Edge effects determine the direction of bilayer bending

Area of Science:

• Materials Science
• Solid Mechanics
• Physics

Background:

• Preferential bending along the long edge in thin rectangular bilayers with strained layers has been observed.
• The underlying physical mechanism for this phenomenon remained poorly understood.

Purpose of the Study:

• To elucidate the physical basis for the preferential bending direction in strained thin rectangular bilayers.
• To understand the role of edge geometry and strain in determining bending behavior.

Main Methods:

• Theoretical analysis of thin rectangular bilayers with one isotropically strained layer.
• Investigation of energy landscapes associated with different bending configurations ('spiral' vs. 'cigar').

Main Results:

• Identified the existence of doubly curved regions at the curled edges as the cause of preferential bending.
• Demonstrated that these doubly curved regions lower the system's energy.
• Found that the energy difference between spiral and cigar shapes increases with the aspect ratio of the bilayer.

Conclusions:

• The preferential bending along the long edge is driven by energy minimization through the formation of doubly curved edge regions.
• The aspect ratio significantly influences the energy penalty associated with different bending modes.