Foldable apparatus, foldable substrate, and methods of making
Foldable apparatus comprise a foldable substrate foldable about an axis and a substrate thickness defined between a first major surface and a second major surface. The foldable substrate comprises a central portion positioned between a first portion and a second portion. The first portion comprising a substrate thickness. The central portion comprises a central thickness that is less than the substrate thickness. In some embodiments, a width of central portion is about 45 millimeters or less. Methods of making a foldable apparatus comprise forming a recess in a first major surface of the foldable substrate. In some embodiments, methods comprise chemically strengthening the foldable substrate.
1 . A foldable apparatus comprising a foldable substrate foldable about an axis extending in a direction of a width of the foldable substrate, the foldable substrate further comprising:
a substrate thickness defined between a first major surface and a second major surface opposite the first major surface, wherein the foldable substrate is formed of an amorphous glass material;
a first portion comprising the substrate thickness and a first surface area of the first major surface;
a second portion comprising the substrate thickness and a third surface area of the first major surface; and
a central portion comprising a central thickness defined between a first central surface area and the second major surface opposite the first central surface area, the first central surface area attaching the first surface area to the third surface area, a width of the central portion, extending from the first portion to the second portion, is about 45 millimeters or less, and the central thickness is less than the substrate thickness,
wherein the central portion is positioned between the first portion and the second portion in a direction of a length of the foldable substrate that is perpendicular to the direction of the width of the foldable substrate, and the foldable apparatus comprises a neutral stress configuration when the foldable apparatus is in a bent configuration, wherein:
the foldable substrate of the foldable apparatus comprises an effective minimum bend radius in a range from about 1 millimeter to about 10 millimeters,
the width of the central portion is in a range from about 2.8 times the effective minimum bend radius to about 6 times the effective minimum bend radius,
the substrate thickness is in a range from about 125 micrometers to about 200 micrometers,
the central thickness is in a range from about 10 micrometers to about 40 micrometers, and
the substrate is chemically strengthened so that the first portion and the second portion each comprise a maximum tensile stress of about 100 MPa or less.
2 . The foldable apparatus of claim 1 , wherein the foldable apparatus comprises a polymer-based portion positioned in a recess defined between the first central surface area of the central portion and a first plane that the first major surface extends along, and a movement of the foldable apparatus from a flat configuration to the neutral stress configuration corresponds to a maximum magnitude of a deviatoric strain of the polymer-based portion in a range from about 1% to about 8%.
3 . The foldable apparatus of claim 2 , wherein the maximum magnitude of the deviatoric strain is in a range from about 2% to about 6%.
4 . The foldable apparatus of claim 1 , wherein the foldable substrate achieves an effective bend radius of 5 millimeters.
5 . The foldable apparatus of claim 1 , wherein the width of the central portion is in a range from about 2.8 millimeters to about 40 millimeters.
6 . The foldable apparatus of claim 1 , wherein the central thickness is in a range from about 0.5% to about 13% of the substrate thickness.
7 . The foldable apparatus of claim 1 , wherein the substrate thickness is at least 71 micrometers greater than about 4 times the central thickness.
8 . A method of making a foldable apparatus comprising:
forming a recess in a first major surface of a foldable substrate that forms a first central surface area of a central portion attaching a first portion to a second portion, wherein the first portion comprises a first surface area and a second surface area opposite the first surface area, the second portion comprises a third surface area and a fourth surface area opposite the third surface area, the foldable substrate comprises a second major surface comprising the second surface area and the fourth surface area, and the foldable substrate comprises a first major surface opposite the second major surface, the first major surface comprising the first surface area and the third surface area; and
curing a polymer-based portion disposed between the first portion and the second portion, wherein the foldable apparatus is in a bent configuration during the curing, wherein a movement of the foldable apparatus from a flat configuration to a neutral stress configuration corresponds to a maximum magnitude of a deviatoric strain of the polymer-based portion in a range from about 1% to about 8%, and the foldable apparatus comprise the foldable apparatus of claim 1 .
9 . The method of claim 8 , further comprising chemically strengthening the first central surface area of the central portion, the first surface area, the third surface area, and the second major surface.
10 . The method of claim 8 , wherein the maximum magnitude of the deviatoric strain is in a range from about 2% to about 6%.
11 . The method of claim 8 , wherein the polymer-based portion expands as a result of curing.
12 . The method of claim 8 , wherein the polymer-based portion comprises a negative coefficient of thermal expansion.
13 . The method of claim 12 , wherein the polymer-based portion comprises particles of one or more of copper oxide, beta-quartz, a tungstate, a vanadate, a pyrophosphate, or a nickel-titanium alloy.
14 . The method of claim 8 , wherein curing the polymer-based portion comprises a ring-opening metathesis polymerization.