CN112162112B

CN112162112B - Flexible thermal convection acceleration sensor

Info

Publication number: CN112162112B
Application number: CN202011020481.4A
Authority: CN
Inventors: 谢建兵; 王修谱; 王一炜; 苑伟政
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2020-09-25
Filing date: 2020-09-25
Publication date: 2022-10-28
Anticipated expiration: 2040-09-25
Also published as: CN112162112A

Abstract

The invention discloses a flexible thermal convection acceleration sensor, and belongs to the technical field of sensors. The sensor comprises a four-layer structure from top to bottom, namely a flow guide layer 1, a middle partition plate 2, a bonding layer 3 and a flexible substrate layer 4; a heat insulation cavity 5 is formed in the center of the bonding layer 3; the heat conduction rate of the gas is far higher than that of the solid; the upper surface of the middle clapboard is pasted with a heater 6 and a pair of temperature sensing elements 7, and the lower surface is pasted with a heating compensation 8; and a horizontal through channel vertical to the temperature sensing element 7 is arranged in the flow guide layer 1, the height of the channel is the thickness of the flow guide layer, and openings at two ends of the channel are conical. The invention further improves the sensitivity of the thermal convection sensor on the basis of inheriting the advantages of the micro-mechanical thermal convection sensor.

Description

Flexible thermal convection acceleration sensor

Technical Field

The invention relates to a flexible thermal convection acceleration sensor, belongs to the technical field of sensors, and particularly relates to the field of flexible thermal convection acceleration sensors.

Background

An acceleration sensor is an inertial device used for measuring the motion acceleration of an object, and an MEMS (micro electro mechanical system) acceleration sensor is widely applied to the fields of automobile electronics, smart phones, earthquake monitoring, bionic biology and the like due to the advantages of small size, easiness in integration and the like. With the rapid development of technologies such as aerospace, wearable electronics, electronic display, and biosensing, the requirements for flexibility, ductility, and biocompatibility of the MEMS acceleration sensor are more and more prominent. Therefore, the research on the flexible acceleration sensor has important basic theoretical value and potential application prospect.

Conventional MEMS acceleration sensors typically require a proof mass. The existence of the mass block causes the sensor to have narrow measurement range, weak impact resistance and low reliability, and also causes the sensor to have larger size and higher processing cost. In order to solve the above problems, for example, chinese patent publication No. CN1161618C discloses a micro silicon bridge type thermal convection acceleration sensor, which includes a sealed cavity, a heating wire at the center of the cavity, two pairs of temperature sensors symmetrically disposed at two sides of the heating wire, and a bridge type temperature detection circuit composed of the two pairs of temperature sensors. The acceleration sensor detects acceleration information by adopting a heat convection principle, a heating wire at the center of a cavity is used as a heat source, a suspended hot air mass is generated in the cavity, when the acceleration is not acted, the temperature drop gradient is symmetrical about the center of the heat source, at the moment, the temperature difference between temperature sensors symmetrically arranged at two sides of the heating wire is zero, the profile of a thermal field can be disturbed by the acceleration in any direction due to the transmissibility of a free convection thermal field, so that the thermal field is asymmetrical, the output of the temperature sensors generated due to the induction temperature is different at the moment, and the difference is directly proportional to the induced acceleration. The thermal convection acceleration sensor has no mass block, and has the advantages of high measuring range, impact resistance and the like. However, since this type of thermal convection acceleration sensor uses silicon as a main material, it is inevitable to use a semiconductor processing process including photolithography, vapor deposition, plasma etching, and other processes, and it is difficult to reduce the manufacturing cost; on the other hand, the silicon-based device cannot meet the requirements of novel applications such as wearable equipment on the stretching and bending performance of the sensor. In order to overcome the above problems, for example, chinese patent publication No. CN106990262A discloses a thermal convection acceleration sensor, which includes a sealed cavity, a heating element, a plurality of temperature sensing elements, and a measuring circuit. The sealed cavity of the thermal convection acceleration sensor is prepared by injection molding, nano-imprinting or 3D printing of synthetic resin. The defects in the silicon-based process technology are overcome, the method has the advantages of simple manufacture and easy acquisition of materials, and the cost of the heat convection type acceleration sensor is greatly reduced. However, heat in the chamber is inevitably dissipated outwards through the cavity due to heat transfer between the sensor and the external environment, and the heat dissipation severely limits the sensitivity of the sensor, and the solution does not adapt to the application of the thermal convection acceleration sensor in the flexible field. Therefore, in order to ensure that the sensor has sufficient flexibility and further improve the sensitivity of the thermal convection acceleration sensor, a flexible thermal convection acceleration sensor is proposed herein.

Disclosure of Invention

The main object of the present invention is to overcome the above mentioned drawbacks of the prior art and to provide a flexible thermal convection acceleration sensor with high sensitivity.

The high-sensitivity flexible thermal convection acceleration sensor is characterized by comprising four layers of structures from top to bottom, namely a diversion layer 1, a middle partition plate 2, a bonding layer 3 and a flexible substrate layer 4, wherein the diversion layer 1, the middle partition plate 2, the bonding layer 3 and the flexible substrate layer 4 are respectively arranged on the four layers of structures; a through hole is formed in the center of the bonding layer 3, and the bonding layer and the upper and lower adjacent layers form a closed cavity, namely a heat insulation cavity 5; since the gas conduction rate is much higher than the solid conduction rate, the insulating cavity significantly reduces the rate at which heat is dissipated from the substrate. The upper surface of the middle partition board is pasted with a heater 6 and a pair of temperature sensing elements 7, the lower surface of the middle partition board is pasted with a heating compensation 8, wherein the heating compensation 8 is located in the center of the top of the heat insulation cavity, the heater 6 is located in the center of the upper surface of the middle partition board, the heater 6 and the heating compensation 8 are located in the same vertical plane, the temperature sensing elements 7 are symmetrically arranged relative to the heater 6, and the heater 6, the heating compensation 8 and the temperature sensing elements 7 are all of strip structures. The horizontal width of the heat insulation cavity 5 is not larger than the horizontal distance between the two temperature sensing elements 7, so that the temperature sensing elements 7 are not influenced by thermal convection in the heat insulation cavity 5. The flow guide layer 1 is internally provided with a horizontal through channel vertical to the temperature sensing element 7, the height of the channel is the thickness of the flow guide layer, openings at two ends of the channel are conical, the width of the channel in a conical area is gradually reduced from outside to inside to the minimum width, and the heater 6 and the temperature sensing element 7 are both positioned in the minimum width area of the channel. The tapered areas on both sides of the channel are flow guide grooves 9 which are used for increasing the gas flow speed in the minimum width area of the channel and improving the sensitivity of the sensor.

As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following advantages:

according to the flexible thermal convection acceleration sensor, the substrate is made of flexible metal materials or flexible organic materials such as polyimide and the like, and good bendability and ductility are achieved; a heat insulation cavity and heating compensation are arranged between the heater and the substrate, so that the heat loss of the heater is effectively reduced; the response speed and the sensitivity of the sensor are improved by arranging the diversion trench. The invention further improves the sensitivity of the thermal convection sensor on the basis of inheriting the advantages of the micro-mechanical thermal convection sensor.

The invention is further illustrated below with reference to figures and examples.

Drawings

FIG. 1 is a cross-sectional view of the present invention

FIG. 2 is an isometric view of the present invention

The device comprises a flow guide layer 1, a middle partition plate 2, a bonding layer 3, a flexible substrate layer 4, a heat insulation cavity 5, a heater 6, a temperature sensing element 7, a heating compensator 8, a flow guide groove 9 and an acceleration direction a.

Detailed Description

Referring to fig. 1 to 2, the present invention provides a flexible thermal convection acceleration sensor. Comprises four layers of structures from top to bottom, namely a diversion layer (1), a middle partition plate (2), a bonding layer (3) and a flexible substrate layer (4). In the embodiment, the overall size of the four-layer structure is 10mm multiplied by 2.8mm, wherein a through hole is formed in the center of the bonding layer, and the bonding layer and the upper layer and the lower layer form a closed cavity, namely a heat insulation cavity (5), and the size of the heat insulation cavity in the embodiment is 5mm multiplied by 1mm. The insulating cavity is filled with gas with low heat conductivity coefficient, such as air, in the embodiment, the gas is air, and the heat conductivity coefficient of the gas is far lower than that of the solid, so that the heat dissipation speed of the substrate is obviously reduced by the insulating cavity. The middle partition plate is provided with a heater (6) and a pair of temperature sensing elements (7) on the upper surface, and a heating compensation (8) on the lower surface, wherein the heating compensation is positioned in the center of the top in the heat insulation cavity, the heater is positioned in the center of the upper surface of the middle partition plate, the heater and the heating compensation are positioned in the same vertical plane, the temperature sensing elements are symmetrically arranged relative to the heater, the heating compensation and the temperature sensing elements are all of strip structures, in the embodiment, the heater adopts metal wires, the temperature sensing elements are thermistors, and the lengths of the metal wires and the thermistors are 8.6mm. (the horizontal width of the heat insulation cavity is slightly smaller than the horizontal distance between the two temperature sensing elements, in this case, the difference between the two temperature sensing elements is 0.3 mm), so that the temperature sensing elements are not influenced by the flow of hot air in the heat insulation cavity. The temperature-sensing sensor is characterized in that a horizontal through channel perpendicular to the temperature-sensing element is arranged in the flow guide layer, the height of the channel is the thickness of the flow guide layer, the thickness of the flow guide layer is 1mm, openings on two sides of the channel are conical, the width of the channel in a conical area is gradually reduced from outside to inside to the minimum width, the minimum width of the channel in the example is 6.6mm, the unilateral horizontal width of the conical area is 1.2mm, the conical degree is 45 degrees, the distance from the conical area to the side edge of the sensor is 0.7mm, and the heater and the temperature-sensing element are both located in the minimum width area of the channel. The conical areas on the two sides of the channel are diversion trenches (9) which are used for increasing the gas flow velocity in the minimum width area of the channel and improving the sensitivity of the sensor.

The flexible substrate is made of flexible organic materials such as PI or PMMA or flexible metal materials such as metal films, and the flexible substrate enables the sensor to be attached to the curved surface. The heat insulation cavity is formed by preparing a plurality of layers of flexible materials through modes such as nanoimprint lithography or 3D printing, air and other gases with low heat conductivity coefficient are filled in the heat insulation cavity, the dissipation speed of heat of the heater through the substrate is greatly reduced, the sensitivity of the thermal convection acceleration sensor is related to the power of the heater, the larger the power of the heater is, the higher the sensitivity of the sensor is, and therefore the reduction of the heat dissipation of the heater is beneficial to the improvement of the sensitivity of the sensor. The diversion trench is a groove which is gradually reduced from outside to inside, when acceleration acts, the motion state of the sensor is changed, due to the action of inertia, a local hot air mass generated by heating of the heater still keeps the original state, relative motion is generated between the hot air mass and the sensor firmware, and then heat convection is formed. The heating compensator is arranged at the center of the top of the heat insulation cavity, and can compensate the heat loss of the heater.

Claims

1. A flexible thermal convection acceleration sensor is characterized by comprising four layers of structures from top to bottom, namely a flow guide layer (1), a middle partition plate (2), a bonding layer (3) and a flexible substrate layer (4); the center of the bonding layer (3) is provided with a through hole, and the through hole and the upper and lower adjacent layers form a closed cavity, namely a heat insulation cavity (5); the upper surface of the middle partition board is adhered with a heater (6) and a pair of temperature sensing elements (7), the lower surface of the middle partition board is adhered with a heating compensation (8), the heating compensation (8) is located in the center of the top in the heat insulation cavity, the heater (6) is located in the center of the upper surface of the middle partition board, the heater (6) and the heating compensation (8) are located in the same vertical plane, the temperature sensing elements (7) are symmetrically arranged relative to the heater (6), and the heater (6), the heating compensation (8) and the temperature sensing elements (7) are all of strip structures; the horizontal width of the heat insulation cavity (5) is not more than the horizontal distance between the two temperature sensing elements (7), a horizontal through channel vertical to the temperature sensing elements (7) is arranged in the flow guide layer (1), and the height of the channel is the thickness of the flow guide layer; the flexible substrate layer (4) is made of flexible organic materials or flexible metal materials, and the flexible substrate layer (4) enables the sensor to be attached to a curved surface;

openings at two ends of a horizontal through channel arranged in the flow guide layer (1) are conical, the width of the channel in a conical area is gradually reduced from outside to inside to the minimum width, and the heater (6) and the temperature sensing element (7) are both positioned in the minimum width area of the channel; the conical areas at the two sides of the channel are guide grooves (9); the flow guide groove (9) is a groove gradually reduced from outside to inside, when acceleration acts, the motion state of the sensor is changed, a local hot air mass generated by heating the heater is still kept in an original state due to the action of inertia, relative motion is generated between the hot air mass and a sensor fixing part, and then heat convection is formed.