Bicontinuous interfacially jammed emulsion gels (bijels) are soft materials that retain a liquid bicontinuous network stabilized by an interfacially jammed layer of nanoparticles. In this thesis, we investigated a microfluidic twisting method to fabricate micro-ropes of nano-structured bijel fibers. This method shows how weak microfibers with tensile strengths of a few kPa can be reinforced by 4 orders of magnitude by means of microfluidic twisting. Microfluidic twisting allows to produce continuous bijel fiber ropes of controllable architecture. Modelling the fluid flow field reveals the rope geometry dependence on a subtle force balance composed of rotational and translational shear stresses. However, the direction of the centrifugal force determines whether microropes undergo undulation during microfluidic twisting. The undulation of ropes can be avoided by decreasing the density of the fiber casting mixture, or upon increasing the density of the co-flowing liquid, enabling a controlled and continuous collection of uniform microropes. We envision microfluidic twisting to enable the fabrication of new composite materials with applications in flexible electronics, micro robotics, actuators, and tissue engineering. Furthermore, the knowledge gained from this thesis will facilitate future studies of microfiber twisting, as well as the assembly of particles, emulsion droplets or biological cells via microfluidic twisting
