Centrifugal assembly of helical fibers during microfluidic twisting

Centrifugal microfluidics has been widely used to integrate different processes such as separating, mixing, and detecting molecules at the nanoscale. Aside from these unit operations, an unrecognized use of the centrifugal effect is introduced during Microfluidic Twisting (MT).

 

We investigate the assembly of helical soft matter fibers in a rotating microcapillary. During assembly, the fibers undergo phase separation, generating particle stabilized bicontinuous emulsion gels (bijels) [1]. This process is accompanied by a transition of the fiber density over time. As a result, the direction of the centrifugal force in the rotating microcapillary changes, pulling fibers of lower density towards the rotation axis, resulting in a helically woven micro rope. We use high-speed video microscopy and computer simulations to thoroughly investigate this effect. The resulting understanding enables control of the helical fiber assembly through manipulation of the densities of the fluids involved. [2, 3].

 

We envision MT to enable the fabrication of new composite materials with applications in flexible electronics, micro robotics, actuators, additive manufacturing, catalysis and tissue engineering. With these potentials, we believe that MT can become a new unit operation to advance high-throughput screening, lab-on-a-chip diagnostics, biochemical assays and material synthesis in microfluidics.