AUGMENTATION METHOD

FIELD OF THE INVENTION

The present invention relates to a process and system for modifying the surface of a substrate using a plasma discharge process. More particularly, the present invention relates to a process and system for the scale up of plasma induced surface functionality.

BACKGROUND OF THE INVENTION

It is known that substrates with specific predetermined surface properties can influence biological and related events and testing thereof. For example, the behaviour and response of cells, proteins and biomolecules of various kinds, including those associated with the immune system can be influenced by chemical and structural characteristics and properties. Control of such events may be useful in areas such as medical implants, oncology, stem cell culture, deep vein thrombosis, drug delivery, biomarker identification, etc. Typically, substrates used in any form of diagnosis or treatment have inherent surface properties that will facilitate a form of action with a biological environment or test platform. In order to optimise the interaction between the surface of a substrate and the cells or biomolecules concerned its surface may be treated in some manner. However, in many cases such treatment procedures are lengthy and resource intensive.

The present invention provides an improved method and system for treating a substrate which may be useful in the above field of technology and in other fields of technology such as the nanotechnology sector, e.g. in carbon nanomaterials, biosensors, fuel cells, batteries, nanochemistry, photocatalysis, solar cells, nanoelectronics, and nanoparticles for drug delivery.

The invention can be used to develop a wide range of functional properties, including physical, chemical, electrical, electronic, magnetic, mechanical, wear- resistant and corrosion-resistant properties at the required substrate surfaces. It is also possible to use the process described herein to form coatings of new materials, graded deposits, multi-component deposits, etc. Therefore, the present invention will be of interest to many industries such as automotive, aerospace, missile, power, electronic, biomedical, textile, petroleum, petrochemical, chemical, steel, cement, machine tools and construction industries.

WO 2012/107723A1 describes a plasma based surface augmentation method. The method comprises providing a first electrode and second electrode and arranging a substrate such that only a portion of the substrate is between the electrodes, and rotating either the substrate or at least one of the electrodes about an axis so as to cause different portions of the substrate to pass between the electrodes during rotation.

SUMMARY OF THE INVENTION From a first aspect, the present invention may comprise a method of modifying a substrate using a downstream plasma process, comprising: providing a plasma head comprising a first electrode and a second electrode within a housing, with a gap provided between said first and second electrodes, and said housing having an outlet; supplying a voltage to at least one of the electrodes so as to create a plasma discharge in said electrode gap between the electrodes and within the housing, arranging said substrate to be modified relative to said housing outlet so that in use said plasma discharge travels downstream from said gap between the electrodes, out of the housing outlet and contacts at least a portion of the substrate to be modified, moving said substrate and/or said plasma head so that said substrate and said outlet of said plasma head are displaced relative to each other and wherein said outlet is shaped so as to produce a variation between the surface modification of a first section of said portion of substrate and a second section of said portion of substrate. The method may further comprise rotating the substrate and/or said plasma head about an axis so as to cause different portions of said substrate to pass the plasma head outlet and come into contact with said plasma discharge exiting said outlet during said rotation; and wherein the plasma head and the substrate are arranged such that said rotating causes the speed of transit of the substrate portion passing the plasma head outlet to vary in a radial direction away from the axis of rotation; wherein said plasma head is arranged and said rotation occurs such that said first section of the portion of substrate that is further from the axis of rotation passes a first section of the plasma head outlet and is modified by the plasma discharge at a first rate and said second section of the substrate that is closer to the axis of rotation passes a second section of the plasma head outlet and is modified by the plasma discharge at a second rate that is different to said first rate.

The first rate may be lower than the second rate, and the plasma treatment may alter the surface chemistry of the substrate surface by a different amount in the first section of the portion of substrate to the second section.

The substrate may be arranged on a platen that is rotated about said axis so as to cause rotation of said substrate relative to said plasma head. The plasma head may or may not remain stationary.

In some embodiments, the plasma head may rotate constantly through repeated uninterrupted cycles. The substrate may be arranged on a platen and both the platen and the substrate may remain stationary.

In some methods, due to said relative displacement of the substrate and the plasma head outlet, said first section of the portion of substrate may have a greater residence time in contact with said plasma discharge that is exiting from said outlet during said displacement than said second section of said portion of the substrate.

Some methods may comprise the step of arranging said plasma head above said substrate and wherein due to said relative displacement, said first section of the portion of substrate may have a greater residence time underneath said outlet during said displacement than said second section of said portion of the substrate.

Some methods may comprise the step of moving either the substrate and/or said plasma head such that said substrate and said plasma head and outlet are being linearly displaced relative to each other along an axis of linear displacement during said movement; and wherein said plasma head outlet is arranged relative to said axis of linear displacement such that said linear movement causes said first section of the portion of substrate to have said greater residence time in contact with said plasma discharge stream during said linear displacement than said second section of said portion of the substrate.

Some methods may comprise the step of moving either the substrate and/or said plasma head such that said substrate and said plasma head are being linearly displaced relative to each other along an axis of linear displacement during said movement; and may further comprise the step of rotating either the substrate or said plasma head about an axis of rotation during said relative linear displacement along said axis, so that said first section of the portion of substrate has a greater residence time in contact with said plasma discharge stream than a second section of said portion of substrate.

A system for modifying a substrate using a downstream plasma process is also described herein comprising: a plasma head comprising a first electrode and a second electrode within a housing; with a gap provided between said first and second electrodes, and said housing having an outlet; means for supplying a voltage to at least one of the electrodes so as to create a plasma discharge between the electrodes and within the housing, means for positioning said substrate to be modified so that it is exposed to said outlet of the plasma head; means for directing said plasma discharge stream downstream from said gap between the electrodes, out of the outlet and into contact with at least a first portion of said substrate to be modified; means for moving either the substrate and/or said plasma head so that said substrate and said plasma head and plasma head outlet are being displaced relative to each other; wherein said means for moving said substrate and/or plasma head is moved, and wherein said outlet is shaped so as to be configured to produce a variation between the surface modification of a first section of said portion of substrate and a second section of said portion of substrate.

The system may further comprise means for rotating the substrate and/or said plasma head about an axis so as to cause different portions of said substrate to pass the plasma head outlet and come into contact with said plasma discharge exiting said outlet during said rotation; and the plasma head and the substrate may be arranged such that said rotating causes the speed of transit of the substrate portion passing the plasma head outlet to vary in a radial direction away from the axis of rotation; wherein said plasma head is arranged and said rotation occurs such that said first section of the portion of substrate that is further from the axis of rotation passes a first section of the plasma head outlet and is modified by the plasma discharge at a first rate and said second section of the substrate that is closer to the axis of rotation passes a second section of the plasma head outlet and is modified by the plasma discharge at a second rate that is different to said first rate.

In some systems, the first rate may be lower than the second rate, and the plasma treatment may alter the surface chemistry of the substrate surface by a different amount in the first section of the portion of substrate to the second section.

In some systems said substrate is arranged on a platen that is configured to be rotated about said axis so as to cause rotation of said substrate relative to said plasma head. The plasma head may or may not be configured to remain stationary.

In some systems said plasma head is configured to rotate constantly through repeated uninterrupted cycles. In some systems said substrate is arranged on a platen and is configured to remain stationary.

In some systems, due to said relative displacement, said first section of the portion of substrate may have a greater residence time in contact with said plasma discharge that is exiting from said outlet during said displacement than said second section of said portion of the substrate.

In some systems said plasma head may be positioned above said substrate and due to said relative displacement, said first section of the portion of substrate may b e have a greater residence time underneath said outlet during said displacement than said second section of said portion of the substrate.

Some systems described herein may have means configured to move the substrate and/or plasma head so that said substrate and said plasma head are linearly displaced relative to each other along an axis of displacement during said movement, said plasma head outlet being positioned relative to said axis of displacement such that said linear movement causes a first section of the portion of substrate to have a greater residence time in contact with said plasma discharge stream during said linear displacement than a second section of said portion of the substrate.

In some embodiments, the plasma head outlet may have a non-uniform shape that is arranged relative to the axis of displacement so as to cause this greater residence time in contact with the plasma discharge.

Some systems described herein may have means configured to move the substrate and/or plasma head so that said substrate and said plasma head are linearly displaced relative to each other along an axis of displacement during movement, and further comprising means for rotating either the substrate or said plasma head about an axis of rotation during said relative linear movement, so that a first section of the portion of substrate has a greater residence time between the electrodes than a second section of said portion of substrate. The plasma head outlet may have a shape and may be arranged relative to said axis of displacement such that said shape causes said first section of the portion of substrate to have said greater residence time between the electrodes during said linear displacement than said second section of said portion of the substrate. The plasma head outlet may have a shape and may be arranged relative to said axis of linear displacement such that said shape causes said first section of the portion of substrate to be exposed for a greater distance to the plasma head outlet along said axis of displacement than said second section of said portion of substrate. The plasma head outlet may comprise a first side with a first shaped outlet profile, and said substrate may be positioned relative to said outlet so that said first shaped profile is facing said portion of substrate. Said plasma head outlet may comprise an opening or openings that is/are elongated in shape.

Said plasma head outlet may comprise an opening or openings that have non-linear and/or non-uniform profile.

Said plasma head outlet may comprise an opening or openings that have a profile that is wedge-shaped and/or tapered.

Said plasma head outlet may comprise an opening or openings that has/have a curved profile.

Said plasma head outlet may comprise a plurality of individual plasma head openings or outlets. The plurality of plasma head openings or outlets may differ in size and/or shape from each other.

Said plasma head may be configured to rotate so that said plurality of plasma head openings or outlets rotate about an axis of rotation.

Some systems and methods described herein may comprise a plurality of said plasma heads.

In some systems and methods described herein said substrate may be moved linearly at a first speed along an axis of displacement and said plasma head may be moved at a second speed along said axis of displacement, said first and second speeds being different to each other, so that said portion of said substrate passes said plasma head outlet along said axis of displacement. In some systems and methods described herein said second speed is greater than said first speed.

In some systems and methods described herein said substrate is provided on a platen.

Some systems and methods described herein may comprise a plurality of said platens and said substrate may be provided on said plurality of platens, such that movement of said plurality of platens having said substrate provided thereon causes movement of said substrate and said linear displacement of said substrate and said plasma head outlet or outlets relative to each other.

Said platen may comprise a flexible platen and said flexible platen may have said substrate provided thereon, and the platen and substrate may be moved along said axis of displacement so that said portion of said substrate passes along said axis of movement and past said plasma head outlet or outlets.

Said flexible platen or said plurality of platens may be provided on a platen carousel and said step of linearly displacing said substrate and said plasma head outlet relative to each other may comprise rotating said platen carousel.

Said platen carousel may rotate in a plane that extends along the axis of displacement and also perpendicular to the plane of the substrate and/or platen, to thereby move said plurality of platens linearly along said axis of displacement.

Said substrate may extend from a first reel to a second reel and said substrate and said plasma head may be linearly displaced relative to each other by rotating said first and/or second reel to thereby move said substrate along the axis of

displacement.

In some systems and methods described herein said plasma head is mounted on a plasma head carousel and said substrate and said plasma head are linearly displaced relative to each other by rotating said plasma carousel so that said plasma head moves along said axis of displacement. In some systems and methods described herein said plasma head carousel rotates in a plane that extends along the axis of displacement and also perpendicular to the plane of the substrate and/or platen, to thereby move said plasma head along said axis of displacement.

In some systems and methods described herein said plasma head carousel rotates in a plane that extends parallel to the plane of the substrate and/or platen, to thereby move said plasma head along said axis of displacement. In some systems and methods described herein a potential difference or a current is applied to the electrodes so as to generate the plasma there between, and the magnitude of the current or potential difference may be varied with time.

In some systems and methods described herein a potential difference or a current may be repeatedly applied to the electrodes so as to generate the plasma there between, and the frequency of application of the current or potential difference may be varied with time.

The distance between the first and second electrodes may be dynamically varied with time.

In some systems and methods described herein one or more type of gas may be supplied to the region between the electrodes whilst the plasma is being generated. The one or more gas may comprise or carry at least one type of chemical which modifies the substrate when the plasma is being generated.

In some systems and methods described herein a plurality of different types of gases may be caused to flow into the plasma head outlet or outlets at different flow rates.

In some systems and methods described herein a gas distributor may be provided for supplying one or more types of gas to the region between the electrodes in a non-uniform manner. ln some systems and methods described herein one or more types of gas may be provided at a plurality of loci across the plasma head outlet or outlets.

Some of the systems and methods described herein comprise means or the step of varying the flow rate of one or more types of gas that is exiting the outlet or outlets of the plasma head and contacting the substrate.

Some systems and methods described herein comprise the step of varying the flow rate through different outlets in the plasma head.

In some examples, the plasma head and substrate are located in a chamber.

The plasma treatment may alter the surface chemistry, topography, or morphology of the substrate surface by different amounts in different areas of the substrate.

The plasma may modify the substrate by one or more of the following processes: modifying the substrate surface to include chemical functionalities; depositing monomers or oligomers on the surface; grafting monomers or oligomers on the surface; polymerising monomers or oligomers on the surface; or changing the surface roughness of the substrate.

In some systems and methods described herein the first and/or second electrode is replenished after having been subjected to said plasma.

Some systems and methods described herein may comprise a plurality of plasma heads such that different separate regions of said substrate pass the outlets of the plurality of plasma heads simultaneously.

In some examples, the plasma occurs at or about atmospheric pressure.

In some examples, the plasma is generated by a dielectric barrier discharge process.

In some examples, the gas is supplied non-uniformly across the surface of the substrate. In some examples, the gas is supplied to the substrate through said plurality of plasma head outlets. In some examples, the gas has different flow rates through different openings of the plasma head outlet or outlets.

In some examples, at least one of the electrodes has a conduit and one or more apertures extending from the conduit to the outside of the electrode and said gas is supplied through the conduit so that it flows out of the at least one electrode through said apertures.

In some examples, biomolecules are deposited or immobilized on the substrate. The methods described herein may comprise the subsequent step of vacuum forming the modified substrate to provide a 3-dimensional surface form.

In some examples, the method comprises processing the substrate prior to exposing it to said plasma, said processing being by one or more of the following techniques: 3D printing, additive manufacturing processes, embossing, vacuum forming, lithography, injection moulding, sputtering, chemical treatment (e.g. using silane derivatives), laser ablation, dip coating, spin coating, deposition, spraying, coating, ion beam etching, punching, cutting, mounting, adhering, welding, mechanically fixing or housing in substrate carriers.

In some examples, the method comprises processing the substrate after having exposed it to said plasma, said processing being by one or more of the following techniques: 3D printing, additive manufacturing processes, embossing, vacuum forming, lithography, injection moulding, sputtering, chemical treatment (e.g. using silane derivatives), biomaterial deposition, laser ablation, dip coating, spin coating, deposition, spraying, coating, ion beam etching, punching, cutting, mounting, adhering, welding, mechanically fixing or housing in substrate carriers. BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention will now be described, by way of example only, and with reference to the drawings, in which:

Figure 1 a shows a side cross section of a plasma distributor that may be used with any of the embodiments described herein.

Figure 1 b shows a front cross section of figure a.

Figure 2 shows a cross section of a locally variable flow plasma distributor.

Figure 3 shows a top view of a plasma distributor having two plasma heads each having plasma head outlets with a curved profile.

Figure 4 shows a top view of a rotating plasma head assembly.

Figure 5a shows an alternative example of a plasma head that may be used which has a central electrode.

Figure 5b shows a plasma head having multiple sources of gas flow.

Figure 6 shows a bottom view a plasma head showing a plasma head outlet having a wedge shaped opening of varying cross section.

Figure 7 shows a bottom view a plasma head showing a plasma head outlet having a plurality of individual openings that vary in size from each other.

Figure 8 shows a plurality of plasma heads that may be used together.

Figures 9a and 9b show how a chemical(s) may be introduced into the plasma head.

Figure 10 shows a bottom view of a plasma head outlet having a varying cross section that comprises undulations. Figure 1 shows a variant of a downstream or ion free type plasma head Figure 12 shows a plasma head wherein the electrodes have varying positions.

Figure13 shows a top view of a plasma head arrangement that may be used with the systems and methods of the present invention.

Figure 14 shows a side view of figure 13.

Figure 15 shows a top cross sectional view of an embodiment of the invention showing a plurality of individual outlets or openings.

Figure 16 shows a side view of figure 15.

Figure 17 shows a top cross sectional view of plasma heads having plasma head outlets or openings having non-uniform profiles.

Figure 18 shows a top cross sectional view of plasma heads having plasma head outlets or openings having non-uniform profiles.

Figure 19 shows a side view of an embodiment of the invention wherein the platen and the substrate move in synergy whilst the plasma head moves at a rate different to this.

Figure 20 shows a top view of an embodiment of the invention wherein the plasma heads are mounted on a carousel that rotates the plasma heads about an axis so that they move in a plane that extends generally parallel to the plane of the substrate positioned underneath.

Figure 21 shows a side view of an embodiment of the invention wherein the plasma heads are mounted on a carousel that rotates the plasma heads about an axis so that they move along the axis of displacement and in a plane that extends from the axis of displacement and generally perpendicular to the plane of the substrate positioned underneath. Figure 22 shows a side view of an embodiment of the invention wherein the substrate is mounted and transferred through the process in a start/stop fashion using a form of a reel to reel mechanism.

Figure 23 shows a side view of an example of an embodiment of the assembly where the substrate to be treated with gradient surface functionality is mounted and transferred through the process in a continuous fashion using a form of a reel to reel mechanism.

Figure 24 shows a side view of an example of an embodiment of the assembly comprising many inflexible platen type elements mounted on a carousel that cycles so as to match the speed of transition of the substrate underneath the plasma head(s).

Figure 25 shows a side view of an example of the embodiment shown in figure 24 where the plasma heads and platens are moved simultaneously on carousels.

Figure 26 shows a side view of an embodiment of the invention wherein the platen is flexible in nature and may be continuously cycled through the process.

Figure 27 shows a top view of an embodiment of the invention wherein plasma head assemblies are mounted on a carousel that rotates the plasma heads about an axis so that they move in a plane that extends generally perpendicular to the plane of the substrate positioned underneath and wherein each of the plasma head assemblies further rotates about its own individual line.

Figure 28 shows a side view of a chamber that can be used with any of the embodiments described herein.

Figure 29 shows a side view of an embodiment of the invention wherein the plasma head is replenished continuously or on a start/stop basis. SPECIFIC DESCRIPTION

The present invention relates to a downstream plasma method and apparatus, wherein a main feature of the present invention that is not known from prior downstream methods is the deliberate production of spatially resolute differences in surface functionality. Prior art downstream plasma processes are typically used to produce homogeneous or localised outcomes. They do not produce the amount of different surface outcomes that the present invention can in similar timeframes, i.e. they can't prototype different surface functionalities with the same efficiency. The systems and methods of the present invention described herein may use different techniques such as variations in speed, associated residence time or even power at specific positions to deliver a spatial variation in the treatment condition of the substrate being modified. The present invention therefore allows for the deliberate production of, the condition of or, the outcome from use of a carefully controlled non-uniform surface condition/coating produced using a single sweep process. In the present invention the premise is to induce variation across the plane of treatment in a deliberate and controlled way to benefit from the effect of multiple adjacent outcomes that can be created with a single sweep. The present invention provides an improved method and system for treating a substrate which may be useful in the field of surface modification and in other fields of technology such as the nanotechnology sector, e.g. in carbon nanomaterials, biosensors, fuel cells, batteries, nanochemistry, photocatalysis, solar cells, nanoelectronics, and nanoparticles for drug delivery.

The invention can be used to develop a wide range of functional properties, including physical, chemical, electrical, electronic, magnetic, mechanical, wear- resistant and corrosion-resistant properties at the required substrate surfaces. It is also possible to use the process described herein to form coatings of new materials, graded deposits, multi-component deposits, etc. Therefore, the present invention will be of interest to many industries such as automotive, aerospace, missile, power, electronic, biomedical, textile, petroleum, petrochemical, chemical, steel, cement, machine tools and construction industries. The methods and systems of the present invention specifically use downstream, or ion free, plasma processes, i.e. configurations where the two electrodes are mounted close together in a plasma "head" or housing and the fluid flow is controlled through the electrode gap and out of the outlet in the housing to provide a downstream flow of chemical species.

WO 2012/107723A1 is a document that describes surface modification of a substrate using a rotating platen positioned between two electrodes. As described later, the present invention can also provide surface modification of a substrate that is provided on a rotating platen, however, in contrast to the device described in WO 2012/107723A1 , because the present invention does not have the substrate positioned between the electrodes but instead comprises the arrangement of the two electrodes together in a plasma head that is positioned above the substrate, this provides a system and method that is more flexible in terms of the geometries of surfaces that can be treated using the process. For example the surfaces no longer need to be planar to accommodate movement of the substrate through the electrode gap.

In a first aspect, the present invention may therefore comprise a slot plasma head arranged relative to a substrate holder or platen. In another aspect, the slot plasma head may be held in a fixed position over a rotating sample holder similar to primary embodiments as described in WO 2012/107723A1.

In some embodiments, the slot plasma head may rotate through 360° similar to the embodiments described in WO 2012/107723A1. In some embodiments, the plasma head may rotate constantly through repeated uninterrupted cycles. This is typically not the case in standard systems where the head would normally be limited to restricted rotation. In further embodiments, the plasma discharge flow in the systems and methods of the present invention may be directed internally (within the head) to provide the same type of locally variable flow characteristics that are described in WO

2012/107723A1 , and as described below. In further embodiments, the plasma head and/or substrate may be moved so that they are displaced relative to each other along a linear axis, as described below.

In the embodiments described herein it is also possible to provide multiple heads or jets that are mounted adjacent to each other with the capacity to have different plasma characteristics and therefore provide multiple surface outcome scenarios.

In the embodiments described herein it is also possible to use a single power source for the multiple heads or jets and/or use only different gaseous/fluid conditions within each stream. This would cause differences in surface modification of the substrate being treated.

In some embodiments, fixed, variable or automatically controlled variable resistors may be used in the differentiation of the electrical characteristics in different plasma streams. These are novel high efficiency methods that get a lot of surface outcomes from a single power source.

The processes and systems described herein are for modifying the surface of a substrate using a plasma discharge process and provide a number of ways to effectively control substrate modification.

A typical plasma head 1 that may be used in conjunction with any of the embodiments of the present invention is depicted in figures 1a and 1 b. Figure 1 a depicts a side cross sectional view of the plasma distribution system 10, and figure 1 b shows a front cross section view, with the electrode 12 foremost. The plasma head 1 1 has a housing 19 in which the plasma distributor is positioned, an outlet 20 (which is basically an opening, or plurality of openings, in some cases, as described below) a first electrode 12, and a second electrode 13. A substrate 14 that is to be modified by the plasma deposition process is provided in the vicinity of the plasma head outlet 20 so as to receive the plasma discharge stream produced between the electrodes 12 and 13. As shown in figures 1 a, 1 b and 2, the present invention may comprise at least a first electrode 12 and at least one second electrode 13. The first electrode12 and the second electrode(s) 13 may be positioned relative to each other to provide a gap or space 1 there between, as shown in figure 1a. In the embodiments shown in figure 1 a, the first electrode, 12, can be seen as being positioned beside and parallel to the second electrode(s) 13 to provide this gap 1. A substrate 14, the surface of which is to be modified using a plasma discharge process, is positioned beneath these two electrodes and beneath the plasma head housing outlet 20. The working electrode is therefore arranged at a distance away from the other electrode, to provide this gap, or space, 1 , therebetween.

Although in this figure the substrate is positioned underneath the plasma head 1 1 , with the plasma head above the substrate 14, the systems and methods described in this application are not limited to this and the substrate 14 could alternatively be positioned in any other position such as to the side, or above the plasma head, as long as the plasma discharge stream is able to exit the outlet 20 and contact the substrate 14.

One of the first electrode 12 and second electrode may 13 act as a ground electrode, whilst the other may act as a working electrode. In some embodiments, only one plasma head may be used, however, in any of the embodiments described herein (such as that shown in figure 3 for example), the system may comprise a plurality of plasma heads 1 1 , 1 1a. For example, figure 3 shows a top view of the embodiment of figure 1 , that comprises two plasma heads 1 1 , 11 a each having an outlet with a curved opening 20.

In any of the examples described herein, a gas distributor 15 such as that shown in figure 2 may provide a flow of gas 16 towards the substrate 14 so that the flow 16 travels from the distributor 15 within the housing 19, between the electrodes 12, 13 (i.e. within the electrode gap between the electrodes 12, 13) and to an outlet 20 of the housing 1 1. From the outlet 20 of the housing the gas then flows to the substrate 14 that is to be treated.

In some embodiments described herein, the plasma head may be provided over a platen on which a substrate to be modified is provided, (as shown in figures 14 and 16). In some embodiments such as that shown in figure 4, the plasma head may be rotated about 360 degrees above the substrate. This is similar to the method described and shown in WO 2012/107723A1 except in this embodiment, there is no underlying electrode, as both electrodes are provided in the plasma head itself, as described above. Unlike in WO2012/107723A1 , the substrate is not positioned between the electrodes. The electrodes are positioned inside a plasma head and the substrate is positioned outside of the plasma head and in the vicinity of the plasma head outlet. Figure 5a shows an example of an alternative plasma head wherein the plasma head has a first electrode 2 which is a central electrode, and a second cylindrical electrode, 13, is provided surrounding the central electrode 12. The gas discharge then exits the plasma head through the outlet in the same way as described above with reference to figures 1 to 3.

In some embodiments, the plasma head may have first and second electrodes that have variable positions. For example, in figure 5a the central electrode 12 may be movable Figure 5b depicts a front view of a plasma head wherein there are multiple gas sources provided (specifically in this example, four are shown, although other multiples of gas sources can be used).

Figure 6 depicts a bottom view of a plasma head wherein the plasma head outlet 20 is wedge shaped. In other words, the opening 20 of the outlet is wedge shaped. The outlet is therefore a slot having a large width at one end and smaller width at the other end. This design may therefore produce a different rate and amount of flow at different positions along the length of the plasma head and plasma head outlet. Examples of how this may be used in a linear process are described below with reference to figures 13 to 29. However, this shape outlet may also be used in conjunction with the rotating embodiment depicted in figure 4.

Figure 7 depicts an alternative plasma head wherein the plasma head comprises a plurality of plasma head outlets or openings and wherein the size of the plasma head outlets or openings differ from each other. In this example, the plasma head outlets or openings decrease in size from one end of the bottom of the plasma head to the other, to thereby allow for a different rate and amount of flow at different positions along the length of the plasma head (to thereby produce a similar outcome to that shown in figure 6). Of course, other embodiments may comprise varying sizes along the length of/in varying positions on the section of the plasma head that faces the substrate to be modified.

Figure 8 depicts a plasma head that may be used with any of the embodiments described herein wherein multiple aligned sets of plasma heads are used in conjunction with each other. Variable flow/frequency or power may be used across the different jets and plasma heads.

In some embodiments, a chemical additive may be introduced to the plasma discharge. Figure 9a depicts a side view wherein the chemical additive is introduced into the plasma flow at point 90. The flow of chemical additive into the plasma jet may be varied/variable and figure 9b shows how the chemical additive may be introduced via a plurality of individual inlets and how the flow may be varied between the inlets.

Figure 10 depicts a further example of a plasma head outlet that may be used with any of the embodiments described herein wherein the plasma head outlet is an opening or slot having a non-uniform shape that has a variable cross section or profile, i.e. wherein the edges of the opening or slot comprise undulations.

Figure 1 1 shows a variant of a downstream or ion free type plasma head. It is indicative that the effects described here can be applied across the full extent of ion free/downstream plasma type processes regardless of individual electrode to electrode or electrode to ion capture component relationships. In some

embodiments, the plasma head may rotate about an axis of revolution as shown at the right hand side of the figure.

Any of the different shaped plasma heads/plasma head outlets /openings described herein may be used with either the linear processes and/or rotating process described herein.

In some embodiments, such as those shown in figure 13 to 29, the substrate 14 may be provided on a platen 4 that is movable linearly, along a line, 80, back and forth in first, 81 , and second, 82, opposite directions along this axis of movement, 80. The substrate 14 is mounted, (in the embodiments shown in figures 1 to 4, directly) onto the upper surface of the platen, 4 so that it is positioned beneath the plasma head(s) and so that the plasma discharge created in the housing of the plasma head passes downstream from the gap 1 between the two electrodes 12, 13, though the opening of the outlet in the plasma head(s) and comes into contact with the substrate 14 to be modified. In other examples the substrate may be mounted indirectly and/or a dielectric may be used.

As shown in the embodiments of figures 13 to 16, the substrate 14 may be provided directly on the uppermost surface of the platen 4, (i.e. that which is facing the outlet 20 of the plasma head 1 ) and linear movement of the platen 4 along the axis of movement 80 also results in linear movement of the substrate 14 provided thereon. Due to this movement of the substrate, the substrate and the plasma head are therefore linearly displaced relative to each other along the axis of movement, i.e. axis of linear displacement 80. In these embodiments, the plasma head(s) remain stationary, however, in other embodiments, they may also move, as described later.

Figure 2 shows a cross section of a locally variable plasma distributor that may also be used with the methods and systems of the present invention. Such locally variable plasma distributors as shown in figure 2 may be used to provide separate or individually different flows of gas to the substrate either through one single outlet/opening or multiple outlet/openings, as described later.

As discussed above, a gas distributor15 may be provided to supply gas to the space 1 between the two electrodes 12, 13, in the plasma head, to thereby generate a plasma discharge between the electrodes and a high voltage is applied to at least one of the electrodes so as to create a plasma discharge between the electrodes. This plasma discharge contacts and modifies at least the portion of the substrate 14 that is passing the outlet 20 of the plasma head(s) during the linear movement of the substrate. This region in which the discharge occurs may be accurately controlled to provide variation in discharge power, distribution and number of treatment cycles.

For example, in some embodiments of the present invention, the gas distributor 15 may provide a non-uniform gas distribution as a means of creating enhanced or otherwise unique dielectric barrier discharge operating conditions that can engender well defined localised changes in surface chemistry and/or topography of the substrate. It is also possible to combine a unique form of distributed gas (air or other gas) delivery to the gap 1 between the electrodes (hereinafter referred to as the electrode gap) and movement of the substrate, 14, and/or plasma head(s) under specific speeds and conditions. In essence, the gas (air or other gas) may be presented to the working electrodes, 12, 13, via channels 30 which lead to exit points, 21 , that produce loci of flow (see figure 2).

Figure 15 shows a top view of an embodiment of the present invention, wherein a gas distributor is integrated into the plasma heads 1 1 , 1 1 a, the plasma heads having a curved shape and therefore a plurality of individual openings distributed in a curved shape along the bottom of the plasma head. In figures 2, 15 and 16 a gas distributor 15 may be arranged above the substrate 14, the gas distributor 15 comprising a plurality of channels, 30, which lead to these openings for supplying the plasma discharge at discrete loci. A form of gas distributor comprising a hollow tube for carrying the gas with a plurality of apertures in the tube is described in WO 2012/107723 A1. The apertures deliver the gas to the substrate surface in the plasma discharge region at the loci adjacent to the position of the holes, thus providing localised gas flow at a plurality of points along the substrate surface. This arrangement permits the combined effects of energy dose and gas

flow/concentration to be exercised in the same plane.

In any of the embodiments described herein, the gas distributor may be adapted to provide a varying profile of types and amounts of gases, to provide a general and/or localised variation of the gas condition in proximity to the electrode. This

arrangement changes the plasma conditions across the length of the plasma head in a manner that provides for associated localised variations in the excited species created in these regions and hence varies the degree to which the surface modification occurs in regions proximal to these points. The origin and direction of the gas flow may be adjusted during treatment or between treatments to provide for additional variation in plasma conditions during a treatment or in different treatment situations. In some embodiments, the flow of a gas or gas mixtures into the discharge region is controlled as described in WO 2012/107723 A1. The gas flow may be controlled using mass flow controllers. Each mass flow controller operates in a different flow range (for example up to 20 L/min, 5 L/min, 0.5 L/min, and 0.01 L/min) in order to provide for accurately controlled flow levels and therefore enables delivery of predetermined percentage concentrations of each gas in the final mixture. These mass flow controllers are connected via input lines to the discharge chamber. The mass flow controllers may be operated manually using a suitable control unit or automatically via an appropriate software routine.

In some embodiments four mass flow controllers are controlled by such control units. The line entering each mass flow controller has four solenoid valves controlled via switches. These may also be controlled via computer software. This allows rapid switching of input gases to each of the mass flow controllers and thereby provides the functionality to produce gas mixtures across a very large concentration range. The gas is channelled to flow directly through the electrode gap but can also be directed to purge the chamber. With appropriate gas mixtures a glow discharge may be produced. The types of gases that can be used as well as combinations and ratios thereof are largely unlimited due to the use of a stainless steel and polytetrafluoroethylene (PTFE) based flow control design. Additionally, many liquids in vapour form or solids in aerosol form may be carried to the discharge region using the same flow system using evaporation cells and carrier gases as necessary. This may include, but is not limited to, chemicals such as silanes, allylamine and other functional chemicals, monomers or oligomers (such as polyethylene glycol) suited to deposition and/or grafting or polymerisation.

In some embodiments, the systems and methods described herein may be used in conjunction with a chamber, (although this is not necessary) and in a further embodiment the gas flow conditions can be controlled to allow for blanketing of the entire surface of the platen in order to provide a barrier between the substrate and other chamber gases. In this configuration the requirement for chamber purging prior to sample treatment may be negated. Further plasma heads 1 1 , 1 1 a may be fixed over the platen surface, 4, in order to allow discharges that operate with similar or different electrical conditions (e.g. frequency, voltage, current) to augment substrate surfaces as part of the overall substrate treatment regime.

The electrodes used in the methods and systems described herein may be selected from any one of the known formats used in ion free/downstream type plasma processing configurations. The distance (or size of the gap) 30 between the outlet 20 of the plasma head 1 1 and the upper surface of the substrate 14 to be modified (as shown in at least figure 1 ) may change and may or may not be distinct from the gas gap (between gas distributor 15 and platen 4). Additionally, in tandem or as a separate function, an alternative mechanism can be used to adjust the voltage signal used to set the power level (by changing the voltage across the discharge gap) in a manner that varies this dynamically during processing.

The adjustment of power and/or plasma-substrate gap parameters, in

synchronisation or otherwise, affects the subsequent distribution and specific intensity of treatment zones.

The discharge power may be continuously or discontinuously changed over time throughout a specific region or in a number of different regions. The methods by which gas is made to flow through the discharge region may also be adapted to provide both gradual gradients of flow across the substrate or to create step changes in flow at specified locations. The gas distributor may further be designed in such as way as to provide for flows of different types of gases in close proximity to each other. The variations in plasma head-substrate gap and power can alternatively be achieved in a manner similar to the effects obtained above by using any form of electrode configuration conducive to delivering the effects of DBD processing, e.g. by using gearing and cams connected to the electrode drive system in a linear or reel to reel configuration. This could be considered as an additional form of this invention. Although in the embodiment shown in figures 13 to 16, the linear displacement of the substrate and the plasma head relative to each other is achieved using a plasma head 1 1 that remains stationary while the substrate moves linearly relative to the plasma head and in particular plasma head outlet, in other examples, the platen, and therefore, substrate, may alternatively be kept stationary, and the plasma head(s) may be moved linearly relative to the substrate 14. In further examples, only the substrate 14 may be moved along the line 80 between the two electrodes, both of which remain stationary. In further embodiments (described later) this may also even involve moving both the substrate 14 and the plasma head(s) 1 1 in the same linear direction, 81 , albeit at different speeds to each other (thereby providing relative movement between the substrate and the second electrode). In use, the substrate 14 and/or the plasma head(s) may therefore be described as being moved or displaced linearly relative to each other so that a portion of the substrate 14 that is positioned in the proximity of (e.g. beneath) the outlet 20 of the plasma head(s) moves linearly along the axis of movement or displacement 80 relative to at least the outlet port 20 of the plasma head(s).

As seen in figures 3 and 6, in some embodiments of the present invention, the outlet(s) 20 of the plasma head(s) may comprise an opening(s) in the plasma head having a non-linear and/or non-uniform profile, or cross-section, that in use, faces the substrate 14 to be modified. In the particular embodiments shown in figure 3 the opening of the outlet 20 of the plasma head has an elongated curved profile, although other shaped profiles could be used. For example, figures 6, 17 and 18 show top views of alternative arrangements wherein one or more plasma heads are used which have openings 20 that have different 'wedge' shaped cross sections, or profiles.

In use, the plasma head(s) may be positioned relative to the substrate and the axis of linear displacement so that the cross sectional profile of the opening of the outlet(s) of the plasma head(s) is facing the portion of the surface of the substrate to be treated. As shown in figures 13, 14 and 15, the plasma head(s) may further be positioned relative to the substrate 14 and more particularly to the direction of movement 81 of the substrate, so that the non-linear and/or non-uniform profile results in a first portion of the substrate that is passing between the electrodes having a greater residence time underneath the plasma head outlet(s) than a second portion of the substrate that is also passing underneath the outlet(s).

In the examples shown in figures 13 to 15, this is achieved due to the fact that the plasma head outlet has been positioned relative to the substrate 14 and relative to the axis of movement or displacement 80 of the substrate so that a first section, 61 , of the curved profile of the opening of the plasma head outlet extends for a greater distance above a first section of the portion of substrate being treated than a second section of the portion of substrate being treated as the substrate and second electrode are being linearly displaced relative to each other. In particular, in this example, the first section extends for a greater distance along the same axis of displacement 80 along which the substrate is moving, whereas the second section 62 of the curved profile of the opening of the plasma head outlet extends in a direction that is not in line with the axis of displacement and eventually extends in a direction that is generally perpendicular transverse to the linear direction of movement of the substrate.

A first section of the substrate that passes beneath the outlet and in particular, under this first portion 61 of the outlet would therefore experience a greater residence time underneath the plasma head outlet and therefore in contact with the plasma discharge as the substrate is moved linearly in the first direction 81 as compared to the section of substrate that passes under the second section 62 of the outlet In the examples shown in figure 17 on the other hand, the outlet(s) of the plasma head(s) are shaped and positioned relative to the axis of movement 80 of the substrate 8 passing underneath, so that the section of substrate that passes underneath the thick end 64 of the wedge shaped opening of the outlet as the substrate is moved linearly along the axis of movement 80 has a greater residence time underneath the opening of the plasma head outlet than at the thin end, 65. This is because the thicker end of the wedge extends for a greater distance over the substrate than the thinner end of the wedge as the plasma head and substrate are being linearly displaced relative to each other. This is also the case for the embodiment shown in figure 17 however, in this embodiment, the plasma head and plasma head outlet is further shaped so that a first leading edge 66 which, in this case, lies generally transversely or across the axis of movement 80 when the substrate and/or plasma head is moving in the direction 82 is curved, whereas the trailing edge 67 is straight, (or vice versa if moving in the opposite direction 81 ). Therefore, this combination of providing a plasma head that, due to the shape of its outlet(s) (i.e. the opening of the outlet) can be positioned relative to the axis of displacement so that a first section of the substrate extends for a greater distance in the proximity of the outlet than a second section, results in a variation in residence time of the two sections of substrate beneath the plasma head outlet. As described herein, this may be due to the plasma head outlet having an opening of a particular non-linear and/or non-uniform shaped cross sectional profile.

The examples shown in figures 6, 7 and 18 are therefore able to deliver a gradient type effect across the working area of a substrate. In these embodiments, the variation or gradient of surface condition or function is delivered in a system where the substrate to be treated moves linearly under a static plasma head, however, this may be other way round, as herein described. This means that multiple surface outcomes, chemistries, topographies and/or functionalities can be produced in a single sweep or step. This is in contrast to a situation wherein a substrate may be moved in a linear direction of movement but using a plasma head having an outlet 20 with a linear elongated profile to provide only a single outcome, i.e. a consistent condition across the surface of the substrate. In addition to this, due to the fact that the present invention utilises linear movement of the substrate, this allows for the possibility of scaling the process up to an increased capacity.

As can be seen in the figures, in some embodiments, at least a portion of the underside of the plasma head that comprises the plasma outlet 20 may extend in a first plane, (and since the substrate is provided on the upper surface of the platen, so does at least a portion of the substrate). In addition to this, at least a portion of the profile of the plasma head which comprises the plasma head outlet 20 and which is facing the substrate may extend in a second plane. In this example, this second plane is substantially parallel to the first plane (see figures 14 and 16). It is, however, not absolutely essential that these planes are parallel to each other. In these embodiments, plasma head is therefore positioned relative to the platen 4 to provide a reasonably constant gap between the plasma head outlet and the platen during operation.

This is not essential, however, and in other embodiments, this gap may be changed dynamically during or between the plasma treatments in order to create variations in the surface treatment. This can be achieved using a suitable mechanism wherein a variable height adjustment feature is used as part of the assembly. This mechanism is capable of adjusting the plasma head height throughout the process. Although not shown in the figures, this mechanism may be used with any of the embodiments described herein, and the plasma head(s) used in this variable height electrode arrangement may therefore be non-linear, curved, wedge-shaped or any other shape which may achieve the treatment effect described above. This mechanism for changing the gap between the plasma head and the platen (and therefore substrate) provides for a variation in the vertical height of the plasma head (and integrated gas distribution sub assembly) in an automated fashion either prior to the process or during the process. This enhances the efficiency in the production of even more variations of characteristics and functionality on the substrate surface through the plasma process, particularly when used in combination with the linearly moving substrate and/or electrodes as described herein.

Figures 19 to 29 show different ways by which the substrate and the plasma heads can be moved linearly in relation to each other. The features of the embodiments described with reference to figures 1 to 18 may also be used in conjunction with these methods. In some embodiments, the different shaped plasma head outlets 20 may also be used together with any of these methods or systems.

As described above, the platen and substrate and the plasma head are positioned relative to each other, as described above, to provide a gap or space there between.

The features of the substrate are better seen in figure 22 and it may further be described as having a first surface 9 that is to be plasma treated, which faces the plasma head outlet and a second, opposite, surface 100 that is facing the platen 4, on which it is positioned. Since, in the examples described herein, the gas distributor 15 is provided at/within the plasma head, it effectively provides gas between the upper surface 9 of the substrate 14 and plasma head outlet 20. It is therefore the upper surface 9 of the substrate 14 that is facing the plasma head outlet 20 that is treated with the plasma. Figure 19 shows a side view of an embodiment of the invention wherein the platen and the substrate provided thereon move in synergy, whilst the plasma head(s) 1 1a, 1 1 b having a plasma head outlet(s) with non-linear profiles(s) moves at a rate different to this. In one example, the plasma head and substrate 14 provided thereon, may move in a first linear direction, 81 , at rate of 20 meters per second along the axis of movement, 80, whilst the plasma heads 1 1a, 1 1 b positioned above the substrate at least partially along the same axis of movement 80 at a rate of 40 meters per second. Of course, other speeds could be used.

Figure 20 shows a top view of an example of an embodiment wherein the plasma heads are arranged on a carousel 300 that is adapted to move the plasma heads so that they are moved in a loop from a position wherein the plasma head outlets 20 are above the platen 4 and therefore also the substrate 14 and so interfacing the platen 4 and substrate 14 (to thereby provide a gap) to a position wherein they are no longer above the platen, or the substrate 14 and so no longer interfacing the substrate 14.

As can be seen in figure 20, the plasma heads are moved via the carousel so that they are positioned, at some points in time, over the substrate and underlying platen, 4, at a first end, 40. This therefore creates a gap which is then present between the underside of the plasma head and the underlying platen 4. The substrate 41 is provided within the gap as described above. The plasma heads are then moved by the carousel so that they travel over the substrate and underlying platen 4 in the same direction 81 as the direction in which the platen 4 is moving. At some point, in time, the plasma heads may also move linearly over the substrate, as shown in the figures. Once the carousel has moved the plasma heads across the length of the substrate 14 and to/towards the second end 50 of the substrate and/or platen 4 then the carousel moves the plasma heads away from the substrate and platen 4 by moving the plasma heads transversely away from the axis of movement 80 and back into the loop before the process is repeated again. The carousel in this embodiment can therefore be described as moving in a plane that is generally parallel to the plane in which the substrate and/or platen 4 extend.

In this embodiment, by making the plasma heads mobile, the capacity of the system to produce multiple surface conditions in a more efficient way is therefore achieved. This function thereby provides the capacity to achieve variation in the treatment of the substrate without having to move the substrate during the treatment regime or alternatively to move the substrate at a velocity of choice during the process. Figure 21 shows a side view of a further embodiment of the invention which is similar in theory to that of figure 20, but where the carousel operates in a slightly different manner in that the rotation of the plasma heads around the carousel occurs vertically away from the substrate and platen 4 as opposed to laterally away from it.

In this embodiment, the carousel 300 moves the plasma heads, (and gas distributor 15 if provided therein) in a plane that extends along the axis of movement, 80, and also perpendicular to the plane of the substrate and/or platen, 4. The lateral space consumed by the assembly of figure 20 can therefore be reduced by circulating the plasma head and/or gas distribution assembly in the vertical direction away from the working area.

These embodiments therefore show that different types of carousels having different orientations and circulating in different planes can therefore be used to move the plasma heads and/or the gas distributor 15 in a loop towards and away from the working area comprising the platen 4, the plasma head(s) and the gap therebetween in which the substrate 14 is positioned, as desired.

In these embodiments, the plasma heads are again shown as being, or having plasma head outlets 20 that are, non-linear and curved, however other shapes of outlets or openings could be envisaged, as described above.

In the embodiments shown in figures 20 and 21 , the substrate and underlying platen are static whilst the carousel 300 moves the working electrode and associated gas distributor towards and away from them. In other embodiments, however, the substrate and platen 4 do not have to be constantly static. Figure 22 shows a side view of an example of an embodiment of the assembly wherein the platen, 4, is stationary, and the substrate 14 is moved intermittently and linearly in the direction 81. In this embodiment of the present invention, the plasma head(s), and/or associated gas distribution assembly may be rotated about a loop by the carousel 300 in the same way as in figures 20 or 21 , for example, whilst at least the substrate 14 is moved intermittently in the same direction, 81 , as the plasma head(s) 1 1. The substrate 14 may be moved in the linear direction 81 by different means, however, in this example, it is moved from a first reel 25, to a second reel 26. In this embodiment, the rollers 25, 26 are stopped and started, so that the linear movement of the substrate 14 in the first direction 81 is also intermittent and stops and starts accordingly, whereas the plasma heads are moved around the carousel continuously. In this embodiment, the substrate to be treated with gradient surface functionality is therefore mounted and transferred through the process in a start/ stop fashion.

Due to this, the capacity to deliver the variation in localised plasma condition can therefore be controlled solely by the movement of the plasma head and/or associated gas assembly, but the substrate can be delivered to be treated on a reel to reel format. This means that, although the substrate can be moved, the present invention is not limited to the movement (or continuous movement) of the substrate and can be delivered using such a start-stop regime. Figure 23 shows a side view of an example of an embodiment of an assembly similar to that in figure 22, except that the substrate to be treated with gradient surface functionality is mounted and transferred through the process in a continuous fashion using a form of a reel to reel mechanism. In other words, both the substrate 14 as well as the overhead plasma head assembly are moving continuously. The speeds of the plasma head and gas distributor assembly 15 may be ratioed to the speed of movement of the substrate, at least when the plasma head outlets are passing over the working area, i.e. over the substrate and underlying platen 4. Due to this, the efficiency and/or the efficacy of the process may be improved by moving the plasma head and/or gas distribution assembly 15 and the substrate 14 8, at ratioed speeds at least through the working or processing zone or area (i.e. when the working electrodes are passing over the first electrode to provide the gap there between).

In some situations, it may be necessary to use a solid platen, 4, that does not move relative the substrate 14. In such a situation, an embodiment of the present invention allows this by providing a carousel assembly 300 that comprises a plurality of individual platens 4. Figure 24 shows a side view of an example of this where the platen takes the form of many inflexible platen type elements, 4, mounted on a carousel that cycles so as to match the speed of transition of the substrate 14 underneath the plasma head. In this embodiment, the plasma heads positioned above the substrate 14 are stationary. This embodiment therefore builds on the embodiments wherein a solid platen is used and shows how the invention can be used to deliver a large capacity in a continuous process environment.

Figure 25 shows a side view of an example which is similar to that shown in figure 24, however, instead of being stationary (as in figure 24), in this example, the plasma head and platen are moved simultaneously on speed ratioed carousels. This embodiment therefore builds on that shown in figure 24 to provide an improvement in the range of outcomes or speed of processing to be delivered in a situation wherein a stationary plasma head would have limited the speed that the reel to reel assembly could effectively move the substrate through the process.

Figure 26 shows a side view of an example of an embodiment which is similar to that of figures 24 and 25 but wherein the platen 4 is flexible in nature and may be continuously cycled through the process. The flexible platen 4 can be used to deliver an appropriate effect in processing where the electrical characteristics are suitable. In this embodiment, this can be used to produce a surface on the substrate that relates to localised conditions found on the flexible ground electrode.

For example, if the flexible platen 4 has localised variations, and if the speeds of the substrate 14 and flexible platen 4 are the same, the surface outcome can also be localised on the substrate 14. Alternatively, if the relative speed of the platen 4 is significantly different to the substrate speed, the process could be used to deliver outcomes on the substrate with a very small degree of variation, as the differences produced on the substrate by small localised variations in the platen 4 condition could be averaged out by its constant relative movement.

In a situation wherein the production of a defined pattern is important, the flexible platen 4 and the substrate can be moved at the same speed. Alternatively, or additionally, it may be beneficial to move the patterned platen 4 at a ratioed speed to the substrate in order to deliver a specific patterned outcome on the surface of the substrate. Highly defined localised variations can therefore be produced in a reel to reel set up using a flexible platen 4 mechanism. Defined offsets (delivered through ratioed speed) of the underlying pattern can be used to deliver alternative (overlaid) patterns on the substrate. Figure 27 shows a top view of an example of another embodiment of the invention which may use the types of plasma heads (such as those having non-linear, curved, wedge shaped outlets etc.) as described above, or may alternatively use different types of plasma heads and plasma head outlets and/or rotating mechanisms.

In the embodiment shown in figure 27, the substrate 14 is being moving linearly along the axis of movement 80 as described above. At the same time, the plasma heads are also being moved linearly in the same direction 81 and then transversely away from the substrate surface, as in the example shown in figure 20. In this example, however, instead of the carousel moving each individual plasma head in a loop, a rotating plasma head assembly, or plurality of rotating plasma head assemblies (each assembly comprising a plurality of plasma heads) are mounted on the carousel and these are then moved around the loop, as in the example shown in figure 27, whilst the plasma head assemblies rotate.

These plasma head assemblies therefore rotate about their own individual axis of rotation as well being moved around the loop of the carousel 300. The rotation is limited in this instance to the dimensions of the elongated plasma head in order to provide the variation in residence time between the plasma head outlet and associated variation in surface characteristics. In some embodiments, the plasma heads may have outlets that may be linear, and in others they may be non-linear (i.e. the opening(s) of the outlets may be linear or non-linear).

This embodiment therefore provides a variation in the localised conditions of the plasma and the plasma residence time at specific positions on the substrate via a rotation of the plasma head and/or gas distribution assembly. As mentioned above, this system and method may be used with plasma head outlets that have a linear profile, or alternatively may be used in conjunction with the plasma heads described above which may have outlets that are curved, or non-linear, or non-uniform profiles or cross sections.

The invention may also be carried out using any of the different movement methods, speeds, ratios, variations etc as described above and is not limited to the feature of both the substrate and the plasma heads being moved along the axis of movement. For example, it may be carried out in the manner described above i.e. by moving only the substrate (and/or platen) linearly underneath the plasma head outlet(s) and keeping the plasma heads above stationary, whilst they rotate above about their own central axes. Alternatively, the substrate may be stationary whilst the plasma heads are moved linearly above, as described above. The different mechanisms of carousel described herein could also be used in conjunction with this embodiment of the invention. The different speeds, ratios, and types and variations of ground electrode, for example, may also be used in combination with this embodiment.

Figure 28 shows a side view of an example of an embodiment of the assembly of any of the previous assemblies operating in a gas capture environment, i.e. closed off at high points to capture/retain low density gases and remove heavier gases from the processing environment. This arrangement may be inverted to capture high density gases for the process.

Figure 29 shows a side view of an example of an embodiment of the assembly of any of the previous assemblies where the plasma heads are replenished

continuously or on a start/stop basis. In a further embodiment of the invention, shown in figure 23, the substrate can alternatively be delivered continuously and the speed at which the substrate moves differs from the speed at which the plasma head moves. In one embodiment, the plasma heads may move at a speed that is twice that of the substrate 14 positioned underneath. Alternative speeds may also be used.

The present invention described herein therefore provides novel and inventive ways in which the conditions comprise those required for creation and control of a plasma with a dielectric barrier discharge plasma shown as an example. In dielectric barrier discharge, the key elements are the electrodes, the characteristics of the electrical discharge created in the form of micro-streamers (or glow-like plasma under suitable conditions) and the composition of the gas that makes up the dielectric gap between the electrodes. The actual plasma conditions are largely determined by the dielectric properties which is a consequence of the nature of the gas (air or other gas) that the discharge passes through. It is typical in dielectric barrier discharge for a solid insulating material to sheath one or other or both of the electrodes. The figures do not show the sheathing barrier material, as the invention described here can also be applied in non-dielectric barrier discharge applications and as such the applications should not be limited to such an arrangement alone.

The plasma head assemblies described herein may be configured in a way so as to achieve effective masking of the discharge in specified zones of the substrate in order to achieve localised or varied treatment in such specific regions.

The preferred embodiment has the capacity to control the discharge so as to operate in various gas and gas mixture environments. This may provide the facility to produce layered treatment effects on the substrate surface indicated above. For example, a surface roughness may be induced via treatment using selected gas mixtures and discharge parameters suited to deliver an ablative treatment effect.

Likewise, chemical functionalities may be grafted to the surface in succession using selected gas/vapour/aerosol and surface liquid/gel mixtures and appropriate discharge parameters. Further ablative treatment may then be used to expose other chemistries and appropriate surface roughness. It is typical with atmospheric pressure plasma treated surfaces for ageing to affect the chemical functionality and related properties such as wettability. As such, further functions of the substrate surface character would relate to the time elapsed since processing.

As has been described above, by providing a high voltage plasma, varying the shapes and or numbers of the openings of the plasma head outlets, varying substrate transit speed and direction through the plasma region, and/or varying gas concentration in the plasma region or varying gas flow control across the plasma region, controlled and repeatable changes in surface chemistry, topography, morphology of the substrate can be provided.

The present invention is not limited to the plasma head and chamber/enclosure dimensions, gases, flow rates, flow distribution dynamics, power levels, or cycle numbers provided in the examples above and this data provides only examples of the potential surface outputs in terms of chemical concentrations and production of surface gradient effects. In addition to changing the overall chemical composition, the type and nature of surface chemical bonds involved can be controlled using the system. Determination of the subtle changes to surface properties that occur over the macro-scale, can provide useful data to predict subsequent interfacial responses.

If used with a plasma reactor chamber, this may be an enclosed chamber which can be stand alone or integrated with a given manufacturing/treatment process. A pre-treatment chamber environment may also be created to deliver gas/vapour concentrations and to control operational conditions such as humidity and temperature. Whereas, the normal operation of the process is at or near atmospheric pressure, the ambient environment can be over- or under-pressurised up to the limit of the conditions necessary for creation of the plasma discharge.

In some embodiments, the substrate or other device supporting the substrate may be clamped within a frame that interfaces with either the plasma head outlet, the dielectric layer or the platen, thereby providing for accurate location within the system and physical separation of the electrode/dielectric layer from the gas gap/discharge region. The flow conditions and content of the gas used to provide the chamber with a general background environment may be different from that of the gas used during the plasma treatment process. The plasma and/or gas flow may be monitored and controlled via feedback from electrical, spectroscopic and residual gas analysis techniques. A secondary or multi-treatment processing stage may be carried out in order to homogeneously or heterogeneously deposit and/or polymerise monomers and/or oligomers using other forms of plasma or related processing or using the above gradient technology. In some embodiments, the substrate may be arranged on a secondary material of known chemistry having elements and/or functionalities that would be useful when transferred to the substrate. Both the substrate and substrate holder may then be subjected to the plasma so as to transfer some of the chemical moieties from the secondary material to the substrate surface in the process.

As noted previously, this processing treatment typically extends nanometres into the substrate surface region with the actual extent of substrate modification and the chemical composition within this modified region/depth being gradated. The nature of this gradual change in properties into the substrate surface is a function of a number of parameters including the plasma conditions adjacent to the surface. It may also be affected by exposure to the atmosphere present after processing. Therefore, control of post-processing conditions may be necessary.

Surface chemical gradients are useful in a large range of industries and areas of research. For example, the present invention may be useful in surface

technologies such as adhesion, coating, printing, smart packaging, painting, plasma treatment, etching, deposition, MEMS, electroplating, electroless plating, optics, polishing, anti-corrosion, anti-fouling, cleaning, laser surface texturing, laser ablation, sputtering, embossing/moulding, self assembled monolayers,

electrospinning, spincoating, drug development, catalysis, fuel cell, solar cell, semiconductor, pharmaceuticals, diagnostics, and medical device manufacturing.

The invention may also be useful in the broad area of biomedical engineering and may be applied to laboratory equipment, products and supplies, biomaterials, biocompatible coatings/implants, tissue engineering, in vitro diagnostics, chemo-, immuno-, monoclonal antibody and vaccine therapies in oncology, genetics, bioinstrumentation, nanofabrication, cardiac mapping, wound healing, regenerative medicine, micro and nanoscale devices and nanoscale metrology and analysis. The substrates could be supplied to users with tray frame sets, specialised autoclavable tray frame sets, multi-well/channel substrates and various forms of multiple test devices.

It is important to note that the surface treatment process disclosed here can provide a mechanism by which advanced processes which are dependent on effects that occur in the sub-micron to nanoscale dimension can be used commercially. In this regard, the system may be well suited to alignment with products, companies and markets in the microscopy and spectroscopy fields noted previously, where the technology offering is surface specific. It should also be noted that whilst the type of atmospheric pressure plasma used in the system reported here is dielectric barrier discharge, the principle involved applies to all atmospheric processing conditions and those that operate at close to a normal atmosphere state. The terms dielectric barrier discharge and atmospheric pressure plasma are often used interchangeably and should be considered as such in this disclosure without being seen as a limiting factor in the types of plasma that can be covered and protected as part of the process.

WO 2012/107723 describes a label which is configured to produce an image that varies over time. In some embodiments, the image changes colour when it contacts one or more types of gas or vapour. In some embodiments, functional aspects of the label may be produced using plasma processing. The present invention can therefore be used to implement the technologies disclosed in this document. This allows for providing a large scale plasma process that is capable of producing time dependent labels in significant numbers and rapidly.