Capacitively coupled MEMS helium atom cell microfluidic channel integrated structure and packaging method

Abstract

The application belongs to the field of quantum sensors, and discloses a capacitive coupling MEMS helium atom gas chamber micro-flow channel integrated structure and a packaging method. The micro-flow channel and the gas chamber cavity are arranged in the glass substrate at the same time, and are arranged adjacently along the plane direction of the glass substrate and are separated by a glass partition wall. The integration of the fluid transport unit and the helium atom sensitive unit is realized. The structure can ensure that the fluid sample and the low-pressure helium gas are isolated, significantly shorten the distance between the fluid sample and the helium atom sensitive area, enable the weak magnetic field generated by the fluid sample to be coupled to the gas chamber cavity in close proximity, thereby reducing the attenuation of the magnetic signal during spatial propagation, and improving the detection sensitivity of the weak magnetic signal.

Description

Technical Field

[0001] This invention belongs to the field of quantum sensors, specifically relating to the integrated structure and packaging method of capacitively coupled MEMS helium atom gas chamber microfluidic channel. Background Technology

[0002] Helium atom magnetometers are quantum sensors that utilize the energy level structure and magnetic resonance effect of helium atoms to measure magnetic fields. They feature high sensitivity, wide dynamic range, good long-term stability, and no need for cryogenic refrigeration, making them applicable to fields such as current detection, biomagnetic measurement, geophysical exploration, nuclear magnetic resonance detection, and quantum precision measurement. As quantum sensing technology continues to evolve towards miniaturization, low power consumption, and high integration, chip-based helium atom magnetometers based on microelectromechanical systems (MEMS) technology have attracted widespread attention. Among these components, the helium atom chamber, as the core component for generating metastable helium atoms and sensing external magnetic fields, has its structure, manufacturing process, airtightness, and helium atom excitation method directly affecting the magnetometer's detection performance.

[0003] Existing helium atom chambers are typically manufactured using glass blowing, a process that makes it difficult to control the dimensional consistency and structural precision of the resulting chambers. This hinders device miniaturization, standardization, and mass production, and also makes them incompatible with microelectromechanical systems (MEMS) fabrication processes. Some miniature chambers are encapsulated using anodic bonding, adhesive bonding, or other methods, but these encapsulation methods may generate significant thermal stress and suffer from deterioration in sealing performance and leakage of low-pressure helium during long-term use, making it difficult to provide a long-term, reliable gas environment for the stable generation of metastable helium atoms.

[0004] In microfluidic NMR detection, biological sample analysis, and other scenarios involving the detection of weak magnetic signals, the fluid sample is typically transported via an independent microchannel or external tubing, while the helium atom chamber is housed within a separate sensor package. Because the fluid channel and the helium atom sensing element are manufactured and assembled separately, a significant spatial gap often exists between them. The magnetic field strength generated by the fluid sample rapidly decreases with increasing transmission distance. A large distance between the sample and the sensing element can easily weaken the effective magnetic signal, thereby reducing the sensitivity to weak magnetic fields.

[0005] Furthermore, existing helium atom magnetometers typically utilize radio frequency (RF) induction coils wound around the perimeter of the gas chamber to generate an RF electromagnetic field, thereby exciting low-pressure helium gas and producing metastable helium atoms. This excitation structure requires a large amount of external space, and the fabrication, winding, and installation of the coil are quite complex. As the size of the helium atom gas chamber shrinks further, it becomes difficult to simultaneously miniaturize and planarize the RF induction coil, hindering the integrated design of the gas chamber, excitation unit, and fluid detection unit, and also limiting the arraying and mass production of the device. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of existing technologies, such as the large magnetic signal coupling distance of the sample due to the separate setting of the helium atom chamber and the microchannel, the difficulty in miniaturizing and integrating the radio frequency induction coil, and the insufficient reliability of long-term sealing of low-pressure helium. The invention provides a capacitively coupled MEMS helium atom chamber microchannel integrated structure and packaging method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a capacitively coupled MEMS helium atom gas chamber microchannel integrated structure, comprising an upper glass window, a glass substrate and a lower glass window stacked sequentially, wherein the upper glass window and the lower glass window are respectively sealed to the glass substrate; The glass substrate contains microchannels and air chambers, which are arranged adjacent to each other along the plane of the glass substrate, and a glass partition wall is provided between the microchannels and the air chambers. The gas chamber is encapsulated with low-pressure helium. Capacitively coupled excitation electrodes corresponding to the positions of the gas chamber are respectively set on the outer surfaces of the upper and lower glass windows. The two capacitively coupled excitation electrodes are respectively connected to the radio frequency excitation circuit. The upper glass window is equipped with inlet and outlet holes for the flow channel, which are connected to the microchannel.

[0008] A further improvement of the present invention is that the air chamber includes an interconnected cylindrical main chamber and a cuboid extended chamber, and the axis of the cylindrical main chamber extends along the stacking direction of the upper glass window, the glass substrate and the lower glass window.

[0009] A further improvement of the present invention is that the diameter of the cylindrical main cavity is 6mm to 10mm, and the length of the cuboid extended cavity is 20mm to 40mm.

[0010] A further improvement of the present invention is that the microchannel has an elongated oval structure, which includes a straight section in the middle and semicircular sections connected to the two ends of the straight section in the middle, and the total length of the microchannel is 10mm to 20mm.

[0011] A further improvement of the present invention is that the inlet and outlet holes of the flow channel include a fluid inlet hole and a fluid outlet hole that are respectively connected to both ends of the microchannel, and the diameter of the fluid inlet hole and the fluid outlet hole is 5mm to 10mm.

[0012] A further improvement of the present invention is that each of the two capacitively coupled excitation electrodes is provided with a light-transmitting hole corresponding to the gas chamber cavity in the middle. The operating frequency of the radio frequency excitation circuit is 1MHz to 50MHz, the output voltage is 300V to 800V, and the pressure of helium gas in the gas chamber cavity is 200Pa to 500Pa.

[0013] A further improvement of the present invention is that the upper glass window, the glass substrate and the lower glass window are all made of BF33 borosilicate glass, the thickness of the glass partition wall is 1mm to 2mm, and the thickness of the upper glass window and the lower glass window is 0.5mm to 1mm.

[0014] Secondly, this invention provides a packaging method for a capacitively coupled MEMS helium atom gas chamber microchannel integrated structure, comprising the following steps: Prepare the upper glass wafer, the glass substrate wafer, and the lower glass wafer; Microchannels and gas chambers are formed within the glass substrate wafer, and inlet and outlet holes communicating with the microchannels are formed on the upper glass wafer. The processed upper glass wafer, glass substrate wafer, and lower glass wafer are cut to obtain the upper glass window, glass substrate, and lower glass window; Align the upper glass window with the glass substrate and weld the upper glass window to the glass substrate; The welded upper glass window and glass substrate are placed in the vacuum welding chamber, the vacuum welding chamber is evacuated, and pure helium gas at a predetermined pressure is filled into the gas chamber. Press the lower glass window firmly onto the lower surface of the glass substrate, and weld the lower glass window to the glass substrate.

[0015] A further improvement of this invention is that the microchannels and air chambers are formed by precision grinding; after cutting, the upper glass window, glass substrate and lower glass window are subjected to ultrasonic cleaning and surface cleaning treatment.

[0016] A further improvement of the present invention is that a pneumatic lifting platform is used to press the lower glass window tightly against the lower surface of the glass substrate, and the femtosecond laser passes through the upper or lower glass window and is focused on the corresponding glass contact interface; after the encapsulation is completed, capacitively coupled excitation electrodes are installed on the outer surfaces of the upper and lower glass windows respectively, and the capacitively coupled excitation electrodes are connected to the radio frequency excitation circuit.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention achieves integrated fluid transport unit and helium atom sensing unit by simultaneously incorporating microchannels and a gas chamber within a glass substrate, arranging them adjacently along the plane of the glass substrate and separated by a glass partition wall. This structure significantly shortens the distance between the fluid sample and the helium atom sensing region while ensuring isolation between the fluid sample and the low-pressure helium gas. This allows the weak magnetic field generated by the fluid sample to couple closely into the gas chamber, reducing attenuation of the magnetic signal during spatial propagation and improving the detection sensitivity of the weak magnetic signal. By setting capacitively coupled excitation electrodes on the outer surfaces of the upper and lower glass windows, the low-pressure helium gas within the gas chamber can be non-contactly excited using an alternating radio frequency electric field. This eliminates the need for a radio frequency induction coil outside the gas chamber, simplifying the excitation structure, reducing the space occupied by the device, and facilitating planarization, miniaturization, and integration. The upper glass window, glass substrate, and lower glass window form a stacked encapsulation structure, providing a relatively independent working space for the low-pressure helium gas and a stable fluid transport path for the microchannels. The upper glass window is equipped with inlet and outlet holes that communicate with the microchannel, facilitating connection to an external fluid delivery system and enabling continuous introduction, detection, and discharge of the fluid sample. Thus, this invention achieves a compact integration of the gas sensing unit, fluid channel, and radio frequency excitation structure, improving the device's magnetic field coupling capability, structural integration, and ease of application. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of an explosion of an integrated MEMS helium atom chamber and fluid channel structure based on capacitive coupling excitation. Figure 2 A schematic diagram of the process for fabricating and packaging a MEMS helium atom gas chamber; Figure 3 This is a schematic diagram illustrating an application scenario of a MEMS helium atom chamber.

[0019] The components include: 1. Upper glass window; 11. Flow channel inlet / outlet holes; 2. Glass substrate; 21. Microchannel; 22. Gas chamber; 3. Lower glass window; 4. Upper glass wafer; 5. Glass substrate wafer; 6. Lower glass wafer; 7. Femtosecond laser; 8. Vacuum welding chamber; 81. Ball valve; 82. Pneumatic lifting platform; 9. 1083 nm laser; 10. Optical path system; 12. MEMS gas chamber; 13. Capacitively coupled excitation electrode; 14. 1083 nm probe laser; 15. Photodetector; 16. Signal acquisition system. Detailed Implementation

[0020] To further understand the content of this invention, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the invention.

[0021] Example 1: like Figure 1 As shown, this embodiment provides a capacitively coupled MEMS helium atom gas chamber microchannel integrated structure, including an upper glass window 1, a glass substrate 2, and a lower glass window 3 stacked sequentially along the thickness direction. The upper glass window 1, the glass substrate 2, and the lower glass window 3 together form a three-layer glass encapsulation structure. The upper glass window 1 is sealed to the upper surface of the glass substrate 2, and the lower glass window 3 is sealed to the lower surface of the glass substrate 2.

[0022] The upper glass window 1, the glass substrate 2, and the lower glass window 3 are preferably made of BF33 borosilicate glass. BF33 borosilicate glass possesses high optical transmittance, good electrical insulation properties, low gas permeability, good chemical stability, and good compatibility with femtosecond laser welding, meeting the requirements for optical detection, capacitively coupled radio frequency excitation, and long-term hermetically sealed packaging in helium atom chambers. In other embodiments, glass materials with similar optical, electrical insulation, and welding properties can also be selected.

[0023] The thickness of both the upper glass window 1 and the lower glass window 3 is 0.5 mm to 1 mm. This thickness range can reduce the dielectric distance between the capacitively coupled excitation electrode 13 and the low-pressure helium gas in the gas chamber 22 while ensuring structural strength and airtightness, thereby reducing the coupling loss of the radio frequency electric field when passing through the glass window and facilitating the passage of the 1083 nm detection laser 14 through the upper glass window 1 and the lower glass window 3.

[0024] A microchannel 21 and a gas chamber 22 are disposed within a glass substrate 2, both formed by precision grinding. The microchannel 21 and the gas chamber 22 are located within the same glass substrate 2 and are arranged adjacent to each other along the plane of the glass substrate 2. Unremoved glass material is retained between the microchannel 21 and the gas chamber 22, forming a glass isolation wall. This glass isolation wall isolates the fluid sample within the microchannel 21 from the low-pressure helium gas within the gas chamber 22, preventing communication between the two media, while allowing the magnetic field generated by the fluid sample within the microchannel 21 to pass through the glass isolation wall and couple to the gas chamber 22.

[0025] The thickness of the glass isolation wall is preferably 1 mm to 2 mm. Setting the glass isolation wall to a thickness in the millimeter range can ensure sufficient mechanical strength and isolation reliability between the gas chamber 22 and the microchannel 21. On the other hand, it can shorten the distance between the fluid sample and the helium atom sensitive area, reduce the attenuation of the weak magnetic field as the spatial distance increases, and improve the near-field magnetic coupling efficiency between the magnetic signal of the fluid sample and the metastable helium atoms.

[0026] The microchannel 21 adopts an elongated oval structure, including a straight section in the middle and semi-circular sections connecting the two ends of the straight section. The total length of the microchannel 21 is 10mm to 20mm. The elongated oval structure can reduce local stagnation and eddies formed at the corners of the channel, allowing the fluid sample to flow continuously and smoothly within the detection area.

[0027] Two inlet / outlet holes 11 are provided on the upper glass window 1. One inlet / outlet hole 11 serves as the fluid inlet hole, and the other serves as the fluid outlet hole. The two inlet / outlet holes 11 are connected to both ends of the microchannel 21, and the diameters of the fluid inlet and outlet holes are both 5mm to 10mm. The inlet / outlet holes 11 can be connected to the fluid delivery system via connectors or external hoses, so that the fluid sample to be tested enters the microchannel 21 through the fluid inlet hole, flows through the magnetic signal detection area adjacent to the gas chamber 22, and then exits through the fluid outlet hole.

[0028] The lower glass window 3 does not have a through hole communicating with the microchannel 21, so that the lower side of the microchannel 21 remains closed. In other embodiments, the inlet and outlet holes 11 of the flow channel can also be set in the lower glass window 3, or respectively set in the upper glass window 1 and the lower glass window 3, depending on the fluid delivery direction and external connection requirements, as long as the communication between the microchannel 21 and the external fluid delivery system can be achieved.

[0029] The gas chamber 22 includes an interconnected cylindrical main cavity and a cuboid extension cavity. The axis of the cylindrical main cavity extends along the stacking direction of the upper glass window 1, the glass substrate 2, and the lower glass window 3, allowing the 1083nm probe laser 14 to pass through the gas chamber 22 along the axial direction of the cylindrical main cavity. The cylindrical main cavity is used to form the main optical detection area and the radio frequency discharge area, and its diameter is 6mm to 10mm.

[0030] The cuboid extension cavity is connected to the cylindrical main cavity, and the length of the cuboid extension cavity is 20mm to 40mm. The cuboid extension cavity is used to increase the effective discharge volume of the gas chamber cavity 22 and the diffusion space of metastable helium atoms. Compared with the gas chamber structure with only a cylindrical cavity, the gas chamber cavity 22 formed by the combination of the cylindrical main cavity and the cuboid extension cavity can increase the effective internal volume while maintaining a small device planar size and thickness, thereby increasing the number of metastable helium atoms participating in magnetic field detection and improving the spatial distribution uniformity of metastable helium atoms in the gas chamber cavity 22.

[0031] The gas chamber 22 is filled with low-pressure pure helium gas, and a permanently sealed low-pressure helium environment is formed by the upper glass window 1, the glass substrate 2, and the lower glass window 3. The helium pressure inside the gas chamber 22 can be from tens of Pascals to hundreds of Pascals, preferably 200 Pa to 500 Pa. This pressure range is beneficial for achieving breakdown discharge of low-pressure helium gas under the action of a radio frequency alternating electric field, and for generating metastable helium atoms with a long lifetime.

[0032] A capacitively coupled excitation electrode 13 is respectively disposed on the outer surface of the upper glass window 1 and the lower glass window 3. The two capacitively coupled excitation electrodes 13 correspond to the positions of the gas chamber cavity 22 and are respectively connected to the radio frequency excitation circuit. The capacitively coupled excitation electrodes 13 are attached to or deposited on the outer surface of the corresponding glass windows. The capacitively coupled excitation electrodes 13 do not directly contact the helium gas in the gas chamber cavity 22, but form a capacitive coupling structure with the low-pressure helium gas in the gas chamber cavity 22 through the upper glass window 1 and the lower glass window 3.

[0033] Both capacitively coupled excitation electrodes 13 have light-transmitting holes in their middle sections. These holes correspond to the cylindrical main cavity of the gas chamber 22 to prevent the capacitively coupled excitation electrodes 13 from blocking the 1083nm probe laser 14. The size of the light-transmitting holes can be determined based on the probe beam diameter, the optical path adjustment range, and the effective area of ​​the electrodes.

[0034] The operating frequency of the radio frequency (RF) excitation circuit is 1MHz to 50MHz, preferably 10MHz to 30MHz; the output voltage of the RF excitation circuit is 300V to 800V, preferably approximately 500V. After the RF excitation circuit applies a high-frequency AC voltage to the two capacitively coupled excitation electrodes 13, an alternating electric field is formed between the two capacitively coupled excitation electrodes 13. The alternating electric field couples through the upper glass window 1 and the lower glass window 3 into the interior of the gas chamber 22, causing the low-pressure helium gas inside the gas chamber 22 to undergo breakdown discharge and form plasma.

[0035] During the discharge process, free electrons in the helium gas gain energy under the influence of an alternating electric field and undergo inelastic collisions with helium atoms. Some helium atoms absorb the collision energy and transition from the ground state to an excited state, with some further entering longer-lived metastable energy levels, thus forming a metastable helium atom population within the gas chamber 22. The cuboid extension cavity provides additional diffusion space for the metastable helium atoms, allowing them to diffuse from the discharge region to other areas of the gas chamber 22, which helps improve the total amount and spatial uniformity of the metastable helium atoms.

[0036] This embodiment uses capacitive coupling excitation instead of the traditional radio frequency induction coil excitation method. Since it eliminates the need to build an excitation coil outside the helium atom gas chamber, it reduces the space occupied by the device and eliminates the need for micro-coil winding, mounting, and fixing. The capacitive coupling excitation electrode 13 can be mounted on the glass window surface using planar attachment, thin-film deposition, or patterning methods, facilitating the planarization, miniaturization, arraying, and mass production of the MEMS helium atom gas chamber.

[0037] Example 2: like Figure 2 As shown, this embodiment provides a method for fabricating and packaging a capacitively coupled MEMS helium atom gas chamber microchannel integrated structure, including the following steps: S1. Prepare the upper glass wafer 4, the glass substrate wafer 5, and the lower glass wafer 6. All three are made of BF33 borosilicate glass. Select the appropriate thickness of the glass wafer according to the device design dimensions, and perform a preliminary inspection of the glass wafer surface to remove materials with cracks, chipped edges, or surface defects.

[0038] S2, a microchannel 21 and a gas chamber 22 are formed within the glass substrate wafer 5 using a precision grinding process. When processing the gas chamber 22, a cylindrical main cavity and a cuboid extension cavity connected to the cylindrical main cavity are formed respectively; when processing the microchannel 21, an elongated oval channel structure with a straight section in the middle and semi-circular sections at both ends is formed, and a glass isolation wall with a thickness of 1mm to 2mm is retained between the microchannel 21 and the gas chamber 22.

[0039] During precision grinding, the feed rate and machining trajectory of the grinding tool are controlled according to the designed depth of the air chamber 22 and the microchannel 21, so that the air chamber 22 and the microchannel 21 penetrate the thickness of the glass substrate wafer 5, or can be closed by the upper glass window 1 and the lower glass window 3 respectively during subsequent packaging. Two flow channel inlet and outlet holes 11 are machined at corresponding positions on the upper glass wafer 4, so that the two flow channel inlet and outlet holes 11 correspond to the two ends of the microchannel 21 respectively.

[0040] S3 involves dicing the processed upper glass wafer 4, glass substrate wafer 5, and lower glass wafer 6. The dicing trajectory is set according to the outer contour of each individual device, dividing the wafer into multiple independent device units.

[0041] S4. Obtain the individual device structure and perform ultrasonic cleaning and surface cleaning on the cut upper glass window 1, glass substrate 2, and lower glass window 3. The cleaning process removes glass debris, grinding fluid residue, oil, and particulate contaminants generated during precision grinding and cutting. After cleaning, each glass component is dried to prevent moisture or contaminants from entering the gas chamber 22 and affecting low-pressure helium discharge and the generation of metastable helium atoms.

[0042] S5, align the upper glass window 1 with the glass substrate 2, so that the two flow channel inlet and outlet holes 11 correspond to the two ends of the microchannel 21 respectively, and make the upper glass window 1 completely cover the gas chamber cavity 22. After alignment, use a femtosecond laser 7 to complete the first surface welding between the upper glass window 1 and the glass substrate 2.

[0043] During welding, the femtosecond laser passes through the upper glass window 1 and is focused on the contact interface between the upper glass window 1 and the glass substrate 2. The femtosecond laser generates local nonlinear absorption at the glass contact interface, causing the glass material near the contact interface to partially melt and resolidify, thereby forming a continuous welded joint area. The femtosecond laser moves along a predetermined encapsulation trajectory around the gas chamber cavity 22 and the microfluidic channel 21, forming a permanent sealed connection between the upper glass window 1 and the glass substrate 2.

[0044] Femtosecond laser welding has a smaller heat-affected zone, which can reduce thermal stress and structural deformation caused by large-area heating, and avoid the volatilization, aging or contamination of the gas chamber cavity 22 by adhesive materials. After the first side is welded, the upper glass window 1 and the glass substrate 2 form a semi-enclosed structure, and the lower side of the gas chamber cavity 22 remains open.

[0045] S6, the semi-encapsulated structure with the first side welded is placed in the vacuum welding chamber 8. The vacuum welding chamber 8 is equipped with a ball valve 81 for controlling the vacuuming and filling processes. The vacuum welding chamber 8 is evacuated by an external vacuum system and the corresponding ball valve 81 to remove air, water vapor and other residual gases from the vacuum welding chamber 8 and the gas chamber 22.

[0046] During the vacuuming process, the predetermined evacuation time can be maintained according to the working pressure requirements after packaging, so that the inside of the gas chamber 22 reaches a vacuum state that meets the requirements for pure helium filling. The vacuuming process reduces the content of impurity gases such as oxygen, nitrogen, and water vapor in the gas chamber 22, avoiding the impact of impurity gases on the stability of helium discharge, metastable helium atom lifetime, and optical detection performance.

[0047] S7. Once the vacuum level in the vacuum welding chamber 8 reaches the preset requirement, high-purity helium gas at a predetermined pressure is introduced into the vacuum welding chamber 8 and the gas chamber 22 through the ball valve 81. The helium pressure is from tens to hundreds of Pascals, preferably controlled between 200 Pa and 500 Pa. After the filling is completed, the helium pressure in the vacuum welding chamber 8 is kept stable, so that a pure helium environment at a predetermined pressure is formed inside the gas chamber 22.

[0048] S8, the lower glass window 3 is placed on the lower surface of the glass substrate 2, and the lower glass window 3 is pushed vertically by the pneumatic lifting platform 82 to make the lower glass window 3 fit tightly against the lower surface of the glass substrate 2. Under the condition that the pneumatic lifting platform 82 is kept in a pressed state and the predetermined helium pressure is maintained in the gas chamber 22, the femtosecond laser 7 is used to complete the second-side welding between the lower glass window 3 and the glass substrate 2.

[0049] During the second welding, the femtosecond laser passes through the lower glass window 3 and focuses on the contact interface between the lower glass window 3 and the glass substrate 2. The femtosecond laser scans along the predetermined welding trajectory, forming a continuous and sealed connection between the lower glass window 3 and the glass substrate 2. After the second welding is completed, the gas chamber 22 is completely sealed by the upper glass window 1, the glass substrate 2, and the lower glass window 3, thereby permanently sealing pure helium gas at a predetermined pressure within the gas chamber 22.

[0050] After completing the hermetically sealed assembly, two capacitively coupled excitation electrodes 13 are respectively installed on the outer surfaces of the upper glass window 1 and the lower glass window 3, aligning the capacitively coupled excitation electrodes 13 with the cylindrical main cavity of the gas chamber 22. Subsequently, the two capacitively coupled excitation electrodes 13 are connected to the radio frequency excitation circuit, and the inlet / outlet holes 11 of the flow channel are connected to the fluid delivery system via external hoses, thereby completing the assembly of the capacitively coupled MEMS helium atom gas chamber microfluidic integrated device.

[0051] like Figure 2 As shown, the entire fabrication and packaging process can be represented as follows: structural processing is completed on the upper glass wafer 4, the glass substrate wafer 5, and the lower glass wafer 6; the wafers are cut to obtain individual devices; the first side is welded using a femtosecond laser 7; the semi-packaged device is placed into the vacuum welding chamber 8; vacuuming and helium filling are completed using a ball valve 81; the lower glass wafer 6 is pressed using a pneumatic lifting platform 82; and finally, the second side is welded and packaged using a femtosecond laser 7.

[0052] Example 3: like Figure 3 As shown, this embodiment provides a magnetic signal detection application method for the above-described integrated structure. The packaged MEMS gas chamber 12 is disposed in the optical detection path. The MEMS gas chamber 12 includes a helium atom sensitive region formed by the gas chamber cavity 22 and a microchannel 21 disposed adjacent to it.

[0053] A 1083nm laser 9 emits a probe beam, which is collimated, shaped, and its propagation direction adjusted by the optical path system 10 to form a 1083nm probe laser 14. The 1083nm probe laser 14 passes sequentially through the light-transmitting aperture of the upper capacitively coupled excitation electrode 13, the upper glass window 1, the metastable helium atom region in the gas chamber 22, the lower glass window 3, and the light-transmitting aperture of the lower capacitively coupled excitation electrode 13.

[0054] The radio frequency excitation circuit applies a high-frequency AC voltage to the two capacitively coupled excitation electrodes 13, causing the low-pressure helium gas in the gas chamber 22 to discharge and generate a metastable helium atom population. The 1083nm probe laser 14 interacts optically with the metastable helium atoms, and the absorption, transmission, or polarization characteristics of the metastable helium atoms with respect to the 1083nm probe laser 14 change with the external magnetic field.

[0055] Driven by an external fluid delivery system, the fluid sample to be tested enters the microchannel 21 through the fluid inlet orifice and flows along the microchannel 21 through the detection area adjacent to the gas chamber 22. The weak magnetic field generated by the magnetized particles, spin system, or electric current in the fluid sample passes through the glass isolation wall and acts on the metastable helium atom population in the gas chamber 22.

[0056] An external magnetic field alters the energy level structure and magnetic resonance state of metastable helium atoms, thereby changing their absorption, transmission, or polarization response to the 1083nm probe laser 14. The probe light passing through the MEMS gas chamber 12 is received by a photodetector 15, which converts the optical signal into an electrical signal and transmits it to the signal acquisition system 16.

[0057] The signal acquisition system 16 amplifies, filters, acquires and processes the electrical signal output by the photodetector 15, and obtains the corresponding magnetic field information based on the changes in transmitted light intensity, polarization state or other optical response parameters, thereby realizing the detection of the magnetic signal of the fluid sample in the microchannel 21.

[0058] This invention places the gas chamber 22 and the microchannel 21 within the same glass substrate 2, separated by a glass isolation wall with a thickness of 1 mm to 2 mm, maintaining a millimeter-level distance between the fluid sample and the metastable helium atom sensitive region. Compared to methods that separately encapsulate the gas chamber and fluid channel and assemble them through external structures, this invention reduces the gaps caused by intermediate encapsulation layers, support structures, and external pipelines, thereby improving the near-field coupling strength of the magnetic signal of the fluid sample.

[0059] This invention employs a combination of a cylindrical main cavity and a cuboid extended cavity to form a gas chamber 22. The cylindrical main cavity provides a relatively concentrated working area for optical detection and radio frequency discharge, while the cuboid extended cavity increases the low-pressure helium gas volume and the diffusion space for metastable helium atoms. This combined gas chamber structure can balance chip size, detection optical path arrangement, effective discharge volume, and the number of metastable helium atoms.

[0060] This invention employs femtosecond laser welding to connect the upper glass window 1, the glass substrate 2, and the lower glass window 3. Compared to anodic bonding or adhesive encapsulation, femtosecond laser welding eliminates the need for high-temperature heating across the entire device, resulting in a smaller heat-affected zone. Furthermore, it eliminates the need to introduce organic adhesives into the encapsulation interface, thereby reducing thermal stress and the risk of gas chamber contamination, and improving the long-term retention capability of low-pressure helium.

[0061] The present invention uses a capacitively coupled excitation electrode 13 disposed on the outer surface of a glass window to excite low-pressure helium gas. The electrode and the helium gas are isolated by a glass medium. It is not necessary to introduce a metal electrode into the gas chamber cavity 22, nor is it necessary to set a radio frequency induction coil outside the gas chamber. This is beneficial to simplify the packaging structure and improve the miniaturization and integration of the device.

[0062] The integrated structure formed by this invention can be applied to chip-based helium atom magnetometers, microfluidic nuclear magnetic resonance detection, biomagnetic detection, weak current magnetic field detection, quantum precision measurement, laboratory-on-a-chip systems, and other application scenarios that require near-field weak magnetic detection of trace fluid samples.

[0063] In one specific embodiment, the thickness of both the upper glass window 1 and the lower glass window 3 is set to 0.8 mm, the diameter of the cylindrical main cavity is set to 8 mm, the length of the cuboid extended cavity is set to 30 mm, the total length of the microchannel 21 is set to 15 mm, the aperture of both inlet and outlet holes 11 of the two channels is set to 6 mm, and the thickness of the glass isolation wall is set to 1.5 mm. The gas chamber 22 is filled with high-purity helium gas at a pressure of 300 Pa, the operating frequency of the radio frequency excitation circuit is set to 20 MHz, and the output voltage is set to 500 V.

[0064] Under the aforementioned parameters, the radio frequency excitation circuit generates an alternating electric field within the gas chamber 22 through two capacitively coupled excitation electrodes 13, causing a stable discharge of 300 Pa low-pressure helium gas and generating a metastable helium atom population. A 1083 nm probe laser 14 passes through the cylindrical main cavity, and the fluid sample flows continuously within adjacent microchannels 21. The magnetic field generated by the fluid sample acts on the metastable helium atoms through a 1.5 mm thick glass isolation wall. A photodetector 15 receives the transmitted light and outputs an electrical signal. The signal acquisition system 16 processes this electrical signal to obtain the magnetic signal of the fluid sample under test.

[0065] In another specific embodiment, the diameter of the cylindrical main cavity is set to 6 mm, the length of the cuboid extended cavity is set to 20 mm, the total length of the microchannel 21 is set to 10 mm, the thickness of the glass isolation wall is set to 1 mm, the helium pressure in the gas chamber 22 is set to 200 Pa, the radio frequency excitation frequency is set to 10 MHz, and the radio frequency excitation voltage is set to 300 V. This embodiment is suitable for detection scenarios with small device size requirements and small sample volume.

[0066] In another specific embodiment, the diameter of the cylindrical main cavity is set to 10 mm, the length of the cuboid extended cavity is set to 40 mm, the total length of the microchannel 21 is set to 20 mm, the thickness of the glass isolation wall is set to 2 mm, the helium pressure inside the gas chamber 22 is set to 500 Pa, the radio frequency excitation frequency is set to 30 MHz, and the radio frequency excitation voltage is set to 800 V. This embodiment has a large effective gas chamber volume and metastable helium atom diffusion space, making it suitable for applications requiring increased effective atom count and detection area length.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A capacitively coupled MEMS helium atom gas chamber microchannel integrated structure, characterized in that, It includes an upper glass window (1), a glass substrate (2) and a lower glass window (3) arranged in sequence, with the upper glass window (1) and the lower glass window (3) respectively sealed to the glass substrate (2); A microchannel (21) and an air chamber (22) are provided inside the glass substrate (2). The microchannel (21) and the air chamber (22) are arranged adjacent to each other along the plane direction of the glass substrate (2). A glass isolation wall is provided between the microchannel (21) and the air chamber (22). The gas chamber (22) is encapsulated with low-pressure helium gas. The outer surfaces of the upper glass window (1) and the lower glass window (3) are respectively provided with capacitively coupled excitation electrodes (13) corresponding to the positions of the gas chamber (22). The two capacitively coupled excitation electrodes (13) are respectively connected to the radio frequency excitation circuit. The upper glass window (1) is provided with a flow channel inlet and outlet hole (11) that communicates with the microchannel (21).

2. The capacitively coupled MEMS helium atom gas chamber microchannel integrated structure according to claim 1, characterized in that, The air chamber (22) includes a cylindrical main chamber and a cuboid extension chamber that are interconnected. The axis of the cylindrical main chamber extends along the stacking direction of the upper glass window (1), the glass substrate (2) and the lower glass window (3).

3. The capacitively coupled MEMS helium atom gas chamber microchannel integrated structure according to claim 2, characterized in that, The diameter of the cylindrical main cavity is 6mm to 10mm, and the length of the cuboid extended cavity is 20mm to 40mm.

4. The capacitively coupled MEMS helium atom gas chamber microchannel integrated structure according to claim 1, characterized in that, The microchannel (21) has an elongated oval structure, which includes a straight section in the middle and semicircular sections connected to the two ends of the straight section in the middle. The total length of the microchannel (21) is 10 mm to 20 mm.

5. The capacitively coupled MEMS helium atom gas chamber microchannel integrated structure according to claim 1, characterized in that, The inlet and outlet holes (11) of the flow channel include a fluid inlet hole and a fluid outlet hole that are respectively connected to both ends of the microchannel (21). The diameter of the fluid inlet hole and the fluid outlet hole is 5mm to 10mm.

6. The capacitively coupled MEMS helium atom gas chamber microchannel integrated structure according to claim 1, characterized in that, The two capacitively coupled excitation electrodes (13) are provided with light-transmitting holes corresponding to the gas chamber cavity (22) in the middle. The operating frequency of the radio frequency excitation circuit is 1MHz to 50MHz, the output voltage is 300V to 800V, and the pressure of helium gas in the gas chamber cavity (22) is 200Pa to 500Pa.

7. The capacitively coupled MEMS helium atom gas chamber microchannel integrated structure according to claim 1, characterized in that, The upper glass window (1), the glass substrate (2) and the lower glass window (3) are all made of BF33 borosilicate glass. The thickness of the glass partition wall is 1mm to 2mm, and the thickness of the upper glass window (1) and the lower glass window (3) is 0.5mm to 1mm.

8. A packaging method for the capacitively coupled MEMS helium atom gas chamber microchannel integrated structure according to any one of claims 1 to 7, characterized in that, Includes the following steps: Prepare the upper glass wafer, the glass substrate wafer, and the lower glass wafer; Microchannels (21) and gas chambers (22) are formed in the glass substrate wafer, and inlet and outlet holes (11) communicating with the microchannels (21) are formed on the upper glass wafer. The processed upper glass wafer, glass substrate wafer and lower glass wafer are cut to obtain the upper glass window (1), glass substrate (2) and lower glass window (3). Align the upper glass window (1) with the glass substrate (2) and weld the upper glass window (1) to the glass substrate (2); The welded upper glass window (1) and glass substrate (2) are placed in the vacuum welding chamber, the vacuum welding chamber is evacuated, and pure helium gas at a predetermined pressure is filled into the gas chamber cavity (22). Press the lower glass window (3) against the lower surface of the glass substrate (2) and weld the lower glass window (3) to the glass substrate (2).

9. The packaging method for the capacitively coupled MEMS helium atom gas chamber microchannel integrated structure according to claim 8, characterized in that, The microchannel (21) and the air chamber (22) are formed by precision grinding. After cutting, the upper glass window (1), the glass substrate (2) and the lower glass window (3) are ultrasonically cleaned and surface cleaned.

10. The packaging method for the capacitively coupled MEMS helium atom gas chamber microchannel integrated structure according to claim 8, characterized in that, A pneumatic lifting platform is used to press the lower glass window (3) against the lower surface of the glass substrate (2). The femtosecond laser passes through the upper glass window (1) or the lower glass window (3) and is focused on the corresponding glass contact interface. After the encapsulation is completed, capacitively coupled excitation electrodes (13) are installed on the outer surfaces of the upper glass window (1) and the lower glass window (3), respectively, and the capacitively coupled excitation electrodes (13) are connected to the radio frequency excitation circuit.

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