Soft hydraulics: from Newtonian to complex fluid flows through compliant conduits

Abstract

Microfluidic devices manufactured from soft polymeric materials have emerged as a paradigm for cheap, disposable and easy-to-prototype fluidic platforms for integrating chemical and biological assays and analyses. The interplay between the flow forces and the inherently compliant conduits of such microfluidic devices requires careful consideration. While mechanical compliance was initially a side-effect of the manufacturing process and materials used, compliance has now become a paradigm, enabling new approaches to microrheological measurements, new modalities of micromixing, and improved sieving of micro- and nano-particles, to name a few applications. This topical review provides an introduction to the physics of these systems. Specifically, the goal of this review is to summarize the recent progress towards a mechanistic understanding of the interaction between non-Newtonian (complex) fluid flows and their deformable confining boundaries. In this context, key experimental results and relevant applications are also explored, hand-in-hand with the fundamental principles for their physics-based modeling. The key topics covered include shear-dependent viscosity of non-Newtonian fluids, hydrodynamic pressure gradients during flow, the elastic response (deformation and bulging) of soft conduits due to flow within, the effect of cross-sectional conduit geometry on the resulting fluid--structure interaction, and key dimensionless groups describing the coupled physics. Open problems and future directions in this nascent field of soft hydraulics, at the intersection of non-Newtonian fluid mechanics, soft matter physics, and microfluidics, are noted.

32 pages, 14 figures, 267 references; invited topical review to appear in J. Phys.: Condens. Matter; v2: minor updates/correct typos

References in corpus (8)

• The hydrodynamics of swimming microorganisms
• Reexamination of Hagen-Poiseuille flow: shape-dependence of the hydraulic resistance in microchannels
• Passive control of viscous flow via elastic snap-through
• Analytical solutions for the flow of Carreau and Cross fluids in circular pipes and thin slits
• Braess's paradox and programmable behaviour in microfluidic networks
• Reduced models of unidirectional flows in compliant rectangular ducts at finite Reynolds number
• Steady streaming viscometry of Newtonian liquids in microfluidic devices
• Dispersion control in pressure-driven flow through bowed rectangular microchannels

Cited by in corpus (12)

• Non-Newtonian fluid-structure interaction: Flow of a viscoelastic Oldroyd-B fluid in a deformable channel
• Oscillatory flows in compliant conduits at arbitrary Womersley number
• Flow rate-pressure drop relations for shear-thinning fluids in deformable configurations: theory and experiments
• Reduced modelling and global instability of finite-Reynolds-number flow in compliant rectangular channels
• Flow rate--pressure drop relations for new configurations of slender compliant tubes arising in microfluidics experiments
• Elasto-inertial rectification of oscillatory flow in an elastic tube
• Pressure drop reduction due to coupling between shear-thinning fluid flow and a weakly deformable channel wall: A reciprocal theorem approach
• Experimental investigation of the flow rate--pressure drop relation of a viscoelastic Boger fluid in a deformable channel
• Fluid-induced snap-through instability of spherical shells
• Emergent oscillations and chaos in non-compliant microfluidic networks
• Flow rate-pressure drop relation for deformable channels via fluidic and elastic reciprocal theorems
• Theory and simulation of elastoinertial rectification of oscillatory flows in two-dimensional deformable rectangular channels