Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
A MULTI-LAYERED SENSING APPARATUS AND METHOD OF USE
Document Type and Number:
WIPO Patent Application WO/2020/183168
Kind Code:
A1
Abstract:
A stretchable multi-layered sensing apparatus comprises a stretchable laminate structure having an array of sensors for measuring strain orthogonal to a surface of the apparatus and a first stretchable lamina structure having an array of sensors for measuring strain through the apparatus. The stretchable structures form a stack. There is also a method of monitoring a vehicle condition using a multi-layered sensing apparatus to gather data indicative of the pressure and strain across a surface of the vehicle. The multi-layered sensing apparatus comprises at a first and second stretchable laminate structure. The first stretchable laminate structure to measure stain orthogonal to the surface of the apparatus and the second stretchable laminate structure sensors to measure in-plane stain. There is a further method of collecting data related to fluid flow over an object by using the multi-layered sensing apparatus.

Inventors:
CONDE JUAN SEBASTIAN TOBON (GB)
Application Number:
PCT/GB2020/050602
Publication Date:
September 17, 2020
Filing Date:
March 11, 2020
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
HYVE DYNAMICS HOLDINGS LTD (GB)
International Classes:
G01L1/14; G01L1/20; G01L1/22; G01M5/00; H05K1/02; H05K1/16
Foreign References:
US20160033343A12016-02-04
EP3355041A12018-08-01
US20120118066A12012-05-17
US20130041235A12013-02-14
DE102016109531A12017-06-22
GB201901260A2019-01-30
Other References:
LIPOMI ET AL.: "Skin-like pressure and strain sensors based on transparent elastic films of carbon nanotubes", NATURE NANOTECHNOLOGY, vol. 6, no. 12, pages 788 - 792, XP055390039, DOI: 10.1038/nnano.2011.184
MANNSFELD ET AL.: "Highly sensitive flexible pressure sensors with microstructured rubber dielectric layers", NATURE MATERIALS, vol. 9, no. 10, pages 859 - 864, XP055548599, DOI: 10.1038/nmat2834
XU ET AL.: "stretchable batteries with self-similar serpentine interconnects and integrated wireless recharging systems", NATURE COMMUNICATION, vol. 4, pages 1543
Attorney, Agent or Firm:
NOBLE, Frederick (GB)
Download PDF:
Claims:
CLAIMS

1. A stretchable multi-layered sensing apparatus comprising:

a stretchable laminate structure having an array of sensors for measuring strain orthogonal to a surface of the apparatus;

a first stretchable lamina structure having an array of sensors for measuring in-plane strain;

wherein the stretchable laminate structure and the first stretchable lamina structure form a stack.

2. A stretchable multi-layered sensing apparatus as claimed in claim 1, in which the array of sensors of the first stretchable lamina structure comprise at least one row of strain gauges connected by stretchable electrodes; wherein the strain gauges and stretchable electrodes are located on or are embedded in a dielectric elastomeric material.

3. A stretchable multi-layered sensing apparatus as claimed in claim 2, in which the stretchable electrodes are either serpentine electrodes or formed from carbon nanotubes.

4. A stretchable multi-layered sensing apparatus as claimed in claim 2 or 3, in which the strain gauges are formed from a strain-sensitive conductive structure comprising one or more conductive filaments arranged in a pattern.

5. A stretchable multi-layered sensing apparatus as claimed in any of the preceding claims, further comprising a second stretchable lamina structure located between the stretchable laminate structure and the first stretchable lamina structure; wherein the second stretchable lamina structure has an array of sensors for measuring temperature.

6. A stretchable multi-layered sensing apparatus as claimed in claim 5, in which the array of sensors of the second stretchable lamina structure comprise at least one row of temperature sensors connected by stretchable electrodes; wherein the temperature sensors and stretchable electrodes are located on or embedded in a dielectric elastomeric material.

7. A stretchable multi-layered sensing apparatus as claimed in claim 6, in which the stretchable electrodes are either serpentine electrodes or formed from carbon nanotubes.

8. A stretchable multi-layered sensing apparatus as claimed in claim 6 or 7, in which the temperature sensors are formed from a temperature-sensitive conductive structure comprising one or more conductive filaments arranged in a pattern.

9. A stretchable multi-layered sensing apparatus as claimed in any of the preceding claims, in which the strain orthogonal to the surface of the apparatus represents pressure acting on the surface.

10. A stretchable multi-layered sensing apparatus as claimed in any of the preceding claims, in which the stretchable laminate structure is a stretchable bidirectional pressure sensing laminate structure.

11. A stretchable multi-layered sensing apparatus as claimed in claim 10, in which the stretchable bidirectional pressure sensing laminate structure comprises: a first dielectric elastomeric sheet; a second dielectric elastomeric sheet; and at least one array of pressure-sensitive sensors.

12. A stretchable multi-layered sensing apparatus as claimed in claim 11, in which the at least one array of pressure-sensitive sensors is formed by a first series of conductor lines located on or in the first dielectric elastomeric sheet, a second series of conductor lines located on or in the second dielectric elastomeric sheet, and a separation layer made from a dielectric elastomer; wherein the first series conductor lines are substantially orthogonal to the second series conductor lines, and the separation layer is bonded directly or indirectly to the first and second dielectric elastomeric sheets so that the array of pressure-sensitive sensors can register positive and negative pressure by the movement of the first and second dielectric elastomeric sheets.

13. A stretchable multi-layered sensing apparatus as claimed in claim 11, in which the separation layer is formed from a microstructure which comprises a plurality of pillars disposed between the first and second dielectric elastomeric sheets.

14. A stretchable multi-layered sensing apparatus as claimed in claims 12 or 13, in which the first and second series of conductor lines are formed from carbon nanotubes.

15. A stretchable multi-layered sensing apparatus as claimed in any of the preceding claims, in which the first stretchable lamina structure comprises an adhesive for attaching the stretchable multi-layered sensing apparatus to an object.

16. A stretchable multi-layered sensing apparatus as claimed in any of the preceding claims, in which the dielectric elastomeric material is polydimethylsiloxane.

17. A stretchable multi-layered sensing apparatus as claimed in any of the preceding claims, wherein at least one of the stretchable structures has a mean nominal thickness of approximately 0.3 mm.

18. A method of monitoring a vehicle condition comprising the steps of:

gathering data indicative of pressure and strain across a surface of a vehicle using a stretchable multi-layered sensing apparatus;

the stretchable multi-layered sensing apparatus comprises a stretchable laminate structure adapted to measure strain orthogonal to a surface of the multi layered sensing apparatus and a first stretchable lamina structure adapted to measure in-plane strain, wherein the stretchable structures form a stack; and analysing the gather data to determine the condition of the vehicle or a component of the vehicle.

19. A method of monitoring a vehicle condition as claimed in claim 18, further comprising the step of using the gathered data to predict the future condition of the vehicle or a component of the vehicle.

20. A method of monitoring a vehicle condition as claimed in either claim 18 or 19, in which the stretchable multi-layered sensing apparatus is attached to the surface of the vehicle or the surface of the vehicle component by means of an adhesive.

21. A method of monitoring a vehicle condition as claimed in any of claims 18 to

20, wherein the stretchable multi-layered sensing apparatus is connected to an integrated vehicle health management system and the integrated vehicle health management system uses the gathered data to determine the condition of the vehicle or the component of the vehicle.

22. A method of monitoring a vehicle condition as claimed in any of claims 18to

21, wherein the stretchable multi-layered sensing apparatus is a stretchable multi-layered sensing apparatus as claimed in any of claims 1 to 17.

23. A method of collecting data related to fluid flow over an object, comprising the steps of:

attaching a stretchable multi-layered sensing apparatus to an area of the object; subjecting the object to a fluid flow; and,

recording, from the stretchable multi-layered sensing apparatus, data indicative of at least pressure over the surface of the multi-layered sensing apparatus and strain over a surface of the object.

24. A method of collecting data related to fluid flow over an object as claimed in claim 23, wherein the stretchable multi-layered sensing apparatus is a stretchable multi-layered sensing apparatus as claimed in any of claims 1 to 17.

Description:
A MULTI-LAYERED SENSING APPARATUS AND METHOD OF USE

The invention relates generally to a stretchable multi-layered sensing apparatus adapted to measure a number of variables. More particularly, the invention relates to a stretchable multi-layered sensing apparatus comprising a laminate structure adapted to measure strain orthogonal to a surface of the apparatus and a first lamina structure adapted to measure in-plane strain. The invention also relates generally to a method of using a stretchable multi-layered sensing apparatus adapted to measure pressure and strain across a surface of an object. More particularly, the invention relates to a method of monitoring a vehicle condition using the stretchable multi-layered sensing apparatus. Furthermore, the invention relates to a method of collecting data related to fluid flow over an object using the stretchable multi-layered sensing apparatus.

BACKGROUND TO THE INVENTION

Flexible and/or stretchable sensors are a recent development attracting much interest within research, especially within the biomedical field. They commonly have an array of sensors which allows for readings over an area.

There are many known sensing mechanisms used to measure different variables in stretchable and flexible sensors. For example, piezoresistivity, capacitance and piezoelectricity are mechanisms which can be used to measure pressure, with capacitive sensing providing for high sensitivity, fast response and a wide dynamic range. Another sensing mechanism used is monitoring a change in resistance through a wire. This mechanism is commonly used for measuring strain and temperature.

As described by Lipomi et al in“Skin-like pressure and strain sensors based on transparent elastic films of carbon nanotubes” Nature nanotechnology 6(12) p788-792, stretchable sensors can be constructed from two electrode layers, embedded in an elastomeric material, separated by a separation layer constructed from a continuous flexible dielectric polymer. This construction allows for the measurement of a positive compressive force being applied to the electrode layers; however, it only provides low sensitivity and is unable to measure a negative compressive force being applied to the electrode layers. Developments shown by Mannsfeld et al in“Highly sensitive flexible pressure sensors with microstructured rubber dielectric layers” Nature Materials 9(10) p859-864, have determined that sensitivity can be improved by the separation layer being constructed from microstructures instead of a continuous layer, particularly when the microstructures are pyramidal microstructures. However, this improvement in sensitivity is limited to detecting a positive compressive force as the pyramidal microstructures are attached to a single electrode layer.

The material used for electrodes in stretchable electronics have varied from rigid conductors to electrolytic fluids. The use of these types of conductors have limited the field of application because of the potential for leaking, breaking or undesired variation in the electrical properties when stretched. For example. Majidi et al in US20120118066 Al describe a pressure sensor with a plurality of liquid filled micro channels being used in areas such as wearable technology. Xu et al in“stretchable batteries with self-similar serpentine interconnects and integrated wireless recharging systems” Nature Communication 4 p 1543 describes a stretchable wireless charging system using various stretchable electronics, such as serpentine conductor lines and using thin films of carbon nanotubes forming supercapacitors.

Research has also been directed towards patterns of continual conductive filaments. Certain patterns and arrangements of conductive filaments can form a component within the circuit. For example, Rogers et al in US20130041235 Al describe a skin-mounted stretchable biomedical device which includes stretchable electronic circuits in the form of serpentine curves which are used as strain gauges. Devices which use these patterns for stretchable electronic circuits can become extremely complex because of the number of patterns required to form the necessary components. The stretchable substrate may have limited space for all the required components formed by the patterns.

Traditionally, the analysis and study of fluid flows is performed using computational methods or experimental methods. The use of a model within a wind tunnel is a common experimental method. By introducing single point sensors, such as pressure taps, into an area of the model it is possible to measure a variable at that point, but it can be difficult to gain a more complete picture because of limitations on the number of locations. Furthermore, because of the size of wind tunnels, or other experimental apparatuses, the models used are limited in size. Computational methods, such as computational fluid dynamics (CFD), have gone someway to addressing the limitations of the experimental methods. However, the accuracy of the computational method is limited by the complexity of the computational model and the available computational power. Both methods are also challenged by low Reynold number conditions, as it may be difficult to observe these conditions in the experimental method or it may be problematic to solve computationally.

A further problem with both computational and experimental methods is with the environment and the data collected from it. The environmental conditions in both methods can be idealised or controlled slightly, which lead to the collected data being at best partially relevant to the real world. Morozini et al in DE102016109531 A1 discuses the use of a smart textile to measure aerodynamic pressure. The disclosed smart textile is applied to a vehicle and used to make specific adjustments to sections of the vehicle. However, the smart textile once applied cannot be moved as the lacquer hardens the textile into the desired position.

The developments in sensor technology and data analytics has made sensors more ubiquitous. It has also allowed for the development of monitoring systems which are more accurate and can determine the health of the system or component. For example, Integrated Vehicle Health Management (IVHM) systems have been developed. IVHM systems allow for the status and health of a vehicle system or part to be determined, they also allow for improved diagnostic of faults and even prediction of faults. Since the system knows the current state and predicts the future state it is possible to produce a maintenance schedule to allow optimised reliability or minimise downtime of the vehicle. However, these systems are limited by the location and types of sensors used. For example, the system may not be able to make the most accurate predictions on the status of a component because the inferences are made from a sensor directed to a different component or measuring a less suitable variable.

It is an object of the present invention to reduce or substantially obviate the aforementioned problems. STATEMENT OF INVENTION

According to a first aspect of the present invention, there is provided a stretchable multi-layered sensing apparatus comprising: a stretchable sensing laminate structure having an array of sensors for measuring strain orthogonal to a surface of the apparatus; a first stretchable sensing lamina structure having an array of sensors for measuring in-plane strain; wherein the stretchable sensing laminate structure and the first stretchable sensing lamina structure form a stack.

It is possible to measure a variety of variables within a specific area by providing a stretchable multi-layered sensing apparatus with stacked stretchable structures. Furthermore, by allowing each stretchable structure to measure a single variable it is possible to improve the resolution. This is because the array of sensors for detecting a particular variable do not have to compete for space with other sensors. The in-plane strain experienced by the first lamina structure is the equivalent to the strain over a surface the multi-layered sensing apparatus may be attached to.

The array of sensors of the first stretchable sensing lamina structure may comprise at least one row of strain gauges connected together by stretchable electrodes. The strain gauges and/or the stretchable electrodes may be located on a dielectric elastomeric material. The strain gauges and/or stretchable electrodes may be embedded in a dielectric elastomeric material. The stretchable electrodes may be either serpentine electrodes or be formed from carbon nanotubes. By providing stretchable electrodes it is possible to maintain electrical connection between the strain gauges despite any deformation to the first stretchable lamina structure. Moreover, the electrical properties of the stretchable electrodes are maintained.

The strain gauges may be formed from a strain-sensitive conductive structure. These structures allow for the structure to have a minimal thickness. Furthermore, it ensures that the lamina structure can be deformed to a greater degree without damaging the ability to sense the in-plane strain.

The strain-sensitive conductive structure may be formed from one or more conductive filaments arranged in a continuous pattern. The continuous pattern may be formed so that the resistance changes when deformed. By providing conductive filaments in a continuous pattern a minimal thickness of lamina structure is ensured. Moreover, it is possible to deform the lamina structure without damaging electrical connectivity.

The strain-sensitive conductive structures may comprise a first number of strain-sensitive conductive structures located in a first orientation and a second number of strain-sensitive conductive structures in a second orientation. Furthermore, the strain-sensitive conductive structures may be divided into sets. Each set may have a different orientation when compared to another set.

The strain-sensitive conductive structure may be made from a material with a predetermined thermal expansion coefficient. The material may be selected to minimise the apparent strain (thermal output) independent of a mechanical load. The material may have a thermal expansion coefficient which matches or is similar to the material of the surface the multi-layered apparatus will be attached to.

The pattern of the strain-sensitive conductive structure may be a low temperature-sensitive strain-sensitive pattern. Low temperature-sensitive strain- sensitive patterns have a minimal resistance change due to a change in temperature.

The stretchable multi-layered sensing apparatus may further comprise a second stretchable sensing lamina structure with an array of sensors for measuring temperature. By providing a second lamina structure it is possible to measure the temperature of the environment or an object. Alternatively, the temperature data could be used to compensate other measured variables.

The second stretchable sensing lamina structure may be located between the stretchable sensing laminate structure for measuring strain orthogonal to the surface of the apparatus and the first stretchable sensing lamina structure.

By placing the second stretchable sensing lamina structure between the other stretchable structures it is possible to maintain high sensitivity to the measured variables. The first lamina structure is in a position to be directly attached to an object to measure strain across the surface of the object. The second lamina structure is in an intermediate position which allows for a decrease or removal of strain being registered by the array of temperature sensors. The stretchable sensing laminate structure is located so that any strain orthogonal to the surface caused by an external force is directly registered.

Alternatively, the stretchable sensing laminate structure for measuring strain orthogonal to the surface of the apparatus may be located between the first and second stretchable sensing lamina structures. This arrangement improves the sensitivity of the array of temperature sensors as they would register less strain as there is an intermediate structure providing a buffer. However, it would lower the sensitivity of the stretchable sensing laminate structure.

The array of sensors for measuring temperature may comprise at least one row of temperature sensors connected together by stretchable electrodes. The temperature sensors and or stretchable electrodes may be located on a dielectric elastomeric material. The temperature sensors and/or stretchable electrodes may be embedded in a dielectric elastomeric material. The stretchable electrodes may either be serpentine electrodes or formed from carbon nanotubes. By providing stretchable electrodes it is possible to maintain electrical connection between the temperature sensors despite any deformation to the lamina structure. Moreover, the electrical properties of the stretchable electrodes are maintained.

The temperature sensors may be formed from a temperature-sensitive structure. The temperature-sensitive structure may be formed from one or more conductive filaments arranged in a continuous pattern. The continuous pattern may be formed so that the resistance changes when deformed by temperature expanding the conductor. These structures allow for a minimal thickness of lamina structure. Furthermore, it ensures that the laminate can be deformed to a greater degree without damaging the ability to sense temperature. Moreover, it is possible to deform the lamina structure without damaging electrical connectivity. The pattern of the temperature-sensitive structure may be a low strain-sensitive temperature-sensitive pattern. Low strain-sensitive temperature-sensitive patterns have a minimal resistance change due to deformation caused by strain.

The temperature-sensitive structure may be constructed from a material with minimal resistance change due to deformation.

The pattern of the strain-sensitive conductive structure may be similar to the pattern of the temperature-sensitive conductive structure.

Alternatively, the pattern of the strain-sensitive conductive structure may be different to the pattern of the temperature sensitive conductive structure.

The first stretchable sensing lamina structure may be a strain-sensitive laminate structure formed from multiple lamina structures.

The strain-sensitive laminate structure may comprise at least two stretchable sensing lamina structures for measuring in-plane strain. Each of the stretchable sensing lamina structures for measuring in-plane strain may comprise the features of the first stretchable sensing lamina structure. The strain-sensitive conductive structure located in one stretchable sensing lamina structure may have a different orientation to the strain- sensitive conductive structure located in the other stretchable sensing lamina structure. Alternatively, each lamina structure may be offset from another. Preferably, one lamina structure may measure in-plane strain in a direction orthogonal to the other lamina structure.

The second stretchable sensing lamina structure may be a temperature-sensitive laminate structure formed from multiple lamina structures.

The measurement of strain orthogonal to the surface of the apparatus may represent the deformation through compression and/or tension acting on the stretchable sensing laminate structure. The strain orthogonal to the surface may represent pressure acting on the surface of the apparatus. The stretchable sensing laminate structure may be a stretchable bidirectional pressure sensing laminate structure.

The stretchable bidirectional pressure laminate structure may comprise a first sheet made from a dielectric elastomeric material; a second sheet made from a dielectric elastomeric material; and at least one array of pressure-sensitive sensors. This structure allows for the array of sensors to be responsive to both positive and negative pressure.

The array of pressure-sensitive sensors may be formed by a first series of parallel conductor lines located on or in the first sheet, a second series of parallel conductor lines located on or in the second sheet, and a microstructure formed from a plurality of pillars made from a dielectric elastomeric material. The plurality of pillars may be disposed between the first and second sheets; wherein the first series conductor lines are substantially orthogonal to the second series conductor lines. The microstructure is an array of spaced apart repeating structures used to separate the series of electrodes. The microstructure may be bonded to both the first and second sheets so that the array of pressure-sensitive sensors can register positive and negative pressure by the movement of the first and second dielectric elastomeric sheets. Because of the high sensitivity from this construction, low Reynold conditions are no longer a challenge. Furthermore, the sensors may register both compressive and tensile forces created by positive or negative pressure.

The array of pressure-sensitive sensors may be formed by a first series of parallel conductor lines located on or in the first sheet, a second series of parallel conductor lines located on or in the second sheet, and a separation layer made from a dielectric elastomer. The separation layer is disposed between the first and second sheets. Furthermore, the separation layer may be bonded directly or indirectly to the first and second sheets. The first series of conductor lines are substantially orthogonal to the second series of conductor lines.

The separation layer may be a microstructure comprising an array of spaced apart repeating structures used to separate the first and second series of conductor lines. The separation layer may be a single structure for separating the first and second series of conductor lines.

The microstructure may be an array of spaced apart repeating structures used to separate two electrodes. The structures may be cuboid, frustro-conical or other shapes. The shapes should provide opposing faces for bonding either directly or indirectly to the first and second elastomeric sheets. The shape may preferably be cuboid.

The first and second series of conductor lines may be formed from carbon nanotubes. This type of conductive material allows for the electrical properties of the conductor lines to be maintained when the sheets are stretched or deformed. The number of conductor lines in the series, as well as the type of conductor material, may be selected based on the required specifications (resolution, sensitivity, or etc). For example, the number of conductor lines may be increased to improve the resolution. The first and second series of conductor lines may be in direct contact with the microstructure or have an intervening layer, such as another dielectric elastomeric sheet.

Each pillar may be located at a crossing point between the first elastomeric sheet’s conductor lines and the second elastomeric sheet’s conductor lines. The combination of a pillar and crossing point forms a pixel. The number of pixels determines the resolution of the sensor. Each pixel can provide a measurement, but the combination of pixels creates the array of pressure-sensitive sensors.

The stretchable laminate structure may comprise stretchable electrodes. Each of the first and second sheets may have a stretchable electrode connected to the series of conductor lines. The stretchable electrode may be located in or on its respective elastomeric sheet. Having a stretchable electrode connected to the conductor lines in the series of conductor lines allows for an electrical connection to each conductor line to be maintained despite the sensor being deformed. The stretchable electrodes may be formed from any suitable material such as copper. Each stretchable electrode may be a serpentine electrode. Serpentine electrodes can be stretched by up to 300% while maintaining their electrical properties. The first stretchable sensing lamina structure or strain-sensitive laminate structure may comprise an adhesive for attaching the stretchable multi-layered sensing apparatus to an object. The adhesive may be applied separately or be an additional layer covered by a protector. Different adhesives vary in strength and an adhesive may be selected to allow the stretchable multi-layered sensing apparatus to be removed and reused.

The dielectric elastomeric materials used throughout the multi-layered apparatus may be a polydimethylsiloxane (PDMS) polymer, or other suitable elastomeric dielectric material. This material is a stretchable dielectric polymer and may also be transparent, translucent or opaque.

At least one of the stretchable sensing structures may have a mean nominal thickness of approximately 0.3 mm.

According to a second aspect of the present invention, there is provided a method of monitoring a vehicle condition comprising the steps of: gathering data indicative of pressure and strain across a surface of a vehicle using a stretchable multi layered sensing apparatus; and using the gathered data to determine the current condition of the vehicle or a component of the vehicle; wherein the stretchable multi layered sensing apparatus comprises a stretchable sensing laminate structure adapted to measure strain orthogonal to a surface of the multi-layered sensing apparatus and a first stretchable sensing lamina structure adapted to measure strain across the surface of the vehicle or component, wherein the stretchable sensing laminate structure and the first stretchable sensing lamina structure form a stack.

By using a stretchable multi-layered sensing apparatus, it is possible to measure a variety of variables within a specific area of the vehicle or vehicle component. This allows for real time monitoring and mapping of strain across a surface and pressure variation. By using this data it is possible to determine and predict the health, status, integrity and conditions of the vehicle or vehicle component. Furthermore, by allowing each stretchable structure to measure a single variable it is possible to improve the resolution. This is because the array of sensors for detecting a particular variable do not compete for space with other sensors measuring a different variable. The method of monitoring a vehicle condition may further include the step of performing analysis on the gathered data to predict the future condition of a vehicle and/or a vehicle component. By knowing the future condition of a vehicle and/or vehicle component it is possible to plan and organise maintenance schedules.

The method of monitoring a vehicle condition may further comprise the step of applying the multi-layered sensing apparatus to a surface of a vehicle or a surface of a component by means of an adhesive. The adhesive may be applied to the first stretchable sensing lamina structure. This allows for the multi-layered sensing apparatus to be moved to different portions of the vehicle or components.

The stretchable multi-layered sensing apparatus used in the second aspect of the invention may be the stretchable multi-layered sensing apparatus according to the first aspect of the present invention.

According to a third aspect of the present invention, there is provided a method of collecting data related to fluid flow over an object using a stretchable multi-layered sensing apparatus comprising a laminate structure for measuring pressure and a first stretchable lamina structure for measuring strain across the surface of the object, the method comprises the steps of attaching the stretchable multi-layered sensing apparatus to an area of the object, subjecting the object to a fluid flow, and recording data indicative of pressure over the surface of the multi-layered sensing apparatus and strain across the surface of the object.

By using a stretchable multi-layered sensing apparatus, it is possible to measure a variety of variables within a specific area. Moreover, by using an array of sensors within each of the stretchable structures it is possible to create a map of variables over an area. Traditionally, pressure taps, or point sensors only provide a single reading within an area. Furthermore, by allowing each stretchable structure to measure a single variable it is possible to improve the resolution. This is because the array of sensors for detecting a particular variable do not have to compete for space. By using an array of sensors it is possible to get detail similar to computational methods while also allowing for the accuracy of experimental methods. The method allows for the collection of data in real world conditions with actual real world objects, for example the method allows for a sensor to be attached to a vehicle being driven on public roads.

The stretchable multi-layered sensing apparatus used in the third aspect of the present invention may be the stretchable multi-layered sensing apparatus according to the first aspect of the present invention.

The method of analysing fluid flow may further comprise the step of placing the object within an experimental apparatus, such as a wind tunnel or water tank. The use of the multi-layered sensing apparatus within wind tunnels or water tanks allows for more measurements to be taken within an area and provides the accuracy of experimental data while providing detail similar to that of a computational method.

The object may be subjected to fluid flow in real-world conditions. An example of this is applying the stretchable sensing apparatus to a vehicle, or part of a vehicle, then operating the vehicle outside of an experimental apparatus (wind tunnel etc) in real-world conditions. This allows for real world data to be collected instead of data within a controlled environment.

According to a further aspect of the present invention, there is provided a stretchable multi-layered sensing apparatus comprising a plurality of stretchable sensing laminate structures; wherein each stretchable sensing laminate structure is bonded to at least another stretchable sensing laminate structure and comprises an array of sensors adapted to measure a different variable.

In all aspects of the invention, the first stretchable sensing lamina structure may be known as the bottom stretchable sensing lamina structure because it is the structure which is in contact with or attach to a surface of an object. The stretchable structure (either the laminate structure or second lamina structure) can be known as the top structure because it is furthest away from the surface of the object. BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made by way of example only to the accompanying drawings, in which:

Figure 1 shows an exploded schematic view of a first embodiment of the multi layered sensing apparatus according to the first aspect of the present invention;

Figure 2 shows an exploded schematic view of a second embodiment of the multi-layered sensing apparatus according to the first aspect of the present invention;

Figure 3 shows an array of strain-sensitive conductive structures according to the first aspect of the present invention; and

Figure 4 shows an array of temperature-sensitive conductive structures according to the first aspect of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Figure 1 shows an exploded schematic view of a stretchable multi-layered sensing apparatus 10. In the current embodiment the stretchable multi-layered sensing apparatus 10 comprises a stretchable laminate structure 12, a second stretchable lamina structure 14 and a first stretchable lamina structure 16. The stretchable structures 12, 14 & 16 form a stack. The laminate structure 12 forms the surface of the apparatus. In other embodiments the stretchable multi-layered sensing apparatus 10 only needs to have stretchable sensing laminate structure 12 and the first stretchable sensing lamina structure 16.

Although not apparent from the exploded schematic view in figure 1, the first stretchable lamina structure 16 is attached to the second stretchable lamina structure 14 which is attached to the stretchable laminate structure 12. In other embodiments, the first stretchable lamina structure 16 is attached to the stretchable laminate structure 12. The stretchable laminate structure 12 has a first dielectric elastomeric sheet 121, a second dielectric elastomeric sheet 123 and a microstructure formed by a plurality of dielectric elastomeric pillars 125. Each pillar in the present embodiment is preferably a cuboid. Although not apparent from the exploded view in figure 1, two opposite faces of the cuboid pillars are bonded, either indirectly or directly, to the first dielectric elastomeric sheet 121 and the second dielectric elastomeric sheet 123.

The stretchable laminate structure 12 has an array of sensors for measuring strain orthogonal to the surface of the apparatus. The sensors are formed by a first series of parallel running conductor lines 127 located on or in the first dielectric elastomeric sheet 121, a second series of parallel running conductor lines 129 located on or in the second dielectric elastomeric sheet 123, and the plurality of dielectric elastomeric pillars 125. The first series of conductor lines 121 are orthogonal to the second series of conductor lines 123. Each pillar 125 of the microstructure is bonded to both the first and second dielectric elastomeric sheets so that the array of sensors can register strain orthogonal to the surface. The registered strain can be representative of both a positive and negative pressure external to the apparatus, particularly the pressure along the surface of the apparatus or the first dielectric elastomeric sheet 121.

Each pillar 125 is located at a crossing point between conductor lines of the first series 127 and second series of conductor lines 129. There is no point at which the conductor lines of the first and second series are in physical contact, however there is a point at which they cross when the apparatus is viewed from above or below. The combination of pillar and conductor line crossing point form the sensor. In the current embodiment the sensing mechanism used for the array of sensors in the laminate structure 12 is a capacitive mechanism. An external force causes the pillar to deform either by compressor or extension. This deformation causes a change in capacitance as the distance between the conductor lines change. The capacitance of each pillar and conductor line crossing point is calculated by equation 1.

Where the capacitance (C) is inversely proportional to the distance between the orthogonal conductor lines ( L ), and directly proportional to the area formed by conductor lines at the crossing point (A), relative permittivity of the dielectric material (e G ) and the permittivity in a vacuum (e 0 ). By calculating the change in capacitance, it is possible to calculate the location and intensity of the force.

The first series and second series of conductor lines 127, 129 are schematically represented by solid lines in figure 1, this is not indicative of the structure or type of material. In preferable embodiments the conductor lines may be formed from carbon nanotubes, however any conductive material which is known to the skilled person as being flexible and deformable while maintaining its electrical properties would be suitable.

The first dielectric elastomeric sheet 121 and second dielectric elastomeric sheet 123 of the laminate structure 12 may each include a stretchable electrode in the form of a serpentine electrode 131 made from copper. Each serpentine electrode 131 is connected to the ends of all the conductor lines in the series on its respective sheet. Furthermore, the serpentine electrode of the first elastomeric sheet is perpendicular to the serpentine electrode of the second elastomeric sheet.

The second lamina structure 14 comprises a dielectric elastomeric sheet 141 with an array of sensors 143 for measuring temperature. The array of sensors 143 are located on the dielectric elastomeric sheet 141. In other embodiments, the sensors may be embedded within the dielectric elastomeric sheet 143 or another sheet. Additionally, the sensors may be encapsulated by an additional layer of dielectric elastomeric material.

The array of sensors for measuring temperature 143 are arranged in five rows of three sensors. In other embodiments the number of sensors within a row and the number of rows may vary. Each sensor 143 has an electrical property which varies based on temperature. For example, a thermistor or at least one conductive filament arranged in a known pattern in which the resistance changes based on a temperature. See figure 4 for an example of a conductive filament pattern.

Each sensor 143 is represented schematically as blocks; however, this is not indicative of the type of sensor. For example, a sensor may be constructed from a temperature-sensitive conductive filament pattern. The electrical resistance of the pattern changes based on deformation of the pattern due to temperature. See figure 4 for an example of a conductive filament pattern.

Each sensor in the row is connected to another in the same row by stretchable electrodes 145. The stretchable electrodes 145 are represented schematically by solid lines in figure 1, this is not indicative of the structure or type of material. The stretchable electrodes 145 may be any construction which allow for the electrical properties to be maintained while being flexible and/or deformable. For example, they may be serpentine electrodes or electrodes formed from carbon nanotubes as shown in figures 3 and 4.

The first lamina structure 16 comprises a dielectric elastomeric sheet 161 with an array of sensors 163 for measuring strain. The array of sensors 163 are located on the dielectric elastomeric sheet 161. In other embodiments, the sensors may be embedded within the dielectric elastomeric sheet 161 or another sheet. The sensors may also be encapsulated by an additional layer of dielectric elastomeric material. The first lamina structure 16 has an adhesive layer 167 which allows the sensor 10 to be attached to an object.

The array of sensors for measuring strain 163 are arranged in five rows of three sensors. In other embodiments the number of sensors within a row and the number of rows may vary. Each sensor is represented schematically as blocks; however, this is not indicative of the type of sensor. For example, a sensor may be constructed from a strain- sensitive conductive filament pattern. The electrical resistance of the pattern changes based on deformation of the pattern. See figure 3 for an example of a conductive filament pattern.

Each sensor in the row is connected to another in the same row by stretchable electrodes 165. The stretchable electrodes 165 are represented schematically by solid lines in figure 1, this is not indicative of the structure or material. The stretchable electrodes 165 may be any construction which allow for the electrical properties to be maintained while being flexible and/or deformable. For example, they may be serpentine electrodes or electrodes formed from carbon nanotubes as shown in figures 3 and 4. Figure 2 shows a second embodiment of the stretchable multi-layered sensing apparatus 20. The stretchable multi-layered sensing apparatus 20 comprises a stretchable laminate structure 22, a second stretchable lamina structure 24 and a first stretchable lamina structure 26.

The stretchable laminate structure 22 has a first dielectric elastomeric sheet 221, a second dielectric elastomeric sheet 223 and a separation layer 225 made from dielectric elastomer. The stretchable laminate structure 22 has a first conductive layer 227 disposed between the first sheet 221 and the separation layer 225. The conductive layer 227 is made from a dielectric elastomeric material and has a first series of parallel conductor lines located in or on the layer. The stretchable laminate structure 22 has a second conductive layer 229 disposed between the second sheet 223 and the separation layer 225. The second conductive layer 229 is made from a dielectric elastomeric material and has a series of parallel conductor lines located in or on the layer. The series of conductor lines in the first conductive layer 227 are orthogonal to the series of conductor lines in the second conductive layer 229. In other embodiments, the first and second series of conductor lines may be located on or in the first and second dielectric elastomeric sheets. Furthermore, the separation layer 225 may be a microstructure formed from an array of repeating structures of the same shape.

The array of sensors in the laminate structure 22 are formed from the separation layer 225 and the crossing points between the series of conductor lines in the first conductive layer 227 and the series of conductor lines in the second conductive layer 229. In the current embodiment, the sensing mechanism works through a change in capacitance caused by a change in distance between the two electrodes at the crossing point.

The laminate structure 22 may be substantially the same or similar to the laminate structure disclosed in the applicant’s co-pending application no. 1901260.8, the disclosure of which is incorporated by reference.

The first stretchable lamina structure 24 comprises an array of temperature sensors 243. The current embodiment shows a single row of five temperature sensors connected by a conductive layer 245. The conductive layer 245 is made from a stretchable substrate, such as a dielectric elastomeric material, with a series of stretchable electrodes formed in or on the layer. The conductive layer 245 is bonded to a further layer 241 made from a dielectric elastomer.

Although not apparent from the schematic view shown in figure 2, the second stretchable lamina structure 24 is bonded to the laminate structure 22. The array of sensors and/or the conductive layer 245 may be bonded directly to the second dielectric elastomeric sheet 223. In an alternative embodiment, there may be an additional layer of dielectric elastomeric material which is bonded to the conductive layer 245 and the second dielectric elastomeric sheet 223. This additional layer may encapsulate the array of sensors.

The first stretchable lamina structure 26 comprises an array of strain-sensitive sensors 263. The current embodiment shows a single row of five strain gauges connected by a conductive layer 265. The conductive layer 265 is made from a stretchable substrate, such as a dielectric elastomeric material, with a series of stretchable electrodes formed in or on the layer. The conductive layer 265 is bonded to a further layer 261 made from a dielectric elastomer.

Although not apparent from the schematic view shown in figure 2, the first stretchable lamina structure 26 is bonded to the second lamina structure 24. The array of sensors and/or the conductive layer 265 may be bonded directly to layer 241. In an alternative embodiment, there may be an additional layer of dielectric elastomeric material which is bonded to the conductive layer 265 and layer 241. This additional layer may encapsulate the array of sensors.

In figure 2 each sensor of the array of strain gauges 263 and array of temperature sensors 243 are represented schematically as blocks; however, this is not indicative of the type of sensor. For example, each sensor of the array of strain gauges 263 and the array of temperature sensors 243 may be formed from a conductive filament pattern.

Figure 3 shows an array of sensors 30 from the first lamina structure. The array of sensors is constructed from a plurality of sensor rows. Each row comprises a series of sensors 32 connected by stretchable electrodes 34. The sensors shown are strain- sensitives structures constructed from a conductive filament arranged in a known pattern. A conductive filament pattern will use a property of electrical conductance and its dependence on the conductor’s geometry to determine strain. When the conductive filament is deformed or stretched, within limits of the material’s elasticity, it becomes narrower and longer resulting in an increase in electrical resistance. Conversely, when compressed the conductive filament will broaden and shorten, decreasing its electrical resistance. The electrical resistance is indicative of the strain. A typical pattern for a strain-sensitive conductive filament is a series of parallel conductor runs. Each parallel run is connected to another parallel run by an orthogonal conductor run at its end. The parallel runs are closely spaces and may vary in length. There are other known patterns which involve complex shapes and/or curved conductor runs.

The stretchable electrodes 34 are serpentine electrodes made from a conductive material such as copper. In other embodiments, the stretchable electrodes 34 can be formed from carbon nanotubes (similar to figure 4) applied to the elastomeric material in the first lamina structure. The stretchable electrodes 34 maintain their electrical properties when stretched or deformed.

Figure 4 shows an array of sensors 40 from the second lamina structure. The array of sensors is constructed from a plurality of sensor rows. Each row comprises a series of sensors 42 connected by stretchable electrodes 44. The sensors shown are temperature-sensitive structures constructed from a conductive filament arranged in a known pattern. A conductive filament pattern will use a property of electrical conductance and its dependence on the conductor’s geometry to determine temperature. When the conductive filament experiences a change in temperature the resistivity of the material will change. The change in resistivity is indicative of the change in temperature. The patterns used for temperature sensing may be similar to those used for strain gauges, however they may be different.

The stretchable electrodes 44 are formed from carbon nanotubes. In other embodiments, the stretchable electrodes 44 may be formed from serpentine electrodes (similar to figure 3). The stretchable electrodes 44 maintain their electrical properties when stretched or deformed. The second aspect of the invention is provided by a stretchable multi-layered sensing apparatus used to gather data indicative of the pressure and strain across a surface of a vehicle or component of the vehicle. The stretchable multi-layered sensing apparatus comprises a stack of stretchable structures. The stack of stretchable structures comprises a stretchable laminate structure adapted to measure strain orthogonal to the surface of the multi-layered sensing apparatus and a first stretchable lamina structure adapted to measure strain across the surface of a vehicle or component of the vehicle.

The first stretchable lamina structure is attached to the surface of a vehicle or the surface of a component part of the vehicle. As the multi-layered sensing apparatus is stretchable it can closely conform to the surface it is attached to. The vehicle is then operated in real world conditions or within a wind tunnel. During operation of the vehicle the laminate structure is used to gather data indicative of strain orthogonal to the surface of the multi-layered sensing apparatus, this strain represents the pressure over the surface. The first lamina structure is used to gather data indicative of strain across the surface of the vehicle or component of the vehicle.

The gathered data is than used to determine the condition or health of the vehicle or component of the vehicle. The gathered data can be analysed on its own or with other measured variables and/or other data to determine the condition, status, state or health of the vehicle or component of the vehicle. In the current embodiment, the gathered data is provided to an integrated vehicle health management (IVHM) system which performs analysis on the data to determine the condition, status, state or health of the vehicle or vehicle component. The IVHM system determines the condition, state, status or health of a vehicle system or component. The condition, state, status and/or health can be used in a further process, for example fault diagnostics or predictions of faults. The IVHM system may also predict the future condition, status, state or health of the vehicle or component of the vehicle. In another embodiment, the IVHM system may used the current state, condition, status or health of the vehicle and the predicted state, condition, status or health of the vehicle to produce a maintenance schedule for the vehicle. Another embodiment of the second aspect of the present invention uses a stretchable multi-layered sensing apparatus according to the first aspect of the present invention.

The third aspect of the invention is provided by a stretchable multi-layered sensing apparatus attached to an object allowing for the collection of data related to fluid flow over the object. The stretchable multi-layered sensing apparatus comprises a stack of stretchable structures. The stack of stretchable structures includes a stretchable laminate structure adapted to measure pressure over the surface of the multi-layered sensing apparatus and a first stretchable lamina structure adapted to measure strain across a surface of the object.

The first stretchable lamina structure is attached to an area of the surface of the object by means of an adhesive. Because the multi-layered sensing apparatus is stretchable it can closely conform to the surface of the object. Once the stretchable multi-layered sensing apparatus has been attached to the object it is subjected to fluid flow, preferably in real world conditions or within a wind tunnel or water tank. The laminate structure is used to gather data indicative of the pressure over the objects surface. The first lamina structure is used to gather data indicative of the strain the object experiences. The gathered data is recorded and can be used either immediately in analysing fluid flow or stored for later analysis. The fluid flow over the multi-layered apparatus creates an external force which acts on the surface of the laminate structure. The external force deforms the material of the laminate structure which is used to determine the pressure over the surface. The first lamina structure undergoes deformation as a result of the surface of the object deforming.

In another embodiment, the third aspect of the present invention uses a multi layered sensing apparatus described in the first aspect of the present invention.

The embodiments described above are provided by way of example only, and various changes and modifications will be apparent to persons skilled in the art without departing from the scope of the present invention as defined by the appended claims.