Flexible pressure or strain mapping device, method of preparing same, pressure mapping system, computer implemented method of real time digitization and visualization of graphical representations, computer program, and computer readable data carrier - Patents.com

Abstract

The present invention refers to a flexible pressure or strain mapping device comprising a fibrous substrate layer (1) comprising at least one layer zone (2) impregnated with hydrogel, a first sensor electrode (3) having a portion contacting at least the lower part of said layer zone (2) impregnated with hydrogel, and a second sensor electrode (4) having a portion contacting at least the upper part of said layer zone (2) impregnated with hydrogel. Flexible pressure or strain mapping devices include hydrogels, which are flexible and have higher performance in terms of mechanical and sensing properties, given that the materials are easily tailored and therefore they can be stretchable, biocompatible and exhibit self-healing properties. Additionally, flexible pressure or strain mapping devices may be placed in the array to map the pressure distribution and provide a more accurate output in some applications.

Description

[Technical Field]

[0001] The present invention refers to a flexible pressure or strain mapping device configured to perform electrical detection of various physical stimuli, such as pressure, strain, touch, and stretch. [Background technology]

[0002] The number of sensing devices surrounding us is growing rapidly, due in part to the spread of the Internet of Things (IoT) and the adoption of wearable devices. Among the plethora of sensors, pressure sensors play an important role in several applications, from health monitoring by detecting several physiological signals, such as pulse, respiration, and other muscle movements, to robotic skin, functional prosthetic limbs, and human-machine interfaces. However, with the growth in production of wearable devices and other small electronic devices, e-waste is becoming a significant burden, highlighting the need to identify more environmentally friendly and sustainable materials. The manufacturing process is also important when creating these sensing devices, which has driven research into low-cost, simple, and scalable sensor processes, such as screen printing.

[0003] Pressure sensors typically rely on piezoresistive or capacitive transduction mechanisms to convert mechanical inputs into electrical signals. The sensitivity, hysteresis, and response and recovery times of pressure sensors are frequently improved by microstructuring some of their components, i.e., the sensing film or electrodes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Patent Application No. WO2013113122A1 to Smart Skin Technologies INC., entitled "PRESSURE MAPPING AND ORIENTATION SENSING SYSTEM," filed August 8, 2013 [Non-patent literature]

[0005] [Non-Patent Document 1] Johanna Zikulnig, Jurgen Kosel, "Flexible Printed Sensors - Overview of Fabrication Technologies," Reference Modules in Biomedical Sciences, Elsevier, 2021 Summary of the Invention [Means for solving the problem]

[0006] In a first aspect, the present invention provides a flexible pressure or strain mapping device comprising: a fibrous substrate layer (1) comprising at least one layer zone (2) impregnated with a hydrogel; at least one first sensor electrode (3) having a portion contacting at least the lower portion of the layer zone (2) impregnated with hydrogel; and at least one second sensor electrode (4) having a portion contacting at least the upper portion of the layer zone (2) impregnated with hydrogel; The hydrogel is a cellulose derivative, and cellulose derivative hydrogel refers to a flexible pressure or strain mapping device selected from the group consisting of cellulose acetate, cellulose acetate phthalate, cellulose acetate butyrate, cellulose acetate trimellitate, hydroxypropyl methylcellulose phthalate, methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, composites thereof or composites thereof with natural polymers, polyvinyl alcohol, polyelectrolyte complexes, interpenetrating polymer networks, cellulose-inorganic hybrid hydrogels, or mixtures or composites thereof.

[0007] Alternatively, in a first aspect as shown in FIG. 16, the present invention provides a flexible pressure or strain mapping device comprising: a fibrous substrate layer (1) comprising at least one layer zone (2) impregnated with a hydrogel; at least one first interdigitated electrode (19) having a portion contacting at least a portion of the layer zone (2) impregnated with hydrogel; and at least one second interdigital electrode (20) having a portion contacting at least the same portion of the hydrogel-impregnated layer zone (2) contacted by the first interdigital electrode (19), wherein the portion of the hydrogel-impregnated layer zone (2) is selected from its lower portion or its upper portion, and when multiple pairs of first interdigital electrodes (19) and second interdigital electrodes (20) are included in the flexible pressure or strain mapping device, at least one electrically insulating layer (21) separates the first interdigital electrodes (19) and second interdigital electrodes (20) from each other; The hydrogel is a cellulose derivative, and cellulose derivative hydrogel refers to a flexible pressure or strain mapping device selected from the group consisting of cellulose acetate, cellulose acetate phthalate, cellulose acetate butyrate, cellulose acetate trimellitate, hydroxypropyl methylcellulose phthalate, methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, composites thereof or composites thereof with natural polymers, polyvinyl alcohol, polyelectrolyte complexes, interpenetrating polymer networks, cellulose-inorganic hybrid hydrogels, or mixtures or composites thereof.

[0008] In a second aspect, the present invention provides a method of preparing a flexible pressure or strain mapping device as defined in the first aspect of the invention, comprising: a) depositing and impregnating a hydrogel in a fibrous substrate layer (1) to form at least one layer zone (2) impregnated with the hydrogel; b) connecting a portion of the first sensor electrode (3) to at least the lower part of said layer zone (2) impregnated with hydrogel; c) connecting a portion of a second sensor electrode (4) to at least the top of said layer zone (2) impregnated with hydrogel.

[0009] Alternatively, in a second aspect, there is provided a method of preparing a flexible pressure or strain mapping device as defined in the first aspect of the invention, comprising the steps of: a) depositing and impregnating a hydrogel in a fibrous substrate layer (1) to form at least one layer zone (2) impregnated with the hydrogel; b) connecting a portion of a first interdigitated electrode (19) to at least a portion of said layer zone (2) impregnated with hydrogel; c) connecting a portion of a second interdigital electrode (20) to at least the same portion of the layer zone (2) impregnated with hydrogel that is contacted by the first interdigital electrode (19), said portion of the layer zone (2) impregnated with hydrogel being selected from its lower portion or its upper portion; d) when multiple pairs of first interdigital electrodes (19) and second interdigital electrodes (20) are included in said flexible pressure or strain mapping device, separating the first interdigital electrodes (19) and second interdigital electrodes (20) from each other by an electrically insulating layer (21).

[0010] In a third aspect, the present invention provides a pressure mapping system comprising a pressure sensitive surface (9), said pressure sensitive surface (9) comprising a flexible pressure mapping device as defined in the first aspect of the present invention, said pressure mapping system comprising: an electronic instrumentation subsystem (11) including a data transmitting and receiving unit (15), a microcontroller (12), and a power supply; a hybrid connector (10) linking the pressure sensitive surface (9) to the electronic instrumentation subsystem (11); Said data transmitting and receiving unit (15) refers to a pressure mapping system that receives the data picked up by the pressure sensitive surface (9) and transmits said data to the microcontroller (12).

[0011] In a fourth aspect, the present invention provides a computer-implemented method for real-time digitization and visualization of graph representations, comprising: a) inputting a physical stimulus on a pressure sensitive surface (9) included in a pressure mapping system as defined in any one of claims 19 to 21; b) converting the physical stimulus into at least one digital signal by said pressure mapping system; c) transmitting at least one digital signal by said pressure mapping system to a computing device that forms a graphical representation of the physical stimulus, said computing device being adapted to enable editing of said graphical representation by a graphical user interface.

[0012] In a fifth aspect, the present invention refers to a computer program comprising instructions which, when executed by a computing device, cause the steps of the method defined in the fourth aspect to be performed.

[0013] In a sixth aspect, the present invention refers to a computer readable data carrier having stored thereon a computer program as defined in the fifth aspect.

[0014] technical issues International Patent Application WO2013113122A1, published August 8, 2013, by Smart Skin Technologies Inc. and entitled "PRESSURE MAPPING AND ORIENTATION SENSING SYSTEM," describes a pressure, force, and orientation sensing system for mapping that uses an array of flexible electrodes and flexible, elastic, piezoresistive materials, such as various types of conductive materials, conductive foams, nanotube-based polymers, carbon black-based polymers, and fabrics coated with graphite-doped plastic. Each sensor is connected to an electronic circuit to measure its electrical resistance, and the data is transmitted to a microprocessor. The data can then be wirelessly transmitted to external devices, such as smartphones and computers, for processing, analysis, and user interaction.

[0015] There is a need to identify other piezoresistive materials that are conducive to accurate and precise measurements, are flexible, and preferably are environmentally friendly materials.

[0016] Furthermore, the individual sensing elements in the prior art may be subject to crosstalk or ghosting effects, which may affect the estimation of the distribution of the mechanical stimulus and lead to misleading conclusions.

[0017] Solutions to the problem The present invention solves the problems of the prior art by impregnating a hydrogel within a fibrous substrate layer to form a hydrogel-impregnated layer zone that can be contacted with electrodes to allow for suitable electrical measurement of physical stimuli applied onto the fibrous layer.

[0018] The present invention solves the prior art problems associated with crosstalk or ghosting effects between sensing elements by individualizing the sensing layer rather than using a continuous sensing film with individualized electrodes. Another approach used by the present invention is to combine the sensing element with a rectifying element to prevent current flow through unwanted paths. The use of a rectifying element for a pressure sensitive element typically requires the introduction of an additional passivation layer to prevent short circuits between the terminals of different elements.

[0019] Advantageous Effects of the Invention In the present invention, hydrogels are an essential element of flexible pressure or strain mapping devices; that is, when hydrogels are biobased polymers or naturally derived materials, they are viable sensing layers for creating sensing devices given their abundance, low cost, sustainability, recyclability, and flexibility. Moreover, hydrogels are attractive materials for sensing layers because they are flexible, their performance in terms of mechanical and sensing properties can be easily tuned, and they can be stretchable, biocompatible, and exhibit self-healing properties.

[0020] Additionally, flexible pressure or strain mapping devices may be arranged in an array to map the pressure or strain distribution and provide a more accurate output in some applications.

[0021] Regarding the incorporation of rectifying elements, the layered structure proposed by the present invention allows adding one rectifying element to each physical sensing element with a minimum of additional layers, which avoids the need for additional passivation layers to prevent short circuits between the terminals of different elements.

[0022] It is contemplated that a flexible pressure or strain mapping device according to the present invention may provide a resistive or capacitive measurement, and the term "or" is to be considered to mean an inclusive "or" rather than an exclusive "or." Thus, the device of the present invention may provide measurements according to any of the following conditions: flexible pressure or strain mapping may provide a resistive measurement; flexible pressure or strain mapping may provide a capacitive measurement; or flexible pressure or strain mapping may provide both capacitive and resistive measurements.

[0023] To facilitate an understanding of the principles according to embodiments of the present invention, reference will be made to the embodiments shown in the drawings and the language used to describe those embodiments. It should be understood that in any event, it is not intended to limit the scope of the present invention to the content of the drawings. Any substitutions or subsequent modifications of the inventive features shown herein, as well as any additional applications of the principles and embodiments of the present invention shown, which would normally occur to one skilled in the art upon reading this specification, are deemed to be within the scope of the claimed invention. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1B is a side view of a flexible pressure or strain mapping device in a one-substrate configuration. [Figure 2] FIG. 12 is a side view of a flexible pressure or strain mapping device in a two-substrate configuration. [Figure 3] FIG. 12 is a side view of a flexible pressure or strain mapping device in a three-substrate configuration. [Figure 4]FIG. 1 is a top view of a flexible pressure or strain mapping device showing a first substrate with a bottom electrode on the backside of the substrate and impregnated hydrogel on the front side. [Figure 5] FIG. 1 is a top view of a flexible pressure or strain mapping device including a rectifying element with a Schottky metal contact, a patterned semiconductor element, and a top electrode on the backside of a substrate. [Figure 6] FIG. 1B is a side view of a flexible pressure or strain mapping device in a two-substrate configuration, where the first substrate contains a hydrogel-impregnated region and a bottom electrode, while the second substrate contains a Schottky metal contact, a patterned semiconductor, and a top electrode on the backside of the second substrate. [Figure 7] FIG. 1C is a top view of a flexible pressure or strain mapping device in a two-substrate configuration, where the first substrate contains a hydrogel-impregnated region and a bottom electrode, while the second substrate contains a Schottky metal contact, a patterned semiconductor, and a top electrode on the backside of the second substrate. [Figure 8] FIG. 12 is a side view of a flexible pressure or strain mapping device in a two-substrate configuration containing a diode, where a first substrate includes a hydrogel-impregnated region and a bottom electrode, while a second substrate includes a Schottky metal contact deposited on the front side of the substrate, a patterned semiconductor impregnated within the substrate, and a top electrode on the back side of the second substrate. [Figure 9] FIG. 10 illustrates the dependence of the relative variation of the output electrical measurement on the applied pressure, showing sensitivity values ​​in two regions of the curve. [Figure 10] FIG. 1 shows a scheme for a 4x4 array of physical sensing elements coupled with diodes, where the six elements to which pressure has been applied are represented by white stars, while the elements under measurement are represented by white dots (row 4 - column 1). [Figure 11]1 shows the current-voltage (IV) curves (solid line) of one physical sensing element (row 4-column 1) coupled with a diode under a pressure of 10 kPa from -2.5 V to 2.5 V, while the current-voltage (IV) curves (dotted lines) of the other six elements (row 1-column 1, row 1-column 4, row 2-column 1, row 2-column 3, row 4-column 3, row 4-column 4) are under a pressure of 10 kPa while the element (row 4-column 1) is in no pressure. [Figure 12] This figure shows the current output of all elements of the array under a voltage of 2.5 V when a pressure of 10 kPa is applied to six elements (row 1-column 1, row 1-column 4, row 2-column 1, row 2-column 3, row 4-column 3, row 4-column 4) in an orthogonal configuration to element (row 4-column 1). [Figure 13] FIG. 1 is a block diagram of a pressure mapping system according to the present invention and its various elements required for a smart surface embodiment. [Figure 14] FIG. 1C is a top view of a flexible pressure or strain mapping device showing a first substrate with bottom electrodes on the backside of the substrate and impregnated hydrogel on the front side, with some bottom electrodes shorted by conductive paths to create a larger area for sensing pressure. [Figure 15] FIG. 1 is a top view of a flexible pressure or strain mapping device showing a first substrate having a first group of interdigitated electrodes and a second group of interdigitated electrodes on the back surface of the substrate and a group of impregnated hydrogel on the front surface. [Figure 16] FIG. 1 is a side view of a flexible pressure or strain mapping device showing a first fibrous substrate including a hydrogel-impregnated layer zone with a first interdigitated electrode and a second interdigitated electrode group in contact with the lower portion of the hydrogel-impregnated layer zone. [Figure 17] FIG. 1 is a side view of a flexible pressure or strain mapping device depicting a first fibrous substrate including a layer zone impregnated with hydrogel and a second fibrous substrate having a first interdigitated electrode and a second interdigitated electrode group on top of the second fibrous substrate. DETAILED DESCRIPTION OF THE INVENTION

[0025] As shown in FIG. 1, the present invention a fibrous substrate layer (1) comprising at least one layer zone (2) impregnated with a hydrogel; at least one first sensor electrode (3) having a portion contacting at least the lower portion of the layer zone (2) impregnated with hydrogel; and at least one second sensor electrode (4) having a portion contacting at least an upper portion of said layer zone (2) impregnated with hydrogel, The hydrogel is a cellulose derivative, and the cellulose derivative hydrogel is selected from the group consisting of cellulose acetate, cellulose acetate phthalate, cellulose acetate butyrate, cellulose acetate trimellitate, hydroxypropyl methylcellulose phthalate, methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, composites thereof, composites thereof with natural polymers, polyvinyl alcohol, polyelectrolyte complexes, interpenetrating polymer networks, cellulose-inorganic hybrid hydrogels, or mixtures or composites thereof.

[0026] Alternatively, the present invention may be implemented as shown in FIGS. a fibrous substrate layer (1) comprising at least one layer zone (2) impregnated with a hydrogel; at least one first interdigitated electrode (19) having a portion contacting at least a portion of the layer zone (2) impregnated with hydrogel; and at least one second interdigital electrode (20) having a portion contacting at least the same portion of said hydrogel-impregnated layer zone (2) contacted by said first interdigital electrode (19), said portion of said hydrogel-impregnated layer zone (2) being selected from its lower portion or its upper portion, provided that when multiple pairs of first interdigital electrodes (19) and second interdigital electrodes (20) are included in said flexible pressure or strain mapping device, at least one electrically insulating layer (21) separates the first interdigital electrodes (19) and second interdigital electrodes (20) from each other; The hydrogel is a cellulose derivative, and the cellulose derivative hydrogel is selected from the group consisting of cellulose acetate, cellulose acetate phthalate, cellulose acetate butyrate, cellulose acetate trimellitate, hydroxypropyl methylcellulose phthalate, methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, composites thereof, composites thereof with natural polymers, polyvinyl alcohol, polyelectrolyte complexes, interpenetrating polymer networks, cellulose-inorganic hybrid hydrogels, or mixtures or composites thereof.

[0027] The present invention also provides a) depositing and impregnating a hydrogel in a fibrous substrate layer (1) to form at least one layer zone (2) impregnated with the hydrogel; b) connecting a portion of the first sensor electrode (3) to at least the lower part of said layer zone (2) impregnated with hydrogel; c) connecting a portion of a second sensor electrode (4) to at least the top of said hydrogel-impregnated layer zone (2).

[0028] Alternatively, the present invention also provides a) depositing and impregnating a hydrogel in a fibrous substrate layer (1) to form at least one layer zone (2) impregnated with the hydrogel; b) connecting a portion of a first interdigitated electrode (19) to at least a portion of said layer zone (2) impregnated with hydrogel; c) connecting a portion of a second interdigital electrode (20) to at least the same portion of the hydrogel-impregnated layer zone (2) contacted by the first interdigital electrode (19), said portion of the hydrogel-impregnated layer zone (2) being selected from its lower portion or its upper portion; d) when multiple pairs of first interdigital electrodes (19) and second interdigital electrodes (20) are included in said flexible pressure or strain mapping device, separating the first interdigital electrodes (19) and second interdigital electrodes (20) from each other by an electrically insulating layer (21).

[0029] The present invention also refers to a pressure mapping system comprising a pressure sensitive surface (9), said pressure sensitive surface (9) comprising a flexible pressure mapping device as defined in the first aspect of the present invention, said pressure mapping system comprising: an electronic instrumentation subsystem (11) including a data transmitting and receiving unit (15), a microcontroller (12), and a power supply; a hybrid connector (10) linking the pressure sensitive surface (9) to the electronic instrumentation subsystem (11); The data transmitting and receiving unit (15) receives the data picked up by the pressure sensitive surface (9) and transmits said data to the microcontroller (12).

[0030] The present invention uses an array of a plurality of first and second sensor electrodes (3) and (4), or a plurality of pairs of first and second interdigitated electrodes (19) and (20), configured to electrically detect various physical stimuli, such as pressure, strain, or stretch, and a plurality of layer zones (2) impregnated with hydrogel.

[0031] In embodiments including multiple pairs of first interdigitated electrodes (19) and second interdigitated electrodes (20), an electrical insulating layer (21) separates the electrodes at their intersections to avoid short circuits between them. The electrical insulating layer (21) may be composed of an uncharged hydrophobic polymer or a polycyclic aromatic hydrocarbon. More preferably, the electrical insulating layer (21) comprises at least one of the group consisting of a lipid polymer, a carbohydrate polymer, a modified carbohydrate polymer, a vinyl polymer, a polycyclic aromatic hydrocarbon, a mixture thereof, or, in the case of the listed polymers, a copolymer thereof.

[0032] In a preferred embodiment of the present invention, the flexible pressure or strain mapping device comprises a second fibrous substrate layer (5) having the second sensor electrode (4) disposed on the lower part of the second fibrous substrate layer (5), the second sensor electrode (4) being simultaneously disposed on and adhered to the upper part of the hydrogel-impregnated layer zone (2) as shown in Figure 2. Thus, this second fibrous substrate layer (5) is placed on top of the hydrogel-impregnated layer zone (2) and ensures electrical contact between the upper surface of the fibrous substrate layer (1) and the second sensor electrode (4) disposed on the back surface of the second fibrous substrate layer (5). Alternatively, the flexible pressure or strain mapping device comprises a second fibrous substrate layer (5) having the first interdigital electrode (19) and the second interdigital electrode (20) disposed on a lower portion of the second fibrous substrate layer (5), the first interdigital electrode (19) and the second interdigital electrode (20) being simultaneously disposed on and adhered to the upper portion of the hydrogel-impregnated layer zone (2), the first interdigital electrode (19) and the second interdigital electrode (20) being separated from each other by an electrically insulating layer (21), as shown in FIG. 15.In these preferred embodiments, the method for preparing a flexible pressure or strain mapping device further comprises the step of adhering a second fibrous substrate layer (5) on top of said hydrogel-impregnated zone (2) in connection with said second sensor electrode (4) disposed on a lower part of said second fibrous substrate layer (5), said second sensor electrode (4) being further disposed on top of said hydrogel-impregnated layer zone (2) and adhering said second fibrous substrate layer (5) on top of said hydrogel-impregnated zone (2) in connection with said second fibrous substrate layer (5). connecting the first interdigitated electrode (19) and the second interdigitated electrode (20) disposed on the lower portion of the layer (5), the first interdigitated electrode (19) and the second interdigitated electrode (20) being further disposed on and adhered to the upper portion of the hydrogel-impregnated layer zone (2), provided that at least one electrically insulating layer (21) separates the first interdigitated electrode (19) and the second interdigitated electrode (20) from each other when multiple pairs of first interdigitated electrodes (19) and second interdigitated electrodes (20) are included in the flexible pressure or strain mapping device. The remaining portion of the second fibrous substrate layer (5) that is not connected or adhered to the upper portion of the hydrogel-impregnated layer zone (2) is connected and adhered to the upper portion of the fibrous substrate layer (1).

[0033] In another preferred embodiment of the present invention, the flexible pressure or strain mapping device comprises a third fibrous substrate layer (6) having the first sensor electrode (3) disposed on top of the third fibrous substrate layer (6) and simultaneously disposed and adhered below the lower portion of the hydrogel-impregnated zone (2), as shown in Figure 3. The remaining portion of the third fibrous substrate layer (6) that is not connected and adhered above the lower portion of the hydrogel-impregnated zone (2) is connected and adhered above the lower portion of the fibrous substrate layer (1). Alternatively, the flexible pressure or strain mapping device comprises a third fibrous substrate layer (6) having the first interdigital electrode (19) and the second interdigital electrode (20) disposed on top of the third fibrous substrate layer (6), as shown in Figure 17, wherein the first interdigital electrode (19) and the second interdigital electrode (20) are simultaneously disposed and adhered below the lower portion of the hydrogel-impregnated layer zone (2). Similarly, for the embodiment of Figure 15, at least one electrically insulating layer (21) separates the first interdigital electrodes (19) and second interdigital electrodes (20) from each other when multiple pairs of first interdigital electrodes (19) and second interdigital electrodes (20) are included in the flexible pressure or strain mapping device.In these preferred embodiments, the method of preparing a flexible pressure or strain mapping device further comprises the step of connecting and adhering a third fibrous substrate layer (6) below the bottom of said hydrogel-impregnated zone (2) with said first sensor electrode (3) disposed on top of said third fibrous substrate layer (6), said first sensor electrode (3) being further disposed on and adhered to said bottom of said hydrogel-impregnated layer zone (2); or connecting a third fibrous substrate layer (6) below the bottom of said hydrogel-impregnated zone (2) with said third fibrous substrate layer (6) The method includes connecting the first interdigital electrode (19) and the second interdigital electrode (20) arranged on the upper part of the plate layer (6), wherein the first interdigital electrode (19) and the second interdigital electrode (20) are further arranged and adhered below the lower part of the layer zone (2) impregnated with hydrogel, provided that when multiple pairs of the first interdigital electrode (19) and the second interdigital electrode (20) are included in the flexible pressure or strain mapping device, the first interdigital electrode (19) and the second interdigital electrode (20) are separated from each other by an electrically insulating layer (21).

[0034] The structure shown in Figure 3 is achieved through contact between a first sensor electrode (3) of a bottom third fibrous substrate layer (6) and a first fibrous substrate layer (1) having a hydrogel-impregnated zone (2) on its bottom surface, and contact between a second sensor electrode (4) of a top second fibrous substrate layer (5) and the top hydrogel-impregnated layer zone (2). In this preferred embodiment, the method of preparing a flexible pressure or strain mapping device further comprises the step of adhering a third fibrous substrate layer (6) in contact with said first sensor electrode (3) below said hydrogel-impregnated zone (2).

[0035] In another embodiment according to the present invention, the flexible pressure or strain mapping device comprises a rectifying element comprising a conductive component (7) and a semiconductor component (8), wherein the semiconductor component (8) is connected to at least one of the group consisting of a first sensor electrode (3), a second sensor electrode (4), a first interdigital electrode (19), or a second interdigital electrode (20), and the conductive component (7) is connected to the semiconductor component (8), as shown in Figures 5, 6, 7, or 8. In this preferred embodiment, the method of preparing a flexible pressure or strain mapping device further comprises the step of connecting the rectifying element comprising the conductive component (7) and the semiconductor component (8) to at least one of the group consisting of a first sensor electrode (3), a second sensor electrode (4), a first interdigital electrode (19), or a second interdigital electrode (20).

[0036] In a preferred embodiment of the present invention, the flexible pressure or strain mapping device comprises at least one array of at least one of a plurality of the group consisting of a first sensor electrode (3), a second sensor electrode (4), a first interdigital electrode (19), or a second interdigital electrode (20), wherein each of the first sensor electrodes (3) or the second sensor electrodes (4) comprised in the array contacts at least the lower or upper portion of the plurality of layer zones (2) impregnated with hydrogel, and each of the first interdigital electrodes (19) or the second interdigital electrodes (20) comprised in the array contacts at least the same portion selected from the lower or upper portion of the plurality of layer zones (2) impregnated with hydrogel, provided that when multiple pairs of the first interdigital electrodes (19) and the second interdigital electrodes (20) are comprised in the flexible pressure or strain mapping device, the first interdigital electrodes (19) and the second interdigital electrodes (20) are separated from each other by an electrically insulating layer (21). More preferably, a plurality of first sensor electrodes (3), or a plurality of pairs of first interdigital electrodes (19) and second interdigital electrodes (20), are arranged in parallel, each of the first sensor electrodes (3), or each of the pairs of first interdigital electrodes (19) and second interdigital electrodes (20) contacts at least the lower portion of the plurality of layer zones (2) impregnated with hydrogel, and the plurality of pairs of first interdigital electrodes (19) and second interdigital electrodes (20) are included in the flexible pressure or strain mapping device, provided that the first interdigital electrodes (19) and second interdigital electrodes (20) are separated from each other by an electrically insulating layer (21) when forming a planar structure configured to enable detection of physical stimuli selected from the group consisting of pressure or strain, as shown in Figure 4.

[0037] In another embodiment, in the flexible pressure or strain mapping device, a plurality of second sensor electrodes (4) or a plurality of pairs of first interdigital electrodes (19) and second interdigital electrodes (20) are arranged in parallel, each of the second sensor electrodes (4) or each of the pairs of first interdigital electrodes (19) and second interdigital electrodes (20) contacts at least an upper portion of a plurality of layer zones (2) impregnated with hydrogel, and the first interdigital electrodes (19) and second interdigital electrodes (20) are separated from each other by an electrically insulating layer (21) when the plurality of pairs of first interdigital electrodes (19) and second interdigital electrodes (20) are contained within the flexible pressure or strain mapping device and form a planar structure configured to enable detection of physical stimuli selected from the group consisting of pressure or strain.

[0038] The serial electrical connection of different bottom and top electrodes in either rows or columns allows for the formation of an array configuration of different hydrogel-impregnated layer zones (2). This planar (XY) structure allows for the detection of precise locations of physical stimuli on the surface of the hydrogel-impregnated layer zones (2). Preferably, the rows or columns are arranged orthogonally among themselves, and each row or column contains multiple physical sensors, i.e., hydrogel-impregnated layer zones (2) and electrodes (3, 4).

[0039] In an exemplary embodiment of the readout protocol, the output of each physical sensing element, hydrogel-impregnated layer zone (2), and electrode of the array is read by applying a specific voltage pulse (having a duration ranging from 1 μs to 10 s and a magnitude ranging from 0.01 to 5 V). The pulse is provided by a microcontroller and delivered to a row or column of physical sensing elements by a multiplexer. After passing through the physical sensing element, the pulse is received by an analog pin of the microcontroller, also using a multiplexer, to select which row or column should be selected. In the microcontroller, the analog signal is converted to a digital signal and presented in a graphic array with a refresh rate ranging from 1 ms to 10 s, considering a 20 x 20 array of physical sensing elements.

[0040] Still, the connections between several hydrogel-impregnated layer zones (2) and electrodes can cause crosstalk and ghosting effects within the array when they are linked to the same electrode row or column.

[0041] In the case of crosstalk, one element of the array can detect an input even when a pressure or strain stimulus is applied to surrounding elements rather than directly to this element. This phenomenon is particularly significant when the sensing component of the device is a continuous material. One strategy to reduce this effect relies on the impregnation of a hydrogel in selected, separate layer zones (2) impregnated with the hydrogel. Because each physical sensing element is individualized, the response of different elements is isolated from surrounding elements. In the case of ghosting, this phenomenon can occur due to the possibility of current flowing in both directions through the physical sensing element, resulting in conductive paths formed by other pressed elements.

[0042] In a preferred embodiment according to the present invention, both the problems of crosstalk and ghosting can be solved through the incorporation of a rectifying element within each element of the sensing array. A rectifying element is an electronic component with two terminals that allow current flow in a specific direction (forward). This is particularly relevant for elements that have very low resistance to current flow in the forward direction, but very high resistance in the opposite direction (reverse). In a preferred embodiment, the rectifying element is a Schottky diode, also known as a Schottky barrier diode, where a potential energy barrier for electrons is formed at the metal-semiconductor junction, forming a rectifying diode. Other types of rectifying elements, such as a pn junction and two coupled transistors, can also be integrated.

[0043] Therefore, in a preferred embodiment, the flexible pressure or strain mapping device comprises an array of a plurality of said rectifying elements, with each conductive component (7) positioned orthogonal to at least one of a group consisting of a first sensor electrode (3), a second sensor electrode (4), or a pair of a first interdigital electrode (19) and a second interdigital electrode (20), as shown in Figure 5 or Figure 7.

[0044] Integrating a rectifying element, such as a Schottky diode, in series with each electrode and the hydrogel-impregnated layer zone (2) prevents current from flowing through unwanted paths, thereby reducing or eliminating crosstalk and ghosting effects within other physical sensing elements. These benefits of reducing crosstalk and ghosting effects are illustrated in FIGS. 11 and 12, along with the pressure pattern diagrams in FIG. 10. The current value of the selected element (row 4, column 1) at a positive applied voltage of 2.5 V is extremely different between the two different configurations in FIG. 11. As shown by the solid line in FIG. 11, when only this element is compressed at 10 kPa, the current value is approximately 6 μA, which is more than 100 times higher than the current value of approximately 50 nA when the other six elements in the orthogonal configuration are compressed instead, as shown by the dotted line in FIG. 11. 12, it can be observed that when six different elements (row 1-column 1, row 1-column 4, row 2-column 1, row 2-column 3, row 4-column 3, row 4-column 4) are pressed, their current values ​​at 2.5 V are at least 50 times higher than the current value in the non-pressed element (row 4-column 1). These facts confirm that the presence of the coupled rectifying element reduces the ghost effect in the element being read (row 4-column 1).

[0045] Preferably, the second fibrous substrate layer (5) includes a Schottky metal contact deposited on the backside of the substrate, followed by patterned deposition of the semiconductor component (8) and the second sensor electrode (4), as shown in the top view of Figure 5. A Schottky diode is formed between the Schottky metal contact and the semiconductor, while the second electrode ensures ohmic contact with the semiconductor.

[0046] The combination of two electrical elements, a physical sensor including a first sensor electrode (3), a second sensor electrode (4), and a hydrogel-impregnated layer zone (2), and a rectifying element, occurs by placing a second fibrous substrate layer (5) containing the rectifying element on top of the hydrogel-impregnated layer zone (2), ensuring electrical contact between the top surface of the hydrogel-impregnated fibrous substrate layer (1) and the second sensor electrode (4) on the bottom surface of the upper second fibrous substrate layer (5). Side and top views of the two-substrate configuration, along with the coupled sensing element and diode, are shown in Figures 6 and 7, respectively.

[0047] This architecture is possible due to several properties of the various components. Because the fibrous substrate layer (1) has specific regions with transverse conductivity due to the hydrogel impregnation, it is possible to deposit the bottom first sensor electrode (3) on the bottom surface of the fibrous substrate layer (1). This fact eliminates the chance of a short circuit between the first sensor electrode (3) and the second sensor electrode (4) on the terminals of the physical sensor. Furthermore, separating the physical sensing element, including the two electrodes and the hydrogel-impregnated layer zone (2), from the Schottky diode in a different substrate, as well as separating the physical sensing element from the Schottky diode in the XY plane, also contributes to a more robust technology. When adjusting between the Schottky diode and the physical sensor, electrical contact is established between the semiconductor component (8) and the hydrogel, resulting in parasitic currents and loss of device performance. This architecture allows for planar separation of the two elements without the need for additional material deposition for passivation.

[0048] This architecture also allows the orientation of both terminal electrodes facing the same surface, the bottom surface in the preferred embodiment presented, allowing the device to be easily integrated with communicating electronics. The architecture presented herein therefore ensures technical advantages such as reduced chance of short circuits, avoidance of direct contact between the hydrogel and the semiconductor component (8), a minimum number of layer materials, and therefore a minimum amount of deposition steps.

[0049] Furthermore, another structure is proposed to combine a physical sensor and a rectifying element while taking advantage of the porous properties of the fibrous substrate layer. As the hydrogel is impregnated into the fibrous substrate layer (1), the semiconductor component (8) can also be impregnated into some regions of the second fibrous substrate layer (5). A side view of the structure is presented in FIG. 8 , showing the conductive component (7) of the rectifying element and the second sensor electrode (4) on different sides of the hydrogel-impregnated layer zone (2). The main advantage of this configuration is that it reduces short circuits between the two electrodes of the diode (Schottky metal contact and ohmic contact), which can result from the deposition method, for example, while maintaining the previous advantages described.

[0050] Hydrogels are piezoelectric responsive materials that can be defined as three-dimensional (3D) networks of hydrophilic polymers that can swell in water and retain large amounts of water while maintaining their structure due to chemical or physical crosslinking of individual polymer chains.

[0051] Some hydrogels may be selected according to their sustainability characteristics with regard to reusability or compostability, ie, the hydrogel comprises a cellulose-based biopolymer.

[0052] In the most preferred embodiment, the hydrogel is a cellulose derivative hydrogel. More preferably, the cellulose derivative hydrogel is selected from the group consisting of cellulose acetate, cellulose acetate phthalate, cellulose acetate butyrate, cellulose acetate trimellitate, hydroxypropyl methylcellulose phthalate, methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, composites thereof, composites thereof with natural polymers, polyvinyl alcohol, polyelectrolyte complexes, interpenetrating polymer networks, cellulose-inorganic hybrid hydrogels, or mixtures or composites thereof. In the most preferred embodiment, the cellulose derivative hydrogel is carboxymethylcellulose or sodium carboxymethylcellulose.

[0053] As explained above, hydrogels are formed through chemical or physical crosslinking of individual polymer chains. Chemical crosslinking can be achieved when the polymers are combined with ionic salts consisting of anions (monovalent, divalent, or trivalent) and cations (monovalent, divalent, or trivalent) through a chemical reaction. As will be understood by those skilled in the art, other forms of chemical crosslinking, such as covalent crosslinking, are also possible.

[0054] In a preferred embodiment according to the present invention, the hydrogel-impregnated layer zone (2) contains at least one salt in the hydrogel matrix, said salt comprising a cation used as an ionic crosslinker selected from the group consisting of monovalent, divalent or trivalent cations, said cation preferably being a zinc, calcium, magnesium, nickel or copper cation. The most preferred salts employed in the present invention are zinc or calcium, which are classified as non-toxic and non-critical materials with regard to environmental issues.

[0055] In a preferred embodiment according to the invention, at least one of the group consisting of the first sensor electrode (3) or the second sensor electrode (4) is selected from the group consisting of conductive materials such as carbon, silver, gold, platinum, copper, aluminum or alloys thereof, or conductive polymers or copolymers, such as polyaniline or poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS), which ensure the electrical connection between the elements to create a rectifying element.

[0056] In a preferred embodiment according to the present invention, at least one of the group consisting of the first sensor electrode (3) or the second sensor electrode (4) is selected from the group consisting of a ribbon, a strip or a wire.

[0057] In a preferred embodiment according to the present invention, the rectifying element comprises a Schottky diode, in which the conductive component (7) is selected from the group consisting of a Schottky metal contact or a conductive polymer or copolymer, such as polyaniline or poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, the Schottky metal contact is selected from the group consisting of silver, gold, platinum, palladium, or alloys containing said metal elements, and the semiconductor component (8) of the Schottky diode is selected from the group consisting of n-type zinc oxide, n-type zinc tin oxide, n-type indium gallium zinc oxide, or n-type silicon-based semiconductors. The second contact of the Schottky diode is an ohmic contact selected from the group consisting of carbon, aluminum, tin, or alloys containing said elements. In the most preferred embodiment according to the present invention, the Schottky metal contact used is silver, the semiconductor component (8) is n-type zinc oxide (ZnO) deposited by screen printing in a carboxymethyl cellulose-based ink, and carbon is used as the second electrode (4).

[0058] The step of depositing and impregnating a hydrogel within the fibrous substrate layer (1) to form at least one layer zone (2) impregnated with the hydrogel may be carried out to form a pattern within specific areas of the fibrous substrate layer (1) to generate individualized sensing elements.

[0059] Elastomers such as polyethylene glycol (PEG) or glycerol can be added to the fibrous substrate layer (1) to improve its mechanical properties. Alternatively, other fibrous structures such as cloth or glass fiber can also be used to improve the mechanical properties of the fibrous substrate layer (1).

[0060] In a preferred embodiment, the fibrous substrate layer (1) is 80 gm -2 Alternatively, the paper layer may be covered by or incorporate cork, cloth fabric, cotton-based fabric, or a mixture thereof.

[0061] In a preferred embodiment, the flexible pressure or strain mapping device comprises a plurality of stacked fibrous substrate layers (1).

[0062] In another embodiment, multiple second fibrous substrate layers (5) may be stacked, with second fibrous substrate layer (5)(n+1) stacked on top of second fibrous substrate layer (5)(n), where n is an integer greater than or equal to 2. In this embodiment, a lower second fibrous substrate layer (5) having said second sensor electrodes (4) is placed on top of and adhered to said fibrous substrate layer (1).

[0063] In other embodiments, multiple third fibrous substrate layers (6) may be stacked, with third fibrous substrate layers (6)(n+1) stacked on top of third fibrous substrate layers (6)(n), where n is an integer greater than or equal to 2. In this embodiment, a higher third fibrous substrate layer (6) having the first sensor electrodes (3) is positioned on and adhered to the lower part of the fibrous substrate layer (1).

[0064] Cellulose-based hydrogels exhibit mechanical responses to deformation due to two distinct properties: i) they are easily deformable when an external force is applied, and ii) the presence of different cations within the structure of cellulose hydrogels creates conductive permeation pathways within the material. Therefore, these materials can be used as the active layer in electrical pressure or strain sensors when the hydrogel is subjected to pressure or strain. Sensing methods can be based on measuring the intrinsic change in the resistance (DC), impedance (AC), or capacitance of the hydrogel, as well as the change in the voltage or current of an electrical signal applied to the hydrogel.

[0065] The electrical measurement of these changes must be achieved by the incorporation of electrodes, which establish a physical sensing element consisting of a hydrogel-impregnated layer zone (2) with two different electrodes in its upper and lower surfaces: at least one first sensor electrode (3) and at least one second sensor electrode (4). Due to the impregnation characteristics of the hydrogel in the fibrous substrate layer (1), different electrode configurations are possible, as shown in Figures 1, 2 and 3 and described herein.

[0066] In a preferred embodiment according to the present invention, any one of the fibrous substrate layer (1), the second fibrous substrate layer (5), or the third fibrous substrate layer (6) is selected from the group consisting of a cellulose fiber-based porous structure, a woven fabric, a nonwoven fabric, a silicone aerogel, a polyurethane aerogel, a silicone foam, a melamine foam, a polyurethane foam, a nickel foam, a sponge (e.g., a sponge from Phylum porifera), a polyurethane sponge, a silicone sponge, a wood-based sponge, a cork matrix, or a paper product containing a composite or derivative thereof. Therefore, any one of the fibrous substrate layer (1), the second fibrous substrate layer (5), or the third fibrous substrate layer (6) includes, but is not limited to, an electrically insulating fibrous substrate. Therefore, the zones of the fibrous substrate layer (1) that are not impregnated with the hydrogel maintain their electrically insulating properties.

[0067] A preferred method for preparing flexible pressure or strain mapping devices according to the present invention centers around printing or drop-on-demand methods, which allow for large-scale production of flexible pressure or strain mapping devices due to the possibility of depositing hydrogels on a variety of substrates, i.e., metals, alloys, glass, polymers, composites, paper, and fabrics, while maintaining reduced production costs. Drop-on-demand methods are compatible with large areas.

[0068] In other embodiments of the preparation of a flexible pressure or strain mapping device according to the present invention, the deposition step can be carried out, for example, by a doctor blade film application step, by a screen printing step, by a flexographic printing step, by a spray painting step, or by an inkjet, roll-to-roll (R2R) compatible step, as will be understood by those skilled in the art. Some methods that can be employed in the deposition step are described in Johanna Zikulnig, Jurgen Kosel, "Flexible Printed Sensors - Overview of Fabrication Technologies," Reference Modules in Biomedical Sciences, Elsevier, 2021.

[0069] In the most preferred embodiment according to the present invention, the hydrogel is incorporated and impregnated into a fibrous substrate layer (1), such as a business paper substrate or a fabric substrate, using a heat treatment below 100°C to create a hydrogel-impregnated activation layer zone (2).

[0070] Therefore, the use of a paper or cloth-based fibrous substrate layer (1) allows for the impregnation of other materials, such as biopolymer hydrogels, into the structure of the substrate, where the porous substrate, consisting of fibers or treads, is surrounded by a polymer component throughout the thickness of the substrate.

[0071] The preparation method according to the present invention also allows for the individualization of hydrogels, since polymer components can be deposited only in selected, defined areas of a fibrous substrate layer (1), such as a paper or fabric substrate. This procedure creates conductive regions on the fibrous substrate layer (1) in a direction transverse to the substrate surface. Thus, a path for electrical conduction is formed from the top surface of the fibrous substrate layer (1) to its bottom surface, allowing for the deposition of electrodes on both sides of the substrate. Furthermore, deposition and impregnation of an electrically insulating material within the substrate can be established in selected areas to improve hydrogel patterning and reduce the ionic conductivity of natural fiber substrates. The insulating material can be a hydrophobic polymer that increases the impermeability of aqueous materials. More specifically, the insulating material can be a wax, which is a water-insoluble organic compound that is a lipid-soluble, malleable solid at ambient temperature and currently has a melting point above 40°C.

[0072] In addition, the impregnation of the hydrogel on the fibrous substrate layer (1) creates a symbiotic phenomenon for the detection of physical stimuli because the fibrous structure of the fibrous substrate layer (1), e.g., paper or fabric, provides mechanical stability to the hydrogel formed therein.

[0073] An embodiment of the present invention, comprising an array of physical sensors, i.e., a hydrogel-impregnated layer zone (2) and electrodes coupled with rectifying elements, can be applied to various mechanical deformation measurements. The surface of the array can be used to detect the presence of an object on its surface, and in addition to the object's location, its shape, weight, and therefore the presence of several different objects on it can be determined. Possible objects include consumer goods, storage products, museum exhibits, and any other use where it is important to determine and monitor the location, shape, weight, and / or presence of an object for inventory control. Additionally, other applications are possible, such as determining the amount of liquid in a container or the presence of a person or living thing, such as an animal, on top of a particular surface.

[0074] In another preferred embodiment of the present invention shown in FIG. 14, multiple sensing elements, i.e., hydrogel-impregnated layer zones (2), are interconnected by connecting at least one conductive path (18) to multiple electrodes selected from the group consisting of a first sensor electrode (3), a second sensor electrode (4), or a pair of a first interdigitated electrode (19) and a second interdigitated electrode (20). The conductive path (18) is selected from the group consisting of a conductive cable or a conductive strip. This embodiment is particularly advantageous when larger sensors are required, and sensing elements can be easily grouped together by shorting the electrodes of individual sensing elements with the conductive path (18). The conductive path (18) is preferably made of a material selected from the group consisting of a conductive material such as carbon, silver, gold, platinum, copper, aluminum, or alloys thereof, or a conductive polymer or copolymer, such as polyaniline or poly(3,4-ethylenedioxythiophene)polystyrenesulfonate (PEDOT:PSS). [Example]

[0075] An exemplary formulation for use in the method of preparing a flexible pressure or strain mapping device is: Sodium carboxymethylcellulose - CMC (Sigma-Aldrich Mw approx. 250,000): solution concentration of approx. 0.1% to approx. 10.0% by weight in water; - Calcium chloride (CaCl2) - in concentrations of about 0.01M to about 10.0M in water; - Zinc chloride (ZnCl2) - in concentrations of about 0.01M to about 10.0M in water, including

[0076] A flexible pressure or strain mapping device according to the present invention was prepared according to the following specifications. Total sensing area of ​​the hydrogel-impregnated layer zone (2): 400 cm 2 , Number of sensing elements containing hydrogel-impregnated layer zones (2): 400; Area of ​​each sensing element: 0.09cm 2 , Minimum distance between sensing elements: 0.9cm, As shown in Figure 9, sensitivity: -10 -2 kPa -1 , Limit of detection: 1g, As shown in Figure 10 and Figure 11, the ghost effect reduction by Schottky diodes: >99%; Response and recovery time: <1s, Fatigue: 1000 pressure cycles, Temporal stability: <10%.

[0077] The invention can also be applied in pressure or strain-sensitive touch and contour smart surfaces for drag and touch interfaces capable of detecting the movement of a finger, pencil, pen, or other object on top of a surface, and for recognizing handwriting.

[0078] The Touch and Contour Smart Surface is a pressure mapping system according to a third aspect of the present invention.

[0079] All physical interactions with the pressure mapping system can be digitized and visualized in real time on a computer software interface. Physical interactions contemplate the use of hands, fingers, pencils, pens, and other devices, which can serve as a means of interaction between the user and the smart surface. Digital content can then be programmed through accessible languages, particularly graphics, making it possible to animate the content created on the sensing surface with movement and sound via a computer program. The embodiment comprises several functionalities arising from various building blocks of the system integrated into three components: a pressure-sensitive surface (9) including a flexible pressure mapping device, as defined in the first aspect of the present invention; a computer program; and a handheld device for controlling the sensing surface's electronics and communicating between the electronics and the computer program.

[0080] An embodiment of a pressure mapping system is depicted in Figure 13 and comprises various elements: a pressure sensitive surface (9), a hybrid connector (10), an electronic instrumentation system (11), a microcontroller (12), a telecommunications unit (13), a data transmission and receiving unit (15), and a power source. In a preferred embodiment, in the pressure mapping system, the power source comprises at least one of the group consisting of a charging unit (14) or a battery (16). In another embodiment, in the pressure mapping system, the electronic instrumentation subsystem (11) comprises an acoustic sensor (17).

[0081] The pressure sensitive surface (9) comprises a flexible pressure or strain mapping device as defined in the first aspect of the present invention.

[0082] The hybrid connector (10) electrically links the pressure sensitive surface (9) to the electronic instrumentation subsystem (11) by means of electrodes, i.e., at least one sensor electrode (3) and at least one sensor electrode (4) included in the flexible pressure mapping device. The hybrid connector (10) can include elements such as needles, springs, clamps, alligator clips, or surface electrodes, which can be constructed of conductive materials such as metals like gold, silver, aluminum, or copper.

[0083] As used herein, the terms "about" and "approximately" refer to a range of values ​​on the order of 10% of the specified number.

[0084] As used herein, the term "substantially" means that the actual value is within an interval of about 10% of a desired value, variable or associated limit, particularly about 5% of a desired value, variable or associated limit, or particularly about 1% of a desired value, variable or associated limit.

[0085] Moreover, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or." That is, unless otherwise specified or clear from context, the phrase "X employs A or B" is intended to mean any of the natural inclusive permutations. That is, the phrase "X employs A or B" is satisfied by any of the following examples: X employs A, X employs B, or X employs both A and B.

[0086] Additionally, the articles "a" and "an" as used in this specification and the appended claims should generally be construed to mean "one or more" unless specifically stated or clear from the context to refer to the singular form.

[0087] Moreover, as used herein, the term "exemplary" is intended to mean serving as an illustration or example of something and is not intended to indicate preference.

[0088] The subject matter described above is provided as an explanation of the present invention and should not be construed as limiting the present invention. The terminology used to describe particular embodiments according to the present invention should not be construed as limiting the present invention. As used in this description, definite and indefinite articles, in their singular form, are intended to include the plural in their interpretation unless the context of the description clearly indicates otherwise. It will be understood that the terms "comprise" and "include," as used herein, specify the presence of features, elements, components, steps, and related operations, but do not exclude the possibility of other features, elements, components, steps, and operations being considered.

[0089] All modifications must be considered to be within the scope of protection of the present invention unless they modify the essential features of the following claims.

[0090] Reference Symbol List 1. a fibrous substrate layer; 2. A layer zone impregnated with hydrogel; 3. a first sensor electrode; 4. a second sensor electrode; 5. A second fibrous substrate layer; 6. a third fibrous substrate layer; 7. Conductive components; 8. Semiconductor components; 9. Pressure sensitive surfaces; 10. Hybrid connector, 11. Electronic instrumentation subsystem, 12. Microcontrollers, 13. Telecommunications unit; 14. Charging unit, 15. Data sending and receiving unit, 16. Battery, 17. Acoustic sensors, 18. Conductive pathways, 19. First interdigitated electrode; 20. A second interdigitated electrode; 21. Electrical insulating layer,

[0091] Citation List The citation list is as follows:

[0092] Patent documents Patent Document 1: International Patent Application No. WO2013113122A1, filed August 8, 2013, by Smart Skin Technologies INC., entitled "PRESSURE MAPPING AND ORIENTATION SENSING SYSTEM."

[0093] Non-patent literature Non-patent literature: Johanna Zikulnig, Jurgen Kosel, "Flexible Printed Sensors - Overview of Fabrication Technologies", Reference Modules in Biomedical Sciences, Elsevier, 2021. [Explanation of symbols]

[0094] 1. Fibrous substrate layer 2. Hydrogel-impregnated layer zone 3 First sensor electrode 4 Second sensor electrode 5 Second fibrous substrate layer 6. Third fibrous substrate layer 7 Conductive Components 8 Semiconductor Components 9 Pressure sensitive surface 10 Hybrid Connector 11 Electronic Instrumentation Subsystem 12 Microcontrollers 13 Telecommunications Unit 14 Charging unit 15 Data sending and receiving units 16 Battery 17 Acoustic Sensor 18 Conductive Path 19 First interdigitated electrode 20 Second interdigital electrode 21 Electrical insulating layer

Claims

1. 1. A flexible pressure or strain mapping device, comprising: a fibrous substrate layer (1) comprising at least one layer zone (2) impregnated with a hydrogel; at least one first sensor electrode (3) having a portion contacting at least a lower portion of said layer zone (2) impregnated with hydrogel; at least one second sensor electrode (4) having a portion contacting at least an upper portion of the layer zone (2) impregnated with hydrogel; Equipped with 1. A flexible pressure or strain mapping device, wherein the hydrogel is a cellulose derivative selected from the group consisting of cellulose acetate, cellulose acetate phthalate, cellulose acetate butyrate, cellulose acetate trimellitate, hydroxypropyl methylcellulose phthalate, methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, composites thereof or composites thereof with natural polymers, polyvinyl alcohol, polyelectrolyte complexes, interpenetrating polymer networks, cellulose-inorganic hybrid hydrogels, or mixtures or composites thereof, The device further comprises at least one of the group consisting of a second fibrous substrate layer (5) or a third fibrous substrate layer (6), the second sensor electrode (4) is disposed on the lower part of the second fibrous substrate layer (5), and the second sensor electrode (4) is simultaneously disposed on and adhered to the upper part of the layer zone (2) impregnated with hydrogel; A flexible pressure or strain mapping device, wherein the first sensor electrode (3) is positioned on top of the third fibrous substrate layer (6), and the first sensor electrode (3) is simultaneously positioned and adhered underneath the bottom of the hydrogel-impregnated zone (2).

2. 1. A flexible pressure or strain mapping device, comprising: a fibrous substrate layer (1) comprising at least one layer zone (2) impregnated with a hydrogel; at least one first interdigitated electrode (19) having a portion in contact with at least a portion of said layer zone (2) impregnated with hydrogel; and at least one second interdigital electrode (20) having a portion contacting at least the same portion of the layer zone (2) impregnated with hydrogel that is contacted by the first interdigital electrode (19), wherein the portion of the layer zone (2) impregnated with hydrogel is selected from its lower portion or its upper portion, and wherein at least one electrically insulating layer (21) separates the first interdigital electrode (19) and the second interdigital electrode (20) from each other when a plurality of pairs of the first interdigital electrode (19) and the second interdigital electrode (20) are included in the flexible pressure or strain mapping device, 1. A flexible pressure or strain mapping device, wherein the hydrogel is a cellulose derivative selected from the group consisting of cellulose acetate, cellulose acetate phthalate, cellulose acetate butyrate, cellulose acetate trimellitate, hydroxypropyl methylcellulose phthalate, methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, composites thereof or composites thereof with natural polymers, polyvinyl alcohol, polyelectrolyte complexes, interpenetrating polymer networks, cellulose-inorganic hybrid hydrogels, or mixtures or composites thereof, The device further comprises at least one of the group consisting of a second fibrous substrate layer (5) or a third fibrous substrate layer (6), the first interdigitated electrode (19) and the second interdigitated electrode (20) are disposed on the lower part of the second fibrous substrate layer (5), and the first interdigitated electrode (19) and the second interdigitated electrode (20) are simultaneously disposed on and adhered to the upper part of the hydrogel-impregnated layer zone (2), provided that when multiple pairs of the first interdigitated electrode (19) and the second interdigitated electrode (20) are included in the flexible pressure or strain mapping device, the first interdigitated electrode (19) and the second interdigitated electrode (20) are separated from each other by an electrically insulating layer (21); A flexible pressure or strain mapping device, wherein the first interdigital electrode (19) and the second interdigital electrode (20) are positioned on top of the third fibrous substrate layer (6), and the first interdigital electrode (19) and the second interdigital electrode (20) are simultaneously positioned and adhered under a lower portion of the hydrogel-impregnated layer zone (2), and when multiple pairs of the first interdigital electrode (19) and the second interdigital electrode (20) are included within the flexible pressure or strain mapping device, the first interdigital electrode (19) and the second interdigital electrode (20) are separated from each other by an electrically insulating layer (21).

3. 3. A flexible pressure or strain mapping device as claimed in any one of claims 1 to 2, comprising a rectifying element including a conductive component (7) and a semiconductor component (8), the semiconductor component (8) being connected to at least one of the group consisting of the first sensor electrode (3), the second sensor electrode (4), the first interdigital electrode (19) or the second interdigital electrode (20), and the conductive component (7) being connected to the semiconductor component (8).

4. 4. The flexible pressure or strain mapping device according to claim 1, comprising at least one array of at least one of a plurality of the group consisting of the first sensor electrode (3), the second sensor electrode (4), the first comb electrode (19) or the second comb electrode (20), wherein each of the first sensor electrode (3) or the second sensor electrode (4) comprised in the array contacts at least a lower or an upper part of a plurality of layer zones (2) impregnated with hydrogel, and each of the first comb electrode (19) or the second comb electrode (20) comprised in the array contacts at least a same part selected from the lower or the upper part of the plurality of layer zones (2) impregnated with hydrogel.

5. 5. The flexible pressure or strain mapping device of claim 4, wherein a plurality of first sensor electrodes (3) or a plurality of pairs of a first interdigital electrode (19) and a second interdigital electrode (20) are arranged in parallel, each of the first sensor electrodes (3) or each of the pairs of a first interdigital electrode (19) and a second interdigital electrode (20) contacting at least a lower portion of a plurality of layer zones (2) impregnated with hydrogel to form a planar structure configured to enable detection of a physical stimulus selected from the group consisting of pressure or strain.

6. 6. The flexible pressure or strain mapping device according to claim 4 or 5, wherein a plurality of second sensor electrodes (4) or a plurality of pairs of a first interdigital electrode (19) and a second interdigital electrode (20) are arranged in parallel, each of the second sensor electrodes (4) or each of the pairs of a first interdigital electrode (19) and a second interdigital electrode (20) contacting at least an upper portion of a plurality of layer zones (2) impregnated with hydrogel to form a planar structure configured to enable detection of a physical stimulus selected from the group consisting of pressure or strain.

7. 7. A flexible pressure or strain mapping device as claimed in any one of claims 3 to 6, comprising an array of a plurality of said rectifying elements, each conductive component (7) being arranged orthogonal to at least one of the group consisting of the first sensor electrode (3), the second sensor electrode (4), or a pair of a first interdigital electrode (19) and a second interdigital electrode (20).

8. 8. A flexible pressure or strain mapping device according to any one of claims 3 to 7, wherein the multiple layer zones (2) impregnated with hydrogel are interconnected by connecting at least one conductive path (18) to multiple electrodes selected from the group consisting of a first sensor electrode (3), a second sensor electrode (4) or a pair of a first interdigital electrode (19) and a second interdigital electrode (20).

9. 9. A flexible pressure or strain mapping device according to any one of claims 1 to 8, wherein the hydrogel impregnated layer zone (2) comprises at least one salt within the hydrogel matrix, said salt comprising a cation selected from the group consisting of monovalent, divalent or trivalent cations used as ionic crosslinks, said cations being preferably zinc, calcium, magnesium, nickel or copper cations or mixtures thereof.

10. 10. The flexible pressure or strain mapping device according to any one of claims 1 to 9, wherein any one of the first, second or third fibrous substrate layers (1, 5, 6) is selected from the group consisting of cellulose fibre based porous structures, woven fabrics, non-woven fabrics, silicone aerogels, polyurethane aerogels, silicone foams, melamine foams, polyurethane foams, nickel foams, sea sponges, e.g. Porifera sponges, polyurethane sponges, silicone sponges, wood based sponges, cork matrices or paper products including composites or derivatives thereof.

11. 11. A flexible pressure or strain mapping device according to any one of claims 1 to 10, wherein at least one of the group consisting of the first sensor electrode (3) or the second sensor electrode (4) is selected from the group consisting of carbon, silver, gold, platinum, copper, aluminium or alloys thereof, or a conductive polymer or copolymer, such as polyaniline or poly(3,4 ethylenedioxythiophene) polystyrene sulfonate.

12. 12. The flexible pressure or strain mapping device of claim 3, wherein the rectifying element comprises a Schottky diode, the conductive component (7) being selected from the group consisting of a Schottky metal contact or a conductive polymer or copolymer, such as polyaniline or poly(3,4 ethylenedioxythiophene) polystyrene sulfonate, the Schottky metal contact being selected from the group consisting of silver, gold, platinum, palladium, or an alloy containing said metal element, and the semiconductor component (8) of the Schottky diode being selected from the group consisting of n-type zinc oxide, n-type zinc tin oxide, n-type indium gallium zinc oxide, or an n-type silicon-based semiconductor.

13. A method of preparing a flexible pressure or strain mapping device as defined in claim 1 or any one of claims 3 to 12, comprising the steps of: a. depositing and impregnating a hydrogel into a fibrous substrate layer (1) to form at least one layer zone (2) impregnated with the hydrogel; b. connecting a portion of a first sensor electrode (3) to at least a lower portion of said layer zone (2) impregnated with hydrogel; c. connecting a portion of a second sensor electrode (4) to at least an upper portion of said layer zone (2) impregnated with hydrogel; A method comprising: connecting and adhering a second fibrous substrate layer (5) with the second sensor electrode (4) arranged on the lower part of the second fibrous substrate layer (5) on the upper part of the zone (2) impregnated with hydrogel, the second sensor electrode (4) being further arranged and adhered on the upper part of the layer zone (2) impregnated with hydrogel; connecting and adhering a third fibrous substrate layer (6) with the first sensor electrode (3) arranged on an upper portion of the third fibrous substrate layer (6) below a lower portion of the hydrogel-impregnated zone (2), the first sensor electrode (3) being further arranged and adhered on the lower portion of the hydrogel-impregnated layer zone (2); The method of claim 1, further comprising at least one of the following:

14. A method of preparing a flexible pressure or strain mapping device as defined in any one of claims 2 to 12, comprising the steps of: a. depositing and impregnating a hydrogel into a fibrous substrate layer (1) to form at least one layer zone (2) impregnated with the hydrogel; b. connecting a portion of a first interdigitated electrode (19) to at least a portion of said layer zone (2) impregnated with hydrogel; c. connecting a portion of a second interdigital electrode (20) to at least the same portion of the layer zone (2) impregnated with hydrogel that is contacted by the first interdigital electrode (19), said portion of the layer zone (2) impregnated with hydrogel being selected from its lower portion or its upper portion; d. isolating the first interdigital electrodes (19) and the second interdigital electrodes (20) from each other by an electrically insulating layer (21) when multiple pairs of the first interdigital electrodes (19) and the second interdigital electrodes (20) are included in the flexible pressure or strain mapping device; A method comprising: connecting a second fibrous substrate layer (5) with the first interdigital electrode (19) and the second interdigital electrode (20) arranged on the lower part of the second fibrous substrate layer (5) on the upper part of the zone (2) impregnated with hydrogel, the first interdigital electrode (19) and the second interdigital electrode (20) being further arranged and adhered on the upper part of the layer zone (2) impregnated with hydrogel; connecting a third fibrous substrate layer (6) with the first interdigital electrode (19) and the second interdigital electrode (20) arranged on an upper part of the third fibrous substrate layer (6) below a lower part of the zone (2) impregnated with hydrogel, the first interdigital electrode (19) and the second interdigital electrode (20) being further arranged and adhered below the lower part of the layer zone (2) impregnated with hydrogel; The method of claim 1, further comprising at least one of the following:

15. 15. A method for preparing a flexible pressure or strain mapping device according to any one of claims 13 to 14, further comprising the step of connecting a rectifying element comprising a conductive component (7) and a semiconductor component (8) to at least one of the group consisting of the first sensor electrode (3), the second sensor electrode (4), the first interdigital electrode (19) or the second interdigital electrode (20).

16. A pressure mapping system comprising a pressure sensitive surface (9), the pressure sensitive surface (9) comprising a flexible pressure mapping device as defined in any one of claims 1 to 12, the pressure mapping system comprising: An electronic instrumentation subsystem (11) including a data transmitting and receiving unit (15), a microcontroller (12) and a power supply; a hybrid connector (10) linking said pressure sensitive surface (9) to said electronic instrumentation subsystem (11); Further equipped with A pressure mapping system, characterized in that said data transmitting and receiving unit (15) receives data picked up by said pressure sensitive surface (9) and transmits said data to said microcontroller (12).

17. The pressure mapping system of claim 16, wherein the power source comprises at least one of the group consisting of a charging unit (14) or a battery (16).

18. 18. A pressure mapping system according to any one of claims 16 to 17, wherein the electronic instrumentation subsystem (11) includes an acoustic sensor (17).

19. 1. A computer-implemented method for real-time digitization and visualization of graph representations, comprising: a. inputting a physical stimulus on a pressure-sensitive surface (9) contained within a pressure mapping system as defined in any one of claims 16 to 18; b. converting said physical stimulus into at least one digital signal by said pressure mapping system; c) transmitting said at least one digital signal by said pressure mapping system to a computing device that forms a graphical representation of said physical stimulus, said computing device being adapted to enable editing of said graphical representation by a graphical user interface; 16. A computer-implemented method according to claim 15, characterized in that it comprises:

20. 20. A computer program comprising instructions which, when executed by a computing device, cause the computing device to perform the steps of the method defined in claim 19.

21. 21. A computer readable data carrier having stored thereon a computer program as defined in claim 20.

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