Magnetic shape memory actuators for energy-passive medical implants

该项目的目标是开发基于磁性形状记忆合金的磁场控制致动器，用于能量被动医疗植入物。将建立、测试和研究待开发执行器的技术示范。定义了三个工作包。首先，将推广Tellinen磁滞模型，对磁形状记忆作动元件应变、应力和磁通密度之间的三维磁滞进行现象学建模。目的是建立数值鲁棒和足够精确的磁性形状记忆元件的一维模型，用于多物理场网络模型对动态系统的仿真。该模型的开发重点是磁性形状记忆致动器的典型工作模式和目前可用的Ni-Mn-Ga合金。此外，还将研究模型扩展，以考虑未来的材料、其他操作模式和额外的影响参数，如温度或循环时间。计划使用Modelica语言将这些模型实现到Dymola和SimulationX环境中。在第二个工作包中，这些模型用于设计和研究用于医疗植入物应用的现场控制执行器。工作原理是磁性形状记忆元件位于大气隙内的一种安排。这样就可以将磁激发源放置在身体外部，而带驱动器的植入物则在身体内部。在外部磁场的控制下，植入物在没有任何能量来源的情况下驱动身体内部的机械负荷。必须设计带有线圈和永磁体的磁场源，以提供所需的磁场强度。可实现的性能参数（力、应力、机械功率和功率密度、功率损耗）将进行评估，并通过应用第一个工作包中开发的模型对设计进行优化。第三个工作包打算在两个不同潜在应用的演示中研究所开发的磁性形状致动器。第一个演示品是用于外科牵引应用的小型化、完全植入式致动器，第二个演示品是用于疼痛治疗的植入式药物输液泵的致动器。能量无源磁形状记忆作动器结构简单，元件少，具有小型化、可靠性高、鲁棒性好的特点。相比之下，植入式电磁或热致动器总是需要一个能量存储元件和一个控制电子元件。因此，小型化磁场控制磁形状记忆致动器打开了其他致动器原理所封闭的应用领域，例如在足、手或牙科、口腔和颌面外科。与临床医生合作，计划开发和研究这些执行器的应用潜力。

It is the aim of the project to develop magnetic field controlled actuators based on magnetic shape memory alloys for applications in energy-passive medical implants. Technology demonstrators of the actuators to be developed will be built, tested and investigated. Three work packages are defined.Initially, a generalization of the Tellinen hysteresis model will be used to model phenomenologically the three-dimensional hysteresis between strain, stress and flux density of magnetic shape memory actuator elements. The objective is to develop numerically robust and sufficiently precise one-dimensional models of magnetic shape memory elements for the simulation of dynamic system by multiphysics network models. The development of the models is focused on the typical operation modes of magnetic shape memory actuators and the Ni-Mn-Ga alloys which are currently available. Furthermore, model extensions will be studied which allow to consider future materials, other operational modes and additional influence parameters like temperature or cycle times as well. It is planned to implement the models into the Dymola and SimulationX environments using the Modelica language. In the second work package, the models are used to design and investigate field controlled actuators for medical implant applications. The operating principle is an arrangement where the magnetic shape memory elements are located inside of large air gaps. This allows to place the magnetic excitation sources outside of the body whereas the implant with the actuator is inside. Controlled by the outer magnetic field, the implants drive mechanical loads inside of the body without any energy sources inside of it. Field sources with coils and permanent magnets have to be designed which provide the required field strength. Achievable performance parameters (force, stress, mechanical power and power density, power loss) are to be evaluated and the designs to be optimized by applying the models developed in the first work package. The third work package intends to investigate the developed magnetic shape actuators in two demonstrators of different potential applications. The first demonstrator is a miniaturized, fully implantable actuator for a surgical distraction application, the second is an actuator for an implantable drug infusion pump which can be used for pain therapy. Energy-passive magnetic shape memory actuators have a simple structure with only a few elements which make them capable to be miniaturized, reliable and robust. In contrast, implanted electromagnetic or thermal actuators always need an energy storage element and a control electronics. Therefore, miniaturized field controlled magnetic shape memory actuators open an application field which is closed for other actuator principles, e.g. in foot and hand or dental, oral and maxillo-facial surgery. In co-operation with clinicians, it is planned to develop and investigate the application potential of these actuators.