Mosquito Repellent Induced by Wetting Phenomenon of Hydrophobic Liquid

Mosquitoes have a unique leg with highly water-repellent due to the fine geometrical structure of their surface. While the roughness of hydrophobic surfaces magnifies their non-wetting property with respect to water, it enhances their wettability with respect to hydrophobic liquids such as silicone oils. This high wettability induces strong attractive meniscus forces on a mosquito’s legs（up to 87％ of the mosquito’s weight）towards the liquids. We studied the landing behaviour of mosquitoes on oil-coated surfaces and observed that the mosquito contact time was reduced compared to that on hydrophilic-liquid-coated surfaces. The observed escape behaviour occurred consistently with several hydrophobic liquids. As the repellent effect is similar to multiple hydrophobic substances, it is likely to be mechanically stimulated owing to the physical properties of the hydrophobic liquids and not due to chemical interactions. On human skin, the contact time was sufficiently short to prevent mosquitoes from starting to blood-feed. This wetting-based method of repellent opens up opportunities in the design of safer, more effective products.