A micro-nano channel ion thermoelectric regulation method based on axial step surface potential gradient

Abstract

The present application relates to a kind of micro-nano channel ion thermoelectric regulation and control method based on axial step surface potential gradient, which is by at least two functional areas with different surface potential being arranged axially along micro-nano channel hole wall, step surface potential difference is formed between adjacent areas, and by two-part, three-part surface potential structure and the arrangement mode and axial partition ratio of different potential area, interface potential space distribution is regulated.Under the action of temperature gradient, axial non-uniform surface potential and micro-nano channel structure cooperatively change solid-liquid interface double electric layer, axial electric field and ion concentration distribution, then adjust diffusion, electromigration and thermal diffusion process, realize the regulation of open-circuit voltage, short-circuit current, thermoelectric current and thermoelectric output performance.The present application takes surface potential amplitude, arrangement mode and axial action range as adjustable parameter, provides a controllable interface regulation method for micro-nano channel ion thermoelectric transport and low-grade heat energy conversion.

Description

Technical Field

[0001] This invention relates to a control method, specifically to a micro / nano channel ion thermoelectric control method based on an axial step surface potential gradient, which enables spatial control of the double layer, ion concentration, electric field, and ion transport process by adjusting the surface potential amplitude, arrangement, and axial partition ratio. This method provides a new technical solution for low-grade thermal energy harvesting and self-powered applications in flexible wearable electronic devices. Background Technology

[0002] With the rapid development of flexible electronics, wearable sensors, and human health monitoring devices, low power consumption, lightweight design, and continuous power supply have gradually become important requirements for flexible electronic devices. Traditional batteries are limited by factors such as size, weight, lifespan, and periodic charging. Therefore, utilizing the low-grade energy continuously present around the human body to achieve self-powering has become an important development direction in the field of flexible wearable electronics. There is usually a certain temperature difference between human skin and the external environment. This temperature difference is continuous, widely distributed, and requires no additional energy input, providing favorable conditions for low-grade thermal energy harvesting.

[0003] Ion thermoelectric conversion technology utilizes the differential migration and redistribution of ions in an electrolyte under the influence of a temperature gradient, thereby generating a potential difference and current output. Compared with traditional solid-state thermoelectric systems, ion thermoelectric systems have the advantages of easily adjustable interface properties, suitability for low temperature difference environments, and easy integration with flexible material systems, making them promising for applications in human body heat harvesting, flexible sensors, and low-power self-powered devices.

[0004] In micro / nano-scale ion transport systems, ion migration is influenced not only by temperature gradients but also by the combined effects of micro / nano channel geometry, pore wall surface potential, solid-liquid interface double layer, local electric field, and ion concentration distribution. When micro / nano channels exhibit geometric asymmetry, differences in local pore size, interface confinement degree, and ion transport resistance at different axial positions lead to significant spatial non-uniformity in diffusion, electromigration, and thermal diffusion processes. Therefore, by controlling the geometry of micro / nano channels and the properties of the pore wall interface, the thermoelectric transport behavior of ions can be further altered.

[0005] Existing ion thermoelectric control methods mainly focus on factors such as electrolyte type, ion concentration, material composition, surface functional groups, and uniform pore wall surface potential. However, for micro- and nano-channels with geometrically asymmetric structures, the ion transport states at different axial positions are not the same. It is difficult to use only a uniform surface potential to achieve differentiated control for different regions, and it is also difficult to fully utilize the synergistic effect between geometric asymmetry and the spatial distribution of interfacial potential.

[0006] By setting functional regions with different surface potentials along the axial direction of micro / nano channels, a step-like surface potential difference can be formed between adjacent regions, thereby altering the local electric double layer, axial electric field, and ion concentration distribution, and further influencing the competitive relationship between diffusion, electromigration, and thermal diffusion. By constructing two-, three-, or multi-regional axial step-like surface potential structures and adjusting the surface potential amplitude, arrangement, and axial influence range of different regions, the interfacial control freedom of ion thermoelectric transport in micro / nano channels can be further expanded.

[0007] However, there is still a lack of systematic design for the thermoelectric control of ions under the synergistic effect of geometrically asymmetric micro-nano channels and axial step surface potentials. In particular, there is a lack of unified control methods for two-zone and three-zone structures, high and low surface potential arrangement, and axial surface potential boundary positions and zone ratios. Summary of the Invention

[0008] To address the aforementioned problems, the main objective of this invention is to provide a micro / nano channel ion thermoelectric control method based on an axial step surface potential gradient. This method allows for spatial adjustment of the double layer, ion concentration, electric field, and ion transport process by regulating the surface potential amplitude, arrangement, and axial partition ratio. This provides a new technical solution for low-grade thermal energy harvesting and self-powered applications in flexible wearable electronic devices.

[0009] The present invention solves the above-mentioned technical problems through the following technical solution: a micro-nano channel ion thermoelectric control method based on axial step surface potential gradient. The method is based on constructing an ion thermoelectric control system based on a micro-nano channel with geometric asymmetric structure and axial non-uniform surface potential distribution. The two ends of the micro-nano channel have different geometric dimensions. The inner wall of the micro-nano channel is divided into at least two functional regions with different surface potentials along the axial direction to form an axial step surface potential gradient.

[0010] The micro / nano channel ion thermoelectric modulation method based on axial step surface potential gradient includes the following steps: Step 1: Construct a micro / nano channel ion thermoelectric model: Based on numerical simulation methods, micro-nano channel structure models with different aspect ratios, aperture ratios, and forward and reverse arrangement methods are established. By controlling the degree of geometric asymmetry of the channels, structural systems with different ion thermoelectric transport properties are formed. Step 2: Construct an axial step surface potential gradient: The inner wall of the micro-nano channel is divided into at least two functional regions with different surface potentials along the axial direction, and different surface potentials are assigned to the pore wall. By adjusting the magnitude, arrangement order and axial range of the surface potential of each region, a dichotomous or trichotomous axial step surface potential structure is constructed. Step 3: Construct a temperature gradient-ion transport coupling system: A temperature gradient is applied at both ends of the micro-nano channel to construct an ion transport model that couples diffusion, electromigration, and thermal diffusion. The open-circuit voltage, short-circuit current, and thermocurrent under different axial step surface potential conditions are calculated, and the internal resistance, thermoelectric potential, and thermally induced power are obtained, thereby realizing the regulation of the thermoelectric output performance of ions in the micro-nano channel. The phenomenon of ion thermoelectric power generation is as follows: under the combined action of temperature gradient, geometric asymmetric structure and axial step surface potential, the double layer, ion concentration and electric field distribution in the channel are changed, the diffusion, electromigration and thermal diffusion processes of ions are regulated, and thermoelectric potential and thermocurrent output are realized. The obtained electrical energy is used to power flexible wearable low-power devices.

[0011] In a specific embodiment of the present invention, in step one, the micro-nano channel continuously changes its axial cross-sectional dimensions, and large-hole end and small-hole end are formed at both ends of the channel, respectively. By changing the relative arrangement direction of the large-hole end and the small-hole end, forward and reverse micro-nano channel structure models are constructed, and the geometrically asymmetric micro-nano channel is selected as conical.

[0012] In a specific embodiment of the present invention, in step one, the half-width H of the macro-aperture end of the micro / nano channel... t The value range is 80–120 nanometers; the design range for the half-width of the small hole end is 20–90 nanometers; and the design range for the axial length of the channel is 1000–3000 nanometers.

[0013] In a specific embodiment of the present invention, in step one, the half-width H of the macro-aperture end of the micro / nano channel... t The value is 100 nanometers. The half-width of the aperture end is 30 nanometers, and the axial length of the channel is 1800 nanometers.

[0014] In a specific embodiment of the present invention, in step one, the forward and reverse structures of the micro-nano channel are defined according to the positional relationship between the macropore end and the micropore end relative to the ion transport direction. The transport process from the macropore end to the micropore end is defined as forward, and the transport process from the micropore end to the macropore end is defined as reverse. At the same time, the temperature gradient direction remains consistent in both the forward and reverse models.

[0015] In a specific embodiment of the present invention, in step two, the bipolar axial step surface potential structure divides the inner wall of the micro-nano channel into two surface potential functional regions along the axial direction. The surface potential of the hole wall in one region is 0.075V, and the surface potential of the hole wall in the other region is designed to range from 0.015 to 0.075V, thus forming an axial non-uniform surface potential structure with high potential in the large hole section and low potential in the small hole section, or low potential in the large hole section and high potential in the small hole section.

[0016] In a specific embodiment of the present invention, in step two, the three-part axial step surface potential structure divides the inner wall of the micro-nano channel into first, second and third surface potential regions along the axial direction. A multi-level axial step surface potential structure is constructed by different arrangements of high, medium and low surface potentials, and each region has a surface potential of high-end potential ψ1, middle-section potential ψ2 and high-end potential ψ3 respectively.

[0017] In a specific embodiment of the present invention, in step two, the high-end potential is selected as 0.075V, the low-end potential is selected as 0.015V, and the middle-section potential is selected in the range of 0.015 to 0.075V.

[0018] In a specific embodiment of the present invention, in step two, for the bipolar axial step surface potential structure, let the normalized axial distances from the surface potential boundary to the small hole end and the large hole end be L respectively. n and L w Satisfying L n +L w =1, axial surface potential partition ratio λ p =L n / L w By changing the partition ratio, the effective range of the high and low surface potential regions along the channel axis is adjusted, where L n and L w The range is 0.1 to 0.9, and the partition ratio is λ. p The value was chosen as 0.667.

[0019] In a specific embodiment of the present invention, in step three, a temperature gradient is formed by setting a temperature difference between the two ends of the micro-nano channel. The temperature at the high-temperature end is T0+ΔT, the temperature at the low-temperature end is T0, the reference temperature T0 is 293.15 Kelvin, and the temperature difference ΔT is designed to be within the range of 0.5 to 10 Kelvin.

[0020] The positive and progressive effects of this invention are as follows: The micro / nano channel ion thermoelectric control method based on axial step surface potential gradient provided by this invention has the following advantages: 1. This invention combines the geometrically asymmetric structure of micro / nano channels with an axially non-uniform surface potential distribution, transforming the surface potential of the pore wall from a uniform distribution to an axially partitioned non-uniform distribution. This enables spatial control of the solid-liquid interface double layer, ion concentration, and axial electric field. By constructing two- or three-part axial step-type surface potential structures and adjusting the magnitude and arrangement order of the surface potential in different regions, the diffusion, electromigration, and thermal diffusion processes can be altered, thereby regulating output performance such as open-circuit voltage, short-circuit current, thermocurrent, and thermally induced power.

[0021] 2. This invention further adjusts the axial range of different surface potential regions by changing the boundary position of the surface potential and the ratio of axial surface potential zones, while keeping the overall geometric dimensions of the micro / nano channel and the amplitudes of high and low surface potentials constant. This achieves multi-level synergistic control of surface potential amplitude, arrangement, and spatial position. Preferably, a tapered micro / nano channel with large and small aperture ends is used, combined with forward and reverse arrangement, which can further adjust ion concentration polarization and the competitive relationship between diffusion and electromigration.

[0022] 3. The method described in this invention can also be applied to flexible ion thermoelectric systems, utilizing the low-grade temperature difference between human skin and the external environment for energy harvesting, providing a new ion thermoelectric control scheme for flexible wearable sensors and low-power self-powered electronic devices. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the binary and ternary differentiation principles of the micro / nano channel ion thermoelectric control method based on the axial step surface potential gradient of the present invention.

[0024] Figure 2 This is a schematic diagram of the simulated structure of the wearable ion thermoelectric power generation device of the present invention, which includes a conical bipolar and tripolar micro-nano channel array, a thermally conductive contact layer, and an environmental heat dissipation layer.

[0025] Figure 3-1 The graph shows the positive and negative thermally induced power results under the triadic model, where the surface potential exhibits a stepwise distribution along the low, medium, and high axes.

[0026] Figure 3-2 The graph shows the positive and negative thermally induced power results under the three-part model, where the surface potential exhibits a high-low-high axial step distribution.

[0027] Figure 3-3 The graph shows the positive and negative thermally induced power results under the triadic model, where the surface potential exhibits a stepwise distribution along the low-high-low axis.

[0028] Figure 3-4 This is a graph showing the positive and negative thermally induced power results under the triadic model, where the surface potential exhibits a stepwise distribution along the high, medium, and low axes.

[0029] Figure 4-1 It is a positive and negative thermally induced power diagram with a wide range of high surface potential and a narrow range of low surface potential under the dichotomy model.

[0030] Figure 4-2 It is a positive and negative thermally induced power diagram with a wide range of low surface potential and a narrow range of high surface potential under the binary model.

[0031] Figure 4-3 This is a thermally induced power diagram showing different partition ratios under the dichotomy model with a wide-segment potential of 0.03V and a narrow-segment potential of 0.075V. Detailed Implementation

[0032] The preferred embodiments of the present invention are given below with reference to the accompanying drawings to illustrate the technical solution of the present invention in detail.

[0033] To address the issues of relatively uniform surface potential distribution on the pore walls and the difficulty in achieving differentiated interface control across different axial regions in existing micro / nanochannel ion thermoelectric systems, this invention provides a micro / nanochannel ion thermoelectric control method based on an axial step surface potential gradient. This method is based on micro / nanochannels with geometrically asymmetric features. By setting functional regions with different surface potentials along the axial direction of the pore wall and adjusting the magnitude, arrangement order, and axial influence range of these functional regions, an axially non-uniform surface potential distribution is constructed. Under the influence of a temperature gradient, the geometrically asymmetric structure and the axial step surface potential jointly affect the solid-liquid interface double layer, ion concentration, and axial electric field distribution within the channel, thereby regulating diffusion, electromigration, and thermal diffusion processes to achieve control over the ion thermoelectric output performance of the micro / nanochannel.

[0034] In this invention, the micro / nano channel is an ion transport channel with different local geometric dimensions along the axial direction. Preferably, a tapered micro / nano channel with continuously varying cross-sectional dimensions along the axial direction is used as a geometrically asymmetric structure, with a macro-pore end and a micro-pore end formed at its two ends, respectively. The half-width H of the macro-pore end of the micro / nano channel is... t The design range is 80–120 nanometers, preferably 100 nanometers. The design range of the half-width at the aperture end is 20–90 nanometers, preferably 30 nanometers. The design range of the axial length of the channel is 1000–3000 nanometers, preferably 1800 nanometers. By changing the size of the large aperture end, the size of the small aperture end, and the axial length of the channel, the geometric asymmetry of the micro / nano channel can be adjusted.

[0035] In this invention, the forward and reverse transport modes of the micro / nano channels are defined according to the positional relationship between the macro- and micro-orifice ends relative to the ion transport direction. The ion transport process from the macro- orifice end to the micro- orifice end is defined as forward, and the ion transport process from the micro- orifice end to the macro- orifice end is defined as reverse. In both forward and reverse models, the temperature gradient direction remains consistent; only the arrangement of the macro- and micro-orifice ends of the micro / nano channels relative to the ion transport direction is changed to study the influence of geometrically asymmetric directions on ion thermoelectric transport behavior.

[0036] In this invention, the axial step surface potential gradient refers to the arrangement of at least two functional regions with different surface potentials along the axial direction of the micro / nano channel wall, creating a surface potential difference between adjacent functional regions and causing the surface potential of the hole wall to change in a step manner along the channel axis. By changing the magnitude of the surface potential, the axial arrangement, and the range of influence of each functional region, the spatial distribution of the double layer, ion concentration, and axial electric field inside the micro / nano channel can be further altered.

[0037] like Figure 1 and2 As shown, the present invention preferably constructs two types of axial step-type surface potential structures: a two-partition structure and a three-partition structure. The two-partition structure divides the wall of the micro / nano channel along the axial direction into two continuous surface potential functional regions. The three-partition structure divides the wall of the channel along the axial direction into first, second, and third surface potential functional regions sequentially. Figure 1 The diagram also shows different high, medium, and low surface potential arrangements and the corresponding forward and reverse micro / nano channel structures.

[0038] The micro / nano channel ion thermoelectric control method based on axial step surface potential gradient described in this invention includes the following steps: Step 1: Construct a micro / nano channel ion thermoelectric model.

[0039] A micro-nano channel model with geometric asymmetry was established based on numerical simulation, with a tapered micro-nano channel being the preferred choice. By adjusting the half-width of the large-aperture end, the half-width of the small-aperture end, the axial length of the channel, and the forward and reverse arrangement, micro-nano channel structure models with different degrees of geometric asymmetry were constructed, providing a geometric basis for subsequent axial surface potential control.

[0040] Step 2: Construct an axial step surface potential gradient.

[0041] The walls of micro / nano channels are divided into two or three functional regions along the axial direction, and each region is assigned a different surface potential. By adjusting the magnitude, arrangement, and axial range of the surface potentials in each functional region, two- or three-part axial step-type surface potential structures can be constructed. For two-part structures, the boundary positions of the surface potentials can be further changed to adjust the range of influence of the high and low surface potential regions along the channel axis.

[0042] Step 3: Construct a temperature gradient-ion transport coupling system.

[0043] A temperature gradient was established at both ends of the micro / nano channel to construct an ion transport model coupling diffusion, electromigration, and thermal diffusion. The open-circuit voltage, short-circuit current, and thermocurrent were calculated under different geometries, different surface potential arrangements, and different axial partitioning conditions. Furthermore, the internal resistance, thermoelectric potential, and thermally induced power were obtained to characterize the regulatory effect of the axial step surface potential on the thermoelectric output performance of the micro / nano channel.

[0044] Furthermore, in step one, the half-width H at the macro-aperture end of the micro / nano channel... t The aperture width is 80–120 nm, preferably 100 nm. The half-width at the aperture end is 20–90 nm, preferably 30 nm. The axial length of the channel is 1000–3000 nm, preferably 1800 nm.

[0045] Furthermore, in step one, the ion transport process from the macropore end to the micropore end is defined as forward, and the ion transport process from the micropore end to the macropore end is defined as reverse. The temperature gradient directions in the forward and reverse models are consistent.

[0046] Furthermore, in step two, for the two-part axial step surface potential structure, the surface potential of the hole wall in one functional region is set to 0.075V, while the surface potential of the hole wall in the other functional region varies within the range of 0.015 to 0.075V. Based on the positional relationship between the high and low surface potentials and the large and small hole segments, two basic axial non-uniform surface potential structures can be formed: a high potential in the large hole segment and a low potential in the small hole segment, and a low potential in the large hole segment and a high potential in the small hole segment.

[0047] Furthermore, in step two, for the three-part axial step-type surface potential structure, the wall of the micro-nano channel is sequentially divided into first, second, and third surface potential regions along the axial direction, each region having surface potentials ψ1, ψ2, and ψ3, respectively. The high surface potential is preferably 0.075V, the low surface potential is preferably 0.015V, and the surface potential in the middle section varies within the range of 0.015 to 0.075V, thus forming multi-level axial step-type surface potential structures such as high-medium-low, low-medium-high, high-low-high, and low-high-low.

[0048] Furthermore, in step two, for the two-part axial step surface potential structure, let the normalized axial distances from the surface potential boundary to the small hole end and the large hole end be L respectively. n and L w Satisfying L n +L w =1, axial surface potential partition ratio λ p =L n / L w By changing the partition ratio, the effective range of the high and low surface potential regions along the channel axis is adjusted, where L n and L w The range is 0.1 to 0.9, and the partition ratio is λ. p The preferred value is 0.667.

[0049] Furthermore, in step three, a temperature gradient is formed by setting a temperature difference at both ends of the micro-nano channel, wherein the temperature at the high-temperature end is set to T0+ΔT, the temperature at the low-temperature end is T0, the reference temperature T0 is 293.15 Kelvin, and the temperature difference ΔT is designed to range from 0.5 to 10 Kelvin, preferably 5 Kelvin.

[0050] Below is a specific example: Example 1 This embodiment uses numerical simulation to calculate and analyze a micro / nano channel ion thermoelectric control method based on an axial step surface potential gradient. For example... Figure 1 and Figure 2 As shown, a conical micro-nano channel with geometric asymmetry is preferably used as the research object. By adjusting the number of axial surface potential regions on the pore wall, the arrangement of surface potentials, and the axial range of action, the effects of dichotomy, trichotomy, and the ratio of axial surface potential partitions on the ion thermoelectric output performance are studied.

[0051] In the calculations, the half-width at the macropore end of the tapered micro / nano channel was set to 100 nm, the half-width at the micropore end to 30 nm, and the axial length of the channel was set to 1800 nm. The reference temperature T0 was set to 293.15 Kelvin, and the temperature difference ΔT was set to 5 Kelvin. The ion transport process from the macropore end to the micropore end was defined as forward, and the ion transport process from the micropore end to the macropore end was defined as reverse. The temperature gradient directions in the forward and reverse models were consistent. Under the above conditions, an ion transport model coupling diffusion, electromigration, and thermal diffusion was constructed. The open-circuit voltage, short-circuit current, and thermocurrent under different axial surface potential structures were calculated, and the internal resistance, thermoelectric potential, and thermally induced power were further obtained.

[0052] like Figure 1 As shown, the influence of a three-part axially stepped surface potential structure on the thermoelectric output performance of ions is first investigated. Specifically, the wall of a conical micro / nano channel is sequentially divided into three functional regions along the axial direction, with the high surface potential set at 0.075V, the low surface potential at 0.015V, and the surface potential of the middle section varying within the range of 0.015–0.075V. By changing the arrangement of the high, medium, and low surface potentials along the channel axis, three-part surface potential structures such as high-medium-low, low-medium-high, high-low-high, and low-high-low are constructed, and the thermally induced power of the forward and reverse models is calculated respectively.

[0053] Depend on Figure 3-1 , Figure 3-2 , Figure 3-3 , Figure 3-4 It can be seen that, while keeping the high and low surface potentials and the geometric parameters of the micro / nano channel constant, the thermally induced power of each triadic model changes accordingly with the change of the surface potential of the middle section. Furthermore, the output amplitude and trend differ significantly under different surface potential arrangements and forward / reverse transport conditions. This indicates that, without changing the overall geometry and temperature gradient of the micro / nano channel, the thermoelectric output performance of ions can be adjusted simply by changing the surface potential of the middle section and its axial arrangement. The triadic structure, by forming two step interfaces of surface potential within a single micro / nano channel, transforms the surface potential of the pore wall from a uniform distribution to a multi-level axially non-uniform distribution, thereby increasing the degree of freedom in spatially controlling the interface potential.

[0054] like Figure 4-1As shown, the axial step-type surface potential structure of the dichotomous structure was further investigated. For the structure with high potential in the large pore section and low potential in the small pore section, the surface potential of the large pore wall was fixed at 0.075V, while the surface potential of the small pore wall was gradually increased from 0.015V to 0.075V. The thermally induced power of the forward and reverse models was calculated respectively. As the surface potential of the small pore section gradually increased, the surface potential difference between the large and small pore sections gradually decreased, and the thermally induced power of the forward and reverse models changed continuously. This indicates that by adjusting the surface potential amplitude in different regions of the dichotomous structure, continuous control of the ion thermoelectric output can be achieved.

[0055] like Figure 4-2 As shown, under the same geometric parameters and temperature conditions, a structure with a low potential for the large-aperture section and a high potential for the small-aperture section was further constructed. In the calculations, the surface potential of the small-aperture section wall was fixed at 0.075V, while the surface potential of the large-aperture section wall was gradually increased from 0.015V to 0.075V. The results show that the forward and reverse models exhibit significantly different thermoelectric output characteristics. The reverse model shows a more pronounced nonlinear thermo-induced power response with changes in the surface potential of the large-aperture section, and exhibits a significant thermo-induced power enhancement when the surface potential of the large-aperture section is approximately 0.03V. The forward model, however, did not exhibit the same degree of peak-type response within the same range.

[0056] The above results demonstrate that the arrangement of high and low surface potentials along the axial direction of the conical micro / nano channel, along with the forward and reverse transport modes of the micro / nano channel, can jointly influence ion thermoelectric output. When a reverse structure is adopted, transporting from the small aperture end to the large aperture end, while maintaining a higher surface potential in the small aperture segment and a lower surface potential in the large aperture segment, different spatial matching relationships are formed between the axially non-uniform surface potential and the geometrically asymmetric structure. Therefore, in this embodiment, a reverse-divided conical micro / nano channel with a small aperture wall surface potential of 0.075V and a large aperture wall surface potential of 0.03V is further selected as a representative model for the study of axial surface potential partitioning.

[0057] like Figure 4-3 As shown, while keeping the high and low surface potential amplitudes, the geometric parameters of the tapered micro / nano channel, and the temperature gradient constant, only the boundary position of the bipolar axial step surface potential structure is changed. Let the normalized axial distances from the surface potential boundary position to the small and large aperture ends be L, respectively. n and L w Satisfying L n +L w =1, and define the axial surface potential partition ratio as: λ p =L n / L w By changing L n and L wThe relative size of the surface potential regions causes changes in the axial range of the high and low surface potential regions within the micro-nano channel.

[0058] Depend on Figure 4-3 It can be seen that, with the surface potential of the small aperture section maintained at 0.075V and the surface potential of the large aperture section maintained at 0.03V, the thermally induced power of the reverse micro / nano channel exhibits a significant non-monotonic change with the variation of the axial surface potential partition ratio. Under the conditions studied in this embodiment, when the axial surface potential partition ratio λ... p At approximately 0.667, the system exhibits a relatively significant thermally induced power response. This result indicates that the ion thermoelectric output is influenced not only by the amplitude and alignment of the surface potential, but also by the axial spatial position of different surface potential regions within the micro / nano channel.

[0059] comprehensive Figure 3-1 , Figure 3-2 , Figure 3-3 , Figure 3-4 and Figure 4-1 , Figure 4-2 , Figure 4-3 As can be seen, this invention can construct a multi-level interface potential control method by adjusting the number of surface potential functional regions, the surface potential amplitude, the axial arrangement, and the axial surface potential partition ratio. Specifically, the tri-section structure can form a multi-level step-like interface potential distribution by changing the surface potential of the middle section. The di-section structure can obtain different thermoelectric output responses by changing the arrangement direction of the high and low surface potentials. Further adjustment of the axial surface potential partition ratio can further control the ion thermoelectric output performance without changing the overall geometric dimensions and temperature gradient. Therefore, this invention forms a micro / nano channel ion thermoelectric control method composed of surface potential amplitude, arrangement, and axial operating range.

[0060] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as defined by the appended claims and their equivalents.

Claims

1. A method for thermoelectric control of ions in micro / nano channels based on an axial step surface potential gradient, characterized in that: The method is based on constructing an ion thermoelectric control system using micro-nano channels with geometrically asymmetric structures and axially non-uniform surface potential distribution. The two ends of the micro-nano channels have different geometric dimensions, and the inner wall of the micro-nano channels is divided into at least two functional regions with different surface potentials along the axial direction to form an axial step surface potential gradient. The micro / nano channel ion thermoelectric modulation method based on axial step surface potential gradient includes the following steps: Step 1: Construct a micro / nano channel ion thermoelectric model: Based on numerical simulation methods, micro-nano channel structure models with different aspect ratios, aperture ratios, and forward and reverse arrangement methods are established. By controlling the degree of geometric asymmetry of the channels, structural systems with different ion thermoelectric transport properties are formed. Step 2: Construct an axial step surface potential gradient: The inner wall of the micro-nano channel is divided into at least two functional regions with different surface potentials along the axial direction, and different surface potentials are assigned to the pore wall. By adjusting the magnitude, arrangement order and axial range of the surface potential of each region, a dichotomous or trichotomous axial step surface potential structure is constructed. Step 3: Construct a temperature gradient-ion transport coupling system: A temperature gradient is applied at both ends of the micro-nano channel to construct an ion transport model that couples diffusion, electromigration, and thermal diffusion. The open-circuit voltage, short-circuit current, and thermocurrent under different axial step surface potential conditions are calculated, and the internal resistance, thermoelectric potential, and thermally induced power are obtained, thereby realizing the regulation of the thermoelectric output performance of ions in the micro-nano channel. The phenomenon of ion thermoelectric power generation is as follows: under the combined action of temperature gradient, geometric asymmetric structure and axial step surface potential, the double layer, ion concentration and electric field distribution in the channel are changed, the diffusion, electromigration and thermal diffusion processes of ions are regulated, and thermoelectric potential and thermocurrent output are realized. The obtained electrical energy is used to power flexible wearable low-power devices.

2. The micro / nano channel ion thermoelectric control method based on axial step surface potential gradient according to claim 1, characterized in that: In step one, the cross-sectional dimensions of the micro-nano channel change continuously along the axial direction, and large-hole end and small-hole end are formed at both ends of the channel. By changing the relative arrangement direction of the large-hole end and the small-hole end, forward and reverse micro-nano channel structure models are constructed. The geometrically asymmetric micro-nano channel is selected as conical.

3. The micro / nano channel ion thermoelectric control method based on axial step surface potential gradient according to claim 2, characterized in that: In step one, the half-width H of the macropore end of the micro / nano channel... t The value range is 80–120 nanometers; the design range for the half-width of the small hole end is 20–90 nanometers; and the design range for the axial length of the channel is 1000–3000 nanometers.

4. The micro / nano channel ion thermoelectric control method based on axial step surface potential gradient according to claim 3, characterized in that: In step one, the half-width H of the macropore end of the micro / nano channel... t The value is 100 nanometers; the half-width of the small hole end is 30 nanometers, and the axial length of the channel is 1800 nanometers.

5. The micro / nano channel ion thermoelectric control method based on axial step surface potential gradient according to claim 1, characterized in that: In step one, the forward and reverse structures of the micro-nano channels are defined according to the positional relationship between the macropore end and the micropore end relative to the ion transport direction. The transport process from the macropore end to the micropore end is defined as forward, and the transport process from the micropore end to the macropore end is defined as reverse. At the same time, the temperature gradient direction remains consistent in both the forward and reverse models.

6. The micro / nano channel ion thermoelectric control method based on axial step surface potential gradient according to claim 1, characterized in that: In step two, the bipolar axial step surface potential structure divides the inner wall of the micro-nano channel into two functional surface potential regions along the axial direction. The surface potential of the hole wall in one region is 0.075V, and the surface potential of the hole wall in the other region is designed to range from 0.015 to 0.075V, thus forming an axial non-uniform surface potential structure with high potential in the large hole section and low potential in the small hole section, or low potential in the large hole section and high potential in the small hole section.

7. The micro / nano channel ion thermoelectric control method based on axial step surface potential gradient according to claim 1, characterized in that: In step two, the three-part axial step surface potential structure divides the inner wall of the micro-nano channel into first, second and third surface potential regions along the axial direction. By arranging high, medium and low surface potentials in different ways, a multi-level axial step surface potential structure is constructed, and each region has a surface potential of high-end potential ψ1, middle-section potential ψ2 and high-end potential ψ3, respectively.

8. The micro / nano channel ion thermoelectric control method based on axial step surface potential gradient according to claim 7, characterized in that: In step two, the high-end potential is selected as 0.075V, the low-end potential is selected as 0.015V, and the middle potential is selected in the range of 0.015 to 0.075V.

9. The micro / nano channel ion thermoelectric control method based on axial step surface potential gradient according to claim 1, characterized in that: In step two, for the bipolar axial step surface potential structure, let the normalized axial distances from the surface potential boundary to the small hole end and the large hole end be L, respectively. n and L w Satisfying L n +L w =1, axial surface potential partition ratio λ p =L n / L w By changing the partition ratio, the effective range of the high and low surface potential regions along the channel axis is adjusted, where L n and L w The range is 0.1 to 0.9, and the partition ratio is λ. p The value was chosen as 0.

667.

10. The micro / nano channel ion thermoelectric control method based on axial step surface potential gradient according to claim 1, characterized in that: In step three, a temperature gradient is formed by setting a temperature difference at both ends of the micro-nano channel. The temperature at the high-temperature end is T0+ΔT, the temperature at the low-temperature end is T0, the reference temperature T0 is 293.15 Kelvin, and the temperature difference ΔT is designed to range from 0.5 to 10 Kelvin.

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