Insect Antiadhesive Surfaces Using Electrosprayed Wrinkled Ethyl Cellulose Particles

Abstract

A range of plants developed leaves, the surfaces of which prevent or diminish insect adhesion due to their microscopic topography. Well known examples include the leaves of the lychee tree (Litchi chinensis). Here, we report a method to coat substrates with ethyl cellulose microparticles that exhibit wrinkled surfaces, resulting in surface morphologies that closely resemble those of insect repelling plants, i.e., Litchi chinensis. The microparticles were prepared by electrospraying, a method that allowed tuning of the particle size and surface morphology. By measuring the traction forces of Colorado potato beetles walking on these surfaces, the wrinkly microsphere parameters were optimized, resulting in biomimetic surfaces that surpass the antiadhesive properties of the biological role model. This study may pave the way to sustainable, nontoxic insecticide replacements.

Synthetic Strategies for Polymer Particles with Surface Concavities

“…Surface‐wrinkled (or crumpled) particles that have significantly enlarged surface areas widely exist in the nature (e.g., pollens, plant seeds, microorganisms, etc.). [ 177–180 ] Inspired by them, surface‐wrinkled polymer particles have been investigated both theoretically [ 181,182 ] and experimentally [ 56,57,139,183–226 ] in recent years. The synthesis of surface‐wrinkled polymer particles can also be conducted by polymerization or post‐treatment methods, as discussed below.…”

“…In a very recent example, Moatsou and co‐workers reported the preparation of 10 µm‐sized wrinkled EC particles by electrospraying. [ 219 ] In the subsequent solvent evaporation process of the droplets, the elastic moduli difference between their inner and outer layers caused wrinkling.…”

“…Moatsou and co‐workers reported a method to coat glass slides with wrinkled ethyl cellulose microparticles to mimick surface morphologies of insect repelling plants. [ 219 ] By optimization parameters of the wrinkled microsphere, biomimetic surfaces with comparable insect anti‐adhesive properties to champion structures of nature were obtained. By using microparticles with a size below 10 µm, wrinkle width below 2 µm and wrinkle‐to‐wrinkle distances in the µm‐range, the traction force on the resulting surface could be lowered by more than 20‐ fold compared to smooth glass surface.…”

“…To date, several post-treatment methods have been proposed for the fabrication of surface-wrinkled polymer particles, which involve surface treatment-based methods, [198][199][200][201][202][203][204][205][206][207][208][209][210][211][212] microfluidic emulsification/emulsion-solvent evaporation, [213][214][215][216][217] electrospraying/solvent evaporation, [218,219] templating methods [220][221][222][223][224] and some other methods. [225][226][227]…”

“…The most prominent characteristic of the concave polymer particles is their larger specific surface area than their spherical counterparts. On the basis of the detailed surface morphology and component of the concave polymer particles, various potential applications, especially in the biological fields, have been reported, such as drug delivery, [30,35,124,140,165,185,207,216] imaging contrast agent, [33,140] insect-repellent, [219] superhydrophobic coatings, [39,101,213] oil-water separation, [65] colloidal model systems, [47] SERS sensing, [194] etc. Some selected examples are presented here.…”