Abstract:Suspensions of swimming microorganisms play important roles in biology, medicine, and engineering. To predict and control the flow field of such suspensions, an understanding of their rheological properties is required. In this background, the suspension rheology of various types of microorganisms has been investigated intensively. Research has shown that some microorganisms, such as ciliates, deform when a strong force is exerted on their bodies. However, the effect of cell deformability on suspension rheolog… Show more
“…The role of body deformability on active suspensions and their effective rheology remains a generically open area of inquiry, but simulations have revealed that the sign of the effective medium's second normal stress differences depends on body stiffness (224). Other non-Newtonian features due to active suspensions like viscoelasticity (11,220,225,226) and yield-stress behavior (227,228) have also been predicted.…”
We review the literature on swimming in complex fluids. A classification is proposed by comparing the length and timescales of a swimmer with those of nearby obstacles, interpreted broadly, extending from rigid or soft confining boundaries to molecules that confer the bulk fluid with complex stresses. A third dimension in the classification is the concentration of swimmers, which incorporates fluids whose complexity arises purely by the collective motion of swimming organisms. For each of the eight system classes that we identify, we provide a background and describe modern research findings. Although some classes have seen a great deal of attention for decades, others remain uncharted waters still open and awaiting exploration. Expected final online publication date for the Annual Review of Condensed Matter Physics, Volume 14 is March 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
“…The role of body deformability on active suspensions and their effective rheology remains a generically open area of inquiry, but simulations have revealed that the sign of the effective medium's second normal stress differences depends on body stiffness (224). Other non-Newtonian features due to active suspensions like viscoelasticity (11,220,225,226) and yield-stress behavior (227,228) have also been predicted.…”
We review the literature on swimming in complex fluids. A classification is proposed by comparing the length and timescales of a swimmer with those of nearby obstacles, interpreted broadly, extending from rigid or soft confining boundaries to molecules that confer the bulk fluid with complex stresses. A third dimension in the classification is the concentration of swimmers, which incorporates fluids whose complexity arises purely by the collective motion of swimming organisms. For each of the eight system classes that we identify, we provide a background and describe modern research findings. Although some classes have seen a great deal of attention for decades, others remain uncharted waters still open and awaiting exploration. Expected final online publication date for the Annual Review of Condensed Matter Physics, Volume 14 is March 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
“…The role of body deformability on active suspensions and their effective rheology remains a generically open area of inquiry, but simulations have revealed that the sign of the effective medium's second normal stress differences depends on body stiffness (222). Other non-Newtonian features due to active suspensions like viscoelasticity (11,218,223,224), and yield-stress behavior (225,226) have also been predicted.…”
We review the literature on swimming in complex fluids. A classification is proposed by comparing the length and time scales of a swimmer with those of nearby obstacles, interpreted broadly, extending from rigid or soft confining boundaries to molecules which confer the bulk fluid with complex stresses. A third dimension in the classification is the concentration of swimmers, which incorporates fluids whose complexity arises purely by the collective motion of swimming organisms. For each of the eight system classes which we identify we provide a background and describe modern research findings. While some classes have seen a great deal of attention for decades, others remain uncharted waters still open and awaiting exploration.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.