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In this paper, a shape memory alloy (SMA) based, multifunctional smart implant for improved bone fracture healing is presented. In contrast to conventionally used medical implants such as intramedullary nails or bone plates supporting a fractured bone in a passive way, the developed smart implant has on the one hand the ability to work as a common stabilizing implant. On the other hand, the smart implant has the property to stimulate the fracture to improve the bone healing process by controlled contracting micro movements. The smart implant consists of one mechanism to change the stiffness of the implant and one mechanism for the active stimulation purpose. Both actuator mechanisms are realized with the help of Nitinol SMA actuator wires, that are suitable for medical applications because of their biocompatibility. In addition to their actuator property the smart “self-sensing” ability of the SMA wires is used to control the actuator movements. This work focuses mainly on the development and the design of the smart implant prototype and the parts are produced via 3D rapid prototyping.

In this paper, a shape memory alloy (SMA) based handling system is presented. The gripping system consists of two different actuator systems based on SMA wires. The first one is a reconfigurable end-effector with four independent gripping arms. The second SMA actuator system is a bi-stable SMA actuated vacuum suction cup, of which one is mounted on each of the four arms of the end-effector. While the four independently adjustable gripping arms of the end-effector allow for an adaption to different workpiece geometries like a flat shaped workpiece or a round shaped, spherical workpiece, integrated SMA driven brake mechanisms enable an energy free position holding of the end-effector components. This means that an electric current is only required when the end-effector arms need to be rearranged. This results in a versatile, adaptive and energy-efficient handling system that can replace mostly pneumatically driven state-of-the-art systems in production and assembly industry. No manual adjustment of the gripping system or even exchanging is needed, if an assembly line switches between products with different work piece geometries as a result. The gripping unit is controlled using an external microcontroller and can be mounted on a robot for diverse handling purposes.

Material handling is a crucial part of manufacturing and assembly in industry. In state-of-the-art handling systems, robots use various end-effectors to grip and transport different shapes of workpieces. The exchange process of fitted end-effectors to appropriate workpieces, often requires to interrupt the manufacturing process. From the prospective of economic efficiency, there is an inherent benefit creating a reconfigurable end-effector that is able to adjust automatically to different workpiece geometries. In this work a novel end-effector prototype based on shape memory alloys (SMA’s) is developed and experimentally validated. The end-effector prototype has four arms with two SMA driven reconfigurable degrees of freedom (DOF’s) to allow gripping of different workpiece shapes and geometries. Each arm is rotatable by 90 degrees (1. DOF) and uses a counterweight to relieve the SMA wire. The tip of the arm is driven by a separate SMA in a 20 degree range and it has a special locking mechanism to hold different positions without any flowing current. The designs of the actuator constructions are presented and a prototype is produced via rapid-prototyping. Future work will include the characterization of the second DOF and controlling the positions of both DOF’s by using a PID controller based on the SMA self-sensing ability.

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