Interview: Programmable materials

Self-cleaning surfaces, programmable building envelopes and 3D-printed gears with integrated overload protection – these are the technologies being developed by the scientists at the Fraunhofer Cluster of Excellence Programmable Materials CPM. Dr. Thorsten Pretsch is deputy scientific coordinator of the cluster and head of the Synthesis and Polymer Technology Research Division at Fraunhofer IAP. In this interview, he talks about the technology of programmable materials and Fraunhofer IAP’s current research findings.

What is special about programmable materials?

Dr. Thorsten Pretsch: We have been developing programmable materials at Fraunhofer CPM since 2018 and the special thing is that we are able to tailor them in terms of their physical and functional properties, for example by selecting thermoplastic polyurethanes (TPUs) as the material base. We are also able to influence the functionality of programmable materials through the design of the external structure. For example, the shape change behavior can be largely determined by thermomechanical treatment. Another specific feature is that the material itself is not susceptible to failure as long as it has not aged significantly. No external control system, energy supply or electronic monitoring is required to activate the programmed material function. The material only reacts to changes in its environment if certain predefined boundary conditions are met, so-called “IF-THEN relationships” known from software language. The function is therefore inherent to the material. This opens up new possibilities over conventional mechatronic systems, which are made up of a large number of components.

Which projects are programmable materials suitable for?

Programmable materials can be of particular technical benefit in a wide range of industries. For example, in the case of a programmable building envelope, where air channels open or close depending on the ambient temperature. Here, foams that autonomously switch from insulating to air-permeable and back again offer particular benefits as an “intelligent” façade technology. Equally promising is the programmable transport behavior, for example, membranes used in water treatment which have specific detection groups that can switch autonomously. Another aspect is programmable friction. This involves self-lubricating bonded coatings with a predetermined release behavior that release lubricants from microcapsules. These are just a few of the key areas of research at Fraunhofer CPM.

What specific expertise does Fraunhofer IAP provide?

Admittedly, we cannot program every function into every material. We have to design the material first. TPUs, for example, are ideally suited for this. So, we start by tailoring the physical properties during polymer synthesis. Once we have synthesized the material, we use it to produce semi-finished products such as filaments or films. We can also extrude hoses and produce foams with our reactive foaming plant. And we have successively improved the manufacturing methods of TPUs with shape memory properties. Simplifying the production of such materials makes more and more new applications possible. Scaling production up to the ton scale is becoming increasingly important. This is demonstrated by the inquiries we receive from industrial partners. In order to meet such needs in the future, we at Fraunhofer IAP and our CPM partner, Fraunhofer ICT, have the PAZ pilot plant center in Schkopau at our disposal. I can, therefore, say that a lot is in our own hands in this respect.

What specific materials did you program in 2023?

We have been working on the further development of thermoplastic polyurethanes with shape memory properties and were able to show for the first time that it is possible to produce a thermally switchable gear wheel. Such gears are capable of maintaining the transmission of forces or temporarily interrupting them when the ambient temperature increases. This makes it possible to implement an overload protection function. TPU materials are generally known to be wear-resistant. We therefore see great potential here.

When I think of other functional materials – windproof or waterproof membranes, for example – what needs to happen for programmable materials to become just as popular?

The breakthrough for programmable materials will come as soon as the functional benefits are recognized by business leaders. This will accelerate the development of a wide range of applications. Our expertise ideally positions us to be able to support companies on this journey in a variety of ways in the coming years.

What steps are necessary for this?

In truth, cooperation with industry needs to be further expanded. Price is also not an insignificant factor. We have already been able to show in various contexts that the manufacturing costs for programmable materials are not significantly higher than for standard materials. Of course, product design must also be developed further so that the products are also socially appealing. We also need to inspire young people with our technologies and act as a magnet for young scientists in order to steadily advance the field. It is important to strengthen cooperation with other Fraunhofer institutes. The Fraunhofer Cluster CPM is the right network for this.

The circular economy, zero waste and decarbonization are among the trends of the future. Where do programmable materials stand?

We take into account the CO₂ footprint of the chemicals used in the process as early as the synthesis stage. In the cluster, we have already worked intensively on mechanically recycling 4D-printed objects. The programmable material was then able to be 4D printed again with its functional properties largely being retained. In the long term, we are pursuing the goal of enabling cross-industry recycling. The cycles can be interlinked. Thus, it is possible to reuse the material in the same application, as well as in a different one.

What are your goals for 2024?

The most important thing is to attract even more interest from industry. And to further expand the cooperation with our partners!

// The interview was conducted by Andrea Schneidewendt from the Strategy and Communication Department at Fraunhofer IAP

Fraunhofer’s research cluster “Programmable Materials CPM” is developing the scientific and technological foundation of materials that can replace entire highly functional systems thanks to their molecular structure and macroscopic design.

Go to the Fraunhofer CPM website