Assembly for and method of forming localized surface wrinkles
AssigneeGM Global Technology Operations LLC
InventorsTao Xie, Xingcheng Xiao, Ruomiao Wang, Joseph C. Simmer
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Abstract
An assembly including and method of forming arbitrary localized wrinkles upon a surface utilizing a shape memory polymer substrate and rigid overlay, wherein the geometrical distribution of the wrinkles is produced by recovering a lateral strain history within the substrate and buckling the overlay, and the localized wrinkles are used to create, among other things, optically three-dimensional engaging surfaces, structural colors, modified surface texturing, and haptic alerts.
Claims19
A method of forming localized wrinkles upon a surface, said method comprising:
- a. indenting a substrate at least partly formed of shape memory polymer, so that the substrate defines a first area experiencing purely compressive strain and a second area adjacent the first area and experiencing compressive and tensile strains;
- b. attaching a relaxed overlay to the substrate, so as to overlay the first and second areas;
- and define the surface;
- c. activating the polymer, so as to recover the strains;
- d. causing wrinkles to form in the overlay, as a result of recovering the tensile strain in the second area;
- and
- e. deactivating the polymer.
A method of measuring the cracking strain/stress of a nanoscopically thin overlay, said method comprising the steps of:
- a. indenting a substrate at least partly formed of shape memory polymer presenting a glass transition temperature, so that the substrate defines a first area experiencing a purely compressive strain, and a second area adjacent the first area and experiencing compressive and tensile strains;
- b. attaching the overlay to the substrate, so as to cover the first and second areas, and define the surface;
- c. activating the polymer, so as to recover the strains;
- d. determining the formation of a crack within the overlay, as a result of recovering the tensile strain in the second area;
- and
- e. observing and measuring the crack relative to the strains, when the crack is formed.
An assembly for forming localized wrinkles within a continuous surface, said assembly comprising:
- a substrate at least partially formed of a shape memory polymer presenting a glass transition temperature and first elastic modulus when activated, being plastically indented so as to define a first area experiencing a purely compressive strain, and a second area adjacent the first area and experiencing compressive and tensile strains, when the polymer is deactivated, and operable to recover a the strains when the polymer is activated;
- and
- a relaxed overlay fixedly attached to and configured to cover the first and second areas, and defining the surface, a second elastic modulus, and a height,
- wherein the second elastic modulus is greater than the first modulus, and the moduli, height, and strains are cooperatively configured to cause buckling in the overlay, when the polymer is activated and recovers the strains.
Dependencies are inferred from the claim text.