Heterogeneous Condensation on Simplified Viral Envelope Protein Structures

Elucidating the mechanisms of heterogeneous condensation on viral and bacterial envelopes is crucial for understanding biothreat transport phenomena and optimizing capture efficiency in condensation-based detection devices. We investigate the impact of viral envelope geometric parameters [e.g., surface structure pitch-to-diameter ratio (p/d)] due to protruding glycoproteins and surface wettability [via liquid-solid interaction intensity (f)] on heterogeneous condensation using molecular dynamics simulations. Complex glycoprotein structures were modeled as cylindrical pillars to analyze condensation rates and active surface areas across a range of p/d ratios (1.0, 1.2, 1.3, 1.7, 2.0, and ∞) and contact angles (θ = 15°, 75°, and 105°, corresponding to f = 3.0, 2.0, and 1.5) to address envelope geometries for a wide variety of viruses. The results indicate that initial condensation rates on surfaces with intermediate p/d ratios (e.g., 1.2-1.3) are significantly higher due to increased active surface area and droplet cluster formations. The rapid initial condensation fills up the gap between the pillars, reducing the active surface area and leading to a gradual decrease and a plateau in the condensation rate. The increased peak condensation rates are not observed as p/d increased to and above 1.7, as the exhibited behavior is like condensation on the unstructured surface. An increase in surface hydrophilicity (θ = 15°, f = 3.0) leads to faster nucleation and higher peak condensation rates compared to hydrophobic surfaces (θ = 105°, f = 1.5). The influence of viral envelope geometries and surface wettability on the heterogeneous condensation mechanisms offers foundational insights required to understand airborne biothreat transmission, which is particularly important in the atmosphere and respiratory tract, and improve biothreat detection methods utilizing condensation-based capture devices.