PAIR Distinguished Lecture by Prof. Julia M YEOMANS (18 Dec 2025)

When physics meets biology: Prof. Yeomans of Oxford unravels how mechanical forces sculpt tissue shape

Prof. Julia M. YEOMANS of the University of Oxford, UK, delivered a PAIR Distinguished Lecture titled “Active Matter meets mechanobiology: Evading the decay to equilibrium” on 18 December 2025. The event drew over 70 in-person participants and an online audience exceeding 15,500 across various social media platforms.

Prof. Yeomans commenced her presentation by introducing the concept of active systems—systems pushed out of thermodynamic equilibrium by energy at the particle level. This framework is particularly valuable for understanding biological phenomena such as biomechanics and self-assembly, and supports the design of novel micro-engines and internally driven microchannel flows. These examples underscore the broader principles of non-equilibrium statistical physics.

Building on this foundation, Prof. Yeomans explored the physics of active matter and its implications for mechanobiology and developmental biology. She discussed how active matter provides a new perspective on the organisation and behaviour of living systems, illustrating this with examples including the intricate patterns that emerge in bacterial colonies and the dynamics of dense active nematics, such as microtubules propelled by motor proteins. In these systems, far-field flow patterns exhibit nematic symmetry—where liquid crystal molecules align in the same general direction. Gradients in the magnitude or direction of nematic order—essentially, misalignments of molecules across a surface—create regions with different alignment directions, making them susceptible to splay distortions that lead to bending or curving deformations in tissues. Notably, active turbulence within these systems can be suppressed by confinement, and in deformable nematic systems, the force axis is not necessarily aligned with the shape axis—adding to the complexity of their behaviour.

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Prof. Yeomans also addressed the relevance of these principles to medical science, specifically the distribution of lesions in invasive breast cancer. By comparing histological slides with computational simulations, she presented evidence suggesting that cluster motility, rather than cell proliferation, is the primary driver of the distinctive patterns seen in malignant breast cancer. This insight has significant implications for understanding tumour progression and could inform future therapeutic strategies.

Furthermore, she examined the dynamics of epithelial cells, which can be modelled as deformable active nematics. In addressing such systems, it is essential to develop theoretical approaches that decouple cellular shape from mechanical stress to provide a more accurate representation of tissue behaviour and development.

In conclusion, Prof. Yeomans emphasised the importance of interdisciplinary research at the intersection of physics, biology and engineering, noting that advances in the study of active matter are continually reshaping our understanding of living systems and their complex behaviours.

Following the presentation was a lively question-and-answer session moderated by Prof. WANG Liqiu, Member of Research Institute for Sports Science and Technology and Research Centre of Textiles for Future Fashion, Otto Poon Charitable Foundation Professor in Smart and Sustainable Energy and Chair Professor of Thermal-Fluid and Energy Engineering in the Department of Mechanical Engineering. Prof. Yeomans led a productive discussion that engaged both the on-site and online audiences.