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Abstract When a suspension of spherical or near-spherical particles passes through a constriction the particle volume fraction either remains the same or decreases. In contrast to these particulate suspensions, here we observe that an entangled fiber suspension increases its volume fraction up to 14-fold after passing through a constriction. We attribute this response to the entanglements among the fibers that allows the network to move faster than the liquid. By changing the fiber geometry, we find that the entanglements originate from interlocking shapes or high fiber flexibility. A quantitative poroelastic model is used to explain the increase in velocity and extrudate volume fraction. These results provide a new strategy to use fiber volume fraction, flexibility, and shape to tune soft material properties, e.g., suspension concentration and porosity, during delivery, as occurs in healthcare, three-dimensional printing, and material repair. 

Flows of nonequilibrated aqueous two-phase systems may result in the formation of a 3-dimensional flow field, due to a gradient in tension across the boundary of the two phases. 

Abstract Injectable hydrogels are valuable tools in tissue engineering and regenerative medicine due to their unique advantages of injectability with minimal invasiveness and usability for irregularly shaped sites. However, it remains challenging to achieve scalable manufacturing together with matching physicochemical properties and on‐demand drug release for a high level of control over biophysical and biomedical cues to direct endogenous cells. Here, the use of an injectable fibro‐gel is demonstrated, a water‐filled network of entangled hydrogel microfibers, whose physicochemical properties and drug release profiles can be tailored to overcome these shortcomings. This fibro‐gel exhibits favorable in vitro biocompatibility and the capability to aid vascularization. The potential use of the fibro‐gel for advancing tissue regeneration is explored with a mice excision skin model. Preliminary in vivo tests indicate that the fibro‐gel promotes wound healing and new healthy tissue regeneration at a faster rate than a commercial gel. Moreover, it is demonstrated that the release of distinct drugs at different rates can further accelerate wound healing with higher efficiency, by using a two‐layer fibro‐gel model. The combination of injectability and tailorable properties of this fibro‐gel offers a promising approach in biomedical fields such as therapeutic delivery, medical dressings, and 3D tissue scaffolds for tissue engineering.