Sensor devices and methods of production

Abstract

A method for producing a sensor assembly is provided The method comprises the steps of providing a sensor material sheet comprising a plurality of sensor units, a plurality of bridging strips and a remainder of the sensor material sheet, arranged such that the sensor units are separated from each other and each bridging strip interconnects a sensor unit with the remainder of the sensor material sheet; arranging a flexible adhesive sheet overlaying one side of the sensor material sheet, such that the sensor material sheet adheres to the flexible adhesive sheet; separating the remainder of the sensor material sheet from the adhesive sheet, causing each bridging strip to disengage from the sensor units, such that the sensor units remain on the adhesive sheet; arranging the adhesive sheet with the sensor units facing a flexible substrate with a plurality of electrodes disposed thereon; aligning each sensor unit with an associated first electrode and an associated second electrode; and joining the adhesive sheet and the flexible substrate such that the adhesive sheet adheres to the flexible substrate, thereby sandwiching at least the plurality of sensor units and the plurality of electrodes therebetween. A sensor assembly is also provided.

Description

[0001] SENSOR DEVICES AND METHODS OF PRODUCTION

[0002] FIELD OF INVENTION

[0003] The present invention relates to a sensor assembly and methods for producing a sensor assembly.

[0004] BACKGROUND OF THE INVENTION

[0005] Pressure sensors are essential devices that measure the force exerted on a given area. These sensors are widely used in various applications, including automotive systems, industrial processes, and medical devices, due to their accuracy and reliability. Pressure sensors convert the mechanical pressure into electrical signals using various technologies, such as piezoresistive, capacitive, or optical methods. When pressure is applied, the sensor’s output changes, allowing for precise measurements of pressure levels. One of the key advantages of pressure sensors is their ability to provide real-time data. Additionally, many pressure sensors are designed to be compact, making them suitable for applications where space is limited.

[0006] However, there are challenges associated with readouts from pressure sensors. One significant difficulty is signal noise, which can arise from environmental factors or electronic interference. This noise can obscure the true readings, leading to inaccuracies. Furthermore, pressure sensors can be sensitive to temperature variations, which may also affect their output. To mitigate these issues, advanced signal processing techniques and temperature compensation methods are often employed, but they can add complexity to the system.

[0007] Sandwich structures that feature one electrode on each side of a sensor are commonly used in various sensing applications. Such designs present several drawbacks. For example, the materials used for the electrodes and the sensor can have different thermal expansion coefficients, and such a mismatch can result in thermal stress, which may affect the sensor’s accuracy and reliability, particularly in environments with fluctuating temperatures. Moreover, the bonding between the electrodes and the sensor layer can be susceptible to delamination, especially under mechanical stress or thermal cycling. This delamination can compromise the sensor’s integrity and lead to failure.

[0008] SUMMARY OF THE INVENTION

[0009] The present invention provides a sensor assembly, and devices comprising such a sensor assembly. The present invention also provides methods for producing a sensor assembly and methods for producing devices comprising one or more sensor assemblies.According to an aspect of the invention, a sensor assembly is provided. The sensor assembly comprises a plurality of sensor units, each sensor unit associated with a first and a second electrode arranged at a first side thereof; a flexible adhesive sheet, at least partly adhered to the plurality of sensor units and arranged at a second, substantially opposite, side of the plurality of sensor units; and a flexible substrate comprising electrically conductive elements, arranged at the first side of the plurality of sensor units. A first surface of each of the plurality of sensor units is arranged in electrical contact with the associated first electrode and second electrode. The sensor units are pressure sensors, preferably piezoresistive sensors, changing their respective electrical resistance when pressure is applied.

[0010] The sensor units arranged in electrical contact with the electrodes may also be referred to as a pressure sensor matrix, a sensor array or a sensor grid. The flexible adhesive sheet, which is adhesive at least on the side to which the sensors are adhered, is adhered to the flexible substrate with the sensor units and electrodes arranged between the adhesive sheet and the flexible substrate, thereby insulating the matrix from the environment. Thereby, an increased resistance to external stresses, such as humidity and / or temperature changes, is achieved.

[0011] The sensor assembly disclosed herein does not employ a sandwich structure that features one electrode on each side of a sensor. Thus, the sensor assembly disclosed herein may be referred to as a single-layer design. Such a design avoids the rigidity of prior art sensor assemblies and thus makes it more adaptable to applications requiring bending, twisting, or dynamic motion. Furthermore, an increased robustness is achieved, since without two interfaces between sensor and two electrodes on two different layers, stress concentration is minimized, lowering the risk of mechanical failure under dynamic or repetitive loading This in turn reduces the risk of delamination or separation, which are common issues in multi-layer designs subjected to mechanical or thermal cycling.

[0012] In addition, an improved manufacturing process is facilitated due to the configuration of the sensor assembly. With fewer components, there is less need for precise alignment or complex adhesion techniques; and the use of fewer materials leads to a lighter, thinner, and more compact sensor assembly, lowering the risk of defects as well as decreasing manufacturing costs.

[0013] The configuration of the sensor assembly disclosed herein also provides an easier integration with other components, since there are fewer points requiring electrical connection. Furthermore, the configuration ensures that the sensor assembly is less likely to lose signal strength due to poor layer adhesion.The sensor assembly may be described as a thin structure having a compact profile that makes it easily used in applications requiring curved surfaces, without adding bulk. The thickness of the sensor assembly may be adapted to fit the circumstances at hand. In some examples the thickness of the sensor assembly is 0.3 to 1 .5 mm, such that the minimum thickness is 0.3 mm and the maximum thickness is 1.5 mm. In some examples, the thickness ranges from (and including) 0.5 mm up to and including 1 mm, or from (and including) 0.7 mm up to and including 1 mm. In some examples the thickness is approximately 0.8 mm. The thickness indicates the distance from an outer surface of the flexible adhesive sheet to an outer surface of the flexible substrate.

[0014] Unless stated otherwise, the term flexible, when used herein relating to the flexible adhesive sheet and the flexible substrate, as well as the sensor assembly, defines a material that deforms elastically when subjected to pressure, in a non-extreme temperature range, for example between -10 degrees Celsius and +40 degrees Celsius. In other words, the term flexible is to be interpreted as it would by a person skilled in the art. In some examples, parts of the flexible adhesive sheet, the flexible substrate, and / or the sensor assembly itself, may deform plastically under normal conditions. However, the flexible components herein would not undergo a ruptural deformation unless subjected to extreme pressure, in a context for which the sensor assembly is not intended to be used. Thus, the term flexible, when used herein, is used to differentiate the “flexible” components from rigid and brittle components, which would rupture when subjected to pressure and / or when being bent, twisted or otherwise deformed. Flexible materials used in the flexible components herein may include any suitable material, such as polyamide, polyether ether ketone (PEEK), polyester, and rubber-based materials or synthetic rubber-based materials. In a non-limiting example, the elasticity modulus of a flexible material herein may be of a value from 0.1 GPa up to and including 5 GPa; such as from 2 GPa up to and including 4 GPa; for example 2.5 GPa or 3.6 GPa.

[0015] The sensor units may be configured as circular dots, squares and / or cylinders, of pressure sensitive material, such as piezoresistive material. The sensors may have any suitable cross -section, such as a circular, rectangular or triangular cross-section. Piezoresistive sensors are particularly suitable for use in the sensor assembly, as they provide variable resistance for applied pressure and are suitable for static as well as dynamic response.

[0016] The first electrode and the second electrode are advantageously arranged adjacent each other, but at the same time spaced apart from each other, so that they are not physically connected. Thereby, the sensor units may be arranged in contact with both the first electrode and thesecond electrode such that the electrical resistance of the sensor unit changes when pressure is applied to the sensor unit. The first electrode and the second electrode may be said to be arranged in electrode pairs, where each sensor unit is associated with an electrode pair.

[0017] The first and second electrodes may be designed and / or configured in any suitable way. For example, the first and second electrodes may be substantially coplanar. Thereby, the first and second electrodes may be arranged on the same plane, whereby the corresponding sensor units may be arranged on a substantially parallel plane, facilitating the production of the sensor assembly and improving the accuracy of the reading of the sensor units . The first and second electrodes are suitably printed on the flexible substrate.

[0018] In some examples, the first and second electrodes are concentric, wherein the first electrode may be arranged as an outer conductive circle and the second electrode may be arranged as an inner conductive circle, or vice versa. The outer conductive circle is arranged at a radial distance from the inner conductive circle, and encircles the inner conductive circle. Alternatively, the first electrode may be arranged as an outer rectangle and the second electrode may be arranged as an inner rectangle, or vice versa. The sides of the outer conductive rectangle are arranged offset from the sides of the inner conductive rectangle, such that the outer rectangle is arranged around, but spaced apart from, the inner rectangle. In examples where the first and second electrodes are concentric, the sensor assembly is arranged with an electronics system, such as tracks arranged on the flexible substrate, which connects to the outer circle, or rectangle, and the inner circle, or rectangle, sequentially to measure the electrical resistance of each sensor unit.

[0019] In other examples, the first and second electrodes are not concentric, but comprise complementary extensions that are arranged adjacent and at a distance from each other. In other words, the complementary extensions or shapes of the first and second electrodes are arranged adjacent each other, but at the same time spaced apart.

[0020] The adhesive sheet is adhesive on at least the surface facing the sensor units, but may in some examples be adhesive on an opposite surface as well.

[0021] The plurality of sensor units may be arranged as a sensor array comprising at least four sensor units arranged in rows and columns. Such a sensor array may comprise several rows and several columns, and a multitude of sensor units arranged in such a structure. Each sensor unit may thereby be located by selecting one row and one column. Such an array structure reduces the wiring required for the sensor assembly.The first and second electrodes, associated with the sensor units, may be arranged in an electrode array comprising rows and columns corresponding to the sensor array, such that each first electrode and second electrode are substantially aligned with the associated sensor unit, enabling physical contact between the first surface of the sensor unit and both of the associated first electrode and second electrode. In other words, each electrode pair associated with a sensor unit may be arranged in an electrode array comprising rows and columns corresponding to the rows and columns of the sensor array, such that each electrode pair is substantially aligned with the associated sensor unit.

[0022] In examples where the electrodes are concentric, each sensor unit advantageously aligns concentrically with a corresponding concentric electrode .

[0023] By arranging the plurality of sensor units as a sensor array with a row / column structure, an improved accuracy in the reading of the sensor units is achieved. When combined with a corresponding electrode array, even further benefits are achieved. An array configuration is beneficial when the sensor assembly is used within or arranged together with, a material or device that is designed to bend. Such a configuration allows for relatively small and separated pressure sensors, and corresponding electrodes, which are not affected by bending, and provide an accurate readout even if the sensor assembly is bent or twisted. In addition, such a configuration decreases the risk of crosstalk resulting in inaccurate readings. Crosstalk may also be referred as “ghost touch” or “phantom touch”, denoting an incorrect indication of applied pressure.

[0024] The first electrodes in each row of the electrode array may be electrically connected and the second electrodes in each column of the electrode array may be electrically connected. Alternatively, the first electrodes in each column of the electrode array may be electrically connected and the second electrodes in each row of the electrode array may be electrically connected. Such a configuration enables a compact and effective design of the sensor assembly.

[0025] A first track may connect at least two of the first electrodes, each associated with a respective sensor unit, and a second track may connect at least two of the second electrodes, each associated with a respective sensor unit. The first track may be arranged on a first surface of the flexible substrate and the second track may be arranged on a second surface of the flexible substrate. In some examples, the first track and the second track are both arranged on the same surface of the flexible substrate.The flexible substrate may comprise at least one via extending through the flexible substrate from the first surface to the second surface thereof. In such examples, the electrodes of the plurality of electrodes may be arranged on the first surface of the flexible substrate and electrically connected to at least one track on the second surface of the flexible substrate through the at least one via. Each sensor unit and a corresponding electrode pair may be arranged in alignment with a respective via in the flexible substrate.

[0026] In other examples, the flexible substrate may comprise at least three vias extending through the flexible substrate from the first surface to the second surface thereof. In such examples, the electrodes of the plurality of electrodes may be arranged on the first surface of the flexible substrate and electrically connected to a first and a second track on the second surface of the flexible substrate through the at least three vias. For example, two vias may connect the first electrode of an electrode pair to a first track, and the third via may connect the second electrode to a second track, or vice versa.

[0027] In some examples, the first track connects all of the first electrodes in a column and the second track connects all of the second electrodes of a row, or vice versa. The sensor assembly may comprise a plurality of first tracks and / or second tracks, depending on the design of the sensor array and electrode array.

[0028] The flexible substrate may comprise a double sided or multi-layered flexible printed circuit board (FPCB / FPC) and / or at least one integrated circuit. Using a double sided or multilayered FPCB as the flexible substrate is beneficial since it allows the tracks interconnecting the first and second electrodes to be arranged on different sides, or on different layers, of the flexible substrate. The FPCB used in the context of the sensor assembly herein may be any suitable FPCB that conforms with general design rules for flexible PCBs used in the art. As a non-limiting example, flexible PCBs, constructed with a polyimide substrate, copper conductive layers, and protective cover layer, offer thin, durable, and bendable circuits with specifications such as: 0.05-0.3 mm thickness; 1 oz / ft2(approximately 0.0031 g / cm2) copper; and operating temperatures of -40°C to 105 °C, which is ideal for compact and dynamic applications. Its bend radius is often specified as 10 times the thickness of the flexible PCB for repeated bending. For an FPCB used in the sensor assembly herein, a stable bending radius from 10:1 up to and including 20:1; a semi-dynamic bending radius from 20:1 up to and including 50:1; and a dynamic bending radius from 100:1 up to and including 150:1 are advantageous.The sensor assembly may further comprise a readout circuit, comprising at least one of each of the following:

[0029] a resistance measurement integrated circuit;

[0030] a micro-controller;

[0031] an operational amplifier;

[0032] a resistor;

[0033] a multiplexer; and

[0034] a wireless transmitter.

[0035] In some examples, the readout circuit comprises at least two multiplexers, one per column and one per row of the sensor array. The readout circuit may be configured in any suitable way, for example using a zero potential method (ZPM) or voltage feedback method (VFM). However, the risk of crosstalk, also called ghost touch or touch errors, should be taken into account when configuring the readout circuit.

[0036] The wireless transmitter may be any suitable transmitter, transmitting data to other components, such as a processing unit, arranged in connection with the sensor assembly, or integrated into the sensor assembly. The wireless transmitter may communicate with a communication module, such as a Bluetooth module or a Wi-Fi module. In some examples, the wireless transmitter itself may comprise such a communication module.

[0037] The sensor assembly may comprise a plurality of apertures arranged as through -holes extending from a first surface of the sensor assembly to a second surface of the sensor assembly and intersecting the flexible substrate and the flexible adhesive sheet. Such a configuration of the sensor assembly facilitates the incorporation of the sensor assembly into any suitable device. Advantageously, the apertures enable an efficient additive manufacturing process, where the sensor assembly is fused, or integrated, with an additive manufacturing material.

[0038] The flexible sensor assembly disclosed herein is particularly suitable for incorporation in a pressure sensing device, because it allows for interconnection and integration of electronic components within the device. Such a pressure sensing device is advantageously configured to allow bending, stretching, twisting or any other type of movement that it may be subjected to, when in use or in storage, while at the same time providing accurate readings from the sensors. Furthermore, the pressure sensing device comprising the sensor assembly may be configured to be lightweight and slim, facilitating integration with other devices or component layers, as well as providing ease of storage and transportation.According to yet another aspect of the invention, robotic skin is provided, comprising the sensor assembly as disclosed herein. The robotic skin may be any suitable piece of robotic skin. Robotic skin may also be referred to as electronic skin. In such a device, the sensor assembly enables the simulation of a sense of touch, which is a highly challenging type of simulation in robotics. Furthermore, such a robotic skin contributes to the proprioception of the robot in which it is used, i.e., the sense of self-movement, force, and position of the robot. The robotic skin may be configured to be connected to any suitable model for interpreting information derived from the robotic skin touching an object or a surface. Such information may be referred to as touch data or touch information. When comprised in the robotic skin, the sensor assembly provides an output of data from the robotic skin, as the sensor units of the sensor assembly change their respective electrical resistance when pressure is applied to the robotic skin. Touch data output from the sensor assembly also provides an indication of the location of the touch on the robotic skin.

[0039] The sensor assembly disclosed herein is particularly suitable for use in robotic skin for several reason. The flexible construction of the sensor assembly allows it to be integrated seamlessly onto curved or irregular surfaces of robots, ensuring full coverage and adaptability. This is particularly important for humanoid robots or soft robotics that require tactile sensing across complex body structures. Furthermore, with a dense network of sensor units, the sensor assembly provides high spatial resolution, enabling robots to identify and localise contact points accurately. This enhances manipulation capabilities, such as grasping objects of varying shapes and textures with appropriate force.

[0040] As discussed above, the sensor assembly is configured in a manner that provides a high level of durability. The sensor assembly is configured to withstand mechanical stress and repetitive use, which makes it reliable in long-term applications. This ensures consistent performance in industrial robotics or field environments.

[0041] In addition, the sensor assembly’s low power requirements make it ideal for integration into mobile or autonomous robots. Moreover, a low cost of fabrication is obtained, especially when employing one or more of the methods disclosed herein, such that when robotic skin covering a large area is required, the low cost of fabrication will be highly beneficial.

[0042] According to yet another aspect of the invention a method for producing a sensor assembly is provided. The method comprises the step of providing a sensor material sheet comprising a plurality of sensor units, a plurality of bridging strips and a remainder of the sensor materialsheet, arranged such that the sensor units are separated from each other, and each bridging strip interconnects a sensor unit with the remainder of the sensor material sheet . The step of providing the sensor material sheet may comprise manufacturing the sensor material sheet, or shaping a provided sensor material sheet into a suitable configuration.

[0043] The sensor material sheet advantageously comprises piezoresistive material. Piezoresistive materials generally rely on incorporating conductive particles, often carbon -based, into a flexible or elastic matrix. The specific conductive particles may vary (e.g., carbon black, graphene, carbon nanotubes). The basic principle of such materials may be described as the conductive fillers forming conductive paths within the material, and when pressure is applied, the distance between these particles changes, which affects the material’s overall resistance. The sensor material sheet may comprise, be comprised in, or consist of any of the following materials:

[0044] a pressure sensitive polymeric foil impregnated with carbon black;

[0045] Velostat or Linqstat;

[0046] conductive textiles for flexible and wearable pressure sensors, such as Eeonyx Conductive Fabrics;

[0047] a flexible, pressure-sensitive material such as 3M Scotchlite;

[0048] a quantum tunnelling composite, being highly sensitive to pressure, such as Peratech QTC;

[0049] a conductive tape that changes resistance with pressure, such as Velcro Pressure- Sensitive Tape; and / or

[0050] conductive elastomers, being soft, flexible sensors, such as piezoresistive rubbers.

[0051] To facilitate orientation of the sensor material sheet in relation to other components, the sensor material sheet may be provided with orientation markings, marks or markers. Such orientation markings may be referred to as fiducial markers, and may be configured in any suitable way. In some examples, the fiducial markers are apertures extending through the sensor material sheet.

[0052] The method further comprises arranging a flexible adhesive sheet overlaying one side of the sensor material sheet, such that the provided sensor material sheet adheres to the flexible adhesive sheet. The flexible adhesive sheet may be provided as a prepared product, or it may be manufactured as a part of the method. The flexible adhesive sheet may comprise any suitable adhesive. The flexible adhesive sheet may comprise a polyethylene layer. To facilitate orientation of the flexible adhesive sheet in relation to other components, the flexible adhesive sheet may be provided with orientation markings, marks or markers. Suchorientation markings may be referred to as fiducial markers, and may be configured in any suitable way. In some examples, the fiducial markers are apertures extending through the flexible adhesive sheet.

[0053] After the flexible adhesive sheet has been arranged overlaying one side of the sensor material sheet, and the sensor material sheet has adhered sufficiently to the flexible adhesive sheet, the method comprises separating the remainder of the sensor material sheet from the adhesive sheet, causing each bridging strip to disengage from the sensor units, such that the sensor units remain on the adhesive sheet. In other words, when the adhesive sheet is removed from the sensor material sheet, or vice versa, the bridging strips brake and the sensor units remain stuck on the adhesive sheet.

[0054] When the sensor units have adhered to the flexible adhesive sheet, the method comprises arranging the adhesive sheet with the sensor units facing a flexible substrate with a plurality of electrodes disposed thereon. The electrodes are advantageously arranged in electrode pairs, each pair comprising a first electrode and a second electrode. The flexible substrate may be provided in any suitable way, such as by manufacturing a flexible circuit designed to fit the sensor assembly. Advantageously, electrodes are arranged on flexible substrate by printing the electrodes on the flexible substrate. The flexible substrate may comprise any suitable material, such as polyamide or PEEK.

[0055] Before joining the flexible adhesive sheet and the flexible substrate, the method comprises aligning each sensor unit with an associated first electrode and an associated second electrode . Prior to aligning each sensor unit with the associated first electrode and the associated second electrode, the method advantageously comprises assigning each sensor unit of the plurality of sensor units to a respective first electrode and second electrode. Each sensor unit is thus assigned to a respective first electrode and second electrode, such that each sensor unit is assigned to a specified electrode pair.

[0056] Thereafter, the sensor units are arranged in alignment with their respective assigned electrode pair. The alignment may be achieved in any suitable way. Advantageously, fiducial markers, or other indications of orientation, of the flexible adhesive sheet and the flexible substrate are aligned, whereby a required alignment between the sensor units and the electrode pairs is achieved. Such a manner of achieving the alignment is made possible through the relative positioning of the sensor units on the flexible adhesive sheet and the electrodes on the flexible substrate. The alignment may include aligning a respective centre point of each sensor unit with a respective centre point of each electrode pair.When the sensor units are satisfactorily aligned with the electrodes, the method comprises joining the adhesive sheet and the flexible substrate such that the adhesive sheet adheres to the flexible substrate. Thereby, the flexible adhesive sheet and the flexible substrate sandwich at least the plurality of sensor units and the plurality of electrodes therebetween. In other words, the plurality of sensor units and the plurality of electrodes are contained between the flexible adhesive sheet and the flexible substrate. Joining the adhesive sheet and the flexible substrate may comprise pressing the adhesive sheet and the flexible substrate together.

[0057] The manufacturing process disclosed herein achieves an improved efficiency compared to prior art manufacturing methods. The method achieves a precise assembly of the sensor assembly in a rational and efficient manner. In addition, with fewer components included in the sensor assembly, compared to prior art structures, there is less need for precise alignment or complex adhesion techniques; and the use of fewer materials leads to a lighter, thinner, and more compact sensor, lowering the risk of incorrect assembly as well as decreasing manufacturing costs.

[0058] In some examples, the step of providing the sensor material sheet comprises a step of cutting the sensor material sheet to produce a cut sensor material sheet comprising the plurality of sensor units, the plurality of bridging strips and the remainder of the sensor material sheet. In such examples, the sensor units are thereby separated from each other, and each bridging strip interconnects a sensor unit with the remainder of the sensor material sheet. Cutting the sensor material sheet to produce the plurality of sensor units may in turn comprise cutting a sensor array comprising at least four sensor units arranged in rows and columns. Cutting the sensor material sheet to produce the cut sensor material sheet may comprise laser cutting the sensor material sheet.

[0059] The flexible substrate advantageously comprises electrically conductive elements and, in such examples, the method may further comprise interconnecting the first and second electrodes associated with each sensor unit to enable sequentially measuring the electrical resistance of each sensor unit.

[0060] The method may further comprise a step of embedding a wireless transmitter in the flexible substrate, enabling data transfer from the sensor assembly.

[0061] The method may further comprise a step of providing apertures extending through the sensor assembly from a first surface of the sensor assembly to a second surface of the sensorassembly, such that the apertures intersect the flexible substrate and the flexible adhesive sheet. The apertures are advantageously provided through laser cutting the sensor assembly after the adhesive sheet and the flexible substrate have been joined together.

[0062] According to yet another aspect of the invention a method for producing a pressure sensing device using additive manufacturing to fuse the sensor assembly with at least an additive manufacturing material is provided.

[0063] The method comprises a step of printing at least a first layer of the additive manufacturing material. Any number of layers of the additive manufacturing material may be printed, depending on the design of the pressure sensing device.

[0064] Thereafter, the method comprises providing the sensor assembly as disclosed herein, wherein the sensor assembly comprises a plurality of apertures configured as through -holes through the sensor assembly. In other words, the method comprises providing a perforated sensor assembly, such as that disclosed herein. The sensor assembly is advantageously provided by producing such a sensor assembly according to the methods disclosed herein.

[0065] When the sensor assembly has been provided, the method comprises temporarily discontinuing the printing process to arrange the sensor assembly at a first surface of the first layer, such that a first side of the sensor assembly faces the first layer and a second, substantially opposite, side of the sensor assembly faces away from the first layer. In other words, the printing of the additive manufacturing material is paused, such that the sensor assembly may be arranged in contact with the printed layer. The sensor assembly may be said to rest against the first layer. The first surface of the sensor assembly may be arranged to face downward, toward the first layer, and the second surface may be arranged to face upward, away from the first layer. Depending on the configuration of the machinery used for the additive manufacturing, the sensor assembly may be arranged such that the first surface of the sensor assembly faces upward and the second surface faces downward. In some configurations, the sensor assembly may be tilted, or arranged at an incline.

[0066] When the sensor assembly has been arranged as desired, the method comprises continuing the printing process, such that additive manufacturing material is introduced into the apertures of the sensor assembly. The apertures are thus filled with additive manufacturing material. Thereby, the sensor assembly is fused, or integrated, with the additive manufacturing material. The additive manufacturing material printed in the apertures may be referred to as a second layer of additive manufacturing material.Optionally, the method comprises allowing the printing process to continue, such that the additive manufacturing material at least partly covers the second side of the sensor assembly. Thereby, at least one layer of additive manufacturing material is arranged on the second surface of the sensor assembly. Such a layer may be referred to as a third layer of additive manufacturing material. The pressure sensing device may thus be shaped through printing at least the third layer covering the sensor assembly, and any number of subsequent layers, as desired.

[0067] Advantageously, the method further comprises a step of incorporating other components within the additively manufactured pressure sensing device. Such a procedure allows for fusing the sensor assembly with layers such as a reinforcement or protective layers, to reinforce or protect the flexible substrate of the sensor assembly. Such a reinforcement improves the resistance of the sensor assembly to damage, such as tracks breaking when exposed to high levels of shear stress.

[0068] Alternatively, or additionally, the components may be electronic components, and / or additional sensors used for various purposes. Such components may be arranged at a printed layer of the additively manufactured pressure sensing device that was printed prior to arranging the sensor assembly. Such a layer may be referred to as a previous layer, or a lower layer. Alternatively or additionally, other components may be arranged at the same layer as the sensor assembly. Such a layer may also be referred to as a concurrent layer. Alternatively, or additionally, other components may be arranged at a subsequent, or upper, layer of the additively manufactured pressure sensor device, compared to the position of the sensor assembly.

[0069] Although additive manufacturing is an efficient method for shaping the pressure sensing device, other methods may be used to finalise the pressure sensing device, after the sensor assembly has been fused with the additive manufacturing material.

[0070] BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Embodiments of the invention shall now be described in detail by way of example and with reference to the accompanying drawings in which:

[0072] Figure 1 shows a schematic exploded view of a sensor assembly according to some embodiments / examples.Figures 2a, 2b and 2c show schematic views of electrodes according to some embodiments / examples.

[0073] Figures 3a and 3b show schematic views of a sensor assembly according to some embodiments / examples.

[0074] Figures 4a, 4b and 4c show schematic views of a sensor assembly according to some embodiments / examples.

[0075] Figures 5a and 5b show schematic views of a sensor assembly according to some embodiments / examples.

[0076] Figure 6 shows a schematic view of a piece of robotic skin according to some embodiments / examples.

[0077] Figures 7a-7h schematically illustrate steps of a method for producing a sensor assembly according to some embodiments / examples.

[0078] Figures 8a - 8d schematically illustrate steps of a method for producing a pressure sensing device according to some embodiments / examples.

[0079] DETAILED DESCRIPTION

[0080] Figure 1 shows a schematic exploded view of the sensor assembly 100 according to some embodiments / examples. Fig. 1 illustrates the sensor assembly 100; the plurality of sensor units 10; the first and a second electrodes 21, 22: the flexible adhesive sheet 3; and the flexible substrate 4.

[0081] As shown in Fig. 1, the sensor assembly 100 comprises a plurality of sensor units 10. Each sensor unit 101 is associated with a first electrode 21 and a second electrode 22. The first electrode 21 and the second electrode 22 are arranged at a first side 10a of the plurality of sensor units 10. The flexible adhesive sheet 3 is at least partly adhered to the plurality of sensor units 10 and is arranged at a second, substantially opposite, side 10b of the plurality of sensor units 10. The flexible substrate 4 is arranged at the first side 10a of the plurality of sensor units 10. The flexible substrate 4 comprises electrically conductive elements 41 (see Fig. 3a).

[0082] A first surface 101a of each sensor unit 101 of the plurality of sensor units 10 is arranged in electrical contact with the associated first electrode 21 and second electrode 22. The sensor units 10 are pressure sensors, preferably piezoresistive sensors, that change their respective electrical resistance when pressure is applied.Figures 2a, 2b and 2c show schematic views of electrodes according to some embodiments / examples. Figs. 2a-c illustrate the first electrode 21 and the second electrode 22 arranged in electrode pairs 20, each electrode pair 20 comprising a first electrode 21 and a second electrode 22. In some examples, each electrode pair 20 consists of a first electrode 21 and a second electrode 22.

[0083] In some examples, the first electrode 21 and the second electrode 22 are substantially coplanar. In other words, each electrode pair 20 is arranged in one plane, such that both the first electrode 21 and the second electrode 22 are arranged on the same plane.

[0084] In the examples shown in Figs. 2a and 2b, the first electrode 21 is concentric with the second electrode 22. In Fig. 2a, the first electrode 21 is arranged as an outer conductive circle and the second electrode 22 is arranged as an inner conductive circle. The outer conductive circle is arranged at a radial distance from the inner conductive circle, and encircles the inner conductive circle. In Fig. 2b, the first electrode 21 is arranged as an outer square and the second electrode 22 is arranged as an inner square. The sides of the outer conductive square are arranged offset from the sides of the inner conductive square, such that the outer square is arranged around, but spaced apart from, the inner square.

[0085] In the example shown in Fig. 2c, the first electrode 21 is not concentric with the second electrode 22. Instead, the first electrode 21 and the second electrode 22 comprise complementary extensions 21’, 22’, arranged adjacent each other, but at the same time spaced apart so that they are not physically connected.

[0086] Figures 3a and 3b show schematic views of the sensor assembly 100 according to some embodiments / examples. Figs. 3a and 3b illustrate the sensor array 1, comprising the plurality of sensor units 10 arranged in rows 11 and columns 12; and the electrode array 2 comprising a plurality of first electrodes 21 and second electrodes 22 arranged in rows 23 and columns 24. A pair comprising one first electrode 21 and one second electrode 22 may be referred to as an electrode pair 20.

[0087] The sensor assembly 100 may comprise the sensor array 1, as illustrated in Figs. 3a and 3b. In the sensor array 1, the plurality of sensor units 10 is arranged as a sensor array 1 comprising at least four sensor units 101 arranged in rows 11 and columns 12.

[0088] Of the plurality of first electrodes 21 and second electrodes 22, each first electrode 21 and second electrode 22 associated with a sensor unit 101 may be arranged in the electrode array2 comprising a plurality of rows 23 and a plurality of columns 24 corresponding to the sensor array 1. As illustrated in Figs. 3a-b, the first electrode 21 and second electrode 22 are substantially aligned with the associated sensor unit 101, enabling physical contact between the first surface 101a of the sensor unit 101 and both of the first electrode 21 and the second electrode 22. In other words, each electrode pair 20 is substantially aligned with the associated sensor unit 101, enabling physical contact between the first surface 101a of the sensor unit 101 and both of the first electrode 21 and the second electrode 22 of the electrode pair 20.

[0089] In the illustrated example in Fig. 3b, the first electrodes 21 in each row 23 of the electrode array 2 are electrically connected and the second electrodes 22 in each column 24 of the electrode array are electrically connected. In other examples, the first electrodes 21 in each column 24 of the electrode array 2 are electrically connected and the second electrodes 22 in each row 23 of the electrode array 2 are electrically connected.

[0090] Figures 4a, 4b and 4c show schematic views of the sensor assembly 100 according to some embodiments / examples. The elements of Figs. 4a-c are schematic representations of the components described below and are neither drawn to scale nor depicted in accurate relative sizes. Certain elements are exaggerated for intelligibility. Figs. 4a and 4b show a segment of the sensor assembly 100 comprising the electrode array 2, the flexible substrate 4, the first track 42, and the second track 43. Fig. 4c schematically illustrates the readout circuit 6.

[0091] In the illustrated example in Figs. 4a and 4b, the first track 42 connects at least two of the first electrodes 21, each associated with a respective sensor unit 101 (not shown in Figs. 4a-c). The second track 43 connects at least two of the second electrodes 22, each associated with a respective sensor unit 101.

[0092] In Fig. 4a, the first track 42 is arranged on a first surface 4a of the flexible substrate 4. The second track 43 is arranged on a second surface 4b of the flexible substrate 4. The electrode pairs 20, each comprising one first electrode 21 and one second electrode 22, are arranged on the first surface 4a of the flexible substrate. The first surface 4a is configured to be arranged facing the sensor units 10 (not shown in Figs. 4a-c) when the sensor assembly 100 is assembled. The first surface 4a may also be referred to as an upper, or top, surface of the flexible substrate 4. The second surface 4b may also be referred to as a lower, or bottom, surface of the flexible substrate 4. In Fig. 4a, the plurality of first tracks 42 are thus arranged on the same side of the flexible substrate 4 as the electrode pairs 20, while the plurality of second tracks 43 are arranged on the opposite side of the flexible substrate 4. The secondtracks 43 are connected to the second electrodes 22 by means of apertures, such as a plurality of vias 44, extending through at least one layer of the flexible substrate 4.

[0093] In Fig. 4b, both the plurality of first tracks 42 and the plurality of second tracks 43 are arranged on the second surface 4b of the flexible substrate 4. The electrode pairs 20 are arranged on the first surface 4a of the flexible substrate. The first surface 4a is configured to be arranged facing the sensor units 10 (not shown in Figs. 4a-c) when the sensor assembly 100 is assembled. In Fig. 4b, both the first tracks 42 and the second tracks 43 are thus arranged on the opposite side of the flexible substrate 4 to the electrode pairs 20. The second tracks 43 are connected to the second electrodes 22 by means of the plurality of vias 44, and the first tracks 42 are connected through a second plurality of vias 44’, extending through at least one layer of the flexible substrate 4.

[0094] Although illustrated as one layer, the flexible substrate may comprise a plurality of layers, wherein the second surface 4b illustrated in the examples may correspond to a second surface of one or more of the plurality of layers. The flexible substrate may, for example, comprise a bottom layer and a top layer. In such an example, the second surface 4b illustrated in the examples may correspond to a bottom surface of the top layer.

[0095] Advantageously, the flexible substrate 4 comprises a double sided or multi-layered flexible printed circuit board (FPCB) and / or at least one integrated circuit.

[0096] In some examples, the sensor assembly 100 comprises a readout circuit such as, or equivalent to, the readout circuit 6 illustrated in Fig. 4c. The readout circuit 6 may comprise any suitable components. In the illustrated example, the readout circuit 6 comprises at least one resistance measurement integrated circuit 61. The readout circuit 6 also comprises at least one microcontroller 62, at least one operational amplifier 63, at least one resistor 64 at least one multiplexer 65 and / or at least one wireless transmitter 66. Advantageously, the readout circuit 6 comprises at least two multiplexers 65.

[0097] Figures 5a and 5b show schematic views of the sensor assembly 100 according to some embodiments / examples. Figs. 5a and 5b show the sensor assembly 100, the plurality of apertures 110, the flexible adhesive sheet 3, and the flexible substrate 4.

[0098] In the illustrated example of Figs. 5a and 5b, the sensor assembly 100 comprises a plurality of apertures 110 arranged as through-holes extending from a first surface 100a of the sensor assembly 100 to a second surface 100b of the sensor assembly 100. The apertures 110 intersectthe flexible substrate 4 and the flexible adhesive sheet 3. The illustrated sensor assembly 100 may thus be referred to as a perforated sensor assembly 100.

[0099] The sensor assembly 100 may, in any example described herein, be described as a thin structure having a compact profile that makes it easily used in applications requiring curved surfaces. The thickness d of the sensor assembly 100 according to any example, and not limited to the example of Fig. 5b showing the example of a perforated sensor assembly 100, may be adapted to fit the circumstances at hand. In some examples the thickness d of the sensor assembly 100 is 0.3 to 1.5 mm, such that the minimum thickness is 0.3 mm, and the maximum thickness is 1.5 mm. In some examples, the thickness d ranges from (and includes) 0.5 mm up to and including 1 mm, or from (and including) 0.7 mm up to and including 1 mm. In some examples the thickness d is approximately 0.8 mm. The thickness d indicates the distance from an outer surface of the flexible adhesive sheet 3 to an outer surface of the flexible substrate 4, as can be seen in Fig. 5b.

[0100] Figure 6 shows a schematic view of a piece of robotic skin 300 according to some embodiments / examples. The robotic skin 300 comprises the sensor assembly 100 as disclosed herein. The sensor assembly 100 comprises the sensor array 1, arranged in rows 11 and columns 12, and the electrode array 2, arranged in rows 23 and columns 24. Each row 11, 23 and each column 12, 24 comprises individual sensor units 101 coupled to a respective electrode pair 20.

[0101] The sensor assembly 100 may be adapted to fit various designs of robotic skin 300. For example, the sensor assembly 100 may be modified in terms of size, shape, and flexibility. The grid structure of the sensor assembly 100, i.e. of the sensor array 1 and the electrode array 2, may be scaled to fit smaller, curved surfaces. In addition, the sensor units 10 and associated electrodes may be arranged in a way that allows them to conform to complex shapes like robotic limbs, joints, or fingers. Thus, the grid structure need not be of a fixed dimension, and the distances between rows and columns may be variable, and / or the number of sensor units 10 and electrode pairs 20 may differ between the various rows and columns. The placement, size, and number of sensor units 10 and corresponding electrode pairs 20 is advantageously selected based on the intended application. For example, when intended to be used in a robotic hand, it may be advantageous to have a higher density of the grid structure on the fingertips, and less dense in other places. A dense -to-sparse transition design may also be contemplated, to achieve highly sensitive areas and less sensitive areas. Density, when used herein, refers to the number of sensor units per area of robotic skin, so that the closer the sensor units are arranged, the higher the density of the grid structure.Depending on where and how to the robotic skin is intended to be placed on a robot, an additively manufactured layer, i.e., a 3D printed cover, may be used which can be of various designs. In some examples, Polydimethylsiloxane (PDMS) may be used to mimic skin. The 3D printed cover is advantageously designed to allow the sensor assembly to bend and to conform to the intended / desired shapes.

[0102] Figures 7a-7h schematically illustrate steps and variations of a method 1000 for producing a sensor assembly according to some embodiments / examples.

[0103] The method 1000 for producing a sensor assembly, such as, but not limited to, the sensor assembly 100 disclosed herein, comprises the steps as described in Fig. 7a. Steps may be taken in any suitable order. Dashed lines and boxes indicate optional steps. Examples of the features included in the method 1000 are illustrated in Figs. 7b-7h.

[0104] The method comprises the step of providing slOlO a sensor material sheet 120 comprising a plurality of sensor units 10, a plurality of bridging strips 121 and a remainder 122 of the sensor material sheet 120. The plurality of sensor units 10, plurality of bridging strips 121 and the remainder 122 of the sensor material sheet 120 are arranged such that each sensor unit 101 of the plurality of sensor units 10 are separated from each other, and each bridging strip 121 interconnects a sensor unit 101 with the remainder 122 of the sensor material sheet 120. The plurality of sensor units 10 may be the same plurality of sensor units as the plurality of sensor units 10 of the sensor assembly 100 as described above. However, other sensor units 10 may be suitable for use in the method 1000 for producing a sensor assembly.

[0105] The method 1000 further comprises arranging si 020 a flexible adhesive sheet 3, such as the flexible adhesive sheet 3 of the sensor assembly 100 described above, overlaying one side of the sensor material sheet 120, such that the sensor material sheet 120 adheres to the flexible adhesive sheet 3.

[0106] The method 1000 further comprises separating si 030 the remainder 122 of the sensor material sheet 120 from the adhesive sheet 3, causing each bridging strip 121 to disengage from the sensor units 10, such that the sensor units 10 remain on the adhesive sheet 3.

[0107] The method 1000 further comprises arranging sl050 the adhesive sheet 3 with the sensor units 10 facing a flexible substrate 4, such as the flexible substrate 4 of the sensor assembly 100 as described above, with a plurality of electrodes, such as the electrodes 20, 21, 22 of the sensorassembly 100 as described above, disposed thereon. The method suitably also comprises providing si 040 the flexible substrate 4, advantageously in the form of a flexible printed circuit board (FPCB).

[0108] The method 1000 further comprises aligning si 060 each sensor unit 101 with an associated first electrode 21 and an associated second electrode 22. The sensor unit 101 may be the same sensor unit as the sensor units 101 of the sensor assembly 100 as described above. The first electrode 21 and the second electrode 22 may be the same electrodes as the first electrode 21 and the second electrode 22 of the sensor assembly 100 as described above. However, other embodiments or types of the sensor unit 101 and / or the first electrode 21 and / or the second electrode 22 may also be suitable for use in the method 1000 for producing a sensor assembly. The sensor units 101 may be aligned with the associated electrodes by aligning si 063 fiducial markers on the flexible adhesive sheet 3 and flexible substrate 4.

[0109] The method 1000 further comprises joining sl070 the flexible adhesive sheet 3 and the flexible substrate 4 such that the flexible adhesive sheet 3 adheres to the flexible substrate 4, thereby sandwiching at least the plurality of sensor units 10 and the plurality of electrodes 20, 21, 22 therebetween. The adhesive sheet 3 and the flexible substrate 4 may be joined by pressing si 071 the adhesive sheet 3 and the flexible substrate 4 together.

[0110] The method 1000 may comprise assigning s 1061 each sensor unit 101 of the plurality of sensor units 10 to a respective first electrode 21 and second electrode 22, preferably prior to aligning si 005 each sensor unit 101 with the associated first electrode 21 and the associated second electrode 22.

[0111] The method 1000 may comprise a step of cutting slOll the sensor material sheet 120 to produce a cut sensor material sheet 120a comprising the plurality of sensor units 10, the plurality of bridging strips 121 and the remainder 122 of the sensor material sheet 120, such that the sensor units 10 are separated from each other, and each bridging strip 121 interconnects a sensor unit 101 with the remainder 122 of the sensor material sheet 120.

[0112] The step of cutting slOl 1 the sensor material sheet 120 to produce a cut sensor material sheet 120a may comprise laser cutting the sensor material sheet 120.

[0113] The step of cutting slOl 1 the sensor material sheet 120 to produce the plurality of sensor units 10 may comprise cutting a sensor array 1 comprising at least four sensor units 101 arranged in rows 11 of the sensor array 1 and columns 12 of the sensor array 1, such that each rowcomprises at least two sensor units 101 and each column comprises at least two sensor units 101, forming a 2x2 grid structure. The sensor array 1 may be the same sensor array as the sensor array 1 of the sensor assembly 100 as described above.

[0114] The method 1000 may further comprise arranging si 021 fiducial markers on the flexible adhesive sheet 3. The fiducial markers are suitably cut into the adhesive sheet 3, for example by laser cutting.

[0115] The flexible substrate 4 may comprise electrically conductive elements 41. In such examples, the method 1000 advantageously comprises interconnecting si 062 the first electrodes 21 and second electrodes 22 associated with each sensor unit 101 to enable sequentially measuring the electrical resistance of each sensor unit 101.

[0116] The sensor material sheet 120 advantageously comprises piezoresistive material.

[0117] The method 1000 may comprise a step of embedding si 041 a wireless transmitter 66 in the flexible substrate 4, enabling wireless data transfer from the sensor assembly.

[0118] The method 1000 may comprise a step of providing sl080 apertures 110 extending through the sensor assembly 100 from a first surface 100a of the sensor assembly 100 to a second surface 100b of the sensor assembly 100, such that the apertures 110 intersect the flexible substrate 4 and the flexible adhesive sheet 3. The apertures 110 are advantageously provided through laser cutting si 081 the sensor assembly 100 after the flexible adhesive sheet 3 and the flexible substrate 4 have been joined together.

[0119] Figures 7b-7h illustrate an example embodiment of the method 1000.

[0120] In Fig. 7b, the sensor material sheet 120 is shown in the form of a cut sensor material sheet 120a. The cut sensor material sheet 120a has been cut to achieve the bridging strips 121 connecting the cut-out sensor units 10 to the remainder 122 of the sensor material sheet 120. In other words, Fig. 7b illustrates the step of providing slOlO the sensor material sheet 120 comprising the plurality of sensor units 10, the plurality of bridging strips 121 and the remainder 122 of the sensor material sheet 120. As can be seen in Fig. 7b, the plurality of sensor units 10, plurality of bridging strips 121 and the remainder 122 of the sensor material sheet 120 are arranged such that all sensor units 101 of the plurality of sensor units 10 are separated from each other, and each bridging strip 121 interconnects a sensor unit 101 with the remainder 122 of the sensor material sheet 120. In the illustrated example, each sensorunit 101 is connected to the remainder 122 of the sensor material sheet 120 through one bridging strip 121. Depending on the circumstances at hand, more than one bridging strip 121 can be connected to each sensor unit 101.

[0121] Advantageously, the sensor units 10 and bridging strips 121 are cut from the sensor material sheet 120 through laser cutting the material sensor sheet 120. The sensor material sheet 120 may be any suitable sheet of sensor material, such as a piezoresistive sensor material. The sensor material sheet may be of any suitable size.

[0122] To facilitate aligning the sensor material sheet 120 with other components, such as an adhesive layer or sheet or a substrate, the sensor material sheet 120 may be provided with orientation marks. In the example of Fig. 7b, the sensor material sheet 120 is provided with fiducial markers 123, which may also be referred to as fiducials. The fiducial markers 123 are suitably achieved by laser cutting the sensor material sheet 120. However, any suitable orientation marks may be used, depending on the situation at hand.

[0123] The sensor material sheet 120 and the plurality of sensor units 10 may be the same or equivalent to the sensor material sheet 120 and the plurality of sensor units 10 of the sensor assembly 100 as described above.

[0124] In Fig. 7c, a flexible adhesive sheet 3 has been arranged sl020 overlaying one side of the sensor material sheet 120, so that the flexible adhesive sheet 3 has adhered to the sensor material 120. The flexible adhesive sheet 3 may be any suitable sheet of adhesive material. Fig. 7c shows a schematic top view, as seen from the side of the sensor material sheet 120, such that, in the figure, the flexible adhesive sheet 3 is arranged underneath the sensor material sheet 120.

[0125] The flexible adhesive sheet 3 may be the same, or an equivalent, flexible adhesive sheet as the flexible adhesive sheet 3 of the sensor assembly 100 described above.

[0126] To facilitate aligning the flexible adhesive sheet 3 with other components, such as a sensor material sheet or a substrate, the flexible adhesive sheet 3 may be provided with orientation marks. In the example of Fig. 7c, the flexible adhesive sheet 3 is provided with one or more fiducial markers 31. The fiducial markers 31 are suitably achieved by laser cutting the flexible adhesive sheet 3. However, any suitable orientation marks may be used, depending on the situation at hand.Fig. 7d shows a plan view of the flexible adhesive sheet 3 with the sensor units 10 arranged thereon, as seen from the same perspective as in Fig. 7c. Fig. 7d also shows the fiducial markers 31 of the flexible adhesive sheet 3.

[0127] In the illustrated example of Fig. 7d, the adhesive sheet 3 has been separated sl030 from the remainder 122 of the sensor material sheet 120. When the adhesive sheet 3 is removed, or pulled off, from the sensor material sheet 120, the bridging strips 121 disengage from the sensor units 10, and only the sensor units 10 remain on the adhesive sheet 3. In other words, when the adhesive sheet 3 is pulled off from the sensor material sheet 120, the bridging strips break and the sensor units 10 remain stuck on the adhesive sheet 3. The adhesion between the sensor units and the adhesive sheet is thus stronger than the connection between the bridging strips 121 and the sensor units. However, the adhesion between the flexible sheet and sensor material sheet cannot be so strong that it prevents separating the flexible adhesive sheet 3 from the sensor material sheet 120. Thus, the adhesive force exerted by the flexible adhesive sheet 3 needs to be strong enough to disengage the sensor units from the bridging strips, while still allowing the sensor material sheet 120 to be separated from the flexible adhesive sheet 3.

[0128] Fig. 7e shows a plan view of a flexible substrate 4, with apertures 40, electrodes 20 / 21 / 22, and fiducial markers 45 arranged thereon. The flexible substrate 4 may be an FPCB.

[0129] In the illustrated example of Fig. 7e, the flexible substrate 4 has been provided sl040, in the form of a substrate panel 4’ comprising a plurality of sub-units 46. Each sub-unit 46 comprises electrodes 20, 21, 22, and apertures 40. The flexible substrate 4 may be provided sl040 by manufacturing the flexible substrate panel 4’, which may be an FPCB panel, with multiple sub-units 46, where each sub-unit 46 is separated at least partly from a remainder 47 of flexible substrate panel 4’. The sub-units 46 may also be referred to as substrate mats. In some examples, however, the flexible substrate 4 does not comprise sub-units but is instead arranged as one unit comprising a plurality of electrodes 20,21,22 and, optionally, apertures 40.

[0130] The flexible substrate 4 comprises a plurality of electrodes, such as the electrodes 20, 21, 22 of the sensor assembly 100 as described above, arranged thereon. The electrodes 20, 21, 22 are advantageously printed on the flexible substrate 4.

[0131] Fig. 7f shows a plan view of the flexible adhesive sheet 3 overlaying the flexible substrate 4. In Fig. 7f, the adhesive sheet 3 has been arranged s!050 with the sensor units 10 facing theflexible substrate 4. Each sensor unit 101 has been aligned si 060 with an associated first electrode 21 and an associated second electrode 22. A first electrode 21 and a second electrode 22 may together be referred to as an electrode pair 20. Each sensor unit 101 may be aligned with an associated electrode pair 20 in any suitable way. Advantageously, the fiducial markers 31 of the flexible adhesive sheet 3 and the fiducial markers 45 of the flexible substrate 4, or of the flexible substrate panel 4’, are used to align the sensor units 10 with the electrode pairs 20. When joined si 070, the flexible adhesive sheet 3 adheres to the flexible substrate 4, or the flexible substrate panel 4’, thereby sandwiching at least the plurality of sensor units 10 and the plurality of electrodes 20, 21, 22 therebetween. Thereby, a sensor assembly such as the sensor assembly 100 has been achieved.

[0132] In examples where the flexible substrate panel 4’ is joined with the flexible adhesive sheet 3, comprising the sensor units, a sensor assembly panel 100’ is achieved. The sensor assembly panel 100’ may then be cut into multiple sensor assemblies 100, in some examples corresponding to the sub-units 46 of the flexible substrate panel 4’. Alternatively, or additionally, the sensor assembly panel 100’ may be used as a panel or a combination of modular units, comprising multiple sensor assemblies 100.

[0133] In Fig. 7g, multiple sensor assemblies 100 have been separated from a remainder 100” of the sensor assembly panel 100’. Advantageously, the multiple sensor assemblies 100 have been cut out from the sensor assembly panel 100’, for example by laser cutting. Each sensor assembly 100 may in such examples be referred to as a sensor module, or sensor mat. Each sensor assembly 100 comprises embedded sensor units 10. In the illustrated example, the sensor assembly panel 100’ has been cut into four sensor assemblies 100. However, any suitable number of sensor assemblies 100 may be cut from the sensor assembly panel 100’. Advantageously, the sensor assemblies 100 comprise the plurality of apertures 110, arranged as through-holes 5, extending from the first surface 100a of the sensor assembly to the second surface 100b of the sensor assembly. The cut apertures 110 suitably align with any pre-cut apertures 40 of the flexible substrate 4.

[0134] In Fig. 7h, the remainder 100” of the sensor assembly panel 100’ has been separated from the sensor assemblies 100. The sensor assemblies 100 may then be arranged or used as desired, in combination or separately. Each sensor assembly 100 advantageously comprises the through-holes 5, extending through the sensor assembly 100.

[0135] Figures 8a to 8d schematically illustrate steps of a method 2000 for producing a pressure sensing device 200, such as the robotic skin 300, according to some embodiments / examples.The method 2000 for producing the pressure sensing device 200, such as, but not limited to, the robotic skin 300 disclosed herein, comprises the steps as described in Fig. 8a. Steps may be taken in any suitable order. Dashed lines and boxes indicate optional steps. Examples of the features included in the method 2000 are illustrated in Figs. 8b-8d.

[0136] The method 2000 for producing the pressure sensing device 200 uses additive manufacturing to fuse the sensor assembly 100 with at least one additive manufacturing material. The method 2000 comprises the step of printing s2010 at least a first layer 401 of the additive manufacturing material. The method 2000 further comprises providing s2020 the sensor assembly 100 as disclosed herein, wherein the sensor assembly 100 comprises a plurality of apertures 110 configured as through-holes 5 through the sensor assembly 100. Such a sensor assembly may be referred to as a perforated sensor assembly. The sensor assembly 100 is advantageously provided by producing a sensor assembly according to the method 1000 for producing a sensor assembly, as described above.

[0137] The method 2000 further comprises the step of temporarily discontinuing s2030 the printing process to arrange the sensor assembly 100 at a first surface 401a of the first layer 401 (see Fig. 8b), such that the first surface 100a of the sensor assembly 100 faces the first layer 401 and the second surface 100b, which is substantially opposite of the first surface 100a, of the sensor assembly 100 faces away from the first layer 401 (see Fig. 8c).

[0138] The method 2000 further comprises the step of continuing s2040 the printing process, such that the additive manufacturing material is introduced into the apertures 110 of the sensor assembly 100.

[0139] Optionally, the method 2000 comprises allowing s2050 the printing process to continue, such that the additive manufacturing material at least partly covers the second surface 100b of the sensor assembly 100 (see Fig. 8d).

[0140] The method 2000 for producing the pressure sensing device 200 may further comprise a step of incorporating s2060 other components within the additively manufactured pressure sensor device 200.

[0141] In examples where the pressure sensing device 200 is a piece of robotic skin, there are several ways to achieve the final product, depending on the intended use of the robotic skin. The method 2000 may be used to produce a plurality of modular units with wireless connectivity,which are then connected using any suitable means. In some examples, a modular unit of the sensor assembly 100 comprising three rows and three columns, which may be referred to as a 3X3 design, may be used, where each 3X3 matrix is intended to cover a small and curved area. The connection to the grid of the sensor assembly may then be extended and the modular units jointed together to form a 6X6 grid.

[0142] Since robotic skin often requires a flexible construction, flexible interconnections are suitably employed, for example by using flexible FPC cables of a suitable length. Such flexible interconnections are suitably configured and / or arranged within the body of the main sensor assembly 100, to route the connections out from the sensor assembly 100. Alternatively, or additionally, direct joints may be used, without the need for intermediate connectors and / or additional wiring.

[0143] Figures 8b-8d illustrate an example embodiment of the method 2000.

[0144] In Fig. 8b, a suitable number of layers 401, 402, 403 of additive manufacturing material 400, also referred to as 3D-printing material, are printed. In the method 2000 for producing the pressure sensing device 200 disclosed herein, at least a first layer 401 is printed s2010. Thereafter, i.e., when a suitable number of layers has been printed, the printing is temporarily discontinued s2030.

[0145] In Fig. 8c, the sensor assembly 100 with apertures 110, i.e., a perforated sensor assembly 100, has been provided s2020. The sensor assembly 100 has been arranged at the first surface 401a of the first layer 401, such that the first surface 100a of the sensor assembly 100 faces the first layer 401 and the second surface 100b of the sensor assembly 100 faces away from the first layer 401. In the illustrated example, the first surface 100a of the sensor assembly 100 faces downward, toward the first layer 401, and the second surface 100b faces upward, away from the first layer 401. Depending on the configuration of the machinery used for the additive manufacturing, i.e., the configuration of the 3D printer, the sensor assembly may be arranged such that the first surface 100a of the sensor assembly 100 faces upward and the second surface 100b faces downward. In some configurations, the sensor assembly 100 may be tilted, or arranged at an incline.

[0146] When the sensor assembly 100 has been arranged as desired, the printing process continues s2040, such that the additive manufacturing material 400 is introduced into the apertures 110 of the sensor assembly 100. In other words, the apertures 110 of the sensor assembly 100 are filled with additive manufacturing material 400. Thereby, the sensor assembly 100 is fused,or integrated, with the additive manufacturing material 400. In the method 2000 for producing the pressure sensing device 200 disclosed herein, the additive manufacturing material 400 printed in the apertures may be referred to as a second layer 402 of additive manufacturing material 400. In other words, at least the first layer 401 of an additively manufactured product is achieved, whereafter the sensor assembly 100 is arranged in contact with the first layer 401 and the second layer 402 fills the apertures 110 of the sensor assembly 100. Thereby the pressure sensing device 200 is achieved.

[0147] In Fig. 8d, a subsequent layer has been printed on top of the sensor assembly 100. In the method 2000 for producing the pressure sensing device 200 disclosed herein, the subsequent layer may be referred to as a third layer 403 of additive manufacturing material 400. In the illustrated example, the printing process has thus been allowed s2050 to continue, such that the additive manufacturing material 400 at least partly covers the second surface 100b of the sensor assembly 100. The pressure sensing device 200 may thereafter be further shaped through printing additional layers covering the sensor assembly 100. Additional sensor assemblies 100 and / or other suitable components may also be incorporated s2060 into the additively manufactured pressure sensing device 200.

[0148] In some examples, the method for producing the pressure sensor device 200 may be used to shape the robotic skin 300.

Claims

CLAIMS1. A method for producing a sensor assembly, comprising the steps of:providing a sensor material sheet comprising a plurality of sensor units, a plurality of bridging strips and a remainder of the sensor material sheet, arranged such that the sensor units are separated from each other and each bridging strip interconnects a sensor unit with the remainder of the sensor material sheet;arranging a flexible adhesive sheet overlaying one side of the sensor material sheet, such that the sensor material sheet adheres to the flexible adhesive sheet; separating the remainder of the sensor material sheet from the adhesive sheet, causing each bridging strip to disengage from the sensor units, such that the sensor units remain on the adhesive sheet;arranging the adhesive sheet with the sensor units facing a flexible substrate with a plurality of electrodes disposed thereon;aligning each sensor unit with an associated first electrode and an associated second electrode; andjoining the adhesive sheet and the flexible substrate such that the adhesive sheet adheres to the flexible substrate, thereby sandwiching at least the plurality of sensor units and the plurality of electrodes therebetween.

2. The method according to claim 1, wherein the method further comprises assigning each sensor unit of the plurality of sensor units to a respective first electrode and second electrode, preferably prior to aligning each sensor unit with the associated first electrode and the associated second electrode.

3. The method according to claim 1 or 2, further comprising a step of cutting the sensor material sheet to produce a cut sensor material sheet comprising the plurality of sensor units, the plurality of bridging strips and the remainder of the sensor material sheet, such that the sensor units are separated from each other, and each bridging strip interconnects a sensor unit with the remainder of the sensor material sheet.

4. The method according to claim 3, wherein the step of cutting the sensor material sheet to produce a cut sensor material sheet comprises laser cutting the sensor material sheet.

5. The method according to claim 3 or 4, wherein the step of cutting the sensor material sheet to produce the plurality of sensor units comprises cutting a sensor array comprising at least four sensor units arranged in rows and columns.

6. The method according to any of claims 1 to 5, wherein the flexible substrate comprises electrically conductive elements and the method further comprises interconnecting the first and second electrodes associated with each sensor unit to enable sequentially measuring the electrical resistance of each sensor unit.

7. The method according to any of claims 1 to 6, wherein the sensor material sheet comprises piezoresistive material.

8. The method according to any of claims 1 to 7, further comprising a step of embedding a wireless transmitter in the flexible substrate, enabling data transfer from the sensor assembly.

9. The method according to any of claims 1 to 8, further comprising a step of providing apertures extending through the sensor assembly from a first surface of the sensor assembly to a second surface of the sensor assembly, such that the apertures intersect the flexible substrate and the flexible adhesive sheet, wherein the apertures are preferably provided through laser cutting the sensor assembly after the adhesive sheet and the flexible substrate have been joined together.

10. A method for producing a pressure sensing device using additive manufacturing to fuse a sensor assembly comprising a plurality of apertures configured as through-holes through the sensor assembly, preferably the sensor assembly according to claim 21, with at least an additive manufacturing material, the method comprising the steps of:printing at least a first layer of the additive manufacturing material; providing the sensor assembly, preferably by producing a sensor assembly according to the method of claim 9;temporarily discontinuing the printing process to arrange the sensor assembly at a first surface of the first layer of additive manufacturing material, such that a first side of the sensor assembly faces the first layer of additive manufacturing material and a second, substantially opposite, side of the sensor assembly faces away from the first layer of additive manufacturing material;continuing the printing process, such that the additive manufacturing material is introduced into the apertures of the sensor assembly; andoptionally allowing the printing process to continue, such that the additive manufacturing material at least partly covers the second side of the sensor assembly.

11. The method of claim 10, further comprising a step of incorporating other components within the additively manufactured pressure sensor device.

12. A sensor assembly comprising:a plurality of sensor units, each sensor unit associated with a first and a second electrode arranged at a first side thereof;a flexible adhesive sheet, at least partly adhered to the plurality of sensor units and arranged at a second, substantially opposite, side of the plurality of sensor units; anda flexible substrate comprising electrically conductive elements, arranged at the first side of the plurality of sensor units;wherein a first surface of each of the plurality of sensor units is arranged in electrical contact with the associated first and the second electrode, and the sensor units are pressure sensors, preferably piezoresistive sensors, changing their respective electrical resistance when pressure is applied.

13. The sensor assembly according to claim 12, wherein the plurality of sensor units is arranged as a sensor array comprising at least four sensor units arranged in rows and columns.

14. The sensor assembly according to claim 13, wherein each first and second electrode associated with a sensor unit is arranged in an electrode array comprising rows and columns corresponding to the sensor array, such that the first and second electrode are substantially aligned with the associated sensor unit, enabling physical contact between the first surface of the sensor unit and both of the first electrode and the second electrode.

15. The sensor assembly according to claim 14, wherein:the first electrodes in each row of the electrode array are electrically connected and the second electrodes in each column of the electrode array are electrically connected; orthe first electrodes in each column of the electrode array are electrically connected and the second electrodes in each row of the electrode array are electrically connected.

16. The sensor assembly according to any of claims 12 to 15, wherein the first and second electrodes are substantially coplanar.

17. The sensor assembly according to any of claims 12 to 16, wherein a first track connects at least two of the first electrodes, each associated with a respective sensor unit, and a second track connects at least two of the second electrodes, each associated with a respective sensor unit.

18. The sensor assembly according to claim 17, wherein the first track is arranged on a first surface of the flexible substrate and the second track is arranged on a second surface of the flexible substrate.

19. The sensor assembly according to any of claims 12 to 18, wherein the flexible substrate comprises a double sided or multi-layered flexible printed circuit board (FPCB) and / or at least one integrated circuit.

20. The sensor assembly according to any of claims 12 to 19, further comprising a readout circuit, wherein the readout circuit comprises at least one of each of the following: - a resistance measurement integrated circuit;- a micro-controller;- an operational amplifier;- a resistor;- a multiplexer; and- a wireless transmitter.

21. The sensor assembly according to any of claims 12 to 20, wherein the sensor assembly comprises a plurality of apertures arranged as through -holes extending from a first surface of the sensor assembly to a second surface of the sensor assembly and intersecting the flexible substrate and the flexible adhesive sheet.

22. Robotic skin comprising the sensor assembly according to any of claims 12 - 21.

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