Polydimethylsiloxane bilayer films with an embedded spontaneous curvature

Area of Science:

• Materials Science
• Polymer Science
• Soft Matter Physics

Background:

• Elastomeric films offer tunable properties for advanced applications.
• Creating controlled stress gradients in polymers is challenging.
• Polydimethylsiloxane (PDMS) is a versatile elastomer with tunable properties.

Purpose of the Study:

• To develop a method for creating in-plane gradient stress in PDMS films.
• To investigate the relationship between stress, film geometry, and deformation.
• To demonstrate the fabrication of 3D structures from stress-engineered PDMS films.

Main Methods:

• Fabrication of PDMS/(PDMS + silicone oil) crosslinked bilayers.
• Extraction of silicone oil using an organic solvent to induce differential stress.
• Analysis of film curvature using the relationship κ = 1.5δH(-1).
• Curvature mapping of triangular PDMS plates to identify deformation types.
• Design and cutting of 2D patterns for self-folding into 3D shapes.

Main Results:

• Successfully created PDMS films with embedded in-plane gradient stress.
• Observed out-of-plane deformation directly resulting from differential stress.
• Validated a simple relationship describing the curvature of bilayer stripes.
• Identified spherical and cylindrical deformation modes in PDMS plates.
• Demonstrated the formation of various 3D objects, including microtubes, via self-folding.

Conclusions:

• The developed method effectively embeds gradient stress in PDMS films.
• The resulting stress gradients drive predictable out-of-plane deformations and self-folding.
• This technique allows for the controlled fabrication of complex 3D structures from 2D PDMS patterns.
• The findings have implications for designing micro-devices, actuators, and soft robotics.