Continuum robots are inspired by biological trunks, snakes and tentacles. Unlike conventional robot manipulators, there are no rigid structures or joints. Advantageous is the ease of miniaturization combined with high dexterity, since limiting components such as bearings or gears can be omitted. Most currently used actuation elements in continuum robots require a large drive unit with electric motors or similar mechanisms. Contrarily, shape memory alloys (SMAs) can be integrated into the actual robot. The actuation is realized by applying current to the wires, which eliminates the need of an additional outside drive unit. In the presented study, SMA actuator wires are used in variously scaled continuum robots. Diameters vary from 1 to 60 mm and the lengths of the SMA driven tentacles range from 75 to 220 mm. The SMAs are arranged on an annulus in a defined distance to the neutral fiber, whereby the used cores vary from superelastic NiTi rods to complex structures and also function as restoring unit. After outlining the theoretical basics for the design of an SMA actuated continuum robot, the design process is demonstrated exemplarily using a guidewire for cardiac catheterizations. Results regarding dynamics and bending angle are shown for the presented guidewire.

In industrial applications, rotatory motions and torques are often needed. State-of-the-art actuators are based on either combustion engines, electro-motors, hydraulic, or pneumatic machines. The main disadvantages are the construction space, the high weight, and a large amount of needed peripheral devices. To overcome these limitations, compact and light-weight actuator systems can be built by using shape memory alloys (SMAs), which are known for their superior energy density. In this paper, the development of a scalable bi-directional rotational actuator based on SMA wires is presented. The scalability was based on a modular design, which allowed the actuator to be adapted to various application specifications by customizing the rotational angle and the output torque. On the mechanical side, each module enabled a small rotatory motion, which added up to the total angle of the actuator. The SMA wires were arranged in an agonist-antagonist configuration to provide active rotation in both directions. The presented prototype achieved a total rotation of 100 • . The modularity of the mechanical concept is also reflected in the electronics, which is discussed in this paper as well. This consideration allows the electronics to be adapted to the mechanics with minimal changes. As a result, a prototype, including the presented mechanical and electronic design, is reported in this study.

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adem.202200205.

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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.