FOOD PACKAGING COMPRISING AT LEAST ONE METAMATERIAL

BACKGROUND

[001] Microwave energy can heat an entirety of at least one food item. However, conventional methods of using microwave energy to heat a food item have several drawbacks. For example, it can be difficult to control the amount of microwave energy that irradiates the food item.

SUMMARY

[002] Techniques are generally described that include methods and systems. An example food packaging includes packaging defining at least one chamber. The food packaging also includes at least one food item disposed in the at least one chamber. The food packaging further includes at least one metamaterial positioned at least proximate to the at least one chamber. The at least one metamaterial is configured to change from a first state to a second state. The at least one metamaterial includes a plurality of conductive shapes. The at least one metamaterial also includes a first sheet defining a first surface. The first surface includes some of the plurality of conductive shapes. The at least one metamaterial further includes a second sheet defining a second surface. The second surface includes some of the plurality of conductive shapes and is spaced further from the at least one chamber than the first surface. Finally, the at least one metamaterial also includes a hollow at least partially defined by the first and second sheets. The first and second surfaces are spaced by a first distance when the at least one metamaterial is in the first state. The first and second surfaces are spaced by a second distance that is greater than the first distance when the at least one metamaterial is in the second state. The at least one metamaterial reflects at least five times more microwave energy when the at least one metamaterial is in the second state than when the at least one metamaterial is in the first state.

[003] An example method to heat at least one food item includes positioning at least one food packaging in a microwave emitting device. The at least one food packaging includes packaging that at least partially defines at least one chamber. The at least one food packaging includes at least one metamaterial position at least proximate to the at least one chamber and at least one food item disposed in the at least one chamber. The at least one metamaterial includes a plurality of conductive shapes. The at least one metamaterial also includes a first sheet comprising a first surface. The first surface includes some of the plurality of conductive shapes. The at least one metamaterial further includes a second sheet comprising a second surface. The second surface includes at least some of a remainder of the plurality of conductive shapes and is spaced from the first surfaced by a first distance. The second surface is spaced further from the at least one chamber than the first surface. Finally, the at least one metamaterial includes a hollow at least partially defined by the first and second sheets, the hollow exhibiting a first volume. The method also includes, with the microwave emitting device, emitting microwave energy toward the at least one metamaterial of the at least one food packaging. Further, the method includes transmitting at least some of the microwave energy through the at least one metamaterial. Additionally, the method includes, responsive to emitting the microwave energy and transmitting at least some of the microwave energy through the at least one metamaterial, releasing at least one gas from within the at least one food packaging. The method also includes, responsive to releasing the at least one gas, increasing a volume of the hollow from the first volume to a second volume thereby increasing a distance between the first and second surfaces from the first distance to a second distance. Finally, the method includes, responsive to increasing the distance between the first and second surfaces from the first distance to the second distance, reflecting at least five times more of the microwave energy than when the first and second surfaces were spaced by the first distance.

Features from any of the disclosed embodiments may be used in combination with one another, without limitation. In addition, other features and advantages of the present disclosure will become apparent through consideration of the following detailed description and the accompanying drawings.

[005] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[006] The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several examples in accordance with the disclosure and are, therefore, not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings, in which:

FIG. 1A is a schematic cross-sectional view of a food packaging that includes at least one metamaterial when the metamaterial is in a first state;

FIG. IB is a schematic cross-sectional view of the food packaging of FIG. 1A when the metamaterial is in a second state;

FIG. 2 is a schematic cross-sectional view of a food packaging where the at least one food item that is disposed in the chamber is a gas source;

FIG. 3 is a schematic cross-sectional view of a food packaging that includes a gas source disposed in a chamber that is distinct from at least one food item that is disposed in the chamber;

FIG. 4 is a schematic cross-sectional view of a food packaging that includes a gas source disposed in a hollow;

FIG. 5 is a schematic cross-sectional view of a portion of a metamaterial that includes gas source disposed in the first or second sheet;

FIG. 6A is a schematic cross-sectional view of a food packaging that includes at least one retainer disposed in the hollow;

FIG. 6B is a schematic cross-sectional view of the food packaging of FIG. 6A after the at least one retainer has ruptured;

FIG. 7 is a schematic cross-sectional view of a food packaging that includes a metamaterial that includes at least one vent; FIG. 8 is a schematic cross-sectional view of a food packaging that includes at least one microwave susceptor;

FIGS. 9A and 9B are an isometric view and a schematic cross-sectional view, respectively, of a food packaging that includes a plurality of chambers;

FIGS. 10A and 10B are an isometric view and a schematic cross-sectional view, respectively, of a food packaging that includes a plurality of chambers;

FIG. 11 is a schematic cross-sectional view of a food packaging that includes a metamaterial having three sheets;

FIGS. 12A-12B illustrate a portion of a metamaterial that transitions from a first state to a second state by laterally shifting the first sheet relative to the second sheet;

FIGS. 13A-13D are plan views of some of the split ring resonators that can form the conductive shapes disclosed herein;

FIG. 14 is a flow chart of an example method of using any of the food packaging disclosed herein,

all arranged in accordance with at least some embodiments of the present disclosure.

DETAILED DESCRIPTION

[007] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative examples described in the detailed description, drawings, and claims are not meant to be limiting. Other examples may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different states, all of which are implicitly contemplated herein.

[008] This disclosure is drawn, inter alia, to methods, systems, products, devices, and/or apparatus generally related to food packaging that includes at least one metamaterial that is configured to change from a first state to a second state. In an example, the food packaging defines at least one chamber and includes at least one food item disposed in the chamber. The food packaging also includes at least one metamaterial at least proximate to the at least one chamber. The metamaterial includes a plurality of conductive shapes, a first sheet, and a second sheet. The first sheet defines a first surface that includes some of the plurality of conductive shapes. The second sheet defines a second surface that includes some of the plurality of conductive shapes. The second surface is spaced from the first surface by a first distance when the metamaterial is in the first state. The second surface is spaced further from the at least one chamber than the first surface. The metamaterial further includes a hollow at least partially defined by the first and second sheets. The hollow is configured to be expanded by a gas from a first volume when the metamaterial is in the first state to a second volume when the metamaterial is in a second state. The distance between the first and second surfaces also increases when the metamaterial is in the second state. The at least one metamaterial reflects at least five times more microwave energy when the metamaterial is in the second state.

[009] FIG. 1A is a schematic cross-sectional view of a food packaging 100 that includes at least one metamaterial 102 when the metamaterial 102 is in the first state, according to at least one example. The food packaging 100 defines at least one chamber 104. For example, the food packaging 100 can include packaging 106 that partially defines the chamber 104. The packaging 106 can include one or more walls that at least partially defines the chamber 104. The metamaterial 102 includes a plurality of conductive shapes 108, a first sheet 110, and a second sheet 112. The first sheet 110 defines a first surface 114 that includes some of the conductive shapes 108 and the second sheet 112 defines a second surface 116 that also includes some of the conductive shapes 108. The second surface 116 is spaced further from the chamber 104 than the first surface 114. The metamaterial 102 further includes a hollow 118 that is defined by the first sheet 110 and the second sheet 112 and is configured to be expanded by a gas. As will be discussed in more detail below, the metamaterial 102 is configured to transition from the first state to a second state (FIG. IB). The food packaging 100 can further include at least one food item 120 disposed in the chamber 104.

[010] The food packaging 100 can exhibit any suitable shape. For example, the food packaging 100 can form an enclosure, a tray, a box, a bag, a bottle, a plate, a bowl, a device exhibiting a generally tubular shape, a device exhibiting a pocket-like shape, etc. In another example, the food packaging 100 can define a single chamber 104 or a plurality of chambers 104 (see FIGS. 9 A - 10B). In another example, the packaging 106 that at least partially defined the chamber 104 can be formed from any suitable microwaveable material, such as a microwaveable polymer (e.g., polypropylene).

[011] The metamaterial 102 is configured to control the amount of microwave energy that reaches the chamber 104. For example, the metamaterial 102 can be at least partially transparent (e.g., completely transparent) to microwave energy when the metamaterial 102 is in the first state. Additionally, the metamaterial 102 can reflect at least 5 times more microwave energy when the metamaterial 102 is in the second state than when in the first state. As such, the metamaterial 102 is positioned at least proximate to the chamber 104 such that the metamaterial 102 can control the amount of microwave energy that reaches the chamber 104. For example, the metamaterial 102 at least partially defines the chamber 104. It is noted that reflecting the microwave energy with the metamaterial 102 can increase the amount of microwave energy that is present in a microwave oven. As such, reflecting the microwave energy can cause other portions of the food packaging 100 that are not covered by the reflecting metamaterial 102 (e.g., second food item 920b of FIG. 9B) can receive increased amounts of the microwave energy.

[012] The conductive shapes 108 of the metamaterial 102 are configured to interact with microwave energy (e.g., transmit or reflect microwave energy). For example, as will be discussed in more detail below, the conductive shapes 108 are selected to controllably transmit or reflect microwave energy depending on the spacing between the first and second surfaces 1 14, 1 16. As such, the conductive shapes 108 can exhibit any shape or geometry that allows that conductive shapes 108 to controllably transmit or reflect microwave energy. Examples of conductive shapes 108 that can controllably transmit or reflect microwave energy includes split ring resonators, such as the split ring resonators shown in FIGS. 12A-12D, loops, or another suitable shape.

[013] The conductive shapes 108 can exhibit a maximum lateral dimension in a range from about 1 mm to about 20 mm, such as about 1 mm to about 3 mm, about 2 mm to about 4 mm, about 3 mm to about 5 mm, about 4 mm to about 6 mm, about 5 mm to about 7 mm, about 6 mm to about 8 mm, about 7 mm to about 10 mm, about 9 mm to about 12 mm, about 1 1 mm to about 14 mm, about 13 mm to about 17 mm, or about 16 mm to about 20 mm. The maximum lateral dimension of the conductive shape 108 can depend on a number of different factors. For example, the maximum lateral dimension of the conductive shape 108 can depend on the frequency of the microwave energy that the conductive shape 108 is configured to interact with (e.g., smaller maximum dimensions are better at interacting with microwave energy exhibiting larger frequencies). For instance, a conductive shape 108 that is configured to interact with microwave energy exhibiting a frequency of about 900 MHz to about 930 MHz (e.g., a commercial or industrial microwave oven) may exhibit a maximum lateral dimension of about 3 mm to about 20 mm. In another instance, a conductive shape 108 that is configured to interact with microwave energy exhibiting a frequency of about 2.4 GHz to about 2.5 GHz (e.g., a consumer microwave oven) may exhibit a maximum lateral dimension of about 1 mm to about 10 mm. In another example, the maximum lateral dimension of the conductive shapes 108 can depend on the shape and geometry of the conductive shapes 108. For instance, the maximum lateral dimension of a single split ring resonator (e.g., split ring resonator 1208a of FIG. 12A) can be about 3 times larger than a double split ring resonator (e.g., split ring resonator 1208d of FIG. 12D). In another example, the maximum lateral dimension of the conductive shapes 108 can depend on the arrangement of the conductive shapes 108 on the first and second surface 1 14, 1 16, the type of material that is used to form the conductive shapes 108, etc.

[014] The conductive shapes 108 can be formed from any suitable conductive material, such as a metallic foil. In an example, the conductive shapes 108 can be formed from aluminum foil because aluminum is a relatively lightweight metal, exhibits a high conductivity, is easy to shape, and is cheap. In another example, the conductive shapes 108 can be formed from silver, copper, gold, molybdenum, zinc, brass, carbon (e.g., oriented carbon fibers), nickel, iron, another electrically-conductive material, alloys thereof, or combinations thereof.

[015] The conductive shapes 108 can exhibit a thickness in a range from about 500 nm to about 10 μπι, such as in a range from about 500 nm to about 1 μπι, about 750 nm to about 1.5 μπι, about 1 μπι to about 2 μπι, about 1.5 μπι to about 3 μπι, about 2 μπι to about 4 μπι, about 3 μπι to about 6 μπι, or about 5 μπι to about 10 μπι. As such, the conductive shapes 108 can be a foil because foils exhibit a low mass and can be formed using simple machinery (e.g., hot or cold foil stamping machines) and decreases the costs of the food packaging 100.

[016] As previously discussed, the metamaterial 102 also includes the first and second sheets 1 10, 1 12 that define the first and second surfaces 1 14, 1 16, respectively. The first and second surfaces 114, 1 16 each include some of the conductive shapes 108. For example, the first and second surfaces 1 14, 1 16 can include conductive shapes 108 attached thereto, at least partially disposed therein such that the conductive shapes 108 extend outwardly therefrom, or disposed therein such that the conductive shapes 108 define a portion of the first and second surfaces 1 14, 1 16.

[017] It is noted that the first surface 1 14 of the first sheet 1 10 can include the bottom surface of the first sheet 1 10 (e.g., the surface of the first sheet 1 10 that is closest to the chamber 104) or the upper surface of the first sheet 1 10 (e.g., the surface of the first sheet 1 10 that is farthest from the chamber 104). Similarly, the second surface 1 16 of the second sheet 1 12 can include the bottom surface of the second sheet 1 12 (e.g., the surface of the second sheet 1 12 that is closest to the chamber 104) or the upper surface of the second sheet 1 12 (e.g., the surface of the second sheet 1 12 that is farthest from the chamber 104).

[018] The conductive shapes 108 can be arranged in periodic patterns on the first and second surfaces 1 14, 1 16. For example, the conductive shapes 108 can be arranged in a plurality of substantially parallel rows in which each of the conductive shapes 108 in each row exhibits a center-to-center spacing C that depends on the maximum lateral dimension of the conductive shapes 108. For example, the center-to-center spacing C can be in a range from about 0.1 to about 5 times the maximum lateral dimension of the conductive shapes 108, such as in a range from about 0.2 to about 4, about 0.1 to about 0.5, about 0.25 to about 0.75, about 0.5 to about 1, about 0.75 to about 1.5, about 1 to about 2, about 1.5 to about 3, about 2 to about 4, or about 3 to about 5 times the maximum dimension of the conductive shapes 108. In another example, the center-to-center spacing C can be about 0.1 mm to about 50 mm, such as in a range from about 0.1 mm to about 1 mm, about 0.5 mm to about 1.5 mm, about 1 mm to about 2 mm, about 1.5 mm to about 3 mm, about 2 mm to about 4 mm, about 3 mm to about 5 mm, about 4 mm to about 6 mm, about 5 mm to about 8 mm, about 7 mm to about 10 mm, about 9 mm to about 12 mm, about 1 1 mm to about 15 mm, about 14 mm to about 20 mm, about 19 mm to about 25 mm, about 20 mm to about 40 mm, or about 30 mm to about 50 mm. The center-to-center spacing C can affect the density of the conductive shapes 108 on the first and second surfaces 1 14, 1 16 which, in turn, can affect how the conductive shapes 108 interact with the microwave energy.

[019] In an example, the first and second sheet 1 10, 1 12 can be formed from a material that is at least partially transparent to microwave energy. In another example, the first and second sheets 1 10, 1 12 can be formed from a microwaveable material. In another example, the first and second sheet 1 10, 1 12 can be formed from a non-conductive (e.g., exhibits a resistivity greater than about 1 Ω-m) and non-magnetic material since a conductive or magnetic material can affect how the metamaterial 102 interacts with the microwave energy. In another example, the first and second sheet 1 10, 1 12 can be formed from a polymer, such as polypropylene.

[020] As previously discussed, the hollow 1 18 is at least partially defined by the first and second sheets 1 10, 1 12. In an example, the hollow 1 18 is substantially only defined by the first and second sheets 1 10, 1 12. In such an example, the first and second sheets 1 10, 1 12 can be directly coupled together. In another example, as illustrated, the hollow 1 18 is defined by the first and second sheets 1 10, 1 12 and at least one hollow wall 122 that extends between the first and second sheets 1 10, 1 12. In an example, the hollow wall 122 can be configured to expand when the volume of the hollow 1 18 increases thereby allowing the distance between the first and second surfaces 1 14, 1 16.

[021] The hollow 1 18 is configured to be expanded by at least one gas. In particular, a volume of the hollow 1 18 is configured to be expanded from a first volume to a second volume (FIG. IB) by the at least one gas. As such, one or more of the first sheet 1 10, the second sheet 1 12, or the at least one hollow wall 122 is configured to expand (e.g., stretch) as the hollow 1 18 is expanded. For example, one or more of the first sheet 1 10, the second sheet 1 12, or the at least one hollow wall 122 is formed from an elastic material, includes one or more wrinkles that can be unfolded, etc.

[022] As previously discussed, the metamaterial 102 is configured to transition from a first (e.g., initial) state to a second state. FIG. 1A illustrates the metamaterial 102 in the first state. The metamaterial 102 is configured to be at least partially transparent to microwave energy (e.g., microwave energy exhibiting a frequency of about 900 MHz to about 930 MHz or about 2.4 GHz to about 2.5 GHz) when the metamaterial 102 is in the first state. As such, the metamaterial 102 allows the microwave energy to heat the at least one food item 120 disposed in the chamber 104 when the metamaterial 102 is in the first state.

[023] The metamaterial 102 is in the first state when the first and second surfaces 1 14, 1 16 are spaced by the first distance Dl . The first distance Dl can be in a range from 0 (e.g., the first and second surfaces are touching) to about 2 mm, such as in a range from 0 to about 0.1 mm, about 0.05 mm to about 0.15 mm, about 0.1 mm to about 0.2 mm, about 0.15 mm to about 0.3 mm, about 0.2 mm to about 0.4 mm, about 0.3 mm to about 0.5 mm, about 0.4 mm to about 0.6 mm, about 0.5 mm to about 0.8 mm, about 0.7 mm to about 1 mm, about 0.9 mm to about 1.5 mm, or about 1.4 mm to about 2 mm. The first distance Dl can be selected based on how much microwave energy should be initially transmitted through the metamaterial 102, the maximum dimension of the conductive shapes 108, the shape of the conductive shapes 108, the arrangement of the conductive shapes 108, the frequency of microwave energy that the metamaterial 102 is configured to transmit, etc. [024] The metamaterial 102 can transition from the first state to the second state by increasing the volume of the hollow 1 18 with at least one gas and increasing the distance between the first and second surfaces 1 14, 116. FIG. IB is a schematic cross-sectional view of the food packaging 100 of FIG. 1A when the metamaterial 102 is in the second state, according to at least one example. The metamaterial 102 changes from the first state to the second state because the metamaterial 102 allows at least some microwave energy to be transmitted therethrough. For example, the microwave energy can heat one or more gas sources to release at least one gas that can increase a pressure in the hollow 1 18. The increased pressure in the hollow 1 18 increase, the volume of the hollow 1 18 and the distance between the first and second surfaces 1 14, 1 16. Increasing the distance between the first and second surfaces 1 14, 1 16 changes the resonant frequency of the metamaterial 102. The distance between the first and second surfaces 1 14, 1 16 changes until the metamaterial 102 is in the second state.

[025] The metamaterial 102 is in the second state when the metamaterial reflects at least 5 times more of the microwave energy than when the metamaterial 102 is in the first state. For example, the metamaterial 102 may reflect at least 6, at least 7, at least 8, at least 9, at least 10, at least 15, about 5 to about 10, or about 7.5 to about 15 times more microwave energy when the metamaterial 102 is in the second state that when the metamaterial 102 is in the first state.

[026] The metamaterial 102 is in the second state when the first and second surfaces 1 14, 1 16 are separated by a second distance D2. For example, the second distance D2 can be in a range from about 0.5 mm to about 10 mm greater than the first distance Dl, such as in a range from about 1 mm to about 2 mm, about 1.5 mm to about 3 mm, about 2 mm to about 4 mm, about 3 mm to about 5 mm, about 4 mm to about 6 mm, about 5 mm to about 7 mm, about 6 mm to about 8 mm, or about 7 mm to about 10 mm greater than the first distance Dl . In another example, the second distance D2 corresponds to the maximum lateral dimension of at least one of the conductive shapes 108 (e.g., the maximum lateral dimension 1244a-e of FIGS. 12A-12D. In such an example, the second distance D2 can be about 0.1 to about 1 times the maximum dimension of the conductive shapes 108, such as in ranges of about 0.1 to about 0.3, about 0.2 to about 0.4, about 0.3 to about 0.5, about 0.4 to about 0.6, about 0.5 to about 0.7, about 0.6 to about 0.8, about 0.7 to about 0.9, or about 0.8 to about 1 times the maximum dimension of the conductive shapes 108. The second distance D2 can depend on, the first distance Dl, the maximum lateral dimension of the conductive shapes 108, the shape of the conductive shapes 108, the arrangement of the conductive shapes 108, the frequency of microwave energy that the metamaterial 102 is configured to reflect, etc.

[027] The metamaterial 102 allows significantly less microwave energy to be transmitted therethrough when the metamaterial 102 is in the second state compared to when the metamaterial 102 is in the first state. The metamaterial 102 can be configured such that the amount of microwave energy that reaches the food item 120 when the metamaterial 102 is in the second state is sufficient to decrease the rate that the temperature of the food item 120 increases, maintain the temperature of the food item 120 at or near a preselected temperature (e.g., about 50 °C to about 100 °C, about 75 °C to about 125 °C, about 100 °C to about 150 °C, about 125 °C to about 175 °C, or about 150 °C to about 200 °C), or cause the temperature of the food item 120 to decrease.

[028] FIGS. 1A-1B illustrate that the metamaterial 102 transitions from the first state to the second state by increasing the distance between the first and second surfaces 1 14, 1 16. However, it is noted that the metamaterial 102 can also transition from the first state to the second state by shifting the second sheet 1 12 in a lateral direction relative to the first sheet 1 10 instead of or in conjunction with increasing the distance between the first and second surfaces 1 14, 1 16. The metamaterial 102 can be configured to shift the second sheet 1 12 in the lateral direction relative to the first sheet 1 10 using any suitable method. For example, the at least one hollow wall 122 and can be folded in a manner that causes the second sheet 1 12 to shift laterally relative to the first sheet 1 10 when the hollow wall 122 unfolds.

[029] In an example, as shown in FIGS. 1A and IB, the first and second sheets 1 10, 1 12 are substantially planar. In such an example, the first and second surfaces 1 14, 1 16 can be parallel. As such, the first or second distances Dl, D2 are substantially uniform. In another example, the first or second sheets 1 10, 1 12 can exhibit a curvature. In such an example, the first or second distances Dl, D2 can vary (e.g., the first and second surfaces 1 14, 1 16 are not parallel) or can be the same (e.g., the first and second surfaces 1 14, 1 16 are parallel).

[030] In an example, the metamaterial 102 is disposable (e.g., configured for single use). In such an example, the first and second sheets 1 10, 1 12 can be formed from a biodegradable polymer, such as polylactic acid. In another example, the metamaterial 102 is reusable. In such an example, the metamaterial 102 can form a durable lid that can be coupled to a container, such as a storage container (e.g., a Tupperware container).

[031] The food packaging 100 can include at least one gas source (not shown) that is positioned in the food packaging 100 such that a gas released by the gas source can increase the volume of the hollow 1 18. In an example, the gas source includes a liquid that exhibits a phase changes (e.g., liquid to gas). An example of a liquid that can form the gas source includes water or salt water. In another example, the gas source can include at least one generally-regarded-as-safe (GRAS) alcohol.

[032] FIG. 2 is a schematic cross-sectional view of a food packaging 200 where the at least one food item 220 is the gas source, according to at least one example. Similar to the food packaging 100 of FIGS. 1A and IB, the food packaging 200 includes packaging 206 that at least partially define the chamber 204 and the food item 220 is disposed in the chamber 204. The food packaging 200 also includes a metamaterial 202 positioned at least proximate to the chamber 204 that is configured to transition from a first state to a second state. The metamaterial 202 includes a plurality of conductive shapes 208, a first sheet 210, and a second sheet 212. The first sheet 210 defines a first surface 214 that includes some of the conductive shapes 208 and the second sheet 212 defines a second surface 216 that includes some of the conductive shapes 208. The metamaterial 202 further comprises a hollow 218 that is defined by the first and second sheets 210, 212.

[033] As previously discussed, the food item 220 is the gas source. As such, the food item 220 can include any food item that has water or another suitable gas source. For example, the food item 220 can include meats, fruits, vegetables, certain grains (e.g., precooked noodles, bread, etc.), or any other suitable food item. [034] The food item 220 is separated from the hollow 218 by the first sheet 210. As such, the first sheet 210 can be configured to be at least semi-permeable to the at least one gas (e.g., steam) released by the food item 220 can enter the hollow 218. In an example, the first sheet 210 can define at least one hole 224, such as a plurality of holes 224, extending therethrough such that the gas released by the food item 220 can enter the hollow 218. The at least one hole 224 is sufficiently large that a pressure gradient between the chamber 204 and the hollow 218 is not large enough to cause the first sheet 210 to rupture. For example, the at least one hole 224 is sufficiently large that the pressure in the chamber 204 and the pressure in the hollow 218 are substantially the same.

[035] FIG. 3 is a schematic cross-sectional view of a food packaging 300 that includes a gas source 326 disposed in a chamber 304 that is distinct from at least one food item 320, according to at least one example. Similar to the food packaging 100 and 200 of FIGS. 1A-2, the food packaging 300 includes packaging 306 that at least partially define the chamber 304 and the food item 320 is disposed in the chamber. The food packaging 300 also includes a metamaterial 302 positioned at least proximate to the chamber 304 that is configured to transition from a first state to a second state. The metamaterial 302 includes a plurality of conductive shapes 308, a first sheet 310, and a second sheet 312. The first sheet 310 defines a first surface 314 that includes some of the conductive shapes 308 and the second sheet 312 defines a second surface 316 that includes some of the conductive shapes 308. The metamaterial 302 further comprises a hollow 318 that is defined by the first and second sheets 310, 312.

[036] The gas source 326 (e.g., water) is distinct from (e.g., outside of) the food item 320. In an example, the gas source 326 is distinct from the food item 320 because the food item 320 is saturated with water. In another example, the gas source 326 is distinct from the food item 320 because the food item 320 is enclosed in a barrier (e.g., water resistant barrier) which substantially prevents the gas source 326 from entering the food item 320. In another example, the gas source 326 is enclosed in a rupturable barrier. The rupturable barrier can be configured to rupture after the gas source 326 begins release steam. [037] FIG. 4 is a schematic cross-sectional view of a food packaging 400 that includes a gas source 426 disposed in a hollow 418, according to at least one example. Similar to the food packaging 100, 200, 300 of FIGS. 1A-3, the food packaging 400 includes packaging 406 that at least partially define the chamber 404 and a food item 420 disposed in the chamber 404. The food packaging 400 also includes a metamaterial 402 positioned at least proximate to the chamber 404 that is configured to transition from a first state to a second state. The metamaterial 402 includes a plurality of conductive shapes 408, a first sheet 410, and a second sheet 412. The first sheet 410 defines a first surface 414 that includes some of the conductive shapes 408 and the second sheet 412 defines a second surface 416 that includes some of the conductive shapes 408. The metamaterial 402 further comprises a hollow 418 that is defined by the first and second sheets 410, 412.

[038] In an example, since the gas source 426 is disposed in the hollow 418, the first sheet 410 may not define at least one hole therein since the gas source is already present in the hollow 418. In another example, the first sheet 410 can define at least one hole (e.g., the hole 324 of FIG. 3), such as when the food packaging 400 includes additional gas sources disposed in the chamber 404. In such an example, the gas source 426 can be free to flow through the hole or the food packaging 400 can include a rupturable barrier (not shown) that prevents the gas source 426 from flowing through the hole. The rupturable barrier can restrict the flow of the gas source 426 by obstructing the holes or at least partially defining an enclosure. The rupturable barrier can be configured to rupture when the gas source 426 transitions from a liquid into a gas.

[039] FIG. 5 is a schematic cross-sectional view of a portion of a metamaterial 502 that includes a gas source 526 disposed in the first or second sheet 510, 512, according to at least one example. The metamaterial 502 is configured to transition from a first state to a second state. The metamaterial 502 includes a plurality of conductive shapes 508, the first sheet 510, and the second sheet 512. The first sheet 510 defines a first surface 514 that includes some of the conductive shapes 508 and the second sheet 512 defines a second surface 516 that includes some of the conductive shapes 508. The metamaterial 502 also includes a hollow 518 defined by the first sheet 510 and the second sheet 512. [040] The first or second sheets 510, 512 define a plurality of cavities 528. Each of the plurality of cavities 528 can be at least partially occupied by the gas source 526. When the metamaterial 502 is exposed to microwave energy, the gas source 526 that is disposed in the cavities 528 releases at least one gas. Releasing the gas in the cavities 528 can increase the pressure inside the cavities 528 until the cavities 528 rupture, thereby releasing the gas into the hollow 518. To ensure that the cavities 528 release the gas into the hollow 518, the cavities 528 can be positioned closer to a surface of the first or second sheet 510, 512 that defines the hollow 518 than a surface of the first or second sheet 510, 512 that does not define the hollow 518.

[041] In an example, each of the cavities 528 exhibits substantially the same distance d. In such an example, each of the cavities 528 can rupture at or about the same time. Rupturing each of the cavities 528 at or about the same time can cause the metamaterial 502 to quickly and suddenly transition from the first state to the second state. In another example, at least some of the cavities 528 exhibit a distance d that varies such that the cavities rupture at different times. Rupturing the cavities 528 at different times can cause the metamaterial 502 to gradually transition from the first state to the second state.

[042] As previously discussed, FIGS. 2-5 illustrate different gas sources. It is noted that the food packaging disclosed herein can include only one of the gas sources illustrated in FIGS. 2-5 or can include a combination of the gas sources illustrated in FIGS. 2-5. It is also noted that other gas sources can be used in any of the food packaging disclosed herein. For example, any of the food packaging disclosed herein can include packaging that defines a plurality of cavities that are at least partially occupied with the gas source. In another example, any of the food packaging disclosed herein can include a plurality of microspheres disposed therein (e.g., disposed in a chamber or a hollow). Each of the microspheres can define a cavity that is at least partially occupied by the gas source. Heating the microspheres can cause a pressure in the cavities of the microsphere to increase and rupture the microspheres.

[043] FIG. 6A is a schematic cross-sectional view of a food packaging 600 that includes at least one retainer 630 disposed in the hollow 618, according to at least one example. Similar to the food packaging 100, 200, 300, and 400 of FIGS. 1A-4, the food packaging 600 defines at least one chamber 604 and includes a metamaterial 602 and at least one food item 620 disposed in the chamber 604. The metamaterial 602 includes a plurality of conductive shapes 608, a first sheet 610 defining a first surface 614, a second sheet 612 defining a second surface 616, and a hollow 618 defined by the first and second sheets 610, 612.

[044] The metamaterial 602 also includes the at least one retainer 630. The retainer 630 is configured to prevent the metamaterial 602 from transitioning into the second state until the pressure within the hollow is at or about a selected pressure. The selected pressure is greater than a pressure required to transition a substantially similar metamaterial that does not include at least one retainer into its second state. For example, the retainer 630 is coupled to surfaces of the first and second sheet 610, 612 that define the hollow 618 (e.g., the first and second surfaces 614, 616). The retainer 630 exhibits an initial length L that is equal to or greater than the first distance Dl and less than the second distance D2 (FIG. 6B). As such, the retainer 630 prevents the metamaterial 602 from transitioning into the second state since the retainer 630 exhibits a length that is less than the second distance D2.

[045] As previously discussed, the retainer 630 is configured to allow the metamaterial 602 to transition to the second state when the pressure in the hollow 618 is at or near the selected pressure. For example, the retainer 630 can be configured to rupture when the pressure in the hollow 618 is at or near the selected pressure. FIG. 6B is a schematic cross-sectional view of the food packaging 600 of FIG. 6A after the at least one retainer 630 has ruptured, according to at least one example. Rupturing the retainer 630 enables the metamaterial 602 to suddenly transition to the second state. In another example, the retainer 630 can enable the metamaterial 602 to transition to the second state without rupturing. For instance, the retainer 630 can be formed from an elastic material that is configured to slowly stretch as the pressure in the hollow 618 increases until the length of the retainer 630 is equal to the second distance D2. Stretching the retainer 630 can cause the metamaterial to gradually transition to the second state. In another instance, the retainer 630 can become decoupled from one of the surfaces defining the hollow 618.

[046] In an example, the retainer 630 can be formed of any non-conductive and nonmagnetic material so that the retainer 630 does not substantially affect how the metamaterial interacts with the microwave energy. In another example, the retainer 630 can be formed of a substantially microwave transparent material such that the retainer 630 does not substantially affect the amount of microwave energy that is transmitted through the metamaterial 602. In another example, the retainer 630 can include one or more stress concentrators (e.g., the retainer 630 defines a slit, a notch, at least one perforation, etc.) that are configured to cause the retainer 630 to rupture at the selected pressure. In another example, the retainer 630 can be formed of a material that is configured to soften or melt at about 100 °C to about 200 °C. In such an example, the at least one gas that is present in the hollow 618 can weaken the retainer 630 thereby causing the retainer 630 to rupture since the at least one gas may exhibit such temperatures.

[047] In an example, the metamaterial 602 can include at least one second state retainer (not shown) that is configured to maintain the metamaterial 602 in the second state. The metamaterial 602 can include the at least one second state retainer in conjunction with or instead of the retainer 630. The second state retainer is formed of a rigid material and is not configured to rupture or fail. Additionally, the second state retainer exhibits a length that is equal or similar to the second distance D2. As such, the second state retainer is configured to maintain the metamaterial 602 in the second state. For example, the food packaging 600 may continue to release gas after the metamaterial 602 is in the second state since the gas source may still exhibit a temperature that is sufficient to release the gas. As such, the second state retainer can prevent the additional gas from transitioning the metamaterial 602 out of the second state.

[048] FIG. 7 is a schematic cross-sectional view of a food packaging 700 that includes a metamaterial 702 that includes at least one vent 732, according to at least one example. Similar to the food packaging 100, 200, 300, 400, and 600 of FIGS. 1A-4 and 6, the food packaging 700 can define a chamber 704 and include the metamaterial 702 and a food item 720 disposed in the chamber 704. The metamaterial 702 can include a plurality of conductive shapes 708, a first sheet 710 defining a first surface 714, a second sheet 712 defining a second surface 716, and a hollow 718 that is defined by the first and second sheet 710, 712.

[049] The second sheet 712 can also define the at least one vent 732. The vent 732 is configured to at least partially control the pressure that is present in the hollow 718. For example, the vent 732 allows some of the gas that is present in the hollow 718 to exit the hollow 718 and enter an atmosphere about the food packaging 700. However, the vent 732 exhibits a size that is sufficiently small that a pressure gradient can form between the hollow 718 and the atmosphere, thereby allowing the hollow 718 to increase in volume. As such, the vent 732 can increase the time required to transition the metamaterial 702 from the first state to the second state. Additionally, the vent 732 can decrease the likelihood that the metamaterial 702 ruptures since the vent 732 can reduce the pressure inside the hollow 718.

[050] In an example, any of the food packaging disclosed herein can include at least one microwave susceptor since, by itself, the microwave energy may be unable to generate Maillard or caramelization reactions in the food item. FIG. 8 is a schematic cross-sectional view of a food packaging 800 that includes at least one microwave susceptor 834, according to at least one example. Similar to the food packaging 100, 200, 300, 400, 600, and 700 of FIGS. 1A-4, 6, and 7, the food packaging 800 can include a metamaterial 802, a chamber 804, and at least one food item 820 disposed in the chamber 804. The microwave susceptor 834 can be disposed in the chamber 804 and positioned at least proximate to (e.g., contacting) the food item 820. The microwave susceptor 834 can include any material that is configured to absorb microwave energy and re-emit the microwave energy as heat. For example, the microwave susceptor 834 can include a metal foil, such as aluminum foil.

[051] In an example, as illustrated, the microwave susceptor 834 forms a sheet and the food item 820 is disposed on the microwave susceptor 834. In another example, the microwave susceptor 834 forms an enclosure and the food item 820 is disposed in the enclosure. In another example, the microwave susceptor 834 forms a tubular structure and the food item 820 is disposed in the tubular structure. In another example, the microwave susceptor 834 is attached to, at least one partially disposed in, or incorporated into the packaging 806 that defines the chamber 804.

[052] FIGS. 1A-4 and 6-8 illustrate food packaging that only includes a single chamber. However, it is understood that any of the food packaging disclosed herein can include a plurality of chambers. For example, FIGS. 9A and 9B are an isometric view and a schematic cross-sectional view, respectively, of a food packaging 900 that includes a plurality of chambers, according to at least one example. For example, the food packaging 900 includes packaging 906 that defines a first chamber 904a, a second chamber 904b, and, optionally, one or more additional chambers (not shown) 904c. The first chamber 904a can include at least one first food item 920a disposed therein and the second chamber 904b can include at least one second food item 920b disposed therein.

[053] In an example, the first and second food items 920a, 920b may need to be heated differently. For instance, the first and second food items 920a, 920b may need to be heated to different maximum temperatures, at different rates, etc. To facilitate the different heating requirements of the first and second food items 920a, 920b, the food packaging 900 can include a metamaterial 902 that is configured to interact with at least some of the microwave energy that enters the first chamber 904a and substantially not interact with the microwave energy that enters the second chamber 904b. For example, the metamaterial 902 can at least partially define the first chamber 904a and includes a plurality of conductive shapes 908. As such, at least some of the microwave energy that can enter the first chamber 904a must interact with (e.g., be transmitted or reflected by) the metamaterial 902. Additionally, the second chamber 904b is not defined by the metamaterial 902. As such, the metamaterial 902 can at least partially control the amount of microwave energy that enters the first chamber 904a but does not at least partially control the amount of microwave energy that enters the second chamber 904b.

[054] It is noted that in some microwave ovens, the microwave energy may converge on the food packaging 900 in a plurality of different directions. As such, the metamaterial 902 may interact with some of microwave energy that can enter the second chamber 904b even though the second chamber 904b is not defined by the metamaterial.

[055] FIGS. 10A and 10B are an isometric view and a schematic cross-sectional view, respectively, of a food packaging 1000 that includes a plurality of chambers, according to at least one example. Similar to the food packaging 1000 of FIGS. 10A and 10B, the food packaging 1000 can include packaging 1006 that define a first chamber 1004a, a second chamber 1004b, and, optionally, one or more additional chambers 1004c (not shown). The first chamber 1004a includes at least one first food item 1020a and the second chamber 1004b includes at least one second food item 1020b. The first chamber 1004a is at least partially defined by a first metamaterial 1002a and the second chamber 1004b is at least partially defined by a second metamaterial 1002b.

[056] In an example, the first and second food items 1020a, 1020b may need to be heated differently. To facilitate the different heating requirements of the first and second food items 1020a, 1020b, the first metamaterial 1002a is different than the second metamaterial 1002b. For example, the first metamaterial 1002a can include a plurality of first conductive shapes 1008a and the second metamaterial 1002b can include a plurality of second conductive shapes 1008b that are different than the first conductive shapes 1008a. As such, the first and second metamaterial 1002a, 1002b interact with microwave energy differently and, thereby, heat the first and second food items 1020a, 1020b differently.

[057] In another example, the first and second food items 1020a, 1020b may need to be heated the same. For instance, the first and second food items 1020a, 1020b can be the same food item or different food items that need to be heated the same. To facilitate the similar heating requirements of the first and second food items 1020a, 1020b, the first metamaterial 1002a is the same as the second metamaterial 1002b. As such, the first and second metamaterial 1002a, 1002b interact with microwave energy the same and, thereby, heat the first and second food items 1020a, 1020b the same.

[058] The metamaterials 102, 202, 302, 402, 502, 602, 702, 802, 902, and 1002 of FIGS. 1A-10B are illustrated as only including two sheets. However, any of the metamaterials disclosed herein can include three or more sheets. For example, FIG. 11 is a schematic cross-sectional view of a food packaging 1100 that includes a metamaterial 1102 having three sheets, according to at least one example. Similar to the food packaging 100, 200, 300, 400, 500, 700, 800, 900, 1000 of FIGS. 1A-4 and 6-10, the food packaging 1100 includes at least one chamber 1104, at least one metamaterial 1102, and at least one food item 1120. The metamaterial 1102 includes a plurality of conductive shapes 1108, a first sheet 1110, a second sheet 1112, a third sheet 1136, a first hollow 1118a defined by the first and second sheets 1110, 1112, and a second hollow 1118b defined by the first and third sheets 1110, 1136. The first sheet 11 10 defines a first surface 1114 that includes some of the conductive shapes 1108, the second sheet 1112 defines a second surface 1116 that includes some of the conductive shapes 1108, and the third sheet 1136 defines a third surface 1138 that includes some of the conductive shapes 1108. It is noted that increasing the number of sheets that forms the metamaterial 1102 can increase the amount of microwave energy that is reflected by the metamaterial 1102 when the metamaterial 1102 is in the second state.

[059] When the metamaterial 1102 is in the first state, the first and second surfaces 1114, 1116 can be separated by a first distance Dl and the first and third surfaces 1114, 1138 can be separated by a third distance D3. The third distance D3 can be similar to any of the first distances disclosed herein. When the metamaterial 1102 is in the second state, the first and second surfaces 1114, 1116 can be separated by a second distance (not shown) and the first and third surfaces 1114, 1138 can be separated by a fourth distance (not shown). The fourth distance can be similar to any of the second distances disclosed herein.

[060] As previously discussed, any of the metamaterials disclosed herein can be configured to transition from a first state to a second state by shifting at least one of the first or second sheets laterally. FIGS. 12A-12B illustrate a portion of a metamaterial 1202 that transitions from a first state to a second state by laterally shifting the first sheet 1210 relative to the second sheet 1212, arranged in accordance with at least some of the examples of the present disclosure. The first and second sheets 1210, 1212 of the metamaterial 1202 includes a first and second surface 1214, 1216, respectively, that each includes a plurality of conductive shapes 1208. [061] FIG. 12A illustrates the metamaterial 1202 when the metamaterial 1202 is in the first state. When the metamaterial 1202 is in the first state, the first and second surfaces 1214, 1216 are separated by a first distance Dl . The first distance D l can include any of the first distances disclosed herein.

[062] The conductive shapes 1208 exhibit a first lateral shift LS I when the metamaterial 1202 is in the first state. The first lateral shift LS I is the distance between a center of a conductive shape 1208 of the first sheet 1210 to a center of a conductive shape 1208 of second sheet 1212 that is immediately above the conductive shape 1208 of the first sheet 1210. The first lateral shift LS I is measured in a direction that is perpendicular from the first distance Dl . In an example, as shown, the first lateral shift LS I can be 0 (e.g., the conductive shape 1208 of the second sheet 1212 is immediately above the conductive shape 1208 of the first sheet 1212). In another example, the first lateral shift LS I can be in ranges of about 0 to about 0.5 the center-to-center spacing (C) of the conductive shapes 1208, such as in a range from about 0 to about 0.2C, about 0.1C to about 0.3C, 0.2C to about 0.4C, or about 0.3C to about 0.5C. The center-to-center spacing C of the conductive shapes 1208 can be the same as of similar to any of the center-to-center spacings disclosed herein. The first lateral shift LS I can be selected based on the amount of microwave energy that is to be transmitted or reflected when the metamaterial 1202 is in the first state.

[063] FIG. 12B illustrates the metamaterial 1202 when the metamaterial 1202 is in the second state. When the metamaterial 1202 is in the second state, the first and second surfaces 1214, 1216 are separated by a second distance D2. In an example, the second distance D2 can be the same as the first distance Dl . In another example, the second distance D2 can be greater than the first distance D2. In such an example, increasing the distance between the first and second surfaces 1214, 1216 to the second distance D2 can decrease the difference between the first lateral shift LS I to a second lateral shift LS2 (discussed below) required to transition the metamaterial 1202 from the first state to the second state. The second distance D2 can include any of the second distances disclosed herein. [064] When the metamaterial 1202 is in the second state, the conductive shapes 1208 exhibit a second lateral shift LS2. In an example, the second lateral shift LS2 can be greater than the first lateral shift LS I . In such an example, the second lateral shift LS2 can be at least 0.1C greater than the first lateral shift LS2, such as about O. IC to about 0.3C, or 0.2C to about 0.4C times greater than the first lateral shift LS2. In another example, the second lateral shift LS2 can in ranges of about 0 to about 0.2C, about 0.1C to about 0.3C, 0.2C to about 0.4C, or about 0.3C to about 0.5C. The second lateral shift LS2 can depend on the amount of microwave energy that is transmitted or reflected when the metamaterial 1202 is in the second state.

[065] As previously discussed, the conductive shapes disclosed herein can include split ring resonators. FIGS. 13A-13D are plan views of some of the split ring resonators that can form the conductive shapes disclosed herein, arranged in accordance with at least some of the embodiments disclosed herein.

[066] Referring to FIG. 13A, the split ring resonator 1308a can include a conductive material 1340a that forms a generally circular shape and defines a gap 1342a. A maximum lateral dimension 1344a of the split ring resonator 1308a is the diameter thereof.

[067] Referring to FIG. 13B, the split ring resonator 1308b can include a conductive material 1340b that forms a generally rectangular shape (e.g., generally square shape) and defines a gap 1342b. A maximum lateral dimension 1344b of the split ring resonator 1308b is the hypotenuse thereof.

[068] Referring to FIG. 13C, the split ring resonator 1308c can include a conductive material 1340c that forms a generally omega-like shape and defines a gap 1342c. The split ring resonator 1308c exhibits a maximum lateral dimension 1344c.

[069] Referring to FIG. 13D, the split ring resonator 1308d is a double split ring resonator. A double split ring resonator includes include a first conductive material 1340d and a second conductive material 1340e disposed inside the first conductive material 1340d. The first and second conductive material 1340d, 1340e form a generally circular shape that each defines a gap 1342d, 1342e, respectively. However, it is noted that the first and second conductive materials 1340d, 1340e can exhibit any suitable shape. A maximum lateral dimension 1344d of the split ring resonator 1308d is the diameter thereof. A maximum lateral dimension 1344e of the second conductive material 1340e is the diameter thereof.

[070] FIG. 14 is a flow chart of an example method 1400 of using any of the food packaging disclosed herein. The example method 1400 may include one or more operations, functions or actions as illustrated by one or more of blocks 1405, 1410, 1415, 1420, 1425, and/or 1430. The operations described in the blocks 1405 through 1430 may be performed in response to execution (such as by one or more processors described herein) of computer-executable instructions stored in a computer-readable medium, such as a computer-readable medium of a computing device or some other controller similarly configured.

[071] An example process may begin with block 1405, which recites "positioning at least one food packaging in a microwave emitting device." Block 1405 may be followed by block 1410, which recites "with the microwave emitting device, emitting microwave energy toward the at least one metamaterial of the at least one food packaging." Block 1410 may be followed by block 1415, which recites "transmitting at least some of the microwave energy through the at least one metamaterial." Block 1415 may be followed by block 1420, which recites "responsive to emitting the microwave energy and transmitting at least some of the microwave energy through the at least one metamaterial, releasing at least one gas from within the at least one food packaging." Block 1420 may be followed by block 1425, which recites "responsive to releasing the at least one gas, increasing a volume of the hollow from the first volume to a second volume thereby increasing a distance between the first and second surfaces from the first distance to a second distance." Block 1425 may be followed by block 1430, which recites "responsive to increasing the distance between the first and second surfaces from the first distance to the second distance, reflecting at least five times more of the microwave energy than when the first and second surfaces were spaced by the first distance."

[072] The blocks included in the described example methods are for illustration purposes. In some embodiments, the blocks may be performed in a different order. In some other embodiments, various blocks may be eliminated. In still other embodiments, various blocks may be divided into additional blocks, supplemented with other blocks, or combined together into fewer blocks. Other variations of these specific blocks are contemplated, including changes in the order of the blocks, changes in the content of the blocks being split or combined into other blocks, etc. In some examples, the method 1400 can include venting at least some of the at least one gas from the hollow through at least one vent defined by the second sheet.

[073] Block 1405 recites, "positioning at least one food packaging in a microwave emitting device." For example, block 1405 can include positioning the food packaging in a microwave oven that is configured to emit microwave energy exhibiting a frequency of about 900 MHz to about 930 MHz. In another example, block 1405 can include positioning the food packaging in a microwave oven that is configured to emit microwave energy exhibiting a frequency of about 2.4 GHz to about 2.5 GHz. In an example, block 1405 can include positioning any of the food packaging disclosed herein in the microwave oven.

[074] Block 1410 recites, "with the microwave emitting device, emitting microwave energy toward the at least one metamaterial of the at least one food packaging." For example, block 1410 includes emitting microwave energy exhibiting a frequency of about 900 MHz to about 930 MHz, about 2.4 GHz to about 2.5 GHz, or any other suitable frequency.

[075] Block 1415 recites, "transmitting at least some of the microwave energy through the at least one metamaterial." For example, during block 1415, the metamaterial of the food packaging is in the first state and, as such, the metamaterial is at least partially transparent to the microwave energy. For instance, the metamaterial of the food packaging may transmit 20% or more of the microwave energy therethrough, such as at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least 99% of the microwave energy.

[076] Block 1420 recites, "responsive to emitting the microwave energy and transmitting at least some of the microwave energy through the at least one metamaterial, releasing at least one gas from within the at least one food packaging." In such an example, block 1420 includes heating a gas source to a temperature that is sufficient to cause the gas source to release at least one gas via evaporation or boiling. In a particular example, block 1420 includes heating water to a boiling temperature thereof thereby releasing steam.

[077] In an example, block 1420 includes releasing the at least one gas from at least one gas source that is disposed in the at least one chamber and flowing at least some of the at least one gas from the chamber to the hollow using at least one hole defined by the first sheet. For instance, releasing the at least one gas from at least one gas source that is disposed in the at least one chamber includes releasing the at least one gas from the at least one food item. In another instance, releasing the at least one gas from at least one gas source that is disposed in the at least one chamber includes releasing the at least one gas from the at least one gas source that is disposed in the chamber and distinct from the at least one food item. In another instance, releasing the at least one gas from at least one gas source that is disposed in the at least one chamber includes releasing the at least one gas from the at least one food item and from the at least one gas source that is distinct from the at least one food item. In example, block 1420 includes releasing the at least one gas from the at least one gas source that is disposed in the hollow. In another example, block 1420 includes releasing the at least one gas in a plurality of cavities that are defined by the first sheet or the second sheet. In such an example, releasing the at least one gas in a plurality of cavities that are defined by the first sheet or the second sheet includes rupturing at least some of the plurality of cavities. In another example, block 1420 includes releasing the at least one gas from at least two of the at least one gas source that is disposed in the at least one chamber, the at least one gas source that is disposed in the hollow, a plurality of cavities that are defined by the first sheet or the second sheet, or another suitable gas source.

[078] Block 1425 recites, "responsive to releasing the at least one gas, increasing a volume of the hollow from the first volume to a second volume thereby increasing a distance between the first and second surfaces from the first distance to a second distance." For example, at least some of the gas that was released in block 1425 can increase the volume of the hollow.

[079] Block 1430 recites, "responsive to increasing the distance between the first and second surfaces from the first distance to the second distance, reflecting at least five times more of the microwave energy than when the first and second surfaces were spaced by the first distance." For example, block 1425 can cause the metamaterial to transition from the first state to the second state. As previously discussed, the metamaterial reflects more of the microwave energy when the metamaterial is in the second state compared to when the metamaterial is in the first state. The change in the reflectivity of the metamaterial is caused by changing the resonant frequency of the metamaterial. In an example, Block 1430 includes reflecting at least ten times more of the microwave energy than when the first and second surfaces were spaced by the first distance.

[080] In an example, the method 1400 can include, before increasing a volume of the hollow from the first volume to a second volume, restricting expansion of the volume of the hollow using at least one retainer that is coupled to the first sheet and the second sheet, the at least one retainer exhibiting an initial length that is less than the second distance. In such an example, the method 1400 can include rupturing the at least one retainer when a pressure in the hollow is at or near a selected pressure or stretching the at least one retainer from the initial length to final length, where the final length is the same as, similar to, or greater than the second distance.

[081] In an example, the method 1400 can include venting at least some of the at least one gas from the hollow through at least one vent defined by the second sheet. In such an example, the method 1400 can include increasing the pressure in the hollow even though some of the gas is vented through the at least one vent.

[082] The present disclosure is not to be limited in terms of the particular examples described in this application, which are intended as illustrations of various aspects. Many modifications and examples can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and apparatuses within the scope of the disclosure, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing descriptions. Such modifications and examples are intended to fall within the scope of the appended claims. The present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is to be understood that this disclosure is not limited to particular methods, reagents, compounds compositions or biological systems, which can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular examples only, and is not intended to be limiting.

[083] With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

[084] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.).

[085] It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation, no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to examples containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, means at least two recitations, or two or more recitations).

[086] Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general, such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general, such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B ."

[087] In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.

[088] As will be understood by one skilled in the art, for any and all purposes, such as in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as "up to," "at least," "greater than," "less than," and the like include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member. Thus, for example, a group having 1-3 items refers to groups having 1, 2, or 3 items. Similarly, a group having 1-5 items refers to groups having 1, 2, 3, 4, or 5 items, and so forth.

[089] While the foregoing detailed description has set forth various examples of the devices and/or processes via the use of block diagrams, flowcharts, and/or examples, such block diagrams, flowcharts, and/or examples contain one or more functions and/or operations, it will be understood by those within the art that each function and/or operation within such block diagrams, flowcharts, or examples can be implemented, individually and/or collectively, by a wide range of hardware, software, firmware, or virtually any combination thereof. In one example, several portions of the subject matter described herein may be implemented via Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), digital signal processors (DSPs), or other integrated formats. However, those skilled in the art will recognize that some aspects of the examples disclosed herein, in whole or in part, can be equivalently implemented in integrated circuits, as one or more computer programs running on one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs running on one or more processors (e.g., as one or more programs running on one or more microprocessors), as firmware, or as virtually any combination thereof, and that designing the circuitry and/or writing the code for the software and/or firmware would be well within the skill of one of skill in the art in light of this disclosure. For example, if a user determines that speed and accuracy are paramount, the user may opt for a mainly hardware and/or firmware vehicle; if flexibility is paramount, the user may opt for a mainly software implementation; or, yet again alternatively, the user may opt for some combination of hardware, software, and/or firmware. In addition, those skilled in the art will appreciate that the mechanisms of the subject matter described herein are capable of being distributed as a program product in a variety of forms, and that an illustrative example of the subject matter described herein applies regardless of the particular type of signal bearing medium used to actually carry out the distribution. Examples of a signal bearing medium include, but are not limited to, the following: a recordable type medium such as a floppy disk, a hard disk drive (HDD), a Compact Disc (CD), a Digital Video Disk (DVD), a digital tape, a computer memory, etc.; and a transmission type medium such as a digital and/or an analog communication medium (e.g., a fiber optic cable, a waveguide, a wired communication link, a wireless communication link, etc.).

[091] Those skilled in the art will recognize that it is common within the art to describe devices and/or processes in the fashion set forth herein, and thereafter use engineering practices to integrate such described devices and/or processes into data processing systems. That is, at least a portion of the devices and/or processes described herein can be integrated into a data processing system via a reasonable amount of experimentation. Those having skill in the art will recognize that a typical data processing system generally includes one or more of a system unit housing, a video display device, a memory such as volatile and non-volatile memory, processors such as microprocessors and digital signal processors, computational entities such as operating systems, drivers, graphical user interfaces, and applications programs, one or more interaction devices, such as a touch pad or screen, and/or control systems including feedback loops and control motors (e.g., feedback for sensing position and/or velocity; control motors for moving and/or adjusting components and/or quantities). A typical data processing system may be implemented utilizing any suitable commercially available components, such as those typically found in data computing/communication and/or network computing/communication systems.

[092] The herein described subject matter sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely examples, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively "associated" such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as "associated with" each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being "operably connected", or "operably coupled", to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being "operably couplable", to each other to achieve the desired functionality. Specific examples of operably couplable include but are not limited to physically mateable and/or physically interacting components and/or wirelessly interactable and/or wirelessly interacting components and/or logically interacting and/or logically interactable components.

[093] While various aspects and examples have been disclosed herein, other aspects and examples will be apparent to those skilled in the art. The various aspects and examples disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.