Dynamic Facial Prosthetics for Sufferers of Facial Paralysis

BackgroundThis paper discusses the various methods and the materialsfor the fabrication of active artificial facial muscles. Theprimary use for these will be the reanimation of paralysedor atrophied muscles in sufferers of non-recoverableunilateral facial paralysis.MethodThe prosthetic solution described in this paper is based onsensing muscle motion of the contralateral healthy musclesand replicating that motion across a patient’s paralysed sideof the face, via solid state and thin film actuators. Thedevelopment of this facial prosthetic device focused onrecreating a varying intensity smile, with emphasis ontiming, displacement and the appearance of the wrinklesand folds that commonly appear around the nose and eyesduring the expression.An animatronic face was constructed with actuations beingmade to a silicone representation musculature, usingmultiple shape-memory alloy cascades. Alongside theartificial muscle physical prototype, a facial expressionrecognition software system was constructed. This formsthe basis of an automated calibration and reconfigurationsystem for the artificial muscles following implantation, soas to suit the implantee’s unique physiognomy.ResultsAn animatronic model face with silicone musculature wasdesigned and built to evaluate the performance of ShapeMemory Alloy artificial muscles, their power controlcircuitry and software control systems. A dual facial motionsensing system was designed to allow real time control overmodel – a piezoresistive flex sensor to measure physicalmotion, and a computer vision system to evaluate real toartificial muscle performance.Analysis of various facial expressions in real subjects wasmade, which give useful data upon which to base thesystems parameter limits.ConclusionThe system performed well, and the various strengths andshortcomings of the materials and methods are reviewedand considered for the next research phase, when newpolymer based artificial muscles are constructed andevaluated.Key WordsArtificial Muscles, facial prosthetics, stroke rehabilitation,facial paralysis, computer vision, automated facialrecognition

3D Printed Architectured Silicones with Autonomic Self-healing and Creep-resistant Behavior

Self-healing silicones that are able to restore the functionalities and extend the lifetime of soft devices hold great potential in many applications. However, currently available silicones need to be triggered to self-heal or suffer from creep-induced irreversible deformation during use. Here, we design and print silicone objects that are programmed at the molecular and architecture levels to achieve self-healing at room temperature while simultaneously resisting creep. At the molecular scale, dioxaborolanes moieties are incorporated into silicones to synthesize self-healing vitrimers, whereas conventional covalent bonds are exploited to make creep-resistant elastomers. When combined into architectured printed parts at a coarser length scale, layered materials exhibit fast healing at room temperature without compromising the elastic recovery obtained from covalent polymer networks. A patient-specific vascular phantom is printed to demonstrate the potential of architectured silicones in creating damage-resilient functional devices using molecularly designed elastomer materials

In silico design of additively manufacturable composite synthetic vascular conduits and grafts with tuneable compliance

Benchtop testing of endovascular medical devices under accurately simulated physiological conditions is a critical part of device evaluation prior to clinical assessment. Currently, glass, acrylic and silicone vascular models are predominantly used as anatomical simulator test beds for in vitro testing. However, most current models lack the ability to mimic the non-linear radial compliance of native vessels and are typically limited to being compliance-matched at a single mean pressure comparison point or not at all. Hence, a degree of caution needs to be shown when analysing results from such models under simulated physiological or pathophysiological conditions. Similarly, the clinical translation of proposed biomimetic compliance-matched vascular grafts has undoubtedly been curtailed due to performance and material limitations. Here, we propose a new design for synthetic vessels where compliance can be precisely modulated across a wide physiological pressure range by customising design parameters. Building on previously demonstrated methods of 3D printing composite compliant cylindrical structures, we demonstrate proof of principle in creating composite vascular constructs designed via a finite element model. Our constructs are 3D printable and consist of a soft silicone matrix with embedded polyurethane fibres. The fibre layer consists of circumferential sinusoidal waves with an amplitude that can be altered to result in tuneable internal radial compliances of 5.2-15.9%/mmHg × 10-2 at a mean pressure of 100 mmHg. Importantly, the design presented here allows preservation of the non-linear exponentially decaying compliance curve of native arteries and veins with an increasing mean pressure. This model offers a design toolbox for 3D printable vascular models that offer biomimetic compliance. The robust nature of this model will lead to rapidly accelerating the design process for biomimetic vascular anatomical simulators, lumped parameter model flow loops, endovascular device benchtop testbeds, and compliance-matched synthetic grafts.Science Foundation IrelandFulbright Ireland Student Award12 month embargo - A

3D printing of bacteria into functional complex materials

Despite recent advances to control the spatial composition and dynamic functionalities of bacteria embedded in materials, bacterial localization into complex three-dimensional (3D) geometries remains a major challenge. We demonstrate a 3D printing approach to create bacteria-derived functional materials by combining the natural diverse metabolism of bacteria with the shape design freedom of additive manufacturing. To achieve this, we embedded bacteria in a biocompatible and functionalized 3D printing ink and printed two types of “living materials” capable of degrading pollutants and of producing medically relevant bacterial cellulose. With this versatile bacteria-printing platform, complex materials displaying spatially specific compositions, geometry, and properties not accessed by standard technologies can be assembled from bottom up for new biotechnological and biomedical applications.ISSN:2375-254

Fused filament fabrication of polycaprolactone bioscaffolds: Influence of fabrication parameters and thermal environment on geometric fidelity and mechanical properties

Polycaprolactone (PCL) is frequently used in the fabrication of porous scaffold architectures for tissue engineering applications. PCL's biocompatibility, bio-resorption profile and thermoplasticity make it an exceptionally versatile polymer for the fabrication of 3D printed lattice bioscaffold architectures. However, despite its ubiquitous use, optimal parameters for printing PCL lattice bioscaffolds have not been fully elucidated. In this study, fused filament fabrication (FFF) and a custom temperature-regulated enclosure were used to fabricate cubic PCL lattice porous solids. It was hypothesised that the cooling rate of the extruded scaffold material plays a key role in ensuring geometrical fidelity. Samples were fabricated at 3 different layer heights 0.12, 0.13 and 0.14 mm within two temperature regulated envelopes at 17.5 ± 1.5 °C for sample group ET17.5 °C and 27.5 ± 1.5 °C for sample group ET27.5 °C. Scaffold architectures fabricated within the 17.5 ± 1.5 °C envelope at the respective layer heights presented consistently less geometric deviation from the original CAD model than those scaffolds fabricated within a 27.5 ± 1.5 °C envelope. Echoed in the mechanical performance evaluation, the ET17.5 °C group performed with greater consistency and less deviation in Young's modulus and ultimate compressive strength. Samples from ET17.5 °C were also found to possess lower levels of crystallinity compared to ET27.5 °C which correlates with the extended cooling cycle within a 27.5 ± 1.5 °C envelope. Optical profilometry also revealed less undulation in the surface topography of polymer struts from ET17.5 °C when compared to ET27.5 °C. These results could assist tissue engineers in further optimising FFF of PCL bioscaffolds by reducing geometric variability between the design and fabrication of bioscaffold architectures; reducing the potential for inconsistent mechanical performance and improving yield rates as this technology transitions from prototyping to mass manufacturing environments

Flax-based natural composites hierarchically reinforced by cast or printed carbon fibres

Plant-derived natural fibres hold great potential as renewable and sustainable reinforcing elements in structural composites. However, a broader use of natural fibre composites requires further improvements in their mechanical properties, to reach performance comparable to carbon fibre-reinforced polymers. In this study, we exploit discontinuous carbon fibres in rheologically modified inks to controllably reinforce flax-based laminates in specific directions. The carbon fibres are incorporated by tape casting or 3D printing approaches directly on the pre-aligned flax structures. With the help of quasi-static flexural tests and dynamic mechanical analysis, we show that the elastic modulus, the strength, and the damping behaviour of the flax-based composites can be significantly enhanced by controlling the relative orientation of the hierarchically structured carbon and flax fibres. The flexural stiffness of composites reinforced with carbon fibres oriented along and perpendicular to the flax fibres increases, respectively, 62% and 146% relative to the carbon-free reference. This is accompanied by a 1.6-fold increase in loss modulus, which is a performance indicator for damping. The experimentally observed stiffening of the flax-based structures can be described using simple beam theory. By combining reinforcing elements of different length scales with readily available manufacturing techniques, this work shows the potential of hierarchical structuring in improving the mechanical performance of flax-based composites.ISSN:0266-3538ISSN:1879-105

Study Of The Flutter Kinematics And Blood Flow Motion For Bioprosthetic Aortic Valves With Different Designs

OBJECTIVE: Improving bioprosthetic aortic valve (BAV) design is of paramount importance considering the increased number of aortic valve replacement procedures over the past decades. The design of such valves still needs further investigation to improve haemodynamic performance and to reduce detrimental flutter motion of leaflets that can lead to calcification and structural valve degeneration in time. For this reason, the effect of relevant shape parameters on leaflet kinematics and on flow features downstream of the valve is characterised in this study. METHODS: The approach considered to tackle the fluid-structure interaction (FSI) problem encompassing the simulation of the flow around a BAV and its leaflet kinematics is based on (i) a finite-element solver for the elastodynamics equation governing the valve mechanics, (ii) a high-order finite-difference solver for the incompressible Navier-Stokes equations governing the blood flow, (iii) a variational transfer for the strong coupling between fluid and structure. RESULTS: An emphasis has been put on the interplay of leaflet dynamics (more specifically, the observed flutter motion) and flow disturbances. In fact, the phenomenon of fluttering describes a relatively rapid oscillation of the leaflet mainly during peak systole. Depending on the designed leaflet shape, the simulated cases displayed very different motion, also named flutter modes, entailing the presence of different vortical patterns in the flow, levels of viscous shear stress close to the leaflets and von Mises stresses in the leaflets. The flutter modes characterised from the simulations have also been noted during in vitro experiments using high-speed cameras. CONCLUSIONS: This work brings new insights on the optimisation of the design of BAV leaflets from advanced numerical simulations of fluid-structure interaction problems. We anticipate that the developed approach and the findings may help to improve the design of BAV

3D printing of robotic soft actuators with programmable bioinspired architectures

Soft actuation allows robots to interact safely with humans, other machines, and their surroundings. Full exploitation of the potential of soft actuators has, however, been hindered by the lack of simple manufacturing routes to generate multimaterial parts with intricate shapes and architectures. Here, we report a 3D printing platform for the seamless digital fabrication of pneumatic silicone actuators exhibiting programmable bioinspired architectures and motions. The actuators comprise an elastomeric body whose surface is decorated with reinforcing stripes at a well-defined lead angle. Similar to the fibrous architectures found in muscular hydrostats, the lead angle can be altered to achieve elongation, contraction, or twisting motions. Using a quantitative model based on lamination theory, we establish design principles for the digital fabrication of silicone-based soft actuators whose functional response is programmed within the material's properties and architecture. Exploring such programmability enables 3D printing of a broad range of soft morphing structures.ISSN:2041-172

Fused Filament Fabrication of Bioresorbable Stent on a Rotating Mandrel

Bioresorbable stents have the potential to restore patency to blood vessels while minimising the risk of long-term complications. Bioresorbable stents can dissolve after restoring flow to a blocked artery, leaving behind a blood vessel with restored vascular tone. This can provide increased lumen gain, long-term vascular rehabilitation, and long-term healing. Additive manufacturing (AM) could offer new design freedom and patient-specific solutions; however, AM fabrication of bioresorbable stents, especially for specific patients, is challenging. In recent times, AM-based Fused Filament Fabrication (FFF) has gained popularity for printing stents by employing a rotating mandrel as a printing bed. However, using standard slicing methodology is challenging when generating extrusion profiles with strut dimensions at this size scale. By eliminating the requirement for a CAD model and instead slicing based on direct extrusion path generation from parametric curves, a method has been proposed for the FFF printing of bioresorbable stents on rotating mandrels. A Grasshopper (plugin in Rhinoceros) -based visual programming method was adopted for the generation of the required shapes of curves for the stent. The extrusion profile (gCode) was generated by Grasshopper for 3D printing on an FFF multi-axis machine. Poly (l-lactic) acid (PLLA) polymer material was chosen along with a standard zigzag stent shape for testing the proposed methodology. The extrusion temperature, nozzle speed, and extrusion values were varied as per the design of the experiment (Taguchi L9) approach to study their effect on the stent strut width and flexural strength. The optimisation was carried out to obtain a feasible relationship between parameters to print minimum strut width and maximum flexural strength. The proposed methodology successfully demonstrates printing complex stent shapes without a CAD model and slicing. (C) 2022 The Authors. Published by Elsevier B.V.ISSN:2212-827

Additive Manufacture of Composite Soft Pneumatic Actuators

This article presents a direct additive manufacturing method for composite material soft pneumatic actuators that are capable of performing a range of programmable motions. Commonly, molding is the method used to manufacture soft fluidic actuators. This is material, labor, and time intensive and lacks the design freedom to produce custom actuators efficiently. This article proposes an alternative semiautomated method of designing and manufacturing composite soft actuators. An affordable, open-source, desktop three-dimensional (3D) printer was modified into a four-axis, combined, fused deposition modeling, and paste extrusion printer. A Grasshopper 3D algorithm was devised to implement custom actuator designs according to user inputs, resulting in a G-code print file. Bending, contracting, and twisting motion actuators were parametrically designed and subsequently additively manufactured from silicone and thermoplastic elastomer (TPE) materials. Experimental testing was completed on these actuators along with their constitutive materials. Finite element models were created to simulate the actuator's kinematic performance. Having a platform method to digitally configure and directly additively manufacture custom-motion, composite soft actuators has the potential to accelerate the development of more intricate designs and lead to potential impacts in a range of areas, including in-clinic personalization of soft assistive devices and patient-specific biomedical devices.European Commission - European Regional Development FundScience Foundation Irelan