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Bangalore, India – Researchers at the Raman Research Institute (RRI), an autonomous institute under the Department of Science and Technology (DST), have made a significant breakthrough in material science. They have developed a method to accurately predict the exact time of the emergence of the first crack in aged clay and blood. This finding has promising implications for diagnosing conditions like anaemia, aiding in forensic investigations, and improving the quality of paints used for coatings.
The study, published in the journal Physics of Fluids, explored the relationship between the time of the first crack’s emergence, fracture energy (the sum of plastic dissipation and stored surface energy), and the elasticity of drying clay samples. Researchers used the theory of linear poroelasticity to estimate the stress at the surface of the drying sample at the time of crack onset. Linear poroelasticity describes the diffusion of water (or any mobile species) in the pores of a saturated elastic gel.
The team equated this stress with Griffith’s criterion, which states that a crack will grow when the energy released during propagation is equal to or greater than the energy required to create a new crack surface. The relation obtained was validated through a series of experiments and was also applicable to other colloidal materials, such as silica gels.
“This correlation can be useful while optimising material design during product development. We can apply this knowledge and suggest tweaking in the material composition at the time of manufacturing industry-grade paints and coatings so that they can have better crack resistance and improve product quality,” said Professor Ranjini Bandyopadhyay, head of the RheoDLS lab and faculty at the Soft Condensed Matter group at RRI.
In the study, the team used Laponite, a synthetic clay with disk-shaped particles sized 25-30 nanometres (nm) and one nm in thickness. They created multiple Laponite samples with varying elasticities, dried at temperatures ranging from 35 to 50 degrees Celsius in petri dishes. The samples took 18-24 hours to dry completely, during which the rate of evaporation and elasticity were measured. As water evaporated, the particles rearranged, and stresses developed on the material’s surface.
Higher sample elasticity indicated a better ability of the sample to deform under stress. Cracks began developing at the outer walls of the petri dish and progressed inward, forming networks of cracks as the sample aged.
This study’s insights hold potential for various applications, from optimizing industrial products to enhancing medical diagnostics and forensic methods. By understanding the mechanisms behind crack formation, researchers can better design materials and improve their practical applications in diverse fields.
