Paper Number
MR20   Keynote                         My Program 

Session
Microrheology, Microfluidics and Nanofluidics

Title
Microrheometry with deformable microchannels

Presentation Date and Time
17 April 2026 (Friday) 11:50

Track / Room
Track 5 / Room C

Authors (Click on name to view author profile)

1. Christov, Ivan C. (Purdue University, School of Mechanical Engineering)

Author and Affiliation Lines (in printed abstract book)
Ivan C. Christov
School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907

Speaker / Presenter 
Christov, Ivan C.

Text of Abstract
A decade ago, Del Giudice et al. asked, "Is microrheometry affected by channel deformation?" (Biomicrofluidics 10, 043501, 2016). The answer is: it depends. In the years since, we have developed a complete understanding of the flow-induced deformation of fluidic conduits by low-Reynolds-number viscous flows (J. Phys.: Condens. Matter 34, 063001, 2022). In this talk, I will present our latest comprehensive experimental-theoretical studies on complex fluids in 3D deformable microchannels fabricated from PDMS, focusing on steady pressure-driven flows. Specifically, I will show how flow-induced deformation curves the streamlines of a weakly viscoelastic (small Deborah number) flow, reducing the pressure drop by an amount well predicted by theory (J. Non-Newton. Fluid Mech. 313, 104990, 2023; Phys. Rev. Applied 24, 034001, 2025). This observation may provide a new way to measure the relaxation time of constant-shear-viscosity (i.e., Boger) fluids modeled by the Oldroyd-B constitutive equations by exploiting microchannel deformation. Meanwhile, for inelastic fluids, I will demonstrate that their flows in deformable channels fall in the large-Carreau-number regime and are thus well captured by theory based on the power-law viscosity model (J. Non-Newton. Fluid Mech. 264, 62-72, 2019; Phys. Rev. Fluids 9, 043302, 2024). In particular, I will highlight the critical importance of the lateral dimension of the shallow, wide microchannels fabricated by soft lithography. The lateral dimension of 3D channels with a thin deformable top wall allows us to "tune" the flow-induced deformation and overall pressure drop, revealing rheological features of the complex fluids within. In summary, the compliance of deformable 3D microchannels offers new possibilities for microrheometry, leveraging experimentally validated predictive theories for the pressure drop of model complex fluids in such configurations. This talk presents results from productive joint work with E. Boyko, J. Feng, and S.G. Chun.