3D fluid flow manipulation on a microscopic scale*

Real-time control in a 3D flow chamber is essential for probing the force-free dynamics of swimming microorganisms. We present a novel device called a ``Stokes wind tunnel'' that permits direct control over a 3D fluidic chamber using independent pressure pumps that connect to a series of channels to a central chamber. Leveraging these basic components, we can create 3 orthogonal flow modes that act as a ``wind tunnel'' in which microorganisms become trapped in the center of the chamber under uniform Stokes flow due to a low Reynolds number condition. Our device also has the capacity to superimpose flow modes in order to form more complex flow patterns, such as shearing flow and extensional flow. These higher order flow patterns can be used to perturb microorganism dynamics and behavior in real-time through precise flow control. We additionally show the ability to perform high-throughput reconstruction of particle trajectory in 3D, which allows analysis of objects in the generated flow patterns. Our device represents the next generation in microfluidic control for probing fundamental microbial biomechanical systems.