Shape Memory Alloys - Application Development

After tendon injuries or a stroke, the mobility of the hands can be severely restricted. Exoskeletons, which are attached to the hand like a second skeleton, are increasingly being used in therapy. They enable targeted, slow movement of the wrist and fingers. For successful therapy, it is crucial that the exoskeleton is individually tailored to the patient's hand and meets key requirements such as low weight and compact design.

Connectors for electric vehicles are important components in DC fast charging. However, charging capacities above 150 kW cause thermal problems due to high contact resistance between the charging cable and the vehicle connection. One way to reduce contact resistance is to increase the normal contact force between the contact socket and pin, for example, using FGL-based actuator systems.

Drive systems based on shape memory alloys (SMA) have been steadily conquering new fields of application for several years now. A current example of the use of these lightweight actuators is a drone, in which the actuators developed ensure reliable locking of the battery tray.

Micro-irrigation or drip irrigation systems have become established in commercial agriculture. However, on steep slopes (e.g., in viticulture), the amount of water delivered varies considerably. Uniform irrigation is therefore not possible with this principle. An SMA-based valve provides a remedy.

Wire-based SMA actuators are well established in industrial applications, but are limited to low forces (N range) with small strokes (mm range). There is also demand for compact SMA actuators with higher forces (kN range) and small strokes (mm range). The HochPerForm project is researching technologies that enable fast-switching SMA actuators in the high-load range (kN).

In the “ProAuSter” project, Hahn-Schickard and Fraunhofer IWU are working together on innovative process technologies for the heterogeneous integration of shape memory alloys (SMA) into silicon-based microsystems. The technologies developed will be tested using the example of a sterilization cycle counter. 

Compared to steel and aluminum, fiber composites and plastics are highly elastic and stretchable. Sensors that are equally elastic are therefore required to measure strain on components made from these materials. Conventional strain gauges are not suitable for this purpose, as they fail due to fatigue at high cycle counts. Elastic SMA sensors, which can be easily integrated into fiber composites and plastics, are suitable for cyclic measurements and mobile applications. 

The SMA incense rocket, which was developed in collaboration between Fraunhofer IWU and Seiffen-based craftsman Markus Füchtner, uses the heat from a standard incense cone to activate its shape memory function. After a few minutes, the rocket capsule “explodes.” A mischievously smiling “Nutcracker Wilhelm” can then emerge from the rocket. It is no coincidence that he is in a rocket, as he has already been to the ISS.