Sliding friction of a pillar array interface: part I

Area of Science:

• Interfacial mechanics
• Bio-inspired engineering
• Materials science

Background:

• Biological systems utilize shape-complementary surfaces to control interfacial properties like adhesion and friction.
• Bio-inspired and biomimetic structures offer tunable friction and adhesion, with applications in soft robotics and tire manufacturing.

Purpose of the Study:

• To investigate friction between polydimethylsiloxane (PDMS) surfaces patterned with pillar arrays.
• To analyze the formation and behavior of Moiré patterns and interfacial dislocations during sliding.
• To understand the relationship between surface structure, misorientation, lattice mismatch, and frictional stress.

Main Methods:

• Fabrication of PDMS samples with patterned pillar arrays.
• Experimental observation and analysis of Moiré pattern formation and interfacial dislocation glide.
• Measurement of inter-pillar interactions and frictional forces.
• Development of a geometric model to correlate sliding with frictional stress.

Main Results:

• Contact between patterned PDMS surfaces generates Moiré patterns, interpretable as interfacial dislocations.
• Surface misorientation leads to screw dislocations, while lattice mismatch creates edge dislocations.
• Sliding motion involves the glide of these interfacial patterns.
• Frictional stress arises from periodic pillar-pillar contact and sliding, showing good agreement between experimental measurements and the geometric model.

Conclusions:

• The study elucidates the fundamental mechanisms governing friction in patterned surfaces through Moiré patterns and dislocations.
• The findings provide a quantitative understanding of how surface geometry and relative orientation dictate interfacial mechanical properties.
• This research contributes to the design principles for advanced materials with controlled friction and adhesion for technological applications.