ICMCS Seminar - i-Rheo: One Small Strain in Rheology, One Giant Leap in Viscoelastic Characterisation

Abstract

The frequency-dependent linear viscoelastic (LVE) properties of materials are essential for understanding their topological structure across different length scales. These properties are characterized by the complex shear modulus $G^{∗}(\omega)$, which provides insights into both the elastic and viscous nature of materials. Traditionally, $G^{∗}(\omega)$ is determined using oscillatory methods, which, although effective, are often time-consuming and restricted in frequency range. Over the past two decades, I have contributed to significant advancements in rheological characterization, addressing the limitations of traditional methods. My research has led to the development of innovative tools that extract LVE properties directly from time-domain data, eliminating the need for preconceived analytical models. These include i-Rheo, which enables broadband bulk rheology measurements from simple step-strain experiments [1]; i-Rheo-GT, designed for molecular dynamics simulations [2]; MOT, which leverages optical tweezers for microrheology [3]; and AFM2 , which adopts atomic force microscopy for microrheological measurements [4]. All these tools are built upon an analytical method for evaluating the Fourier transform of any generic time-dependent experimental function [5], enabling precise viscoelastic measurements across a broad frequency range. Recently, I have developed additional tools to further advance the rheological characterization of biological systems. OptoRheo integrates light sheet fluorescence microscopy with particle-tracking microrheology to investigate cell-matrix interactions, enabling precise rheological characterization of extracellular matrices surrounding live cells and advancing our understanding of drug transport in biological environments. [6]. Similarly, i-Rheo-optical assay combines rheology with optical microscopy to analyse the viscoelastic properties of multicellular spheroids, offering potential biomarkers for distinguishing between healthy and pathological tissues [7]. Furthermore, Optical Halo, a proof-of-concept microrheology technique, utilizes a ring-shaped Bessel beam created by optical tweezers, enabling viscoelastic measurements across an extended frequency spectrum, including low-frequency regimes that are typically challenging to access [8]. These innovative tools greatly expand the scope of rheological characterization, enabling the analysis of a wide range of materials—from synthetic polymers to complex biological systems—while providing deeper insights into their properties across a broad frequency spectrum. This advancement opens new avenues for research and applications in material science, mechanobiology, and beyond.

References

[1] Tassieri M. et al., Journal of Rheology, 60, 649 (2016).

[2] Tassieri M. et al., Macromolecules, 51, 14, 5055 (2018).

[3] Tassieri M. et al., New J. of Physics, 14, 115032 (2012).

[4] Chim Y. H. et al., Scientific Reports, 8, 14462 (2018).

[5] Evans R.M.L., et al., Phys. Rev. E, 80, 012501 (2009).

[6] Mendoca T. et al., Communications Biology, 6, 463 (2023).

[7] Ferraro R., et al., Materials Today Bio, 26, 101066 (2024).

[8] Ramírez J. et al., Micromachines, 15, 889 (2024).

Biography

Dr Manlio Tassieri is a Reader in the Division of Biomedical Engineering at the University of Glasgow and an internationally recognised expert in rheology and soft matter physics. He serves as a Council Member of the British Society of Rheology and is on the Executive Board of the European Society of Rheology (2023-2025). Additionally, he is a Member of the Institute of Physics, an Associate Member of the Institute of Non-Newtonian Fluid Mechanics, and an Editorial Board Member of Scientific Reports. Dr Tassieri earned a Laurea (MEng equivalent) in Chemical Engineering from the University of Naples “Federico II” in 2000, where he developed novel rheo-optical methods for measuring interfacial tension in polymer blends. After a brief period in industry, he pursued a PhD in Physics at the University of Leeds, specializing in microrheology of semi-flexible bio-polymers. In 2008, he joined the University of Glasgow as a Research Associate and later secured a prestigious Royal Academy of Engineering Research Fellowship (2010-2015). His research integrates microrheology with microfluidics, leading to groundbreaking advances in the characterization of complex fluids using optical tweezers. Dr Tassieri has published extensively in high-impact journals and has been invited to deliver keynote lectures and seminars at leading international conferences. His current research focuses on the rheological characterization of complex fluids and soft solids, with applications in biomedical engineering, polymer physics, and materials science. He is also actively advancing i-Rheo technology, simplifying rheological measurements across a broad range of materials.

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