Demonstrating the antibiofouling property of the Clanger cicada wing with ANSYS Fluent simulations Brady C. Pilsbury, Paul W. Leu The Laboratory for Advanced Materials at Pittsburgh, Department of Industrial Engineering Brady Pilsbury is originally from Warren, NJ. His interests in science, writing, and law drive him to become a patent agent.
Brady C. Pilsbury
Dr. Leu is an Associate Professor in the Department of Industrial Engineering and the Department of Mechanical Engineering and Materials Science. He received his BS in Mechanical Engineering at Rice University in 2002, his MS from Stanford University in 2004, and his PhD from Stanford Paul W. Leu, Ph.D. University in 2008. Dr. Leu’s lab research focuses on designing and understanding advanced materials by computational modeling and experimental research.
Significance Statement
Microdroplets released upon coughing, sneezing, or speaking are one source of spread for human viruses. Simulation results illustrate how the introduction of nanostructures inspired by the Clanger cicada wing to a surface can limit microdroplet adhesion and help reduce the spread of pathogens due to contact with surfaces.
Category: Computational Research
Keywords: Nanostructures, Antibiofouling, ANSYS Fluent
72 Undergraduate Research at the Swanson School of Engineering
Abstract
The Clanger cicada wing is known to have an antibiofouling effect related to the particular pattern of nanostructures on the wing surface. Understanding the mechanisms that create this effect allows for the development of effective antibiofouling nanostructured surfaces, which can help reduce the spread of pathogens. Water repellency is well established as one such mechanism, which this study seeks to validate with the use of water droplet simulations conducted in ANSYS Fluent. The 2D simulations show how the addition of Clanger cicada wing inspired nanostructures to a flat surface impacts surface hydrophobicity and water droplet contact angle hysteresis. A pre-existing empirical dynamic contact angel model was implemented to capture differences in contact angle hysteresis between the flat and nanostructured surface. The application of such a model to a nanostructured surface has not been previously attempted within ANSYS Fluent. The water droplet achieved a greater contact angle and lower contact angle hysteresis on the nanostructured surface when compared to the flat control, indicating that the drop entered the Cassie-Baxter state and would roll off the surface at low incline angles. These results support the repellence of microdroplets containing pathogens as one mechanism through which the Clanger cicada wing achieves a strong antibiofouling effect.
1. Introduction
The wings of insects like the Clanger cicada (Psaltoda claripennis) have been observed to have highly hydrophobic and antibiofouling properties due to the presence of nanopatterns on the surface of their wings [1]. The behavior of microdroplets on such nanopatterned surfaces has implications for public health, since viruses and other pathogens can be transferred through microdroplets. Surfaces designed to strongly repel and roll off microdroplets can help reduce the spread of pathogens. The water repellency of a surface is often characterized by a water droplet contact angle measurement. This angle refers to the angle formed by the gas-liquid and solid-liquid interfaces at the points along the bottom edge of the droplet where all three phases meet. Convention dictates that a surface is hydrophilic when its contact angle is less than 90°, hydrophobic when the contact angle is greater than 90°, and superhydrophobic when the contact angle exceeds 150° [2]. Nanoscale surface roughness can allow a droplet to enter the Cassie-Baxter state, which is characterized by the droplet resting atop protrusions from the surface and bridging over lower elevation regions of the surface instead of penetrating them [2]. Water droplets in the Cassie-Baxter state tend to have a high contact angle, low contact angle hysteresis, and an associated low run off angle [2]. Contact angle hysteresis refers to the
