The Droplet Lab tabletop goniometer was used to quantify water wettability (hydrophobicity) via contact angle measurements on the electrospun fiber mats (and a smooth PS film reference). The contact angle dataset is the key performance readout linking solvent-driven micro/nano-porosity and bead/roughness features to textile-relevant water repellency, and it enables comparison across solvent ratios and spinning voltages (Characterization section; contact angle results shown in the contact angle figures/tables).

• All electrospun PS mats were highly hydrophobic, with water contact angles spanning ~130.1° to 143.2° across conditions (Table 5).
• Higher applied voltage generally increased contact angle, attributed to smaller fiber diameters and increased roughness contributions from pores and/or beads (Figure 7 discussion).
• The highest contact angles occurred for chloroform:DMF = 30:70, particularly at 22.5 kV (contact angle up to 143.2° ± 0.6°), associated with bead formation that creates hierarchical roughness.
• Solvent ratio strongly shifts surface texture:
  • 70:30 tends to form thinner, more homogeneous fibers with external surface porosity (~100 nm scale).
  • 50:50 yields largest fiber diameters and lowest contact angles (less favorable for water repellency).
  • 30:70 promotes beads + internal porosity, which increases hydrophobicity via multi-scale roughness.

The wettability behavior is interpreted using Cassie–Baxter wetting, with projected solid fraction f < 0.3 (Table 6), implying air fraction > 0.7 under the droplet—consistent with strong water repellency on porous fibrous surfaces.

For fabric and textile-style nonwovens, this work shows how solvent formulation (chloroform/DMF ratio) and electrospinning voltage can be used as practical “knobs” to tune fiber diameter, bead density, and pore structure, which directly controls water repellency. A Droplet Lab contact angle method can be translated into a simple QC/acceptance test for water-repellent fibrous webs or coatings—helping teams set specifications (e.g., minimum contact angle threshold), compare process windows, and optimize designs that balance repellency, surface texture, and functional surface area for end uses like moisture-resistant textiles or technical fabric layers.