WO2023184887A1

WO2023184887A1 - Wearable sweat self-driving active collection and discharge device

Info

Publication number: WO2023184887A1
Application number: PCT/CN2022/119210
Authority: WO
Inventors: 黄海波; 庞焱; 陈立国; 申浩
Original assignee: 苏州大学
Priority date: 2022-04-02
Filing date: 2022-09-16
Publication date: 2023-10-05
Also published as: CN114680945A

Abstract

The present invention provides a wearable sweat directional self-driving collection and discharge device, which may be used for real-time monitoring of sweat lactic acid, and particularly relates to a bionic structure design thereof and a preparation method therefor. Inspiration for the bionic structure of the device comes from the non-parallel plate structure of shorebird beaks and the conical structure of pinecones. Sweat enters a channel from a bionic inlet, external energy input is not needed, and the sweat may be directionally moved merely by means of a driving force difference generated by the structure, and enters a measurement area. An electrode plate of a modified electrochemical sensor is arranged above the measurement area, and the content of lactic acid in the sweat can be specifically measured. In order to accelerate separation of new and old sweat, sweat-discharging structures are arranged on two sides of the measurement area, and sweat can be automatically discharged from the measurement area merely by means of a driving force generated by the structures. With the device, physical workers, such as athletes, can non-invasively and conveniently measure changes of the content of lactic acid in the body in real time, so as to evaluate a motion state. Moreover, the device can also react to the oxidative metabolism level, and provide early warnings for lactic acid acidosis and stress-induced ischemia.

Description

Wearable self-driven sweat collection and discharge device

Technical field

The present invention relates to the field of microfluidics related to droplet self-driving, and in particular to a flexible wearable sweat collection and discharge device that can be used for sweat lactic acid detection without external driving force.

Background technique

In recent years, there have been many types of wearable devices used to monitor human health, such as smart bracelets, smart watches, smart vests, etc. However, these devices can only monitor human activities and vital signs, such as walking speed, step asymmetry, and bilateral Support time, heart rate, blood oxygen, etc. Although biophysical information such as this is useful for analyzing physiological states, they lack direct information about dynamic biochemical and metabolic processes.

Among various metabolites, lactate is one of the most important markers of tissue oxygen binding. For athletes, firefighters and other people who consume a lot of physical energy, lactate testing can effectively evaluate exercise intensity and physical status, especially strenuous exercise. Exercise and endurance-based sports, such as speed skating, cycling, marathon, etc. In this case, aerobic metabolism usually cannot meet the body's energy needs, and the glycogen stored in the body is consumed in the form of anaerobic energy and lactic acid. . Lactic acid in the muscles enters the blood, causing blood lactic acid to rise. Blood samples must be obtained by puncturing the skin, which will cause pain and inconvenience and bring unnecessary infection risks.

technical problem

There is a linear relationship between lactic acid in sweat and blood lactic acid. Therefore, blood lactic acid concentration can be assessed by non-invasively analyzing the concentration of lactic acid in sweat. However, the traditional sweat lactic acid detection currently on the market requires the use of sweat-absorbent paper or gauze to collect sweat, and then perform the experiment. chamber for subsequent analysis, but sweat exposed to the air evaporates easily and is easily contaminated by oils, residual dirt, or other chemicals on the surrounding skin. Although existing wearable sweat detection devices can achieve in-body detection, as the amount of sweat increases, there is a problem of mixing old and new sweat, which makes the sensor readings only reflect the average value of lactic acid concentration changes rather than real-time lactic acid concentration. measurement value. Therefore, it is of great significance to achieve non-invasive and convenient real-time detection of sweat lactate concentration.

Technical solutions

In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a wearable self-driven sweat collection and discharge device that can be used for real-time monitoring of sweat lactic acid.

In order to achieve the above objects, the technical solutions of the present invention are as follows:

A wearable self-driven sweat collection and discharge device that can be used for real-time monitoring of sweat lactic acid, including:

The sweat collection inlet includes a collection inlet with a shorebird beak bionic structure, each collection inlet is in contact with the skin and is used to collect sweat;

The sweat transport and collection channel includes a sweat directional self-driven channel with a pine needle bionic structure. The tip of the pine needle is connected to the collection inlet, and the thick end is connected to the detection area, and is used to transport the collected sweat to the detection area;

The perspiration channel includes a channel with a shorebird's beak bionic structure. One end is connected to the detection area, and the other end is the old sweat outlet, which is used to discharge sweat in the detection area to avoid mixing of new and old sweat;

The top cover is installed on the top of the sweat collection and discharge equipment, and is used to insert the detection electrode of sweat lactic acid.

As a further improvement of the present invention, the shorebird beak bionic structure is a tapered microporous structure with an opening that gradually shrinks from bottom to top. The opening is large near the skin and small near the transportation channel. The taper of the tapered structure is 5°. .

As a further improvement of the present invention, the radius of the larger opening at the lower part of the shorebird's beak bionic structure is 750 microns.

As a further improvement of the present invention, the pine needle bionic structure is a semi-conical structure, which is small near the collection port and large near the detection area. The taper of the pine needle bionic structure is 5° and the length is 6400 microns. The angle between the side wall of the sweat transport channel where the pine needle structure is located and the center line is 5°, and the width of the narrow end of the sweat transport channel is 1800 microns.

As a further improvement of the present invention, the perspiration outlet is a non-parallel channel. A partition is added in the middle of the channel to increase the capillary force. The channel opening is largest near the detection area and the exit is the smallest. The non-parallel channel wall and the middle partition are sandwiched between each other. The angle is 5°, the partition width is 400 microns, the length is 4800 microns, and the narrow end of the non-parallel channels is 1800 microns wide.

As a further improvement of the present invention, the height of the slot in the top cover for inserting the sweat lactic acid detection electrode is 300 microns.

As a further improvement of the present invention, the top cover is provided with a slot above the sweat outlet for accelerating the evaporation of old sweat that has been discharged.

beneficial effects

(1). The shorebird beak bionic structure sweat collection port provided by the present invention can transport sweat from the skin to the device in one direction. Compared with micropores of other shapes, the critical intrusion pressure required for sweat to enter the tapered micropores that gradually shrink from bottom to top is the lowest, and the driving force during the wetting process is the largest and the resistance is the smallest. The structure can transmit sweat faster, and the sweat transmission efficiency is better than other micropores.

(2) Sweat that enters the transportation and collection channel through the collection port does not require the input of external energy in the channel with the pine needle bionic structure. The sweat can be quickly and directionally transported to the detection site only by relying on the Laplace pressure difference generated by the pine needle structure itself. area, and quickly fills the cavity in the detection area for subsequent detection. Traditional microchannels require the pressure generated by a large amount of perspiration to push sweat to move within the channel. Thanks to the directional self-driving structure, the device is much more efficient than traditional microchannels while ensuring portability.

(3) The perspiration structure arranged around the sweat detection area effectively solves the mixing and residual problems between new sweat and old sweat faced by existing micro-channel-based wearable sweat detection devices. Under the joint action of the sweat directional self-driven structure and the perspiration structure, the sweat in the detection chamber is always in a state of separation of old and new, that is, the concentration of the detection analyte in the detection chamber is in a state of constant change, which makes the sensor readings more accurate. Directly reflects the real-time measurement value of the analyte to achieve real-time detection of the analyte concentration, rather than just reflecting the average value of the analyte concentration change.

(4) Polydimethylsiloxane (PDMS) was selected as the material of the device mainly due to its stable structure and size in water, good biocompatibility, Young's modulus similar to skin, and good elasticity.

Description of drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are for the purpose of illustrating preferred embodiments only and are not to be construed as limiting the invention. Also throughout the drawings, the same reference characters are used to designate the same components. In the attached picture:

Figure 1 is an overall structural diagram of the equipment of the present invention;

Figure 2 is a bottom structural diagram of the equipment of the present invention;

Figure 3 is a structural diagram of the top cover of the equipment of the present invention;

Figure 4 is a schematic diagram of the lactic acid detection electrode inserted into the top cover slot;

Figure 5 shows the force diagram of droplets in different micropores;

Figure 6 is the force diagram of the droplet on the imitation pine needle half-cone structure;

Figure 7 is a dimensional diagram of the key structure of the bottom of the present invention.

Embodiments of the invention

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a thorough understanding of the disclosure, and to fully convey the scope of the disclosure to those skilled in the art.

The invention provides a wearable sweat directional self-driven collection and discharge device, which can be used for real-time monitoring of sweat lactic acid, and particularly relates to its bionic structure design and preparation method. The device's bionic structure is inspired by the non-parallel plate structure of the shorebird's beak and the tapered structure of pine needles. Sweat enters the channel from the bionic inlet without external energy input. It only relies on the driving force difference generated by the structure to make the sweat move directionally and enter the detection area. Above the detection area is the electrode piece of the modified electrochemical sensor, which can specifically detect the lactic acid content in sweat. In order to speed up the separation of old and new sweat, sweat-discharging structures are arranged on both sides of the detection area. Sweat can also be automatically discharged from the detection area solely by relying on the driving force generated by the structure.

As shown in Figure 1, a wearable self-driven sweat collection and discharge device can be used for real-time detection of sweat lactic acid.

As shown in Figures 2 and 3, the device as a whole is composed of two upper and lower parts: a bottom 1 and a top cover 10. The upper surface 9 of the bottom 1 and the lower surface 13 of the top cover 10 are bonded and sealed through oxygen plasma treatment.

As shown in Figure 2, sweat enters the device through the sweat collection inlet 3 and moves toward the detection area 6 through the sweat directional self-driving channel 5 with the pine needle bionic structure 4. While new sweat continues to enter the detection area 6, the old sweat in the detection area 6 is discharged from the detection area through the perspiration channel 7. The partition 8 in the perspiration channel 7 is used to increase the capillary force and increase the discharge speed of the old sweat. Exit the device through outlet 2.

As shown in Figure 3, the top cover opening 11 is used to accelerate the evaporation of old sweat in the sweat channel, thereby increasing the discharge speed of old sweat. The slot 14 is used to insert the lactate detection electrode. After the detection electrode is inserted into the slot 14, the working electrode of the lactate detection electrode is located exactly at the circular hole opening 12 and contacts the sweat in the detection area, as shown in Figure 4.

Analysis of the force of droplets in the micropores of the collection port

In order to confirm that the conical micropore structure of the sweat collection port has advantages in the sweat transmission process, the stress of 2 microliter droplets in micropores with three different structures was analyzed and compared. The three shapes of micropores are openings from large to small, openings from small to large and cylindrical micropores, which are defined as micropore one, micropore two and micropore three respectively, as shown in Figure 5. Sweat entering the microchannel through the micropores can be roughly divided into three steps, namely the invasion process, the wetting process and the absorption process.

Invasion process: In general, the theoretical invasion pressure (P ₀ ) of a microporous structure can be expressed by the formula P ₀ =4γ/D, where D is the diameter of the micropore and γ is the interfacial tension. It can be seen from the above formula that the size D of the micropore contact surface has a significant impact on the initial invasion process of droplets wetting the inner surface of the micropore. Compared with micropores two and three, micropore one makes it easier for droplets to enter.

Wetting process: Once the three-phase contact line of the droplet contacts the hydrophilic coating of the tapered micropore, the driving force becomes two forces: the surface tension _F of the droplet and the capillary force in the tapered micropore _F2 . The upward driving force of the droplet is F=F ₁ +F ₂ -F _g , where . In the formula, γ _water is the surface tension of water, r is the radius of the droplet, ρ is the mass density of the liquid, and g is the acceleration of gravity. F ₁ and F _g are equal for the three types of micropores, and F ₂ is different due to different shapes. micropore one ;Micropore 2 ;Micropore three . In the formula, d ₁ is the diameter of the three-phase contact line, θ is the Young's contact angle of the droplet in the hydrophilic coating, and α is the taper of the tapered micropore. Theta of the device is about 5°, and when α is 5°, , that is, micropore one has the largest driving force.

Absorption process: The liquid in the micropores is continuously absorbed into the super-hydrophilic channel under capillary action without flowing back. The capillary force provided by the super-hydrophilic channel causes the droplets to spread rapidly. The resistance F ₃ during the absorption process can be expressed as micropore- ;Micropore 2 ;Micropore three , similarly because , so micropore one has the smallest resistance.

To sum up, it can be seen that the conical micropore structure inspired by the beak structure of shorebirds, that is, micropore one, can transport droplets faster. Compared with micropores two and three, micropore one is more efficient in intrusion. Hydrostatic pressure is minimal during the process, driving force is maximal during the wetting process, and resistance is minimal during the absorption process. Under constant hydrostatic pressure, the liquid transport performance of micropore one is better than that of other micropore structures.

The non-parallel plate structure of the perspiration structure is similar to the tapered micropores of the sweat collection port. They are both designed from large to small openings. They have greater capillary force than traditional microchannels, which can make the old sweat in the cavity of the detection area clearer. Quick discharge.

Force analysis of droplets on the half-cone structure of the collection channel

Pine needles can directionally drive the liquid collected at the tip to the root, which mainly relies on the Laplace pressure generated by the shape gradient of the pine needle. The radius of the pine needle gradually increases from the tip to the root, which is generated by the shape gradient of this tapered structure. The Laplace pressure is used to achieve directional self-driving of droplets. In order to analyze the movement of droplets on the conical structure, the stress on the surface of the conical structure was analyzed, as shown in Figure 6. Water droplets are affected by three forces on the surface of the conical structure, namely surface adhesion, Laplace pressure and gravity. Among them, the adhesion force of the droplet on the conical surface is F _N =kγ _water πd/2, γ _water is the surface tension of the droplet, and k represents the numerical factor πd/2 that considers the shape of the contact line and the change of the contact angle along the contact line. The length of the contact line between the droplet and the conical structure. For simple calculation, the contact line is considered to be the section radius. At this time, the gravity of the droplet is , where r is the radius of the droplet, ρ is the mass density of the liquid, and g is the acceleration due to gravity. The Laplace pressure difference experienced by the droplet is: Among them, R ₁ and R ₂ are the cone radii on both sides of the droplet. r is the cone radius. R ₀ is the radius of the droplet, and β is the taper. When the conical structure is placed horizontally, the droplet on the conical surface only needs to overcome the adhesion between the droplet and the surface under the action of Laplace pressure to move toward the root end. Therefore, the droplet does not require external energy input at all. Directional self-driving can be achieved.

Preparation of flexible wearable devices

The preparation method of the equipment is similar to that of casting. The template is printed by a high-precision 3D printer. The printing parameters of the high-precision 3D printer are: layer thickness 10 microns, exposure time 5 seconds, polydimethylsiloxane (PDMS) evenly Apply to the surface of the template and peel off after curing to obtain a flexible wearable device. Specifically, polydimethylsiloxane (PDMS) prepolymer and cross-linking agent were mixed at a mass ratio of 10:1. Stir evenly and put it into a vacuum drying box to remove bubbles generated during the stirring process. After removing the bubbles, the PDMS Dispensing onto the template prepared by 3D printing, the PDMS will be dispensed onto The template was cured in a 70°C oven for 2 hours. After curing, it was carefully peeled off along the edge to obtain a flexible PDMS device.

The sweat transport and collection channel, that is, the sweat directional self-driving channel 5, uses Teflon for hydrophobic treatment, and the pine needle bionic structure 4 for hydrophilic treatment.

Using this device, athletes and other physical workers can non-invasively and conveniently detect changes in lactic acid content in the body in real time to assess their exercise status. It can also reflect the level of oxidative metabolism and provide early warning for lactic acidosis and stress ischemia.

The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person familiar with the technical field can easily think of changes or modifications within the technical scope disclosed in the present invention. All substitutions are within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

A wearable self-driven sweat collection and discharge device for real-time monitoring of sweat lactic acid, which is characterized by:

The sweat collection inlet includes a collection inlet with a shorebird beak bionic structure, each collection inlet is in contact with the skin and is used to collect sweat;

The sweat transport and collection channel includes a sweat directional self-driving channel with a pine needle bionic structure, the tip of the pine needle bionic structure is connected to the sweat collection inlet, and the thick end is connected to the detection area, for transporting the collected sweat to the detection area;

The perspiration channel includes a channel with a bionic structure of a shore bird's beak. One end is connected to the detection area, and the other end is an old sweat outlet for draining sweat in the detection area;

The top cover is installed on the top of the collection and discharge equipment and is used to insert the detection electrode of sweat lactic acid.
The wearable self-driven sweat collection and discharge device according to claim 1, wherein the shorebird's beak bionic structure is a tapered microporous structure with an opening gradually shrinking from bottom to top, with a large opening close to the skin. , the opening near the transportation channel is small.
The wearable self-driven sweat collection and discharge device according to claim 2, characterized in that the taper of the shorebird beak bionic structure is 5°.
The wearable self-driven sweat collection and discharge device according to claim 2, characterized in that the radius of the lower opening of the shorebird's beak bionic structure is 750 microns.
The wearable self-driven sweat collection and discharge device according to claim 1, characterized in that the pine needle bionic structure is a semi-conical structure, which is smaller near the collection port and larger near the detection area.
The wearable self-driven sweat collection and discharge device according to claim 5, characterized in that the taper of the pine needle bionic structure is 5° and the length is 6400 microns; the sweat transport and collection device where the pine needle bionic structure is located The angle between the side wall of the channel and the centerline is 5°, and the width of the narrow end of the sweat transport and collection channel is 1800 microns.
The wearable sweat self-driven active collection and discharge device according to claim 1, characterized in that the perspiration channel is a non-parallel channel, with a partition in the middle of the channel, the channel opening is the largest near the detection area, and the outlet is the smallest. .
The wearable sweat self-driven active collection and discharge device according to claim 7, characterized in that the angle between the non-parallel channel wall and the partition is 5°, the width of the partition is 400 microns, and the length is 4800 microns, and the narrow end width of the non-parallel channels is 1800 microns.
The wearable self-driven sweat collection and discharge device according to claim 1, wherein the height of the slot in the top cover for inserting the sweat lactic acid detection electrode is 300 microns.
The wearable self-driven sweat collection and discharge device according to claim 1, wherein the top cover is provided with an opening above the sweat discharge channel.