Development of a Fish Robot Equipped with Novel 3D-Printed Soft Bending Actuators

This paper reports on design and fabrication of a novel soft fish robot. Application of soft actuators for the fish tail will generates continuum bending motion which resembles the natural motion of the fish. However, most soft actuator mechanisms are complex and have low efficiency. Thus, to address this issue we have developed a 3D printed soft bending actuator which can be actuated with an electromotor. The basic design idea of the soft bending actuator is explained, and iteration of the design showed to create the desired motion for the soft tail. The soft actuator has been successfully integrated with fish body and it has been shown that the fish can swim

A novel design of a polymeric aortic valve

Introduction: in this paper we propose a novel method for developing a polymeric heart valve that could potentially offer an optimum solution for a heart valve substitute. The valve design proposed will provide superior hydrodynamic performance and excellent structural integrity. A full description of the design process is given together with an analysis of the hemodynamic performance using a 2-way strongly coupled Fluid Structure Interaction (FSI). Method: a polymeric tri-leaflet heart valve is designed based on a patient's sinus of Valsalva (SOV) geometry. The design strategy aims to improve valve hemodynamic performance as well as valve durability by avoiding stress concentrations in the leaflets and reducing the maximum stress level. The valve dynamics and stress levels are also validated by comparing the predicted data to existing experimental and numerical data. Results: the stress distribution in the valve structure is fully characterized throughout the simulation and Von Mises stress is found to be up to 5.32 Mpa during diastole. The results show that an effective orifice area (EOA) and a pressure drop of 3.22 cm^2, and 3.52 mmHg, respectively, can be achieved using the proposed design. Conclusions: the optimized valve demonstrates high hemodynamic performance with no sign of damaging stress concentration in the entire cardiac cycle

An analytical method informed by clinical imaging data for estimating outlet boundary conditions in computational fluid dynamics analysis of carotid artery blood flow

Abstract Stroke occur mainly due to arterial thrombosis and rupture of cerebral blood vessels. Previous studies showed that blood flow-induced wall shear stress is an essential bio marker for estimating atherogenesis. It is a common practice to use computational fluid dynamics (CFD) simulations to calculate wall shear stress and to quantify blood flow. Reliability of predicted CFD results greatly depends on the accuracy of applied boundary conditions. Previously, the boundary conditions were estimated by varying values so that they matched the clinical data. It is applicable upon the availability of clinical data. Meanwhile, in most cases all that can be accessed are arterial geometry and inflow rate. Consequently, there is a need to devise a tool to estimate boundary values such as resistance and compliance of arteries. This study proposes an analytical framework to estimate the boundary conditions for a carotid artery based on the geometries of the downstream arteries available from clinical images

Numerical Investigation of the Hydrodynamic Characteristics of 3-Fin Surfboard Configurations

Surfing is a popular sport, with the associated market forecast to reach 2.6 billion US dollars by 2027. In the published literature, there is a range of investigations into the performance of surfboard fins. Some studies model a single fin or review the performance of different fin layouts and surface designs. However, the effects of individual fin design features on flow dynamics are not well understood. This study provides numerical analysis into the thruster fin aspects (rake, depth, and base length) and resultant key performance indicators (i) lift and drag coefficients, and (ii) turbulent kinetic energy. The models were simulated in Ansys Fluent R19.1, solving steady Reynolds-averaged Navier–Stokes equations using the SST k−ω turbulence model at a velocity of 7 m/s. The results indicate the performance of fins varies more post-stall. The variations in rake showed the biggest impact on the turbulence intensity at an angle ≥20°. The variations in base length exhibited coefficient trends with greater lift at small angles but significant lift losses at high angles of attack. The variations in depth affected the forces on the fins rather than the performance indicators. Based on these simulations, a proposed fin set was developed that presented the lowest lift losses after the stall point

Dynamic nanohybrid-polysaccharide hydrogels for soft wearable strain sensing

Electroconductive hydrogels with stimuli-free self-healing and self-recovery (SELF) properties and high mechanical strength for wearable strain sensors is an area of intensive research activity at the moment. Most electroconductive hydrogels, however, consist of static bonds for mechanical strength and dynamic bonds for SELF performance, presenting a challenge to improve both properties into one single hydrogel. An alternative strategy to successfully incorporate both properties into one system is via the use of stiff or rigid, yet dynamic nano-materials. In this work, a nano-hybrid modifier derived from nano-chitin coated with ferric ions and tannic acid (TA/Fe@ChNFs) is blended into a starch/polyvinyl alcohol/polyacrylic acid (St/PVA/PAA) hydrogel. It is hypothesized that the TA/Fe@ChNFs nanohybrid imparts both mechanical strength and stimuli-free SELF properties to the hydrogel via dynamic catecholato-metal coordination bonds. Additionally, the catechol groups of TA provide mussel-inspired adhesion properties to the hydrogel. Due to its electroconductivity, toughness, stimuli-free SELF properties, and self-adhesiveness, a prototype soft wearable strain sensor is created using this hydrogel and subsequently tested

3D‐Printed Triboelectric Nanogenerators: State of the Art, Applications, and Challenges

Triboelectric nanogenerator (TENG) development is undergoing rapid progress utilizing the state‐of‐the‐art 3D‐printing technologies. Herein a critical analysis of the latest developments in 3D‐printed wearable and implantable TENGs that can be used to energize small portable electronic and biomedical devices is presented. Recent progress in 3D‐printed triboelectric nanogenerator (3DP‐TENG) materials and architectural formations, as well as their performance, is evaluated for powering systems that implement physiological monitoring, multifunctional sensing, electronic energizing, noise canceling, dust filtering, and self‐healing. Furthermore, the review explicitly focuses on the 3D‐printing approaches used to form stable and robust 3DP‐TENGs. In addition, the key challenges to improving the performance of 3DP‐TENGs for optimal energy harvesting are discussed, and a roadmap is given for research and translation to commercial markets in the next decade

Blood pressure sensors: materials, fabrication methods, performance evaluations and future perspectives

Advancements in materials science and fabrication techniques have contributed to the significant growing attention to a wide variety of sensors for digital healthcare. While the progress in this area is tremendously impressive, few wearable sensors with the capability of real-time blood pressure monitoring are approved for clinical use. One of the key obstacles in the further development of wearable sensors for medical applications is the lack of comprehensive technical evaluation of sensor materials against the expected clinical performance. Here, we present an extensive review and critical analysis of various materials applied in the design and fabrication of wearable sensors. In our unique transdisciplinary approach, we studied the fundamentals of blood pressure and examined its measuring modalities while focusing on their clinical use and sensing principles to identify material functionalities. Then, we carefully reviewed various categories of functional materials utilized in sensor building blocks allowing for comparative analysis of the performance of a wide range of materials throughout the sensor operational-life cycle. Not only this provides essential data to enhance the materials’ properties and optimize their performance, but also, it highlights new perspectives and provides suggestions to develop the next generation pressure sensors for clinical use