Nuno Alves

Innovative Developments in Design and Manufacturing: Advanced Research in Virtual and Rapid Prototyping -- Proceedings of VRP4, Oct. 2009, Leiria, Portugal

The use of rapid prototyping has increasingly begun to reveal itself as a tool of great value in supporting medical activity. From two-dimensional medical images from computed tomography (CT) or magnetic resonance imaging (MRI) it is possible to obtain three-dimensional models. The models produced by rapid prototyping technologies are useful both in educational and medical-surgical environments. It can simplify the diagnosis of certain diseases, the development of complex surgical procedures, the prostheses and medical devices manufacture and the visualization of anatomical structures in educational environment produce models and prototype parts (Alves & Braga 2001). One of the main applications of Rapid Prototyping is the fast way that is allowed in verifying new concept projects in the earlier stages or even in advanced phases of conception. In all Rapid Prototyping processes, a 3D CAD model is used that is translated into an STL (Stereolithography) format file, (Souza et al. 2003) where all the model surfaces are converted in a triangle mesh. In Biomedical Engineering field, using Rapid Prototyping techniques it is possible to produce several types of anatomical models and implant replica with educational purposes or to better understand a specific patient pathology. The models, depending of available techniques, can be made of paper, wax, ceramic, plastic or metal (Antas & Lino 2008). These models can be produced without finishing or color or have these finishing operations done later to improve visualization. For educational purpose it is possible to manufacture implant replica with much lower cost than the implant value. A great interest can be found in anatomical models manufacture from patient tomographic images. These models allow students from biomedical field to have an easier view of a specific pathology and compare it with normal anatomical models. To better understand image techniques and anatomy, it is also possible to simultaneously compare the original image (TC or MRI) and 3D solid model. Medical professionals cooperate with other field professionals to optimize pre-surgical pathology analysis, shorten surgical times, create personalized tools, facilitate the communication with patients and, simultaneously, to explore the capabilities this technology offers in personalized prosthesis design (Antas & Lino 2008). Vertebral Spine replica are particularly useful to diagnose, plan and simulate surgical procedures as it also allows the patients to understand the nature of their pathologies as well the need for surgical procedures (Madrazo et al. 2008) Several manufacturing processes are available today, as Fused Deposition Modeling (FDM), Stereolithography (SLA), Selective Laser Sintering (SLS), Tridimensional Printing (TDP or 3DP) and Laminated Object Manufacturing (LOM) among other specific processes. A brief description of the most used Rapid Prototyping processes is presented as follows: • Fused Deposition Modeling (FDM): This prototyping process build the prototypes by depositing an extruded thermoplastic material. The injection head draw transversal section perimeters and fills them building, this way, each layer. The most used material is ABS once it has good mechanical properties. More recently have been developed equipments that allow the used of materials such as polycarbonate and polyphenilsulfone (PPSU) that have better mechanical and thermic properties than ABS. • Stereolitography (SLA): This system builds the prototype by polymerizing a photosensitive liquid resin by applying an ultraviolet light formed by a laser. The solidifying process is made layer by layer, allowing obtaining a good surface finished prototype. • Selective Laser Sintering (SLS): This process allows physical models building by using dust materials like ceramics or metal. These materials are processed in an inert and thermally controlled environment inside a chamber. In here, the melting point (sintering) is achieved by action of a CO2 laser. After one layer being sinterized, another layer is deposited until the prototype is finished. This method demands a post-processing work to obtain a better surface. • Three Dimensional Printing (TDP or 3DP): In this process, models are built from a dust material (which can be a blend using materials like composite, cellulose among others) infiltrated with a liquid binder. This binder is applied through a printing head as used in traditional printing. The prototype is removed having the dust blended with the binder and needing operations of cleaning and medium consolidation. • Laminated Object Manufacturing (LOM): In LOM, most of the times, the models are obtained by gluing successive layers of paper which are cut by a laser beam. All the paper not used in the model is cut in square or rectangle forms to make easier prototype remove. To ensure the needed rigidity a frame is also built. Model definition will result from paper thickness and quality. Sometimes, instead paper there can be, also, used glass fibres, ceramics or metal (Alves & Braga 2001).

Choosing sheep (Ovis aries) as animal model for temporomandibular joint research: Morphological, histological and biomechanical characterization of the joint disc.

Preclinical trials are essential to the development of scientific technologies. Remarkable molecular and cellular research has been done using small animal models. However, significant differences exist regarding the articular behavior between these models and humans. Thus, large animal models may be more appropriate to perform trials involving the temporomandibular joint (TMJ). The aim of this work was to make a morphological (anatomic dissection and white light 3D scanning system), histological (TMJ in bloc was removed for histologic analysis) and biomechanical characterization (tension and compression tests) of sheep TMJ comparing the obtained results with human data. Results showed that sheep processus condylaris and fossa mandibularis are anatomically similar to the same human structures. TMJ disc has an elliptical perimeter, thinner in the center than in periphery. Peripheral area acts as a ring structure supporting the central zone. The disc cells display both fibroblast and chondrocyte-like morphology. Marginal area is formed by loose connective tissue, with some chondrocyte-like cells and collagen fibers in diverse orientations. Discs obtained a tensile modulus of 3.97±0.73MPa and 9.39±1.67MPa, for anteroposterior and mediolateral assessment. The TMJ discs presented a compressive modulus (E) of 446.41±5.16MPa and their maximum stress value (σmax) was 18.87±1.33MPa. Obtained results suggest that these animals should be considered as a prime model for TMJ research and procedural training. Further investigations in the field of oromaxillofacial surgery involving TMJ should consider sheep as a good animal model due to its resemblance of the same joint in humans.

Automatic 3D shape recovery for rapid prototyping

The capacity to create, display and manipulate a three-dimensional (3D) computer model and produce a physical replica of an existing object, enabling 3D re-shaping activities, plays an important role in different areas such as engineering, biology, architecture and archaeology. Some improvements have been made in a biologically based computer-aided design system, called BioCAD, specifically designed for the rapid and accurate 3D shape recovery from existing large objects, creating 3D computer models either to produce sophisticated photo-realistic renderings, two-dimensional drawings, or to generate surface models for simulation purposes and rapid prototyping applications. This improved system comprises three main routines through which the major findings are as follows: i) the algorithm for “ciliary” calibration routine enables to converge all digital image sequence, so uncertainties decrease, resulting in higher accuracy; ii) through the binocular stereopsis routine, the 3D shape of the perceived large object can actually be inferred; iii) STL and SLI routine allows to integrate BioCAD system and other advanced computer-aided technologies, enabling one to obtain a very small layer thickness from a straightforward slicing process of STL files with a large dimension, minimising the slicing processing time by exploring the advantage of the Matlab language, in terms of matrix manipulation and RAM memory of personal computers.

Fabrication of Poly(ε-caprolactone) Scaffolds Reinforced with Cellulose Nanofibers, with and without the Addition of Hydroxyapatite Nanoparticles.

Biomaterial properties and controlled architecture of scaffolds are essential features to provide an adequate biological and mechanical support for tissue regeneration, mimicking the ingrowth tissues. In this study, a bioextrusion system was used to produce 3D biodegradable scaffolds with controlled architecture, comprising three types of constructs: (i) poly(ε-caprolactone) (PCL) matrix as reference; (ii) PCL-based matrix reinforced with cellulose nanofibers (CNF); and (iii) PCL-based matrix reinforced with CNF and hydroxyapatite nanoparticles (HANP). The effect of the addition and/or combination of CNF and HANP into the polymeric matrix of PCL was investigated, with the effects of the biomaterial composition on the constructs (morphological, thermal, and mechanical performances) being analysed. Scaffolds were produced using a single lay-down pattern of 0/90°, with the same processing parameters among all constructs being assured. The performed morphological analyses showed a satisfactory distribution of CNF within the polymer matrix and high reliability was obtained among the produced scaffolds. Significant effects on surface wettability and thermal properties were observed, among scaffolds. Regarding the mechanical properties, higher scaffold stiffness in the reinforced scaffolds was obtained. Results from the cytotoxicity assay suggest that all the composite scaffolds presented good biocompatibility. The results of this first study on cellulose and hydroxyapatite reinforced constructs with controlled architecture clearly demonstrate the potential of these 3D composite constructs for cell cultivation with enhanced mechanical properties.

Four-Dimensional Bioprinting As a New Era for Tissue Engineering and Regenerative Medicine

In the era of “big data,” coping with a society that is in constant development, the discovery of “new” scientific and technological knowledge must (i) progress at an incredibly fast pace, (ii) target a wide audience, and (iii) have a practical impact in the society by addressing relevant challenges. The health sciences are naturally a priority area of research, mostly because of the impact they have on augmenting human life expectancy and improving well-being, by developing advanced tailored approaches to address patient-specific needs. As an example, during the past decade, the wide amount of data gathered from the human genome project, along with the improved knowledge of genome regulatory mechanisms, brought about the development of synthetic biology and genomic editing techniques (Singh et al., 2017). This massive advancement has been contributing not only to a better definition of disease mechanisms, but, importantly, also to the development of personalized therapeutic approaches. Indeed, the so-called “precision medicine” represents one of the main themes addressed by the European Commission health program, being featured in several distinct topics in the Horizon 2020 research and innovation program.1 In this context of incessant development of tools and improvements in the biomedical field, tissue engineering is playing a leading role as a multidisciplinary research branch. The ambition to cope with the complexity of human tissues, aimed at regenerating those hampered by diseases and age-related degeneration, has been the major goal of tissue engineering, which emerged in the 1980s, as a frontier scientific field with an enormous potential. An overwhelming amount of tissue engineering strategies have been developed since then, aimed at regenerating bone, cartilage, skin, and many other tissues and organs, in the attempt to bridge structure (gross anatomy and histological architecture) with the corresponding function (physiology and cell biology), as a paramount challenge to be solved (Campana et al., 2014). On this regard, several efforts have been made worldwide to develop synthetic or semisynthetic constructs that could mimic native tissues. Most of the human native tissues are made of complex three-dimensional (3D) structures, presenting different shapes, architectures, specific cell types, and extracellular matrix compositions. Furthermore, these tissues are extremely plastic and not static, having unique functions suitable to dynamic changes in tissue conformations. Thus, the conventional approaches of creating static 3D structures are not sufficient for its usage in biomedicine and the achievement of 3D complex organ structures is far from being tangible (Woodfield et al., 2017). Implants for tissue engineering strongly depend on the (bio)materials and the manufacturing process. The conventional manufacturing processes do not present a properly control over pore size, geometry, and spatial distribution, not guaranteeing pore interconnectivity; which are key features for successful tissue regeneration (Hollister, 2005). Therefore, additive manufacturing (also known as 3D printing) techniques have gained an increased importance for the scientific community overlapping the referred drawbacks. The usage of computer-aided processes for patterning and assembling

Computer modelling and simulation of a bioreactor for tissue engineering

A conventional approach to tissue engineering involves the implantation of porous, biodegradable and biocompatible scaffolds seeded with cells into the defect site. In some strategies, tissue engineering requires the in vitro culture of tissue-engineering constructs for implantation later. In this case, bioreactors are used to grow 3D tissues under controlled and monitored conditions. However, the quality of the resulting 3D tissue is highly dependent on the design and dimensions of the bioreactor, as well on the operating conditions. In this work, a computational fluid dynamic software package was used to investigate the influence of cylindrical bioreactor dimensions (length and diameter) on the fluid flow and scaffold shear stress. Computer simulations were performed using three different rotational movements (horizontal, vertical and biaxial rotation) and appropriate boundary conditions. Results show that the effect of the bioreactor length on the scaffold shear stress is more important than the diameter, while high length is associated to low scaffold shear stress. On the other hand, the fluid flows within the bioreactor and scaffold shear stresses are dependent on the rotational movement, being more uniform in the biaxial rotation due to the combination of rotational movements.

Computer rapid design II: applications

A new reverse design approach based on the more appropriate algorithms and procedures from both photogrammetry and computer vision in combination with biologically based algorithms replicating the human vision process is presented. The integration of this novel approach with rapid prototyping is investigated through two historic buildings. The findings show that the geometric shape of an existing building can be easily captured and automatically reproduced in both virtual and physical ways.

Rapid manufacturing of medical prostheses

The fabrication of medical prostheses is a topical research area combining knowledge from distinct domains, like engineering, materials and medical fields. Recent computer assisted technologies have proved to play an important role in the medical field. In this research work, the generation of a prosthetic glove to cover a damaged hand of a patient is produced using reverse engineering, rapid prototyping and rapid tooling techniques. The geometric data obtained from reverse engineering through both computer tomography and laser scanning are used and manipulated to create accurate representations of these devices. The reverse engineering data are then used to produce STL models that are physically reproduced through rapid prototyping and tooling processes. An accurate prosthetic glove is obtained using non-toxic materials proving that the exploitation of these technologies can represent key tools to improve the quality of life.

Effects of bilateral discectomy and bilateral discopexy on black Merino sheep rumination kinematics: TEMPOJIMS – phase 1 – pilot blinded, randomized preclinical study

BACKGROUND The temporomandibular joint interposal study (TEMPOJIMS) is a rigorous preclinical trial divided in 2 phases. In phase 1 the authors investigated the role of the TMJ disc and in phase 2 the authors evaluated 3 different interposal materials. The present work of TEMPOJIMS - phase 1, investigated the effects of bilateral discectomy and discopexy in sheep mastication and rumination. METHODS This randomized, blinded and controlled preclinical trial (in line with the ARRIVE guidelines) was conducted in 9 Black Merino sheep to evaluate changes in mastication and rumination after bilateral discectomy and bilateral discopexy, by comparing with a sham surgery control group. The outcomes evaluated were: (1) absolute masticatory time; (2) ruminant time per cycle; (3) ruminant kinematics, and (4) ruminant area. After baseline evaluation and surgical interventions, the outcomes were recorded over 3 successive days, every 30 days, for 6 months. RESULTS The first month after intervention seemed to be the critical period for significant kinematic changes in the discectomy and discopexy groups. However, 6 months after the bilateral interventions, no significant changes were noticed when compared with the control group. CONCLUSIONS In this study, bilateral discectomy and discopexy had no significant effect in mastication and ruminatory movement. The introduction of kinematic evaluation presents a new challenge that may contribute to the improvement of future studies on the TMJ domain.

Bio Inspired Algorithms for Injection Moulding Optimization

Social behaviors of living organisms found in nature, like food searching, environment fitness and survival are inspiration for meta-heuristic mathematical models. Replicating these natural organism behaviors, several optimization algorithms have been developed and applied to technological processes. In this work, some nature inspired algorithms are applied to the injection problem in order to optimize the injection runners’ geometry, so that the overall cycle time is minimized. A key issue is the injection moulding process, as it strongly determines the cost per part. A global optimization strategy was implemented for the injection moulding cycle time, covering the main steps of process, filling time, cooling time, packing time and opening time. To achieve the optimum solution for each design variable and obtain the best time solution overall, it will enable to evaluate optimality, robustness, convergence, and variables dispersion for each used algorithm.