Design and Analysis of a Polymeric Left Ventricular Simulator via Computational Modelling.

Preclinical testing of medical devices is an essential step in the product life cycle, whereas testing of cardiovascular implants requires specialised testbeds or numerical simulations using computer software Ansys 2016. Existing test setups used to evaluate physiological scenarios and test cardiac implants such as mock circulatory systems or isolated beating heart platforms are driven by sophisticated hardware which comes at a high cost or raises ethical concerns. On the other hand, computational methods used to simulate blood flow in the cardiovascular system may be simplified or computationally expensive. Therefore, there is a need for low-cost, relatively simple and efficient test beds that can provide realistic conditions to simulate physiological scenarios and evaluate cardiovascular devices. In this study, the concept design of a novel left ventricular simulator made of latex rubber and actuated by pneumatic artificial muscles is presented. The designed left ventricular simulator is geometrically similar to a native left ventricle, whereas the basal diameter and long axis length are within an anatomical range. Finite element simulations evaluating left ventricular twisting and shortening predicted that the designed left ventricular simulator rotates approximately 17 degrees at the apex and the long axis shortens around 11 mm. Experimental results showed that the twist angle is 18 degrees and the left ventricular simulator shortens 5 mm. Twist angles and long axis shortening as in a native left ventricle show it is capable of functioning like a native left ventricle and simulating a variety of scenarios, and therefore has the potential to be used as a test platform.

Parametric Design and Prototyping of a Low-Power Planar Biped Robot.

This study proposes a design approach and the development of a low-power planar biped robot named YU-Bibot. The kinematic structure of the robot consists of six independently driven axes, and it weighs approximately 20 kg. Based on biomimetics, the robot dimensions were selected as the average anthropomorphic dimensions of the human lower extremities. The optimization of the mechanical design and actuator selection of the robot was based on the results of parametric simulations. The natural human walking gait was mimicked as a walking pattern in these simulations. As a result of the optimization, a low power-to-weight ratio of 30 W/kg was obtained. The drive system of the robot joints consists of servo-controlled brushless DC motors with reduction gears and additional bevel gears at the knee and ankle joints. The robot features spring-supported knee and ankle joints that counteract the robot's weight and compensate for the backlash present in these joints. The robot is constrained to move only in the sagittal plane by using a lateral support structure. The robot's feet are equipped with low-cost, force-sensitive resistor (FSR)-type sensors for monitoring ground contact and zero-moment point (ZMP) criterion. The experimental results indicate that the proposed robot mechanism can follow the posture commands accurately and demonstrate locomotion at moderate stability. The proposed parametric natural gait simulation-based design approach and the resulting biped robot design with a low power/weight ratio are the main contributions of this study.

The effect of fundamental curves on geometric orifice and coaptation areas of polymeric heart valves.

Valvular diseases, such as aortic stenosis, are considered a common condition in the US. In severe cases, either mechanical or prosthetic heart valves are employed to replace the diseased native valve. The prosthetic heart valve has been a focal point for researchers to gain a better understanding of the mechanics, which will lead to improved longevity. In this study, our objective was to evaluate the effect of fundamental curves on the geometric orifice area and the coaptation area by implementing a two-level Taguchi Orthogonal Array (OA) design (Analysis of Variance (ANOVA) technique) and the interaction plots to investigate the individual contributions. The leaflet geometry was represented with the attachment curve, the free edge, and the belly curve. A total of three varying control coordinates were used to form different leaflet surfaces. With two different biocompatible polymers, 16 finite element models were prepared. Each model was subjected to time-varying transvalvular pressure. The results showed that the control coordinate for the belly curve has the highest impact on the coaptation area of the valve models with higher average 100% modulus. The geometric orifice area was affected by both control points of the attachment curve and the belly curve. A similar effect was also observed for the valve models with lower average 100% modulus.