Effect of adhesion force on the height pesticide droplets bounce on impaction with cabbage leaf surfaces.

The relationship between adhesion force and the height drops containing difenoconazole-loaded mesoporous silica nanoparticles (DF-MSNs)/Tween 80 bounce on cabbage leaf surfaces was investigated as a function of Tween 80 concentration. The adhesion force of a pesticide droplet on cabbage leaf surfaces was assessed using a high-sensitivity microelectromechanical balance system and the impact behavior was recorded with a high-speed camera. The height droplets bounced decreased with increasing adhesion force, with a negative correlation between the height of the bouncing drops and adhesion force. Although droplets containing ≥0.06% Tween 80 adhered to the cabbage leaves, the retraction height was still observed to decrease as the adhesion force increased. The experimental results indicate that for cabbage leaf surfaces, the adhesion force has a significant effect on the height drops bounce. The results provide new insights into how researchers can screen for formulations for hydrophobic target crops and how to increase spray adhesion to difficult-to-wet crop leaf surfaces.

Influence of the surface limiting elasticity modulus on the impact behavior of droplets of difenoconazole-loaded mesoporous silica nanoparticles with associated SDS.

The relation between the surface limiting elasticity modulus, ε0, of difenoconazole-loaded mesoporous silica nanoparticle (DF-MSN) formulations with associated SDS and the height of the first returning droplet impacting on cabbage and rice leaf surfaces was investigated. The surface dilational rheology properties were determined by means of surface tension relaxation. The impact of a droplet on the leaf surface was recorded with a high-speed camera. The surface limiting elasticity modulus, ε0, shows differences with different SDS concentrations. A positive correlation between droplet first rebound height and the surface limiting elasticity modulus, ε0, is observed. The pesticide droplet impact on the target leaf surface is a rather complex phenomenon, so the focus of this article is to establish a relationship between the surface limiting elasticity modulus, ε0, and droplet first rebound height. These findings introduce a chemical way to affect the impact behavior of pesticide droplets on target crop leaf surfaces, which may be of particular importance for pesticide spraying and crop protection, especially for hydrophobic and superhydrophobic target crops.

Evaporation kinetics of surfactant solution droplets on rice (Oryza sativa) leaves.

The dynamics of evaporating sessile droplets on hydrophilic or hydrophobic surfaces is widely studied, and many models for these processes have been developed based on experimental evidence. However, few research has been explored on the evaporation of sessile droplets of surfactant or pesticide solutions on target crop leaves. Thus, in this paper the impact of surfactant concentrations on contact angle, contact diameter, droplet height, and evolution of the droplets' evaporative volume on rice leaf surfaces have been investigated. The results indicate that the evaporation kinetics of surfactant droplets on rice leaves were influenced by both the surfactant concentrations and the hydrophobicity of rice leaf surfaces. When the surfactant concentration is lower than the surfactant CMC (critical micelle concentration), the droplet evaporation time is much longer than that of the high surfactant concentration. This is due to the longer existence time of a narrow wedge region under the lower surfactant concentration, and such narrow wedge region further restricts the droplet evaporation. Besides, our experimental data are shown to roughly collapse onto theoretical curves based on the model presented by Popov. This study could supply theoretical data on the evaporation of the adjuvant or pesticide droplets for practical applications in agriculture.