built up, initially focusing on thin, flexible edges characterized by different thicknesses. Finite element analyses and design optimization allowed us to achieve the optimal design solution with improved compliance/flexibility for easy intranasal manoeuvrability, maintaining an adequate mechanical stability. As the thickness of the edges decreased, an increase of strain energy values was found (i.e. 1.2 mJ – Model A, 1.7 mJ – Model B, 2.3 mJ – Model C, 4.3 mJ – Model D). However, a further optimization (Model E) led to a significant increase of the compliance (strain energy of 14.1 mJ). Originality/value: The results obtained from clinical evaluations demonstrated the feasibility of the proposed technical solutions, improving surgery effectiveness.

Keywords: Design for additive manufacturing | Endoscopic endonasal approach | Finite element analysis | Mechanical measurements | Pituitary surgery | Reverse engineering

Abstract: Over the past years, a wide range of dental implants has been proposed. In general, the dentists may find the best solutions according to the specific needs of the patients. A variety of factors influences the level of osseointegration and, consequently, the anchorage of the implant to the bone. The stress transfer mechanism along the bone-implant interface depends upon the surface area of the bone-implant contact. Great efforts have been devoted to the design of 3D porous lattice structures with tailored architectural features in order to reduce the implant stiffness as well as to favour bone ingrowth, thus stabilizing the device. Accordingly, the aim of the current study was to provide further insight into the design criteria for dental implants. In particular, starting from a screw implant (Implant A), different concepts of dental implants were developed: i) Implants B1–B5, with lattice shell surrounding a solid core, without thread; ii) Implant C, with lattice structure; iii) Implant D as topography optimized implant. Finite element analysis on the several models of bone-implant provided interesting information in terms of stress distributions in cortical and trabecular bone. Some differences among the implants may be ascribed to the different design criteria.

Keywords: Dental implants | Design criteria | Finite element analysis | Lattice structure | Topography optimization | Topology optimization

Abstract: Creative design methods should allow the extraction of novel wisdoms and favour their integration into many technological domains, thus leading to an innovative product. The current research reports some technical considerations on the role of generative design as a “collaborative partner” in supporting the ideation process through the development of design alternatives in agreement with the designer’s criteria. A specific case study was considered and the role of the generative design method was stressed, also focusing on technical features and differences in terms of solutions for the given design problem. The possibility of selecting well defined manufacturing methods (e.g., traditional or advanced – additive manufacturing) was highlighted.

Keywords: additive manufacturing | design methods | development | Generative design | mechanical measurements | product design

Abstract: Additive manufacturing (AM) techniques are based on the process of joining materials, layer upon layer, differently from subtractive manufacturing methods. The design for AM allows for the creation of complex shapes as well as for the improvement of the performance of critical components in several fields, spanning from aerospace and automotive to biomedical applications. On the other hand, unlike man-made high load-bearing capacity devices, which are usually dense solids, nature uses mesoscopic or microscopic cellular structures as a fundamental support for the design. The increasing applications of AM in industrial production have led to product reimagination from a novel standpoint, enabling the fabrication of advanced lattice structures using polymer-based materials. Over the past few years, many efforts have been made to develop strategies for finding the design which is best suited to the requirements. In the current research, specific design scenarios were explored, the aim being to develop novel lattice structures for energy absorption, using an AM technique (i.e., fused deposition modelling) and a modified Acrylonitrile Styrene Acrylate (ASA)-based material. The fabricated structures were preliminarily analysed by means of compression tests.

Keywords: Design for Additive Manufacturing | Lattice Structures | Mechanical and Functional Analysis

Abstract: The concept of magnetic guidance has opened a wide range of perspectives in the field of tissue regeneration. Accordingly, the aim of the current research is to design magnetic responsive scaffolds for enhanced bone tissue regeneration. Specifically, magnetic nanocomposite scaffolds are additively manufactured using 3D fibre deposition technique. The mechanical and magnetic properties of the fabricated scaffolds are first assessed. The role of magnetic features on the biological performances is properly analyzed.

Keywords: bone tissue engineering | design for additive manufacturing | magnetic nanocomposite scaffolds | mechanical and functional properties

Abstract: A wide range of materials has been considered to repair cranial defects. In the field of cranioplasty, poly(methyl methacrylate) (PMMA)-based bone cements and modifications through the inclusion of copper doped tricalcium phosphate (Cu-TCP) particles have been already investigated. On the other hand, aliphatic polyesters such as poly (e-caprolactone) (PCL) and polylactic acid (PLA) have been frequently investigated to make scaffolds for cranial bone regeneration. Accordingly, the aim of the current research was to design and fabricate customized hybrid devices for the repair of large cranial defects integrating the reverse engineering approach with additive manufacturing, The hybrid device consisted of a 3D additive manufactured polyester porous structures infiltrated with PMMA/Cu-TCP (97.5/2.5 w/w) bone cement. Temperature profiles were first evaluated for 3D hybrid devices (PCL/PMMA, PLA/PMMA, PCL/PMMA/Cu-TCP and PLA/PMMA/Cu-TCP). Peak temperatures recorded for hybrid PCL/PMMA and PCL/PMMA/Cu-TCP were significantly lower than those found for the PLA-based ones. Virtual and physical models of customized devices for large cranial defect were developed to assess the feasibility of the proposed technical solutions. A theoretical analysis was preliminarily performed on the entire head model trying to simulate severe impact conditions for people with the customized hybrid device (PCL/PMMA/Cu-TCP) (i.e., a rigid sphere impacting the implant region of the head). Results from finite element analysis (FEA) provided information on the different components of the model.

Keywords: Composite bone cement for cranioplasty | Design for additive manufacturing | Finite element analysis | Reverse engineering | Temperature profile analysis

Abstract: Recently, a variety of craniofacial approaches has been adopted to enter the skull base, including the endonasal endoscopic technique. An effective watertight technique, the reconstruction can be performed using different materials, both autologous and non-autologous, individually or combined in a multilayer fashion. The current study focuses on the development of new advanced devices and techniques that help to reduce the postoperative cerebrospinal fluid leak rate. Additive manufacturing allows the design of devices with tailored structural and functional features, as well as injectable semi-interpenetrating polymer networks and composites; therefore, specific mechanical/rheological and injectability studies are valuable. Accordingly, we propose new additive manufactured and injectable devices.

Keywords: Additive manufacturing | CSF leakage | Design of injectable systems | Endoscopic endonasal surgery | Reverse engineering | Skull base reconstruction

Abstract: Additive manufacturing represents a powerful tool for the direct fabrication of lightweight and porous structures with tuneable properties. In this study, a fused deposition modelling/3D fibre deposition technique was considered for designing 3D nanocomposite scaffolds with specific architectures and tailored biological, mechanical, and mass transport properties. 3D poly(ε-caprolactone) (PCL)/hydroxyapatite (HA) nanocomposite scaffolds were designed for bone tissue engineering. An optimisation design strategy for the additive manufacturing processes based on extrusion/injection methods was at first extended to the development of the PCL/HA scaffolds. Further insight into the effect of the process parameters on the mechanical properties and morphological features of the nanocomposite scaffolds was provided. The nanocomposite structures were analysed at different levels, and the possibility of designing 3D customised scaffolds for mandibular defect regeneration (i.e., symphysis and ramus) was also reported.

Keywords: Additive manufacturing | Design of Experiments | Nanocomposites | Reverse Engineering | Scaffold Design and Analysis

Abstract: It has been widely reported that breast reconstruction improves the quality of life of women who undergo mastectomy for breast cancer. This approach provides many psychological advantages. Today, different techniques are available for the breast oncoplastic surgeon that involve the use of breast implants and autologous tissues, also offering interesting results in terms of aesthetic and patient-reported outcomes. On the other hand, advanced technologies and design strategies (i.e. design for additive manufacturing, reverse engineering) may allow the development of customised porous structures with tailored morphological, mechanical, biological, and mass transport properties. For this reason, the current study deals with the challenges, principles, and methods of developing 3D additive manufactured structures in breast reconstructive surgery. Specifically, the aim was to design 3D additive manufactured poly(ε-caprolactone) scaffolds with different architectures (i.e. lay-down patterns). Preliminary mechanical and biological analyses have shown the effect of the lay-down pattern on the performances of the manufactured structures.

Keywords: Additive manufacturing | Breast reconstructive surgery | Fat grafting | Functional properties | Mechanical | Pore geometry and lay-down pattern | Reverse engineering | Scaffold design

Abstract: In the last decades a variety of innovative craniofacial approaches has been adopted to entire skull base. The endonasal endoscopic route has emerged as a suitable methodology for several skull base lesions. An effective watertight closure is essential to isolate the intracranial cavity in order to restore the natural intra and extradural compartment division, necessary to prevent postoperative cerebrospinal fluid (CSF) leakage and complications such as meningitis, brain herniation, and tension pneumocephalus. The reconstruction can be performed using different materials, both autologous (autologous grafts) and non-autologous, individually or combined in a multilayer fashion. The harvesting a nasoseptal flap is one of the most effective techniques: it reinforces the skull base closure granting isolation of the surgical field. The current study was focused on the development of new advanced devices and techniques, aiding in reducing postoperative CSF leak, which is one of the most feared complication of this surgical procedure. Additive manufacturing allows to design devices with tailored structural and functional features, in order to satisfy all the requirements. On the other hand, the development of injectable semi-IPNs and composites clearly benefits from specific mechanical/rheological and injectability studies. Accordingly, starting from some basic concepts, innovative principles and strategies were also proposed towards the design of additively manufactured and injectable devices.

Keywords: additive manufacturing | CSF leakage | design of injectable systems | endoscopic endonasal surgery | reverse engineering | skull base reconstruction

Abstract: 3D Printing and Additive Manufacturing technologies represent powerful tools for the direct fabrication of lightweight structures with improved and tunable properties. In current research, Fused Deposition Modeling (FDM)/3D fiber deposition technique was considered to design 3D multifunctional scaffolds with complex morphology, tailored biological, mechanical and mass transport properties. Polymeric and nanocomposite materials were used for scaffold design and optimization, with a particular focus on bone tissue engineering. As an example, poly(ϵ-caprolactone) (PCL), and PCL-based nanocomposite scaffolds were fabricated and analyzed. The effects of structural and morphological features (i.e., sequence of stacking, fiber spacing, pore size and geometry) as well as of nanoparticle inclusion on the mechanical performances were reported. Furthermore, the possibility to design 3D customized scaffolds for mandibular defect regeneration (i.e., symphysis and ramus) was also considered.

Keywords: Additive manufacturing | nanocomposites | reverse engineering | scaffold design

Abstract: Many women with early breast cancer undergo mastectomy as a consequence of an unfavorable tumor/breast ratio or because they prefer this option to breast conservation. As reported, breast reconstruction offers significant psychological advantages. Several techniques are currently available for the breast oncoplastic surgeon and offer interesting results in terms of aesthetic and patient-reported outcomes, using both breast implants and autologous tissues. On the other hand, advanced methodologies and technologies, such as reverse engineering and additive manufacturing, allow the development of customized porous scaffolds with tailored architectures, biological, mechanical and mass transport properties. Accordingly, the current research dealt with challenges, design methods and principles to develop 3D additively manufactured structures in breast reconstructive surgery.

Keywords: additive manufacturing | breast reconstructive surgery | design | fat grafting | reverse engineering | scaffold design