Gradient Micropillar Array Inspired by Tree Frog for Robust Adhesion on Dry and Wet Surfaces

Abstract

The strong adhesion on dry and wet surfaces and the durability of bioinspired hierarchical fibrillar adhesives are critical for their applications. However, the critical design for the strong adhesion normally depends on fine sub-micron structures which could be damaged during repeat usage. Here, we develop a tree frog-inspired gradient composite micropillars array (GP), which not only realizes a 2.3-times dry adhesion and a 5.6-times wet adhesion as compared to the pure polydimethylsiloxane (PDMS) micropillars array (PP), but also shows excellent durability over 200 repeating cycles of attachment/detachment and self-cleaning ability. A GP consists of stiffer tips and softer roots by incorporating gradient dispersed CaCO3 nanoparticles in PDMS micropillar stalks. The modulus gradient along the micropillar height facilitates the contact formation and enhances the maximum stress during the detaching. The study here provides a new design strategy for robust adhesives for practical applications in the fields of robotics, electronics, medical engineering, etc.

Picking food by robot hand with tree-frog like pad in various wet conditions

“…This principle is appropriate to design a soft robotic hand for autonomously picking up wet deformable objects without requiring high squeeze force. Previous researchers have investigated the principle of wet adhesion mimicking the attachment of tree-frog toes to a substrate [22][23][24][25][26][27][28]. Hybrid surface patterns [29][30][31][32][33] formed with hexagonal micro-pillars have been experimentally compared among different construction materials.…”

Self-assembled micropillar arrays via near-field electrospinning

“…4 Compared to planar films, films with micropillar arrays have enhanced surface areas, endowing the surface with new functions such as adhesion and water-repellency. 5,6 Controlled spacing allows micropillar arrays to be used in electrochemical detection, and optical, biomedical and energy harvesting applications. [7][8][9][10][11][12] Therefore, the fabrication and application of microcolumn arrays are essential for research.…”

Bioinspired Core–Shell Micropillar Array for Robust and Enhanced Adhesion and Friction

“…41 By incorporating gradientdistributed CaCO 3 nanoparticles (NPs) into PDMS micropillar, the adhesion was enhanced by 2.3 times and remained stable during 200 cycles of attachment−detachment. 43 The composite pillars with a core−shell structure are also reported to be advantageous in enhancing both adhesion and stability. 44−48 On one hand, the implementation of a softshell material facilitates the establishment of conformal contact with the surface, thereby leading to improved adhesion.…”

“…To construct composite pillars is an effective strategy to enhance adhesion performance and stability. − Polyurethane acrylate (PUA) and magnetic Fe 3 O 4 @SiO 2 were synergistically combined to create gradient composite micropillars, of which the modulus gradually decreases from root to the tip of the pillar, resulting in substantial improvements in shear adhesion and durability . By incorporating gradient-distributed CaCO 3 nanoparticles (NPs) into PDMS micropillar, the adhesion was enhanced by 2.3 times and remained stable during 200 cycles of attachment–detachment .…”

“…To construct composite pillars is an effective strategy to enhance adhesion performance and stability. − Polyurethane acrylate (PUA) and magnetic Fe 3 O 4 @SiO 2 were synergistically combined to create gradient composite micropillars, of which the modulus gradually decreases from root to the tip of the pillar, resulting in substantial improvements in shear adhesion and durability . By incorporating gradient-distributed CaCO 3 nanoparticles (NPs) into PDMS micropillar, the adhesion was enhanced by 2.3 times and remained stable during 200 cycles of attachment–detachment . The composite pillars with a core–shell structure are also reported to be advantageous in enhancing both adhesion and stability. − On one hand, the implementation of a soft-shell material facilitates the establishment of conformal contact with the surface, thereby leading to improved adhesion.…”