Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L1/00—Measuring force or stress, in general
  • G01L1/14—Measuring force or stress, in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators
  • G01L1/142—Measuring force or stress, in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators using capacitors
  • G01L1/146—Measuring force or stress, in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators using capacitors for measuring force distributions, e.g. using force arrays
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
  • G01L9/0041—Transmitting or indicating the displacement of flexible diaphragms
  • G01L9/0072—Transmitting or indicating the displacement of flexible diaphragms using variations in capacitance

Definitions

• the invention is related to a textile-based large-area pressure sensing array having a pressure sensor feature comprising a conductive knitted fabric, a thermoplastic polyurethane layer having dielectric properties and a double-sided fusible layer, and a method of production the array using a pressure plate, for use in smart textile, security, healthcare, entertainment, art industries and robotic applications.
• Textile-based capacitive sensors are generally designed for pressure, tactile, and strain sensing applications. Textile structures with pressure sensor feature have an important place with their wide range of applications. Textile structures with pressure sensor feature can be used in smart textile, security, healthcare, entertainment, art, and robotic applications. Information on the areas of use are listed below.
• Smart textiles Electronic textiles are suitable for wearable technologies due to their flexible and stretchable properties.
• the proposed textile-based structures with pressure sensor feature will enable user-computer interactions when used as wristbands or gloves.
• the designed textile structures with large-area pressure sensor feature can be used as seat covers that, when integrated with software, will provide observation of posture analysis during driving and prevent accidents by warning the driver when he falls asleep.
• Healthcare Soft pressure sensor arrays have the ability to determine pressure intensity. Therefore, they can be applied to chairs or armchairs to detect sitting/balance disorders. Pressure mats can also be applied to wheelchairs or beds to monitor patient posture, enabling early detection of pressure sores, also known as bedsores.
• Soft pressure sensors would be a strong candidate for art, instead of using familiar materials such as wood and plastic in musical instruments.
• the arrays could be designed as piano keyboards and a new instrument could be created with these pressuresensor keyboards by determining the pressure intensity.
• the sensor structure can be used as exercise equipment that can track the steps of dancers and evaluate training progress with a combination of artificial intelligence as good as a professional trainer.
• Robotics applications Pressure sensors can measure different object properties and provide information through the physical interaction between a sensor and an object. For example, a robotic hand picking up an object can be integrated with sensitive sensors. This will provide feedback to the control system that prevents the object from being damaged or released too early. In terms of agriculture, the cost of manual labor for fruit harvesting can be reduced with robotic hands. Robots can recognize and determine if they are mature enough to be picked. Fruit picking robots have already been introduced to the industry. However, fragile fruits can be damaged during picking by grippers. In this situation, soft pressure sensors are really ideal tools to give robotic hands a tactile feeling so that the machines can regulate the pressure applied and not damage the crop.
• Some pressure sensors available on the market can measure compressive strength by sensing different pressure points simultaneously.
• Some products lack in flexibility and even require a flat surface to be used.
• textile materials are suitable candidates due to their natural, flexible, stretchable, and porous structure.
• the wearable electronics industry is a highly expanding field and flexibility is an important factor in the wearable electronics industry.
• production in the former methods is complex, costly, and time-consuming so that not suitable for mass production.
• the cast silicone approach requires time and constant heat for curing.
• Some products on the market contain conductive ink or paste released by screen printing or inkjet, which require complex procedures and expensive machinery.
• pressure-sensor arrays produced by older methods lack high sensitivity characteristics together with a wide operating range.
• Pressure sensors in the known state of the art have been able to show considerable sensitivity in the products on the market using some methods, but a high operating range has not been provided simultaneously.
• the air gaps formed by the pressure plate gaps between the conductive layers and the dielectric layers provide a high degree of sensitivity.
• Thermoplastic dielectric layers provide the pressure sensor with high repeatability and, most importantly, a wide operating range.
• Some pressure sensors on the market contain electrode-like conductive ink or paste released either by screen printing or inkjet printing. In other production techniques, a silicone elastomer is compressed between conductive fabric as a dielectric material.
• a method of fabricating capacitive air-gap touch sensors by printing and coating is mentioned.
• the bottom electrode is printed on a PET substrate with silver ink.
• polydimethylsiloxane was mixed with a curing agent using a polyimide pattern mask. It was spun-coated to form a sheet.
• the top electrode was formed by spin-coating a stretchable silver ink onto the sheet.
• the sensor samples were immersed in a tetrabutylammonium (TBAF) bath to remove the layer and form an air gap.
• TBAF tetrabutylammonium
• the developed textile-based large-area pressure sensing arrays and fabrication technique will enable simple, fast, and relatively inexpensive production.
• the developed textile-based large-area pressure sensing arrays are able to detect even low pressures thanks to air-gaps, and thermoplastic polyurethane layers have increased the operating range of the sensor presented here. Therefore, there is a need to develop textilebased large-area pressure sensing arrays and fabrication technique comprising a novel pressure sensor to meet the demand for a scalable, effortless, rapid, and repeatable production strategy for mass production and commercialization.
• the aim of the present invention is to provide textile-based large-area pressure sensing arrays with a wide operating range and high sensitivity, and a method of production of the sensor arrays.
• Another purpose of the present invention is to provide a method of manufacturing textilebased large-area pressure sensing arrays, which makes the manufacturing process of capacitive-based pressure sensors rapid and scalable.
• Another purpose of the present invention is to realize the production method of textile-based large-area pressure sensing arrays that enable manufactured sensors to gain sensitivity to pressure as a result of the air gaps formed between the dielectric layers themselves and between the dielectric layers and the conductive fabric layers thanks to the cell-patterned double-sided fusible layers.
• Figure 1 Schematic view of the mat containing the components of textile-based large-area pressure sensing arrays.
• Figure 2 a A cross-sectional view of the textile-based large-area pressure sensing array developed before the application of heat and pressure, without the application of a pressure plate.
• Figure 2 b A cross-sectional view of a textile-based large-area pressure sensing array developed by applying heat and pressure by the aid of the novel pressure plate
• Figure 2 c A cross-sectional view of a textile-based large-area pressure sensing array without the new pressure plate component developed after heat and pressure are applied.
• Figure 3 A graph comparing the pressure sensitivities of sensors with silicone, fusible layer only and thermoplastic polyurethane (TPU) layer with air gaps, which is the subject of this patent.
• Figure 4 Sensitivity results of square sensor cell samples with one, two and three dielectric thermoplastic polyurethane layers from left to right; a-c) Sensitivity values of 15x 15 mm 2 pressure sensor cell, d-f) Graph showing the sensitivity values of a 10x 10 mm 2 sensor cell.
• the invention relates to textile-based large-area pressure sensing arrays and includes the following elements: a pressure plate (1) located under the pressure sensing arrays, with holes responsible for the formation of air-gaps, which are necessary for high sensitivity, and identifying areas that must stick together when heat is applied (1), conductive knitted fabrics with flexibility and elastic strength (2), which are the layers on the top and bottom sides of the sensor that positioned over the pressure plate (1), where an electrostatic field is produced when a small voltage is applied,
• thermoplastic polyurethane film (3) with flexible and dielectric (insulating) properties in layers between conductive knitted fabrics (2), double-sided fusible layers (4) between the layers of thermoplastic polyurethane film (3) and conductive knitted fabrics (2), which ensures the bonding of the layers and the formation of an air gap, and have the ability to melt when heated.
• thermoplastic polyurethane film (3) provides the developed pressure sensor arrays with an increased operating range up to 1000 kPa.
• Figure 4 a-c shows the sensing behavior of a 15* 15 mm 2 sensor cell with an increasing number of thermoplastic polyurethane film (3) layers.
• Figure 4 d-f shows the sensing behavior of a 10* 10 mm 2 sensor cell with an increasing number of layers of thermoplastic polyurethane film (3).
• the pressure sensitivity of the produced sensor cells increases as the amount of air gap increases from 0% to 44%.
• the sensor with the highest air-gap amount and the least amount of thermoplastic polyurethane film layers (3) has the highest sensitivity among the 15 * 15 mm 2 sensor cells.
• the sensor with no air gap showed the lowest sensitivity performance.
• the pressure sensitivities of the three sensors are compared to analyze the effect of the approaches on the sensitivity value.
• Air-gaps are created in the cells in the layers to achieve high sensitivity.
• the flexibility problem of commonly used robust dielectric materials is eliminated by introducing such soft air-gaps between the layers. Even the soft touch of light objects can be detected.
• Doublesided fusible layers (4) containing cell-like structures were used to bond the layers. These cell-like structures obtained by cutting the double-sided fusible layers (4) with a laser cutting machine. Therefore, when heat and pressure are applied, the double-sided fusible layers (4) only adhere to the corners of the cells that helps air-gap formation.
• a new pressure plate (1) with square cell gaps has been designed for this purpose.
• the designed pressure plate (1) determines the areas that need to adhere to each other while heat is applied from above to melt the double-sided fusible layer (4), so that the required air gaps can be achieved in exact predetermined locations.
• the size of the designed pressure plate (1) can be adjusted according to the required pressure sensor shape and cell dimensions.
• thermoplastic polyurethane film (3) helps to extend the sensing range.
• the designed pressure plate (1) has holes on it, which are responsible for the formation of air-gaps.
• the pressure plate (1) is placed under the layers.
• all double-sided fusible layers (4) start to soften and the pressure plate (1) transmits the pressure only to the edges of the sensor cells.
• the conductive knitted fabric (2) starts to expand through these plate holes.
• the points of the arrays are determined by the gaps of the designed pressure plate (1), producing air gaps in the cells.
• Electrically conductive knitted fabrics (2) were formed into arrays by laser cutting. An electrostatic field is formed when a small voltage is applied to these sensor arrays. Textilebased materials, especially knitted structures, can return to their original shape after being bent, crushed, crumpled or distorted, therefore capacitance can return to initial values and repeatability can be ensured.
• the conductive knitted fabric (2) has an excellent stretch range and elastic strength.
• the pressure plate (1) only transmits the applied pressure to the edges of the array cells, while allowing the cell center to extend into the plate cavities.
• Thermoplastic polyurethane film (3) can stretch up to 500% of its original length, therefore it does not prevent the stretchability of the conductive knitted fabric (2).
• thermoplastic polyurethane film (3) was used as the dielectric layer.
• the double-sided fusible layers (4) have the ability to melt when heated.
• the double-sided fusible layers (4) are modified by laser cutting into the cell-like structure so they only stick the edges of the array cells when placed between the layers and let the fabric extend into cavities to form air-gaps.
• the double-sided fusible layers (4) melt when heat is applied and stick the conductive knitted fabrics (2) / thermoplastic polyurethane film layers (3) together.
• Air gap formation is also ensured thanks to their special design.
• thermoplastic polyurethane film (2) provides the sensor with a wide operating range.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Force Measurement Appropriate To Specific Purposes (AREA)

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Publications (2)

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• 2023
  • 2023-03-16 EP EP23771193.2A patent/EP4493897A4/de active Pending

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