Controlling impact behavior on superhydrophobic surfaces for droplets of nonionic surfactants by tailoring hydrophilic chain length

The behavior of high-speed droplets impacting on superhydrophobic surfaces plays an essential role in many daily applications. Adding surfactants is one excellent approach to improve droplet retention through enhancing the solid-liquid interface interaction. However, the regulating of the impact process has been rarely concerned about the effect of molecular structure on it. In our work, we study the impact behavior of nonionic surfactants Triton X (TX) on superhydrophobic surfaces by characterizing the diffusion rate of surfactant molecules and the receding contact angle and adhesion of surfactant solution on surfaces. We reveal that droplets of TX surfactant solution can deposit better on superhydrophobic surfaces as hydrophilic (ethylene oxide, EO) chain length increasing, which is mainly attributed by the faster diffusion speed towards the newly formed interface during the spreading phase, leading to better wettability transition and larger pinning area on the substrate. Our work promotes the understanding of the mechanism that controls the impact behavior of droplets of surfactant by adjusting the EO chain length, which provides an effective strategy to control droplet deposition on superhydrophobic surfaces. © 2021 Elsevier B.V.