Microrobots designed to pick up and place particles
Microrobots designed to pick up and place particles lead image
Surface tension traps microparticles at fluid interfaces, where they disturb the interface shape and generate hydrodynamic and capillary interactions. Stebe et al. have found a way to harness these interactions to successfully manipulate microrobots to pick up and place passive microparticles. The authors’ microrobots, which are controllable via a magnetic field, can manipulate microparticles at fluid interfaces.
“Our experiments show how microrobot shape and motion can be harnessed to take advantage of those naturally occurring forces, collect microparticle ‘cargo,’ and get them to desired locations,” said author Kathleen Stebe.
The group compared the applications of different microrobot shapes, including circular and square. In particular, the flower-shaped robot has specially designed features that gently curve the surrounding interface, which reduces the strength of the surrounding capillary interactions that naturally attract polystyrene particles. This allows particles to be assembled and subsequently released.
“The cargo is strongly attracted to the sharp corners of the robots, where the interface curvature is highest,” Stebe said. “If the corners are too sharp, the particles assemble irreversibly. However, by altering the sharpness and locations of those corners, we find an optimal configuration for both picking and placing a piece of cargo.”
The authors also designed docking stations to which particles can be delivered. Using visual feedback and an electromagnetic control system to drive the robot, they successfully demonstrated transfer of a particle from a microrobot to this station.
“The particles we’re manipulating in this study are about the average size of a human cell or smaller, for example, so this kind of system might have applications in the field of single-cell biology, with a magnetic microrobot moving individual cells through different stages of an experiment,” said Stebe.
Source: “Directed assembly and micro-manipulation of passive particles at fluid interfaces via capillarity using a magnetic micro-robot,” by Tianyi Yao, Nicholas G. Chisholm, Edward B. Steager and Kathleen J. Stebe, Applied Physics Letters (2020). The article can be accessed at https://doi.org/10.1063/1.5130635 .
