Aerosol-generating article comprising a first and a second sheet of aerosol-forming substrate

Abstract

There is provided an aerosol-generating article for use with an aerosol-generating device to generate an aerosol. The aerosol-generating article comprising a first sheet of aerosol-forming substrate forming a first sheet protrusion and a second sheet of aerosol-forming substrate forming a second sheet depression. The first sheet and second sheet are stacked such that at least a portion of the first sheet protrusion is accommodated within at least a portion of the second sheet depression. At least a portion of the first sheet protrusion is in contact with at least a portion of a surface of the second sheet depression. There is also provided an aerosol-generating system.

Description

[0001] FTR3875 / PCT (P / 90290.W001)

[0002] 1

[0003] AEROSOL-GENERATING ARTICLE COMPRISING A FIRST AND A SECOND SHEET OF AEROSOLFORMING SUBSTRATE

[0004] The present disclosure relates to an aerosol-generating article comprising an aerosol-forming substrate. In particular, the present disclosure relates to an aerosol-generating article for use with an aerosol-generating device to generate an aerosol.

[0005] A typical aerosol-generating article may appear similar to a conventional cigarette. For example, such an aerosol-generating article may be substantially cylindrical and comprise an aerosol-forming substrate and other components such as a mouthpiece filter element and a cooling element, all arranged together in the form of a rod and wrapped in a cigarette paper. Dimensions of typical aerosol-generating articles are often similar to the dimensions of conventional cigarettes. A typical aerosol-forming article may contain an aerosol-forming substrate that is moulded or extruded as a block or layer or an aerosol-forming substrate that comprises bound collection of strips, strands or particles of material.

[0006] However, a significant portion of the aerosol-forming substrate in these cylindrical aerosol-generating articles may not be sufficiently heated to form an aerosol during use. This is undesirable since the insufficiently heated portion of the aerosol-forming substrate contributes to the cost of manufacture and transport of the aerosol-generating article, but does not contribute to the aerosol delivered to an end user. This may be the case regardless of the way in which the aerosol-forming substrate is heated, for example regardless of whether a resistive or inductive heater is used and regardless of whether the aerosol-forming substrate is heated from the inside or the outside. Moreover, the components of these cylindrical aerosolgenerating articles normally need to have the same or very similar outer diameters so that they can be brought together, accurately positioned in co-axial alignment and wrapped in a cigarette paper. This can lead to increased cost and complexity of manufacture.

[0007] It is an aim of the present disclosure to provide an aerosol-generating article, in which a greater portion of an aerosol-forming substrate of the aerosol-generating article is sufficiently heated to form an aerosol during use. It is also an objective of the present disclosure to provide an aerosol-generating article that can be manufactured relatively efficiently and cheaply, in particular, it is an objective of the present invention to provide an aerosol-forming substrate that is relatively that can be manufactured relatively efficiently and cheaply.

[0008] According to the present disclosure, there may be provided an aerosol-generating article for use with an aerosol-generating device to generate an aerosol. The aerosol-generating article may comprise a first sheet of aerosol-forming substrate forming a first sheet protrusion and a second sheet of aerosol-forming substrate forming a second sheet depression. The first sheet and second sheet may be stacked such that at least a portion of the first sheet protrusion is accommodated within at least a portion of the second sheet depression. At least a portion of the first sheet protrusion is in contact with at least a portion of a surface of the second sheet depression.

[0009] For example, there is provided an aerosol-generating article for use with an aerosol-generating device to generate an aerosol, the aerosol-generating article comprising a first sheet of aerosol-forming substrate forming a first sheet protrusion; and a second sheet of aerosol-forming substrate forming a second sheet depression. The first sheet and second sheet are stacked such that at least a portion of the first sheet protrusion is accommodated within at least a portion of the second sheet depression. At least a portion of the first sheet protrusion is in contact with at least a portion of a surface of the second sheet depression.

[0010] The surface of the at least a portion of the second sheet depression in contact with the first sheet protrusion may be a surface of the second sheet of aerosol-forming substrate. The surface of the at least a portion of the second sheet depression in contact with the first sheet protrusion may be referred to as an inner surface of the second sheet of aerosol-forming substrate. A surface of the first sheet protrusion in contact with the at least a portion of a surface of the second sheet depression may be a surface of the first sheet of aerosol-forming substrate. The surface of the first sheet protrusion in contact with at least a portion of the surface of the second sheet depression may be referred to as an inner surface of the first sheet of aerosol-forming substrate.

[0011] Advantageously, at least a portion of the first sheet protrusion being accommodated within at least a portion of the second sheet depression may allow more than one sheet of aerosol-forming substrate to be provided in an aerosol-generating article. Advantageously, at least a portion of the first sheet protrusion being accommodated within at least a portion of the second sheet depression may prevent or reduce relative movement between the first sheet and the second sheet, for example, movement in a direction orthogonal to the direction of stacking, for example a sliding movement, may be reduced or prevented.

[0012] Advantageously, at least a portion of the first sheet protrusion being accommodated within at least a portion of the second sheet depression and the contact between the first sheet protrusion and a surface of the second sheet depression may allow the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate to be fit together. Advantageously, this may allow the first sheet of aerosolforming substrate and the second sheet of aerosol-forming substrate to be assembled together with little, minimal or no adhesive. Preferably, no adhesive, such as glue, is required to fit the first sheet of aerosolforming substrate and the second sheet of aerosol-forming substrate together. Adhesives may cause an undesirable flavour to be generated when the aerosol-generating article is heated.

[0013] Preferably, a fit, such as an interference fit, or a location fit, is defined between first sheet protrusion and second sheet depression. For example, the contact between and relative shapes of first sheet protrusion and second sheet depression may at least partially secure the first sheet of aerosol-forming substrate to the second sheet of aerosol-forming substrate.

[0014] Preferably, the aerosol-generating article comprises an air inlet, an air outlet and an airflow path defined between the air inlet and the air outlet. At least a portion of the airflow path may be defined between the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate. Advantageously, at least a portion of the airflow path being defined between the first sheet of aerosolforming substrate and the second sheet of aerosol-forming substrate may allow an air flow to contact both the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate, for example simultaneously, this may advantageously improve contact between air flow and the aerosol-forming substrate increasing and improving aerosol formation.

[0015] At least a portion of the airflow path being defined between the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate may allow air to flow across a surface of the first sheet of aerosol-forming substrate and a surface of the second sheet of aerosol-forming substrate. Therefore, improved contact between the airflow and the aerosol-generating substrate may be provided, which may lead to improved aerosol generation. Advantageously, the distance between the first sheet of aerosol- forming substrate and the second sheet of aerosol-forming substrate may be selected to provide a desired cross-section of the airflow path. Therefore, the size of the airflow path and thus the resistance to draw of the aerosol-generating article may be controlled.

[0016] The first sheet of aerosol-forming substrate may be a planar sheet shaped to form the first sheet protrusion. The second sheet of aerosol-forming substrate may be a planar sheet shaped to form the second sheet depression. Advantageously, planar sheets may be simple to manufacture efficiently. Planar sheets of aerosol-forming substrate may be suitable for use in a substantially planar aerosol-generating article.

[0017] The first sheet of aerosol-forming substrate may have a thickness of between 0.02 millimetres to 2 millimetres. For example, the first sheet of aerosol-forming substrate may have a thickness of between 0.05 millimetres to 1 .5 millimetres, for example between 0.1 millimetres and 1 millimetres, for example between 0.2 millimetres and 0.8 millimetres, for example between 0.3 millimetres and 0.6 millimetres, for example between 0.4 millimetres and 0.5 millimetres.

[0018] The second sheet of aerosol-forming substrate may have a thickness of between 0.02 millimetres to 2 millimetres. For example, the second sheet of aerosol-forming substrate may have a thickness of between 0.05 millimetres to 1.5 millimetres, for example between 0.1 millimetres and 1 millimetres, for example between 0.2 millimetres and 0.8 millimetres, for example between 0.3 millimetres and 0.6 millimetres, for example between 0.4 millimetres and 0.5 millimetres.

[0019] Preferably, the aerosol-generating article is defined by an article length extending in the x direction, an article width extending in the y direction, and an article height extending in the z direction. Preferably, the article thickness is less than each of the article width and the article length. Preferably, the article thickness is less than 50 percent article width. Preferably, the article thickness is less than 50 percent article length.

[0020] The first sheet of aerosol-forming substrate may have a length extending in the same direction as the article length, for example in the x direction. The first sheet of aerosol-forming substrate may extend along at least 50 percent of the article length, for example at least 60 percent, at least 70 percent or at least 80 percent of the article length.

[0021] The second sheet of aerosol-forming substrate may have a length extending in the same direction as the article length, for example in the x direction. The second sheet of aerosol-forming substrate may extend along at least 50 percent of the article length, for example at least 60 percent, at least 70 percent or at least 80 percent of the article length.

[0022] The first sheet of aerosol-forming substrate may have a width extending in the same direction as the article width, for example in the y direction. The first sheet of aerosol-forming substrate width may extend along at least 50 percent of the article width, for example at least 60 percent, at least 70 percent or at least 80 percent of the article width.

[0023] The second sheet of aerosol-forming substrate may have a width extending in the same direction as the article width, for example in the y direction. The second sheet of aerosol-forming substrate width may extend along at least 50 percent of the article width, for example at least 60 percent, at least 70 percent or at least 80 percent of the article width.

[0024] Preferably, the first sheet and the second sheet are stacked in the z direction. The first sheet protrusion may have a length, which may be referred to as the first sheet protrusion length. The first sheet protrusion length may extend in substantially the same direction as the article length. The first sheet protrusion length may extend in substantially the same direction as the length of the first sheet of aerosol-forming substrate. The first sheet protrusion may extend the entire length of the first sheet of aerosol-forming substrate. In other words, the length of the first sheet protrusion may be equal to the length of the first sheet of aerosol-forming substrate. Preferably, the first sheet protrusion does not extend along the entire length of the first sheet of aerosol-forming substrate. For example, the first sheet protrusion length may be less than 90 percent, less than 80 percent or less than 70 percent of the length of the first sheet of aerosol-forming substrate. Preferably, the first sheet protrusion length may be less than 50 percent of the length of the first sheet of aerosol-forming substrate, for example less than 40 percent, less than 30 percent or preferably less than 20 percent of the length of the first sheet of aerosol-forming substrate. The second sheet depression may have a length, which may be referred to as the second sheet depression length. The second sheet depression length may extend in substantially the same direction as the article length. The second sheet depression length may extend in substantially the same direction as the length of second sheet of aerosol-forming substrate. The second sheet depression may extend the entire length of the second sheet of aerosol-forming substrate. In other words, the length of the second sheet depression may be equal to the length of the second sheet of aerosol-forming substrate. Preferably, the second sheet depression does not extend along the entire length of the second sheet of aerosol-forming substrate. For example, the second sheet depression length may be less than 90 percent, less than 80 percent or less than 70 percent of the length of the second sheet of aerosol-forming substrate. Preferably, the second sheet depression length may be less than 50 percent of the length of the second sheet of aerosol-forming substrate, for example less than 40 percent, less than 30 percent or preferably less than 20 percent of the length of the second sheet of aerosol-forming substrate.

[0025] Preferably, the first sheet protrusion length may correspond to the second sheet depression length. For example, the first sheet protrusion length may be substantially equal to the second sheet depression length.

[0026] Advantageously, the length of the first sheet protrusion and alternatively or in addition the length of the second sheet depression being less than the length of the first sheet of aerosol-forming substrate and the length of the second sheet of aerosol-forming substrate, respectively, may allow the first sheet of aerosol-forming substrate and alternatively or in addition the second sheet of aerosol-forming substrate to comprise additional features along the length of the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate, respectively. For example, the first sheet of aerosol-forming substrate may comprise multiple first sheet protrusions along a length of the first sheet of aerosol-forming substrate. The second sheet of aerosol-forming substrate may comprise multiple second sheet depressions along a length of the second sheet of aerosol-forming substrate. Advantageously, multiple protrusions and alternatively or in addition multiple depressions may increase the contact between the first sheet of aerosolforming substrate and the second sheet of aerosol-forming substrate, which may reduce the risk of relative movement, such as sliding, between the first sheet and the second sheet. Multiple protrusions and alternatively or in addition multiple depressions along the length of the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate, respectively, may be particularly beneficial for reducing sliding of the sheets of aerosol-forming substrate in a longitudinal direction of the substrate sheet, for example in the x direction when the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate extend in substantially the same direction as the article length.

[0027] According to the present disclosure, there may be provided an aerosol-generating article for use with an aerosol-generating device to generate an aerosol, the aerosol-generating article comprising an aerosolforming substrate for producing an aerosol, the aerosol-generating article being a planar aerosol-generating article having a base defined by a length extending in an x direction, a width extending in a y direction, and a height extending in a z direction.

[0028] Preferably, the article height of the aerosol-generating article is less than both of the article length and article width of the aerosol-generating article. For the purpose of the present disclosure, the “height” of the aerosol-generating article may also be referred to as the “thickness” of the aerosol-generating article.

[0029] According to the present disclosure, there may be provided an aerosol-generating article for use with an aerosol-generating device to generate an aerosol, the aerosol-generating article comprising an aerosolforming substrate for producing an aerosol, the aerosol-generating article comprising a substantially planar upper surface defined by a length extending in an x direction and a width extending in a y direction, and a substantially planar lower surface defined by a length extending in an x direction and a width extending in a y direction. The substantially planar upper surface and the substantially planar lower surface may be vertically spaced from each other by a height defined in a z direction.

[0030] Aerosol-generating articles according to the present disclosure may preferably be substantially flat articles or substantially planar articles. Such articles have a large base area relative to the volume of the article. In particular, the height of the aerosol-generating article may be less than 50 percent of both the length and width of the aerosol-generating article. Advantageously, a larger base area may provide greater surface area for heating by a planar heater of an aerosol-generating device. Advantageously, a smaller height may allow a smaller temperature gradient or difference across the height of the aerosol-generating article during heating. For example, where the base of the aerosol-generating article is in contact with, and heated by, a planar heater, there may be a smaller temperature difference between the base and an upper surface opposing the base if the spacing, or height, between the base and the upper surface is smaller. Advantageously, this may allow heating of a greater proportion of the aerosol-forming substrate of the aerosol-generating article to a temperature at which an aerosol is released, whilst minimising the risk of burning the hottest portion of the substrate closest to the heater. Alternatively, or in addition, this may reduce a time required to heat the aerosol-forming substrate sufficiently to release an aerosol.

[0031] Preferably, the first sheet forms a first sheet depression and the second sheet forms a second sheet protrusion, in which at least a portion of the second sheet protrusion is accommodated in at least a portion of the first sheet depression. Preferably, at least a portion of the second sheet protrusion is in contact with at least a portion of a surface of the first sheet depression. Advantageously, providing this arrangement may further reduce the risk of relative movement, such as sliding, between the first sheet and the second sheet.

[0032] The aerosol-generating article according to any of the aspects disclosed herein may have an air flow path extending through the aerosol-generating article. The aerosol-generating article may have an air-flow path defined through the aerosol-generating article in an x / y plane from one side of the aerosol-generating article to the other side of the aerosol-generating article. The aerosol-generating article may have a resistance to draw (RTD) of up to 50 millimetre H2O. Preferably the aerosol-generating article has a RTD of up to 30 millimetre H2O. The aerosol-generating article may have a resistance to draw (RTD) of between 50 millimetre H2O and 20 millimetres H2O, for example about 30 millimetre H2O. The RTD may be configured to provide a desirable experience for a user.

[0033] The aerosol-generating article preferably has a resistance to draw (RTD) of less than 20 millimetre H2O, for example less than 10 millimetre H2O, in the direction of the airflow path. Preferably, the aerosolgenerating article has a RTD of less than 20 millimetre H2O, for example less than 10 millimetre H2O, in at least one direction in an x / y plane of the aerosol-generating article. An aerosol-generating article with a low resistance air-flow path may allow for superior air-flow management and allow aerosol to be extracted more efficiently from the aerosol-generating article and guided to a user.

[0034] Unless otherwise specified, the resistance to draw (RTD) is measured in accordance with ISO 6565- 2015. The RTD refers to the pressure required to force air through the full length of a component, such as the aerosol-generating article. The terms “pressure drop” or “draw resistance” of a component or article may also refer to the “resistance to draw”. Such terms generally refer to the measurements made in accordance with ISO 6565-2015 and are normally carried out at under test at a volumetric flow rate of about 17.5 millilitres per second at the output or downstream end of the measured component at a temperature of about 22 degrees Celsius, a pressure of about 101 kPa (about 760 Torr) and a relative humidity of about 60%.

[0035] Preferably, the first sheet forms a first plateau and the second sheet forms a second plateau, in which the first plateau and the second plateau are aligned. The first plateau may be formed at a maximum of the first sheet protrusion and the second plateau is formed at a minimum of the second sheet depression. For example, the first sheet protrusion may have a trapezoidal shape. The second sheet depression may have a trapezoidal shape.

[0036] The first sheet protrusion may extend with a first slope and the second sheet depression may extend with a second slope different to the first slope. Advantageously, this may allow the first sheet and second sheet to be stacked, but prevent the second sheet depression from being fully occupied with the first sheet protrusion, so a gap may be formed between the second sheet depression and the first sheet protrusion. Therefore, the gap may allow at least a portion of the airflow path to be defined between the second sheet depression and the first sheet protrusion. Advantageously, adjusting the first slope, the second slope or both the first slope and the second slope may adjust the size of the gap between the second sheet depression and the first sheet protrusion. This may allow the size of the airflow path between the first sheet and second sheet to be adjusted. Therefore, the RTD of the aerosol-generating article may be controlled by adjusting the first slope, the second slope or both the first slope and the second slope.

[0037] The first slope may extend to a plateau of the first sheet protrusion. The second slope may extend to a plateau of the second sheet depression. The plateau of the first sheet protrusion may align with the plateau of the second sheet depression, for example in an x or length direction, and / or in a y or width direction. The plateau of the first sheet protrusion may be spaced from the plateau of the second sheet depression, for example in a z or height direction. The first slope of the first sheet protrusion may align with the second slope of the second sheet depression, for example in an x or length direction, and / or in a y or width direction. The first slope of the first sheet protrusion may be spaced from the second slope of the second sheet depression, for example in a z or height direction. The first sheet and the second sheet may be stacked, for example in a z or height direction. When the first sheet and the second sheet are stacked, the second slope being different to the first slope may result in the plateau of the first sheet protrusion being spaced from the plateau of the second sheet depression, for example in a z or height direction.

[0038] The aerosol-generating article according to any of the aspects disclosed herein may comprise substantially planar upper and lower surfaces. A vertical separation between the substantially planar upper and lower surfaces may define a height (for example, a z dimension) of the aerosol-generating article. An air flow channel may be defined between the substantially planar upper and lower surfaces. The height of the aerosol-generating article may be less than 5 millimetres, for example between 1 .5 millimetres and 5 millimetres, for example between 1 .5 millimetres and 4 millimetres, for example between 1 .5 millimetres and 3 millimetres, for example between 1 .5 millimetres and 2 millimetres. One or both of the substantially planar upper and lower surfaces may comprise an aerosol-forming substrate. The aerosol-generating article may comprise upper and lower layers, the upper layer forming the substantially planar upper surface and the lower layer forming the substantially planar lower surface. At least one of the upper and lower layers may comprise or consist of aerosol-forming substrate.

[0039] Preferably, the first sheet protrusion has a height of between 0.1 millimetres and 6 millimetres, for example between 0.2 millimetres and 5 millimetres, for example between 0.5 millimetres and 5 millimetres, for example between 1 and 5 millimetres, for example between 2 millimetres and 4 millimetres, for example between 2 and 3 millimetres. Preferably, the first sheet protrusion has a height of at least 2.8 millimetres, for example a height of at least 3.0, 3.2 or 3.5 millimetres.

[0040] Preferably, the second sheet depression has a depth of between 0.1 millimetres and 6 millimetres, for example between 0.2 millimetres and 5 millimetres, for example between 0.5 millimetres and 5 millimetres, for example between 1 and 5 millimetres, for example between 2 millimetres and 4 millimetres, for example between 2 and 3 millimetres. Preferably, the second sheet depression has a depth of at least 3 millimetres, for example a height of at least 3.2, 3.5 or 4 millimetres. Advantageously, a depression with a greater depth may allow increased area for the first sheet protrusion to be accommodated within, which may increase the security of the fit between the first sheet and the second sheet. In some embodiments, for example when the first sheet protrusion is only partially received within the second sheet depression, a greater depth of the depression may provide an increased area for air to flow between the first sheet and the second sheet, this may improve aerosol-generation.

[0041] Preferably, the first sheet of aerosol-forming substrate forms multiple first sheet protrusions and the second sheet of aerosol-forming substrate forms multiple second sheet depressions. Preferably, at least a portion of more than one of the multiple first sheet protrusions is accommodated within at least a portion of more than one of the multiple sheet depressions. Preferably, at least a portion of each of the multiple first sheet protrusions is accommodated within at least a portion of a second sheet depression of the multiple second sheet depressions. Preferably, at least a portion of each of the first sheet protrusions is in contact with at least a portion of a surface of a second sheet depression of the multiple second sheet depressions. Preferably, a fit, such as an interference fit, is defined between each first sheet protrusion that is accommodated within at least a portion of a second sheet depression.

[0042] Advantageously, multiple protrusions and multiple depressions may increase the surface area of the first sheet in contact with the second sheet. Advantageously, multiple protrusions and multiple depressions may reduce the risk of relative movement, such as sliding, between the first sheet and the second sheet. The multiple first sheet protrusions and the multiple second sheet depressions may be arranged in a regular pattern.

[0043] The multiple first sheet protrusions may be distributed, for example aligned, in the length direction of the first sheet of aerosol-forming substrate. The multiple second sheet depressions may be distributed, for example aligned, in the length direction of the second sheet of aerosol-forming substrate.

[0044] Alternatively, or in addition, the multiple first sheet protrusions may be distributed, for example aligned, in the width direction of the first sheet of aerosol-forming substrate. The multiple second sheet depressions may be distributed, for example aligned, in the width direction of the second sheet of aerosolforming substrate.

[0045] Preferably, the multiple first sheet protrusions may be aligned in both the length direction and width direction of the first sheet of aerosol-forming substrate. Preferably, the multiple second sheet depressions may be aligned in both the length direction and width direction of the second sheet of aerosol-forming substrate. Advantageously, being aligned in both the length and width direction may reduce the risk of the first sheet of aerosol-forming substrate sliding relative to the second sheet of aerosol-forming substrate in both the length and width directions.

[0046] The aerosol-generating article may comprise a corrugated element. The corrugated element may comprise at least one corrugated sheet. At least one of the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate may be a corrugated sheet. Preferably, the first sheet is a first corrugated sheet of aerosol-forming substrate forming first corrugations and the second sheet is a second corrugated sheet of aerosol-forming substrate forming second corrugations, in which the first corrugations form the multiple first sheet protrusions and first sheet depressions and the second corrugations form multiple second sheet depressions and second sheet protrusions. Advantageously, corrugated sheets may be relatively efficient and simple to manufacture and may be produced using high speed production methods similar to those used for production of corrugated cardboard.

[0047] The first and second corrugated sheets may be defined by a corrugation profile, in which the corrugation profile is sinusoidal, or triangular, or rectangular, or trapezoidal, or toroidal, or parabolic.

[0048] Preferably, the first and second corrugations extend along a longitudinal axis of the aerosolgenerating article. At least a portion of the airflow path may be defined by at least one of the first corrugated sheet of aerosol-forming substrate and the second corrugated sheet of aerosol-forming substrate. Preferably, at least a portion of the airflow path may be defined by both the first corrugated sheet of aerosolforming substrate and the second corrugated sheet of aerosol-forming substrate. Preferably, at least a portion of the airflow path may extend along the first and second corrugations. For example, at least a portion of the airflow path may be aligned substantially parallel to and between the first and second corrugations. Therefore, at least a portion of the airflow path may extend along a longitudinal axis of the article. This may provide a low RTD airflow path through the article.

[0049] The height of the protrusions of the corrugated sheet may be an amplitude, such as a peak amplitude, of the corrugated sheet. The depth of the depressions of the corrugated sheet may be an amplitude, such as a peak amplitude, of the corrugated sheet. The peak-to-peak amplitude of the corrugated sheet may be a height of the protrusion of the corrugated sheet plus a height of the depression of the corrugated sheet.

[0050] The peak-to-peak amplitude of the first sheet may also be known as the height of the first sheet, which may be between 0.2 and 12 millimetres, for example between 0.5 and 10 millimetres. Preferably, the height of the first sheet may be at least 1 millimetre, for example at least 2, 3, 4 or 5 millimetres. Preferably, the height of the first sheet is least 6 millimetres. The peak-to-peak amplitude of the second sheet may also be known as the height of the second sheet, which may be between 0.2 and 12 millimetres, for example between 0.5 and 10 millimetres. Preferably, the height of the second sheet may be at least 1 millimetre, for example at least 2, 3, 4 or 5 millimetres. Preferably, the height of the second sheet is least 6 millimetres.

[0051] The height of the first sheet may be the same as the height of the second sheet. As the height of the first sheet and second sheet is increased, the security of the fit between the two sheets may also increase. In other words, as the height increases the risk of accidental relative movement between the first sheet and the second sheet may be reduced.

[0052] The aerosol-generating article may comprise a first planar layer and a second planar layer. The first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate may be positioned between the first planar layer and the second planar layer. The first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate may together be referred to as an intermediate layer.

[0053] Optionally, the aerosol-generating article comprises more than two sheets of aerosol-forming substrate. For example, the aerosol-generating article may comprise a third sheet of aerosol-forming substrate. The aerosol-generating article may further comprise a fourth sheet of aerosol-forming substrate. The aerosol-generating article may further comprise a fifth sheet of aerosol-forming substrate. Any sheet of the multiple sheets of aerosol-forming substrate may be the same as the first sheet of aerosol-forming substrate. Any sheet of the multiple sheets of aerosol-forming substrate may be the same as the second sheet of aerosol-forming substrate. Preferably, each sheet of aerosol-forming substrate is stacked with another sheet of the sheets of aerosol-forming substrate.

[0054] According to the present disclosure, there may be provided an aerosol-generating article for use with an aerosol-generating device to generate an aerosol, the aerosol-generating article comprising a first planar layer, a second planar layer, and a corrugated layer arranged between the first planar layer and the second planar layer. At least one of the first planar layer, the second planar layer and the corrugated layer may comprise or consist of an aerosol-forming substrate.

[0055] The use of a corrugated structure in the aerosol-generating article may advantageously allow the production of an aerosol-generating article that has extremely low RTD while still being sufficiently rigid to for a user to handle. Further, use of a corrugated structure may allow a low density, low RTD, aerosolgenerating article to be produced using high speed production methods similar to those used for production of corrugated cardboard.

[0056] The corrugated layer may comprise or consist of the first sheet of aerosol-forming substrate. The corrugated layer may comprise or consist of the second sheet of aerosol-forming substrate.

[0057] Preferably, the corrugated layer is a first corrugated layer, and the aerosol-generating article may further comprise a second corrugated layer. Preferably, the first corrugated layer comprises or consists of the first sheet of aerosol-forming substrate. Preferably, the second corrugated layer comprises or consists of the second sheet of aerosol-forming substrate.

[0058] The aerosol-generating article may comprise a cavity, in which the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate are positioned in the cavity and the at least a portion the airflow path extends through the cavity. The aerosol-generating article may comprise a first planar external surface and a second planar external surface. The aerosol-generating article may comprise a frame positioned between the first planar external surface and the second planar external surface. Preferably, the frame at least partially defines the cavity.

[0059] According to the present disclosure, there may be provided an aerosol-generating article for use with an aerosol-generating device to generate an aerosol. The aerosol-generating article may comprise a first planar external surface, a second planar external surface, a cavity and a frame. The frame is positioned between the first planar external surface and the second planar external surface. The frame at least partially defines the cavity. The aerosol-generating article comprises an aerosol-forming substrate. The aerosolgenerating article may comprise an air inlet and an air outlet, and an airflow passage extending between the air inlet and the air outlet through the cavity.

[0060] Preferably, the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate are positioned between the first planar external surface and the second planar external surface.

[0061] The frame may comprise a peripheral wall at least partially circumscribing or encircling the cavity. The frame may comprise a peripheral wall wholly circumscribing or encircling the cavity. Advantageously, the frame may allow the aerosol-generating article to be relatively thin whilst maintaining structural rigidity.

[0062] The aerosol-generating article may comprise a first planar external layer and a second planar external layer, in which the first planar external layer forms the first planar external surface and the second planar external layer forms the second planar external surface. Optionally, at least one of the first planar external layer, the second planar external layer, and the frame may comprise or consist of aerosol-forming substrate.

[0063] The cavity may be substantially empty.

[0064] The cavity may have a cavity length of at least 15 or 20 millimetres. The cavity may have a cavity length of no more than 40 or 30 millimetres. The cavity may have a cavity width of no more than 13 or 10 millimetres. The cavity may have a cavity height of no more than 5 or 4 millimetres. The cavity may have a cavity length of between 15 and 40, preferably between 20 and 30, millimetres. The cavity may have a cavity width of between 5 and 13, preferably between 7 and 10, millimetres. The cavity may have a cavity height of between 1 .5 and 5, preferably between 2.5 and 4, millimetres. Preferably, the cavity has a cavity length of between 15 and 40 millimetres, a cavity width of between 5 and 13 millimetres, and a cavity height of between 1 .5 and 5 millimetres. More preferably, the cavity has a cavity length of between 20 and 30 millimetres, a cavity width of between 7 and 10 millimetres, and a cavity height of between 2.5 and 4 millimetres.

[0065] Preferably, the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate may be positioned within the cavity.

[0066] A corrugated layer may be positioned within the cavity.

[0067] The frame may be a planar frame.

[0068] The frame may have a height between 50 percent and 95 percent of the height of the aerosolgenerating article. The frame may have a height between 60 percent and 95 percent of the height of the aerosol-generating article. The frame may have a height between 70 percent and 95 percent of the height of the aerosol-generating article. The frame may have a height between 80 percent and 95 percent of the height of the aerosol-generating article. The frame may have a height between 1 millimetre and 5.5 millimetres. The frame may have a height between 1 millimetre and 5 millimetres. Preferably, the frame may have a height between 1 .5 millimetres and 5 millimetres.

[0069] The frame may be made from or comprise a biodegradable material. The frame may be made entirely from a biodegradable material.

[0070] The frame may be made from or comprise a cellulosic material. The cellulosic material may comprise a sheet of cellulosic material. The cellulosic material may comprise cellulose fibres. The cellulosic material may be paper, paperboard, or cardboard. The frame may be made from or comprise a plant material, such as tobacco. The frame may be made entirely from a cellulosic material.

[0071] The frame may be a unitary component. Alternatively, the frame may comprise two or more layers. That is, the frame may have a laminated structure.

[0072] Preferably, at least one of the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate is an embossed sheet.

[0073] As used herein, the term "embossed" denotes a raised pattern on a surface. In "embossing", a design is formed, for example carved, moulded, stamped or others, on a surface of a sheet so that it stands out in relief. The embossed pattern may include a plurality of projections (also called bumps or protuberances ) on at least one of the sheet's surfaces. For example, the embossing process may form a plurality of peaks and valleys on the surface. Alternatively, a plurality of raised structures on an otherwise flat surface can be obtained.

[0074] The embossed sheet may be a crimped sheet. For example, a sheet of aerosol-forming substrate may be crimped to form the embossed sheet. The sheet of aerosol-forming substrate may be crimped to form projections. For example, the sheet may have a wavy profile, when observed in a direction parallel to its surface.

[0075] Advantageously, at least one of the first sheet and the second sheet being embossed may allow a gap between the first sheet and second sheet to be formed. At least one of the first sheet and the second sheet being embossed may prevent or reduce the surface area of the first sheet in contact with the second sheet, and therefore reduce risk of the first and the second sheet sticking together.

[0076] The embossed sheet may comprise a projection from a surface of the embossed sheet. Preferably, the embossed sheet comprises a plurality of projections from a surface of the embossed sheet. The projection is, or projections are, in contact with the other sheet of the first or second sheets to separate the surface from the other sheet of the first or second sheets. The projection or projections may extend orthogonal to a surface of the sheet of aerosol-forming substrate. For example, the projection or projections of the embossed sheet, in which first sheet of aerosol-forming substrate is the embossed sheet, may extend orthogonal to the inner surface of the first sheet of aerosol-forming substrate. The projection or projections of the embossed sheet, in which second sheet of aerosol-forming substrate is the embossed sheet, may extend orthogonal to the inner surface of the second sheet of aerosol-forming substrate.

[0077] Preferably, the projection or projections have a height of between about 10 and about 150 percent of the thickness of the embossed sheet, more preferably between about 25 and about 75 percent of the thickness of the embossed sheet.

[0078] Preferably, the projection or projections have a height of less than 3 millimetres, preferably less than 2 millimetres. Preferably, the projection or projections have a height of between 0.01 and 1 millimetres. Preferably, the projection or projections have a height of between 0.05 and 0.5 millimetres, for example between 0.1 and 0.4 millimetres.

[0079] Advantageously, the height of the projection or projections provides a distance between a surface of the first sheet and second sheet sufficient to allow an airflow having a desirable RTD.

[0080] The embossed sheet may have a thickness. The thickness of the embossed sheet may be the same as the thicknesses described as suitable for the first or second sheet. Preferably, the thickness of the embossed sheet is between about 0.1 millimetres and 2 millimetres.

[0081] Preferably, the thickness of the embossed sheet has a is between about 0.1 millimetres and 0.5 millimetres. Preferably, the thickness of the embossed sheet is between 0.2 and 0.5 millimetres. Advantageously, this relatively thin thickness of the embossed sheet may ensure there is adequate space for air to flow within the aerosol-generating article.

[0082] The thickness of the embossed sheet may be greater than 1 millimetre, for example greater than 1 .2 or 1 .5 millimetres. The thickness of the embossed sheet may be between 1 .2 and 3 millimetres, for example between 1 .2 and 2 millimetres. Advantageously, a relatively thick thickness of the embossed sheet may increase the amount of aerosol-forming substrate in the embossed sheet.

[0083] The projections may be provided with a regular pattern, evenly distributed across a surface of the embossed sheet. Advantageously, a regular pattern may enable to the embossed sheet to provide a regular and consistent gap between the first sheet and second sheet.

[0084] Preferably, both the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate are embossed sheets.

[0085] The aerosol-generating article of any of the aspects of the present disclosure may have a length (for example, an x dimension) of between 10 millimetres and 100 millimetres, or between 10 millimetres and 50 millimetres, for example between 10 millimetres and 40 millimetres, for example between 12 millimetres and 30 millimetres, for example between 14 millimetres and 26 millimetres, for example between 16 millimetres and 24 millimetres, for example between 18 millimetres and 22 millimetres, for example about 18 millimetres, or about 19 millimetres, or about 20 millimetres, or about 21 millimetres, or about 22 millimetres.

[0086] The aerosol-generating article may have a width (for example, a y dimension) of between 5 millimetres and 20 millimetres, for example between 8 millimetres and 18 millimetres, for example between 10 millimetres and 16 millimetres, for example between 11 millimetres and 15 millimetres, for example between 12 millimetres and 14 millimetres, for example about 13 millimetres.

[0087] The aerosol-generating article may have a height (for example, a z dimension) of between 1 millimetres and 10 millimetres, for example between 1 .2 millimetres and 8 millimetres, for example between 1 .4 millimetres and 7 millimetres, for example between 1 .6 millimetres and 6 millimetres, for example between 1.7 millimetres and 5 millimetres, for example about 1.7 millimetres, or about 4.5 millimetres, or about 2 millimetres, or about 3 millimetres, or about 4 millimetres.

[0088] The aerosol-generating article of any of the aspects of the present disclosure when viewed in plan may have a shape defining a polygon, a quadrilateral (for example, a rectangle or a square), an oval, a circle, or a combination thereof. Where the aerosol-generating article comprises substantially planar upper and lower surfaces, one or both of the upper and lower surfaces when viewed in plan may have a shape defining a polygon, a quadrilateral (for example, a rectangle or a square), an oval, a circle, or a combination thereof. A perimeter of the aerosol-generating article when viewed in plan may be formed of a plurality of straight sides, a plurality of curved sides, or a combination of straight and curved sides. Where the aerosolgenerating article comprises substantially planar upper and lower surfaces, a perimeter of one or both of the upper and lower surfaces when viewed in plan may have a shape defining a polygon, a quadrilateral (for example, a rectangle or a square), an oval, a circle, or a combination thereof.

[0089] The aerosol-generating article may consist entirely of aerosol-forming substrate. For example, the aerosol-generating article may consist entirely of the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate.

[0090] Alternatively, the aerosol-forming substrate may be one of a plurality of component parts of the aerosol-generating article. For example, the aerosol-generating article may comprise the first sheet of aerosol-forming substrate, the second sheet of aerosol-forming substrate and one or more other components.

[0091] Preferably, the aerosol-forming substrate comprises an aerosol-forming material.

[0092] The aerosol-forming substrate may comprise nicotine. Nicotine may be present in the form of a tobacco material or may be in the form of a nicotine extract.

[0093] The aerosol-forming substrate may comprise one or more organic materials such as tobacco, mint, tea and cloves. The aerosol-forming substrate may comprise one or more of: herb leaf, tobacco leaf, fragments of tobacco ribs, reconstituted tobacco, homogenised tobacco such as cast leaf, extruded tobacco, expanded tobacco, aerosol-generating films and gel compositions.

[0094] The aerosol-forming substrate may comprise or consist of homogenised tobacco material, for example a reconstituted tobacco material or a cast leaf tobacco material.

[0095] The aerosol-forming substrate may be in the form of shredded aerosol-generating material. The shredded aerosol-generating material may comprise one or more of: strips and strands of aerosolgenerating material, such as strips and strands of tobacco or homogenised tobacco material. The shredded aerosol-generating material may be in the form of a shredded sheet of homogenised tobacco material.

[0096] The aerosol-forming substrate may be cut filler. The aerosol-forming substrate may be tobacco cut filler. The cut filler may comprise one or more of bright tobacco, dark tobacco, aromatic tobacco and filler tobacco. Examples of bright tobaccos are Flue-Cured Brazil, Indian Flue-Cured, Chinese Flue-Cured, US Flue-Cured such as Virginia tobacco, and Flue-Cured from Tanzania. Examples of aromatic tobaccos are Oriental Turkey, Greek Oriental, semi-oriental tobacco but also Fire Cured, US Burley, such as Perique, and Rustica. Examples of dark tobacco are Dark Cured Brazil Galpao, Burley Malawi or other African Burley, Sun Cured or Air Cured Indonesian Kasturi. As used herein, the term “cut filler” is used to describe a blend of shredded plant material, such as tobacco plant material, including, in particular, one or more of leaf lamina, processed stems and ribs, homogenised plant material.

[0097] The aerosol-forming substrate may comprise a bound collection of strips, strands or particles of tobacco material. The aerosol-forming substrate may be in the form of a compressed plug of tobacco material; for example, in which a plug having a substantially circular cross-section in an initial state of the plug is compressed into a flatter cross-sectional profile in a subsequent state of the plug. The tobacco material may be enclosed by a wrapper. The aerosol-forming substrate may be in the form of strips, strands or particles of tobacco material bound together in a binder matrix. As used herein, the term “sheet” describes a laminar element having a width and length substantially greater than the thickness thereof. The width of a sheet may be greater than 10 mm, preferably greater than 20 mm or 30 mm. In certain embodiments, sheets of material for use in forming aerosol-forming substrates as described herein may have a thickness of between 10 pm and about 1000 pm, for example between 10 pm and about 300 pm. The first sheet of aerosol-generating substrate may be a sheet of plant material. The second sheet of aerosol-generating substrate may be a sheet of plant material. The first sheet of aerosol-generating substrate may be a sheet of tobacco material. The second sheet of aerosolgenerating substrate may be a sheet of tobacco material. The first sheet of aerosol-generating substrate may be a sheet of homogenised tobacco material, such as a cast leaf sheet. The second sheet of aerosolgenerating substrate may be a sheet of homogenised tobacco material, such as a cast leaf sheet.

[0098] Preferably, the first sheet of aerosol-forming substrate comprises a first aerosol-forming material and the second sheet of aerosol-forming substrate comprises a second aerosol-forming material. Preferably, the first aerosol-forming material is different to the second aerosol-forming material.

[0099] Preferably, at least one of the first aerosol-forming material and the second aerosol-forming material is a homogenised tobacco material.

[0100] Preferably, at least one of the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate comprises a cellulose fibre, such as hydroxypropyl methylcellulose.

[0101] The aerosol-forming substrate may comprise one or more aerosol-formers. Suitable aerosol-formers are well known in the art and include, but are not limited to, one or more aerosol-formers selected from: polyhydric alcohols, such as propylene glycol, polyethylene glycol, triethylene glycol, 1 , 3-butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. It may be particularly preferable for the aerosol-former to be or comprise one or both of glycerine and propylene glycol. The aerosol former may consist of glycerine or propylene glycol or of a combination of glycerine and propylene glycol.

[0102] The aerosol-forming substrate may have an aerosol-former content greater than or equal to 1 , 2, 5, 10, or 15 percent by weight on a dry weight basis. The aerosol-forming substrate may have an aerosolformer content greater than or equal to 15 percent by weight on a dry weight basis, for example greater than 20 by weight on a dry weight basis, or greater than 25 by weight on a dry weight basis, or greater than 30 by weight on a dry weight basis, or greater than 40 by weight on a dry weight basis, or greater than 50 by weight on a dry weight basis.

[0103] The aerosol-forming substrate may have an aerosol-former content less than or equal to 30 percent by weight on a dry weight basis, less than or equal to 25 percent by weight on a dry weight basis, or less than or equal to 20 percent by weight on a dry weight basis. That is, the aerosol-generating material may have an aerosol-former content less than or equal to 30 by weight on a dry weight basis, less than or equal to 25 by weight on a dry weight basis, or less than or equal to 20 by weight on a dry weight basis.

[0104] The aerosol-forming substrate may have an aerosol-former content between 1 percent and 30 percent by weight on a dry weight basis, between 1 percent and 25 percent by weight on a dry weight basis, or between 1 percent and 20 percent by weight on a dry weight basis.

[0105] The aerosol-forming substrate may comprise at least 50 percent by weight of aerosol former, at least 60 percent by weight of aerosol former, or at least 70 percent by weight of aerosol former. The aerosol-forming substrate may comprise less than or equal to 85 percent by weight of aerosol former, less than or equal to 80 percent by weight of aerosol former, or less than or equal to 75 percent by weight of aerosol former.

[0106] The aerosol-forming substrate may comprise between 50 percent and 85 percent by weight of aerosol former, between 50 percent and 80 percent by weight of aerosol former, or between 50 percent and 75 percent by weight of aerosol former.

[0107] The aerosol-forming substrate may comprise nicotine. The aerosol-forming substrate may comprise natural nicotine, or synthetic nicotine, or a combination of natural nicotine and synthetic nicotine.

[0108] The aerosol-forming substrate may comprise at least 0.5 percent by weight of nicotine, at least 1 percent by weight of nicotine, at least 1 .5 percent by weight of nicotine, or at least 2 percent by weight of nicotine.

[0109] The aerosol-forming substrate may comprise one or more flavourants. The one or more flavourants may comprise one or more of: one or more essential oils such as eugenol, peppermint oil and spearmint oil; one or both of menthol and eugenol; one or both of anethole and linalool; and a herbaceous material. Suitable herbaceous material includes herb leaf or other herbaceous material from herbaceous plants including, but not limited to, mints, such as peppermint and spearmint, lemon balm, basil, cinnamon, lemon basil, chive, coriander, lavender, sage, tea, thyme, and caraway. The one or more flavourants may comprise a tobacco material.

[0110] The aerosol-forming substrate may comprise one or more botanicals. For example, the aerosolforming substrate may comprise about 1 to 90 %, for example about 15 to 55 %, preferably of about 20 to 35 %, of botanicals such as Clove, Echinacea sp., Fennel, Ginger, Hawthorn berry, Elderberry, Monarda, Mullein leaves, Nettle, Plantain, Turmeric, Yarrow, Rooibos, Star Anise, Thyme, Anethum, Chamomile and compounds of those.

[0111] The aerosol-forming substrate may have a moisture content of about 5 to 25%, preferably of about 7 to 15%, at final product state. For example, the aerosol-forming substrate may be a homogenised tobacco material with a moisture of about 5 to 25%, preferably of about 7 to 15%, at final product state.

[0112] The aerosol-forming substrate may comprise a binder. For example, the aerosol-forming substrate may comprise about 1 to 10%, preferably of about 1 to 5%, of a binder such as any of common gums or pectins used in food and beverage (F&B) industries. Preferred binders may be natural pectins, such as fruit, for example citrus, ortobacco pectins; guar gums, land locust bean gums, such as hydroxyethyl and / or hydroxypropyl of those; starches, such as modified or derivatized starches; alginate; methyl, ethyl, ethyl hydroxymethyl and carboxymethyl, celluloses; dextran; and xanthan gum. A preferable binder is guar.

[0113] The aerosol-forming substrate may comprise, or consist of, a solid aerosol-forming material. The aerosol-forming substrate may comprise a liquid aerosol-forming material, for example a liquid aerosolforming material retained within a porous matrix. The aerosol-forming substrate may comprise a gel aerosol-forming material.

[0114] The aerosol-forming substrate may have a true or absolute density of at least 0.25, 0.35 or 0.5 grams per centimetre cubed. The aerosol-forming substrate may have a true or absolute density of no more than 1.8, 1.3 or 1.1 grams per centimetre cubed. The aerosol-forming substrate may have a true or absolute density of between 0.25 and 1.8, preferably between 0.35 and 1.3, more preferably between 0.5 and 1.1 grams per centimetre cubed. A total mass of aerosol-forming substrate of the aerosol-generating article may be at least 50, 80, or 110 milligrams. A total mass of aerosol-forming substrate of the aerosol-generating article may be no more than 700, 500, 400, 300, 250, 200, or 150 milligrams. A total mass of aerosol-forming substrate of the aerosol-generating article may be between 50 and 700, or between 80 and 500, or between 110 and 400, or between 110 and 300, milligrams.

[0115] Preferably, the article is a low-mass substrate article. That is, preferably, a total mass of aerosolforming substrate of the aerosol-generating article is no more than 250 milligrams. It may be even more preferable for a total mass of aerosol-forming substrate of the aerosol-generating article to be no more than 200 milligrams. It may be most preferable for a total mass of aerosol-forming substrate of the aerosolgenerating article to be no more than 200 milligrams. Advantageously, the article may allow extraction of more aerosol from a smaller mass of substrate, for example due to a configuration with the first sheet and second sheet with the protrusion and depression, and this may allow an article with a mass of substrate no more than 250 or 200 or even 150 milligrams to still provide a satisfactory experience. This low mass may also advantageously reduce transport costs. This low mass may also mean that the article has a low RTD.

[0116] Thus, preferably, a total mass of aerosol-forming substrate of the aerosol-generating article is between 110 and 250 milligrams. More preferably, a total mass of aerosol-forming substrate of the aerosolgenerating article is between 110 and 200 milligrams. Most preferably, a total mass of aerosol-forming substrate of the aerosol-generating article is between 110 and 150 milligrams.

[0117] The first and second sheets of aerosol-forming substrate may make up the total mass of aerosolforming substrate of the aerosol-generating article. The total mass of aerosol-forming substrate of the aerosol-generating article may be contained within the cavity mentioned above.

[0118] The total mass of aerosol-forming substrate of the aerosol-generating article may be contained within the cavity, and the total mass of aerosol-forming substrate of the aerosol-generating article divided by the volume of the cavity may be one or both of: at least 0.1 or 0.2 milligrams per millimetre cubed; and no more than 0.4 or 0.3 milligrams per millimetre cubed. Thus, the total mass of aerosol-forming substrate of the aerosol-generating article divided by the volume of the cavity may be between 0.1 and 0.4, preferably between 0.2 and 0.4 or between 0.1 and 0.3, most preferably between 0.2 and 0.3, milligrams per millimetre cubed. Advantageously, such relatively low ranges may be particularly beneficial with low masses of substrate, for example where the total mass of substrate is no more than 250 or 200 milligrams. These values may mean that the cavity is mostly empty, and this may advantageously give the article a low RTD.

[0119] Alternatively, the total mass of aerosol-forming substrate of the aerosol-generating article may be contained within the cavity, and the total mass of aerosol-forming substrate of the aerosol-generating article divided by the volume of the cavity may be one or both of: at least 0.3 or 0.4 milligrams per millimetre cubed; and no more than 0.7 or 0.6 milligrams per millimetre cubed. Thus, the total mass of aerosol-forming substrate of the aerosol-generating article divided by the volume of the cavity may be between 0.3 and 0.7, preferably between 0.4 and 0.7 or between 0.3 and 0.6, most preferably between 0.4 and 0.6, milligrams per millimetre cubed. Such relatively high ranges may be particularly beneficial with higher masses of substrate. These values may mean that the cavity is relatively densely packed with substrate, meaning that there is less empty space and the articles more space-efficient. This can advantageously allow the articles to be made smaller, for example. The cavity may have a total volume made up of a volume occupied by aerosol-forming substrate and a volume not occupied by aerosol-forming substrate. The volume not occupied by aerosol-forming substrate may be empty or occupied by air. The volume occupied by aerosol-forming substrate divided by the total volume of the cavity may be one or both of: at least 0.05 or 0.1 ; and no more than 0.5 or 0.4. Thus, the volume occupied by aerosol-forming substrate divided by the total volume of the cavity may be between 0.05 and 0.5, preferably between 0.1 and 0.4. Advantageously, this may mean that the cavity is mostly empty, and this may advantageously give the article a low RTD.

[0120] According to the present disclosure, an aerosol-generating device for receiving an aerosolgenerating article as disclosed herein, or an aerosol-forming substrate as disclosed herein, may comprise a cavity dimensioned to receive at least a portion of the aerosol-generating article or aerosol-forming substrate, a heater or heating means, a power source for supplying power to the heater or heating means, and a controller to control supply of power to the heater or heating means. The aerosol-generating device is configured to heat an aerosol-forming substrate, for example an aerosol-forming substrate that is a component part of an aerosol-generating article, to form an aerosol, for example an inhalable aerosol.

[0121] The aerosol-generating device may preferably be configured to receive the entirety of the aerosolgenerating article such that the aerosol-generating article is wholly enclosed within the aerosol-generating device.

[0122] The cavity may comprise an opening into which a distal end of the aerosol-generating article can be inserted. The cavity may have any suitable cross-sectional shape. For example, the cavity may have a rectangular transverse cross-section, for example a rectangular cross-section having opposing top and bottom sides that are greater in length than left and right sides.

[0123] Preferably, at least one internal surface of the cavity is a heating surface configured to heat an aerosol-generating article. The heating surface may comprise a heater, for example a resistance heater, or an infra-red heater, or a susceptor configured to be heated by engagement with an inductor. The heating surface may comprise an inductor, for example the surface may comprise a coil arranged to generate a fluctuating electromagnetic field within a space of the cavity. The heating surface may be a surface that is permeable to a fluctuating electromagnetic field, such that an inductor arranged outside the cavity can project a fluctuating electromagnetic field through the heating surface to engage with a susceptor arranged within the cavity.

[0124] According to the present disclosure, there may be provided an aerosol-generating system. The aerosol-generating system may comprise an aerosol-generating article and an aerosol-generating device for use with the aerosol-generating article to generate an inhalable aerosol. The aerosol-generating article may be any aerosol-generating article as described herein.

[0125] Preferably, the aerosol-generating device comprises a heater arranged to heat at least part of the aerosol-generating article. The aerosol-generating device may be any aerosol-generating device as described herein.

[0126] Preferably, the heater is configured to heat the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate, to generate an inhalable aerosol.

[0127] As used herein, the term “aerosol-generating article” may refer to an article able to generate, or release, an aerosol. As used herein, the term “aerosol-forming substrate” may refer to a substrate capable of releasing an aerosol or volatile compounds that can form an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate. An aerosol-forming substrate may comprise an aerosol-forming material. An aerosol-forming substrate may be adsorbed, coated, impregnated, or otherwise loaded onto a carrier or support. An aerosol-forming substrate may conveniently be part of an aerosol-generating article or smoking article.

[0128] As used herein, the term “aerosol-generating device” may refer to a device for use with an aerosolgenerating article to enable the generation, or release, of an aerosol.

[0129] As used herein, the term “aerosol generating system” refers to a combination of an aerosolgenerating device and one or more aerosol-forming articles for use with the device. An aerosol-generating system may include additional components, such as a charging unit for recharging an on-board electric power supply in an electrically operated or electric aerosol-generating device.

[0130] As used herein, the term “aerosol former” may refer to any suitable known compound or mixture of compounds that, in use, facilitates formation of an aerosol. The aerosol may be a dense and stable aerosol. The aerosol may be substantially resistant to thermal degradation at the operating temperature of the aerosol-forming substrate or aerosol-generating article.

[0131] As used herein with reference to the invention, the term “nicotine”, is used to describe nicotine, nicotine base or a nicotine salt.

[0132] As used herein with reference to the invention, the terms “proximal”, “distal”, “upstream” and “downstream” are used to describe the relative positions of components, or portions of components, of the aerosol-generating article.

[0133] As used herein, the term “longitudinal” refers to the direction corresponding to the main longitudinal axis of the aerosol-generating article, which extends between the upstream and downstream ends of the aerosol-generating article. During use, air may be drawn through the aerosol-generating article in the longitudinal direction.

[0134] As used herein, the term “homogenised tobacco material” encompasses any tobacco material formed by the agglomeration of particles of tobacco material. Sheets or webs of homogenised tobacco material are formed by agglomerating particulate tobacco obtained by grinding or otherwise powdering of one or both of tobacco leaf lamina and tobacco leaf stems. In addition, homogenised tobacco material may comprise a minor quantity of one or more of tobacco dust, tobacco fines, and other particulate tobacco byproducts formed during the treating, handling and shipping of tobacco. The sheets of homogenised tobacco material may be produced by casting, extrusion, paper making processes or other any other suitable processes known in the art.

[0135] The term “cast leaf’ is used herein to refer to a product made by a casting process that is based on casting a slurry comprising plant particles (for example, clove particles or tobacco particles and clove particles in a mixture) and a binder (for example, guar gum) onto a supportive surface, such as a belt conveyor, drying the slurry and removing the dried sheet from the supportive surface. An example of the casting or cast leaf process is described in, for example, US-A-5,724,998 for making cast leaf tobacco. In a cast leaf process, particulate plant materials are produced by pulverizing, grinding, or comminuting parts of the plant. The particles produced from one or more plants are mixed with a liquid component, typically water, to form a slurry. Other components in the slurry may include fibres, a binder and an aerosol former. The particulate plant materials may be agglomerated in the presence of the binder. The slurry is cast onto a supportive surface and dried into a sheet of homogenized plant material. Preferably, homogenized plant material used in articles according to the present invention may be produced by casting. Such homogenized plant material may comprise agglomerated particulate plant material.

[0136] As used herein, resistance to draw is expressed with the units of pressure “mm H2O” or “mm WG” or “mm of water gauge” and may be measured in accordance with ISO 6565:2002.

[0137] The invention is defined in the claims. However, below there is provided a non-exhaustive list of nonlimiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

[0138] Ex1 . An aerosol-generating article for use with an aerosol-generating device to generate an aerosol, the aerosol-generating article comprising: a first sheet of aerosol-forming substrate forming a first sheet protrusion; and a second sheet of aerosol-forming substrate forming a second sheet depression, in which the first sheet and second sheet are stacked such that at least a portion of the first sheet protrusion is accommodated within at least a portion of the second sheet depression, and a fit is defined between first sheet protrusion and second sheet depression.

[0139] Ex2. The aerosol-generating article according to example Ex1 , comprising an air inlet, an air outlet and an airflow path defined between the air inlet and the air outlet, in which at least a portion of the airflow path is defined between the first sheet and the second sheet.

[0140] Ex3. The aerosol-generating article according to example Ex1 or Ex2, wherein the first sheet of aerosolforming substrate is a planar sheet shaped to form the first sheet protrusion, and the second sheet of aerosol-forming substrate is a planar sheet shaped to form the second sheet depression.

[0141] Ex4. The aerosol-generating article according to any preceding example, wherein the aerosolgenerating article is defined by an article length extending in an x-direction, an article width extending in a y-direction, and an article thickness extending in a z-direction, wherein the article thickness is less than each of the article width and the article length.

[0142] Ex5. The aerosol-generating article according to example Ex4, in which the first sheet and the second sheet are stacked in the z-direction.

[0143] Ex6. The aerosol-generating article according to any preceding example, wherein the first sheet forms a first sheet depression, and the second sheet forms a second sheet protrusion, in which at least a portion of the second sheet protrusion is accommodated in at least a portion of the first sheet depression.

[0144] Ex7. The aerosol-generating article according to any preceding example, wherein the first sheet forms a first plateau and the second sheet forms a second plateau, in which the first plateau and the second plateau are aligned.

[0145] Ex8. The aerosol-generating article according to example Ex7, wherein the first plateau is formed at a maximum of the first sheet protrusion and the second plateau is formed at a minimum of the second sheet depression.

[0146] Ex9. The aerosol-generating article according to any preceding example, wherein the first sheet protrusion extends with a first slope and the second sheet depression extends with a second slope different to the second slope. Ex9a. The aerosol-generating article according to example Ex9, wherein the first slope extends to a plateau of the first sheet protrusion, and wherein the second slope extends to a plateau of the second sheet depression.

[0147] Ex9b. The aerosol-generating article according to example Ex9a, wherein the plateau of the first sheet protrusion aligns with the plateau of the second sheet depression, for example in an x or length direction and / or in a y or width direction.

[0148] Ex9c. The aerosol-generating article according to example Ex9a or Ex9b, wherein the plateau of the first sheet protrusion is spaced from the plateau of the second sheet depression, for example in a z or height direction.

[0149] Ex9d. The aerosol-generating article according to example Ex9 or Ex9a or Ex9b or Ex9c, wherein the first slope of the first sheet protrusion aligns with the second slope of the second sheet depression, for example in an x or length direction and / or in a y or width direction.

[0150] Ex9e. The aerosol-generating article according to example Ex9 or Ex9a or Ex9b or Ex9c or Ex9d, wherein the first slope of the first sheet protrusion is spaced from the second slope of the second sheet depression, for example in a z or height direction.

[0151] Ex10. The aerosol-generating article according to any preceding example, in which the first sheet protrusion has a height of between 0.1 millimetre and 6 millimetres, for example between 0.2 millimetres and 5 millimetres, for example between 0.5 millimetres and 5 millimetres, for example between 1 and 5 millimetres, for example between 2 millimetres and 4 millimetres, for example between 2 millimetres and 3 millimetres.

[0152] Ex11. The aerosol-generating article according to any preceding example, in which the second sheet depression has a depth of between 0.1 millimetre and 6 millimetres, for example between 0.2 millimetres and 5 millimetres, for example between 0.5 millimetres and 5 millimetres, for example between 1 and 5 millimetres, for example between 2 millimetres and 4 millimetres, for example between 2 millimetres and 3 millimetres.

[0153] Ex11 a. The aerosol-generating article according to any preceding example, wherein a length of the first sheet protrusion is less than a length of the first sheet of aerosol-forming substrate and a length of the second sheet depression is less than a length of the second sheet of aerosol-forming substrate.

[0154] Ex12. The aerosol-generating article according to any preceding example, in which the first sheet of aerosol-forming substrate forms multiple first sheet protrusions and the second sheet of aerosol-forming substrate forms multiple second sheet depressions.

[0155] Ex13. The aerosol-generating article according to any preceding example, in which the first sheet is a first corrugated sheet of aerosol-forming substrate forming first corrugations and the second sheet is a second corrugated sheet of aerosol-forming substrate forming second corrugations, in which the first corrugations form the multiple first sheet protrusions and the second corrugations form multiple second sheet depressions.

[0156] Ex14. The aerosol-generating article according to example Ex13, in which the first and second corrugated sheets are defined by a corrugation profile, in which the corrugation profile is sinusoidal, or triangular, or rectangular, or trapezoidal, or toroidal, or parabolic.

[0157] Ex15. The aerosol-generating article according to example Ex13 or Ex14, in which the first and second corrugations extend along a longitudinal axis of the article. Ex16. The aerosol-generating article according to any preceding example, in which at least one of the first sheet and the second sheet is an embossed sheet.

[0158] Ex17. The aerosol-generating article according to example Ex16, in which the embossed sheet comprises a projection from a surface of the embossed sheet, in which the projection is in contact with the other sheet of the first or second sheets to separate the surface from the other sheet of the first or second sheets.

[0159] Ex18. The aerosol-generating article according to example Ex17, in which the projection has a height of between about 10 and about 150 percent of the thickness of the embossed sheet, more preferably between about 25 and about 75 percent of the thickness of the embossed sheet.

[0160] Ex19. The aerosol-generating article according to any preceding example, in which the embossed sheet has a thickness of between about 100 microns and about 300 microns, preferably 200 microns.

[0161] Ex20. The aerosol-generating article according to any preceding example, in which both the first sheet and the second sheet are embossed sheets.

[0162] Ex21. The aerosol-generating article according to any preceding example, in which the first sheet of aerosol-forming substrate comprises a first aerosol-forming material and the second sheet of aerosolforming substrate comprises a second aerosol-forming material.

[0163] Ex22. The aerosol-generating article according to example Ex21 , in which the first aerosol-forming material is different to the second aerosol-forming material.

[0164] Ex23. The aerosol-generating article according to example Ex21 or Ex22, in which at least one of the first aerosol-forming material and the second aerosol-forming material is a homogenised tobacco material.

[0165] Ex24. The aerosol-generating article according to any preceding example, in which at least one of the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate comprises a cellulose fibre, such as hydroxypropyl methylcellulose.

[0166] Ex25. The aerosol-generating article according to any preceding example, comprising a first planar layer, a second planar layer, in which the first sheet of aerosol-forming substrate and the second sheet of aerosolforming substrate are positioned between the first planar layer and the second planar layer.

[0167] Ex26. The aerosol-generating article according to any of examples Ex2 to Ex25, comprising: a cavity, in which the first sheet of aerosol-forming substrate and the second sheet are positioned in the cavity and the at least a portion the airflow path extends through the cavity; a first planar external surface; a second planar external surface; and a frame positioned between the first planar external surface and the second planar external surface, wherein the frame at least partially defines the cavity.

[0168] Ex27. The aerosol-generating article according to example Ex26, wherein the cavity has a cavity length of between 15 and 40 millimetres, a cavity width of between 5 and 13 millimetres, and a cavity height of between 1 .5 and 5 millimetres.

[0169] Ex28. The aerosol-generating article according to example Ex26, wherein the cavity has a cavity length of between 20 and 30 millimetres, a cavity width of between 7 and 10 millimetres, and a cavity height of between 2.5 and 4 millimetres

[0170] Ex29. The aerosol-generating article according to any of examples Ex26 to Ex28, wherein a total mass of aerosol-forming substrate of the aerosol-generating article is contained within the cavity, and the total mass of aerosol-forming substrate of the aerosol-generating article divided by a total volume of the cavity is between 0.1 and 0.4 milligrams per millimetre cubed, preferably wherein the total mass of aerosol-forming substrate of the aerosol-generating article is no more than 250 milligrams.

[0171] Ex30. The aerosol-generating article according to any of examples Ex26 to Ex28, wherein a total mass of aerosol-forming substrate of the aerosol-generating article is contained within the cavity, and the total mass of aerosol-forming substrate of the aerosol-generating article divided by a total volume of the cavity is between 0.3 and 0.7 milligrams per millimetre cubed, preferably wherein the total mass of aerosol-forming substrate of the aerosol-generating article is at least than 250 milligrams.

[0172] Ex31 . The aerosol-generating article according to any preceding example, wherein the aerosol-forming substrate has a true or absolute density of between 0.25 and 1 .8, preferably between 0.35 and 1 .3, more preferably between 0.5 and 1 .1 grams per centimetre cubed.

[0173] Ex32. The aerosol-generating article according to any preceding example, wherein a total mass of aerosol-forming substrate of the aerosol-generating article is between 50 and 700, or between 80 and 500, or between 110 and 400, or between 110 and 300, milligrams.

[0174] Ex33. The aerosol-generating article according to any preceding example, wherein a total mass of aerosol-forming substrate of the aerosol-generating article is between 110 and 250 milligrams. Ex34.

[0175] The aerosol-generating article according to any preceding example, wherein a total mass of aerosol-forming substrate of the aerosol-generating article is between 1 10 and 200 milligrams.

[0176] Ex35. The aerosol-generating article according to any preceding example, wherein a total mass of aerosol-forming substrate of the aerosol-generating article is between 1 10 and 150 milligrams.

[0177] Ex36. An aerosol-generating system comprising: the aerosol-generating article according to any preceding example; and an aerosol-generating device for use with the aerosol-generating article to generate an inhalable aerosol, in which the aerosol-generating device comprises a heater arranged to heat at least part of the aerosol-generating article.

[0178] Examples will now be further described with reference to the figures in which:

[0179] Figure 1 is a perspective side view of an aerosol-generating article according to a first embodiment of the present disclosure;

[0180] Figure 2 is a perspective side view of an aerosol-generating article according to a second embodiment of the present disclosure;

[0181] Figure 3 is a schematic end view of an aerosol-generating article according to a third embodiment of the present disclosure;

[0182] Figure 4 is a schematic side view of the aerosol-generating article of Figure 3;

[0183] Figure 5 is a schematic plan view of the aerosol-generating article of Figure 3;

[0184] Figure 6 shows a schematic illustration of a first sheet of aerosol-forming substrate as used in the aerosol-generating article of Figure 3;

[0185] Figure 7 shows a schematic illustration of a first alternative corrugated element of an aerosolgenerating article of the present disclosure;

[0186] Figure 8 shows a schematic illustration of a second alternative corrugated element of an aerosolgenerating article of the present disclosure;

[0187] Figure 9 shows a schematic illustration of a third alternative corrugated element of an aerosolgenerating article of the present disclosure; Figure 10 is a representation of a trapezoidal corrugation profile;

[0188] Figure 11 is a perspective illustration of an alternative sheet of aerosol-forming substrate of the present disclosure having a surface formed by translating perpendicularly two trapezoidal curves to form a surface having rectangular peaks and troughs;

[0189] Figure 12 is a schematic plan view of Figure 11 illustrating potential air flow paths through peaks and troughs of the surface;

[0190] Figure 13 shows a perspective view of an aerosol-generating article according to a fourth embodiment of the present disclosure;

[0191] Figure 14 shows an exploded perspective view of the aerosol-generating article of Figure 13;

[0192] Figure 15 shows a further exploded perspective view of the aerosol-generating article of Figure 13;

[0193] Figure 16 shows a schematic transverse cross-sectional view of the aerosol-generating article of Figure 13;

[0194] Figure 17 shows a schematic longitudinal cross-sectional view of the aerosol-generating article of Figure 13;

[0195] Figure 18 shows an exploded perspective view of an aerosol-generating article according to a fifth embodiment of the present disclosure;

[0196] Figure 19 shows a schematic transverse cross-sectional view of the aerosol-generating article of figure 18;

[0197] Figure 20 shows a schematic lateral cross-sectional view of the aerosol-generating article of figure 18.

[0198] Figure 21 shows a schematic view of an aerosol-generating device according to an embodiment of the present disclosure, the device configured to engage with an aerosol-generating article, for example the aerosol-generating article of any of figures 1 to 5 or 13 to 20;

[0199] Figure 22 shows a schematic end view of the aerosol-generating device of figure 21 ;

[0200] Figure 23 is a schematic view showing an aerosol-generating article (for example, the aerosolgenerating article of any of figures 1 to 5 or 13 to 20) in engagement with the aerosol-generating device of figure 21 .

[0201] Figure 24 is a schematic view of an alternative embodiment to that of Figure 23, showing an aerosolgenerating article in engagement with an aerosol-generating device.

[0202] Figure 1 illustrates a perspective side view of an aerosol-generating article 100 according to a first embodiment of the present disclosure. The aerosol-generating article 100 has upper and lower surfaces 110, 120 which are flat or planar.

[0203] The aerosol-generating article 100 comprises an aerosol-forming substrate (not shown). In one embodiment, the aerosol-generating article 100 may consist substantially of aerosol-forming substrate. In another embodiment, the aerosol-forming substrate may be one of a plurality of component parts of the aerosol-generating article 100. The aerosol-forming substrate may be enclosed within an interior of the aerosol-generating article 100. The aerosol-forming substrate may at least partially define an exterior of the aerosol-generating article 100; for example, one or both of the upper and lower surfaces 110, 120 may comprise or consist of aerosol-forming substrate.

[0204] A suitable aerosol-forming substrate may be homogenised tobacco. The aerosol-generating article 100 has a length, extending in an x dimension, of 80 millimetres, a width, extending in a y dimension, of 15 millimetres, and a height (which may also be referred to as a thickness), extending in a z dimension, of 3.6 millimetres.

[0205] Figure 2 illustrates a perspective side view of an aerosol-generating article 200 according to a second embodiment of the present disclosure, being a variant of aerosol-generating article 100. Features in common with aerosol-generating article 100 are referred to with like reference signs but commencing with numeral 2 instead of numeral 1 . An air flow path 230 is defined through the aerosol-generating article 200 between the upper and lower surfaces 210, 220. The air flow path 230 extends between opposed first and second ends 201 , 202 of the aerosol-generating article 200. The first end 201 may define a distal end of the aerosol-generating article 200, and the second end 202 may define a proximal or mouth end of the aerosol-generating article. The air flow path 230 may be directed towards a mouth of a user to allow a user to inhale aerosol generated in consequence of heating of aerosol-forming substrate of the aerosolgenerating article 200.

[0206] Figures 3, 4, and 5 illustrate respectively an end view, a side view, and a plan view of an aerosolgenerating article 300 according to a third embodiment of the present disclosure. The aerosol-generating article 300 comprises a planar upper layer 310, a planar lower layer 320, and an intermediate or separation layer 340 arranged between the upper layer 310 and lower layer 320.

[0207] The planar upper layer 310 is formed from a sheet of paper having a thickness of 300 microns. The planar lower layer 320 is formed from a sheet of paper having a thickness of 300 microns.

[0208] The intermediate layer 340 comprises a first sheet of aerosol-forming substrate 345 and a second sheet of aerosol-forming substrate 348 stacked in the z direction. The first sheet of aerosol-forming substrate 345 is a planar sheet shaped to form first sheet protrusions and first sheet depressions in teh form of corrugations. The second sheet of aerosol-forming substrate 348 is a planar sheet shaped to form second sheet depressions and second sheet protrusions in the form of corrugations. Therefore, the first sheet of aerosol-forming substrate 345 is formed from a first corrugated sheet of aerosol-forming substrate forming first corrugations. The second sheet of aerosol-forming substrate 348 is formed from a second corrugated sheet of aerosol-forming substrate forming second corrugations. The first sheet of aerosolforming substrate 345 and the second sheet of aerosol-forming substrate 348 together form a corrugated element.

[0209] A suitable aerosol-forming substrate for both the first and second sheets of aerosol-forming substrate 345, 348 may be homogenised tobacco. Thus, the corrugated element may be formed from corrugated sheets of homogenised tobacco material 345, 348.

[0210] Points of intersection 351 , 352 between the upper layer 310 and the intermediate layer 340 and between the lower layer 320 and the intermediate layer 340 comprise an adhesive that joins the respective layers. In this example, the points of intersection 351 between the upper layer 310 and the first sheet of aerosol-forming substrate 345 and the points of intersection 352 between the lower layer 320 and the second sheet of aerosol-forming substrate 348 comprise an adhesive that joins the respective layers.

[0211] The aerosol-generating article 300 has a length, extending in an x dimension, of 80 millimetres, a width, extending in a y dimension, of 15 millimetres, and a height (or thickness), extending in a z dimension, of 3.6 millimetres. Figure 6 illustrates the first corrugated sheet of aerosol-forming substrate 345. The corrugations have an amplitude 346 of 3 millimetres and a wavelength 347 of 3 millimetres. The amplitude 346 is a peak to peak amplitude. In this example the corrugations are uniform and therefore the height of the first protrusions of the first sheet of aerosol-forming substrate is about 1 .5 millimetres and the height of the first depressions of the first sheet of aerosol-forming substrate is about 1 .35 millimetres. The first sheet of aerosol-forming substrate 345 has a thickness of 0.2 millimetres. In this example, the second corrugated sheet of aerosolforming substrate 348 is identical to the first sheet of aerosol-forming substrate 345. However, it will be appreciated that in other examples, the first sheet of aerosol-forming substrate may be different to the second sheet of aerosol-forming substrate, for example the first aerosol-forming material may comprise a first aerosol-forming material and the second sheet of aerosol-forming substrate may comprise a second aerosol-forming material different to the first aerosol-forming material.

[0212] Corrugations of the first sheet of aerosol-forming substrate 345 of the intermediate layer 340 form a first set of longitudinally extending channels 361 that are bounded by the upper layer 310 and the intermediate layer 340. Corrugations of the second sheet of aerosol-forming substrate 348 of the intermediate layer 340 form a second set of longitudinally extending channels 362 bounded by the lower layer 320 and the intermediate layer 340. The first and second sets of longitudinally extending channels 361 , 362 extend through the length of the first and second sheets of aerosol-forming substrate 345, 348 between a proximal end 371 of the first and second sheets of aerosol-forming substrate 345, 348 and a distal end 372 of the first and second sheets of aerosol-forming substrate 345, 348. The longitudinally extending channels 361 , 362 define an air flow path through the aerosol-generating article 300. The airflow path, therefore, passes over at least one side of the first sheet of aerosol-forming substrate 345 and over at least one side of the second sheet of aerosol-forming substrate 348. The aerosol-generating article along the air-flow path has a resistance to draw (RTD) of less than 20 millimetres H2O.

[0213] During use of the aerosol-generating article 300, the first and second sheets of aerosol-forming substrate 345, 348 are heated up to cause the aerosol-forming substrate to release volatile compounds, which are then entrained in air drawn into the channels 361 , 362 via the distal end 372. The volatile compounds then cool and condense to form an aerosol which may be drawn out of the channels 361 , 362 of the aerosol-generating article 300 via the proximal end 371 .

[0214] Figure 7 shows a schematic illustration of first and second sheets of aerosol-forming substrate 355,

[0215] 358. The first and second sheets are variants of the sheets of Figures 3-6, except where described below. The first sheet of aerosol-forming substrate 355 is formed from a first corrugated sheet of aerosol-forming substrate forming first corrugations. The second sheet of aerosol-forming substrate 358 is formed from a second corrugated sheet of aerosol-forming substrate forming second corrugations. The corrugations of the first sheet and second sheet of aerosol-forming substrate 355, 358 have a sinusoidal corrugation profile.

[0216] The second sheet of aerosol-forming substrate 358 is an embossed sheet comprising projections

[0217] 359. The projections 359 extend from a surface of the second sheet of aerosol-forming substrate 358. The projections 359 contact a surface of the first sheet of aerosol-forming substrate 355 to separate the surface of the second sheet of aerosol-forming substrate 358 from the surface of the first sheet of aerosol-forming substrate 355. The first sheet of aerosol-forming substrate 345 has a thickness of 0.2 millimetres. The second sheet of aerosol-forming substrate 348 has a thickness of 0.2 millimetres. The projections have a height of between 20 percent and 80 percent of the thickness second sheet of aerosol-forming substrate

[0218] 358.

[0219] A portion of an air flow path of an article comprising the first sheet and second sheet of aerosolforming substrate 355, 358 is defined between the first sheet of aerosol-forming substrate 355 and the second sheet of aerosol-forming substrate 358.

[0220] Figure 8 illustrates a schematic illustration of first and second sheets of aerosol-forming substrate. The first and second sheets are variants of the sheets of Figures 3-6, except where described below. The first sheet of aerosol-forming substrate 365 comprises a trapezoidal first sheet protrusion 364. The second sheet of aerosol-forming substrate 368 comprises a trapezoidal second sheet depression 369.

[0221] The first sheet protrusion 364 comprises a first plateau 363 formed at a maximum extension of the first sheet protrusion the second sheet depression 369 forms a second plateau 367 minimum of the second sheet depression. The first plateau 363 and the second plateau 367 are aligned.

[0222] The first sheet protrusion 364 comprises a slope extending to the first plateau 363. The second sheet depression 369 comprises a slope extending to the second plateau 367. The slope of the first sheet protrusion 364 is different to the slope of the second sheet depression 369. In the example, the slope of the first sheet protrusion 364 is steeper than the slope of the second sheet depression 369, as shown.

[0223] A portion of an air flow path of an article comprising the first sheet and second sheet of aerosolforming substrate 365, 368 is defined between the first sheet of aerosol-forming substrate 365 and the second sheet of aerosol-forming substrate 368.

[0224] Figure 9 illustrates a schematic illustration of first and second sheets of aerosol-forming substrate. The first and second sheets are variants of the sheets of Figures 3-8, except where described below. The first sheet of aerosol-forming substrate 375 is formed from a first corrugated sheet of aerosol-forming substrate forming first corrugations. The second sheet of aerosol-forming substrate 378 is formed from a second corrugated sheet of aerosol-forming substrate forming second corrugations. The corrugations of the first sheet and second sheet of aerosol-forming substrate 375, 378 have a trapezoidal corrugation profile. The first sheet of aerosol-forming substrate 375 forms a first plateau formed at a maximum of the first sheet protrusion and the second sheet of aerosol-forming substrate 378 forms a second plateau formed at a minimum ofthe second sheet depression. The first plateau and the second plateau are aligned.

[0225] Both the first sheet of aerosol-forming substrate 375 and the second sheet of aerosol-forming substrate 378 are embossed. The first sheet of aerosol-forming substrate 375 comprises projections 379 extending from a surface of the sheet of aerosol-forming substrate 375. The second sheet of aerosolforming substrate 378 also comprises projections 379 extending from a surface of the second sheet of aerosol-forming substrate 378. The projections 379 of the second sheet of aerosol-forming substrate 378 contact a surface of the first sheet of aerosol-forming substrate 375 to separate the surface of the second sheet of aerosol-forming substrate 378 from the surface of the first sheet of aerosol-forming substrate 375. It will be understand that a further sheet of aerosol-forming substrate could be stacked on top of the first sheet of aerosol-forming substrate 375, in the same way.

[0226] In this example, the first sheet of aerosol-forming substrate 375 has the same thickness as the second sheet of aerosol-forming substrate 378. The projections 379 have a height of between 20 percent and 80 percent of the thickness of the first and second sheets of aerosol-forming substrate 375, 378. Figures 10, 11 and 12 illustrate a schematic illustration of a first or second sheet of aerosol-forming substrate.

[0227] Figure 10 illustrates a continuous trapezoidal curve 380. This trapezoidal curve 380 may be translated perpendicularly with itself to create a surface 390, shown in Figure 11. The surface 390 comprises a plurality of upwardly extending truncated pyramidical pillars 384, which may be referred to as the substrate sheet protrusions. The surface 390 further comprises a plurality of downwardly depending truncated pyramidical pillars 389, which may be referred to as the substrate sheet depressions.

[0228] Figure 11 illustrates a perspective view of the surface 390. The surface 390 may be used as an intermediate or separation layer of an aerosol-forming article as disclosed herein. Preferably, an aerosolgenerating article may comprise a first sheet of aerosol-forming substrate having the form of the surface 390 and a second sheet of aerosol-forming substrate also having the form of the surface 390.

[0229] Figure 12 illustrates potential air flow paths that may be formed within an aerosol-generating article comprising an intermediate layer such as a sheet of aerosol-forming substrate having the form of the surface 390.

[0230] Figure 13 shows an aerosol-generating article 400 according to a fourth embodiment of the present disclosure. The aerosol-generating article 400 comprises a first planar external layer 424 forming a first planar external surface 421 , a second planar external layer 425 forming a second planar external surface 422, and a frame 450 positioned between the first planar external layer 424 and the second planar external layer 425. The second planar external surface 422 is positioned parallel to the first planar external surface 421.

[0231] Figures 14 and 15 show exploded views of the aerosol-generating article 400 of Figure 13. The frame 450 circumscribes and at least partially defines a cavity 430. Figure 13 shows the cavity 430 in an empty state. Figure 15 shows the cavity 430 containing aerosol-forming substrate 440. Figures 16 and 17 show respective transverse and longitudinal cross-sectional views of the aerosol-generating article 400 when the cavity 430 contains aerosol-forming substrate 440.

[0232] The first planar external layer 424 and the second planar external layer 425 are made from cigarette paper having a thickness of 35 micrometres and are in physical contact, with and bonded to, the frame 450. The first planar external layer 424 overlies a first end of the cavity 430 and forms a first cavity end wall 431 . The second planar external layer 425 overlies a second end of the cavity 430 and forms a second cavity end wall 432, the second cavity end wall 432 being opposite to the first cavity end wall 431 . That is, the frame 450, the first planar external layer 424 and the second planar external layer 425 collectively define the cavity 430.

[0233] The frame 450 has a hollow cuboid shape and is made from cardboard. The frame 450 defines an aperture extending through the height (also referred to as the thickness) of the frame 450 and the aperture at least partially forms the cavity 430 of the aerosol-generating article 400. The frame 450 comprises a peripheral wall 451 that circumscribes the cavity 430. The peripheral wall 451 includes a front wall 413 and a back wall 414. In more detail, the peripheral wall 451 is defined by an inner transverse surface 452 of the frame 450 and an outer transverse surface 453 of the frame 450. The inner transverse surface 452 of the peripheral wall 451 at least partially defines a perimeter of the cavity 430. The outer transverse surface 453 of the peripheral wall 451 at least partially defines a perimeter of the aerosol-generating article 400. The peripheral wall 451 has a radial thickness measured between the inner transverse surface 452 of the frame 450 and the outer transverse surface 453 of the frame 450 of about 5 millimetres.

[0234] An air inlet 411 and an air outlet 412 are defined by, and extend through, the peripheral wall 451 of the frame 450. More specifically, the air inlet 411 extends through the front wall 413 and the air outlet 412 extends through the back wall 414. The air inlet 411 and the air outlet 412 have an equivalent diameter of 5 millimetres. An airflow passage extends between the air inlet 411 and the air outlet 412 through the cavity 430. As shown in Figures 15 to 17, an aerosol-forming substrate 440 is positioned within the cavity 430. The aerosol-forming substrate 440 may be any aerosol-forming substrate as described herein. For example, the aerosol-forming substrate 440 may comprise a first sheet of aerosol-forming substrate and a second sheet of aerosol-forming substrate. It should be understood that any of the first and second sheets of aerosol-generating substrate described in relation to Figures 3 to 12 may form the aerosol-forming substrate 440 situated in the cavity 430.

[0235] The aerosol-generating article 400 has a cuboid shape and has a height (or thickness) extending in a z dimension, as measured between the first planar external surface 421 and the second planar external surface 422, of 8 millimetres, a width extending in a y dimension of 40 millimetres and a length extending in an x dimension of 60 millimetres. The frame 450 has a height (or thickness) extending in a z dimension of 7.93 millimetres, a width extending in a y dimension of 40 millimetres and a length extending in an x dimension of 60 millimetres. The cavity 430 has a height (or thickness) extending in a z dimension of 7.93 millimetres, a width extending in a y dimension of 30 millimetres and a length extending in an x dimension of 50 millimetres.

[0236] Figure 18 shows an aerosol-generating article 500 according to a fifth embodiment of the present disclosure. Features in common with aerosol-generating article 400 are referred to with like reference signs but commencing with numeral 5 instead of numeral 4. Aerosol-generating article 500 differs from aerosolgenerating article 400 in that the aerosol-forming substrate is in the form of a first sheet of aerosolgenerating forming substrate 545 and a second sheet of aerosol-generating forming substrate 548. Both the first sheet of aerosol-generating forming substrate 545 and the second sheet of aerosol-generating forming substrate 548 are corrugated sheets of homogenised tobacco material. Figures 19 and 20 show respective transverse and lateral cross-section views of the aerosol-generating article 500 of Figure 18.

[0237] The first sheet of aerosol-generating forming substrate 545 comprises a plurality of parallel corrugations having a plurality of substantially parallel peaks 543 and troughs 544. The plurality of parallel corrugations are defined by a corrugation profile which, as seen in Figure 19, is sinusoidal. The second sheet of aerosol-generating forming substrate 548 also comprises a plurality of parallel corrugations having a plurality of substantially parallel peaks 542 and troughs 549. The plurality of parallel corrugations are defined by a corrugation profile which, as seen in Figure 19, is sinusoidal. The plurality of parallel corrugations of both the first sheet of aerosol-generating forming substrate 545 and the second sheet of aerosol-generating forming substrate 548 have a corrugation wavelength of about 4.6 millimetres. The corrugation amplitude of the corrugations of the first sheet of aerosol-generating forming substrate 545 and the second sheet of aerosol-generating forming substrate 548 is the same as each other. The peaks 543 coincide with the first cavity end wall 531 and the troughs 549 coincide with the second cavity end wall 532.

[0238] The plurality of parallel corrugations form a plurality of channels 561 between the first sheet of aerosol-generating forming substrate 545 and the first cavity end wall 531 , and a plurality of channels 562 between the second sheet of aerosol-generating forming substrate 548 and the second cavity end wall 532. The plurality of channels 561 , 562 extend in a longitudinal direction of the aerosol-generating article 500 and form at least a portion of the airflow path extending between the air inlet 511 and the air outlet 512. Another portion of the airflow path is defined between the first sheet of aerosol-generating forming substrate 545 and the second sheet of aerosol-generating forming substrate 548.

[0239] During use of each of the aerosol-generating articles 400, 500, the aerosol-forming substrate 440, 545, 548 is heated up to cause the aerosol-forming substrate 440, 545, 548 to release volatile compounds, which are then entrained in air drawn through the air inlet 411 , 51 1 into the cavity 430, 530. The volatile compounds then cool and condense to form an aerosol which may be drawn out of the aerosol-generating article 400, 500 through the air outlet 412, 512.

[0240] Figures 21 and 22 illustrate an aerosol-generating device 6000 configured for use with an aerosolgenerating article 600 comprising or consisting of aerosol-forming substrate 640. The device 6000 is an elongate aerosol-generating device extending between a proximal end 6001 and a distal end 6002. The device 6000 comprises a battery 6010, a controller 6020 and a heater 6030 located within a housing 6040. The controller 6020 controls supply of power from the battery 6010 to the heater 6030. A cavity 6050 is defined in the device 6000, the cavity having an opening 6051 defined in the proximal end 6001 of the device. The opening 6051 is rectangular in shape and is dimensioned to accommodate the transverse cross-section of the aerosol-generating article 600. The cavity 6050 comprises an upper planar surface 6052 and a lower planar surface 6053. The heater 6030 is located in the lower planar surface 6053 to heat a lower surface of the aerosol-generating article 600 inserted into the cavity 6050. An air-flow path is configured to allow air to flow into the cavity 6050 from outside the device 6000.

[0241] Figure 23 illustrates the device 6000 of figure 21 in engagement with the aerosol-generating article 600. There is little tolerance between outer surfaces of the aerosol-generating article 600 and the internal surfaces of the cavity 6050. Thus, there is a snug fit between the aerosol-generating article 600 and the device 6000. As the RTD of the aerosol-generating article 600 is negligible, the RTD of the system formed by the combination of aerosol-generating article 600 and aerosol-generating device 6000 is controlled by the air-flow path defined within the device. When a user has inserted the aerosol-generating article 600 into the cavity 6050, the device 6000 can be operated. The heater 6030 heats a lower surface of the aerosolgenerating article 600, and as a result the aerosol-forming substrate 640 of the aerosol-generating article 600 is heated. Volatile components of the aerosol-forming substrate 640 are evaporated and condense in longitudinal air-flow channels defined within the aerosol-generating article 600 to form an aerosol. The user inhales the aerosol by drawing on the proximal end 601 of the aerosol-generating article 600. Once the aerosol-generating substrate 640 of the aerosol-generating article 600 has been depleted of volatile components, the aerosol-generating article is removed from the cavity 6050 of the device 6000 and disposed of. The aerosol-generating article 600 may be any one of the aerosol-generating articles 100, 200, 300, 400, 500 previously described or any other aerosol-generating article of the present disclosure. The aerosol-forming substrate 640 may comprise any one of the sheets of aerosol-forming substrate 345, 348, 355, 358, 365, 368, 375, 378, 385, 545, 548 previously described or any other aerosol-forming substrate of the present disclosure.

[0242] Although figure 23 shows part of the aerosol-generating article 600 extending outside of the aerosolgenerating device 6000, in other embodiments the entirety of an aerosol-generating article may be wholly enclosed within an aerosol-generating device. By way of example, figure 24 illustrates an alternative embodiment to that of figure 23, with like features referred to by the same reference numbers but with the addition of a prime symbol For the alternative embodiment of figure 24, the entirety of aerosol-generating article 600’ is enclosed within the interior of aerosol-generating device 6000’. For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term “about”. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number “A” is understood as “A” ± 10% of “A”. Within this context, a number “A” may be considered to include numerical values that are within general standard error for the measurement of the property that the number “A” modifies. The number “A”, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which “A” deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. The terms “in which” and “wherein” are used synonymously through this specification.

Claims

Claims1 . An aerosol-generating article for use with an aerosol-generating device to generate an aerosol, the aerosol-generating article comprising: a first planar layer; a second planar layer; a first sheet of aerosol-forming substrate forming a first sheet protrusion; and a second sheet of aerosol-forming substrate forming a second sheet depression, wherein the first sheet and second sheet are stacked such that at least a portion of the first sheet protrusion is accommodated within at least a portion of the second sheet depression, and at least a portion of the first sheet protrusion is in contact with at least a portion of a surface of the second sheet depression, and wherein the first sheet of aerosol-forming substrate and the second sheet of aerosol-forming substrate are positioned between the first planar layer and the second planar layer.

2. The aerosol-generating article according to claim 1 comprising an air inlet, an air outlet and an airflow path defined between the air inlet and the air outlet, wherein at least a portion of the airflow path is defined between the first sheet and the second sheet.

3. The aerosol-generating article according to claim 2 comprising: a cavity, wherein the first sheet of aerosol-forming substrate and the second sheet are positioned in the cavity and the at least a portion the airflow path extends through the cavity; a first planar external surface; a second planar external surface; and a frame positioned between the first planar external surface and the second planar external surface, wherein the frame at least partially defines the cavity.

4. The aerosol-generating article according to claim 1 or 2 or 3, wherein the first sheet of aerosolforming substrate is a planar sheet shaped to form the first sheet protrusion and the second sheet of aerosol-forming substrate is a planar sheet shaped to form the second sheet depression.

5. The aerosol-generating article according to any preceding claim, wherein the aerosol-generating article is defined by an article length extending in an x-direction, an article width extending in a y-direction, and an article thickness extending in a z-direction, wherein the article thickness is less than each of the article width and the article length.

6. The aerosol-generating article according to claim 5, in which the first sheet and the second sheet are stacked in the z-direction.

7. The aerosol-generating article according to any preceding claim, wherein the first sheet protrusion has a height of between 0.1 millimetres and 6 millimetres, for example between 0.2 millimetres and 5 millimetres, for example between 0.5 millimetres and 5 millimetres, for example between 1 and 5 millimetres, for example between 2 millimetres and 4 millimetres, for example between 2 millimetres and 3millimetres, and the second sheet depression has a depth of between 0.1 millimetres and 6 millimetres, for example between 0.2 millimetres and 5 millimetres, for example between 0.5 millimetres and 5 millimetres, for example between 1 and 5 millimetres, for example between 2 millimetres and 4 millimetres, for example between 2 millimetres and 3 millimetres.

8. The aerosol-generating article according to any preceding claim, wherein a length of the first sheet protrusion is less than a length of the first sheet of aerosol-forming substrate and a length of the second sheet depression is less than a length of the second sheet of aerosol-forming substrate, wherein the length of the first sheet protrusion extends in the same direction as the length of the first sheet of aerosol-forming substrate and the length of the second sheet depression extends in the same direction as the length of the second sheet of aerosol-forming substrate.

9. The aerosol-generating article according to any preceding claim, wherein the first sheet is a first corrugated sheet of aerosol-forming substrate forming first corrugations and the second sheet is a second corrugated sheet of aerosol-forming substrate forming second corrugations, in which the first corrugations form the multiple first sheet protrusions and the second corrugations form multiple second sheet depressions.

10. The aerosol-generating article according to any preceding claim, wherein at least one of the first sheet and the second sheet is an embossed sheet, wherein the embossed sheet comprises a projection from a surface of the embossed sheet, wherein the projection is in contact with the other sheet of the first or second sheets to separate the surface from the other sheet of the first or second sheets.

11. The aerosol-generating article according to claim 10, wherein the projection has a height of between about 10 and about 150 percent of the thickness of the embossed sheet, more preferably between about 25 and about 75 percent of the thickness of the embossed sheet.

12. The aerosol-generating article according to any of claims 10 or 11 , wherein both the first sheet and the second sheet are embossed sheets.

13. The aerosol-generating article according to any preceding claim, wherein the first sheet of aerosolforming substrate comprises a first aerosol-forming material and the second sheet of aerosol-forming substrate comprises a second aerosol-forming material.

14. The aerosol-generating article according to any preceding claim, wherein the first sheet protrusion extends with a first slope and the second sheet depression extends with a second slope different to the first slope so as to allow the first sheet and second sheet to be stacked but prevent the second sheet depression from being fully occupied with the first sheet protrusion, so a gap is formed between the second sheet depression and the first sheet protrusion..

15. An aerosol-generating system comprising: the aerosol-generating article according to any preceding claim; andan aerosol-generating device for use with the aerosol-generating article to generate an inhalable aerosol, in which the aerosol-generating device comprises a heater arranged to heat at least part of the aerosol-generating article.

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