Fully integrated fused quartz acoustic horns for structural health monitoring.

Non-destructive acoustic structural sensing is an imperative technology, applicable to many different fields such as aerospace and civil engineering. To maintain a high sensitivity or to mitigate acoustic loss, it is important to increase the signal-to-noise ratio by improving coupling efficiency from acoustic sources to the object under test, such as an acoustic waveguide. Here, a fully integrated fused quartz horn design is combined with a fused quartz acoustic waveguide. The resulting system is intended to demonstrate a high accuracy low cost alternative to current sensing systems and the present article report on the viability of using a merged acoustic horn and waveguide.

Development of biomimetic in vitro fatigue assessment for UHMWPE implant materials.

An important research goal in the field of biomaterials lies in the progressive amendment of in vivo tests with suitable in vitro experiments. Such approaches are gaining more significance nowadays because of an increasing demand on life sciences and the ethical issues bound to the sacrifice of animals for the sake of scientific research. Another advantage of transferring the experiments to the in vitro field is the possibility of accurately control the boundary conditions and experimental parameters in order to reduce the need of validation tests involving animals. With the aim to reduce the amount of needed in vivo studies for this cause, a short-time in vitro test procedure using instrumented load increase tests with superimposed environmental loading has been developed at TUD to assess the mechanical long-term durability of ultra-high molecular weight polyethylene (UHMWPE) under fatigue loading in a biological environment.

A new mechanical indentation framework for functional assessment of articular cartilage.

The conventional mechanical properties of articular cartilage, such as compressive stiffness, have been shown to have limited capacity to distinguish visually normal from degraded cartilage samples. In this study, a new mechanical indentation framework for assessing functional properties of articular cartilage during loading/unloading, i.e. deformation and recovery, was established. The capacity of a ring-shaped indenter integrated with an ultrasound transducer to distinguish mechanically intact from proteoglycan-depleted tissue was investigated. To achieve this, normal and enzymatically degraded bovine osteochondral samples were subjected to loading/unloading while the response of the tissue at the middle was captured by ultrasound at the same time. The enzymatic degradation model was characterized by amount of proteoglycan content, glycosaminoglycan release and proteomic analysis. The mechanical response of a wider continuum of articular cartilage in the loaded area and its surrounding region was captured in this framework leading to investigate two parameters, L and TS, related to the surrounding tissue of the loaded area for functional assessment of cartilage. L is the distance between the ultrasound transducer and articular cartilage surface and TS is the transient strain of articular cartilage during loading and unloading. Classification Analysis based on Principal Component Analysis was used to investigate the capacity of the new parameters to assess the functionality of the tissue. Multivariate statistics based on Partial Least Squares regression was employed to identify the correlation between the response of the tissue in the indented area and its surrounding cartilage. The results of this study indicate that L during loading (deformation) can differentiate normal and mildly proteoglycan-depleted samples from severely depleted samples and L during unloading (recovery) can distinguish between normal and proteoglycan-depleted tissue. However, TS during deformation and recovery is unable to discriminate normal cartilage samples from proteoglycan-depleted tissue. The results also demonstrate a strong correlation between mechanical properties of the loaded area with the response of its surrounding cartilage during recovery. It is therefore concluded that L in this newly established framework can discriminate between normal and proteoglycan-depleted cartilage samples. However, more samples will be needed to verify the demarcation between samples degraded for varying amount of time.

IEC 61331-1: A new setup for testing lead free X-ray protective clothing.

PURPOSE: Lead free protective clothing can create a higher part of secondary radiation (SR) than products that are based on lead. Hence, the attenuation properties may be downgraded. The international measuring standard IEC 61331-1:2014 declares the "inverse broad beam geometry" (IBG) as standard method, which has recently been modified to IBG∗ by the Physikalisch Technische Bundesanstalt (PTB). Because of the unspecific partial irradiation of the ionization chamber problems in the evaluation of lead equivalence values (LEVs) can occur. An alternative method proposed in this paper overcomes these problems. MATERIALS AND METHODS: The alternative setup "modified broad beam geometry" (BBG∗) was tested and compared to the IBG∗ method by performing Monte Carlo simulations and radiation measurements including several lead-composite and lead-free protective materials. RESULTS: Simulations show a reduced collection efficiency of SR under IBG∗ whereas BBG∗ features a high degree of SR collection. Material samples with a high amount of SR can feature up to 8% higher LEVs compared to IBG∗. For most of the currently salable materials the differences of BBG∗ vs IBG∗ amount to <3% (0.25 mm LEV) and <1% (0.50 mm LEV). In special cases the currently practiced method can lead to heavier protective clothings. CONCLUSIONS: The proposed BBG∗ setup meets the specifications of the IEC standard with respect to energy response and SR collection. The method should be implemented in the IEC standard.

Design, optimisation and testing of a compact, inexpensive elastic element for series elastic actuators.

This paper presents the development of a compact torsion spring for use as an elastic element in a lightweight series elastic actuator for an active orthosis. This orthosis is going to be utilised as an assistive device for motorically impaired stroke-patients. In the design a two-step optimisation strategy was implemented to meet all requirements for the torsion spring. The first step was to identify a promising topology for the element. In the second step, the shape was optimised based on a finite element model using two different optimisation methods in order to minimise the von Mises equivalent stresses. Four promising variants of the identified topology were extracted from these calculations, one of which was then chosen as the final design. A prototype was manufactured by a laser cutting process, which is a new procedure in the context of elastic elements for series elastic actuators. The calculation results were validated successfully by measurement of the spring properties of this prototype.

Biodegradability and platelets adhesion assessment of magnesium-based alloys using a microfluidic system.

Magnesium (Mg)-based stents are extensively explored to alleviate atherosclerosis due to their biodegradability and relative hemocompatibility. To ensure the quality, safety and cost-efficacy of bioresorbable scaffolds and full utilization of the material tunability afforded by alloying, it is critical to access degradability and thrombosis potential of Mg-based alloys using improved in vitro models that mimic as closely as possible the in vivo microenvironment. In this study, we investigated biodegradation and initial thrombogenic behavior of Mg-based alloys at the interface between Mg alloys' surface and simulated physiological environment using a microfluidic system. The degradation properties of Mg-based alloys WE43, AZ31, ZWEK-L, and ZWEK-C were evaluated in complete culture medium and their thrombosis potentials in platelet rich plasma, respectively. The results show that 1) physiological shear stress increased the corrosion rate and decreased platelets adhesion rate as compared to static immersion; 2) secondary phases and impurities in material composition induced galvanic corrosion, resulting in higher corrosion resistance and platelet adhesion rate; 3) Mg-based alloys with higher corrosion rate showed higher platelets adhesion rate. We conclude that a microfluidic-based in vitro system allows evaluation of biodegradation behaviors and platelets responses of Mg-based alloys under specific shear stress, and degradability is related to platelets adhesion.

Biomechanical assessment of the aortic root using novel force transducers.

In recent years the use of valve sparing techniques has become more common in selected patients with aortic valve insufficiency. However, limited experimental research has been performed to document the biomechanical effect of these techniques. One experimental platform is to evaluate how the normal physiological aortic root forces are altered or re-established after the surgical intervention. Hence, the aim of this project was to develop new implantable force transducers for a biomechanical description of various aortic root repair techniques. Two novel force transducers were developed. Both transducers were manufactured using rapid prototyping and were instrumented with miniature strain gauges. Before implantation both transducers were calibrated using a dedicated setup, yielding very linear correlation between the applied load and transducer output. The developed force transducers were implanted and tested in an 80kg porcine model. In the post-cardioplegic heart, the peak annular forces varied in the range of 2-4N and the commissural forces varied from 0.4 to 0.8N with a left ventricular pressure of 111mmHg. In conclusion, the two new force transducers to measure forces in the aortic root have successfully been developed. With these new devices a novel versatile and direct force measurement system has been provided.

A novel blood incubation system for the in-vitro assessment of interactions between platelets and biomaterial surfaces under dynamic flow conditions: The Hemocoater.

Hemocompatibility evaluation of biomaterials necessitates the use of blood incubation systems which simulate physiological flow conditions. However, most of the current systems have various limitations, especially restricted material variability, poor access to the test surface or damage of blood cells due to the use of a pump. In this paper, we combined the advantages of existent setups and developed a new planar shaped incubation test bench to lift those restrictions and mimic the pulsatile in-vivo situation. The adjustable flow conditions at the tested material surface were defined and corresponded to those in blood vessels. Platelet/material-interaction, as major aspect of hemocompatibility, was investigated for four common polymeric materials (polyoxymethylene, polypropylene, polyethylene and silicone elastomer) with platelet deprivation and platelet adhesion tests. Highly significant differences in the adhesion of platelets onto the tested material surfaces were measured. The number of adhered platelets on the most hydrophobic sample (silicone elastomer) was four-times higher than on the most hydrophilic sample (polyoxymethylene). These findings were confirmed with a scanning microscopic analysis and demonstrated the suitability of the testing device for the evaluation of platelet/material interactions. Moreover, hemolysis measurements demonstrated that the system did not provoke blood damage. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2430-2440, 2016.

Assessment of wear facets produced by the ACTA wear machine.

OBJECTIVE: To investigate the use of a three-dimensional (3D) digital scanning method in determining the accuracy of the wear performance parameters of resin-based composites (RBCs) determined using a two-dimensional (2D) analogue methodology following in-vitro testing in an Academisch Centrum for Tandheelkunde Amsterdam (ACTA) wear machine. METHODS: Specimens compatible with the compartments of the ACTA wear machine specimen wheel (n=10) were prepared from one commercial and four experimental RBCs. The RBC specimens were rotated against an antagonist wheel in a food-like slurry for 220,000 wear cycles. The mean wear depth was measured using the traditionally employed 2D and compared with the 3D profilometric (digital) techniques. Data were submitted to analyses of variance, Tukey's post hoc tests and Independent Samples Student's t-tests (where appropriate) at p<0.05. RESULTS: The RBC rank achieved for mean wear depth calculations were similar whether the 2D or 3D techniques were employed. However, the mean wear depth values obtained from the 3D digital technique were significantly increased for two of the five RBC materials compared with the 2D methodology. The total volumetric wear data provided an assessment of the potential of the experimental RBC formulations for clinical usage. CONCLUSION: The 3D technique allowed for the assessment of mean maximum wear depth and mean total volumetric wear which enables tribological analyses of the wear facet and therefore the wear mechanisms operative. Employing the 2D profile technique ranks RBC materials in terms of in-vitro wear performance. CLINICAL SIGNIFICANCE: Confidence in the wear volume measurements can only be achieved if the wear facet is analysed with sufficient resolution using a 3D digital measurement technique. However, the employment of 2D profilers is useful when screening potential new RBC formulations for the restoration of posterior dentition.

Assessment of Carbon- and Metal-Based Nanoparticle DNA Damage with Microfluidic Electrophoretic Separation Technology.

In this study, we examined the feasibility of extracting DNA from whole cell lysates exposed to nanoparticles using two different methodologies for evaluation of fragmentation with microfluidic electrophoretic separation. Human lung macrophages were exposed to five different carbon- and metal-based nanoparticles at two different time points (2 h, 24 h) and two different doses (5 µg/ml, 100 µg/ml). The primary difference in the banding patterns after 2 h of nanoparticle exposure is more DNA fragmentation at the higher NP concentration when examining cells exposed to nanoparticles of the same composition. However, higher doses of carbon and silver nanoparticles at both short and long dosing periods can contribute to erroneous or incomplete data with this technique. Also comparing DNA isolation methodologies, we recommend the centrifugation extraction technique, which provides more consistent banding patterns in the control samples compared to the spooling technique. Here we demonstrate that multi-walled carbon nanotubes, 15 nm silver nanoparticles and the positive control cadmium oxide cause similar DNA fragmentation at the short time point of 2 h with the centrifugation extraction technique. Therefore, the results of these studies contribute to elucidating the relationship between nanoparticle physicochemical properties and DNA fragmentation results while providing the pros and cons of altering the DNA isolation methodology. Overall, this technique provides a high throughput way to analyze subcellular alterations in DNA profiles of cells exposed to nanomaterials to aid in understanding the consequences of exposure and mechanistic effects. Future studies in microfluidic electrophoretic separation technologies should be investigated to determine the utility of protein or other assays applicable to cellular systems exposed to nanoparticles.

Unconstrained testing of spine with bi-axial universal testing machine.

BACKGROUND: In-vitro biomechanical assessment of the spine reveals significant information on the mechanics of spinal disorders, treatment methods, and surgical implants. Specialized devices for the evaluation of spine biomechanics have thus become popular. However, these devices might not be affordable for all research groups. PURPOSE: The purpose of this study was to describe an apparatus to be attached to a standard bi-axial universal testing machine that would make unconstrained testing of the spine possible. STUDY DESIGN/SETTING: A technical note on the definition of a spinal testing fixture with validation. METHODS: Intact lumbosacral spines (T12-S1) were tested in sagittal and lateral bending and axial rotation. Three-dimensional interlevel rotations at each level (L1-4) were analyzed. RESULTS: By comparison with the literature, we found that the new fixture was able to successfully produce reasonable relative rotation values for the lumbar spine. CONCLUSIONS: We demonstrated that the low cost fixture allowed unconstrained (six degree of freedom, 6 DOF) testing of fresh-frozen cadaveric lumbar spine.

High pressure assessment of bilayered electrospun vascular grafts by means of an Electroforce Biodynamic System®.

INTRODUCTION: Tissue engineering offers the possibility of developing a biological substitute material in vitro with the inherent properties required in vivo. However, the inadequate performance in vascular replacement of small diameter vascular grafts (VG) reduces considerably the current alternatives in this field. In this study, a bilayered tubular VG was produced, where its mechanical response was tested at high pressure ranges and compared to a native femoral artery. MATERIALS AND METHOD: The VG was obtained using sequential electrospinning technique, by means of two blends of Poly(L-lactic acid) and segmented poly(ester urethane). Mechanical testing was performed in a biodynamic system and the pressure-strain relationship was used to determine the elastic modulus. RESULTS: Elastic modulus assessed value of femoral artery at a high pressure range (33.02×106 dyn/cm(2)) was founded to be 36% the magnitude of VG modulus (91.47×106 dyn/cm(2)) at the same interval. CONCLUSION: A new circulating mock in combination with scan laser micrometry have been employed for the mechanical evaluation of bioresorbable bilayered VGs. At same pressure levels, graft elasticity showed a purely "collagenic" behavior with respect to a femoral artery response.

A new approach to determine ligament strain using polydimethylsiloxane strain gauges: exemplary measurements of the anterolateral ligament.

A thorough understanding of ligament strains and behavior is necessary to create biomechanical models, comprehend trauma mechanisms, and surgically reconstruct those ligaments in a manner that restores a physiological performance. Measurement techniques and sensors are needed to conduct this data with high accuracy in an in vitro environment. In this work, we present a novel sensor device that is capable of continuously recording ligament strains with high resolution. The sensor principle of this biocompatible strain gauge may be used for in vitro measurements and can easily be applied to any ligament in the human body. The recently rediscovered anterolateral ligament (ALL) of the knee joint was chosen to display the capability of this novel sensor system. Three cadaver knees were tested to successfully demonstrate the concept of the sensor device and display first results regarding the elongation of the ALL during flexion/extension of the knee.

Avaliação in vitro da citotoxicidade do enxaguatório Periogard© em diferentes períodos de tempo / In vitro assessment of the cytotoxicity of Periogard© mouthwash at different periods

O estudo teve como objetivo avaliar a citotoxicidade do enxaguatório a base de clorexidina Periogard® em diferentes períodos de tempo, 0, 15, 30, 45, 60 e 120 segundos, quanto ao seu efeito citotóxico em fibroblastos gengivais L929. Utilizou-se 3 grupos controle: positivo (C+) detergente celular Tween 80, negativo (C-) PBS e controle de célula (CC), onde as mesmas não foram expostas a nenhum material. O ensaio de citotoxicidade foi realizado utilizando cultura celular de fibroblasto de camundongo (L929). Após contato do enxaguatório com as células, as mesmas foram colocadas em contato com o corante vital vermelho neutro utilizando-se a técnica “dye up take”. Os valores da quantidade de células viáveis foram submetidos à análise da variância (ANOVA) para determinar se havia diferença estatística entre os grupos e, posteriormente, ao teste de Tukey (p<0.05). Os resultados demonstraram citotoxicidade do enxaguatório Periogard® em todos os períodos avaliados. Foram encontradas diferenças estatísticas entre os grupos experimentais com todos os demais controles (p>0.05). Pode-se concluir com a realização deste trabalho que o Periogard® é citotóxico aos fibroblastos no período de 0 a 120 segundos.

This study aimed to evaluate the cytotoxicity of chlorhexidine-based mouthwash (Periogard©) in different periods, 0, 15, 30, 45, 60 and 120 seconds, for its cytotoxic effect on gingival fibroblasts L929. Three control groups were used: positive (C +) cell detergent Tween 80, negative (C -) PBS, and control of cell (CC) with cells that were not exposed to any material. The cytotoxicity test was performed using fibroblast cell culture of mouse (L929). After the the cells were in contact with the mouthwash, they were placed in contact with Neutral red using the dye up take technique. The values of the quantity of viable cells were submitted to analysis of variance (ANOVA) to determine whether there were statistical differences between groups, and then submitted toTukey test (p <0.05). The results demonstrated cytotoxicity of mouthwash Periogard© in all periods. Differences were observed between the experimental groups with all other controls (p> 0.05). It is possible to conclude that Periogard© is cytotoxic to fibroblasts in the periodsfrom 0 to 120 seconds

Assessment of the initial viscoelastic properties of a critical segmental long bone defect reconstructed with impaction bone grafting and intramedullary nailing.

INTRODUCTION: This study compared the initial viscoelastic properties of a segmental tibial defect stabilized with intramedullary nailing and impaction bone grafting to that of a transverse fracture stabilized with intramedullary nailing. MATERIALS AND METHODS: Seven sheep tibiae were tested in compression (1000N), bending and torsion (6Nm) in a six degree-of-freedom hexapod robot. Tests were repeated across three groups: intact tibia (Intact), transverse fracture stabilized by intramedullary nailing (Fracture), and segmental defect stabilized with a nail and impaction bone grafting (Defect). Repeated measures ANOVA on the effect of group on stiffness/phase angle were conducted for each loading direction. RESULTS: The Intact group was significantly stiffer than the Fracture and Defect groups in bending and torsion (p<0.022 for both loading directions), and was marginal for the Defect group in compression (p=0.052). No significant differences were found between the Fracture and Defect groups (p>0.246 for all loading directions) for stiffness/phase angle. In compression and bending, phase angles were significantly greater for the Fracture and Defect groups compared to Intact (p<0.025), with no significant differences between groups in torsion (p=0.13). Sensitivity analyses conducted between the Fracture and Defect group differences found that they were not of clinical significance. CONCLUSION: The initial properties of a segmental defect stabilized with intramedullary nailing and impaction bone grafting was not clinically significantly different to that of a transverse fracture stabilized with intramedullary nailing.

Rapid assessment of migration and proliferation: a novel 3D high-throughput platform for rational and combinatorial screening of tissue-specific biomaterials.

Designing an ideal biomaterial supportive of multicellular tissue repair is challenging, especially with a poor understanding of the synergy between constituent proteins and growth factors. A brute-force approach, based on screening all possible combinations of proteins and growth factors, is inadequate due to the prohibitively large experimental space coupled with current low-throughput screening techniques. A high-throughput screening platform based on rational and combinatorial strategies for design and testing of proteins and growth factors can significantly impact the discovery of novel tissue-specific biomaterials. Here, we report the development of a flexible high-throughput screening platform, Rapid Assessment of Migration and Proliferation (RAMP), to rapidly investigate cell viability, proliferation, and migration in response to highly miniaturized three-dimensional biomaterial cultures (4-20 µL) with sparingly low cell densities (63-1000 cells per µL for cell arrays; 1 µL of 1000-10,000 cells per µL for migration arrays). The predictions made by RAMP on the efficacy and potency of the biomaterials are in agreement with the predictions made by conventional assays but at a throughput that is at least 100-1000-fold higher. The RAMP assay is therefore a novel approach for the rapid discovery of tissue-specific biomaterials for tissue engineering and regenerative medicine.

A novel flow chamber for biodegradable alloy assessment in physiologically realistic environments.

In order to better understand the in vivo corrosion of biodegradable alloys, it is necessary to replicate the physiological environment as closely as possible. In this study, a novel flow chamber system is developed that allows the investigation of biodegradable alloy corrosion in a simulated physiological environment. The system is designed to reproduce flow conditions encountered in coronary arteries using a parallel plate setup and to allow the culturing of cells. Computational fluid dynamics and analytical methods are used as part of the design process to ensure that suitable flow conditions are maintained in the test region. The system is used to investigate the corrosion behavior of AZ31 alloy foils of different thickness, in test media with and without proteins and in static and dynamic solutions. It is observed that pulsatile flows, similar to those in the coronary arteries, significantly increase corrosion rates and lead to a different corrosion surface morphologies relative to static immersion tests.

In vitro assessment of the immunity of implantable cardioverter-defibrillators to magnetic fields of 50/60 Hz.

Public concern for the compatibility of electromagnetic (EM) sources with active implantable medical devices (AIMD) has prompted the development of new systems that can perform accurate exposure studies. EM field interference with active cardiac implants (e.g. implantable cardioverter-defibrillators (ICDs)) can be critical. This paper describes a magnetic field (MF) exposure system and the method developed for testing the immunity of ICD to continuous-wave MFs. The MFs were created by Helmholtz coils, housed in a Faraday cage. The coils were able to produce highly uniform MFs up to 4000 µT at 50 Hz and 3900 µT at 60 Hz, within the test space. Four ICDs were tested. No dysfunctions were found in the generated MFs. These results confirm that the tested ICDs were immune to low frequency MFs.

Assessment of the in-plane biomechanical properties of human skin using a finite element model updating approach combined with an optical full-field measurement on a new tensile device.

Human skin is one of the most important organ of the body. The assessment and knowledge of its properties are very useful for clinical or cosmetic research. Many techniques are used to measure the mechanical properties of this organ, like suction, indentation, torsion or tension tests. The aim of this paper is to present a new device based on tension technique and combining mechanical and optical measurements. The whole procedure used to assess the displacement field as described, and first results of tests performed in vivo are shown.

In vitro assessment of blood compatibility: residual and dynamic markers of cellular activation.

The blood compatibility of materials and surfaces used for medical device fabrication is a crucial factor in their function and effectiveness. Expansion of device use into more sensitive and longer term applications warrants increasingly detailed evaluations of blood compatibility that reach beyond the customary measures mandated by regulatory requirements. A panel of tests that assess both deposition on the surface and activation of circulating blood in contact with the surface has been developed. Specifically, the ability of a surface to modulate the biological response of blood is assessed by measuring: (1) dynamic thrombin generation; (2) surface-bound thrombin activity after exposure to blood; (3) activation of monocytes, polymorphonuclear leukocytes, lymphocytes, and platelets; (4) activation of complement; and (5) adherent monocytes, polymorphonuclear leukocytes, lymphocytes, and platelets on blood-contacting surfaces. The tests were used to evaluate surfaces modified with immobilized heparin (Ension's proprietary bioactive surface) and demonstrated that the modified surfaces reduced platelet activation, leukocyte activation, and complement activation in flowing human blood. Perfusion of the surfaces with human platelet-rich plasma showed that the immobilized heparin surfaces also reduce both dynamic thrombin levels in the circulating plasma and residual thrombin generated at the material surface.