Researchers from the University of Illinois have created tiny gentle hands that can handle soft, delicate items at a microscopic scale. The new device is called a Stokes trap. The Stokes trap allows tiny soft particles to be handled with controlled fluid flows, allowing researchers to test the physical limits of soft particles. University of Illinois researchers have honed a technique called the Stokes trap, which can handle and test the physical limits of tiny, soft particles using only fluid flow. From left, undergraduate student Channing Richter, professor Charles Schroeder and graduate student Dinesh Kumar. (Source: L. Brian Stauffer)It makes it simple to control the orientation and trajectories of all shapes of particles.

The team used the Stokes trap to study dynamics in vesicles. Vesicles are squishy fluid-filled particles that are important in biological systems. The team used the Stokes trap to understand the dynamics of lipid vesicles when they are not in their equilibrium state. They wanted to know what happens when the particles are pulled by a strong flow and how they act when they deform. This has implications for the long-term stability and workability of the vesicles. The Stokes trap was used to deform the vesicles and measure the changes.

The results proved that when the vesicles are deformed, they stretched into one of three shapes; symmetric dumbbell, asymmetric dumbbell or ellipsoid shape. This proves that the Stokes trap is an effective way to measure the stretching dynamics of soft materials in a solution.

With this data, the team created a phase diagram that can be used to determine what kinds of fluid flow will influence the deformation and physical properties of soft particles. With the Stokes trap, researchers can find what kinds of particle interactions will cause vesicles to aggregate.

Right now the technique is limited to the particle size that the Stokes trap can pick up. The team worked with particles that were generally larger than 100 nanometers in diameter, but the trap needs to be able to pick up particles that are 10-20 nanometers in diameter. Researchers are currently working towards capturing smaller particles and using the Stokes trap to study membrane proteins.

The paper on this research was published in Soft Matter.