Manipulating and positioning small objects like cells or drops in flow is important in industry, biology, and medicine. The properties of these objects, including size, shape, and softness, often distinguish particles of interest from complex mixtures of many particles. However, current tools for measuring the deformability or softness of such objects are very limited. Often, these tools can analyze objects only slowly and in small numbers, so that large heterogeneous samples cannot be processed efficiently. Alternately, some tools do not allow only objects with certain properties to be selected and collected for further analysis. This study aims to understand how the mechanical properties of cell-like objects affects their behavior in flow in small channels and relate that behavior to the object's properties. Experiments and computer simulations will be used to examine cell-like objects undergoing flow. The results will be used to engineer a rapid, cellular deformability measurement tool that will also allow cell sorting. Such a device would benefit various biological and clinical applications, such as cancer diagnostics, stem cell research, and drug development.

This research will identify critical factors that enhance lateral migration of deformable microscale objects and will establish the fundamental understanding required to predict locations of deformable objects with known properties in channel flow. When microscale objects are injected into inertial microfluidics operating at finite particle-Reynolds-number, a balance of opposing, inertial lift forces acting on flowing microscale objects leads to unique lateral and vertical positions in a rectangular microchannel. An additional force also exists away from the channel walls in Poiseuille flow, which locates deformable objects closer to the channel center than rigid ones. By taking particle size into account, the location of objects in the channel can be used to infer their deformability. Also, the inherently high flow speeds at which inertial effects are relevant make inertial microfluidic systems ideal candidates for high-throughput deformability measurements. This study examines behaviors of droplets and vesicles in inertial flow, experimentally and computationally, to explain fundamental aspects of nonlinear particle migration. The experiments span a wide range of parameters and will identify dynamically significant regions of the parameter space, and the simulations will provide non-intrusive access to the flow fields, the balance of forces, and the stability of the flow state.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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Johns Hopkins University
United States
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