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CN-122004876-A - Stitch density gradient controlled embroidery electrocardiograph sensing fabric and preparation method thereof

CN122004876ACN 122004876 ACN122004876 ACN 122004876ACN-122004876-A

Abstract

The invention provides an embroidery electrocardiograph sensing fabric controlled by stitch density gradient and a preparation method thereof, the embroidery electrocardiograph sensing fabric comprises a flexible fabric substrate layer and an embroidery structure arranged on the flexible fabric substrate layer, the embroidery structure comprises an electrocardiograph electrode contact area, a substrate area and a gradient transition area positioned between the electrocardiograph electrode contact area and the substrate area, the gradient transition area extends outwards from the boundary of the electrocardiograph electrode contact area to an area between the initial boundaries of the substrate area, the stitch density of the embroidery structure is gradually transited from a high level near the electrocardiograph electrode contact area to a low level near the substrate area, the stitch density refers to the number of needle points in unit length along the embroidery path direction and is used for representing the compactness degree of the embroidery structure, and the technical scheme can realize quantification and controllable design of embroidery stitch parameters.

Inventors

  • LUO GAOSHENG
  • GUO SHAN
  • ZHANG XIANGQUAN
  • LIN CHENG

Assignees

  • 杭州电子科技大学

Dates

Publication Date
20260512
Application Date
20260114

Claims (10)

  1. 1. The embroidery electrocardiograph sensing fabric is characterized by comprising a flexible fabric substrate layer and an embroidery structure arranged on the flexible fabric substrate layer, wherein the embroidery structure comprises an electrocardiograph electrode contact area, a substrate area and a gradient transition area between the electrocardiograph electrode contact area and the substrate area, the gradient transition area is an area extending outwards from the electrocardiograph electrode contact area boundary to the substrate area starting boundary, the width of the gradient transition area is the shortest distance between the electrocardiograph electrode contact area boundary and the substrate area starting boundary, the width W is a nominal transition area width which is designed and set, the local width is defined along the boundary outer normal direction and taken as W for irregular boundaries, the stitch density of the embroidery structure gradually transits from a high level near the electrocardiograph electrode contact area to a low level near the substrate area in the gradient transition area, so that a continuous or quasi-continuous structure transition is formed between the electrocardiograph electrode contact area and the substrate area, the stitch density is the number of needle points in unit length along the running line radial direction, the embroidery structure is used for representing the embroidery structure, the embroidery structure is filled with the embroidery structure along the boundary outer edge contact area or the outer edge of the embroidery structure, and the embroidery structure is filled with the conductive yarn in the contact area.
  2. 2. The stitch density gradient controlled embroidered electrocardiographic sensing fabric of claim 1 wherein the electrocardiographic electrode contact area is for contacting the skin of a human body to collect electrocardiographic bioelectric signals, the electrocardiographic electrode contact area is formed by embroidering conductive yarns, the embroidered stitch comprises at least conductive stitches formed by conductive yarns, and the stitch density is 8-15 stitches/mm for the first stitch density ρ 1 ,ρ 1 .
  3. 3. The stitch density gradient controlled embroidery electrocardiographic sensing fabric of claim 1 wherein the base zone is located outside the electrocardiographic electrode contact zone and is a non-conductive yarn having a stitch density of 0-3 stitches per mm for a second stitch density ρ 2 ,ρ 2 , wherein ρ 2 = 0 stitches per mm corresponds to no embroidery or needle skipping.
  4. 4. The stitch density gradient controlled embroidery electrocardiographic sensing fabric of claim 1 wherein said gradient transition zone is disposed between said electrocardiographic electrode contact zone and said base zone, d is the shortest distance from any point P in the gradient transition zone to the boundary of said electrocardiographic electrode contact zone, W is the gradient transition zone width, and normalized distance parameter Where d ε [0, W ] and t ε [0,1], then the stitch density ρ (d) at point P satisfies: Wherein f (t) is a normalized transition function and satisfies f (0) =0, f (1) =1, and a cubic Hermite interpolation polynomial is used as the normalized transition function: 。
  5. 5. the stitch density gradient controlled embroidered electrocardiographic fabric of claim 1 wherein the maximum rate of change of stitch density in the shortest distance d direction in the gradient transition zone is: Wherein ρ is in units of needle/mm and d is in units of mm, the upper limit of the change rate corresponds to the range of elastic deformation allowed by the embroidery thread when the distance between adjacent needle points is changed under the conditions of needle speed and thread tension of conventional embroidery equipment, thereby avoiding the risk of local rigidity mutation or thread loosening in the gradient boundary region, Representing the change rate of stitch density with distance, for limiting the change amplitude of stitch density at adjacent positions in the transition zone, and in the embodiment of dispersing the gradient transition zone into n layers, making the center distance of adjacent layers be Stitch density difference between adjacent layers is Then the following is satisfied: 。
  6. 6. The stitch density gradient controlled embroidered electrocardiographic sensing fabric of claim 1 wherein the embroidered stitch of the gradient transition zone is formed by a mix of conductive yarn and non-conductive yarn embroidering with a conductive yarn ratio α (d) that decreases progressively in a direction away from the electrocardiographic electrode contact zone and satisfies: , wherein, Alpha 1 is the conductive yarn ratio near the electrocardio electrode contact area, and alpha 2 is the conductive yarn ratio near the substrate area.
  7. 7. The stitch density gradient controlled embroidered electrocardiographic sensing fabric of claim 1 wherein the embroidered structure comprises at least two of the electrocardiographic electrode contact regions for forming a differential electrode pair or a multi-lead electrode array for electrocardiographic signal acquisition, the spatial layout of the plurality of electrocardiographic electrode contact regions being configurable according to standard electrocardiographic lead positions, the embroidered electrocardiographic sensing fabric further comprising electrically conductive lead regions connecting the electrocardiographic electrode contact regions to connection ends of external signal processing circuitry.
  8. 8. A method for preparing a stitch density gradient controlled embroidered electrocardiographic sensing fabric according to any one of claims 1-7, comprising the steps of: s1, selecting a fabric substrate, fixing the fabric substrate in a workbench or an embroidery machine embroidery frame, and calibrating the central position of an electrocardio electrode contact area on the fabric substrate; S2, establishing a plane coordinate system by taking the center of an electrocardio electrode contact area as an origin, defining the shortest distance d from any point P (x, y) in a gradient transition area to the boundary of the electrocardio electrode contact area, setting stitch density related parameters including 8-15 stitches/mm of stitch density rho 1 of the electrocardio electrode contact area, 0-3 stitches/mm of stitch density rho 2 of a substrate area, 3-15 mm of width W of the gradient transition area, establishing a stitch density distribution function, establishing a conductive yarn proportion distribution function, and 6, generating embroidery stitch paths of all areas according to the stitch density distribution function, wherein stitch spacing S (d) and stitch density rho (d) meet the following conditions When rho (d) =0 is calculated, the corresponding area does not generate an embroidery stitch path or adopts a needle skipping process, and the needle pitch is not calculated according to s (d) =1/rho (d); The method comprises the steps of S3, generating an embroidery program file, wherein the embroidery program file comprises an embroidery design software, converting an embroidery pattern into a program file which can be identified by a computer numerical control embroidery machine, wherein the program file or the generation process of the program file comprises a level parameter table or needle point sequence data obtained by calculation of the function, so that different devices can reproduce the same density gradient distribution when the same parameterization rule is imported, the program file comprises a stitch path, stitch density parameters, thread changing or mixing instructions and a routing sequence of each functional area, and for a gradient transition area, the continuous stitch density function is discretized into 3-8 levels, each level corresponds to one embroidery subprogram, and connection among the levels is realized through automatic thread changing or mixing instructions; s4, preparing and installing yarn materials, namely preparing conductive yarns, wherein the conductive yarns are preferably silver-plated nylon yarns or silver-plated fiber yarns, the linear density of the conductive yarns is 50-300D, the resistivity is not more than 10 omega/cm, uniformity and continuity of the yarns are checked, preparing non-conductive yarns, wherein the non-conductive yarns are selected from yarns matched with the fabric substrate, colors of the non-conductive yarns are coordinated with or are compared with the substrate, fixing the fabric substrate in an embroidery frame of a computer numerical control embroidery machine, controlling the tension of the embroidery frame to be 50-80N/m, installing the conductive yarns in a first needle position of the embroidery machine, installing the non-conductive yarns in a second needle position, and using a plurality of needle positions under the condition that a plurality of yarns are needed; S5, performing embroidery processing, namely introducing the embroidery program file generated in the step S3 into a computer numerical control embroidery machine, setting embroidery process parameters including a needle speed of 600-800 needles/min, a bottom thread tension of 30-50 cN, an upper thread tension of 60-80 cN, adjusting an embroidery presser foot pressure according to the thickness of a fabric substrate, performing embroidery processing according to a preset sequence, monitoring embroidery quality, and checking whether stitch uniformity, needle skipping or thread breakage exists and tension is proper; S6, post-treatment, namely trimming the jumper wire and the thread end on the back of the fabric, cleaning the floating thread, hot-pressing shaping, namely placing the embroidered fabric in hot-pressing equipment, wherein the hot-pressing temperature is 100-150 ℃, the hot-pressing time is 5-30S, and the hot-pressing pressure is 0.1-0.5 MPa, so that the embroidered structure is smoother, the bonding stability of the conductive yarn and the fabric substrate is improved, and detecting the quality of the embroidered electrocardiograph sensing fabric, wherein the quality of the embroidered electrocardiograph sensing fabric comprises the contact resistance test of an electrocardiograph electrode contact area, the impedance test when the embroidered fabric contacts with simulated skin, the mechanical property test, the air permeability test and the appearance check, and obtaining the embroidered electrocardiograph sensing fabric after being qualified.
  9. 9. The method of producing a stitch density gradient controlled embroidered electrocardiographic sensing fabric according to claim 1 wherein in S2, when the electrocardiographic electrode contact region is circular, the shortest distance d from point P to the electrocardiographic electrode contact region boundary is calculated: Wherein R is the distance from the point P to the center of the electrode area, R is the radius of the electrocardio electrode contact area, and when the electrocardio electrode contact area is rectangular or square, the boundary is set as The shortest distance d from the point P (x, y) to the boundary of the electrode contact area is: Wherein: When the boundary of the electrode contact area is an arbitrary closed curve, the distance d is defined as the minimum Euclidean distance from the point P to the boundary curve.
  10. 10. The method for preparing the stitch density gradient controlled embroidery electrocardiographic sensing fabric according to claim 1, wherein in step S5, the layered embroidery mode of the gradient transition zone is that the gradient transition zone is divided into n layers according to the distance direction, n is 3-8, and the center distance of the i-th layer is: The corresponding stitch density ρ i and the conductive yarn duty ratio alpha i are respectively that Then The embroidery machine sequentially completes embroidery of each level according to the sequence from outside to inside or from inside to outside, and the adjustment of the conductive yarn ratio is realized through automatic thread replacement or thread mixing among the levels.

Description

Stitch density gradient controlled embroidery electrocardiograph sensing fabric and preparation method thereof Technical Field The invention relates to the technical field of flexible wearable electronics and intelligent textiles, in particular to an embroidered electrocardiographic sensing fabric with stitch density gradient control and a preparation method thereof. Background Electrocardiography (ECG/EKG) is an important detection means reflecting the electrical activity of the heart. The existing electrocardiograph monitoring generally adopts a wet electrode and is matched with conductive gel to contact with skin, so that better signal quality can be obtained. However, in long-term wearing and daily use scenarios, such solutions still have certain limitations in terms of comfort, convenience and integration with clothing, for example, conductive gels may cause skin irritation or discomfort, have certain dependence on operating specifications during use, and the electrode adhesion or contact state changes with wearing time, affect signal stability, etc. With the development of wearable electronics and smart textiles, fabric-based dry electrodes have received attention for their characteristics of softness, breathability, flexibility, and ease of integration with clothing. The existing preparation methods of the fabric electrode comprise coating, printing, braiding, embroidering and the like, wherein the embroidering method has the advantages of flexible pattern design, good compatibility with a garment process, easy accurate control of the shape and the position of a conductive area and the like, and becomes an important implementation method of the fabric electrode. The prior embroidery technology generally regards stitch density change as a regulating means of processing efficiency or local conductive continuity, and the coupling relation between stitch density change continuity and change rate control in space, fabric mechanical property and electrode edge contact impedance stability is not recognized yet. Current embroidered electrocardiographic sensing fabrics typically achieve electrocardiographic signal acquisition by forming conductive embroidered areas on the fabric surface. In order to ensure the continuity of conduction, related schemes mostly adopt the arrangement of higher embroidery stitch density in the electrode area or the adoption of different stitch densities between the electrode area and the peripheral area for distinguishing. However, the inventors found during the course of the study that these approaches still have room for improvement in terms of: (1) The electrode area and the peripheral area are embroidered uniformly or in large area with high stitch density, so that the local rigidity of the fabric is easily increased, the softness and the air permeability are reduced, and the long-term wearing comfort is not facilitated; (2) When different stitch densities are set in a simple partition mode, the stitch densities are mutated at the boundary of an electrode area and a non-electrode area, so that the mechanical properties of the fabric are easily discontinuous, and local stress concentration is formed in the wearing, stretching or washing process; (3) The abrupt change of stitch density and conductive material distribution in space can also lead to uneven distribution of a conductive network, and larger contact impedance change of an electrode edge area, thereby influencing the acquisition stability of electrocardiosignals. In addition, in the existing embroidery type electrocardiographic sensing fabric, the setting of embroidery stitch density and related process parameters is mostly dependent on operator experience or equipment default parameters, and a definite quantitative control rule is lacked, so that the structural consistency and performance repeatability among different products are difficult to ensure, and the large-scale production and quality control are not facilitated. The technical problems to be solved by the invention include: 1) How to ensure the conductivity required by electrocardiosignal acquisition and simultaneously consider the softness and wearing comfort of the fabric; 2) How to avoid abrupt changes in stitch density at the region boundary to reduce the risk of mechanical discontinuities and non-uniform distribution of the conductive network; 3) How to establish a quantifiable and repeatable embroidery parameter control mechanism. Unlike smoothing by zoning the density alone or using an arbitrary function, the inventors have found that the spatial continuity of the stitch density in the electrode edge region and its first order rate of change are key factors affecting fabric performance. In particular, there is a coupling relationship between this parameter and fabric edge stress gradient, conductive network connectivity, and contact resistance fluctuations. Disclosure of Invention Therefore, the invention aims to provide an embroidery electrocardiograp