© Fraunhofer
Programmable shape changing and mechanics
Motivation
Methods for optimizing the topology of the outer form of components are firmly established in industrial practice. For the past few years, the importance of the so-called free material optimization and multi-scale methods has been increasing. Due to the rapid development of additive production technologies such as 3D printing, a designing process using them has in the meantime become possible, which optimizes the outer form parallel to the local internal (micro)structure of the material. This leads to materials whose internal structure fulfills the required system functions. To distinguish these mechanical metamaterials from normal mechanical structures, the applied load or the externally received signal does not dissolve the internal structure, but perceives the metamaterial as a quasi-homogeneous material. Under predefined loads, these materials show complex reactions and can therefore respond as a technical system.
Such programmable system materials that allow variation and switching of the mechanical properties by an external trigger (e.g. external load, temperature change) are preferable in many applications. It is practical to use adaptive materials particularly when there are severe spatial limitations such as in space travel or in case of special requirements as regards the individuality of a product.
Research topic
The development process of programmable materials requires a paradigm change, because the internal structure of the material and its properties must be adapted specifically to the application and not vice-versa. In order to design programmable materials, the internal structure of the materials must be predicted and produced at various locations in the material such that the different areas show certain elastic properties in combination, some of which are not available in nature, such as a negative Poisson’s ratio or an adjustable E-module. In many cases, the optimum design depends on the load history, which must thus be included in the optimization.
In the research topic of programmable deformation and mechanics, the cluster is researching the development of programmable materials based on mechanical unit cells. This includes the search for functional elementary structures, a complete understanding of their programming as well as the optimization of the production processes of unit cells.
Any time the development of mechanical metamaterials is begun, there is always the question of how a unit cell should look so that it can fulfill specific functions. The researchers of the topic initially start with the mechanism, e.g. torsion or contraction, which then implies a function. With the help of simulations or thought experiments, the researchers then consider which unit cell can transport the desired mechanism optimally. Another function of the topic is to design the search for such correlations in as systematic and automated a manner as possible. A challenge faced here is that it makes a lot of difference whether a single unit cell performs a function or whether a function is possible only by combining several or even different cells.
In addition to the research of Beul structures that can run through the body like a wave, the work on the topic of concrete metamaterials also extends to the wettability of surfaces. The objective here is to use adaptive wettability through microstructured surfaces to move fluids along a specific transport route.
A high-resolution 3D printer is used to print the unit cells on a polymer substrate. The cells should then unfold under an external force such that they expose a surface with greatly altered wettability. One possibility tested by the cluster is to design the structures in such a manner that a mechanical force deforms them such that previously hidden tips protrude out of the unit cell. The tips then minimize the contact area to the liquid, thus minimizing the adhesion forces of the surface against the cohesive forces in the liquid. The periodically applied structures could then be switched from hydrophilic to hydrophobic and ideally back by an external stimulus.
For applications, the researchers plan to structure the unit cells in the form of a gradient, e.g. with different wall thicknesses, so that the material could switch from hydrophilic to hydrophobic at different times in a chain. The liquids are then transported from one side to the other and a transport route is thus established. Obvious applications for the same would be for instance Lab-on-a-chip or filter systems.
The researchers were successful indesigning both of these conditions of the unit cells according to the requirements. The opened-out as well as the folded-in conditions were printed using a Nanoscrive 3D printer and partly coated. The reference measurements regarding the wettability of both the conditions resulted in a difference of the contact angle of approx. 50°, where the opened structures led to a super hydrophobic condition already known from the lotus blossom.
Challenges and perspective
The biggest challenge of the research topic of programmable deformation and mechanics is to find unit cells that perform the desired functions, with minimum possible effort. Even the next step, i.e. the comparison of simulation and reality in order to derive the material and its production process from a cell still presents the cluster with difficulties. Even if functional materials were found, their effects are often still relatively weak and must be reinforced.
The scaling of the materials also poses a challenge. The high resolution of modern additive methods in the three-digit nanometer range makes programmable structures possible. However, they require a correspondingly long time to produce macroscopic components in the centimeter range. The production of a surface itself on which a drop of water fits requires 10 whole days using the current method.
The opening of the closed structure is still not completely controllable in the unit cell structures for the adaptive wettability itself, because the carrier medium fails under load and the desired change thus does not happen in the unit cells. Stretchable polyethylene is said to be the current carrier medium, which is coated with an Indium-Tin-Oxide layer. As it turned out, the fragility of the coating is also transferred to polyethylene so that a thinner and more flexible coat provides a remedy in the next step. In addition, the current material combination is not as yet hydrophilic enough, which is to be dissolved by another separate coating of the closed structures.
For the next step, the participants of the research topic would like to use Shape-memory polymers as substrate. These perform a mechanical conversion in the shape at specific temperatures and thus enable thermal actuators instead of mechanical actuators. Their inherent temperature programming, their reversible form and high elasticity make them interesting for application in programmable materials in several ways. They would be predestined as applications for the cooling of microchips among other things, e.g. if a coolant is introduced from a certain temperature onwards or ventilation flaps open.
Moreover, polymer-based structures should be converted into ceramic materials by means of pyrolysis, because they mainly allow extended temperatures. The developed mechanical mechanisms should then be optimized on different scales and applied in macroscopic components.
Figure 1: On the left: Microdosing system as a demonstrator for a system consisting of a mechanical metamaterial.
Publications
Referred journals
Chalissery, Dilip; Schönfeld, Dennis; Walter, Mario; Shklyar, Inga; Andrä, Heiko; Schwörer, Christoph; Amann, Tobias; Weisheit, Linda; Pretsch, Thorsten; Highly shrinkable objects as obtained from 4D printing, Macromlecular Materials and Engineering 307/1 (2022) Art. 2100619, 12 pp.
Link
Participating institutes of the cluster: IAP, ITWM, IWM, IWU
Constante, Gissela; Apsite, Indra; Auerbach, Paul; Aland, Sebastian; Schönfeld, Dennis; Pretsch, Thorsten; Milkin, Pavel; Ivanov, Leonid; Smart mechanically tunable surfaces with shape memory behavior and wetting-programmable topography, ACS Applied Materials & Interfaces 14/17 (2022) 20208–20219
Participating institutes of the cluster: IAP
Uribe-Gomez, Juan; Schönfeld, Dennis; Posada-Murcia, Andrés; Roland, Michel-Manuel; Caspari, Anja; Synytska, Alla; Salehi, Sahar; Pretsch,Thorsten; Ionov, Leonid; Fibrous scaffolds for muscle tissue engineering based on Touch-Spun Poly(Ester-Urethane) Elastomer, Macromolecular Bioscience (2022) Art. 2100427, 12 pp.
Link
Participating institutes of the cluster: IAP
Schönfeld, Dennis; Chalissery, Dilip; Wenz, Franziska; Specht, Marius; Eberl, Chris; Pretsch, Thorsten; Actuating shape memory polymer for thermoresponsive soft robotic gripper and programmable materials, Molecules 26/3 (2021) Art. 522, 20 pp.
Link
Participating institutes of the cluster: IAP, IWM
Wenz, Franziska; Schmidt, Ingo; Leichner, Alexander; Lichti, Tobias; Baumann, Sascha; Andrä, Heiko; Eberl, Christoph; Designing shape morphing behavior through local programming of mechanical metamaterials, Advanced Materials 33/37 (2021) Art. 2008617, 8 pp.
Link
Participating institutes of the cluster: IWM, ICT, ITWM
Fischer, Sarah C. L.; Hillen, Leonie; Eberl, Chris; Mechanical metamaterials on the way from laboratory scale to industrial applications: Challenges for characterization and scalability, Materials 13/16 (2020) Art. 3605, 16 pp.
Link
Participating institutes of the cluster: IZFP, IWM
Specht, Marius; Berwind, Matthew; Eberl, Chris; Adaptive wettability of a programmable metasurface, Adaptive wettability of a programmable metasurface, Advanced Engineering Materials 23/2 (2020) Art. 2001037, 6 pp.
Link
Participating institutes of the cluster: IWM
Weisheit, Linda; Wenz, Franziska; Lichti, Tobias; Eckert, Medardus; Baumann, Sascha; Hübner, Christof; Eberl, Christoph; Andrä, Heiko, Domänenübergreifende Workflows zur effizienten Entwicklung Programmierbarer Materialien, ZWF Zeitschrift für wirtschaftlichen Fabrikbetrieb 115/7–8 (2020) 470-475
Link
Participating institutes of the cluster: IWU, IWM, ITWM, ICT
Non-referred journals
Steinchen, Peter; Kaal, William; Schwingungen optimieren, Lärmbekämpfung 16/01 (2021) 23-25
Participating institutes of the cluster: LBF
Chalissery, Dilip; Pretsch, Thorsten; Staub, Sarah; Kasack, Katharina; Andrä, Heiko; 3D-Druck von QR-Codes mit Formgedächtniseigenschaften, Der Druckspiegel 11-12 (2019) 34-37
Link
Participating institutes of the cluster: IAP, ITWM, IZI BB
Conference proceedings
Lichti, Tobias.; Andrä; Heiko; Leichner, Alexander; Müller, Ralf; Wenz, Franziska.; Optimal design of unit-cell based programmable materials, PAMM 20/1Special Issue: 91th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM); Kuhl, D.; Mesiter, A.; Ricoeur, A.; Wünsch, O. (Eds.); John Wiley & Sons, Inc., Hoboken, NJ, USA (2021) Art. e202000010, 2 pp.
Link
Participating institutes of the cluster: ITWM, IWM
Pretsch, Thorsten; Schönfeld, Dennis; Chalissery, Dillip; Walter, Moritz; Köbler, Jonathan; Andrä, Heiko; Wenz, Franziska; Eberl, Chris; Shape memory polymers in transition to programmable materials, in Proc. of Global Congress on Advances in Polymer Science & Nanotechnology 2021: Enlightening the Advancements in the fields of Polymer Science, Chemistry and Nanotechnology; Peers Alley Media, Vancouver BC, Canada (2021) 9
Participating institutes of the cluster: IAP, IWM, ITWM
Pretsch, Thorsten; Schönfeld, Dennis; Chalissery, Dillip; Walter, Moritz; Köbler, Jonathan; Andrä, Heiko; Wenz, Franziska; Eberl, Chris; Shape memory polymers in transition to programmable materials, in Proc. of 2nd Advanced Chemistry World Congress 2021 - Latest Global Innovations and Market Insights in Chemistry; Peers Alley Media, Vancouver BC, Canada (2021) 21
Participating institutes of the cluster: IAP, IWM, ITWM
Lectures
Pretsch, Thorsten
Additive manufacturing of thermoresponsive objects
Global Scientific Guild - Global Webinar on 3D Printing and Additive Modelling 2022
online, Indien 25.02.2022-26.02.2022
Pretsch, Thorsten
Funktionsintegration mit Additiver Fertigung
4. Virtuelles Werkstattgespräch "Additive Fertigung"
online, Deutschland; 19.01.2022
Link
Herter, Simon
Machine Learning as powerful tool to push the boundaries in classical material evaluation: An Introduction to machine learning from an applied science perspective
Adhesion Society Meeting 2021
online, USA; 22.02.2021-25.02.2021
Leichner, Alexander
A computational framework for the development of programmable materials based on unit cells and multiscale optimization
IX. International Conference on Coupled Problems in Science and Engineering 2021
virtuell, Chia Luga, Italien, 14.06.2021-16.06.2021
Leichner, Alexander
Optimal Design and Distribution of Unit Cells for Programmable Materials
14th Virtual Congress WCCM & ECCOMAS 2020
virtuell, Paris, Frankreich 11.01.2021-15.01.2021
Pretsch, Thorsten
Additive Fertigung mit Formgedächtnispolymeren
4. Status-Workshop des Leistungszentrums | Phase III KickOff zum Joint Lab BioF
online, Deutschland; 30.09.2021
Link
Wenz, Franziska
Programming shape morphing in Metamaterials
Engineering Mechanics International Conference EMI-IC 2021
virtuell, United Kingdom; 22.03.2021-24.03.2021
Eberl, Chris
Programmable (meta) materials as a framework to enable adaptivity and longevity in technical materials and systems
Gordon Research Conference on Multifunctional Materials and Structures GRC 2020
Ventura, CA, USA; 19.01.2020-24.01.2020
Fischer, Sarah
Characterization and scalability of mechanical metamaterials: Are they going to revolutionize materials in technical applications or will they stay a scientist’s dream forever?
Materials Science and Engineering Congress MSE 2020
online, Deutschland; 22.09.2020-25.09.2020
Kappe, Konstantin
Metallic Metamaterial with bistable behavior
DDMC2020, Fraunhofer Direct Digital Manufacturing Conference
online, Deutschland; 23.06.2020-23.06.2020
Lichti, Tobias
Multiscale modelling and optimization of complex unit-cell based materials for large deformations
Materials Science and Engineering Congress MSE 2020
Digital Conference, Deutschland; 22.09.2020-25.09.2020
Schönfeld, Dennis
Synthesis of a shape memory polymer for soft robotics
Materials Science and Engineering Congress MSE 2020
Digital Conference, Deutschland; 22.09.2020-25.09.2020
Wenz, Franziska
Developing programmable materials based on metamaterial unit cells
Materials Science and Engineering Congress MSE 2020
Digital Conference, Deutschland; 22.09.2020-25.09.2020
Pretsch, Thorsten
Programmierbare Polymere
Fraunhofer Symposium Netzwert 2019 »MOMENTUM«
München, Deutschland; 26.02.2019-27.02.2019
Wenz, Franziska
Developing programmable materials based on metamaterial unit cells
International Conference on Nonlinear Solid Mechanics
Rom, Italien; 16.09.2019-19.06.2019
PhD theses
Matthew Berwind
Albert-Ludwigs-Universität Freiburg im Breisgau
Materials design: the influence of structure, size and composition on material properties
Wissenschaftliche Preise und Auszeichnungen
Posterpreis WerkstoffWoche Dresden 2019
an PM1 für »Versuche zum Impact-Verhalten programmierbarer Dämpfungssysteme« ID 5
Dresden, Deutschland; 20.09.2019
Students' theses (Bachelor, Master, Diploma)
Akustische Spektroskopie zur Untersuchung von metallischen Metamaterialien (M)
Charakterisierung des Stoßverhaltens eines strömungsbasierten Dämpfungssystems als Modell für ein Metamaterial (B)
Classification of mechanical metamaterials and inverse unit cell design (M)
Entwicklung einer Charakterisierungsmethode für Rohmaterialien von pulverbasierten additiven Fertigungsverfahren (M)
Establishing two-way shape memory properties by 4D printing (M)
Mesoverkapselung von Phasenwechselmaterialien mittels SLA-3D-Druck – Potentiale und Grenzen des Druckverfahrens und Materialverträglichkeit (B)
Neuartige Formgedächtnispolymer-Materialien als thermische Stellglieder (M)
Visualization of fourth order tensor fields (M)
Optimization of Eddy current sensor for proximity and deformation detection (B)
Posters
Specht, Marius
Developing programmable adaptive wettability
Gordon Research Conference on Multifunctional Materials and Structures GRC 2020
Ventura, CA, USA, 19.01.2020-24.01.2020
Wenz, Franziska
A programmable mechanical metamaterial with designed strain-dependent poisson's ratio
Gordon Research Conference on Multifunctional Materials and Structures GRC 2020
Ventura, CA, USA, 19.01.2020-24.01.2020