Cross-Species Bioinspired Anisotropic Surfaces for Active Droplet Transportation Driven by Unidirectional Microcolumn Waves

Abstract

Natural evolution has endowed diverse species with distinct geometric micro/nanostructures exhibiting admirable functions. Examples include anisotropic microgrooves/microstripes on the rice leaf surface for passive liquid directional rolling, and motile microcilia widely existed in mammals’ body for active matter transportation through in situ oscillation. Till now, bionic studies have been extensively performed by imitating a single specific biologic functional system. However, bionic fabrication of devices integrating multispecies architectures is rarely reported, which may sparkle more fascinating functionalities beyond natural findings. Here, a cross-species design strategy is adopted by combining the anisotropic wettability of the rice leaf surface and the directional transportation characteristics of motile cilia. High-aspect-ratio magnetically responsive microcolumn array (HAR-MRMA) is prepared for active droplet transportation. It is found that just like the motile microcilia, the unidirectional waves are formed by the real-time reconstruction of the microcolumn array under the moving magnetic field, enabling droplet (1–6 μL) to transport along the predetermined anisotropic orbit. Meanwhile, on-demand droplet horizontal transportation on the inclined plane can be realized by the rice leaf-like anisotropic surface, showcasing active nongravity-driven droplet transportation capability of the HAR-MRMA. The directional lossless transportation of droplet holds great potential in the fields of microfluidics, chemical microreaction, and intelligent droplet control system.

Magneto‐Responsive Shutter for On‐Demand Droplet Manipulation

“…[ 6 , 21 , 32 , 33 ] For example, magneto‐responsive conical array was employed for static fog collection under windless regions. [ 1 ] Magneto‐responsive arrays of microcilia and micropillars can realize switchable wettability, [ 2 , 20 , 23 ] reversible adhesion, [ 31 ] directional droplet transportation, [ 7 , 22 , 26 , 34 , 35 ] and droplet bouncing. [ 24 ] MRSS with magneto‐responsive Janus microplates enabled reversible switch between superhydrophobic and hydrophilic states, [ 21 ] and achieved 3D droplet transport.…”

Microfluidic Applications of Artificial Cilia: Recent Progress, Demonstration, and Future Perspectives

“…The light-controllable cilia were fabricated using Diarylethene and are capable of transporting objects, demonstrated to transport the polystyrene bead (PB) of 1 mm in diameter. Recent bioinspired artificial cilia established from natural cilia for transporting ability are reported elsewhere [ 23 , 30 , 31 , 34 , 36 , 37 , 38 , 39 , 40 ]. Inspired by the starfish surface, researchers designed ciliary bands [ 29 ], which can be actuated by ultrasound.…”

Recent Developments of Superhydrophobic Surfaces (SHS) for Underwater Drag Reduction Opportunities and Challenges

“…[169] Copyright 2018, American Institute of Physics. Lotus leaf Superhydrophobicity, self-cleaning, low adhesion [31,32] Mosquito eyes Superhydrophobicity, antifogging [33,34] Salvinia Superhydrophobicity, air-retention [35] Butterfly wings Superhydrophobicity, antireflection, directional adhesion, antifogging [36,37] Shark skin Underwater superoleophobicity, low drag, antifouling [38] Fish scales Underwater superoleophobicity [39,40] Nepenthes pitcher Superhydrophobicity [41][42][43][44][45] Gecko feet Superhydrophobicity, high adhesive, reversible adhesive [46,47] Springtails Superoleophobicity [48][49][50] Rice leaves Directional transport [51,52] Snail shell Superoleophobicity, self-cleaning [53] Rose petals Superhydrophobicity, structural color, high adhesion [54,55] Loquat leaves Anti-corrosion [56] Cicada wing Superhydrophobicity, anti-reflection [57][58][59] Water strider leg Superhydrophobicity, water-repellent, antifogging [60,61] Caterpillar Superhydrophilic; superhydrophobic [62] Nacre Underwater superoleophobicity, mechanical property, strength, [63,64] Adv. Mater.…”