Body Part Surrogates for Medicine, Comfort and Safety Applications

Body part surrogates made with support from additive manufacturing (AM) technologies belong to a rapidly developing area of modeling. Although computer-based and mathematical modeling of complex processes is already an established field, these are not free from inherited problems. Surrogate modeling (physical modeling) being a subject of its own successfully complement mathematical and computer modeling and helps to cross-validate these methods and improve particular models. Present chapter provides a discussion on the general aspects of modeling relevant to the design, manufacturing and application of body part surrogates It also introduces new term ‘surrogate twins’ using the analogy of ‘virtual twins’. It also outlines a number of known applications of body part surrogates manufactured with support of AM in medicine, safety and comfort research. Strong and weak points of particular surrogate models is discussed basing on the general concepts of modeling including defining of particular surrogate model purposes, approximations, the ways of model validation, input parameter harvesting, related measurement systems and data processing, and setups for material and product testing. Comprehensive references will allow readers getting detailed information regarding discussed issues

Angular rate effect on stiffness and damping characteristics of different head/neck assemblies during cyclic tests

Introduction: Head and neck injuries are a serious threat in everyday and sport activities. Thus, a proper testing of protective gear is crucial to guarantee their effectiveness and to support companies towards their development. To achieve this goal, surrogates adopted in testing must be improved: researchers are developing their own prototypes as alternatives to the Hybrid III neck [1]. To further improve the bio fidelity of neck surrogates, a set of new prototypes aiming to obtain a neck stiffness closer to cadaver literature data [2] is under development. The novel method here presented was developed to characterize the cyclic/impact response of head/neck assemblies. This approach is useful since available stiffness data are typically obtained with static or quasistatic data [1] but the response of these surrogates may not be linear with flexion/extension angular rate. Methods: Two neck surrogates, a 50th male percentile Hybrid III (JASTI, Japan) and a novel biofidelic neck surrogate named BNP1 were assembled to a 50th male percentile Hybrid III head form (JASTI, Japan). The head/neck assembly was mounted over a K6D68 six-axis load cell (ME-Systeme, Germany) which was secured to a horizontal sliding platform. The platform was actuated using a 200 mm stroke MTS 242 servo hydraulic cylinder (MTS, USA) and sine waves of different amplitudes to increase the flexion/extension angular rate (Figure 1a). Loads at the neck base were acquired with the six-axis load cell synchronously to the displacement imposed by the cylinder. Motion of the head/neck assembly was acquired using a Bonita 3D Motion Capture System (Vicon, USA). Static stiffness of the two neck surrogates was also measured using an experimental setup like the one adopted by Nightingale [2]. Kinematics of the neck were reconstructed from marker data of two reference systems: lower neck base and head. From the bending moment vs flexion/extension angle cross plot as in Figure 1.b, two parameters were calculated: the sagittal neck stiffness (KS) as the slope of the linear regression of data, and the dissipated energy (E*d) as the area of the hysteresis cycle normalised to the flexion/extension range in radians. Results: Hysteresis cycles of the two necks at different angular speeds are reported in Figure 1b. The stiffnesses and the normalized energy values are reported in Table 1. IDiscussion: The Hybrid III presents a higher stiffness in flexion than in extension as expected [1], due to the cuts on the frontal portion of rubber disks; BNP1 shows an unbiased behaviour in the sagittal plane. At increasing angular rate, stiffness decreases and normalized energy increases; static stiffness differs from the cyclic values, possibly due to the different setups. Hybrid III, BNP1 and cadaver stiffness data differ from each other of about an order of magnitude, showing a trend towards better bio fidelity of BNP1. Square/ramp movements of the platform are also possible to simulate a step flexion/extension movement as well as side bending. This method could be adapted to study the effect of neck protectors on head/neck overloads. 1. Walsh E., Kendall M., Post A., Meehan A., Hoshizaki T. B. (2018). Comparative analysis of Hybrid III neckform and an unbiased neckform. Sports Engineering volume 21, pages 479–485. 2. Nightingale R.W., Winkelstein B.A., Knaub K. E., Richardson W.J.L., Jason F., Myers B.S. (2002). Comparative strengths and structural properties of the upper and lower cervical spine in flexion and extension. Journal of Biomechanics 35, 725–732

Prospects of paramagnetic lanthanide complexes for magnetic resonance imaging, local thermosensing and diagnosing

The features of the paramagnetic properties of lanthanide (Ln) containing complexes with crown ethers, pivaloyltrifluoracetonato, and EDTA have been studied by 1H and 19F NMR techniques. These complexes are of interest due to the prospect of using some of them as sensors for biology and medicine. The temperature dependencies of the lanthanide-induced shifts revealed that Ln complexes might have practical importance for 1H and 19F NMR temperature control in solutions. It was shown in vitro (using NMR spectrometers and MRI scanners) that these complexes can serve as special NMR thermo-sensitive contrast reagents

Influence of beam current on microstructure of electron beam melted Ti-6Al-4V alloy

The defect microstructure of the samples manufactured from Ti-6Al-4V powder was studied using electron beam melting (EBM) in the beam current range of 17 - 13 mA. The hybrid digital complex combined positron lifetime spectroscopy and coincidence Doppler broadening spectroscopy was used to characterize the defect structure of the materials. The microstructure and defects were also analyzed by transmission electron microscopy. It has been established that the main type of the defects in the EBM manufactured samples is dislocations. According to the conducted measurements and calculations, the dislocation density in the EBM manufactured samples exceeds by two orders the similar value for the cast Ti-6Al-4Valloy. Formation of Ti-Ti-Al nanoscale clusters has been found in the EBM manufactured samples

Parahydrogen-induced polarization of amino acids

Nuclear magnetic resonance (NMR) has become a universal method for biochemical and biomedical studies, including metabolomics, proteomics and magnetic resonance imaging (MRI). By increasing the signal of selected molecules, the hyperpolarization of nuclear spins has expanded the reach of NMR and MRI even further (e.g. hyperpolarized solid-state NMR and metabolic imaging in vivo). Parahydrogen (pH2) offers a fast and cost-efficient way to achieve hyperpolarization, and the last decade has seen extensive advances including the synthesis of new tracers, catalysts, and transfer methods. The portfolio of hyperpolarized molecules now includes amino acids, which are of great interest for many applications. Here, we review the current literature and developments for the hyperpolarization of amino acids and peptides

Powder-bed additive manufacturing for aerospace application: Techniques, metallic and metal/ceramic composite materials and trends

The current paper is devoted to classification of powder-bed additive manufacturing (PB-AM) techniques and description of specific features, advantages and limitation of different PB-AM techniques in aerospace applications. The common principle of “powder-bed” means that the used feedstock material is a powder, which forms “bed-like” platform of homogeneous layer that is fused according to cross-section of the manufactured object. After that, a new powder layer is distributed with the same thickness and the “printing” process continues. This approach is used in selective laser sintering/melting process, electron beam melting, and binder jetting printing. Additionally, relevant issues related to powder raw materials (metals, ceramics, multi-material composites, etc.) and their impact on the properties of as-manufactured components are discussed. Special attention is paid to discussion on additive manufacturing (AM) of aerospace critical parts made of Titanium alloys, Nickel-based superalloys, metal matrix composites (MMCs), ceramic matrix composites (CMCs) and high entropy alloys. Additional discussion is related to the quality control of the PB-AM materials, and to the prospects of new approaches in material development for PB-AM aiming at aerospace applications

Comparison of machining performance of stainless steel 316L produced by selective laser melting and electron beam melting

Powder bed fusion based additively manufactured SS 316L components fall short of surface integrity requirements needed for optimal functional performance. Hence, machining is required to achieve dimensional accuracy and to enhance surface integrity charcteristics. This research is focused on comparing the material removal performance of 316L produced by PBF-LB (laser) and PBF-EB (electron beam) in terms of tool wear and surface integrity. The results showed comparable surface topography and residual stress profiles. While the hardness profiles revealed work hardening at the surface where PBF-LB specimens being more susceptible to work hardening. The investigation also revealed differences in the grogress of the tool wear when machining specimens with either PBF-LB or PBF-EB

Parahydrogen‐Induced Polarization of Amino Acids

Nuclear magnetic resonance (NMR) has become a universal method for biochemical and biomedical studies, including metabolomics, proteomics, and magnetic resonance imaging (MRI). By increasing the signal of selected molecules, the hyperpolarization of nuclear spin has expanded the reach of NMR and MRI even further (e.g. hyperpolarized solid-state NMR and metabolic imaging in vivo). Parahydrogen (pH₂) offers a fast and cost-efficient way to achieve hyperpolarization, and the last decade has seen extensive advances, including the synthesis of new tracers, catalysts, and transfer methods. The portfolio of hyperpolarized molecules now includes amino acids, which are of great interest for many applications. Here, we provide an overview of the current literature and developments in the hyperpolarization of amino acids and peptides

Pectin coatings on titanium alloy scaffolds produced by additive manufacturing:Promotion of human bone marrow stromal cell proliferation

Ti6Al4V is a popular biomaterial for load-bearing implants for bone contact, which can be fabricated by additive manufacturing technologies. Their long-term success depends on their stable anchoring in surrounding bone, which in turn depends on formation of new bone tissue on the implant surface, for which adhesion and proliferation of bone-forming cells is a pre-requisite. Hence, surface coatings which promote cell adhesion and proliferation are desirable. Here, Ti6Al4V discs prepared by additive manufacturing (EBM) were coated with layers of pectins, calcium-binding polysaccharides derived from citrus (C) and apple (A), which also contained alkaline phosphatase (ALP), the enzyme responsible for mineralization of bone tissue. Adhesion and proliferation of human bone marrow stromal cells (hBMSC) were assessed. Proliferation after 7 days was increased by A-ALP coatings and, in particular, by C-ALP coatings. Cell morphology was similar on coated and uncoated samples. In conclusion, ALP-loaded pectin coatings promote hBMSC adhesion and proliferation