A System for Optimizing Medical Device Development Using Finite Element Analysis Predictions

Scale Effects on Performance of BLDC Micromotors for Internal Biomedical Applications: a Finite Element Analysis

This paper theoretically analyses the miniaturization effects on torque, efficiency and thermal behaviour of high torque permanent magnet BLDC motors with ferromagnetic core coils for internal medical devices. Using a finite element model of a 2-phase BLDC motor, scalability laws are provided for diameters between 0.1 and 100 mm and current densities between 1 and 1000 A/mm2. Based in the impact of the cogging torque and overheating of the motor, scale dependent operational limits are calculated. Operational threshold can be determined at the point where cogging torque becomes dominating over total torque, limiting the use of traditional iron-core motors in the micro-scale. To overcome such limitation, a potential solution is to increase the current density in the windings. However, overheating of the motor limits such increase in the current density which is critical for internal medical applications. Current density limits are provided based on three representative in-body thermal scenarios: respiratory tract, body fluid and blood torrent. Maximum current densities and corresponding torque and efficiency have been obtained for different micro-motor sizes considering safe in-body operation as threshold. It is demonstrated the potential application of micro-motors in internal body environments with acceptable performance for sizes down to 0.1 mm diameter.

The Role of Computational Modeling and Simulation in the Total Product Life Cycle of Peripheral Vascular Devices

The total product life cycle (TPLC) of medical devices has been defined by four stages: discovery and ideation, regulatory decision, product launch, and postmarket monitoring. Manufacturers of medical devices intended for use in the peripheral vasculature, such as stents, inferior vena cava (IVC) filters, and stent-grafts, mainly use computational modeling and simulation (CM&S) to aid device development and design optimization, supplement bench testing for regulatory decisions, and assess postmarket changes or failures. For example, computational solid mechanics and fluid dynamics enable the investigation of design limitations in the ideation stage. To supplement bench data in regulatory submissions, manufactures can evaluate the effects of anatomical characteristics and expected in vivo loading environment on device performance. Manufacturers might also harness CM&S to aid root-cause analyses that are necessary when failures occur postmarket, when the device is exposed to broad clinical use. Once identified, CM&S tools can then be used for redesign to address the failure mode and re-establish the performance profile with the appropriate models. The Center for Devices and Radiological Health (CDRH) wants to advance the use of CM&S for medical devices and supports the development of virtual physiological patients, clinical trial simulations, and personalized medicine. Thus, the purpose of this paper is to describe specific examples of how CM&S is currently used to support regulatory submissions at different phases of the TPLC and to present some of the stakeholder-led initiatives for advancing CM&S for regulatory decision-making.