GB2427923A

GB2427923A - Palatography flexible circuit sheet

Info

Publication number: GB2427923A
Application number: GB0612878A
Authority: GB
Inventors: Alan Alexander Wrench
Original assignee: ARTICULATE INSTR Ltd
Current assignee: ARTICULATE INSTR Ltd
Priority date: 2005-07-01
Filing date: 2006-06-29
Publication date: 2007-01-10
Also published as: GB0513659D0; GB0612878D0

Abstract

A flexile circuit sheet 29 comprising a sensor array is mounted on an artificial palate 1 for palatometry. The flexible circuit sheet 29 comprises a connector portion 20 having a plurality of electrical contacts 34, and a sensor array portion 40 having an array of sensor contacts 44. The plurality of electrical contacts 34 is connected to the sensor contacts 44 by conductive tracks 18. The sensor array portion 40 is divided into a plurality of separate elongate lobes 38. A first end of each lobe 38 is attached to the connector portion 20 and a second end 42 of each lobe 38 has a sub-array of the sensor contacts 44 on which sensor components 46 are correspondingly mounted. The sensor components 46 may be conductive dots, or alternatively optical sensors. Two flexible sensor, sheets are mounted on a pseudopalate 1 to create a palatometer.

Description

P14184GB 2427923

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ARTIFICIAL PALATE

The present invention relates to dynamic palatography, and more particularly to the provision of a flexible circuit sheet for positioning an array of electrical sensors on an artificial palate and to artificial palates incorporating the flexible Circuit sheet.

There are a considerable number of techniques for measuring aspects of tongue position during speech. Such techniques are useful in studying the production of speech and in speech training, diagnosis of speech and swallowing disorders and speech therapy [Hardcastle et al 1991]. In particular, the provision of real-time visual feedback of tongue position can be of great value in speech training.

Known techniques for measuring aspects of tongue position include dynamic palatography, also known as electropalatography or palatometry [Hardcastle et al, 1989 Ref. 1]. Dynamic palatography includes the provision of an artificial palate having a number of electrodes sensitive to the contact with the tongue. The output of the electrodes can be processed by electronic circuits and, optionally, a computer to give a display, in real time, representing the tongue contact with the artificial palate.

Pressure sensors have also been used as alternative means for detecting contact between the tongue and the palate.

P14184GB Consequently, dynamic palatography provides feedback for obstruent, lateral and high front vowel articulations.

A further known technique for studying aspects of tongue position is glossometry, also called optopalatography, and includes the use of an artificial palate in which are located photo emitters and photoreceivers. Each emitter/receiver pair acts as a distance sensor unit.

The units measure tongue position by shining light onto the tongue and using the photoreceivers to detect reflected light. The further the tongue is from the artificial palate the lower is the detected level of reflected light.

Optopalatography can therefore provide useful information about the tongue position even when the tongue is not in contact with the artificial palate.

Both electropalatography and optopalatography share in common the need for an artificial palate with embedded sensors and connection to a measurement or display system.

This artificial palate, also known as a pseudopalate, must be formed to fit each individual wearer. Typically a palate for use in electropalatography is constructed using 1.4mm silver contacts connected to fine enamelled copper wire embedded in an acrylic resin formed on a cast of the prospective wearers palate as described in Hardcastle et al P14184GB (Ref 1, Figure 1 (a)). Alternatively, contacts have been embedded in a plastic, vacuum formed to the shape of the cast. The production of such palates is time consuming and Costly.

Since the 1980's several attempts have been made to reduce the time and cost of making artificial palates by the use of flexible circuits. Figures 1 (b - d) illustrate the

prior art in this area.

These flexible circuits have been designed in a variety of shapes but have in common a matrix of electrodes in fixed relation to each other with cutouts to permit the circuit to be folded to fit the palatal arch.

The original flexible palate design shown in figure 1 (b) is disclosed in GB 2052995A (Rion Co Ltd, Japan) . In 1989 Hardcastle et al (Ref 1) published a design (figure 1 (c)) with 2 extra features: a "T-shape cutout to allow more flexibility and the extension of the flexible circuit to form leads continuing out of the mouth from the rear of the palate. In 2000 Fletcher et al filed patent applications including two palate designs, EP 1320850 and WO 02/39881.

One design (figure 1 (d)) was similar to the Hardcastle design with leads extending from the rear of the palate.

It differed slightly in that the part of the circuit I) P14184GB containing the contacts was divided into 3 connected lobes providing a folding means to fit the circuit to the palatal shape. A second design retained the three lobed structure but the leads extended from the centre front of the palate.

This arrangement leads to contact positions which are fixed relative to each other on the circuit but vary in position relative to anatomical landmarks.

These designs have a number of limitations. First, they do not mould well to small, malformed or high arched palates.

Second, the number of electrodes is different from person to person as the circuit is trimmed to fit, making comparison difficult. Third, there is limited adjustability in the placement of the electrodes. Fourth, there occur blind spots on the palatal surface where contacts cannot be placed due to the presence of cutouts and tracks. Fifth, the integrated leads are limited in their reach. Sixth, there is no safety approval for flexible circuits materials to be exposed within the oral cavity and no means is provided for easily exposing the electrical contacts once the circuits are embedded in an approved dental material. Seventh, an additional connector part and/or connecting wires must be fitted. Eighth, the monolithic structure of all of previous circuits does not allow the artificial palate, once formed, to be reformed to fit a differently shaped palate. Ninth, a significant P14184GB amount of time is required to solder wires or connectors to the flexible circuits.

Ref 1. Hardcastle, W.J., Jones, W., Knight, C.,Trudgeon, A. and Calder, G. (1989) New developments in electropalatography: a state-of-the-art report. Clinical Linguistics and Phonetics, 3, 1-38.

It is the object of the invention to provide flexible circuits for use in artificial palates which avoid or reduce at least some of the aforementioned disadvantages.

It is a further object of the invention to provide artificial palates containing the flexible circuits of the invention.

The present invention provides a flexible circuit sheet suitable for use in providing an array of electrical sensor components across the surface of an artificial palate, said flexible circuit sheet having a connector portion and a sensor component array portion; wherein the connector portion has a plurality of electrical contacts which are interconnected by conductive tracks of the flexible circuit sheet to an array of sensor contacts on the sensor component array portion, and the sensor component array portion is divided into a plurality of separate elongate P14184GB lobes, each lobe being attached at one end portion to the connector portion and having at its other end portion, a sub-array of sensor contacts for coupling to respective sensor components thereon, whereby in use of the flexible circuit sheet, sub-arrays of sensor components, each mounted on a corresponding sub-array of sensor contacts, can be independently mounted on an artificial palate so as to form an array of sensor components with a desired spatial relationship between each subarray of sensor components, and with the connector portion remote from said palate so as to be disposable outside the mouth of a wearer of the artificial palate, for connection to data signal processing and/or display apparatus.

For typical palatometry or optopalatography applications, an artificial palate may have an array with from 6 to 120 sensors. The number of sensor contacts required for a given sensor array will depend on the nature of the sensors employed. For example, where the sensor components are contact electrodes, used to detect tongue contact with the artificial palate, only one sensor contact is required per contact electrode. Two or more sensor contacts are required per sensor component when the sensor components are photometers or photoreceivers, such as used for optopalatography. Preferably each lobe has a sub array of 3-20% of the contacts required for the sensor array. More P14184GB preferably each lobe has from 4-10% of the contacts. Most preferably from 5-7% of the contacts.

Where only a single contact per sensor component is required each lobe may have 3-10 contacts, preferably 4-8 contacts.

By using a number of lobes, each with a sub-array of a relatively small proportion of the total sensor components employed in the artificial palate, the flexible circuit allows a high degree of freedom in placement of sensors without the intensive labour requirement of palates where each sensor is individually placed.

Preferably each sub-array of sensor contacts is formed and arranged so as to place sensor components in a linear sub array. Most preferably each sub-array of sensor contacts is formed and arranged so as to place sensor components in a rectilinear sub-array. Where sensor components can be mounted in a linear fashion on the elongate lobes of the flexible circuit sheet the elongate lobes can be linear in form i.e. substantially one dimensional. This has the benefit that one dimensional elongate lobes can conform readily and closely to even complex surface5 of the anatomy of an artificial palate more easily than a two dimensional lobe surface.

S S

P14184GB The linear elongate lobes and their rectilinear sub-arrays of sensor components can be mounted on an artificial palate in any desired fashion. Generally they are arranged to run across the surface of an artificial palate in a spaced apart parallel fashion. This can be either from side to side (left to right) of an artificial palate or from front to back (lips to throat) Desirably the spacing between components on an artificial palate varies from one region of the palate to another.

For example an increased number and/or density of components, such as contact electrodes for the tongue, may be desired towards the front of an artificial palate where complex tongue movements are to be detected. Variable spacing between components is achieved by varying the spacing (pitch) between sensor contacts on a given lobe.

For example where the sensor components are contact electrodes each requiring only one sensor contact on the lobe ends, the pitch between contacts typically varies from 2-12mm with the closest spacing being used on lobes that are placed near the front of the artificial palate.

Preferably the flexible circuit comprises conductive tracks placed on a layer of flexible insulating material. For example the conductive tracks may be of copper. Desirably a a P14184GB the exposed surface of the conductive tracks is coated with an insulator such as a varnish or enamel, to prevent cross circuiting caused by contact of a wearer of an artificial palate with conductive tracks.

Most preferably the flexible circuit comprises conductive tracks embedded between two layers of flexible insulating material. This avoids the need to protect exposed conductive tracks from unwanted contact. Suitable flexible circuits, insulated on both sides of the conductive tracks, are well known in the manufacture of electronic devices.

For example the flexible circuit may consist of copper contacts and conductive tracks bonded between two layers of flexible polyimide material. The flexible polyirnide material may be of Kapton polyimide film manufactured by the DuPont company for example. Other suitable flexible insulating materials can be used.

Preferably the flexible circuit is less than 1mm in thickness. Most preferably the flexible circuit is less than 0.3mm in thickness. A thin circuit allows a thin artificial palate to be constructed which in use minimises discomfort to a wearer and makes speech movements more natural.

SI

P14184GB Preferably the electrical contacts of the connector portion are formed and arranged to constitute a plug connector.

Preferably the electrical contacts of the connector portion are plated with an inert conductive metal such as gold or silver. Most preferably they are plated with SterlingTM silver using a standard industry immersion process. The plug connector can then be used for interconnecting with F data signal processing and/or display apparatus, conveniently a computer. A plug connector which fits into a corresponding socket connected to the data processing apparatus by a connector lead, for example, is particularly convenient. Alternatively the contacts of the connector portion may be connected to the data processing apparatus by other means, such as by soldered connections to a connector cable.

Preferably the sensor contacts are plated with an inert conductive metal such as gold or silver. Most preferably they are plated with SterlingTM silver using a standard industry immersion process. The sensors mounted on the sensor contacts may be for example, conductive dots or pimples. These act as contact electrodes, used to detect tongue contact with the artificial palate. Preferably the conductive dots are of about 0.5 to 2mm in diameter and from 0.2 to 1.5mm in height. More preferably they are from

S

P14184GB about 0.5 to 1.6mm in diameter and from 0.2 to 1mm in height.

Other sensors may be mounted on the flexible circuit, depending on the palatography technique being employed.

For optopalatography, photoernitters such as light emitting diodes (LEDs) can be used in conlunction with photoreceivers such as photovoltaic cells. Such an arrangement may be used to detect tongue position in relation to the palate by reflectance measurement.

In use, in addition to allowing independent mounting of sub-arrays of sensor components on an artificial palate, the separate elongate lobes of the sensor component array portion provide other benefits. The portions of the lobes between the sub-array of sensor contacts and the attachment to the connector portion can be gathered or bunched together so that they exit the mouth of a wearer of an artificial palate in one or more bundles, rather than separately. This minimises the physical interference of the circuit with the speech forming movements of a wearer's mouth and lips.

Preferably the separate elongate lobes are at least 10cm in length. This allows the lobes to be independently mounted on an artificial palate with sufficient length remaining to U. P14184GB ensure that the lobes attach to the connector portion outside the mouth of a wearer. More preferably the elongate lobes are at least 20cm in length.

To facilitate connection to signal data processing equipment the total length of the flexible circuit from sensor contacts to connector portion contacts is preferably at least 30cm, more preferably at least 50cm.

It will be understood that the shape of the elongate lobes is generally designed to facilitate placement of the sensor contacts in a desired array configuration on an artificial palate whilst permitting the lobes to exit from the mouth of a wearer in a convenient fashion.

For example, the lobes may be shaped to exit directly from the centre front of the mouth or from one or both sides of the mouth. Preferably the lobes are shaped to exit from both sides of the mouth, so as to avoid interference with the tongue tip of a wearer. This can be achieved by shaping the lobes so that they leave the surface of the artificial palate, to which they are attached, at either side on the molar portion of the dentition. Alternatively the lobes may be shaped to follow a path from the back of the palate round between the molars and the cheeks of a wearer, before exiting the mouth.

P14184GB According to another aspect of the invention there is provided an artificial palate comprising: a base layer formed to a template which approximates the shape of the wearer's upper dentition and hard palate, and at least one flexible circuit sheet, said at least one flexible circuit sheet having a connector portion and a sensor component array portion, wherein the connector portion has a plurality of electrical contacts which are interconnected by conductive tracks of the flexible circuit sheet to an array of sensor contacts on the sensor component array portion, and the sensor component array portion is divided into a plurality of separate elongate lobes, each lobe being attached at one end portion to the connector portion and having at its other end portion, a sub-array of sensor contacts coupled to respective sensor components thereon, said sub-arrays of sensor components being independently mounted on the base layer so as to form an array of sensor components with a desired spatial relationship between the sensor components of the subarrays, and with the connector portion remote from said palate so as to be disposable outside the mouth of a wearer of the artificial palate, for connection to data signal processing and/or display apparatus.

P14184GB Preferably the lobes of the sensor component array portion are attached to the base layer using an adhesive. A cyanoacrylate adhesive may be used for example. Preferably the sensors mounted on the sensor contacts are conductive dots or pimples. The conductive dots or pimples may, for example, be of a silver/epoxy composition. These conductive dots act as contact electrodes for the tongue in electropalatography. Alternatively the sensor components may be photoemitters and photoreceivers for use in optopalatography.

Preferably the base layer is of a thermoplastic material.

Suitable materials for forming art artificial palate are well known. Acrylate polymers can be used for example and may be formed on a cast made from the mouth of the intended wearer of the artificial palate, to provide a good fit in use. Alternatively the base layer may be of a thermoplastic material with a low melting point such as for example an ethylene vinyl acetate (EVA) copolymer, which may be combined with a wax such as paraffin wax, to provide optimal properties. Suitable EVA copolymers include Elvax EVA copolymers from Dupont which can be formulated to have a softening point between human body temperature and 100 C.

An artificial palate having a base layer of suitably low melting thermoplastic polymer composition can be made in a P14184GB variety of sizes. For a given wearer, a suitable size is chosen, which is then heated to soften it. The wearer then inserts the artificial palate into their mouth and bites down on it to form an artificial palate that closely S conforms to their natural palate.

Preferably a second layer of material is formed over at least part of the flexible circuit sheet where it is attached to the base layer. The second layer may be formed in a number of ways. For example it may be sprayed or painted on. Alternatively it may be built up using polymer powder and hardener or, if sheet material is used, it may be vacuum formed or pressure formed from the same material as the base layer.

Most preferably the second layer covers all of the flexible circuit sheet on the base layer. This prevents contact of the flexible circuit sheet with the mouth or saliva of a wearer of the artificial palate. Sealing the flexible circuit sheet between two layers is particularly advantageous where conductive tracks of the circuit sheet are not fully encapsulated in the insulating material of the circuit sheet. It may also be necessary where the flexible circuit sheet or components attached to it are of material(s) not approved by the appropriate regulations for unprotected use inside an individuals mouth.

P14184GB Where the sensor components mounted on the flexible circuit sheet are conductive dots or pimples, which are to act as contact electrodes with the tongue, the conductive dots must protrude through the second layer. This can be achieved, for example, by forming the second layer over the whole surface of the flexible circuit sheet which is attached to the base layer and removing part of the second layer covering the conductive dots or pimples, for example, by grinding or abrading the second layer, after application thereof, so as to expose the conductive dots.

Where the sensor components are photoemitters and photoreceivers, for use in optopalatography, the second layer is conveniently of a material transparent to the wavelength of the light used, in order to avoid the need for preventing coating of these components where the coating is applied, or for partially removing the coating where it covers the components.

Where the base and optional second layer of the artificial palate are formed of relatively high melting point materials such as acrylate polymers, the artificial palate may be formed so as to have a close accurate fit to the wearer's mouth including dentition. Alternatively the artificial palate may be formed so as to only approximate P14184GB to the mouth, especially about the dentition. In such a case the artificial palate may be provided with an optional third layer, of a thermoplastic material with a softening temperature above human body temperature and below 100 C, placed above the base layer i.e. on the palatal rather then the lingual side of the artificial palate base layer. This layer may be used to fit the artificial palate more closely to the real palate and to adjust the fit of the artificial palate following changes to the shape of dentition and/or the natural palate. The use of such a third layer is particularly beneficial in providing a better grip when a wearer's teeth have gaps, or the teeth are not well developed. The thermoplastic materials employed can be softer than the rest of the artificial palate structure, to avoid damaging crowns or caps fitted to the teeth. The layer can be made from EVA copolymers or compositions of EVA and wax and is used to conform the artificial palate to a natural palate as described above when a low melting polymer is used as the base layer.

Additional layers may be used in the construction of an artificial palate of the invention. For example a layer containing a decorative image, to make the palate more attractive may be inserted between the base layer and a second layer.

P14184GB Further preferred features and advantages of the present invention will appear from the following detailed description of some embodiments illustrated with reference to the accompanying drawings in which: Figs 1 (a-e) show prior art flexible circuit devices for use in electropalatography; Figs 2 (a,b) show an embodiment of a flexible circuit of the invention; Fig 3 (a) shows in an exploded view an artificial palate of the invention fitted with flexible circuit devices of the invention and Fig 3 (b) shows the plug connector for the same embodiment.

Figure 1(a) shows a typical artificial palate 1 as used in electropalatography. A base 2 of acrylic resin which has been moulded to fit the palate of a wearer has 1.4mm contacts 4, made of silver, distributed across its surface.

The artificial palate 1 is held in place by wires 6 fitting around the teeth 8 of a wearer. The contacts 4 are each individually connected by enamelled wires 10 to the rest of the electropalatography equipment (not shown). The wires 10, are embedded in the acrylic resin base 2 and in this example are then led out of the mouth of a wearer by passing round the teeth 8 in collected bundles 12 to exit at either side of the mouth.

P14184GB Figure 1(b) shows a prior art (Rion) flexible circuit 14 with cut out portions 16 to permit folding to approximate to the palatal arch. Contacts 4 connect via conductive tracks 18 to a connector portion 20 at the rear of the flexible circuit.

Figure 1(c) shows a development of the flexible circuit due to Hardcastle et al of Figure 1(b) with a T-shape' cut out 22 to allow more flexible folding of the circuit and extensions 24 of the circuit which carry the conductive tracks (not shown) outside the mouth of a wearer to connect with the rest of the apparatus.

Figures 1(d) and 1(e) show further prior art designs where the flexible circuit 14 is divided into lobes 26 which are joined by an interconnection portion 28.

In use the lobes 26 are folded to approximate to the curvature of an artificial palate to which the flexible circuit 14 is fitted. In both designs conductive tracks 18 of the flexible circuit sheet lead to connector portions 20 which are, in use, external to the mouth of a wearer.

Figure 2(a) shows a flexible circuit 29 of the invention, with some important details shown in magnification in Fig 2 (b) . A flexible circuit sheet 14 has copper conductive P14184GB tracks 18 bonded between two insulating layers of polyimide film 30. The connector portion 20 is an elongate strip 31 of the flexible circuit sheet 14 with conductive tracks 18 running in parallel and then turning at one end 32 through 90 degrees to terminate in an array of parallel contacts (terminals) 34. The terminals 34 are configured to fit into a standard edge connecting socket (not shown) and are laid bare by the absence of one of the polyimide film sheets at the end 32 of the connector portion 20. At the other end 36 of the connector portion 30, distal from the terminals 34, the conductive tracks 18 turn through 180 degrees 37 where the strip 31 of flexible circuit sheet is divided into lobes 38 by cutting through the insulating material along lines 39 between groups of conductive tracks 18 (Fig 2(b)). The lobes 38 form the sensor component distribution portion 40. Each lobe 38 has at least three conductive tracks 18 in this example. The lobes 38 are about 2mm wide and are rectilinear from the end of the connector portion until near their ends 42. Most of the lobe ends 42 have a bend 43 of an angle of 900 or more.

Each lobe 38 has sensor component contacts 44 one at each terminus of a conductive track 18. In this example the sensor component contacts have mounted upon them conductive dots 46 of silver/epoxy composition.

P14184GB The use of the device 29 in distributing sensor components (in this example conductive dots 46) across an artificial palate is described with reference to figure 3.

The total length of the device shown, following the conductive tracks 18 from the terminals 30 to the component contacts 44 is of the order of 45cm when it is fully stretched out. This provides sufficient length for the circuit, when attached to an artificial palate, to be plugged, via the terminals of the connector portion, to the rest of the electropalatography equipment. By manufacturing the circuit with a 180 degree turn 37 the width of flexible sheeting employed in making devices need only be of the order of 25cm. To avoid tearing of the polyimide material at the point where it is divided into lobes 38, small holes 48 are punched in the polyimide layers 30. In use stress on this portion of the circuit can be further reduced by folding the circuit over and gluing together the folds, near the turn 37.

Figure 3(a) shows, in exploded view, an artificial palate 1 of the invention comprising three layers and two of the flexible circuit devices 14 of the invention. The two flexible circuit devices 14 are generally of the form shown in Figure 2 but one 48 is shaped for left hand, the other for right hand fitting.

P14184GB The base 2 of the artificial palate 1 is of a moulded acrylic sheet and includes a portion 52 which in use covers the dentitjon of a wearer. The lobe ends 42 of both the left 48 and right 50 hand circuits 14 are fixed transversely across the corresponding left and right halves of the artificial palate 1 to distribute their sensor component contents 44 in a spaced apart array. As in Figure 2 the sensor components attached to the component contacts are conductive dots 46 in this example. The lobe ends 42 then cross the dentition portion 52 at each side of the base where they bend 43 towards the front 54 of the palate 1. An exception to this arrangement is a lobe 56 that does not have a bend 43 where the contacts are laid front to back on the dentition portion 52. The lobes 38 from the left 48 and right 50 flexible circuit devices 14 are then gathered together by being encased in polymer tubing 58 at the point where each exits the mouth of a wearer to the left and right of the front dentition respectively. The lobes 38 of each circuit 48, 50 are then joined to a connector portion 20 (Fig 3(b)) which terminates in contacts (terminals) 34.

The terminals 34 of the connector portion are formed into a connector plug 60 by fixing them to either side of a piece of insulating board 62. In use the connector plug inserts P14184GB into an appropriate socket in therest of the electropalatography equipment (not shown).

A second layer 64 of acrylate sheet, moulded to conform to the base 2 is bonded, in the assembled artificial palate, to the base 2 to encase and seal from contact with the wearer, the flexible circuits 48, 50. The conductive dots 46 are then exposed by abrading or cutting away the second layer 64 at the location of each dot 46 or by generally abrading the second layer 64 across its entire surface to expose the conductive dots 64.

In this example a third layer 68 of an ethyl vinyl acetate (EVA) co-polymer is provided on top of the base (i.e. on the palatal rather than the lingual side.) The third layer 68 is provided to cover the dentition portion 52 of the base 2 and may be used to provide a close fit of the artificial palate 1 to the dentition of a wearer as follows. After assembly the artificial palate is heated to soften the third layer 68 which is then inserted into a wearers mouth so that the EVA co-polymer of the third layer 68 deforms to conform to the wearers dentition when the wearer bites on it.

Claims

P14184GB CLAIMS

1. A flexible circuit sheet suitable for use in providing an array of electrical sensor components across the surface of an artificial palate, said flexible circuit sheet having a connector portion and a sensor component array portion; wherein the connector portion has a plurality of electrical contacts which are interconnected by conductive tracks of the flexible circuit sheet to an array of sensor contacts on the sensor component array portion, and the sensor component array portion is divided into a plurality of separate elongate lobes, each lobe being attached at one end portion to the connector portion and having at its other end portion, a sub-array of sensor contacts for coupling to respective sensor components thereon, whereby in use of the flexible circuit sheet, sub-arrays of sensor components, each mounted on a corresponding sub-array of sensor contacts, can be independently mounted on an artificial palate so as to form an array of sensor components with a desired spatial relationship between each sub-array of sensor components, and with the connector portion remote from said palate so as to be disposable outside the mouth of a wearer of the artificial palate, for connection to data signal processing and/or display apparatus.

P14184GB

2. A flexible circuit sheet according to claim 1 wherein each lobe has a sub array of from 3-20% of the contacts required for the sensor array.

3. A flexible circuit sheet according to claim 1 wherein each lobe has from 4-10% of the contacts required for the sensor array.

4. A flexible circuit sheet according to claim 1 wherein each lobe has from 5-7% of the contacts required for the sensor array.

5. A flexible circuit sheet according to claim 1 wherein, each elongate lobe has from 3 to 10 sensor contacts.

6. A flexible circuit sheet according to claim 1 wherein each elongate lobe has from 4 to 8 sensor contacts.

7. A flexible circuit sheet according to any preceding claim wherein each sub-array of sensor contacts is formed and arranged so as to place sensor components in a linear sub array.

8. A flexible circuit sheet according to claim 7 wherein each sub-array of sensor contacts is formed and arranged so as to place sensor components in a rectilinear sub-array.

P14184GB

9. A flexible circuit sheet according to claim 7 or claim 8 wherein the elongate lobes are linear in form.

10. A flexible circuit sheet according to any preceding claim wherein the pitch between sensor contacts on each elongate lobe is from 2 to 12mm.

11. A flexible circuit sheet according to any preceding claim wherein the conductive tracks are placed on a layer of flexible insulating material.

12. A flexible circuit sheet according to claim 11 wherein the conductive tracks are copper.

13. A flexible circuit sheet according to claim 11 or claim 12 wherein the exposed surface of the conductive tracks is coated with an insulator.

14. A flexible circuit sheet according to any one of claims 1 to 10 wherein the conductive tracks are embedded between two layers of flexible insulating material.

15. A flexible circuit sheet according to claim 14 wherein the electrical contacts, sensor contacts and conductive tracks are of copper and the conductive tracks are bonded between two layers of flexible polyimide material.

P14184GB

16. A flexible circuit sheet according to any preceding claim wherein the sheet is less than 1mm in thickness.

17. A flexible circuit sheet according to any one of claims 1 to 15 wherein the sheet is less than 0.3mm in thickness.

18. A flexible circuit sheet according to any preceding claim wherein the electrical contacts of the connector portion are formed and arranged to constitute a plug connector.

19. A flexible circuit sheet according to any preceding claim wherein the electrical contacts of the connector portion are plated with an inert conductive metal.

20. A flexible circuit sheet according to claim 19 wherein the electrical contacts of the connector portion are plated with sterling silver.

21. A flexible circuit sheet according to any preceding claim wherein the sensor contacts are plated with an inert conductive metal.

P14184GB

22. A flexible circuit sheet according to claim 21 wherein the sensor contacts are plated with sterling silver.

23. A flexible circuit sheet according to any preceding claim wherein the separate elongate lobes are at least 10cm in length.

24. A flexible circuit sheet according to any preceding claim wherein the elongate lobes are at least 20cm in length.

25. A flexible circuit sheet according to any preceding claim wherein the total length of the flexible circuit from sensor contacts to connector portion contacts is at least 30cm.

26. A flexible circuit sheet according to any preceding claim wherein the total length of the flexible circuit from sensor contacts to connector portion contacts is at least 50cm.

27. An artificial palate comprising: a base layer formed to a template which approximates the shape of the wearer's upper dentition and hard palate, and at least one flexible circuit sheet, said at least one flexible circuit sheet having a connector portion and a sensor component array P14184GB portion, wherein the connector portion has a plurality of electrical contacts which are interconnected by conductive tracks of the flexible circuit sheet to an array of sensor contacts on the sensor component array portion, and the sensor component array portion is divided into a plurality of separate elongate lobes, each lobe being attached at one end portion to the connector portion and having at its other end portion, a sub-array of sensor contacts coupled to respective sensor components thereon, said sub-arrays of sensor components being independently mounted on the base layer so as to form an array of sensor components with a desired spatial relationship between the sensor components of the sub-arrays, and with the connector portion remote from said palate so as to be disposable outside the mouth of a wearer of the artificial palate, for connection to data signal processing and/or display apparatus.

28. An artificial palate according to claim 27 wherein the elongate lobes of the sensor component array portion are attached to the base layer using an adhesive.

29. An artificial palate according to claim 27 or claim 28 wherein the sensor components are conductive dots or pimples.

P14184GB

30. An artificial palate according to claim 29 wherein the conductive dots or pimples are of about 0.5 to 2mm in diameter and from 0.2 to 1.5mm in height.

31. An artificial palate according to claim 29 wherein the conductive dots or pimples are of about 0.5 to 1.6mm in diameter and from 0.2 to 1mm in height.

32. An artificial palate according to anyone of claims 29 to 31 wherein the conductive dots or pimples are of a silver/epoxy composition.

33. An artificial palate according to claim 27 or claim 28 wherein the sensor components are photoemitters and photoreceivers for use in optopalatography.

34. An artificial palate according to any one of claims 27 to 34 wherein the base layer is of a thermoplastic material.

35. An artificial palate according to claim 34 wherein the thermoplastic material has a softening point between human body temperature and 100 C.

36. An artificial palate according to claim 34 or claim 35 wherein the base layer is an ethylene vinyl acetate P14184GB copolymer or an ethylene vinyl acetate copolymer combined with a wax.

37. An artificial palate according to any one of claims 27 to 36 further comprising a second layer of material formed over at least part of the flexible circuit sheet where it is attached to the base layer.

38. An artificial palate according to claim 37 wherein the second layer covers all of the flexible circuit sheet where it is attached to the base layer.

39. An artificial palate according to claim 37 or claim 38, when dependent on claim 33 wherein the second layer is transparent to the wavelength of light used.

40. An artificial palate according to any one of claims 27 to 34 further comprising a third layer on the palatal side of the base layer, said third layer being of a thermoplastic material with a softening temperature above human body temperature and below 100 C.

41. An artificial palate according to claim 40 wherein the third layer is an ethylene vinyl acetate copolymer or an ethylene vinyl acetate copolymer combined with a wax.

P14184GB

42. An artificial palate according to any one of claims 37 to 40 further comprising a layer containing a decorative image inserted between the second layer and the base layer.

43. A flexible circuit sheet substantially as hereinbefore described and with reference to Figures 2a, b and 3a, b of the drawings.

44. An artificial palate substantially as hereinbefore described and with reference to Figures 3a, b of the drawings.