Mechanical meta-material and tribology (MetaTrib) project: Structure- dominated/controlled frictional behaviour.

Project Information

METATRIB

Grant agreement ID: 101065669

DOI

10.3030/101065669

Project closed

EC signature date 14 July 2022

Start date 1 August 2022

End date 31 July 2024

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 214 934,40

Coordinated by

AARHUS UNIVERSITET
Denmark

Periodic Reporting for period 1 - METATRIB (Mechanical meta-material and tribology (MetaTrib) project: Structure- dominated/controlled frictional behaviour.)

Reporting period: 2022-08-01 to 2024-07-31

Summary of the context and overall objectives of the project

The project addresses a critical challenge in the field of materials science and engineering, focusing on understanding and controlling friction in soft materials, particularly at the level of the microscopic contact points, or asperities. The study of friction in soft materials is essential due to the increasing use of such materials in various advanced applications, including robotics, automotive, and aerospace sectors. As industries push the boundaries of innovation, there is a growing need for materials that are not only high-performing but also sustainable, adaptable, and capable of meeting the demands of emerging technologies.
The main objective of the project was to investigate how the mechanical properties of soft materials—specifically their ability to deform under pressure and their response to friction—can be controlled and manipulated. This understanding can lead to the development of more efficient and durable materials, particularly for soft robotics, which is a rapidly growing field. By gaining insight into how elasticity and friction interact in soft materials, the project aimed to enhance the design of mechanical systems that require controlled frictional behavior, such as soft actuators, sensors, and other flexible devices used in next-generation technologies.
The project also explored the multi-asperity contact of these materials, addressing how internal microstructures, such as particle arrangements and elasticity, influence friction at a larger scale. This is crucial for optimizing the design and functionality of complex mechanical systems, where micro-scale friction can impact the overall performance of devices. Additionally, the research aimed to develop a deeper understanding of how local frictional effects can either enhance or suppress certain phenomena, such as instability and deformation, that occur in soft materials under various conditions.
This project’s potential impact lies in its contribution to sustainable innovation and the future competitiveness of Europe’s industrial sectors. It seeks to directly contribute to the European Green Deal, which emphasizes the development of sustainable technologies, and to the EU Digital Strategy, which highlights the need for innovation in digital and advanced manufacturing technologies. The insights gained from this project can help design materials that improve the performance and longevity of soft robotics, while simultaneously reducing waste and energy consumption, leading to more environmentally friendly production methods.
Furthermore, this project supports EU policies on advanced manufacturing, sustainability, and innovative technologies, aligning with efforts to develop new standards for cutting-edge industries. By enabling a better understanding of friction and material behavior, this research could directly influence the development of new regulations and standards in the fields of robotics and smart manufacturing, enhancing Europe's leadership in these sectors.
In the long term, the project is expected to contribute to the advancement of smart and sustainable industrial technologies, creating solutions that address both economic and environmental challenges. These results can help European industries maintain their competitive edge in the global market, promote innovation in the design of adaptive, responsive, and energy-efficient mechanical systems.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The project focused on understanding friction in soft materials, specifically the role of elasticity and internal microstructures at the asperity level. Key activities and achievements include:
1. Friction-Induced Shell Instability
Experiments showed that friction significantly impacts the stability of soft materials, revealing new insights into shell instability and challenging existing theories. This discovery provides a foundation for designing materials where friction can control stability.
2. Development of Experimental Setup
An innovative experimental setup was created to measure friction at the asperity level. This setup enabled high-precision analysis of local friction, material deformation, and instability, providing valuable data on how microstructure and surface roughness influence friction.
3. Advancements in Tribological Theory
The project resulted in three major findings:
◦ Force-contact area deviates from the Hertzian solution in intermediate regimes.
◦ A non-monotonic relationship between contact area and force is observed in post-buckling regimes.
◦ Hysteresis during unloading is influenced by the coefficient of friction, providing new insights into frictional behavior.
4. Collaborative Research
A secondment at the University of Edinburgh led to collaboration on material design and computational modeling of mechanical metamaterials, extending the project's scope and deepening the understanding of microstructural influence on friction.
Main Achievements:
• Key discoveries in frictional behavior and shell instability.
• Development of a new experimental setup for studying friction at the asperity level.
• Contributions to tribological theory, advancing understanding of soft material behavior under friction.
Overall Outcome:
These advances open new perspectives for designing materials for applications such as soft robotics, adaptive materials, and sustainable manufacturing systems by providing critical insights into the design of materials more resistant to wear and friction, as well as offering valuable understanding of frictional instability. The results obtained have the potential to transform future research in these areas, providing a solid foundation for the development of more efficient and sustainable technologies.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The project has provided several innovative insights that push the boundaries of current understanding in the field of friction and tribology, particularly in soft materials. By focusing on the relationship between elasticity and friction at the asperity level and investigating how internal microstructure influences tribological properties at the multi-asperity level, the research has resulted in several key breakthroughs. These findings not only contribute to advancing scientific knowledge but also have the potential to drive innovation in various sectors, including soft robotics, material design, and sustainable manufacturing.
Key Results Beyond the State of the Art:
1. New Insights into Shell Instability:
The project revealed a novel understanding of how friction can either stabilize or destabilize the shell structure of soft materials. This contradicts previous assumptions where friction was generally thought to only contribute to instability. The discovery that friction can have both stabilizing and destabilizing effects opens new possibilities for designing soft materials with controlled properties, such as in soft robotics and adaptive structures.
2. Elasticity-Controlled Friction:
A significant breakthrough of this project was the discovery that elasticity can be used to control friction at the asperity level. By altering the elastic properties of materials, frictional behavior can be tailored to optimize performance in specific applications. This finding has the potential to revolutionize industries that rely on precision material interactions, including automotive, aerospace, and robotics.
3. Experimental Setup for Tribological Measurements:
The development of a new experimental setup for high-precision measurement of friction at the asperity level is another major contribution beyond the state of the art. This setup allows for detailed exploration of the contact mechanics between soft materials, enabling more accurate simulations and real-world applications. The experimental setup can be applied to a wide range of materials and provides a unique tool for researchers working in the field of tribology and soft matter.
4. Hysteresis in Frictional Behavior:
The identification of hysteresis in the frictional behavior of soft materials during unloading, with a maximum at a critical coefficient of friction, is another important contribution. This discovery challenges existing models of friction and introduces the need for further research to understand the underlying mechanisms. The potential impact lies in the ability to design materials with more predictable frictional behavior, which is crucial for the development of adaptive materials and self-healing systems.
5. Multidisciplinary Approach to Material Design:
Through collaboration with leading experts in mechanical metamaterials at the University of Edinburgh, the project has provided a multidisciplinary approach to material design. The combination of experimental data and computational models for large-scale mechanical structures paves the way for future research into the design of complex, adaptive materials with tailored frictional properties.
Potential Impacts and Needs for Further Uptake:
While the project has significantly advanced the scientific understanding of friction in soft materials, further research is needed to explore how these insights can be translated into practical applications. This includes developing new material prototypes based on the discovered principles and testing them in real-world scenarios. Additionally, further work is required to refine the computational models developed during the project and to expand them to include more complex geometries and material systems.
The potential for commercialization of these results is high, particularly in industries such as soft robotics, medical devices, and precision manufacturing. However, to facilitate commercialization, access to markets and finance is essential. Establishing partnerships with industry players, securing venture capital, and engaging with innovation networks will be key to translating the research into viable products.

(a) Robotic arm using a meta-material to move an object, (b) standard contact, (c) advance system