Adhesive pad differentiation in Drosophila melanogaster depends on the Polycomb group gene Su(z)2

Framework with cytoskeletal actin filaments forming insect footpad hairs inspires biomimetic adhesive device design

Footpads allow insects to walk on smooth surfaces. Specifically, liquid secretions on the footpad mediate adhesiveness through Van der Waals, Coulomb, and attractive capillary forces. Although the morphology and function of the footpad are well defined, the mechanism underlying their formation remains elusive. Here, we demonstrate that footpad hair in Drosophila is formed by the elongation of the hair cells and assembly of actin filaments. Knockdown of Actin5C caused a malformation of the hair structure, resulting in reduced ability to adhere to smooth substrates. We determined that functional footpads are created when hair cells form effective frameworks with actin filament bundles, thereby shaping the hair tip and facilitating cuticular deposition. We adapted this mechanism of microstructure formation to design a new artificial adhesive device⁠—a spatula-like fiber-framed adhesive device supported by nylon fibers with a gel material at the tip. This simple self-assembly mechanism facilitates the energy-efficient production of low-cost adhesion devices.

Kimura et al. demonstrate that footpad hair formation of Drosophila involves elongation of hair cells and assembly of actin filaments, followed by cuticular deposition. They then use this mechanism to design an artificial highly adhesive device with easy attachment and detachment properties.

Effective Elastic Modulus of Structured Adhesives: From Biology to Biomimetics

Micro- and nano-hierarchical structures (lamellae, setae, branches, and spatulae) on the toe pads of many animals play key roles for generating strong but reversible adhesion for locomotion. The hierarchical structure possesses significantly reduced, effective elastic modulus (Eeff), as compared to the inherent elastic modulus (Einh) of the corresponding biological material (and therefore contributes to a better compliance with the counterpart surface). Learning from nature, three types of hierarchical structures (namely self-similar pillar structure, lamella⁻pillar hybrid structure, and porous structure) have been developed and investigated.