Functionalisation of implants by use of shape memory materials for temperature and force sensitive applications

通过使用形状记忆材料对温度和力敏感的应用进行植入物的功能化

• 批准号: 316068314
• 负责人: Dr. Thomas Stephan Rau
• 金额: --
• 依托单位: Verbundinstitut für AudioNeurotechnologie und Nanobiomaterialien (VIANNA)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/316068314?language=en
• 关键词: Functionalisation; implants; use; shape; memory

Shape memory materials, above all Nitinol, are of particular interest for minimally invasive applications in medicine. Their unique material properties allow a high degree of miniaturization and the realization of actuator functions. However, the design process of such shape memory actuators is complex and insufficiently controlled. Therefore, the use of Nitinol in medical engineering is up to now restricted to applications which do not require an accurate temperature-dependent behavior or for which the actuation movement can be generously and coarsely designed. This is the case when the transformation temperatures can be chosen considerably below or above body temperature or when the surrounding tissues are sufficiently robust (e.g. bone around compression staples).The situation is different when functionalizing the electrode carrier of a cochlear implant (CI) by use of Nitinol. The desired change of its shape from a straight configuration required for implantation towards a spiral shape (adapted to the cochlea) suggests the use of shape memory materials. However, an unsolved challenge is the concurrent preservation of the functionally important, membranous structures inside the inner ear. Consequently, the temperature-dependent actuation movement and the corresponding forces on the surrounding tissue have to be controllable and adjusted very accurately. In addition, the narrow surgical access causes a high heat input from the surrounding tissues, so that a precise timing of the temperature-dependent actuator is crucial. Thus, the cochlear implant serves as a prime example of a clinical application that requires both a very accurate adjustment of the thermo-mechanical behavior of the actuator to the clinical conditions as well as sufficient strategies to control the heat flow.The proposed research project will address the special challenges of using thin Nitinol wires as actuator elements applied to the concrete example of the CI. The aim is to develop a sound knowledge for the dimensioning of wiry Nitinol shape memory actuators. Therefore, the influence of external forces on the thermal hysteresis will be quantified by a systematic thermo-mechanical characterization of different wire samples. This will be complemented by investigating the interdependence of the thermo-mechanical behaviour and the clinical preconditions (thermal: physiological threshold values, geometrical: anatomical boundaries, mechanical: maximum permissible contact forces). In addition, cooling methods suitable for the OR will be developed and active heating (externally controlled activation of the shape memory effect) will be experimentally investigated. Resulting surface temperatures will be quantified by use of thermography. This application-oriented basic research should support a broader utilization of miniaturized Nitinol shape memory actuators in medical technology.

形状记忆材料，尤其是镍钛合金，在医学上具有微创的应用价值。其独特的材料特性允许高度小型化和实现执行器功能。然而，这种形状记忆执行器的设计过程复杂，控制不够充分。因此，到目前为止，镍钛在医学工程中的使用仅限于不需要精确的温度依赖行为或可以慷慨而粗略地设计驱动运动的应用。当转换温度可以选择远低于或高于体温或当周围组织足够坚固(例如，加压钉周围的骨骼)时，情况就是如此。当使用镍钛使人工耳蜗体(CI)的电极载体功能化时，情况就不同了。其形状从植入所需的直形形状转变为螺旋形(适合于耳蜗)的期望变化表明使用形状记忆材料。然而，一个尚未解决的挑战是同时保留内耳内具有重要功能的膜性结构。因此，温度相关的驱动运动和周围组织上的相应力必须非常精确地进行控制和调整。此外，狭窄的手术通道导致来自周围组织的高热量输入，因此精确的温度相关致动器的时间是至关重要的。因此，人工耳蜗作为临床应用的一个主要例子，既需要非常精确地调整执行器的热机械行为以适应临床条件，也需要足够的策略来控制热流。拟议的研究项目将解决将细镍钛合金丝作为执行器元件应用于CI的具体实例的特殊挑战。其目的是为线状镍镍形状记忆致动器的尺寸确定提供可靠的知识。因此，外力对热滞的影响将通过对不同的线材样品进行系统的热机械表征来量化。这将通过研究热机械行为和临床前提条件(热：生理阈值、几何：解剖边界、机械：最大允许接触力)之间的相互依赖来补充。此外，将开发适用于OR的冷却方法，并将对主动加热(形状记忆效应的外部控制激活)进行实验研究。由此产生的表面温度将通过使用热像仪进行量化。这种面向应用的基础研究应该支持微型镍钛形状记忆致动器在医疗技术中的更广泛应用。