A phase change-driven flexible wearable body temperature and blood pressure sensing device

Abstract

The present invention discloses a phase change-driven flexible wearable body temperature and blood pressure sensing device. The flexible auxiliary wristband and the body temperature visualization sensing skin are both sleeved on the wrist. The body temperature visualization sensing skin is used to represent different body surface temperatures. An installation cavity is provided in the middle of the flexible auxiliary wristband, and a thermochromic liquid-gas phase change flexible driver is embedded in the installation cavity of the flexible auxiliary wristband. The flexible auxiliary wristband on the side of the phase change flexible driver close to the wrist is fixedly connected to the pressure sensing module. The pressure sensing module is attached to the wrist, and the pressure sensing module is electrically connected to the processing circuit. After being energized and heated, the phase change flexible driver expands and deforms, and the phase change flexible driver presses the pressure sensing module, so that the pressure sensing module is pressed against the radial artery part of the wrist to collect pressure signals, and the processing circuit analyzes and processes the pressure signals to obtain blood pressure. The flexible wearable body temperature and blood pressure sensing device of the present invention has great application prospects in the fields of wearable equipment, health monitoring, etc.

Description

Technical Field

[0001] The present invention belongs to a wearable body temperature or blood pressure measuring device in the field of wearable devices, and particularly relates to a phase change-driven flexible wearable body temperature and blood pressure sensing device. Background Art

[0002] Blood pressure and body temperature are two important indicators characterizing human health conditions.

[0003] Most of the existing commercial blood pressure monitoring instruments or wearable blood pressure monitoring devices using pressure sensors require an air pump to provide air pressure to compress the human body for blood pressure measurement. Therefore, there are problems such as large volume, heavy weight, high noise, and high power consumption, and they are not suitable for long-term wearing.

[0004] Most of the existing wearable body temperature measuring devices are not stretchable, which affects the wearing comfort and cannot fit closely to the human body. Currently, there is a lack of a stretchable wearable device that visualizes and senses body temperature through continuous color changes of the same material. Summary of the Invention

[0005] In order to solve the problems in the background art, the present invention proposes a phase change-driven flexible wearable body temperature and blood pressure sensing device, which integrates two sensing functions at the same time. The thermochromic liquid-gas phase change flexible actuator provides an adjustable external pressure for the pressure sensing module without an air pump. The highly stretchable body temperature visualization sensing skin senses the body temperature by the color change at different temperatures, and can fully fit the human body without hindering the normal movement of the human body.

[0006] The technical solution adopted by the present invention is as follows:

[0007] The present invention includes a body temperature visualization sensing skin, a thermochromic liquid-gas phase change flexible actuator, a pressure sensing module, a processing circuit, a flexible auxiliary wristband, and a connection buckle;

[0008] Both the flexible auxiliary wristband and the body temperature visualization sensing skin are sleeved on the wrist. The flexible auxiliary wristband and the body temperature visualization sensing skin are arranged left and right, and the body temperature visualization sensing skin is close to the wrist and represents different body surface temperatures through different colors; both ends of the flexible auxiliary wristband are connected by a connection buckle, an installation cavity is opened in the middle of the flexible auxiliary wristband, and the thermochromic liquid-gas phase change flexible actuator is embedded in the installation cavity of the flexible auxiliary wristband. The flexible auxiliary wristband on the side close to the wrist of the thermochromic liquid-gas phase change flexible actuator is fixedly connected to the pressure sensing module. The pressure sensing module is in contact with the wrist, and the pressure sensing module is electrically connected to the processing circuit; after the thermochromic liquid-gas phase change flexible actuator is powered on and heated, it expands and deforms, and the thermochromic liquid-gas phase change flexible actuator presses the pressure sensing module, so that the pressure sensing module is pressed against the radial artery part of the wrist to collect pressure signals, and the processing circuit analyzes and processes the pressure signals to obtain blood pressure.

[0009] The thermochromic liquid-gas phase change flexible actuator includes an active layer, a passive layer and a polyimide heating film;

[0010] The active layer and the passive layer are stacked up and down to form the housing of the thermochromic liquid-gas phase change flexible actuator. The housing of the thermochromic liquid-gas phase change flexible actuator is embedded in the installation cavity of the flexible auxiliary wristband. The active layer is arranged on the side close to the wrist, and the passive layer is arranged on the side far from the wrist. A polyimide heating film is embedded in the housing of the thermochromic liquid-gas phase change flexible actuator.

[0011] The pressure sensing module includes a TPU film, silicone oil medium, semiconductor pressure chips, a support structure, a flexible cable and a fixing clamp;

[0012] The fixing clamp is fixedly connected to the flexible auxiliary wristband on the side of the thermochromic liquid-gas phase change flexible actuator close to the wrist. The support structure is fixedly installed under the fixing clamp. Two semiconductor pressure chips are fixedly installed on the upper surface of the support structure. Both semiconductor pressure chips are electrically connected to the processing circuit through flexible cables. Two fluid cavities are formed in the lower part of the support structure. The two fluid cavities are arranged in parallel and at intervals. At least two through holes are also formed in the support structure on the two fluid cavities; each fluid cavity communicates with the corresponding through hole; the bottom of the support structure is covered with a TPU film, so that the bottoms of the two fluid cavities are closed. The two fluid cavities and multiple through holes on the TPU film are filled with silicone oil medium. The two fluid cavities are respectively denoted as the first fluid cavity and the second fluid cavity. The bottom of the first fluid cavity is completely open. The silicone oil medium in one of the through holes of the first fluid cavity contacts the bottom of one semiconductor pressure chip, and the silicone oil medium in the other through hole of the first fluid cavity is sealed; two spaced slots are formed in the support structure at the bottom of the second fluid cavity. The silicone oil medium in one of the through holes of the second fluid cavity contacts the bottom of the other semiconductor pressure chip, and the silicone oil medium in the other through hole of the second fluid cavity is sealed; the TPU film is attached to the radial artery part of the wrist.

[0013] The material components of the body temperature visualization sensing skin include: thermochromic microcapsules that change color at 28 degrees with a mass fraction of 0.5%-10%, thermochromic microcapsules that change color at 33 degrees with a mass fraction of 0.5%-10%, thermochromic microcapsules that change color at 38 degrees with a mass fraction of 0.5%-10%, thermochromic microcapsules that change color at 40 degrees with a mass fraction of 0.5%-10% and a low-hardness two-component silicone rubber with a mass fraction of 80%-97%; the low-hardness two-component silicone rubber is a two-component silicone rubber with a Shore hardness between 0010 and 0050, and the mixing mass ratio of components A and B in the low-hardness two-component silicone rubber is 1:1.

[0014] The material components of the active layer include: a low-boiling-point fluid with a mass fraction of 24% - 57%, thermochromic microcapsules with a mass fraction of 1% - 5%, and a low-hardness two-component silicone rubber with a mass fraction of 42% - 75%. The low-boiling-point fluid is a fluid with a boiling point between 20°C and 100°C.

[0015] The material components of the passive layer include: thermochromic microcapsules with a mass fraction of 1% - 5% and a high-hardness two-component silicone rubber with a mass fraction of 95% - 99%.

[0016] The thickness of the flexible auxiliary wristband on the side of the installation cavity close to the wrist is less than the thickness of the flexible auxiliary wristband on the side of the installation cavity far from the wrist.

[0017] The material of the flexible auxiliary wristband is a high-hardness two-component silicone rubber.

[0018] The body temperature visualization sensing skin has five different colors in five temperature ranges: below 28°C, above 28°C - below 33°C, above 33°C - below 38°C, above 38°C - below 40°C, and above 40°C.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. The flexible wearable body temperature and blood pressure sensing device of the present invention integrates two sensing functions of body temperature and blood pressure at the same time, and has the advantages of stretchability, small size, light weight, silent, and low power consumption, and is suitable for long-term wearing.

[0021] The flexible wearable body temperature and blood pressure sensing device of the present invention uses a flexible actuator based on the liquid-gas phase change principle to provide an adjustable external pressure for the pressure sensing module without an air pump. Compared with the traditional blood pressure measurement device that requires an air pump, it reduces the volume and weight, and reduces the noise and power consumption.

[0022] 3. The flexible wearable body temperature and blood pressure sensing device of the present invention uses the body temperature visualization sensing skin to intuitively display the body surface temperature state of the wearer through multiple color changes of the same material, and has high stretchability, and can fully fit the human body without hindering human movement. Description of the Drawings

[0023] Figure 1 is a schematic structural diagram of the present invention;

[0024] Figure 2 is an exploded view of the overall structure of the present invention;

[0025] Figure 3 is an exploded view of the thermochromic liquid-gas phase change flexible actuator of the present invention;

[0026] Figure 4It is a partial sectional view of the pressure sensing module of the present invention;

[0027] Figure 5 It is another partial sectional view of the pressure sensing module of the present invention;

[0028] Figure 6 It is an exploded view of the pressure sensing module of the present invention;

[0029] Figure 7 It is a working schematic diagram of the thermochromic liquid-gas phase change flexible actuator of the present invention;

[0030] Figure 8 It is a waveform diagram of the blood pressure signal measured by the present invention;

[0031] Figure 9 It is a CIE 1931 chromaticity coordinate diagram of five variable colors at different temperatures when the temperature visualization sensing skin of the present invention adopts the components of the embodiment.

[0032] In the figure: 1. Temperature visualization sensing skin; 2. Thermochromic liquid-gas phase change flexible actuator; 21. Active layer; 22. Passive layer; 23. Polyimide heating film; 3. Pressure sensing module; 31. TPU film; 32. Silicone oil medium; 33. Semiconductor pressure chip; 34. Support structure; 35. Flexible cable; 36. Fixed clamp; 4. Processing circuit; 5. Flexible auxiliary wristband; 6. Connecting buckle. Specific embodiments

[0033] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] As Figure 1 and Figure 2 shown, the present invention includes a temperature visualization sensing skin 1, a thermochromic liquid-gas phase change flexible actuator 2, a pressure sensing module 3, a processing circuit 4, a flexible auxiliary wristband 5 and a connecting buckle 6;

[0035] The flexible auxiliary wristband 5 and the body temperature visualization sensing skin 1 are both sleeved on the wrist. The flexible auxiliary wristband 5 and the body temperature visualization sensing skin 1 are arranged at intervals left and right. The body temperature visualization sensing skin 1 is closely attached to the wrist, and different body surface temperatures are represented by different colors; both ends of the flexible auxiliary wristband 5 are connected by a connecting buckle 6. A U-shaped installation cavity is provided in the middle of the flexible auxiliary wristband 5. The U-shaped installation cavity runs through along the axial direction of the arm. A thermochromic liquid-gas phase change flexible actuator 2 is embedded in the U-shaped installation cavity of the flexible auxiliary wristband 5. The flexible auxiliary wristband 5 on the side of the thermochromic liquid-gas phase change flexible actuator 2 close to the wrist is fixedly connected to the pressure sensing module 3. The thickness of the flexible auxiliary wristband 5 on the side of the installation cavity close to the wrist is smaller than the thickness of the flexible auxiliary wristband 5 on the side of the installation cavity far from the wrist. The pressure sensing module 3 is closely attached to the wrist, and the pressure sensing module 3 is electrically connected to the processing circuit 4; after the thermochromic liquid-gas phase change flexible actuator 2 is energized and heated, it expands and deforms. The thermochromic liquid-gas phase change flexible actuator 2 presses the pressure sensing module 3 fixedly connected to the flexible auxiliary wristband 5, so that the pressure sensing module 3 is pressed tightly against the radial artery part of the wrist to collect pressure signals. After the processing circuit 4 analyzes and processes the pressure signals, blood pressure is obtained.

[0036] The material components of the body temperature visualization sensing skin 1 include: thermochromic microcapsules that change color at 28 degrees with a mass fraction of 0.5%-10%, thermochromic microcapsules that change color at 33 degrees with a mass fraction of 0.5%-10%, thermochromic microcapsules that change color at 38 degrees with a mass fraction of 0.5%-10%, thermochromic microcapsules that change color at 40 degrees with a mass fraction of 0.5%-10%, and low-hardness two-component silicone rubber with a mass fraction of 80%-97%; the low-hardness two-component silicone rubber is a two-component silicone rubber with a Shore hardness between 0010 and 0050, and the mixing mass ratio of components A and B in the low-hardness two-component silicone rubber is 1:1. In this embodiment, the components used are thermochromic microcapsules that fade to black at 28°C with a mass fraction of 9.9%, thermochromic microcapsules that fade to yellow at 33°C with a mass fraction of 5%, thermochromic microcapsules that fade to red at 38°C with a mass fraction of 0.8%, thermochromic microcapsules that show blue at 40 degrees with a mass fraction of 1.7%, and low-hardness two-component silicone rubber with a mass fraction of 82.6%; the diameter of the microcapsules is 1-10 μm.

[0037] The body temperature visualization sensing skin 1 has five different colors in five temperature ranges: below 28°C, above 28°C - below 33°C (including 28°C), above 33°C - below 38°C (including 33°C), above 38°C - below 40°C (including 38°C), and above 40°C. When using the components of this embodiment, these five colors respectively correspond to Figure 9 the five points numbered ①-⑤ in the figure.

[0038] As Figure 3As shown in the figure, the thermochromic liquid-gas phase change flexible actuator 2 includes an active layer 21, a passive layer 22, and a polyimide heating film 23. The active layer 21 and the passive layer 22 are stacked up and down to form the housing of the thermochromic liquid-gas phase change flexible actuator 2. The housing of the thermochromic liquid-gas phase change flexible actuator 2 is installed in the U-shaped installation cavity of the flexible auxiliary wristband 5. The thickness of the active layer 21 is greater than that of the passive layer 22. The active layer 21 is arranged on the side close to the wrist, and the passive layer 22 is arranged on the side far from the wrist. The polyimide heating film 23 is embedded in the housing of the thermochromic liquid-gas phase change flexible actuator 2, and the polyimide heating film 23 is connected to the power supply device through a wire.

[0039] The material components of the active layer 21 include: a low-boiling-point fluid with a mass fraction of 24%-57%, a thermochromic microcapsule with a mass fraction of 1%-5%, and a low-hardness two-component silicone rubber with a mass fraction of 42%-75%. The low-boiling-point fluid is a fluid with a boiling point between 20°C and 100°C.

[0040] The material components of the passive layer 22 include: a thermochromic microcapsule with a mass fraction of 1%-5% and a high-hardness two-component silicone rubber with a mass fraction of 95%-99%. The high-hardness two-component silicone rubber is a two-component silicone rubber with a Shore hardness between 10A and 50A. The mixing mass ratio of the A and B components of the high-hardness two-component silicone rubber is 1:1.

[0041] As Figure 7 shown, when the thermochromic liquid-vapor phase change flexible actuator 2 is powered on and heated, the overall expansion is caused by the reversible liquid-gas phase change of the low-boiling-point fluid micro-droplets contained in the active layer 21, thereby realizing driving. After power-off and cooling, it returns to its original state due to its own elasticity. Moreover, it has different deformations and output forces at different temperatures, and can provide an adjustable external pressure for the pressure sensing module. At the same time, when the thermochromic liquid-gas phase change flexible actuator 2 is powered on and heated, the thermochromic microcapsules in it change color, thereby indicating the working state of the actuator.

[0042] The material of the flexible auxiliary wristband 5 is high-hardness two-component silicone rubber.

[0043] As Figure 4 、 Figure 5 and Figure 6 shown, the pressure sensing module 3 includes a TPU film 31, a silicone oil medium 32, a semiconductor pressure chip 33, a support structure 34, a flexible cable 35, and a fixing clamp 36.

[0044] The fixed fixture 36 is fixedly connected to the flexible auxiliary wristband 5 on the side of the thermochromic liquid-gas phase change flexible actuator 2 close to the wrist. The support structure 34 is fixedly installed under the fixed fixture 36. Two semiconductor pressure chips 33 are fixedly installed on the upper surface of the support structure 34, so that the semiconductor pressure chips 33 are arranged in the gap between the fixed fixture 36 and the support structure 34. Both semiconductor pressure chips 33 are electrically connected to the processing circuit 4 through flexible flat cables 35. Two fluid cavities are formed in the lower part of the support structure 34. The two fluid cavities are arranged in parallel and at intervals, and at the same time, both fluid cavities are arranged perpendicular to the wrist axis. At least two through holes are also formed in the support structure 34 on the two fluid cavities. One through hole is used for the injection of fluid, and the other through hole is used for the transmission of pressure; each fluid cavity communicates with the corresponding through hole; the bottom of the support structure 34 is covered with a TPU film 31, so that the bottoms of the two fluid cavities are closed. The two fluid cavities and multiple through holes on the TPU film 31 are filled with silicone oil medium 32. The two fluid cavities are respectively denoted as the first fluid cavity and the second fluid cavity. The bottom of the first fluid cavity is completely open, that is, there is no support structure 34 at the bottom of the fluid cavity. The silicone oil medium 32 in one of the through holes of the first fluid cavity contacts the bottom of one semiconductor pressure chip 33, and this semiconductor pressure chip 33 is used to measure the original arterial pulse wave signal; the silicone oil medium 32 in the other through hole of the first fluid cavity is sealed; two spaced grooves are formed in the support structure 34 at the bottom of the second fluid cavity. The silicone oil medium 32 in one of the through holes of the second fluid cavity contacts the bottom of the other semiconductor pressure chip 33, and this semiconductor pressure chip 33 is used to measure the muscle movement interference signal; the silicone oil medium 32 in the other through hole of the second fluid cavity is sealed; the TPU film 31 is attached to the radial artery part of the wrist, and the radial artery part of the wrist is arranged between the two grooves of the support structure 34 at the bottom of the second fluid cavity.

[0045] Based on the measurement principle of arterial tension method, under the external pressure provided by the thermochromic liquid-vapor phase change flexible actuator 2, the TPU film 31 in the pressure sensing module 3 closely adheres to the radial artery part of the wrist, and transmits the measured pressure to the two semiconductor pressure chips 33 through the silicone oil medium 32 to respectively output the original arterial pulse wave signal and the muscle movement interference signal; the output signals are collected and processed by the processing circuit 4 to obtain the arterial pulse wave signal with muscle movement interference removed and wirelessly transmitted to the recording software in the mobile phone through Bluetooth; after initial calibration, the measured arterial pulse wave signal with muscle movement interference removed can be converted into a blood pressure signal. After experimental verification, the waveform diagram of the obtained blood pressure signal is as Figure 8 shown.

[0046] The flexible wearable body temperature and blood pressure sensing device of the present invention integrates two sensing functions of body temperature and blood pressure at the same time, does not require an air pump, and has the advantages of stretchability, small size, light weight, silent operation, and low power consumption. It is suitable for long-term wearing and has great application prospects in the fields of wearable devices, health monitoring, etc.

Claims

1. A phase change-driven flexible wearable body temperature and blood pressure sensing device, characterized in that, It includes a body temperature visualization sensing skin (1), a thermochromic liquid-gas phase change flexible actuator (2), a pressure sensing module (3), a processing circuit (4), a flexible auxiliary wristband (5) and a connecting buckle (6); Both the flexible auxiliary wristband (5) and the body temperature visualization sensing skin (1) are sleeved on the wrist. The flexible auxiliary wristband (5) and the body temperature visualization sensing skin (1) are arranged left and right. The body temperature visualization sensing skin (1) is closely attached to the wrist and represents different body surface temperatures through different colors. The two ends of the flexible auxiliary wristband (5) are connected by the connecting buckle (6). An installation cavity is provided in the middle of the flexible auxiliary wristband (5). The thermochromic liquid-gas phase change flexible actuator (2) is embedded in the installation cavity of the flexible auxiliary wristband (5). The flexible auxiliary wristband (5) on the side of the thermochromic liquid-gas phase change flexible actuator (2) close to the wrist is fixedly connected to the pressure sensing module (3). The pressure sensing module (3) is attached to the wrist. The pressure sensing module (3) is electrically connected to the processing circuit (4). After the thermochromic liquid-gas phase change flexible actuator (2) is powered on and heated, it expands and deforms. The thermochromic liquid-gas phase change flexible actuator (2) presses the pressure sensing module (3), so that the pressure sensing module (3) is pressed tightly on the radial artery part of the wrist to collect pressure signals. The processing circuit (4) analyzes and processes the pressure signals to obtain blood pressure; The pressure sensing module (3) includes a TPU film (31), a silicone oil medium (32), a semiconductor pressure chip (33), a support structure (34), a flexible flat cable (35) and a fixing fixture (36); The fixed fixture (36) is fixedly connected to the flexible auxiliary wristband (5) on the side close to the wrist of the thermochromic liquid-gas phase change flexible actuator (2). The support structure (34) is fixedly installed under the fixed fixture (36). Two semiconductor pressure chips (33) are fixedly installed on the upper surface of the support structure (34). Both of the two semiconductor pressure chips (33) are electrically connected to the processing circuit (4) through flexible flat cables (35). Two fluid cavities are formed in the lower part of the support structure (34). The two fluid cavities are arranged in parallel and at intervals. At least two through holes are also formed in the support structure (34) on the two fluid cavities. Each fluid cavity communicates with the corresponding through hole. The bottom of the support structure (34) is wrapped with a TPU film (31), so that the bottoms of the two fluid cavities are closed. The two fluid cavities and multiple through holes on the TPU film (31) are filled with silicone oil medium (32). The two fluid cavities are respectively denoted as the first fluid cavity and the second fluid cavity. The bottom of the first fluid cavity is completely open. The silicone oil medium (32) in one of the through holes of the first fluid cavity contacts the bottom of one semiconductor pressure chip (33), and this semiconductor pressure chip (33) is used to measure the original arterial pulse wave signal. The silicone oil medium (32) in the other through hole of the first fluid cavity is sealed. Two through grooves arranged at intervals are formed in the support structure (34) at the bottom of the second fluid cavity. The silicone oil medium (32) in one of the through holes of the second fluid cavity contacts the bottom of the other semiconductor pressure chip (33), and this semiconductor pressure chip (33) is used to measure the muscle movement interference signal. The silicone oil medium (32) in the other through hole of the second fluid cavity is sealed. The TPU film (31) is attached to the radial artery part of the wrist. The radial artery part of the wrist is arranged between the two through grooves of the support structure 34 at the bottom of the second fluid cavity. The thermochromic liquid-gas phase change flexible actuator (2) includes an active layer (21), a passive layer (22) and a polyimide heating film (23). The active layer (21) and the passive layer (22) are stacked up and down to form the outer shell of the thermochromic liquid-gas phase change flexible actuator (2). The outer shell of the thermochromic liquid-gas phase change flexible actuator (2) is embedded in the installation cavity of the flexible auxiliary wristband (5). The active layer (21) is arranged on the side close to the wrist, and the passive layer (22) is arranged on the side far from the wrist. A polyimide heating film (23) is embedded in the outer shell of the thermochromic liquid-gas phase change flexible actuator (2).

2. The flexible wearable body temperature and blood pressure sensing device driven by phase change according to claim 1, characterized in that The material components of the body temperature visualization sensing skin (1) include: thermochromic microcapsules that change color at 28 degrees with a mass fraction of 0.5%-10%, thermochromic microcapsules that change color at 33 degrees with a mass fraction of 0.5%-10%, thermochromic microcapsules that change color at 38 degrees with a mass fraction of 0.5%-10%, thermochromic microcapsules that change color at 40 degrees with a mass fraction of 0.5%-10%, and low-hardness two-component silicone rubber with a mass fraction of 80%-97%.

3. A phase change-driven flexible wearable body temperature and blood pressure sensing device according to claim 1, characterized in that, The material components of the active layer (21) include: a low-boiling-point fluid with a mass fraction of 24% - 57%, thermochromic microcapsules with a mass fraction of 1% - 5%, and a low-hardness two-component silicone rubber with a mass fraction of 42% - 75%.

4. The flexible wearable body temperature and blood pressure sensing device driven by phase change according to claim 1, characterized in that, The material components of the passive layer (22) include: thermochromic microcapsules with a mass fraction of 1% - 5% and a high-hardness two-component silicone rubber with a mass fraction of 95% - 99%.

5. A phase-change-driven flexible wearable body temperature and blood pressure sensing device according to claim 1, characterized in that, The thickness of the flexible auxiliary wristband (5) on the side of the installation cavity close to the wrist is less than the thickness of the flexible auxiliary wristband (5) on the side of the installation cavity away from the wrist.

6. The flexible wearable body temperature and blood pressure sensing device driven by phase change according to claim 1, characterized in that, The material of the flexible auxiliary wristband (5) is a high-hardness two-component silicone rubber.

7. A phase change-driven flexible wearable body temperature and blood pressure sensing device according to claim 1, characterized in that, The body temperature visualization sensing skin (1) has five different colors in five temperature ranges: below 28°C, above 28°C - below 33°C, above 33°C - below 38°C, above 38°C - below 40°C, and above 40°C.

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