Alladi Ramakrishnan Hall

Dissipation and recovery in collagen fibrils: modelling and simulations

Amir Suhail

The Institute of Mathematical Sciences (IMSc)

In hybrid mode
zoom.us/j/95038155052

Meeting ID: 950 3815 5052
Passcode: 272075

(Thesis talk): Collagen, as the most abundant protein in the human body, plays a crucial role in providing mechanical support, strength, flexibility, and mobility to vital tissues like tendons, bones, and skin. When subjected to cyclic loading, collagen fibrils exhibit intriguing hysteretic behaviour with partial recovery on relaxation, as well as increased strength and toughness after cycling. In the thesis, we aim to comprehensively model and understand the mechanical response of single collagen fibrils under cyclic loading. In the first part of the study, a minimal kinetic model is developed, which incorporates reversible sacrificial bonds with hidden loops in collagen fibrils. This model effectively explains and qualitatively reproduces experimental features, including moving hysteresis loops, the time evolution of residual strain, and recovery on relaxation. The second part of the thesis explores the problem from a microscopic perspective, building upon existing molecular dynamics models. To account for experimental observations of recovery during cyclic loading, the study incorporates the reformation of cross-links, which contributes to recovery through relaxation and increased strength. Notably, the approach to the steady state during cyclic loading is found to be governed by a characteristic cycle number for crucial quantities such as residual strain, peak stress, and energy dissipation. This characteristic cycle number demonstrates potential applicability for comparing fibril responses across different animals, ages, stages of disease, and other factors. Our work sheds light on the fundamental mechanical behaviour of collagen fibrils under cyclic loading, offering insights that could contribute to advancements in biomaterials and medical applications, and in understanding tissue mechanics.