Single channel microvascular delivery for self-healing polymer composites

Microvascular systems have successfully demonstrated self-healing functionality in neat polymers and fiber-reinforced composites alike. Many of the previously demonstrated systems deliver two-part healing agents through isolated microvascular networks to the site of damage where mixing of disparate resin and hardener components occurs to initiate polymerization. Mixing in two-component systems is hindered by small crack separation damage geometries and high viscosity healing agent components. To date, improvements to mixing have been accomplished by design of complex microvascular architectures or alternating pressurization of the two networks to induce chaotic flow in the damage zone. Complex vasculature presents a challenge for sample fabrication and alternating pressurization requires a computerized delivery regimen that lacks autonomy. Here, we present a microfluidic device that accomplishes in-situ mixing of two-part healing agents through a single microvascular channel. Components are sequestered from one another until reaching the damage site, where mixing occurs on length scales commensurate with microchannel diameters. Single-channel delivery eliminates the need for complex or branched vascular architectures and the modular design of the device is compatible with previously demonstrated vascularization techniques. Our approach is suitable for a wide range of two-part healing chemistries and achieves repeatable, autonomous delivery using static pressures after calibrating for healing agent surface energy, viscosity, and stoichiometry.