(492a) Centrifugal Assembly of Helical Fibers for pH Responsive Composite Hydrogels

Centrifugal microfluidics has been widely used to integrate 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. Moreover, we demonstrate that the micro ropes generated from this method can be transformed into stimuli responsive composite hydrogels with enhanced mechanical flexibility [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 microfluidic twisting can become a new unit operation to advance high-throughput screening, lab-on-a-chip diagnostics, biochemical assays and material synthesis in microfluidics.

References:

[1] M.F. Haase, K. J. Stebe, D. Lee, Advanced Materials (2015)

[2] S.P. Kharal, R.P. Hesketh, M.F. Haase, Advanced Functional Materials (2020)

[3] S.P. Kharal, M.F. Haase, Small (2022)