The authors used a Droplet Lab Dropometer to measure water contact angle (WCA) on the optimized soyhull-extract (SHE) film—directly quantifying the film’s surface wetting behavior (hydrophilicity/hydrophobicity), which is central to packaging performance where moisture exposure, surface interactions, and barrier behavior matter. The paper explicitly reports that WCA was measured using a Dropometer (Droplet Lab, Markham, ON, Canada) and evaluated over time (0, 10, 20, 30 s) to observe changes after droplet placement.

• Optimized packaging film performance: The optimized film achieved TS = 10.4 ± 1.0 MPa, EB = 9.4 ± 1.8%, and WVP = 3.5 ± 0.4 × 10−11 g·m−1·s−1·Pa−1.
• Validated optimization approach: Predicted vs. experimental TS/EB/WVP were statistically consistent (no significant differences reported).
• Surface wettability quantified by Dropometer: The film surface is hydrophilic (WCA < 90°) and WCA decreased from ~76.9° (0 s) to ~49.2° (30 s), indicating increasing wetting/spreading/interaction with water over time.
• Relevance vs conventional plastics: The authors note LDPE is more hydrophobic (reported WCA ~100.7°), and they discuss pathways (e.g., incorporating hydrophobic components like lignin/waxes) to improve water resistance.

End-of-life advantage: The film shows rapid biodegradation (reported ~90% degradation within 37 days at 24% soil moisture in the abstract).

For packaging teams developing bio-based film structures, contact angle is a fast, quantitative way to screen whether a new film will behave more like a moisture-sensitive, hydrophilic biopolymer (potentially needing coatings/lamination) versus a more water-repellent packaging surface. Here, the Dropometer WCA time-series reveals that the soyhull-derived film wets increasingly over 30 seconds—information that can directly inform coating selection, surface treatments, and QC specs when targeting real-world humidity/water exposure while still benefiting from strong biodegradability and sustainability claims.