More comfortable bandages and flexible robotics

CAU materials scientist presents new structuring method for orthoses at the Hannover Messe 


hand with material
© Siekmann, Kiel University

The slat structure is created in the elastic material - here silicone - without chemical additives, so it remains biocompatible, i.e. well tolerated on bare skin.

When ligaments tear, bandages stabilise the affected joints and corsets help to correct spinal malpositions. As external devices, these so-called orthoses facilitate healing of damaged parts of the body - in contrast to prostheses, which replace them completely. However, hard components in the materials used often lead to painful pressure sores or bruises. Materials scientist Dr Michael Timmermann from Kiel University (CAU) has developed a biologically-inspired method of structuring elastic materials in such a way that they stiffen as soon as they are stretched. Afterwards, they return to their original state. This not only enables the production of more comfortable orthoses, but also of flexible components for soft robotics. Timmermann will be presenting his method at the Hannover Messe from 1 - 5 April at the CAU booth (Hall 2, C07).

Material for more flexible orthoses

Rigid orthoses can cause skin inflammation, are a pain to put on and take off, and are often heavy or don’t look very nice. "Especially with older patients, hard materials can often lead to the necessary treatment with orthoses being refused," explained Dr Michael Timmermann. In his opinion, so-called strain-stiffening materials could be significantly more comfortable to wear: "This type of elastic material is very flexible. If it is stretched beyond a certain point, it automatically stiffens and then behaves like a solid material," he added, to highlight the advantages. While it is true that such materials already exist, for example in special protective clothing, they have not yet been usable in orthoses. So far, they are too soft, stiffen only if they are stretched extremely quickly, or cannot return to their original state.

to hands
© Siekmann, Kiel University

Material scientist Dr.-Ing. Michael Timmermann from Kiel University wants to make orthoses more comfortable with specially structured elastic material

As part of his doctoral research under Professor Christine Selhuber-Unkel, head of the Biocompatible Nanomaterials working group at the Faculty of Engineering, Timmermann developed a method with which materials such as silicon can be structured so that they reversibly stiffen, independent of the speed of stretching. Through a special process, parallel slats are created in the material. If it is stretched, for example by being pulled apart, the slats get into contact with each other and the structure stiffens. By systematic variation of the slat form - in terms of length, thickness or distance from each other - the timing and degree of the stiffening can be precisely determined.


Inspired by cell behaviour

The process can be applied to all elastic materials, without the need for chemical additives such as lubricants, and without the properties being influenced by external factors such as humidity or temperature. "You can therefore choose the source material relatively freely, depending on what it will be used for afterwards," explained Timmermann.

The idea for developing the process comes from nature: in response to an external deformation, cells stiffen to a certain degree in order to protect themselves. Examples include cells in the walls of blood vessels, which stretch over and over again with each heartbeat. Cells consist of a specially-arranged internal structure, the cytoskeleton. This network of polymer fibers ensures the cell’s mechanical stability. If the cells are stretched over and over again, e.g. as part of the connective tissue, they adapt themselves by developing so-called stress fibres: proteins link the polymer filaments with each other, thereby stabilising them, and the cell stiffens. As part of his doctorate, Timmermann investigated how these processes inside the cell can be applied to the behaviour of elastic materials.

set up with material
© Siekmann, Kiel University

The experimental set-up stretches the sample up to 50.000 times. With its special characteristics the material could enable new movements in the field of soft-robotic.

Can also be used in flexible soft robotics

The structuring method for elastic materials could be used not only for more comfortable orthoses, but also in the field of soft robotics. This would allow not just the development of robotic systems based on the classic combination of rigid axles and joints, but also those which enable flexible movements, similar to the tentacles of an octopus. "For this, robotic systems must be able to move very freely, but at the same time very precisely. Here, our structure with its choice of flexible or rigid behaviour could make a useful contribution," hopes Timmermann.

Timmermann’s long-term goal is to develop software to determine the optimal combination of source material and geometric structure for every type of use of strain-stiffening materials. The result could be accurately produced using a 3D printing process. "However, initially I am looking for cooperation partners from the field of orthopaedics and industry, to jointly develop an orthosis which is more comfortable for patients," said the materials scientist. He is also interested in industrial partners for soft robotic applications. He has already been granted a patent for the material.

The project, which is titled "Strainstiff", is being funded by the European Research Council with a so-called Proof of Concept grant amounting to €150,000. These grants are to enable new findings from fundamental research to be put into practice faster.

Key facts:

What?   Lecture: “A strain-stiffening structure inspired by nature”  Exhibit: information stele with demonstrators
Who?   Dr.-Ing. Michael Timmermann
When?  The lecture will be held in English on Wednesday 3 April at 11am and 1:30pm.  The exhibit can be seen from 1 to 5 April.
Where? CAU booth C07 in Hall 2 “Research & Technology”,  Exhibition grounds Germany (entrance North 2), 30521 Hannover

CAU@Hannover Messe:

After 33 years, CEBIT and the Hannover Messe are joining forces. From 1 to 5 April, more than 6,000 exhibitors at the world's leading industrial trade show will present the latest developments in the fields of digitalisation, Industry 4.0 and research. Kiel University (CAU) is among these for the third time. In Hall 2 "Research & Technology", scientists from the true north will present 17 interdisciplinary and transdisciplinary research projects. In addition, 39 stage presentations will offer an over-the-shoulder perspective of current research projects on topics such as battery research, autonomous ship navigation or radar-based pollutant measurement procedures. Joint panel discussions with the Schleswig-Holstein Ministry of Education and Ministry of Economics, a parliamentary evening, and hands-on activities and experiments with the Kieler Forschungswerkstatt (Kiel Research Workshop) round off the offerings. Details can be found at



About the Priority Research Area "KiNSIS"

Details, which are only a millionth of a millimetre in size: this is what the priority research area "Kiel Nano, Surface and Interface Science – KiNSIS" at Kiel University has been working on. In the nano-cosmos, different laws prevail than in the macroscopic world - those of quantum physics. Through intensive, interdisciplinary cooperation between physics, chemistry, engineering and life sciences, the priority research area aims to understand the systems in this dimension and to implement the findings in an application-oriented manner. Molecular machines, innovative sensors, bionic materials, quantum computers, advanced therapies and much more could be the result. More information at


Information on funding through a Proof of Concept grant
With the Proof of Concept funding, innovative research ideas from projects already funded by the European Research Council (ERC) through an ERC grant should be tested for their applicability and be developed further for the market. The funding amount of €150,000 per project can be used for such things as market research, feasibility studies, or creating a business plan. With the Proof of Concept grant, the European Research Council aims to close a gap between fundamental research and the first phases of application.



Scientific Contact

Dr.-Ing. Michael Timmermann
Biocompatible Nanomaterials working group
Kiel University
+49 431 880-6286


Press Contact

Julia Siekmann
Science communication
Priority research area Kiel Nano, Surface and Interface Science (KiNSIS)