Y-Shaped Patterned Thin Films for Stretchable Electronics
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Solution Overview
Problem
Existing methods for engineering elasticity in intrinsically non-elastic materials, such as films and substrates, are expensive, unreliable, and do not provide satisfactory elasticity, making them unsuitable for many applications, particularly in stretchable electronics where materials need to maintain electrical properties under mechanical stress.
Innovation Solution
A method involving the patterning of Y-shaped motifs throughout the material, which allows for elasticity without preferential direction, by forming cuts that extend through the thickness of the layer with branches of equal or predefined lengths and widths, enabling the material to stretch and regain its original shape upon removal of strain, applicable to both ductile and brittle materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional rigid materials are used in stretchable electronics, then electrical conductivity is maintained, but the materials exhibit limited elasticity with fracture strains less than 5%
Solution Approach 1:
The rigid material is segmented into discrete islands separated by flexible connections or gaps. This segmentation allows the rigid conductive elements to maintain their electrical properties while the gaps and flexible connections provide the necessary elasticity and stretchability, enabling the overall structure to deform without fracturing the rigid components.
Solution Approach 2:
Rigid conductive elements are nested within or supported by flexible substrate structures. The rigid materials are embedded in compliant matrices or mounted on flexible circuits that can deform independently, allowing the rigid components to maintain electrical conductivity while the surrounding flexible structures provide elasticity and accommodate mechanical strain.
2Adaptability or versatility
If meander-like structures are used to enable stretching, then elasticity is improved, but design flexibility is restricted and strain is limited to certain directions
Solution Approach 1:
The patent employs asymmetric crack patterns and irregular geometric shapes rather than symmetric meander designs. These asymmetric features allow for more natural deformation paths and reduce the constraints on stretching directions, enabling the structure to accommodate strain in multiple orientations while maintaining electrical connectivity through the flexible connections between rigid islands.
Solution Approach 2:
The design transitions from two-dimensional planar meander patterns to three-dimensional flexible structures with out-of-plane deformation capabilities. By allowing the flexible substrate to buckle and deform in the third dimension, the structure achieves enhanced elasticity without being constrained to specific in-plane stretching directions, thereby reducing design restrictions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The Y-shaped patterned materials demonstrate significant elasticity, with the ability to stretch up to 70% while maintaining electrical conductivity, and withstand repeated strain cycles without fatigue, offering a reliable and cost-effective solution for engineering elasticity in previously inelastic materials.
Implementation Method 1
The Y-shaped motif throughout the plastic film allows for elasticity without preferential direction
Implementation Method 2
maintaining a percolating pathway for electrical conductivity
Data Source
AI summary
The present disclosure relates to how to engineer reversible elasticity in thin films and/or layers and/or substrates, using a repeated Y-shaped motif, which is cut out through the film and/or layer and/or substrate. As an example, using a 75 μm thick polyimide (PI) foil, macroscopic dog-bone shaped structures with a range of geometrical parameters of the Y shape have been prepared according to an embodiment of the present disclosure. The tensile strain response of the film at its point of fracture was then recorded. The structures were also confirmed using finite element modeling. Upon stretching, the PI ligaments locally deflect out of plane, allowing the foil to macroscopically stretch.