device

Abstract

This device comprises a substrate (101), fine particles (102) dispersed in the substrate (101), and a circuit (103) formed on the surface of the substrate (101). The substrate (101) is composed of a hydrogel which is composed of a hydrophilic material that is edible, and which solates at body temperature. The circuit (103) is, for example, a resonance circuit such as an LCR resonance circuit or a split ring resonator. The circuit (103) can be composed of an electroconductive material that is edible.

Description

device

[0001] The present invention relates to devices constructed from edible materials.

[0002] The application of these devices is expanding to include the environment and the human body, but recovery after use is difficult. For this reason, there is a demand for devices to decompose in response to the surrounding environment, for example by absorbing water. However, since there is a large amount of water in the environment and the human body, there is a concern that water absorption could cause the device to deform and cease functioning, so a function to suppress water absorption is essential. Currently, technology is being developed that achieves both of these contradictory functions (decomposition by water and suppression of water absorption) by innovating the substrate on which the device is constructed.

[0003] For example, a technology has been proposed in which a water diffusion barrier substrate (a structure in which hydrophobic particles are dispersed in a water-absorbent material) is constructed using biodegradable materials and a device is fabricated on this substrate (Non-Patent Document 1). The dispersed arrangement of hydrophobic particles increases the water diffusion distance and delays water absorption, allowing the device to operate during this period. There has also been a report of a structure similar to this technology (a structure in which a hydrophobic material is dispersed in a hydrophilic material) being constructed using naturally derived materials (Non-Patent Document 2).

[0004] WB Han et al., "Micropatterned Elastomeric Composites for Encapsulation of Transient Electronics", American Chemical Society Nano, vol. 17, pp. 14822-14830, 2023. 25542-25551, 2023.

[0005] However, the above-mentioned technology has the following problems. First, the water diffusion barrier substrate is made of biodegradable material and cannot be used inside the human body, limiting its range of application. Second, the water absorption rate of the device material cannot be controlled, making it impossible to destroy the device at any time, which means that the device may remain unused for a long period of time.

[0006] The present invention has been made to solve the above problems, and aims to provide a device that has a wider range of applications, does not break down immediately in an aqueous environment, and is eventually destroyed by absorbing water.

[0007] The device of the present invention comprises a substrate made of a hydrogel made of an edible hydrophilic material that solizes at body temperature, microparticles made of an edible hydrophobic material dispersed on the substrate, and a circuit formed on the surface of the substrate.

[0008] As described above, according to the present invention, microparticles made of a hydrophobic material are dispersed in a substrate made of a hydrogel made of a hydrophilic material that sols at body temperature, thereby providing a device with a wider range of applications that does not break down immediately in an aqueous environment but will eventually be destroyed by absorbing water.

[0009] FIG. 1 is a perspective view showing the configuration of a device according to an embodiment of the present invention. FIG. 2 is an explanatory diagram for explaining an example of a method for manufacturing a device according to an embodiment of the present invention. FIG. 3 is an explanatory diagram for explaining an example of a method for manufacturing a device according to an embodiment of the present invention. FIG. 4 is an explanatory diagram for explaining an example of an actual manufacturing of a device according to an embodiment of the present invention. FIG. 5 is an explanatory diagram for explaining an example of an actual manufacturing of a device according to an embodiment of the present invention. FIG. 6 is an explanatory diagram for explaining an example of an actual manufacturing of a device according to an embodiment of the present invention. FIG. 7 is a characteristic diagram showing the characteristics of a device that was actually manufactured.

[0010] A device according to an embodiment of the present invention will now be described with reference to Fig. 1. This device comprises a substrate 101, microparticles 102 dispersed in the substrate 101, and a circuit 103 formed on the surface of the substrate 101. The substrate 101 is made of a hydrogel made of an edible hydrophilic material that turns into a sol at body temperature. The substrate 101 is, for example, in the form of a sheet.

[0011] The hydrophilic material constituting the substrate 101 can be gelatin, which becomes a sol at a temperature relatively close to the body temperature of the human body, or can be mixed with edible hydrophilic materials such as collagen, chitosan, agarose, agar, and cellulose.

[0012] The microparticles 102 are made of an edible hydrophobic material. The hydrophobic material constituting the microparticles 102 can be edible materials such as beeswax or carnauba wax. For environmental applications, the hydrophobic material can be biodegradable paraffin, oils and fats, meat fat or lard, corn oil, soybean oil, rapeseed oil, olive oil, coconut oil, chocolate, butter, margarine, and the like. The hydrophobic material can also be a polyion complex (anionic cationic polymer), a monomer polymerization system (acrylamide, TEMED polymerization), a polymer polymerization system (TETRA-PEG gel), or the like.

[0013] The circuit 103 is, for example, a resonant circuit such as an LCR resonant circuit or a split-ring resonator. The circuit 103 can be made of an edible conductive material. The conductive material can be, for example, an edible metal foil such as gold or silver foil. For example, an emulsion of a hydrophilic material and a prime material is cast on the circuit 103 made of edible metal foil on a transfer substrate, as described above. After this, the resulting substrate 101 (with the microparticles 102 dispersed therein) is cooled and dried, and then peeled off from the transfer substrate, thereby transferring the circuit 103 to the substrate 101.

[0014] According to the above-described embodiment, the microparticles 102 made of a hydrophobic material are dispersed in the substrate 101 made of a hydrogel made of a hydrophilic material that turns into a sol at body temperature, so that destruction can be performed or the destruction can be accelerated at any timing. For example, by appropriately setting the amount of the dispersed microparticles 102, destruction can be performed or the destruction can be accelerated at any timing.

[0015] The freezing point of the hydrophobic material can be set lower than the temperature at which the hydrophilic material constituting the substrate 101 turns into a sol. This facilitates the production of the substrate 101 having the microparticles 102 dispersed therein. The substrate 101 having the microparticles 102 dispersed therein can be produced by cooling an emulsion obtained by mixing the hydrophilic material and the hydrophobic material described above.

[0016] For example, a substrate 101 with dispersed microparticles 102 can be produced by mixing hydrophobic beeswax and hydrophilic gelatin gel. Beeswax and gelatin have different solidification temperatures. By heating beeswax and gelatin to their respective liquefaction temperatures and mixing them, an emulsion-like state can be formed. Hydrophobic beeswax and hydrophilic gelatin are inherently difficult to mix, but they are fluid at around 80°C and can be mixed by stirring. By casting and cooling this emulsion, microspheres (microparticles) of beeswax, which has a relatively high solidification temperature, are formed first, forming a suspension. The beeswax microparticles are fixed within the gelatin film (substrate), resulting in a substrate 101 with dispersed microparticles 102.

[0017] This process is explained in more detail below. Because hydrophobic beeswax and hydrophilic gelatin are difficult to mix, the materials are first melted and mixed and stirred. Beeswax can be liquefied by heating. Gelatin, which is in a hydrogel state, is liquefied by heating. This mixing and stirring process forms an emulsion-like state, which is then cast and cooled. During this cooling process, microspheres of beeswax, which has a relatively high solidification temperature, are first formed and become a suspension. Further cooling causes the gelatin to gel, and the beeswax microparticles (beeswax particles) are fixed within the gelatin gel substrate (film) [Figure 2(a)].

[0018] The size and dispersion of beeswax particles can be adjusted by varying the mixture ratio of gelatin and beeswax. In hydrogels with a high gelatin content (19.6% gelatin, 0.04% beeswax, 80% water), only a small amount of beeswax particles form, and the dried film is hydrophilic. Increasing the beeswax content makes the film water-repellent (hydrophobic), but too much beeswax makes film formation difficult and the particles form unevenly, resulting in hydrophilicity again. Conditions where beeswax particles are packed (8% gelatin, 12% beeswax, 80% water) result in water-repellent properties and function as a water diffusion barrier [Figure 2(b)].

[0019] Next, we will explain the fabrication of the circuit in more detail. First, a circuit is fabricated on a transfer substrate using edible metal foil or the like, and then the mixed solution (emulsion) of beeswax particles and gelatin described above is cast on top of this. The cast mixed solution is cooled, and the gelatin gel is dried to form a film. When this film is peeled off from the transfer substrate, the circuit is transferred to the film, which can be used as a device [Figure 3(a)].

[0020] When the film (substrate) of this device is hydrophobic, it can maintain its circuit even in warm water (37°C), as shown at "0 min" in Figure 3(b). In contrast, at "20 min," 20 minutes after immersion in warm water, slight distortion of the substrate begins to be observed, indicating that decomposition is progressing as the gelatin gradually turns into a sol.

[0021] For a substrate (film) to exhibit hydrophobicity, hydrophobic particles must be dispersed. In the case of a combination of beeswax and gelatin, the conditions for exhibiting hydrophobicity shown in Figure 2 (8% gelatin, 12% beeswax) can be applied. In addition, when using a different material, an emulsifier can be added and the conditions for particle formation can be examined by observation using a microscope or the like.

[0022] Next, the device that was actually fabricated will be described.

[0023] [Device Example 1] First, Device Example 1, in which a device using an LCR resonant circuit was fabricated, is shown in Figure 4. Note that, below, a substrate (film) made of beeswax and gelatin was used. In addition, a film on which an inductor and one planar electrode were formed and a film on which the other planar electrode was formed were fabricated, and a capacitor was constructed by bonding them together with a double-sided adhesive to form an LCR circuit device.

[0024] Resonance due to magnetic field coupling between the loop antenna (read coil) and the device was confirmed at around 80 MHz. Furthermore, resonance was confirmed even when the loop antenna and the device were separated by a distance of about 1 cm. These results confirmed that the circuit formed with edible metal foil on the surface of the film described above was functioning as a device.

[0025] Device Example 2 Device Example 2 using a split-ring resonator is shown in Figures 5 and 6. In the case of devices intended for oral ingestion, it is necessary to observe the device response inside the body from outside. Therefore, we investigated the structure of a resonator that responds to external radio waves in a simulation environment using the electrical composition of each tissue in the human body.

[0026] The environment for simulating the S parameters of radio wave reflection was set to, for example, skin (2 mm), fat (1.55 mm), and muscle (0.25 mm), and the thickness of the split-ring resonator substrate was set to 1 mm, the long side of the metal was X = 15 mm, the short side was 12 mm, the line width was 1.5 mm, the gap was 1 mm, and the thickness was 10 μm, as shown in Figure 5(a).

[0027] The simulation results show that, compared to when no resonator is installed, it is possible to confirm radio wave reflection from the resonator around 1.9 GHz [Figure 5(b)]. This result indicates the possibility of application to the oral cavity and pharynx of the human body, as well as wireless examination of the inside of small animals.

[0028] Next, we fabricated Device Example 2 using a split-ring resonator and experimentally investigated radio wave reflection in the presence of an obstacle. Here, an acrylic tank filled with oil (L = 8 cm) was used as the obstacle [Figure 6]. Similar to the results of the simulation, radio wave reflection was confirmed at specific frequencies. However, there were differences from the simulation environment, such as the dielectric constant of the oil obstacle being significantly lower (around 3) compared to skin and muscle (around 50), and the resonator being thin (only a few hundred micrometers). We believe these differences led to a shift in the resonant frequency.

[0029] By forming a resonator using edible metal foil on a substrate made of a hydrophilic material with hydrophobic microparticles dispersed therein, it may be possible to achieve device functionality while simultaneously achieving water decomposition and suppressing water absorption.

[0030] Assuming that the device will be taken orally, it is best to make the size of the device as small as possible. In addition, to suppress radio wave attenuation within the human body, it is necessary to reflect radio waves in the frequency band of around 1-2 GHz, where the dielectric loss of skin, muscle, and fat is at its minimum. Therefore, the structure of the split ring resonator was optimized.

[0031] In a simulation environment similar to that described using Fig. 5 (an environment in which obstacles are removed and only air is present), the reflection frequency when the long and short sides of the split ring resonator and the dielectric constant of the substrate are variously changed is shown in Fig. 7. For example, when the size of the split ring resonator is 1 cm 2 In the condition "10_10", the dielectric constant of the substrate needs to be 20 in order to obtain a resonance of 1.6 GHz.

[0032] As described above, according to the present invention, microparticles made of a hydrophobic material are dispersed in a substrate made of a hydrogel that is made of a hydrophilic material and turns into a sol at body temperature, making it possible to provide a device that has a wider range of applications, does not break down immediately in an aqueous environment, and will eventually be destroyed by absorbing water.

[0033] For example, in Non-Patent Document 1, elastomer and polytetrafluoroethylene (PTFE) hydrophobic nanoparticles are mixed with dimethylformamide and then cast into a substrate. However, these materials are not biodegradable, and the use of organic solvents raises concerns about their biological effects.

[0034] For applications in the human body (living body), substrates must be constructed from edible or biocompatible materials. In living body applications, the substrate plays a major role because the surrounding environment is rich in liquids such as saliva, gastric juice, and intestinal fluids. However, most edible materials are soft and hydrophilic, and absorbent. While some edible materials, such as carnauba wax and beeswax, exhibit hydrophobic properties, hydrophilic and hydrophobic materials are poorly compatible, making them difficult to disperse, making it difficult to construct a substrate.

[0035] Furthermore, because the water absorption rate is determined by the surface structure of the substrate and the amount of hydrophobic particles mixed in the substrate, the technology of Non-Patent Document 1 cannot promote decomposition depending on the surrounding environment. Therefore, to change the water absorption rate, it is necessary to create a substrate whose surface wettability and structure change depending on the surrounding environment, and to impart stimuli responsive to pH, light, temperature, electromagnetic fields, etc. However, when considering the thermal energy available in the body from body temperature, for example, waxes, which are candidates for edible hydrophobic materials, have melting points of around 60°C, which is much higher than human body temperature, making it difficult to change the wettability of edible materials.

[0036] In response to these issues, the present invention, by constructing a device from an edible material, is expected to be useful in the human body, particularly as an oral ingestible device. Furthermore, by dispersing fine particles made of a hydrophobic material on a substrate made of a hydrogel made of a hydrophilic material that sols at body temperature, decomposition can be initiated by heat in addition to water absorption, making it possible to destroy the device at any time or accelerate its destruction, preventing the device from remaining in the body or other environments for long periods of time.

[0037] Furthermore, by using a split ring resonator or LCR resonator as the circuit, it is possible to wirelessly observe resonance phenomena caused by radio wave reflection and magnetic field coupling, and since it can be read even in the presence of obstacles, it can be applied to remote sensing of the human body and the environment.

[0038] Furthermore, because it is edible, it can be used not only in humans but also for non-invasive sensing in the livestock and agricultural fields (animals and plants), soil, marine, etc. It can also be used in situations requiring wireless management, such as food inspection, beverage inspection, cell culture medium, and culture medium for plant factories.

[0039] 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 made by a person having ordinary knowledge in the art within the technical concept of the present invention.

[0040] 101...Substrate, 102...Particle, 103...Circuit.

Claims

1. A device comprising: a substrate made of a hydrogel made of an edible hydrophilic material that sols at body temperature; microparticles made of an edible hydrophobic material dispersed in the substrate; and a circuit formed on the surface of the substrate.

2. A device according to claim 1, wherein said circuit is a resonant circuit.

3. A device according to claim 1, wherein the freezing point of said hydrophobic material is lower than the temperature at which said hydrophilic material turns into a sol.

4. A device according to claim 1, wherein the circuit is made of an edible conductive material.

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