Reducing droplet contact time for green and breathable water repellent rainwear

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Fabric breathability typically requires large pores to allow moisture evaporation, and liquid repellency requires as small of pores as possible (or none). The goal of this project is to develop breathable and water repellent rainwear by a minimization of the contact time between droplets and fabrics. Droplets soak into the pores of textiles over time and, if this time is minimal, fabrics that can breath and repel rain drops can be realized. Two fluid-dynamic technologies will be investigated to minimize droplet contact time during impact on a fabric: "pancake bouncing" and "butterfly wing droplet splitting". Both concepts reduce the contact time between droplets and surface below the fundamental limit thought to be set by nature. During pancake bouncing, droplets interact with the surface differently than in commonplace impact scenarios. During butterfly wing droplet splitting a single droplet is split into two or more sub-droplets, which alters the time of contact. Precise engineering of the textile's surface's structure and chemistry is required to observe both phenomena.One PhD student and one PDF will utilize non-hazardous surface chemistries to functionalize textiles in order to achieve the surface properties required to enable these two droplet-bouncing phenomena. The PDF will focus on the chemistry development while concurrently the PhD student works on the surface structure. Both HQP will investigate the hydrodynamics of impacting droplets once the fabrics are correctly designed. For macroscopic texturing we will work with our industry partner Lululemon Athletica to fabricate novel fabric structures that HQP will then modify.The simulated effect of body angle and movement will also be investigated, in order to determine how the fabrics work on more realistic surfaces. By the end of the project we envisage design criteria to be constructed in order to realize breathable, water-repellent rainwear.