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29.07.2025From Synthesis to Characterization: AFM as a Key Tool for Understanding New Materials
PhD Jordi Díaz, head of the nanometric techniques laboratory at CCiTUB, has collaborated on a multidisciplinary study alongside researchers from the University of Barcelona(Department of Materials Science and Physical Chemistry, Department of Inorganic and Organic Chemistry), the Faculty of Engineering at the University of Porto and the Institute of Robotics and Intelligent Systems at ETH Zurich.
The study, published in Advance Materials under the title “On‐the‐Fly Synthesis of Freestanding Spin‐Crossover Architectures With Tunable Magnetic Properties”, ”, presents a new 3D flow chemistry technique that enables the fabrication of spin-crossover (SCO)-based materials in a more efficient, homogeneous, and scalable way. These types of materials have great technological potential in various fields such as sensor and optical device manufacturing, among others, thanks to their ability to switch spin states in response to external stimuli like temperature, pressure, light, or magnetic fields. However, their difficult processability has limited their practical use, and traditional methods of polymer integration are complex and costly. This newly developed technique allows for unprecedented control in the direct fabrication of SCO composite materials, addressing key challenges such as processability, scalability, and cost.
At the nanometric techniques laboratory of CCiTUB, mechanical measurements of different samples were carried out using AFM microscopy and nanoindentation. Controlled indentations were performed using the AFM tip on the fibers of this material, thereby measuring their elastic response. The values obtained, in the range of megapascals (MPa), are typical of soft materials such as alginate hydrogel and are consistent with previous studies on similar materials.
Moreover, the indentation curve showed predominantly elastic behavior, with no permanent damage, suggesting that these fibers recover their shape after decompression. This supports their potential for applications requiring flexibility and mechanical reversibility.
The AFM study confirmed that the combination of elasticity (MPa) with spin transition enables the development of soft yet thermochromically functional materials, as achieved with the new technique presented.
Nanoindentation Technique
Atomic force microscopy, such as that used at CCiTUB, incorporates a specific nanoindentation module that allows for the measurement of mechanical properties of materials at the nanometric scale with high precision, requiring only a small sample amount. Through nanoindentation, parameters such as adhesion, deformation, or elastic modulus are obtained, which help determine how resistant a material is to permanent deformation or how capable it is of deforming elastically.