Reshaping at the touch of a button
Programmable materials change their properties in a controlled and reversible manner at the touch of a button. They adapt independently to new conditions. Areas of application include mattresses that prevent bedsores. In this case, the underlay deforms in such a way that the contact surface is large and the pressure on the body parts is reduced as a result. Researchers at the Fraunhofer Cluster of Excellence Programmable Materials CPM are developing such materials.
Numerous people around the world are affected by bedriddenness - whether due to illness, accident or old age. As they are often unable to move or turn on their own, bedsores can become very painful. With materials whose shape and mechanical properties can be changed programmably at any point, bedsores should be prevented in the future. For example, the hardness and stiffness of mattresses made of programmable materials could be adjusted in any area at the touch of a button. In addition, the base deforms automatically so that a high pressure in one place is distributed over a larger area. The bed automatically becomes softer and more elastic where it presses. In addition, caregivers can specifically adjust an ergonomic lying position to suit the patient.
Material plus microstructuring
Fraunhofer CPM researchers are developing materials for applications that require a specific change in stiffness or shape. But how can materials be programmed in the first place? "We basically have two adjusting screws: the basic material - in the case of mattresses thermoplastics, for other applications metallic alloys, also shape memory alloys - and in particular the microstructure," explains Heiko Andrä, from the Fraunhofer Institute for Industrial Mathematics ITWM, one of the core institutes of the Fraunhofer CPM. "The microstructure of the so-called metamaterials is composed of individual cells, which in turn consist of structural elements such as small beams and thin shells." While the size of the individual cells and their structural elements varies randomly in conventional cellular materials such as foams, it is also variable in programmable materials, but precisely determined - in other words, programmed. This programming is done, for example, in such a way that pressure at a certain position leads to desired changes in shape at other points of the mattress, in order to increase the contact surface and optimally support the body zones, for example.
Materials can also react to heat or moisture
"The programmable materials make it possible to adapt objects to the respective application or person and thus use things more multifunctionally than before. So they don't have to be replaced as often. This is particularly interesting against the background of resource consumption," says Franziska Wenz, from the Fraunhofer Institute for Mechanics of Materials IWM, also one of the core institutes of Fraunhofer CPM.
The path to application
A single material can replace complete systems of sensors, controllers and actuators. Fraunhofer CPM's goal is to reduce the complexity of systems and the use of resources by integrating the functions into the material. "We always have the industrial product in mind when developing the programmable materials, so we take series production and material durability into account, among other things," says Wenz. The first concrete pilot projects with industrial partners are also already underway.
