High‐Tensile Strength, Composite Bijels through Microfluidic Twisting

Abstract

Rope making is a millennia old technique to collectively assemble numerous weak filaments into flexible and high tensile strength bundles. However, delicate soft matter fibers lack the robustness to be twisted into bundles by means of mechanical rope making tools. Here, weak microfibers with tensile strengths of a few kilopascals are combined into ropes via microfluidic twisting. This is demonstrated for recently introduced fibers made of bicontinuous interfacially jammed emulsion gels (bijels). Bijels show promising applications in use as membranes, microreactors, energy and healthcare materials, but their low tensile strength make reinforcement strategies imperative. Hydrodynamic twisting allows to produce continuous bijel fiber bundles of controllable architecture. Modelling the fluid flow field reveals the bundle geometry dependence on a subtle force balance composed of rotational and translational shear stresses. Moreover, combining multiple bijel fibers of different compositions enables the introduction of polymeric support fibers to raise the tensile strength to tens of megapascals, while simultaneously preserving the liquid like properties of the bijel fibers for transport applications. Hydrodynamic twisting shows potentials to enable the combination of a wide range of materials resulting in composites with features greater than the sum of their parts.

Explaining Outcome Differences between Men and Women following Mild Traumatic Brain Injury

“…The idea of twisting artificial muscles to increase their strength also attracted considerable attention recently. 34,35 Using thermal heating as driving source, Kharal et al created composite bijels (bicontinuous interfacially jammed emulsion gels) by hydrodynamic twisting multiple bijel fibers around a core polymeric support fiber. 35 The composite bijels could increase the tensile strength up to 20 MPa, roughly 4000 times higher than that of the liquid bijel fibers.…”

“…34,35 Using thermal heating as driving source, Kharal et al created composite bijels (bicontinuous interfacially jammed emulsion gels) by hydrodynamic twisting multiple bijel fibers around a core polymeric support fiber. 35 The composite bijels could increase the tensile strength up to 20 MPa, roughly 4000 times higher than that of the liquid bijel fibers. Many researchers have also investigated hybrid yarn artificial muscles (HYAMs), in which they tailored the multiple fibers to increase the muscle energy densities.…”

Centrifugal Assembly of Helical Bijel Fibers for pH Responsive Composite Hydrogels

“…[32] We generate multiple bijel fibers by flowing the precursor dispersion out of several parallel glass capillaries into a coaxially aligned outer capillary. [19] These bijel fibers are then helically wrapped around each other via microfluidic twisting (see Figure 1B). The twisting originates from the rotation of the outer cylindrical capillary (ID = 0.8 mm) around its axis.…”

“…Moreover, it has limited the choices of fiber precursor dispersions, resulting in strong, but inflexible helical fibers. [19] Here, we close this knowledge gap and show how centrifugal forces during microfluidic twisting enable the continuous assembly and collection of flexible, stimuli-responsive microropes. The assembly and collection of the microropes depends on the direction of the centrifugal force, which is determined by the density difference between the individual rope filaments and the surrounding fluid.…”

“…[17,18] Recently, we have introduced microfluidic twisting (MT) to continuously generate composite helical fiber assemblies. [19] microfluidic twisting enables the combination of multiple helical fibers into high-order helices. The constituent fibers can have different sizes, twisting degrees, or chemical compositions.…”