A Soft Total Artificial Heart-First Concept Evaluation on a Hybrid Mock Circulation

Anatomical and Hemodynamic Characterization of Totally Artificial Hearts

We characterize the anatomy and function of never before studied total artificial hearts (TAHs) using established methods for testing mechanical circulatory support (MCS) devices. A historical review of TAHs is also presented to aid in benchmarking performance metrics. Six TAHs, ranging from spooky Halloween beating hearts to a cute colorful plush heart, were imaged, instrumented (mock flow loops) to measure their pressure, volume, and flow, and qualitatively evaluated by 3rd party cardiac surgeons for anatomical accuracy and surgical considerations. Imaging of Claw, Beating, and Frankenstein TAHs revealed internal motors, circuit boards, and speakers. Gummy TAH was ranked favorite TAH for tactile realism, while Frankenstein TAH had the most favorable audible/visual indicators, including an illuminated Jacob's Ladder. Beating TAH demonstrated superior pulsatile hemodynamic performance compared to Claw TAH (16mL vs 1.3mL stroke volume). Light Up TAH and Gummy TAH functioned only as passive compliance chambers. Cute TAH rapidly exsanguinated due to its porosity (-3.0 L/min flow). These TAHs demonstrated a wide range of anatomical accuracy, surgeon appeal, unique features, and hemodynamic performance. While Claw TAH and Beating TAH successfully generated a modicum of pulsatility, we recommend the clinical community continue to support pre-clinical development of emerging or use of clinically-approved TAHs.

Review of Systemic Mock Circulation Loops for Evaluation of Implantable Cardiovascular Devices and Biological Tissues

CLINICAL IMPACT

On needs-based ex vivo monitoring of implantable devices or tissues/organs in cardiovascular simulators provides new insights and paves new paths for device prototypes. The insights gained could not only support the needs of patients, but also inform engineers, scientists and clinicians about undiscovered aspects of diseases (during routine monitoring). We analyze seminal and current work and highlight a variety of opportunities for developing preclinical tools that would improve strategies for future implantable devices. Holistically, mock circulation loop studies can bridge the gap between in vivo and in vitro approaches, as well as clinical and laboratory settings, in a mutually beneficial manner.

Biomimetic Closed-Loop Control of a Novel Soft Gastric Simulator Toward Emulating Antral Contraction Waves

Soft gastric simulators are in vitro biomimetic modules that can reproduce the antral contraction waves (ACWs). Along with providing information concerning stomach contents, stomach simulators enable experts to evaluate the digestion process of foods and drugs. Traditionally, open-loop control approaches were implemented on stomach simulators to produce ACWs. Constructing a closed-loop control system is essential to improve the simulator's ability to imitate ACWs in additional scenarios and avoid constant tuning. Closed-loop control can enhance stomach simulators in accuracy, responding to various food and drug contents, timing, and unknown disturbances. In this article, a new generation of anatomically realistic soft pneumatic gastric simulators is designed and fabricated. The presented simulator represents the antrum, the lower portion of the stomach where ACWs occur. It is equipped with a real-time feedback system to implement diverse closed-loop controllers on demand. All the details of the physical design, fabrication, and assembly process are discussed. Also, the measures taken for the mechatronics design and sensory system are highlighted in this article. Through several implementation algorithms and techniques, three closed-loop controllers, including model-based and model-free schemes are designed and successfully applied on the presented simulator to imitate ACWs. All the experimental outcomes are carefully analyzed and compared against the biological counterparts. It is demonstrated that the presented simulator can serve as a reliable tool and method to scrutinize digestion and promote novel technologies around the human stomach and the digestion process. This research methodology can also be utilized to develop other biomimetic and bioinspired applications.

Biorobotic hybrid heart as a benchtop cardiac mitral valve simulator

In this work, we developed a high-fidelity beating heart simulator that provides accurate mitral valve pathophysiology. The benchtop platform is based on a biorobotic hybrid heart that combines preserved intracardiac tissue with soft robotic cardiac muscle providing dynamic left ventricular motion and precise anatomical features designed for testing intracardiac devices, particularly for mitral valve repair. The heart model is integrated into a mock circulatory loop, and the active myocardium drives fluid circulation producing physiological hemodynamics without an external pulsatile pump. Using biomimetic soft robotic technology, the heart can replicate both ventricular and septal wall motion, as well as intraventricular pressure-volume relationships. This enables the system to recreate the natural motion and function of the mitral valve, which allows us to demonstrate various surgical and interventional techniques. The biorobotic cardiovascular simulator allows for real-time hemodynamic data collection, direct visualization of the intracardiac procedure, and compatibility with clinical imaging modalities.

Balancing the ventricular outputs of pulsatile total artificial hearts

BACKGROUND

Maintaining balanced left and right cardiac outputs in a total artificial heart (TAH) is challenging due to the need for continuous adaptation to changing hemodynamic conditions. Proper balance in ventricular outputs of the left and right ventricles requires a preload-sensitive response and mechanisms to address the higher volumetric efficiency of the right ventricle.

METHODS

This review provides a comprehensive overview of various methods used to balance left and right ventricular outputs in pulsatile total artificial hearts, categorized based on their actuation mechanism.

RESULTS

Reported strategies include incorporating compliant materials and/or air cushions inside the ventricles, employing active control mechanisms to regulate ventricular filling state, and utilizing various shunts (such as hydraulic or intra-atrial shunts). Furthermore, reducing right ventricular stroke volume compared to the left often serves to balance the ventricular outputs. Individually controlled actuation of both ventricles in a pulsatile TAH seems to be the simplest and most effective way to achieve proper preload sensitivity and left-right output balance. Pneumatically actuated TAHs have the advantage to respond passively to preload changes.

CONCLUSION

Therefore, a pneumatic TAH that comprises two individually actuated ventricles appears to be a more desirable option-both in terms of simplicity and efficacy-to respond to changing hemodynamic conditions.

Vision-controlled jetting for composite systems and robots

Recreating complex structures and functions of natural organisms in a synthetic form is a long-standing goal for humanity1. The aim is to create actuated systems with high spatial resolutions and complex material arrangements that range from elastic to rigid. Traditional manufacturing processes struggle to fabricate such complex systems2. It remains an open challenge to fabricate functional systems automatically and quickly with a wide range of elastic properties, resolutions, and integrated actuation and sensing channels2,3. We propose an inkjet deposition process called vision-controlled jetting that can create complex systems and robots. Hereby, a scanning system captures the three-dimensional print geometry and enables a digital feedback loop, which eliminates the need for mechanical planarizers. This contactless process allows us to use continuously curing chemistries and, therefore, print a broader range of material families and elastic moduli. The advances in material properties are characterized by standardized tests comparing our printed materials to the state-of-the-art. We directly fabricated a wide range of complex high-resolution composite systems and robots: tendon-driven hands, pneumatically actuated walking manipulators, pumps that mimic a heart and metamaterial structures. Our approach provides an automated, scalable, high-throughput process to manufacture high-resolution, functional multimaterial systems.

Soft robotics in wearable and implantable medical applications: Translational challenges and future outlooks

This work explores the recent research conducted towards the development of novel classes of devices in wearable and implantable medical applications allowed by the introduction of the soft robotics approach. In the medical field, the need for materials with mechanical properties similar to biological tissues is one of the first considerations that arises to improve comfort and safety in the physical interaction with the human body. Thus, soft robotic devices are expected to be able of accomplishing tasks no traditional rigid systems can do. In this paper, we describe future perspectives and possible routes to address scientific and clinical issues still hampering the accomplishment of ideal solutions in clinical practice.

Research Progress of Three-Dimensional Bioprinting Artificial Cardiac Tissue

Cardiovascular disease is one of the main diseases that endanger human life and health, and heart failure often occurs when the cardiovascular disease develops to the end-stage. Heart transplantation is the most effective treatment. However, there has always been a shortage of living heart organs. With the development of regenerative medicine, researchers have turned to bioprinting technology that can build tissues and organs in vitro. A large number of relevant literature on three-dimensional (3D) bioprinted hearts were searched and screened in Google Scholar. 3D bioprinting technology can accurately print biomaterials containing living cells into 3D functional living tissues, providing a feasible solution to the shortage of transplantable organs. As one of the most important organs in the human body, the research on 3D bioprinting of the heart has currently become a hot topic. This paper briefly overviews 3D bioprinting technology and the progress in bioprinting cardiac tissue. It is believed that in the future, bio-printed hearts will become a reality, making a new way of providing artificial organs for heart transplantation.

Early career scientists converse on the future of soft robotics

During the recent decade, we have witnessed an extraordinary flourishing of soft robotics. Rekindled interest in soft robots is partially associated with the advances in manufacturing techniques that enable the fabrication of sophisticated multi-material robotic bodies with dimensions ranging across multiple length scales. In recent manuscripts, a reader might find peculiar-looking soft robots capable of grasping, walking, or swimming. However, the growth in publication numbers does not always reflect the real progress in the field since many manuscripts employ very similar ideas and just tweak soft body geometries. Therefore, we unreservedly agree with the sentiment that future research must move beyond "soft for soft's sake." Soft robotics is an undoubtedly fascinating field, but it requires a critical assessment of the limitations and challenges, enabling us to spotlight the areas and directions where soft robots will have the best leverage over their traditional counterparts. In this perspective paper, we discuss the current state of robotic research related to such important aspects as energy autonomy, electronic-free logic, and sustainability. The goal is to critically look at perspectives of soft robotics from two opposite points of view provided by early career researchers and highlight the most promising future direction, that is, in our opinion, the employment of soft robotic technologies for soft bio-inspired artificial organs.

The ongoing quest for the first total artificial heart as destination therapy

Many patients with end-stage heart disease die because of the scarcity of donor hearts. A total artificial heart (TAH), an implantable machine that replaces the heart, has so far been successfully used in over 1,700 patients as a temporary life-saving technology for bridging to heart transplantation. However, after more than six decades of research on TAHs, a TAH that is suitable for destination therapy is not yet available. High complication rates, bulky devices, poor durability, poor biocompatibility and low patient quality of life are some of the major drawbacks of current TAH devices that must be addressed before TAHs can be used as a destination therapy. Quickly emerging innovations in battery technology, wireless energy transmission, biocompatible materials and soft robotics are providing a promising opportunity for TAH development and might help to solve the drawbacks of current TAHs. In this Review, we describe the milestones in the history of TAH research and reflect on lessons learned during TAH development. We summarize the differences in the working mechanisms of these devices, discuss the next generation of TAHs and highlight emerging technologies that will promote TAH development in the coming decade. Finally, we present current challenges and future perspectives for the field.

Progress of 3D Printing Techniques for Nasal Cartilage Regeneration

Once cartilage is damaged, its self-repair capacity is very limited. The strategy of tissue engineering has brought a new idea for repairing cartilage defect and cartilage regeneration. In particular, nasal cartilage regeneration is a challenge because of the steady increase in nasal reconstruction after oncologic resection, trauma, or rhinoplasty. From this perspective, three-dimensional (3D) printing has emerged as a promising technology to address the complexity of nasal cartilage regeneration, using patient's image data and computer-aided deposition of cells and biomaterials to precisely fabricate complex, personalized tissue-engineered constructs. In this review, we summarized the major progress of three prevalent 3D printing approaches, including inkjet-based printing, extrusion-based printing and laser-assisted printing. Examples are highlighted to illustrate 3D printing for nasal cartilage regeneration, with special focus on the selection of seeded cell, scaffolds and growth factors. The purpose of this paper is to systematically review recent research about the challenges and progress and look forward to the future of 3D printing techniques for nasal cartilage regeneration.Level of Evidence III This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors https://www.springer.com/00266 .

3D Antidrying Antifreezing Artificial Skin Device with Self-Healing and Touch Sensing Capability

Hydrogels are attractive, active materials for various e-skin devices based on their unique functionalities such as flexibility and biocompatibility. Still, e-skin devices are generally limited to simple structures, and the realization of optimal-shaped 3D e-skin devices for target applications is an intriguing issue of interest. Furthermore, hydrogels intrinsically suffer from drying and freezing issues in operational capability for practical applications. Herein, 3D artificial skin devices are demonstrated with highly improved device stability. The devices are fabricated in a target-oriented 3D structure by extrusion-based 3D printing, spontaneously heal mechanical damage, and enable stable device operation over time and under freezing conditions. Based on the material design to improve drying and freezing resistance, an organohydrogel, prepared by solvent displacement of hydrogel with ethylene glycol for 3 h, exhibits excellent drying resistance over 1000 h and improved freezing resistance by showing no phase transition down to -60 °C while maintaining its self-healing functionality. Based on the improved drying and freezing resistance, artificial skin devices in target-oriented optimal 3D structures are presented, which enable accurate positioning of touchpoints even on a complicated 3D structure stably over time and excellent operation at temperatures below 0 °C without losing their flexibility.

The hemodynamic power of the heart differentiates normal from diseased right ventricles

Cardiac mechanics is primarily described by the pressure-volume relationship. The ventricular pressure-volume loop displays the instantaneous relationship between intraventricular pressure and volume throughout the cardiac cycle; however, it does not consider the shape of the ventricles, their spatiotemporal deformation patterns, and how these balance with the flowing blood. Our study demonstrates that the pressure-volume relationship represents a first level of approximation for the mechanical power of the ventricles, while, at a further level of approximation, the importance of hemodynamic power emerges through the balance between deformation patterns and fluid dynamics. The analysis is preliminarily tested in a healthy subject's right ventricle and two patients. Moreover, patients' geometry was then rescaled to present a normal volumetric profile to verify whether results were affected by volume size or by the spatiotemporal pattern of how that volume profile was achieved. Results show that alterations of hemodynamic power were found in the abnormal ventricles and that they were not directly caused by the ventricular size but by changes in the ability of intraventricular pressure gradient to generate blood flow. Therefore, hemodynamic power represents a physics-based measure that takes into account the dynamics of the space-time shape changes in combination with blood flow. Hemodynamic power is assessed non-invasively using cardiac imaging techniques and can be an early indicator of cardiac dysfunction before changes occur in volumetric measurements. These preliminary results provide a physical ground to evaluate its diagnostic or prognostic significance in future clinical studies.

Involvement of Machine Learning Tools in Healthcare Decision Making

In the present day, there are many diseases which need to be identified at their early stages to start relevant treatments. If not, they could be uncurable and deadly. Due to this reason, there is a need of analysing complex medical data, medical reports, and medical images at a lesser time but with greater accuracy. There are even some instances where certain abnormalities cannot be directly recognized by humans. In healthcare for computational decision making, machine learning approaches are being used in these types of situations where a crucial data analysis needs to be performed on medical data to reveal hidden relationships or abnormalities which are not visible to humans. Implementing algorithms to perform such tasks itself is difficult, but what makes it even more challenging is to increase the accuracy of the algorithm while decreasing the required time for the algorithm to execute. In the early days, processing of large amount of medical data was an important task which resulted in machine learning being adapted in the biological domain. Since this happened, the biology and biomedical fields have been reaching higher levels by exploring more knowledge and identifying relationships which were never observed before. Reaching to its peak now the concern is being diverted towards treating patients not only based on the type of disease but also their genetics, which is known as precision medicine. Modifications in machine learning algorithms are being performed and tested daily to improve the performance of the algorithms in analysing and presenting more accurate information. In the healthcare field, starting from information extraction from medical documents until the prediction or diagnosis of a disease, machine learning has been involved. Medical imaging is a section that was greatly improved with the integration of machine learning algorithms to the field of computational biology. Nowadays, many disease diagnoses are being performed by medical image processing using machine learning algorithms. In addition, patient care, resource allocation, and research on treatments for various diseases are also being performed using machine learning-based computational decision making. Throughout this paper, various machine learning algorithms and approaches that are being used for decision making in the healthcare sector will be discussed along with the involvement of machine learning in healthcare applications in the current context. With the explored knowledge, it was evident that neural network-based deep learning methods have performed extremely well in the field of computational biology with the support of the high processing power of modern sophisticated computers and are being extensively applied because of their high predicting accuracy and reliability. When giving concern towards the big picture by combining the observations, it is noticeable that computational biology and biomedicine-based decision making in healthcare have now become dependent on machine learning algorithms, and thus they cannot be separated from the field of artificial intelligence.

Applications of 3D bioprinting in tissue engineering: advantages, deficiencies, improvements, and future perspectives

Over the past decade, 3D bioprinting technology has progressed tremendously in the field of tissue engineering in its ability to fabricate individualized biological constructs with precise geometric designability, which offers us the capability to bridge the divergence between engineered tissue constructs and natural tissues. In this work, we first review the current widely used 3D bioprinting approaches, cells, and materials. Next, the updated applications of this technique in tissue engineering, including bone tissue, cartilage tissue, vascular grafts, skin, neural tissue, heart tissue, liver tissue and lung tissue, are briefly introduced. Then, the prominent advantages of 3D bioprinting in tissue engineering are summarized in detail: rapidly prototyping the customized structure, delivering cell-laden materials with high precision in space, and engineering with a highly controllable microenvironment. The current technical deficiencies of 3D bioprinted constructs in terms of mechanical properties and cell behaviors are afterward illustrated, as well as corresponding improvements. Finally, we conclude with future perspectives about 3D bioprinting in tissue engineering.

Increased Longevity and Pumping Performance of an Injection Molded Soft Total Artificial Heart

In this work, we present an injection molded soft total artificial heart (sTAH) produced from high-temperature vulcanizing silicone using an industrial metal injection mold. At 60 beats per minute, the sTAH exhibited a total cardiac output of over 16 L/min against physiological pressures on a mock circulation and was pumped continuously for 110,000 actuation cycles. Finite element analysis was used to identify stress concentrations within the sTAH, allowing an optimized design to be proposed.

Hemodynamic performance of a compact centrifugal left ventricular assist device with fully magnetic levitation under pulsatile operation: An in vitro study

Long-term using continuous flow ventricular assist devices could trigger complications associated with diminished pulsatility, such as valve insufficiency and gastrointestinal bleeding. One feasible solution is to produce pulsatile flow assist with speed regulation in continuous flow ventricular assist devices. A third-generation blood pump with pulsatile operation control algorithm was first characterized alone under pulsatile mode at various speeds, amplitudes, and waveforms. The pump was then incorporated in a Mock circulation system to evaluate in vitro hemodynamic effects when using continuous and different pulsatile operations. Pulsatility was evaluated by surplus hemodynamic energy. Results showed that pulsatile operations provided sufficient hemodynamic assistance and increased pulsatility of the circulatory system (53% increment), the mean aortic pressure (65% increment), and cardiac output (27% increment). The pulsatility of the system under pulsatile operation support was increased 147% compared with continuous operation support. The hemodynamic performance of pulsatile operations is susceptible to phase shifts, which could be a tacking angle for physiological control optimization. This study found third-generation blood pumps using different pulsatile operations for ventricular assistance promising.

3D printing tissue-mimicking materials for realistic transseptal puncture models

Applications of additive manufacturing (commonly referred to as 3D printing) in direct fabrication of models for pre-surgical planning, functional testing, and medical training are on the rise. However, one current limitation to the accuracy of models for cardiovascular procedural training is a lack of printable materials that accurately mimic human tissue. Most of the available elastomeric materials lack mechanical properties representative of human tissues. To address the gap, the authors explore the multi-material capability of material jetting additive manufacturing to combine non-curing and photo-curing inks to achieve material properties that more closely replicate human tissues. The authors explore the impact of relative material concentration on tissue-relevant properties from puncture and tensile testing under submerged conditions. Further, the authors demonstrate the ability to mimic the mechanical properties of the fossa ovalis, which proves beneficial for accurately simulating transseptal punctures. A fossa ovalis mimic was printed and assembled within a full patient-specific heart model for validation, where it exhibited accuracy in both mechanical properties and geometry. The explored material combination provides the opportunity to fabricate future medical models that are more realistic and better suited for pre-surgical planning and medical student training. This will ultimately guide safer, more efficient practices.

Experimental Mechanical Examination of Artificial 3D Printed and Post Processed Vascular Silicone Models

Anatomical models have gained increasing visibility over the last years. Their application in surgical education could have a great impact and many benefits. Vascular haptic models consist of soft materials like silicones, which can be 3D printed for complex geometries. This study focuses on quantifying mechanical behaviors as tensile strength, elongation and Shore A hardness for healthy and pathological silicone based vascular models. The quantification enables a more specific modelling of vessel properties, which leads to a more accurate simulation and therefore better education.

A review of recent advancements in soft and flexible robots for medical applications

BACKGROUND

Soft and flexible robots for medical applications are needed to change their flexibility over a wide range to perform tasks adequately. The mechanism and theory of flexibility has been a scientific issue and is of interest to the community.

METHODS

Recent advancements of bionics, flexible actuation, sensing, and intelligent control algorithms as well as tunable stiffness have been referenced when soft and flexible robots are developed. The benefits and limitations of these relevant studies and how they affect the flexibility are discussed, and possible research directions are explored.

RESULTS

The bionic materials and structures that demonstrate the potential capabilities of the soft medical robot flexibility are the fundamental guarantee for clinical medical applications. Flexible actuation that used to provide power, intelligent control algorithms which are the exact executors, and the wide range stiffness of the soft materials are the three important influence factors for soft medical robots.

CONCLUSION

Some reasonable suggestions and possible solutions for soft and flexible medical robots are proposed, including novel materials, flexible actuation concepts with a built-in source of energy or power, programmable flexibility, and adjustable stiffness.

Three-Dimensional Self-Healable Touch Sensing Artificial Skin Device

Human skin is a unique functional material that perfectly covers body parts having various complicated shapes, spontaneously heals mechanical damage, and senses a touch. E-skin devices have been actively researched, focusing on the sensing functionality of skin. However, most e-skin devices still have limitations in their shapes, and it is a challenging issue of interest to realize multiple functionalities in one device as human skin does. Here, new artificial skin devices are demonstrated in application-oriented three-dimensional (3D) shapes, which can sense exact touch location and heal mechanical damage spontaneously. Beyond the conventional film-type e-skin devices, the artificial skin devices are fabricated in optimal three-dimensional structures, via systematic material design and characterization of ion-conductive self-healing hydrogel system and its extrusion-based 3D printing. The ring-shaped and fingertip-shaped artificial skin devices are successfully fabricated to fit perfectly on finger models, and shows large electronic signal contrast, ∼5.4 times increase in current, upon a human finger contact. Furthermore, like human skin, the device provides the exact positional information of an arbitrary touch location on a three-dimensional artificial skin device without complicated device fabrication or data processing.

Design and Modeling of a Soft Artificial Heart by Using the SolidWorks and ANSYS

Investigating the biomechanical behaviour of a soft artificial heart is a hard task as such things are very complicated in terms of both material properties and geometry. This work focused on developing, designing, modelling and analysing a new generation, low cost, easily operable, full-size, low power consumption, and durable soft artificial heart intended to replace an original heart on a parmanent basis. Numerical simulation and investigation of the artificial heart were implemented using SolidWorks 17 and ANSYS 15.7, with a Multiphysics static structural model, fluent fluid flow (CFX), and fluent fluid poly-flow (CFD) analysis systems used in order to determine the dynamic response and effects of pressurised blood on heart performance during blood flow cycles. The biomechanical modeling and analysis of the soft artificial heart were implemented using the finite element modelling in ANSYS R18.0. To improve and verify the biomechanical performance, Design Expert 11.0 software and a response surface methodology (RSM) technique were used. The simulation results showed that as maximum levels of absolute pressure were applied on the ventricles and air pressurised chambers, the performance of the heart remained secure. The results also showed that strain energy, total deformation, maximum principal elastic strain, stress and fatigue safety factors, and fatigue life all reached thier optimum values when using the SIBSTAR 103T with polyetherimide/silicone (PSN4) Nano-composite elastomers.

On Replacement Body Parts

Technological advances are making devices that functionally replace body parts-artificial organs and limbs-more widely used, and more capable of providing patients with lives that are close to "normal." Some of the ethical issues this is likely to raise relate to how such prostheses are conceptualized. Prostheses are ambiguous between being inanimate objects and sharing in the status of human bodies-which already have an ambiguous status, as both objects and subjects. At the same time, the possibility of replacing body parts with artificial objects puts pressure on the normative status typically accorded to human bodies, seemingly confirming that body parts are replaceable objects. The paper argues that bodies' normative status relies on the relation of a body to a person and shows that persons could have similar relations to prostheses. This suggests that in approaching ethical issues surrounding prostheses, it is appropriate to regard them as more like body parts than like objects.

Ultrasonic sensor concept to fit a ventricular assist device cannula evaluated using geometrically accurate heart phantoms

Future left ventricular assist devices (LVADs) are expected to respond to the physiologic need of patients; however, they still lack reliable pressure or volume sensors for feedback control. In the clinic, echocardiography systems are routinely used to measure left ventricular (LV) volume. Until now, echocardiography in this form was never integrated in LVADs due to its computational complexity. The aim of this study was to demonstrate the applicability of a simplified ultrasonic sensor to fit an LVAD cannula and to show the achievable accuracy in vitro. Our approach requires only two ultrasonic transducers because we estimated the LV volume with the LV end-diastolic diameter commonly used in clinical assessments. In order to optimize the accuracy, we assessed the optimal design parameters considering over 50 orientations of the two ultrasonic transducers. A test bench was equipped with five talcum-infused silicone heart phantoms, in which the intra-ventricular surface replicated papillary muscles and trabeculae carnae. The end-diastolic LV filling volumes of the five heart phantoms ranged from 180 to 480 mL. This reference volume was altered by ±40 mL with a syringe pump. Based on the calibrated measurements acquired by the two ultrasonic transducers, the LV volume was estimated well. However, the accuracies obtained are strongly dependent on the choice of the design parameters. Orientations toward the septum perform better, as they interfere less with the papillary muscles. The optimized design is valid for all hearts. Considering this, the Bland-Altman analysis reports the LV volume accuracy as a bias of ±10% and limits of agreement of 0%-40% in all but the smallest heart. The simplicity of traditional echocardiography systems was reduced by two orders of magnitude in technical complexity, while achieving a comparable accuracy to 2D echocardiography requiring a calibration of absolute volume only. Hence, our approach exploits the established benefits of echocardiography and makes them applicable as an LV volume sensor for LVADs.

Modification of silicone elastomers with Bioglass 45S5® increases in ovo tissue biointegration

Silicone is an important material family used for various medical implants. It is biocompatible, but its bioinertness prevents cell attachment, and thus tissue biointegration of silicone implants. This often results in constrictive fibrosis and implant failure. Bioglass 45S5® (BG) could be a suitable material to alter the properties of silicone, render it bioactive and improve tissue integration. Therefore, BG micro- or nanoparticles were blended into medical-grade silicone and 2D as well as 3D structures of the resulting composites were analyzed in ovo by a chick chorioallantoic membrane (CAM) assay. The biomechanical properties of the composites were measured and the bioactivity of the composites was verified in simulated body fluid. The bioactivity of BG-containing composites was confirmed visually by the formation of hydroxyapatite through scanning electron microscopy as well as by infrared spectroscopy. BG stiffens as prepared non-porous composites by 13% and 36% for micro- and nanocomposites respectively. In particular, after implantation for 7 days, the Young's modulus had increased significantly from 1.20 ± 0.01 to 1.57 ± 0.03 MPa for microcomposites and 1.44 ± 0.03 to 1.69 ± 0.29 MPa to for nanocpmosites. Still, the materials remain highly elastic and are comparably soft. The incorporation of BG into silicone overcame the bioinertness of the pure polymer. Although the overall tissue integration was weak, it was significantly improved for BG-containing porous silicones (+72% for microcomposites) and even further enhanced for composites containing nanoparticles (+94%). These findings make BG a suitable material to improve silicone implant properties. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1180-1188, 2019.

Data related to the experimental design for powder bed binder jetting additive manufacturing of silicone

The data included in this article provides additional supporting information on our recent publication (Liravi et al., 2018 [1]) on a novel hybrid additive manufacturing (AM) method for fabrication of three-dimensional (3D) structures from silicone powder. A design of experiments (DoE) study has been carried out to optimize the geometrical fidelity of AM-made parts. This manuscript includes the details of a multi-level factorial DOE and the response optimization results. The variation in the temperature of powder-bed when exposed to heat is plotted as well. Furthermore, the effect of blending ratio of two parts of silicone binder on its curing speed was investigated by conducting DSC tests on a silicone binder with 100:2 precursor to curing agent ratio. The hardness of parts fabricated with non-optimum printing conditions are included and compared.

Artificial Organs 2017: A Year in Review

In this Editor's Review, articles published in 2017 are organized by category and summarized. We provide a brief reflection of the research and progress in artificial organs intended to advance and better human life while providing insight for continued application of these technologies and methods. Artificial Organs continues in the original mission of its founders "to foster communications in the field of artificial organs on an international level." Artificial Organs continues to publish developments and clinical applications of artificial organ technologies in this broad and expanding field of organ Replacement, Recovery, and Regeneration from all over the world. Peer-reviewed Special Issues this year included contributions from the 12th International Conference on Pediatric Mechanical Circulatory Support Systems and Pediatric Cardiopulmonary Perfusion edited by Dr. Akif Undar, Artificial Oxygen Carriers edited by Drs. Akira Kawaguchi and Jan Simoni, the 24th Congress of the International Society for Mechanical Circulatory Support edited by Dr. Toru Masuzawa, Challenges in the Field of Biomedical Devices: A Multidisciplinary Perspective edited by Dr. Vincenzo Piemonte and colleagues and Functional Electrical Stimulation edited by Dr. Winfried Mayr and colleagues. We take this time also to express our gratitude to our authors for offering their work to this journal. We offer our very special thanks to our reviewers who give so generously of time and expertise to review, critique, and especially provide meaningful suggestions to the author's work whether eventually accepted or rejected. Without these excellent and dedicated reviewers the quality expected from such a journal could not be possible. We also express our special thanks to our Publisher, John Wiley & Sons for their expert attention and support in the production and marketing of Artificial Organs. We look forward to reporting further advances in the coming years.