Wearable device

Abstract

A portion of a coating structure (103) is composed of a material having a higher Young's modulus than the other portion. In embodiment 1, the coating structure (103) includes a first coating layer (103a) that covers one surface of a substrate (101) and a second coating layer (103b) that covers the other surface of the substrate (101). At least a portion of the first coating layer (103a) is composed of a material having a higher Young's modulus than the second coating layer (103b). For example, the entire area of the first coating layer (103a) is composed of a material having a higher Young's modulus than the second coating layer (103b).

Description

Wearable device 【0001】 The present invention relates to a wearable device. 【0002】 Wearable devices such as sensor devices for detecting biological information and stimulation devices for applying stimulation to a living body have been developed. In many cases, wearable devices have hard electronic components mounted on a hard substrate and housed in a hard casing (Non-Patent Document 1), and when attached to the living body, the user may feel a foreign body sensation. 【0003】 In addition, research and development of flexible devices utilizing organic electronics has been carried out (Non-Patent Document 2). However, there are few examples of this device being put into practical use from the viewpoints of long-term reliability such as aging deterioration and impact resistance. Although flexible devices focusing on reliability have also been proposed (Patent Document 1), biocompatibility has not been considered, and a wearable device that achieves both flexibility compatible with a living body and long-term reliability has not been realized. 【0004】 For example, flexibility can be achieved by mounting electronic components on a flexible substrate. Further, it is considered desirable to cover the flexible substrate and the electronic components with a flexible casing such as rubber to reduce the foreign body sensation when in close contact with the living body. On the other hand, as described above, physical robustness is also required for wearable devices. Except for accidental cases such as dropping or stepping on the wearable device, when peeling off the wearable device attached to the human body or clothing during normal use, the most stress is applied to the wearable device. 【0005】 As shown in (a) of FIG. 6, in the state of being worn on the wearing object 315, the device 301 is normally bent in the convex direction. In contrast, as shown in (b) of FIG. 6, it bends in the concave direction at the time of peeling. Since the largest stress is applied to the portion 311 of the device 301 at the time of peeling, it is important to suppress damage or breakage of the flexible substrate, the electronic components, and the flexible casing due to the stress at the time of peeling. 【0006】 Japanese Patent No. 5717961 [[ID=二十]] 【0007】Nippon Telegraph and Telephone Corporation, "Development of Low-Power, Compact Wearable Sensor Enabling Measurement of Electrocardiogram, Acceleration, Temperature, and Humidity for Smart Healthcare," NTT News Release, 2019 [Retrieved November 14, 2024], (https: / / group.ntt / jp / newsrelease / 2019 / 11 / 08 / 191108a.html). Tomoyuki Yokota et al., "Biomedical and Medical Applications of Ultra-Flexible Electronics," J-STAGE, Biomedical Engineering, Annual Vol. 56 Abstract No. p. S140, 2018. 【0008】 However, increasing the Young's modulus (correlated with hardness and strength) of the flexible enclosure to improve the device's robustness compromises the device's flexibility. Therefore, a flexible enclosure design is required that balances the seemingly contradictory characteristics of flexibility and robustness. 【0009】 This invention was made to solve the above-mentioned problems, and aims to provide a wearable device that is flexible enough to be attached to the object without discomfort, while also being robust against the stress applied during peeling. 【0010】 The wearable device according to the present invention comprises a flexible substrate, electronic components mounted on the substrate, and a covering structure made of a flexible material formed to cover at least a portion of the substrate and the electronic components, wherein part of the covering structure is made of a material with a higher Young's modulus than other parts. 【0011】 As described above, according to the present invention, since a part of the covering structure that covers the substrate on which electronic components are mounted is made of a material with a higher Young's modulus than the other parts, a wearable device can be provided that has the flexibility to be attached to the object without discomfort, while also being robust against the stress applied when peeling is performed. 【0012】Figure 1 is a cross-sectional view showing the configuration of a wearable device according to Embodiment 1 of the present invention. Figure 2 is an explanatory diagram showing the simulation conditions used for simulating the stress generated when the wearable device peels off. Figure 3A is a characteristic diagram showing the results of the simulation of the stress generated when the wearable device peels off. Figure 3B is a characteristic diagram showing the results of the simulation of the stress generated when the wearable device peels off. Figure 4 is a characteristic diagram showing the displacement of coating structure #1, coating structure #2, and coating structure #3 when the Young's moduli E1 and E2 of the second coating layer 103b and the first coating layer 103a are changed. Figure 5A is a cross-sectional view showing the configuration of a wearable device according to Embodiment 2 of the present invention. Figure 5B is a plan view showing the configuration of a wearable device according to Embodiment 2 of the present invention. Figure 5C is a cross-sectional view showing the configuration of another wearable device according to Embodiment 2 of the present invention. Figure 6 is an explanatory diagram for explaining the state of the wearable device when it peels off. 【0013】 The following describes a wearable device according to an embodiment of the present invention. 【0014】 [Embodiment 1] First, a wearable device according to Embodiment 1 of the present invention will be described with reference to Figure 1. This wearable device comprises a flexible substrate 101, an electronic component 102 mounted on the substrate 101, and a covering structure 103 made of a flexible material that covers at least a portion of the substrate 101 and the electronic component 102. In addition, a terminal 104 for connecting the electronic component 102 to the outside can be formed on the surface of the substrate 101 opposite to the surface on which the electronic component 102 is mounted. 【0015】The coating structure 103 is made of a material in which part has a higher Young's modulus than other parts. In Embodiment 1, the coating structure 103 is made of a first coating layer 103a that covers one side of the substrate 101 and a second coating layer 103b that covers the other side of the substrate 101. The first coating layer 103a is the side that is attached to the object to be attached. For example, by providing an adhesive layer on the outer surface of the first coating layer 103a, the wearable device can be attached to the object to be attached, such as human skin or clothing, in a detachable manner. The adhesive layer can be made of, for example, a biocompatible double-sided adhesive sheet. 【0016】 Furthermore, at least a portion of the first coating layer 103a is made of a material with a higher Young's modulus than the second coating layer 103b. In this example, the entire first coating layer 103a is made of a material with a higher Young's modulus than the second coating layer 103b. 【0017】 The substrate 101 can be, for example, a general printed circuit board. Preferably, the substrate 101 can be a flexible substrate such as a flexible printed circuit board, a rigid-flexible substrate, or a multilayer flexible substrate made of polyimide. 【0018】 The electronic component 102 can be, for example, a chip resistor, chip capacitor, MPU (Micro Processing Unit), wireless communication module, sensor module, or stimulation module. The electronic component 102 can be mounted on the substrate 101 by well-known solder flow methods, solder reflow methods, etc. 【0019】 The coating structure 103 can be made of, for example, an elastomer such as rubber or a silicone ladder polymer resin. For example, the coating structure 103 can be formed by integrally molding the first coating layer 103a and the second coating layer 103b while changing their Young's moduli using a well-known insert molding method. Alternatively, the coating structure 103 can be formed by injection molding the first coating layer 103a and the second coating layer 103b separately using a predetermined mold and then bonding them together. 【0020】In this case, if the first coating layer 103a or the second coating layer 103b obstructs the signal input / output of sensors or actuators constituting the electronic component 102, an opening can be formed in the first coating layer 103a or the second coating layer 103b in the portion required for the input / output of the electronic component 102. 【0021】 Next, we will explain the results of identifying the location where the most stress occurs during delamination of a wearable device using finite element simulation. Figure 2 shows the simulation conditions. Both the first coating layer 103a and the second coating layer 103b were in the shape of sheets with a thickness of 1 mm, a width of 10 mm, and a length of 100 mm. The Young's modulus of the second coating layer 103b was set to E1, and the Young's modulus of the first coating layer 103a was set to E2. E1 and E2 are arbitrary values. For a coating structure with this structure, a fixed region 151 50 mm from the end in the a-length direction of the first coating layer 103a was fixed and constrained, and forces of -0.2 N and 0.02 N were applied to the opposite end in the x and y directions, respectively. 【0022】 The results are shown in Figures 3A and 3B. Here, both Young's moduli E1 and E2 are set to 1.49 MPa. Under these conditions, the coating structure is curved in a folded manner, and focusing on Figure 3B, the maximum stress σM is applied at the boundary between the fixed-constrained region and the curved portion. Furthermore, the stress applied to the first coating layer 103a is approximately three times greater than the stress applied to the second coating layer 103b. From these results, it is considered that if the first coating layer 103a and the second coating layer 103b are made of flexible material with the same Young's modulus, damage and breakage during delamination are more likely to occur in the first coating layer 103a. 【0023】 As is clear from the simulation results described above, by making at least a portion of the first coating layer 103a, which is the part that is attached to the object to be attached, from a material with a higher Young's modulus than the other parts, it is possible to provide robustness against the stress applied during peeling. 【0024】Figure 4 shows the displacements of coating structures #1, #2, and #3 when the Young's moduli E1 and E2 of the second coating layer 103b and the first coating layer 103a are varied. Table 1 shows the values ​​of E1 and E2 and the maximum stress σM applied to each coating structure. The load conditions are the same as in Figure 2. 【0025】 【0026】 When the same load is applied, the most deformed is coating structure #1, where both E1 and E2 are small, and the maximum stress σM at this time is 2.14 MPa. Next, in coating structure #2, only the Young's modulus E2 of the first coating layer 103a is 2.5 times that of coating structure #1. Furthermore, in coating structure #3, the Young's moduli E1 and E2 of both the second coating layer 103b and the first coating layer 103a are both twice that of coating structure #1. 【0027】 As shown in Figure 4, coating structure #2 deforms more than coating structure #3, indicating that coating structure #2 is more flexible. Furthermore, the maximum stress σM is 2.27 MPa for coating structure #2 and 2.30 MPa for coating structure #3, showing that the applied stress is also reduced for coating structure #2. In addition, since the tensile strength of a material is correlated with Young's modulus, coating structure #2, which uses a material with a higher Young's modulus (harder) due to the first coating layer 103a, is considered to be more robust than coating structure #3. 【0028】 Therefore, by combining the second coating layer 103b, which has a relatively low Young's modulus, with the first coating layer 103a, which has a relatively high Young's modulus, it is considered that flexibility and robustness can be further improved than by increasing the Young's modulus of both the second coating layer 103b and the first coating layer 103. 【0029】 [Embodiment 2] Next, a wearable device according to Embodiment 2 of the present invention will be described with reference to Figures 5A, 5B, and 5C. This wearable device comprises a flexible substrate 101, electronic components 102 mounted on the substrate 101, and a covering structure 103 made of a flexible material that covers the substrate 101 and the electronic components 102. 【0030】The coating structure 103 is composed of a material in which part has a higher Young's modulus than other parts. In Embodiment 1, the coating structure 103 is composed of a first coating layer 103'a that covers one side of the substrate 101 and a second coating layer 103b that covers the other side of the substrate 101. The first coating layer 103'a is the side that is attached to the object to be attached. In the example shown in Figure 5A, the first coating layer 103'a and the second coating layer 103b are made of a material with the same Young's modulus. 【0031】 Furthermore, the surface of the first coating layer 103'a, which forms one side of the coating structure 103, is provided with a first region 141 that is attached to the object to be attached, and a second region 142 other than the first region 141 that is not attached to the object to be attached. An adhesive layer 105 is formed in the first region 141. By providing the adhesive layer 105, the wearable device can be attached to objects such as human skin or clothing in a detachable manner. The adhesive layer 105 can be made of, for example, a biocompatible double-sided adhesive sheet. 【0032】 Furthermore, in the second embodiment, a reinforcing portion 106 made of a material with a higher Young's modulus than the other portions is provided at the boundary between the first region 141 and the second region 142. For example, the reinforcing portion 106 can be attached to the boundary between the first region 141 and the second region 142. 【0033】 As mentioned above, when a wearable device is peeled off, the maximum stress occurs at the boundary between the area to be attached (the area that is fixed and constrained) and the area that cannot be attached. A reinforcing portion 106 is provided at this boundary. The reinforcing portion 106 can be provided by molding while partially changing the Young's modulus using insert molding. The reinforcing portion 106 can be created by forming the first coating layer 103'a from a single material and then partially hardening it with heat or chemical processes. Alternatively, the reinforcing portion 106 can be created by externally reinforcing it with seals or reinforcing materials. 【0034】Furthermore, as shown in Figure 5C, a first coating layer 103a made of a material with a higher Young's modulus than the second coating layer 103b can be used, and a reinforcing portion 106 made of a material with a higher Young's modulus than the other portions can be provided at the boundary between the first region 141 and the second region 142. 【0035】 As described above, according to the embodiment of the present invention, since a part of the covering structure that covers the substrate on which electronic components are mounted is made of a material with a higher Young's modulus than the other parts, it becomes possible to provide a wearable device that has flexibility to be attached to the object without discomfort, while also being robust against stress applied during peeling. 【0036】 It should be noted that the present invention is not limited to the embodiments described above, and it is clear that many modifications and combinations can be implemented within the technical concept of the present invention by those with ordinary skill in the art. 【0037】 101... substrate, 102... electronic component, 103... coating structure, 103a... first coating layer, 103b... second coating layer, 104... terminal.

Claims

1. A wearable device comprising a flexible substrate, electronic components mounted on the substrate, and a covering structure made of a flexible material formed to cover at least a portion of the substrate and the electronic components, wherein the covering structure is made of a material in which a portion has a higher Young's modulus than the other portions.

2. A wearable device according to claim 1, wherein the coating structure comprises a first coating layer covering one surface of the substrate and a second coating layer covering the other surface of the substrate, and at least a portion of the first coating layer is made of a material having a higher Young's modulus than the second coating layer.

3. A wearable device according to claim 2, wherein the entire area of ​​the first coating layer is made of a material with a higher Young's modulus than the second coating layer.

4. A wearable device according to claim 1, comprising a first region formed on one surface of the covering structure which is to be attached to an object, and a second region other than the first region which is not to be attached to the object, wherein the boundary between the first region and the second region is provided with a reinforcing portion made of a material having a higher Young's modulus than the other portion.

5. A wearable device according to claim 4, wherein the reinforcing portion is attached to the boundary between the first region and the second region.

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