Method of forming a substrate

Abstract

The present invention relates to a method of forming a substrate. The invention also relates to substrates obtained or obtainable from the method, and uses of said substrates. In particular, the inventions relates to a method of producing a laser induced substrate, the method comprising: providing a precursor substrate comprising carbon; and tracing a laser over a surface of the precursor substrate at a velocity Lv, wherein Lv is selected based on a predetermined relationship with a target sheet resistance Rs target of the laser induced substrate.

Description

[0001] METHOD

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method of forming a substrate. The invention also relates to substrates obtained or obtainable from the method, and uses of said substrates.

[0004] BACKGROUND TO THE INVENTION

[0005] Substrates having particular surface characteristics can be important for a range of applications. For example, substrates with characteristics such as high surface areas, high thermal conductivity and high chemical stability may find use in arrange of applications including ranging from energy storage to biosystems.

[0006] Graphene is a material which has attracted particular interest in a number of fields, since it can display one or more of the above mentioned characteristics (as well as others). Whilst there a number of ways to produce graphene, including epitaxial growth, chemical vapour deposition (CVD) and chemical stripping, laser induced formation of graphene has grained traction owing to its ability to be conducted at ambient temperatures and in a relatively controllable manner.

[0007] Nevertheless, it would be desirable to develop a method of producing a laser induced substrate whereby it is possible to predictably control one of more characteristics of the resulting substrate.

[0008] SUMMARY OF THE INVENTION

[0009] In one aspect, the present invention relates to a method of producing a laser induced substrate, the method comprising:

[0010] providing a precursor substrate comprising carbon; and tracing a laser over a surface of the precursor substrate at a velocity (Lv), wherein Lvis selected based on a predetermined relationship with a target sheet resistance Rstarget of the laser induced substrate.

[0011] In particular, it has been found that the sheet resistance Rsof the produced substrate can be predictably controlled based on the velocity of the laser over the surface of the substrate (Lv). As a result of identifying this, by selecting a target Lvwhich is based on a predetermined relationship with Rstarget it has been possible to reliably prepare substrates having an Rswith greater certainty, thus reducing experimental effort, time and cost.

[0012] In a further aspect, there is provided a laser induced substrate, the substrate being obtained or obtainable by:

[0013] providing a precursor substrate comprising carbon; and

[0014] tracing a laser over a surface of the precursor substrate at a velocity (Lv), wherein Lvis selected based on a predetermined relationship with a target sheet resistance Rstarget of the laser induced substrate.

[0015] In a further aspect there is provided a heater comprising the laser induced substrate disclosed herein.

[0016] In a further aspect there is provided a sensor comprising the laser induced substrate disclosed herein.

[0017] In a further aspect there is provided an apparatus for producing a laser induced substrate, the apparatus comprising:

[0018] a laser; and

[0019] a controller configured to operate the laser, the controller comprising a processor configured to operate the laser at a velocity (Lv), wherein Lvis selected based on a predetermined relationship with a target sheet resistance Rstarget of the laser induced substrate. In a further aspect there is provided an array of components, each component comprising a portion of laser induced substrate, wherein the sheet resistance Rsof each laser induced substrate for each component varies by no more than + / - 5% between the array of components.

[0020] In a further aspect there is provided a computer program comprising instructions which when the program is executed by a computer, cause the computer to carry out the steps of operating a laser by tracing a laser over a surface of the precursor substrate at a velocity (Lv), wherein Lvis selected based on a predetermined relationship with a target sheet resistance Rstarget of the laser induced substrate.

[0021] While the disclosure is susceptible to various modifications and alternative forms, specific approaches are shown by way of example in the drawings and are herein described in detail. It should be understood however that the drawings and detailed description are not intended to limit the disclosure to the particular form disclosed but rather the disclosure is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the claimed invention.

[0022] It will be recognised that the features of the disclosure can conveniently and interchangeably be used in any suitable combination.

[0023] BRIEF DESCIPTION OF THE FIGURES

[0024] Figure 1 shows an output of modelled peak temperature at the incident point of the laser (Tp, °C) to fluence of the laser (J / mm2);

[0025] Figure 2 shows a plot of sheet resistance (Rs, Ohm.sq) versus velocity of the laser (Lv, mm / s)

[0026] DETAILED DESCRIPTION Method of forming a laser induced substrate

[0027] In one aspect, the present invention relates to a method of producing a laser induced substrate, the method comprising:

[0028] providing a precursor comprising carbon; and

[0029] tracing a laser over a surface of the precursor at a velocity (Lv),

[0030] wherein Lvis selected based on a predetermined relationship with a target sheet resistance Rstarget of the laser induced substrate.

[0031] As will be generally understood by one skilled in the art, lasers can be used to induce photothermic and / or photochemical breaking of chemical bonds between atoms on the surface of a substrate. Once broken, the atoms may form new bonds with different atoms so as to create a new substrate. The process of using lasers to induce photothermic and / or photochemical bond rearrangement has found particular use in the formation of graphene substrates.

[0032] Whilst graphene made via conventional epitaxial or chemical stripping methods generally would have a “2D” hexagonal lattice arrangement of carbon atoms, graphene prepared via laser induction often adopts a distorted arrangement of 6-member rings. Accordingly, the parameters employed when conducting the laser induced substrate formation can affect the surface morphology and thus characteristics.

[0033] Typical parameters that may be modified according to a method of producing a laser induced substrate include laser type, laser power, laser velocity, laser beam width, and laser wavelength. One or more of these parameters can be combined to produce other parameters which are useful in characterizing how the laser is applied to the substrate. For example, fluence is a measure of the energy that is delivered to the surface over a particular area and velocity. The present inventors have found that it is possible to reliably control the sheet resistance Rsof the produced substrate by controlling the velocity at which the laser traces over a surface of the substrate precursor (Lv). In particular, it has been found that Lvis a key parameter which can be controlled whilst still allowing for variability in other parameters, such as laser power.

[0034] Predetermined relationship - Lv

[0035] Lv is the velocity at which the laser traces across the surface of the precursor, and its units are mm / s. Any references to Lvin the present application are in mm / s.

[0036] In one embodiment, the predetermined relationship is at least a 2ndorder polynomial relationship. By at least a 2ndorder polynomial relationship it is meant that the relationship is a 2nd, 3rd, 4th, or higher order polynomial relationship. It is preferred that it is a 2ndorder polynomial relationship, since this relationship gives a high level of predictability when it comes to achieving Rstarget.

[0037] When the predetermined relationship is a 2ndorder polynomial relationship, the 2ndorder polynomial relationship conforms to formula (1):

[0038] Rs target= ALv2mm / s + BLvmm / s + C Formula (1)

[0039] Formula (1) contains coefficients A and B, and constant C.

[0040] In one embodiment, coefficient A conforms to: 1,3e’4< A < 1,8e’4. In one embodiment, coefficient A conforms to: 1,4e-4< A < 1,8e’4. In one embodiment, coefficient A conforms to: 1.5e-4≤ A ≤ 1.8e-4. In one embodiment, coefficient A conforms to: 1.6e-4≤ A ≤ 1.8e-4. In one embodiment, coefficient A conforms to: 1.7e-4< A < 1,8e’4. In one embodiment, coefficient A conforms to: 1,3e’4< A < 1,7e’4. In one embodiment, coefficient A conforms to: 1,3e’4< A < 1,6e’4. In one embodiment, coefficient A conforms to: 1,3e’4< A < 1,5e’4. In one embodiment, coefficient A conforms to: 1,3e’4< A < 1,4e’4. In one embodiment, coefficient A conforms to: 1,4e-4< A < 1,7e’4. In one embodiment, coefficient A conforms to: 1,5e’4< A < 1,6e’4. In one embodiment, coefficient A conforms to: 1,6e’4< A < 1,7e’4.

[0041] It is generally preferred that coefficient A conforms to 1.5e-4≤ A ≤ 1.7e-4with a view to providing a greater level of controllability of Rsfor the produced substrate. In this regard, is particularly preferred that coefficient A conforms to 1,55e’4< A < 1,70e’4. It is highly preferred that A is 1,675e’4.

[0042] In one embodiment, coefficient B conforms to: 5e’2< B < 10e’2. In one embodiment, coefficient B conforms to: 5e’2< B < 9.5e’2. In one embodiment, coefficient B conforms to: 5e-2≤ B ≤ 9e-2. In one embodiment, coefficient B conforms to: 5e-2≤ B ≤ 8.5e-2. In one embodiment, coefficient B conforms to: 5e-2≤ B ≤ 8.0e-2. In one embodiment, coefficient B conforms to: 5e-2≤ B ≤ 7.5e-2. In one embodiment, coefficient B conforms to: 5.5e’2< B < 10e’2. In one embodiment, coefficient B conforms to: 6e’2< B < 10e’2. In one embodiment, coefficient B conforms to: 6.5e’2< B < 10e_2. In one embodiment, coefficient B conforms to: 7e’2< B < 10e’2. In one embodiment, coefficient B conforms to: 5.6e’2< B < 7.5e’2. In one embodiment, coefficient B conforms to: 5.7e-2≤ B ≤ 7.5e-2. In one embodiment, coefficient B conforms to: 5.8e-2≤ B ≤ 7.5e-2. In one embodiment, coefficient B conforms to: 5.9e_2< B < 7.5e’2. In one embodiment, coefficient B conforms to: 6.0e’2< B < 7.5e’2. In one embodiment, coefficient B conforms to: 6.1e’2< B < 7.5e’2. In one embodiment, coefficient B conforms to: 6.2e’2< B < 7.5e’2. In one embodiment, coefficient B conforms to: 6.3e’2< B < 7.5e’2. In one embodiment, coefficient B conforms to: 6.4e_2< B < 7.5e’2. In one embodiment, coefficient B conforms to: 6.5e’2< B < 7.5e’2. In one embodiment, coefficient B conforms to: 6.6e’2< B < 7.5e’2. In one embodiment, coefficient B conforms to: 6.7e-2≤ B ≤ 7.5e-2. In one embodiment, coefficient B conforms to: 6.8e-2≤ B ≤ 7.5e-2. In one embodiment, coefficient B conforms to: 6.9e’2< B < 7.5e’2. In one embodiment, coefficient B conforms to: 7.0e’2< B < 7.5e_2. In one embodiment, coefficient B conforms to: 5.5e’2< B < 7.4e’2. In one embodiment, coefficient B conforms to: 5.5e’2< B < 7.3e’2. In one embodiment, coefficient B conforms to: 5.5e’2< B < 7.2e’2. In one embodiment, coefficient B conforms to: 6.5e’2< B < 7.1e’2. In one embodiment, coefficient B conforms to: 5.5e-2≤ B ≤ 7.0e-2.

[0043] It is generally preferred that coefficient B conforms to 6.9e-2≤ B ≤ 7.5e-2with a view to providing a greater level of controllability of Rsfor the produced substrate. In this regard, is particularly preferred that coefficient B confirms to 6.95e’4< B < 7.10e’2. It is highly preferred that B is 6.3412e-2.

[0044] In one embodiment, constant C conforms to 2.0 ≤ C ≤ 12. In one embodiment, constant C conforms to 3 ≤ C ≤ 12. In one embodiment, constant C conforms to 3.5 ≤ C ≤ 12. In one embodiment, constant C conforms to 4 ≤ C ≤ 12. In one embodiment, constant C conforms to 4.5 ≤ C ≤ 12. In one embodiment, constant C conforms to 5 ≤ C ≤ 12. In one embodiment, constant C conforms to 5.5 ≤ C ≤ 12. In one embodiment, constant C conforms to 6 ≤ C ≤ 12. In one embodiment, constant C conforms to 6.5 ≤ C ≤ 12. In one embodiment, constant C conforms to 7 ≤ C ≤ 12. In one embodiment, constant C conforms to 7.5 ≤ C ≤ 12. In one embodiment, constant C conforms to 8 ≤ C ≤ 12. In one embodiment, constant C conforms to 8.5 ≤ C ≤ 12. In one embodiment, constant C conforms to 9 ≤ C ≤ 12. In one embodiment, constant C conforms to 9.5 ≤ C ≤ 12. In one embodiment, constant C conforms to 10 ≤ C ≤ 12. In one embodiment, constant C conforms to 10.5 ≤ C ≤ 12. In one embodiment, constant C conforms to 11 ≤ C ≤ 12. In one embodiment, constant C conforms to 2 ≤ C ≤ 11. In one embodiment, constant C conforms to 2 ≤ C ≤ 10.5. In one embodiment, constant C conforms to 2 ≤ C ≤ 10. In one embodiment, constant C conforms to 2 ≤ C ≤ 9.5. In one embodiment, constant C conforms to 2 ≤ C ≤ 9. In one embodiment, constant C conforms to 2 ≤ C ≤ 8.5. In one embodiment, constant C conforms to 2 ≤ C ≤ 8. In one embodiment, constant C conforms to 2 ≤ C ≤ 7.5. In one embodiment, constant C conforms to 2 ≤ C ≤ 7. In one embodiment, constant C conforms to 2 ≤ C ≤ 6.5. In one embodiment, constant C conforms to 2 ≤ C ≤ 6. In one embodiment, constant C conforms to 2 ≤ C ≤ 5.5. In one embodiment, constant C conforms to 2 ≤ C ≤ 5. In one embodiment, constant C conforms to 2 ≤ C ≤ 4.5. In one embodiment, constant C conforms to 2 ≤ C ≤ 4. In one embodiment, constant C conforms to 2 ≤ C ≤ 3.5.

[0045] In one embodiment, constant C conforms to 3 ≤ C ≤ 11. In one embodiment, constant C conforms to 4 ≤ C ≤ 10. In one embodiment, constant C conforms to 5 ≤ C ≤ 9. In one embodiment, constant C conforms to 6 ≤ C ≤ 8. In one embodiment, constant C conforms to 8 ≤ C ≤ 11.5. In one embodiment, constant C conforms to 9 ≤ C ≤ 11.5. In one embodiment, constant C conforms to 9.5 ≤ C ≤ 11. It is preferred that constant C conforms to 9.0 ≤ C ≤ 11.5.

[0046] It is highly preferred that C is 11.763.

[0047] Combinations of the above ranges for coefficient A and B and constant C are expressly envisaged.

[0048] In particular, in one embodiment the 2ndorder polynomial relationship conforms to formula (1):

[0049] Rs target= ALv2mm / s + BLvmm / s + C Formula (1)

[0050] wherein A, B and C are as follows:

[0051] 1.6e-4≤ A ≤ 1.7e-4;

[0052] 6.0e-2≤ B ≤ 7.0e-2; and

[0053] 1.0e1≤ C ≤ 1.2e1.

[0054] In particular, in one embodiment the 2ndorder polynomial relationship conforms to formula (1):

[0055] Rs target= ALv2mm / s + BLvmm / s + C Formula (1)

[0056] wherein A, B and C are as follows: 1.5e-4≤ A ≤ 1.7e-4;

[0057] 6.9e-2≤ B ≤ 7.5e-2; and

[0058] 1.0e1≤ C ≤ 1.1e1.

[0059] In particular, in one embodiment the 2ndorder polynomial relationship conforms to formula (1):

[0060] Rs target = ALV2mm / s + BLv mm / s+ C Formula (1)

[0061] wherein A, B and C are as follows:

[0062] 1.55e-4≤ A ≤ 1.70e-4;

[0063] 6.95e’4< B < 7.10e’2; and

[0064] 1.05e1≤ C ≤ 1.10e1.

[0065] In particular, in one embodiment, the 2ndorder polynomial relationship conforms to formula (1):

[0066] Rs target = ALV2mm / s+ BLv mm / s + C Formula (1 )

[0067] wherein A is 1.675e-4, B is 6.3412e-2, and C is 1.1763e1.

[0068] Lvmay be constant or Lvmay be variable throughout the method. Preferably Lvis constant throughout the method whilst adhering to the predetermined relationship with Rs target.

[0069] In some examples, Lvis a velocity of from about 75mm / s to 1000mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 1000mm / s. In one embodiment, Lvis a velocity of from about 125mm / s to 1000mm / s. In one embodiment, Lvis a velocity of from about 150mm / s to 1000mm / s. In one embodiment, Lvis a velocity of from about 175mm / s to 1000mm / s. In one embodiment, Lvis a velocity of from about 200mm / s to 1000mm / s. In one embodiment, Lvis a velocity of from about 225mm / s to 1000mm / s. In one embodiment, Lvis a velocity of from about 250mm / s to 1000mm / s. In one embodiment, Lvis a velocity of from about 275mm / s to 1000mm / s. In one embodiment, Lvis a velocity of from about 300mm / s to 1000mm / s. In one embodiment, Lvis a velocity of from about 325mm / s to 1000mm / s. In one embodiment, Lvis a velocity of from about 350mm / s to 1000mm / s. In one embodiment, Lvis a velocity of from about 375mm / s to 1000mm / s. In one embodiment, Lvis a velocity of from about 400mm / s to 1000mm / s. In one embodiment, Lvis a velocity of from about 425mm / s to 1000mm / s. In one embodiment, Lvis a velocity of from about 455mm / s to 1000mm / s. In one embodiment, Lvis a velocity of from about 475mm / s to 1000mm / s. In one embodiment, Lvis a velocity of from about 500mm / s to 1000mm / s.

[0070] In one embodiment, Lv is a velocity of from about 100mm / s to 975mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 950mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 925mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 900mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 875mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 850mm / s. In one embodiment, Lv is a velocity of from about 100mm / s to 825mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 800mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 775mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 750mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 725mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 700mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 675mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 650mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 625mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 600mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 575mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 550mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 525mm / s. In one embodiment, Lvis a velocity of from about 100mm / s to 500mm / s.

[0071] In one embodiment, Lvis a velocity of from about 200mm / s to 800mm / s. In one embodiment, Lvis a velocity of from about 300mm / s to 700mm / s. In one embodiment, Lvis a velocity of from about 400mm / s to 600mm / s.

[0072] In one embodiment, Lvis about 75mm / s. In one embodiment, Lvis about 100mm / s. In one embodiment, Lv is about 125mm / s. In one embodiment, L is about 150mm / s In one embodiment, Lv is about 175mm / s. In one embodiment, L is about 200mm / s In one embodiment, Lv is about 225mm / s. In one embodiment, L is about 250mm / s In one embodiment, Lv is about 275mm / s. In one embodiment, L is about 300mm / s In one embodiment, Lv is about 325mm / s. In one embodiment, L is about 350mm / s In one embodiment, Lv is about 375mm / s. In one embodiment, L is about 400mm / s In one embodiment, Lv is about 425mm / s. In one embodiment, L is about 450mm / s In one embodiment, Lv is about 475mm / s. In one embodiment, L is about 500mm / s In one embodiment, Lv is about 525mm / s. In one embodiment, L is about 550mm / s In one embodiment, Lv is about 575mm / s. In one embodiment, L is about 600mm / s In one embodiment, Lv is about 625mm / s. In one embodiment, L is about 650mm / s In one embodiment, Lv is about 675mm / s. In one embodiment, L is about 700mm / s In one embodiment, Lv is about 725mm / s. In one embodiment, L is about 750mm / s In one embodiment, Lv is about 775mm / s. In one embodiment, L is about 800mm / s In one embodiment, Lv is about 825mm / s. In one embodiment, L is about 850mm / s In one embodiment, Lv is about 875mm / s. In one embodiment, L is about 900mm / s In one embodiment, Lvis about 925mm / s. In one embodiment, Lvis about 950mm / s. In one embodiment, Lvis about 975mm / s. In one embodiment, Lvis about 1000mm / s.

[0073] It will be appreciated that the laser beam may power-off between adjacent scanning lines. Sheet resistance - Rs

[0074] Sheet resistance is measured in Ohm.sq and is typically used to described the resistance of essentially 2D surfaces. The result of the laser impacting the surface of the precursor is to modify the sheet resistance Rsof the substrate.

[0075] The target sheet resistance Rstarget is the desired sheet resistance of the substrate following the performance method.

[0076] Rs target can be selected such that 10 < Rstarget ≤ 250 Ohm.sq. In one embodiment, 10 < Rstarget < 750 Ohm.sq. In one embodiment, 10 < Rs target < 500 Ohm.sq. In one embodiment, 10 < Rstarget ≤ 250 Ohm.sq. In one embodiment, 10 < Rstarget < 100 Ohm.sq. In one embodiment, 10 < Rstarget < 75 Ohm.sq. In one embodiment, 10 < Rs target — 50 Ohm.sq. In one embodiment, 10 < Rs target < 25 Ohm.sq.

[0077] It will be appreciated that constant “C” can also be used to define the lower limit for the sheet resistance, and so the values of C noted above are directly applicable to the lower end of the ranges specified above.

[0078] Peak temperature at the incident point of the laser (Tp)

[0079] As the laser traces the surface of the precursor, the surface temperature of the precursor increases. It has been found that the peak temperature at the incident point of the laser (TP) can to some extent influence the conformity of the predetermined relationship between Lvand Rs target.

[0080] In particular, it can be preferred that the method is performed such that the peak temperature at the incident point of the laser (TP) conforms to 1400°C < TP< 3000°C. It is preferred that 1500°C < TP< 2500°C, more preferably 1600°C < TP< 2000°C. From the view point of ensuring that the sheet resistance Rsof the produced substrate is + / - 10% of Rstarget it is preferred that the peak temperature at the incident point of the laser (TP) is 2500°C or less, 2400°C or less, 2300°C or less, 2200°C or less, 2100°C or less, or preferably 2500°C or less.

[0081] In one embodiment of the present invention, the predetermined relationship is such that the sheet resistance Rsof the produced substrate is + / - 10% of Rstarget. In one embodiment of the present invention, the predetermined relationship is such that the sheet resistance Rsof the produced substrate is + / - 9% of Rstarget. In one embodiment of the present invention, the predetermined relationship is such that the sheet resistance Rsof the produced substrate is + / - 8% of Rstarget. In one embodiment of the present invention, the predetermined relationship is such that the sheet resistance Rsof the produced substrate is + / - 7% of Rstarget. In one embodiment of the present invention, the predetermined relationship is such that the sheet resistance Rsof the produced substrate is + / - 6% of Rstarget. In one embodiment of the present invention, the predetermined relationship is such that the sheet resistance Rsof the produced substrate is + / - 5% of Rstarget. In one embodiment of the present invention, the predetermined relationship is such that the sheet resistance Rsof the produced substrate is + / - 4% of Rstarget.

[0082] Fluence

[0083] In one embodiment, the laser delivers a fluence to the surface of the precursor of from about 0.10 J / mm2to about 0.80 J / mm2.

[0084] It will be appreciated that lasers (sometimes referred to herein as laser beams) can have varying intensity profiles. For example, Gaussian laser beams have a Gaussian intensity profile, whereas flat top laser beams have a substantially constant intensity profile. Herein, “fluence” refers to the amount of energy delivered by the laser beam to the portion of the outer surface per unit area. Those skilled in the art will readily understand how to determine and specify the fluence of the laser beam. Herein, where the laser beam has a Gaussian intensity profile, the fluence of the laser beam is determined using the 1 / e2beam diameter of the laser beam.

[0085] For example, fluence may be represented by the following formula:

[0086] Power

[0087] Fluence = — - - - - - - Velocity x beam diameter

[0088] wherein fluence is the amount of energy delivered by the laser beam per unit surface area, power is the power of the laser beam, velocity is the velocity of the laser beam across the surface of the precursor (sometimes referred herein to scanning speed of the laser beam), and beam diameter is the beam diameter (e.g. 1 / e2) of the laser beam. As discussed herein, where the laser beam has a Gaussian intensity profile the beam diameter is the 1 / e2beam diameter.

[0089] In some examples, the laser beam delivers a fluence to the surface of the precursor of from about 0.10 J / mm2to about 0.60 J / mm2. In some examples, the laser beam delivers a fluence to the surface of the precursor of from about 0.14 J / mm2to about 0.54 J / mm2. In some examples, the laser beam delivers a fluence to the surface of the precursor of from about 0.25 J / mm2to about 0.35 J / mm2. In some examples, the laser beam delivers a fluence to the surface of the precursor of from about 0.30 J / mm2to about 0.35 J / mm2.

[0090] In some examples, the laser beam irradiates the surface of the precursor along one or more scanning lines. In some examples, the laser beam irradiates the surface of the precursor along a plurality of scanning lines. The scanning lines may be straight. The scanning lines may be curved. The scanning lines may form a scanning pattern. It will be understood that the scanning pattern superposes at least a portion of the surface of the precursor.

[0091] In some examples, the fluence is substantially constant. In some examples, in the fluence is variable. In particular, the fluence may vary along a single scanning line, or between multiple scanning lines. Thus, it can be said that the fluence of the laser varies with the position of the laser on the substrate.

[0092] The scanning pattern may comprise a plurality of lines (e.g. straight lines), which may be arranged side-by-side. Adjacent scanning lines may be spaced apart from each other. Adjacent scanning lines may be contiguous with each other. Adjacent scanning lines may overlap each other. The peak intensity of the laser beam is delivered at the centre point (or central axis) of the scanning line. In some examples, the centre point (or central axis) of adjacent scanning lines are spaced apart by a distance which is approximately equal to the beam diameter (1 / e2) of the laser beam.

[0093] In some examples, adjacent scanning lines are overlapping (to provide a region of overlap), such that the region of overlap is subjected to at least about 13.5% of the peak intensity of the later beam. In some examples, adjacent scanning lines are overlapping, such that the region of overlap is subjected to at least about 20% of the peak intensity of the later beam. In some examples, adjacent scanning lines are overlapping, such that the region of overlap is subjected to at least about 40% of the peak intensity of the later beam. In some examples, adjacent scanning lines are overlapping, such that the region of overlap is subjected to at least about 50% of the peak intensity of the later beam. In some examples, adjacent scanning lines are overlapping, such that the region of overlap is subjected to at least about 60% of the peak intensity of the later beam. In some examples, adjacent scanning lines are overlapping, such that the region of overlap is subjected to at least about 80% of the peak intensity of the later beam. In some examples, adjacent scanning lines are overlapping, such that the region of overlap is subjected to at least about 90% of the peak intensity of the later beam. It will be appreciated that the laser beam may power-off between adjacent scanning lines.

[0094] Power

[0095] In some examples, the laser has a power (P) of from 1 W to about 30 W. In some examples, the laser has a power (P) of from about 3 W to about 25 W. In some examples, the laser beam has a power (P) of from about 6 W to about 21 W.

[0096] It is a particular advantage of the present invention that Rstarget can be selected, follow by Lv(based on the predetermined relationship). Thereafter, the appropriate power can be selected depending on other considerations. For example, where it is desired that the peak temperature at the incident point of the laser (TP) is to be controlled, one Lv has been selected it is possible to simply select the appropriate laser power.

[0097] In this respect, the present inventors have completed further modelling of the peak temperature at the incident point of the laser (TP) and how it can be influenced by Lvand the laser power (P).

[0098] In this respect, once Lv has been selected, the P can be selected so as to ensure that the peak temperature at the incident point of the laser (TP) remains within acceptable limits. For example, where TPis too low, e.g. below 1350°C, the surface of the precursor may not undergo sufficient transformation. On the other hand, where TPis too high, e.g. above 3000°C, the substrate may start to degrade.

[0099] It is possible to select P by modelling the peak temperature at the incident point of the laser (TP) and by choosing a P value for a given Lvthat corresponds to the selected TP. For example, reference is made to Figure 1 whereby the relationship between TPand fluence has been modelled for a range of power (P) settings. Such modelling can be carried out using software available to one skilled in the art, such as from COMSOL, Inc. As can be seen from Figure 1, it is possible to select an appropriate P value once the Lvvalue has been selected. For example, if a particular Lvof 350mm / s has been selected based on the predetermined relationship with Rstarget so as to give an Rstarget of 50Ohm.sq, consideration can then be given to the desired TP. If TPwas desired to be, say, 2000°C the power P could be tuned so as to give the desired TP. According to the modelling shown in Figure 1, such a value for P would be around 13Wto 14W.

[0100] It will be appreciated that establishment of the predetermined relationship between an Rstarget and Lv allows for the parameters of the laser to be quickly and easily preselected, thus allowing for automation of the method which can lead to advantages in cost and reducing in waste materials (since trial and error is reduced).

[0101] Alternatively to performing specific modelling, it has also been found that a particular relationship between Lvand P can be used to even more quickly select P. In one embodiment, following selection of Lvaccording to the predetermined relationship, P is selected based on 0.02 < P / Lv0.08. A higher ratio (towards 0.08) will typically lead to TPtending towards 3000°C, whilst a lower value ratio (towards 0.02) will typically lead to TPtending towards 1300°C.

[0102] Accordingly, in one embodiment, following selection of Lvaccording to the predetermined relationship, P is selected based on 0.02 < P / Lv0.08.

[0103] In one embodiment, P is kept constant during each scanning line. In one embodiment, P is kept constant for every scanning line. In one embodiment, P is varied between one or more scanning lines.

[0104] Other laser parameters Those skilled in the art will appreciate that other properties of the laser beam may be varied. For example, those skilled in the art will appreciate that a particular value of fluence can be provided using varying combinations of laser beam parameters. Such laser beam parameters include, for example, wavelength and beam diameter.

[0105] One of the advantages of the presence invention is that a number of these parameters can be varied whilst still being able to reliably produce substrates with Rstarget.

[0106] In some examples, the laser is an infrared laser. In some examples, the laser is a carbon dioxide laser.

[0107] In some examples, the method is preferably performed using a carbon dioxide laser, such as a Keyence ML-Z9610 laser system. It will be appreciated that other laser systems may be used. In some examples, the laser beam has a Gaussian intensity profile. In some example, in the laser beam has a substantially constant intensity profile.

[0108] In some examples, the laser beam has a wavelength of from about 8 µm to about 16 µm. In some examples, the laser beam has a wavelength of from about 9 µm to about 14 µm. In some examples, the laser beam has a wavelength of from about 10 µm to about 12 µm (e.g. about 10.6 µm).

[0109] In some examples, the laser beam has a beam diameter (1 / e2) of from about 120 µm to 160 µm. In some examples, the laser beam has a beam diameter (1 / e2) of from about 130 µm to 150 µm. In some examples, the laser beam has a beam diameter (1 / e2) of from about 135 µm to 145 µm (e.g. about 140 µm). The term “beam diameter (1 / e2)” will be understood by the skilled person.

[0110] Any of the laser beam parameters may be combined with any other features of the method. In some examples, in addition to Lvbeing selected based on the predetermined relationship, the laser has: a wavelength of from about 8 µm to about 16 µm; a beam diameter (1 / e2) of from about 120 µm to 160 µm; and / or a power of from about 1 W to about 30 W.

[0111] In some examples, in addition to Lvbeing selected based on the predetermined relationship, the laser has: a wavelength of from about 9 µm to about 14 µm; a beam diameter (1 / e2) of from about 130 µm to 150 µm; and / or a power of from about 6 W to about 21 W.

[0112] In some examples, in addition to Lvbeing selected based on the predetermined relationship, the laser has: a wavelength of from about 10 µm to about 12 µm; a beam diameter (1 / e2) of from about 135 µm to 145 µm; and / or a power of from about 6 W to about 21 W.

[0113] Precursor

[0114] In some examples, the precursor is selected from the group comprising polyimides, polyetherketones, polysulfones, or a combination thereof.

[0115] In some examples, the polyimides are selected from the group comprising polyetherimides, polyamideimides, or a combination thereof. In some examples, the precursor is a polyimide.

[0116] In some examples, the polyimide is poly(4,4'-oxydiphenylene-pyromellitimide).

[0117] Poly(4,4'-oxydiphenylene-pyromellitimide) is commercially available from DuPont under the trade name Kapton® HN (and other Kapton® products). In some examples, the polyetherketones are selected from the group comprising polyetheretherketones, polyetherketoneketone, polyether ether ketone ketone, polyetherketoneetherketoneketone, or a combination thereof.

[0118] In some examples, the polysulfones are selected from the group comprising poly(arylene sulfone), poly(bisphenol-A sulfone), polyether sulfone, polyphenylenesulfone, poly(oxy-1,4- phenylenesulfonyl-1,4-phenylene), or a combination thereof.

[0119] In some examples, the precursor is flexible.

[0120] In some examples, the precursor is non-porous. For example, when the precursor is a polyimide, the polyimide may be non-porous. It is to be understood that “non-porous” may encompass embodiments in which at least one through-hole is formed through the precursor. In this way, the term “non-porous” can be considered as referring to the skeletal portion (or matrix) of the precursor. Such through-holes can be effectively ignored in relation to the assessment of whether the precursor is non-porous (where these do not form the matrix of the precursor).

[0121] The precursor may be provided in various forms. In particular, the precursor has a surface which is exposed to the laser during the method. This surface can be referred to as the first surface. The first surface may be substantially planar.

[0122] In some examples, the substrate may comprise a second surface. The second surface may be opposite from the first surface (herein “an opposing second surface”). The second surface may be substantially planar.

[0123] In some examples, the precursor is substantially planar.

[0124] In some examples, the substrate comprises a substantially planar first surface and a substantially planar second surface that is opposite from the first surface. In some examples, the precursor has a thickness of from about 40 pm to about 500 pm. Herein, the thickness of the precursor is measured orthogonally to the plane or lateral extent of the precursor, e.g. from the first surface to the second surface.

[0125] In some examples, the precursor has a thickness of from about 40 pm to about 300 pm. In some examples, the precursor has a thickness of from about 80 pm to about 300 pm. In some examples, the precursor has a thickness of from about 90 pm to about 200 pm. In some examples, the precursor has a thickness of from about 100 pm to about 150 pm. In some examples, the precursor has a thickness of from about 120 pm to about 130 pm.

[0126] Any of the thickness features may be combined with any other features of the carbon precursor. For example, in some examples, the precursor is substantially planar, the outer surface comprising a substantially planar first surface and an opposing substantially planar second surface, wherein the thickness of the precursor is from about 90 pm to about 200 pm, optionally from about 100 pm to about 150 pm, optionally from about 120 pm to about 130 pm, optionally wherein the precursor 101 is a polyimide.

[0127] Laser induced substrate

[0128] In a further aspect, there is provided a laser induced, the substrate obtained or obtainable by:

[0129] providing a precursor substrate comprising carbon; and

[0130] tracing a laser over a surface of the precursor substrate at a velocity (Lv), wherein Lvis selected based on a predetermined relationship with a target sheet resistance Rstarget of the laser induced substrate.

[0131] The laser induced substrate may be characterized by any of the features of the method. For example, the substrate may be derived from a precursor which is selected from the group comprising polyimides, polyetherketones, polysulfones, or a combination thereof.

[0132] In some examples, the polyimides are selected from the group comprising polyetherimides, polyamideimides, or a combination thereof. In some examples, the precursor is a polyimide.

[0133] In some examples, the polyimide is poly(4,4'-oxydiphenylene-pyromellitimide).

[0134] Poly(4,4'-oxydiphenylene-pyromellitimide) is commercially available from DuPont under the trade name Kapton® HN (and other Kapton® products).

[0135] In some examples, the polyetherketones are selected from the group comprising polyetheretherketones, polyetherketoneketone, polyether ether ketone ketone, polyetherketoneetherketoneketone, or a combination thereof.

[0136] In some examples, the polysulfones are selected from the group comprising poly(arylene sulfone), poly(bisphenol-A sulfone), polyether sulfone, polyphenylenesulfone, poly(oxy-1,4- phenylenesulfonyl-1,4-phenylene), or a combination thereof.

[0137] In some examples, the laser induced substrate is flexible.

[0138] In some examples, the laser induced substrate is non-porous. For example, when the laser induced substrate is a polyimide, the polyimide may be non-porous. It is to be understood that “non-porous” may encompass embodiments in which at least one through-hole is formed through the laser induced substrate. In this way, the term “non-porous” can be considered as referring to the skeletal portion (or matrix) of the laser induced substrate. Such through-holes can be effectively ignored in relation to the assessment of whether the laser induced substrate is non-porous (where these do not form the matrix of the laser induced substrate). In some examples, the laser induced substrate is substantially planar.

[0139] In some examples, the laser induced substrate comprises a substantially planar first surface and a substantially planar second surface that is opposite from the first surface.

[0140] In some examples, the laser induced substrate has a thickness of from about 5 pm to about 500 pm. Herein, the thickness of the laser induced substrate is measured orthogonally to the plane or lateral extent of the laser induced substrate, e.g. from the first surface to the second surface.

[0141] In some examples, the laser induced substrate has a thickness of from about 5 pm to about 300 pm. In some examples, the laser induced substrate has a thickness of from about 10 pm to about 300 pm. In some examples, the laser induced substrate has a thickness of from about 20 pm to about 300 pm. In some examples, the laser induced substrate has a thickness of from about 80 pm to about 300 pm. In some examples, the laser induced substrate has a thickness of from about 90 pm to about 200 pm. In some examples, the laser induced substrate has a thickness of from about 100 pm to about 150 pm. In some examples, the laser induced substrate has a thickness of from about 120 pm to about 130 pm.

[0142] Any of the thickness features may be combined with any other features of the laser induced substrate. For example, in some examples, the laser induced substrate is substantially planar, the outer surface comprising a substantially planar first surface and an opposing substantially planar second surface, wherein the thickness of the laser induced substrate is from about 90 pm to about 200 pm, optionally from about 100 pm to about 150 pm, optionally from about 120 pm to about 130 pm, optionally wherein the laser induced substrate 101 is derived from a polyimide.

[0143] The laser induced substrate may be considered to comprise graphene. In this regard, graphene is understood to be an allotrope of carbon. Depending on the method used to produce the graphene, different structures can be formed. Whilst graphene made via conventional epitaxial or chemical stripping methods generally would have a “2D” hexagonal lattice arrangement of carbon atoms, graphene prepared via laser induction often adopts a distorted arrangement of 6-member rings. Accordingly, the parameters employed when conducting the laser induced substrate formation can affect the surface morphology and thus characteristics. Therefore, reference to “graphene” in the context of the present invention should not be considered to be limited strictly to having a “2D” hexagonal lattice arrangement of carbon atoms.

[0144] Resistance

[0145] The laser induced substrate can also have a particular resistance, i.e. (the resistance is non-zero). In one embodiment, the laser induced substrate has a resistance of up to 1000 Ohms. In one embodiment, the laser induced substrate has a resistance of up to 750 Ohms. In one embodiment, the laser induced substrate has a resistance of up to 500 Ohms. In one embodiment, the laser induced substrate has a resistance of up to 250 Ohms. In one embodiment, the laser induced substrate has a resistance of up to 100 Ohms. In one embodiment, the laser induced substrate has a resistance of up to 75 Ohms. In one embodiment, the laser induced substrate has a resistance of up to 50 Ohms. In one embodiment, the laser induced substrate has a resistance of up to 25 Ohms. In one embodiment, the laser induced substrate has a resistance of from 1 Ohm to 100 Ohms. In one embodiment, the laser induced substrate has a resistance of from 1 Ohms to 25 Ohms. In one embodiment, the laser induced substrate has a resistance of from 1 Ohms to 15 Ohms.

[0146] The laser induced substrate can be applied in a variety of end uses.

[0147] In particular, in one embodiment, there is provided a heater comprising the laser induced substrate disclosed herein. The heater may be particularly suitable for use as an aerosol generator. In this regard, the precursor can possibly be chosen from carbon containing materials such as PEEK, and such materials may also be used to form components of aerosol generators (such as to the housing, reservoir, heater support or the like).

[0148] Therefore, in one embodiment, the heater is an aerosol generator. The aerosol generator may be coupled to one or more other components to form a cartridge or other component that is used interchangeable with a device part. As mentioned above, since the other components of the cartridge may also be formed from materials such as PEEK it can be possible to reduce the overall number of materials that are required to form the cartridge.

[0149] Therefore, in one aspect there is also provided an article for use in an aerosol generation system, the article comprising a heater formed from the laser induced substrate disclosed herein, and wherein the article comprises less than 4 materials. A “material” as used in this context is a material with a specific underlying chemical structure. For example, PEEK and polyimide would be “different materials”. PEEK is a particular useful material in this context since it is capable of being laser welded to other components.

[0150] For example, the article may comprise a first group of components. The first group of components may comprise the reservoir, the housing, the aerosol generator, and the mouthpiece (where present). The first group of components may be formed from up to four different materials. The first group of components may be formed from up to three different materials. The first group of components may be formed from up to two different materials. The first group of components may be formed from a single material.

[0151] In some examples, one of the materials or the material is a polyimide. In some examples, one of the materials or the material is a polyetheretherketone. In some examples, the materials comprise a polyimide and a polyetheretherketone. In some examples, one of the materials is a polyimide and one of the materials is polyetheretherketone.

[0152] The first group of components may be integrally formed.

[0153] Another advantage of the present invention is that it is not required to use a metal in the formation of the heater. In particular, the laser induced substrate is essentially free from metal and as such it is possible that an aerosol generator and / or article comprising the aerosol generator which is essentially metal free can be produced. This can avoid any unwanted metals being emitted.

[0154] Moreover, due to the very thin substrates that can be produced (and their resulting low thermal mass), it is possible to use the laser induced substrate as an aerosol generator wherein the time it takes for aerosol to be produced from the generator is very short, such as of the order of 200ms or less.

[0155] Therefore, in a further embodiment there is provided an aerosol generator comprising the laser induced substrate described herein, wherein the time to initial aerosol generation is 300ms or less, preferably 200ms or less, or preferably 100ms or less.

[0156] It is also possible to produce an aerosol generator comprising the laser induced substrate described herein, wherein a suitable aerosol mass is created using a small of modest amount of power and in a suitable period of time. For example, aerosol masses of 1 to 15 mg / puff, 1 to 12 mg / puff, 1 to 10 mg / puff, 1 to 7 mg / puff, or 1 to 5 mg / puff may be possible, in a time of 300ms or less, 200ms or less, or 100ms or less. Moreover, the power required to deliver such an aerosol can be modest and range from 1Wto 15W, 1Wto 10W, 1Wto 7Wor 1Wto 6W.

[0157] In one embodiment, there is provided a sensor comprising the laser induced substrate disclosed herein. It will be appreciated by one skilled in the art that the sheet resistance Rsof the laser induced substrate can be varied dependent on the precise needs of the final application, and that the use of the predetermined relationship with Lvis useful to assist in the production of the desired samples.

[0158] Apparatus

[0159] In a further aspect there is provided an apparatus for producing a laser induced substrate, the apparatus comprising:

[0160] a laser; and

[0161] a controller configured to operate the laser, the controller comprising a processor configured to operate the laser at a velocity (Lv), wherein Lvis selected based on a predetermined relationship with a target sheet resistance Rs target of the laser induced substrate.

[0162] The processor may be configured accordingly by comprising a memory comprising a computer program which when executed causes the controller to operate the laser.

[0163] It will be appreciated that the establishment of the predetermined relationship between sheet resistance Rsand Lvallows for automation and controllability of production, leading to reductions in cost and waste, whilst allowing for increases in speed of manufacture. To this end, it is expected that multiple components comprising portions of laser induced substrate will be able to be produced at high speed and with high reliability. This would be advantageous since it would allow for the mass production of components comprising the laser induced substrate. Clearly, mass production typically requires a high degree of conformity between products and as such the establishment of the predetermined relationship can assist in that.

[0164] Therefore, in a further aspect there is provided an array of components, each component comprising a portion of laser induced substrate, wherein the sheet resistance Rsof each laser induced substrate for each component varies by no more than + / - 5% between the array of components.

[0165] In a further aspect there is provided a computer program comprising instructions which when the program is executed by a computer, cause the computer to carry out the steps of operating a laser by tracing a laser over a surface of the precursor substrate at a velocity (Lv), wherein Lvis selected based on a predetermined relationship with a target sheet resistance Rstarget of the laser induced substrate.

[0166] EXAMPLES

[0167] Example 1

[0168] In one example, a range of polyimide samples (4mm x 4mm, 100pm thick) were subjected to a carbon dioxide laser (Keyence ML-Z9610) having: 10.6pm wavelength; 140pm spot diameter (1 / e2); and maximum power output of 30W. The power and velocity (and accordingly the fluence) applied to the samples was varied according to Table 1.

[0169] Once each sample was prepared, its sheet resistance Rs was measured and recorded (as R.sq actual in Table 1). Based on a plot of the actual sheet resistance Rs against the velocity of the laser, it was established that a predetermined relationship between Rsand Lvexisted, and that a 2ndorder polynomial relationship was a particularly good fit (see Figure 2). Based on this relationship, the target values for Rsand Lvcould be selected. As can be seen from Table 1, the deviation in Rsbetween the actual samples and the estimated (based on the predetermined relationship) was small, in the majority of cases less than 6%.

[0170] It is therefore considered that the use of the predetermined relationship to select Lvcan therefore provide a predictable approach to manufacturing laser induced substrates with Rstarget at scale and in an automated fashion. Moreover, the predetermined relationship is found to be particular good at producing the target sheet resistance when TPis less than 2500°C.

[0171] Table 1

[0172] Sample Power Velocity, Fluence R.sq Rs target Deviation of TP(deg.

[0173] (W) Lv (ave., actual (Ohm.sq) Rs target from Celcius) (mm / s) J / mm2) (Ohm.sq) Rsactual (%

[0174] error)

[0175] 1 6 100 0.4286 23.5 19.2 18.1 2302 2 6 150 0.2857 24.4 24.8 -1.4 1732 3 9 200 0.3214 32.9 31.1 5.5 2030 4 12 200 0.4286 25.4 31.1 -22.3 2649 5 12 325 0.2637 48.8 50.5 -3.3 1886 6 12 500 0.1714 87.3 85.9 1.6 1395 7 15 350 0.3061 52.9 54.9 -3.8 2200 8 15 650 0.1648 123.1 124.1 -0.8 1425 9 15 250 0.4286 29.5 38.2 -29.5 2782 10 15 425 0.2521 69.4 69.5 -0.2 1919 11 18 750 0.1714 153.5 153.6 0.0 1521 12 18 500 0.2571 85.1 85.9 -0.9 2020 13 18 300 0.4286 34.3 46.2 -34.8 2888

[0176]

[0177] 14 21 500 0.3000 88.6 85.9 3.0 2310

[0178] Any aspect of the present disclosure may be defined in relation to any of the other aspects of the present disclosure. For example, one aspect of the present disclosure may include any of the features of any other aspect of the present disclosure and / or the features of one aspect of the present disclosure may be as defined in relation to the features of any other aspect of the present disclosure.

[0179] The figures herein are schematic and not drawn to scale. The various examples described herein are presented only to assist in understanding and teaching the claimed features. These examples are provided as a representative sample of examples only, and are not exhaustive and / or exclusive. It is to be understood that advantages, examples, functions, features, structures, and / or other aspects described herein are not to be considered limitations on the scope of the invention as defined by the claims or limitations on equivalents to the claims, and that other examples may be utilised and modifications may be made without departing from the scope of the claimed invention. Various examples of the claimed invention may suitably comprise, consist of, or consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc., other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future.

Claims

CLAIMS1. A method of producing a laser induced substrate, the method comprising: providing a precursor substrate comprising carbon; andtracing a laser over a surface of the precursor substrate at a velocity (Lv), wherein Lvis selected based on a predetermined relationship with a target sheet resistance Rstarget of the laser induced substrate.

2. The method according to claim 1, wherein the predetermined relationship is at least a 2ndorder polynomial relationship.

3. The method according to claim 2, wherein the 2ndorder polynomial relationship conforms to formula (1):Rs target Ohm.sq = ALV2mm / s + BLVmm / s + Cwherein coefficients A and B and constant C are as follows:1.3e-4≤ A ≤ 1.8e-4;5e’2< B < 10e’2; and2 ≤ C ≤ 12.

4. The method according to claim 3, wherein coefficients A and B and constant C are as follows:1.6e’4< A < 1.7e’4;6.0e-2≤ B ≤ 7.0e-2; and10 ≤ C ≤ 12.

5. The method according to any one of the preceding claims, wherein the laser is traced over the surface of the precursor substrate to produce a peak temperature at the incident point of the laser (TP) of 1400°C ≤ TP≤ 3000°C, preferably 1500°C ≤ TP≤ 2500°C, more preferably 1600°C ≤ TP≤ 2000°C.

6. The method according to any one of the preceding claims, wherein Rstarget conforms to 10 < Rstarget ≤ 250 Ohm.sq.

7. The method according to claim 5, wherein Rstarget conforms to 10 Ohm.sq < Rs target ≤ 50 Ohm.sq.

8. The method according to any one of the preceding claims, wherein the laser has a Gaussian beam distribution.

9. The method according to any one of the preceding claims, wherein the laser has a fluence of from about 0.10 J / mm2to about 0.80 J / mm2.

10. The method according to any one of the preceding claims, wherein the laser has a substantially constant peak fluence throughout the method.

11. The method according to any one of claims 1 to 10, wherein the laser has a variable peak fluence throughout the method.

12. The method according to any one of the preceding claims, wherein Lv is 75mm / s ≤ Lv≤ 500mm / s.

13. The method according to any one of the preceding claims, wherein Lvis kept substantially constant throughout the method.

14. The method according to any one of the preceding claims, wherein the laser is a CO2laser.

15. The method according to any one of the preceding claims, wherein the laser has a wavelength in the region of 10-15μm, preferably 10.6μm.

16. The method according to any one of the preceding claims, wherein the laser has a spot diameter of from 130 to 150μm.

17. The method according to any one of the preceding claims, wherein 5W ≤ P ≤ 25W, preferably 6W ≤ P ≤ 21W.

18. The method according to any one of the preceding claims, wherein P is kept substantially constant throughout the method.

19. The method according to any one of the preceding claims, wherein the laser is traced in a plurality of scanning lines.

20. The method according to any one of the preceding claims, wherein the produced laser induced substrate comprises graphene.

21. The method according to any one of the preceding claims, wherein the precursor substrate comprising carbon is selected from polyimide or PEEK.

22. The method according to any one of the preceding claims, wherein each trace of the laser has a path length of from 1mm to 50mm.

23. A laser induced substrate obtained or obtainable by the method of any one of claims 1 to 22.

24. A heater comprising the laser induced substrate of claim 23.

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