Smart Manufacturing of Medical Devices for soft tissue fixation

我们将研究智能制造路线，在实现精确几何形状产品的同时，赋予聚合物和聚合物复合材料性能和功能可控增强。这些将与我们的行业合作伙伴（Zmith * Nephew， Wittman Battenfeld和Corbion Purac）选择的一系列潜在医疗设备相关，特别是那些利用形状记忆功能和表面特征控制的设备。最初的重点是软组织骨固定（如肩袖和前交叉韧带（ACL）修复）；长期目标包括骨折固定（包括髓间钉）和膝关节置换术。在高于其玻璃化转变点但低于其熔点的温度下对聚合物进行固相取向处理，提供了从低到非常高的聚合物分子取向范围的主要途径。这可以用来制造动态装置，使其在暴露于温度或潜在的体液时原位改变形状，从而使装置适应周围的骨骼拓扑结构。原型设备将由已知的可吸收或惰性聚合物、无机颗粒和合适的增塑剂制造，这些都有已知的临床病史。该装置将被编程为机械功能，然后降解以暴露已知的无机盐/支架，然后可用于促进成骨。对于医疗植入物，如组织固定，通常需要在适当的温度下进行恢复，以避免组织损伤（因此低于~50℃），或者（更具挑战性）由暴露于体液驱动，并在操作临床医生可接受的时间范围内发生（例如少于15秒），并在所需的时间范围内保持固定强度（生物可吸收物为数月，不可吸收物为永久）。除了固相取向加工路线之外，还可以使用一系列熔体加工技术来获得（通常）较低水平的取向，但在制造方面可能具有其他优势，包括净形状加工。研究计划探索了这些方法的新变体，包括：(a)微成型（单次特性梯度产品，或过度成型产品，以及表面特征控制），(b)微挤压（用于模具拉伸的精密预制件，或控制表面连续产品），以及(c)混合加工，例如新型注射拉伸工艺。需要解决的制造挑战包括(i)“智能制造”的总体目标，这里定义为通过加工有效控制性能水平，同时以经济的生产率实现形状记忆聚合物的精确几何形状产品；（ii）材料和添加剂的适用性，以及生物可吸收固定物复杂要求的可加工性；（iii）形成适合制造路线的起始材料，以及（iv）完善建模，以发展对固体和熔融阶段加工的理解，这对于发展对工艺和工艺设计的理解至关重要。

We will research smart manufacturing routes, which impart controllable enhancement of properties and functionality of polymers and polymer composites whilst achieving precision geometry products. These will be relevant to a range of potential medical devices, selected with our industry partners, Zmith * Nephew, Wittman Battenfeld and Corbion Purac, particularly those exploiting shape memory functionality and surface feature control. The initial focus is for soft tissue fixation to bone (e.g. rotator cuff and anterior cruciate ligament (ACL) repairs); longer-term goals include fixations for fracture (including intermedullary nails) and knee joint replacements.Solid phase orientation processing of polymers at temperatures above their glass transition point, but below their melting point, provides the major route to imparting a wide range of polymer molecular orientation, from low up to very high levels. This can be utilized to create dynamic devices which change shape in-situ on exposure to temperature or, potentially, body fluid, allowing the device to adapt to the surrounding bone topology. Protype devices will be manufactured from known resorbable or inert polymers, inorganic particles and suitable plasticisers all having known clinical history. The devices will be programmed to mechanically function and then degrade to expose known inorganic salts/scaffolds which can then be used to promote osteogenesis. In the case of medical implants such as tissue fixations, the recovery typically needs to take place at an appropriate temperature to avoid tissue damage (so less than ~50C), or (more challenging) be driven by exposure to body fluids, and to occur in an acceptable timescale to the operating clinicians (e.g. less than 15 s), and to retain fixation strength over required timescales (months for bioresorbables, permanent for non-resorbables). In addition to the solid phase orientation processing route, a range of melt processing techniques can be used to obtain (in general) lower levels of orientation but which may have other advantages in terms of manufacturing, including net shape processing. Novel variants of these are explored in the Research Programme,including: (a) micromoulding (single shot property gradient products, or over-moulded products, and surface feature control), (b) micro-extrusion (for precision preforms for die drawing, or controlled surface continuous products), and (c) hybrid processing, such as a novel injection-drawing process.Manufacturing challenges to be addressed include (i) the overall goal of 'Smart Manufacturing', defined here as the effective control of property levels through processing, simultaneous with achieving precision geometry products at economic production rates for shape memory polymers; (ii) materials and additives suitability, combined with processability for the complex requirements for bioresorbable fixations; (iii) formation of starting materials suited to manufacturing routes, and (iv) refined modelling for developed understanding of solid and melt phase processing, vital in developing understanding of the processes and process design.