High-resistance sensor and method for using same

A high-resistance sensor. The sensor includes a first low-resistance material and a second low-resistance material, each connected with a base material. The first low-resistance material and the second low-resistance material are separated by a gap. A stimulus causes the first low-resistance material and the second low-resistance to move toward each other. A high-resistance material is positioned within the gap intermediate the first low-resistance material and the second low-resistance material. The high-resistance material increases the resistance of a circuit formed by contact between the first low-resistance material and the second low-resistance material when the sensor is subject to the stimulus.

FIELD

The present disclosure relates to a high-resistance sensor and a method of using the sensor.

BACKGROUND

Sensors that measure applied force have a multitude of uses. A force-sensitive sensor may be used in systems for measurement of pressure on an individual, such as in a shoe or a on a hospital mattress. Many such force sensor systems measure changes in electrical characteristics, such as resistance, of the sensor upon application of the force.

SUMMARY

Herein provided is a high-resistance sensor. The sensor includes separate conductors or other low-resistance material separated by a gap. A first high-resistance material is positioned within the gap intermediate the separate low-resistance materials. When a stimulus is applied to the sensor, the low-resistance materials each contact the high-resistance material, forming a circuit that includes the high-resistance material. The stimulus may be a force, in which case a base material on which the high-resistance materials are bonded or otherwise affixed may flex, directing the low-resistance materials into the gap and forming a circuit including the high-resistance material and both low-resistance materials. In other cases, the stimulus may be temperature or any other suitable input that may drive the low-resistance materials and any base material to flex or otherwise move toward each other. Including the high-resistance material may provide advantages in terms of power efficiency of the sensor, resolution, and accuracy.

In a first aspect, herein provided is a high-resistance sensor. The sensor includes a first low-resistance material and a second low-resistance material, each connected with a base material. The first low-resistance material and the second low-resistance material are separated by a gap. A stimulus causes the first low-resistance material and the second low-resistance to move toward each other. A high-resistance material is positioned within the gap intermediate the first low-resistance material and the second low-resistance material. The high-resistance material increases the resistance of a circuit formed by contact between the first low-resistance material and the second low-resistance material when the sensor is subject to the stimulus.

In a further aspect, herein provided is a sensor including: a first base material; a second base material; a first low-resistance material connected with the second base material; a second low-resistance material connected with the second base material and separated from the first low-resistance material by a gap for flexing toward low-resistance material under a stimulus; and a first high-resistance material positioned within the gap intermediate the first low-resistance material and the second low-resistance material for increasing the resistance of a circuit formed by the first low-resistance material and the second low-resistance material when the sensor is subjected to the stimulus.

In some embodiments, the first base material is flexible and the stimulus includes force.

In some embodiments, the first base material is deformable in response to changes in temperature and the stimulus includes a change in temperature.

In some embodiments, the first low-resistance material is connected with the first base material in a first pattern; the second low-resistance material is connected with the second base material in a second pattern; and the first pattern and the second pattern do not overlap.

In some embodiments, the gap is filled with a fluid.

In some embodiments, the gap is vacuum sealed. In some embodiments, the stimulus is tension.

In some embodiments, the first high-resistance material is bonded with the first low-resistance material.

In some embodiments, the sensor further includes a second high-resistance material. In some embodiments, the first high-resistance material and the second high-resistance material are in constant contact and the gap is substantially minimal. In some embodiments, the circuit is formed by contact between the first high-resistance material and the second high-resistance material.

In some embodiments, the sensor further includes a protective material for reducing permeation of fluids into the sensor.

In some embodiments, the sensor further includes a material adjacent the first base material for directing the stimulus.

In some embodiments, the first high-resistance material is located within the gap and the gap is defined both between the first high-resistance material and the first low-resistance material.

In a further aspect, herein provided is a method of sensing a stimulus including: providing a first low-resistance material separated from a second low-resistance material by a gap; providing a first high-resistance material intermediate the first low-resistance material and the second low-resistance material within the gap; applying a stimulus to the first low-resistance material and the second low-resistance material for closing the gap between the first low-resistance material and the second low-resistance material to create a circuit including the first low-resistance material, the second low-resistance material and the first high-resistance material; and measuring a change in electrical properties of the circuit as a result of the stimulus.

In some embodiments, the stimulus includes force.

In some embodiments, the stimulus includes a change in temperature.

In some embodiments, the method further includes a second high-resistance material where the first high-resistance material and the second high-resistance material are in constant contact and the gap is substantially minimal.

In some embodiments, the method further includes a protective layer.

In some embodiments, the method further includes a base material bonded to the first high-resistance material and includes a material adjacent to the base material for directing the stimulus.

DETAILED DESCRIPTION

Generally, the present disclosure provides a high-resistance sensor. A combination of high-resistance and low-resistance materials provide a path through which electrical current may flow upon application of an external stimulus to the sensor. The sensor may detect changes in an electrical property of material in the sensor (e.g. resistance, conductance, capacitance, inductance, etc.).

Previous systems for measuring changes in force, and the signals provided by such systems, may be affected by electrical resistance of traces that define electrical leads in the system. Differences between trace resistances at different portions of the sensor, or differences from one reading to the next, may result in measurable changes to the resistance of the electrical circuit material. Changes to the trace resistances may result in calibration drift and corresponding changes to the signal detected by the sensor. Previous systems including only low-resistance sensors may drain more electrical current than a system that incorporates a high-resistance sensor. In addition to consuming more power, systems requiring a larger current draw may be subjected to more noticeable cross-channel effects, which may also result in errors in reported measurements. Cross-channel effects may result in signal noise from inductive and capacitive events occurring between nearby conducting traces. Cross-channel effects may result in errors in reported measurements.

Herein provided is a high-resistance sensor including two conductive layers separated by a gap. The two conductive layers may be urged into contact with each other under applied force or may be urged into more intimate contact if already in contact. Each of the conductive layers includes a low-resistance material (e.g. copper, silver, gold, copper, conductive ink, etc.) and an insulating base material. A first layer includes a first base material and a first low-resistance material. A second layer includes a second base material and a second low-resistance material. The first base material may be made of a different material than the second base material. The first low-resistance material may be made of a different material than the second low-resistance. A high-resistance material (e.g. conductive materials, semi-conductive materials, piezoelectric materials, piezoresistive materials, force-sensing materials, force-sensing resistors, force-resistive inks, etc.) is positioned between the two low-resistance materials. The low-resistance material may be traced on, bonded to or otherwise connected with the base material. The high-resistance material may be held in place by friction, traced on, bonded to or otherwise connected to the low-resistance material and/or the base material. Under applied force, the two low-resistance materials are urged toward each other, and the high-resistance material between the two low-resistance materials provides a high-resistance path for a signal resulting in electrical communication between the two conductive layers.

The low-resistance material may be traced, applied or otherwise patterned on each of the two insulating base material layers in an offset pattern such that overlapping portions of the layers lacking any low-resistance material are defined. Void spaces that lack low-resistance material over a portion of the sensor across both of the conductive layers force flow of current between the low-resistance material on the two conductive layers to be directed through the high-resistance material when the two conductive layers are forced into contact with each other.

The high-resistance material in the circuit between the first and second low-resistance materials of the sensor may mitigate the effects on sensor signal of stray impedances and changes in lead resistance. Mitigating these effects may increase sensitivity of the sensor to changes in resistance or other electrical properties of a circuit including both low-resistance materials. The high-resistance sensors may also mitigate sensor hysteresis and increase resolution of the sensor across a range of applied forces.

FIG.1shows a block diagram of a detection system50where the detection system includes a sensor system10and transmission module54powered by a power source5. The sensor system10is in electronic communication with the transmission module54and the transmission module54transmits data56to a computing device60. The computing device60processes the data56, which may then be displayed, communicated to a user, stored and optionally fed back to the transmission module54. The transmission device may transmit the data56via cables or wirelessly to the computing device60. The power source5may be a battery that powers the sensor system10and the transmission module54. The power source5may be a battery that powers the sensor system10and the transmission module54. Current from the power source5may be sent through the sensor system10and the resulting output current can be read to determine a resistance from an associated stimulus change for example, such as described in international patent application PCT/CA2019/050229 to Viberg et al.

FIG.2shows a sensor system10including a first layer30and a second layer40with the first high-resistance material, the second high-resistance material and spacer are not shown. The sensor system10includes a plurality of sensors20disposed on a base material12. The base material12may be manufactured from any suitable flexible insulating material (e.g. polyethylene terephthalate glycol modified, polyimide, polyester, etc.) or any other dimensionally stable, printable electrical insulating material that can bend and deform upon application of force or other stimulus. The sensors20are connected with each other by first traces13and second traces14. The first traces13and the second traces14may be prepared from low-resistance material (e.g. copper, silver, gold, copper, conductive ink, temperature resistive ink, etc.). The sensors20may be disposed in an array that allows for individual addressing using a row and column addressing scheme (not shown) or they may be configured in parallel within the sensor system10.FIG.2shows a 2 by 1 array of sensors20under the layers of base material12and protective material18. The sensors20are connected in the first layer in a row via first trace13and in a column in the second layer via a ‘Y’ shaped second trace14. The first traces13and the second traces14are connected with an output interface16for providing data externally to the sensor system10. A protective material18may be applied to the base material12for protecting the base material12, the first high-resistance material (not shown), the second high-resistance material (not shown), the spacers (not shown), the sensors20, the first traces13and the second traces14. The protective material18may be applied to one or both surfaces of the sensor system10. The protective material18may encompass the entire sensor system10or a portion thereof. The protective material18may be constructed of metal such as aluminum or any other suitable material that reduces the permeation of gases and/or fluids to and from the sensor system10. The protective material18may be foil laminated or foil applied by evaporated deposition and the sensor system10may be vacuumed before sealing. The protective material18may alternately be manufactured of carbon fiber or Kevlar® or any material for protecting the sensors from damage due to excessive high pressure, creasing, bending.

FIG.3shows a cross-sectional view of a sensor20along the axis3-3ofFIG.2.FIG.3shows the first high resistance material34(not shown inFIG.2), the second high resistance layer44(not shown inFIG.2) and the spacer24(not shown inFIG.2) on the periphery of the sensor20.FIG.3shows the first layer30including the base material12and the first low-resistance material32with a connected first high-resistance material34. The second layer40includes the base material12and the second low-resistance material42and it has a connected second high-resistance material44. The spacer24on the periphery of the sensor20is disposed between the two layers of base material12. There is a gap22between the first high resistance material34and the second high-resistance material44. The protective material18protects the outer layers of base material12. In this embodiment, the first low-resistance materials32and the second low-resistance materials42do not overlap in the vertical plane of the sensor20.

InFIG.4, the sensor20ofFIG.3has been subjected to a force F, placing the first high-resistance material34in contact with the second high-resistance material44, closing a circuit and generating a signal to be output at the output interface16(seeFIG.2). A similar effect may result from the urging of the first layer toward the second layer due to dimensional changes effected by a change in temperature. For example, an increase in temperature may cause a differential expansion of the elements of the sensor system10, which may lead to deformation of the sensor system10(the low-resistance material used in the low resistance trace may expand more than other materials in the sensor system10). The protective material18may surround the sensor system10on both sides, isolating the sensor20and the base material12from the external environment, or may be on one side only of the sensor package10. Each sensor20includes a first layer30and a second layer40. Both the first layer30and the second layer40include the base material12. The first layer30is in electrical communication with the first traces13and the second layer40is in electrical communication with the second traces14. The first layer30is separated from the second layer40by a gap22. The gap22may be filled with air and open to the atmosphere, or may be a closed environment including a fluid (e.g. air, nitrogen, gas, water, oil, gel, etc.) or any other compressible substance (e.g. foam, etc.).

The gap22is maintained by a spacer24. The spacer24may be a dielectric or another insulating material to prevent electrical contact between the first layer30and the second layer40. The spacer24may also include adhesive material to bond the base material to the second layer of base material or any adhesive material used to bond any of the layer elements to each other. The spacer24prevents the first layer30from coming into contact with the second layer40when the sensor system10is not subjected to an applied force, a temperature change or other effect that urges the first layer30toward the second layer40. Upon application of a force, temperature change or other effect to the sensor system10, the first layer30and the second layer40flex toward each other. When the first layer30and the second layer40flex toward each other sufficiently to come into contact across the gap22, then a circuit including the first layer30and the second layer40is completed. As a result, upon application of force or another stimulus to the sensor20, the first layer30may come into contact with the second layer40through the gap22, and changes the electrical characteristics of the sensor20for generating a signal.

The first layer30includes a first low-resistance material32and a first high-resistance material34. The second layer40includes a second low-resistance material42and a second high-resistance material44. The first low-resistance material32is patterned on the base material12such that first low-resistance material32does not overlap with the second low-resistance material42. The first low-resistance material32and the second low-resistance material42may be any suitable low-resistance material (e.g. copper, silver, gold, copper, conductive ink, etc.). The first high-resistance material34and the second high-resistive material44may include any suitable conductive material that has a higher resistance than each of the first low-resistance material32and the second low-resistance material42(e.g. piezoelectric materials, piezoresistive materials, force-sensing materials, force-sensing resistors, force-resistive inks, etc.).

FIG.5shows the sensor20of the sensor system10with the first high-resistance material34and the second high-resistance material44removed for the purpose of illustrating the offset nature of the conductive layers. This figure shows an increased resistance sensor20where the non-overlap of the low-resistance conductive layers creates an even higher resistance between opposing first layer30and second layer40. This design urges the current to flow vertically through the first layer30, laterally through the high-resistance material (not shown) and then vertically through the second layer40, which is a more resistive path than a path flowing vertically through sensor20. The honeycomb configuration is an example of the offset pattern of the first low-resistance material32of the first layer30shown in black hexagon outlines. The first low-resistance material32is connected to the first trace13. The second low-resistance material42of the second layer40is show in striped hexagon shapes and is connected to the second trace14. The white area in between the hexagon shapes and the hexagon outlines is the offset pattern formed by the low-resistance materials. The high-resistance material (not shown) is disposed in between the first layer30and the second layer40.

FIG.6shows a top cutaway view of another embodiment of a sensor120in accordance with the present disclosure. For clarity purposes,FIG.6does not show the high-resistance material. In this embodiment, the sensor120includes the first layer130and the second layer140distributed on the base material112. The first layer130and the second layer140have a different tracing pattern than the first layer30and the second layer40of the sensor20ofFIG.5. The low-resistance material of the first layer130and the second layer140are offset in an alternating striped pattern. The first low-resistance material132is connected to the first trace113and the second low-resistance material142is connected to the second trace114. The white area in between the stripes formed by low-resistive material is the offset of the trace patterns. Similarly to the sensor20, upon application of pressure, temperature change or other suitable stimulus, the first layer130contacts the second layer140to form a circuit. The circuit also includes one or more high-resistance layers (not shown).

FIG.7shows an embodiment of a schematic of a footfall detection system250in accordance with the present disclosure. The footfall detection system250includes a sensor system210in a shoe252. The sensor system210may be included over, under or within an insole, orthotic or other insert, affixed temporarily or permanently to the shoe252or otherwise integrated into the footfall detection system250. The sensor system210may alternately be located outside of footware and be arranged on the floor or integrated into a mat in other footfall detection systems250. The sensor system210is in electronic communication with a transmission module254. The sensor system210and the transmission module254are powered by a power source (205inFIG.8). The transmission module254transmits data256to a computing device260(e.g. laptop computer, smart watch, smartphone, tablet, cloud-based server, etc.). The computing device260includes a processing module262for processing the data256. Processed data may be displayed or otherwise communicated to a user via a communication module266, stored in a storage module264or both.

FIG.8shows a block diagram of the footfall detection system250ofFIG.7. The footfall detection system250includes a sensor system210and transmission module254powered by the power source205. The sensor system210is in electronic communication with the transmission module254and the transmission module254transmits data256to a computing device260(e.g. laptop computer, smart watch, smartphone, tablet, cloud-based server, etc.). The computing device260processes the data256which may then be displayed or otherwise communicated to a user, stored and optionally fed back to the transmission module254for calibration.

FIG.9shows a plan view of the first layer230and of the second layer240of the sensor system210laid open with the high-resistance material removed. The outline of layers230and240are mirror images of a foot outline. The base material212is visible for both the first layer230and the second layer240. The sensors220are shown in an array of two pattern variations for the first low-resistance material232and similarly for the second low-resistance material242. Some of the sensors220follow the pattern of sensor20ofFIG.5, while others follow the pattern of sensor120ofFIG.6. To operate this sensor system210, the first layer230and the second layer140are sandwiched with a layer of high-resistance material (not shown). The low-resistance material traces of the first layer230are connected with the first leads213and the low-resistance material traces of the second layer240are connected to the second leads214. The black lines ofFIG.9show the electrical traces and the white areas221show breaks in electrical connectivity. Both traces213and214are connected with the output interface216. Sensors220are clustered together in groups according to a “row” on one side and to a “column” on the other side of the foot arrays. In this way, no two sensors are connected to the same row and column and it is possible to fully isolate one sensor from the others by applying current to a row and reading the resistance measurement on a column. This increases resolution across the entire sensor system620; each sensor can measure pressure at a specific location, while remaining electrically isolated from all other sensors so that their resistance does not affect the reading at the sensor of interest.

FIG.10shows a cross sectional view of another embodiment of a sensor in accordance with the present disclosure. In sensor320, the second high-resistance material344is provided and no first high-resistance material is provided.

FIG.11shows a cross sectional view of another embodiment of a sensor in accordance with the present disclosure. In the sensor420, there is no high-resistance material bonded to either the first layer430or the second layer440. The high-resistance material is provided by a separate high-resistance member426positioned between the first layer430and the second layer440.

FIG.12shows a cross sectional view of another embodiment of a sensor in accordance with the present disclosure. In the sensor520, the pattern of low-resistance material532and the low-resistance material544is such that the low-resistance material532and the low-resistance material544overlap with each other. This sensor arrangement can be used for the detection of pressure via thresholds of higher and lower resistivity paths.

FIG.13shows a cross sectional view of another embodiment of a sensor in accordance with the present disclosure. The sensor620includes a force actuator670. Force actuators may allow for better actuation of a sensor when an external force is applied to the area. Force actuators may come in various configurations, including force concentrators and conformable layers. In sensor620, the force actuator670is configured to be a force concentrator673. The force concentrator673may be used to concentrate applied force onto the sensing area. The force concentrator673includes a layer of flexible material but may alternately be a layer of rigid material. The force concentrator673is configured to be in line vertically with the sensor. The force concentrator673may be smaller in area than the footprint of the sensor620, fitting within the bounds of the sensor walls established by the spacer624. The force concentrator673functions by acting as a pressure point onto which applied force is directed, transferring the force directly through the force concentrator673to the sensor620, rather than allowing the force to be dispersed onto non-sensing elements, such as the walls of the sensing element such as the spacer624. The force concentrator can be placed above, below, or between the layers of a sensing element.

FIG.14shows a cross sectional view of another embodiment of a sensor in accordance with the present disclosure. The sensor720includes a force actuator770. The force actuator770is configured as a force concentrator773disposed above the first layer730overlapping the low-resistance elements732and742.

FIG.15shows a cross sectional view of another embodiment of a sensor in accordance with the present disclosure. The sensor820includes a force actuator870. The force actuator870is configured as a force concentrator873disposed in between the first layer830and second layer840within the high-resistance material826and within the pattern of low-resistance material832, and842.

FIG.16shows a cross sectional view of another embodiment of a sensor in accordance with the present disclosure. The sensor920includes a force actuator970. The force actuator970is configured as a conformable layer977disposed above the first layer930. The conformable layer970may be used to conform to the shape of the sensor, allowing for transmission of force to the sensing element. The conformable layer may sit atop of the sensor. As force is applied to the sensor and the sensing element, the base material layers912bend towards each other and away from the applied force. In such circumstances, the force may then be concentrated onto the walls of the sensor, the spacer924, preventing additional force from transmitting through to the sensing element. An example of a conformable layer would be a foam layer sitting atop the sensor; however the conformable layer may be manufactured from any elastic material such as urethane, Sorbothane®.

FIG.17shows a cross sectional view of the sensor ofFIG.16with a force F applied to the sensor920. The conformable layer970may work to direct the applied force through to the underlying sensing element by remaining in contact with the surface outlined by the high-resistance material throughout the deformation.

FIG.18shows a cross section of the sensor1020with the first high-resistance material1034and the second high-resistance material1044in contact. Other high-resistance sensor designs inherently have an activation threshold pressure, under which the pressure cannot be measured. This activation threshold is due to the configuration of the sensor: the air gap separating the two opposing first and second low-resistance layers results in a situation where some finite amount of pressure is required to be applied to the sensor before these two opposing sensing layers will come into contact with one another through the air gap. This amount of pressure is the activation threshold. It can be minimized if the air gap distance is minimized and can be removed entirely if no air gap exists. In this latter scenario, the two opposing layers may be touching, even under a no pressure scenario. This may result in a conductive pathway, even without pressure application. Pressure application to the sensor will bring the two opposing sides into more intimate contact, increasing the amount of surface area in contact and allow for known electrical phenomena associated with force-sensing resistors to reduce the resistance between the layers. In fabrication, an insulating layer may be placed between ink layers to prevent electrical contact between layers in areas outside of the sensing element, for example, between top and bottom conducting traces. This insulating layer has a finite thickness. So, even without a dedicated spacer component separating the high-resistance material layers, there will be a finite thickness between them, establishing an air gap and resulting in a finite activation threshold.

One method to counteract this undesirable spacer thickness may be to intentionally evacuate the air between the layers, establishing a vacuum within the space between the sensing layers, and thus bringing the opposing sides into contact.

Sensors that have been evacuated of air may be used to sense tension. As the low-resistive materials of the opposing first and second layers are urged apart, a signal change resulting from the change in electrical communication between the two conductive layers may be detected.

Manufacturing of the high resistance sensors may be performed using known printing and screening techniques. Two opposing base materials may have conductive low resistance material traces placed onto them. The base materials may be made of polymer materials including polyester, polyethylene terephthalate, or other such materials. The low resistance material conductive traces may be silver, copper, gold, carbon black ink, or any other conductive material. The conductive traces may be placed onto the base material by printing, screening, lithography, photolithography, or any other form of attaching conductive material to a base. Force-sensing resistive material (FSR) is then placed onto the base substrate and conductive trace layer. The FSR may be in direct contact with the base substrate, the conductive layer, or both. The FSR is placed using known placement techniques, which may include printing, screening, spraying, lithography, photolithography, or other placement methods. A dielectric material may be placed atop the conductive layer and base substrate layer.

The two opposing layers may then be placed into contact with one another, with the FSR and conductive layer facing one another. The opposing layers may be placed into contact by an adhesive layer. The adhesive layer may act as a spacer between the two layers, establishing an air gap between the two layers. The FSR and adhesive layers may be patterned such that no adhesive layer exists between patterned FSR sections, establishing force sensing areas where the FSR from opposing layers may come into contact under applied force or pressure. The adhesive may be applied in a sparse pattern such that few adhesive anchors are used to adhere opposing layers to one another, allowing for opposing layers to come into contact under a no-pressure scenario where no adhesive is. A dedicated spacer layer may be placed between the two opposing layers, adhered to the two opposing layers with adhesive.

The two opposing layers may be connected without adhesive, using other known techniques including ultrasonic welding, heat-staking, contact welding, or other methods. These methods may allow for contact without the need for an intermediary layer such as an adhesive between opposing layers, preventing the establishment of an air gap, and allowing for contact between FSR layers in a no-pressure scenario. In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the embodiments. However, it will be apparent to one skilled in the art that these specific details are not required.