Micropillar with Radial Gradient Modulus Enables Robust Adhesion and Friction

Area of Science:

• Materials Science
• Biomimetics
• Nanotechnology

Background:

• Beetle setae exhibit gradient modulus crucial for adhesion and locomotion on natural surfaces.
• Replicating radial modulus gradients in microstructures is challenging but key for enhanced contact mechanics.
• Existing homogeneous micropillars lack the performance of natural adhesive structures.

Purpose of the Study:

• To develop a micro-scale structure with a radial gradient modulus mimicking beetle setae.
• To investigate the adhesion and friction properties of the gradient modulus (GM) structure.
• To establish a fabrication strategy for creating radial modulus gradients in microstructures.

Main Methods:

• Fabrication of polydimethylsiloxane (PDMS) micropillars with a radial gradient modulus (GM) using a photosensitive resin template and polymerization inhibitor.
• Characterization of adhesion and friction performance by comparing GM pillars with soft homogeneous (SH) and hard homogeneous (HH) micropillars.
• Testing the robustness and durability of the GM structure over 400 cycles.

Main Results:

• GM structures achieved adhesion up to 84 kPa, significantly outperforming SH (2.3x) and HH (4.7x) pillars.
• Radial gradient modulus facilitated better contact formation and shifted stress concentration to the center, enhancing adhesion.
• GM structures demonstrated strong friction (8.1 mN), exceeding SH (1.2x) and HH (2.6x) pillars, and maintained performance after 400 cycles.

Conclusions:

• The developed radial gradient modulus micropillar (GM) offers a robust solution for strong adhesion and friction.
• The fabrication strategy provides a viable method for creating modulus gradients at the microscale.
• This biomimetic approach has potential applications in areas requiring reliable surface attachment and locomotion.