A microballoon integrating a stretchable stimulation electrode and pressure sensor array and a method thereof

Abstract

This invention discloses a method for integrating a stretchable stimulating electrode and a pressure sensor array into a microsphere. The method comprises the following steps: First, photoresist is processed using photolithography to obtain a pressure sensor substrate layer; second, a pressure sensor sensitive layer is obtained using sputtering and dry etching; third, a pressure sensor encapsulation layer is obtained using photolithography; fourth, a conductive layer for the stimulating electrode is obtained using sputtering and dry etching; fifth, the stimulating electrode encapsulation layer is obtained using photolithography; sixth, the prepared stimulating electrode and pressure sensor array are released from the silicon wafer using a wet etching process; seventh, the stimulating electrode and pressure sensor array are transferred from the silicon wafer surface using water-soluble adhesive tape; and eighth, the integration process of the stimulating electrode, pressure sensor array, and microsphere is performed. This method ensures that the stimulating electrode and pressure sensor array deform synchronously with the expansion or contraction of the microsphere, meeting the requirements for electrical stimulation and in-situ monitoring of pressure at the stimulating electrode sites.

Description

Technical Field

[0001] This invention belongs to the field of biomedical electrotechnology, specifically relating to a microballoon-integrated array of extendable stimulation electrodes and pressure sensors, and a method thereof. Background Technology

[0002] With the development of flexible electronic device technology, some studies have reported the integration of functional balloon devices for cardiac diagnosis and treatment. By integrating sensors and electrodes on the balloon surface and connecting them to external signal acquisition or signal generation devices through interface technology, functions such as electrocardiogram monitoring, temperature sensing, and electrical stimulation can be achieved.

[0003] A search of existing technologies revealed that in 2011, the DHKim team published an article in *Nature Materials*, 2011, 10(4):316-323, entitled "Materials for multifunctional balloon catheters with capabilities in cardiac electrophysiological mapping and ablation therapy," proposing a multifunctional balloon device with cardiac electrophysiological monitoring and ablation therapy functions. The balloon device includes a pressure sensor array, a temperature sensor array, an electrode array, and a balloon catheter. The electrodes and serpentine interconnect structure are drawn on a uniform PI film surface. The pressure sensor array, after obtaining the PSR-sensitive bridge structure through photolithography and molding, is integrated between two metal pads on the PI film. This is used to monitor the pressure at the balloon-heart interface. However, in this application, the pressure sensor is a three-dimensional sensitive structure, resulting in high space utilization.

[0004] In 2019, Liu Jingquan's team at Shanghai Jiao Tong University published a paper titled "Flexible Multi-Positional Microsensors for Cryoablation Temperature Monitoring" in IEEE Electron Device Letters, 2019, 40(10):1674-1677. This paper proposed a Parylene-C substrate flexible blood flow sensor with a large-size balloon surface integrating a serpentine wire structure for cryoablation temperature monitoring. The balloon device comprises a microballoon, stretchable electrodes, and a heat-based blood flow sensor, providing hemodynamic information, electrical stimulation, and ablation therapy functions on a single device. The surface electrodes of the balloon device have a wavy geometry, and the flow sensor consists of a thermistor and a heating element, with insulation and support provided by two polyimide overlay layers. The thickness of the metal layer is carefully designed to simultaneously support sensing and radiofrequency stimulation. The polyimide layer is patterned using laser. However, this balloon device is suitable for large-size applications, and the accuracy requirements for the electrodes and blood flow sensing structure are relatively low.

[0005] In 2020, John A. Rogers' team published an article in *Nature Biomedical Engineering*, 2020, 4(10): 997-1009, entitled "Catheter-integrated soft multilayer electronic arrays for multiplexed sensing and actuation during cardiac surgery." This invention integrates stimulation electrodes and pressure sensors on the surface of a large-sized balloon catheter to detect electrical signals in the endocardium and ablate a portion of the myocardial tissue through local heating, achieving treatment of arrhythmia and simultaneous pressure detection. The balloon material used is low-elasticity polyurethane, exhibiting minimal elastic deformation during inflation and deflation, and primarily exhibiting a collapsed or wrinkled shape after deflation, thus requiring less flexibility in the integrated flexible electrodes. However, this balloon device has a three-dimensional pressure cavity structure, suitable for integration in large spaces, but not for microballoon integration.

[0006] CN109223169A discloses a pulmonary vein electrical isolation balloon structure, which includes a first balloon, a second balloon, and a balloon catheter. The first balloon is a cryoballoon, and the surface of the second balloon is provided with several electrodes. The second balloon is located at the front end. The balloon catheter includes a channel that respectively connects the first balloon and the second balloon and an electrode connecting wire that connects the electrodes. However, when the thin electrode connecting wire is directly bonded to the catheter, it is difficult to ensure the reliability of the bonding.

[0007] CN115778522A discloses an ablation catheter and ablation system. The ablation catheter includes a catheter body, a transducer, and multiple wires electrically connected to the transducer. An external electrode is disposed on the outer wall of the transducer body, and an internal electrode is disposed on the inner wall of the transducer body. Each electrode region is electrically connected to the external electrode wires, and these electrode regions are arranged in parallel, allowing for independent control of multiple electrode regions. The ablation is then performed on the lesion site through a focal point, resulting in high ablation efficiency and minimal damage to the human body. However, this device has low system integration and limited balloon expansion, offering limited experience for the development of precision balloon devices.

[0008] The above-mentioned multifunctional balloon-based devices achieve multiple functions with a single device, but they have the following limitations: First, the functional devices are independently distributed, resulting in low system integration and low space utilization. Second, the balloons are mainly small-expansion balloons, and the interconnecting wires of their functional devices are mostly straight, with limited extensibility. Finally, the integration of functional devices with the balloon interface only requires ensuring integration strength; the extensibility and other properties of the elastic adhesive are not critical, thus limiting their applicability to specific application scenarios. Summary of the Invention

[0009] To overcome the shortcomings of existing technologies, this invention provides a microsphere-integrated stretchable stimulating electrode and pressure sensor array, and a method thereof, aiming to fabricate a multifunctional flexible device in which the stimulating electrode and pressure sensor array are vertically stacked and integrated on the surface of the microsphere. The steps are as follows: First, photoresist is processed using photolithography to obtain the pressure sensor substrate layer; second, the pressure sensor sensitive layer is obtained using sputtering and dry etching; third, the pressure sensor encapsulation layer is obtained using photolithography; fourth, the conductive layer of the stimulating electrode is obtained using sputtering and dry etching; fifth, the photoresist is patterned using photolithography to obtain the stimulating electrode encapsulation layer; sixth, the prepared stimulating electrode and pressure sensor array are released from the silicon wafer using a wet etching process; seventh, the stimulating electrode and pressure sensor array are transferred from the silicon wafer surface using water-soluble adhesive tape; and eighth, the integration process of the stimulating electrode, pressure sensor array, and microsphere is performed. This process ensures that the stimulation electrode and the pressure sensor array deform synchronously with the expansion or contraction of the microballoon, meeting the requirements for electrical stimulation and in-situ monitoring of the pressure at the stimulation electrode site. It can also quantitatively express the degree of deformation of the microballoon after expansion and contact with nerve tissue, and provide a closed-loop evaluation function for discharge stimulation.

[0010] The technical solution adopted by this invention to solve its technical problem is as follows:

[0011] A microballoon-integrated array of extendable stimulating electrodes and pressure sensors includes a balloon catheter, a pressure sensor, stimulating electrodes, a device tail pad, and a large-extension wire.

[0012] The balloon catheter includes a metal end, a microballoon, and a support tube; each end of the microballoon is connected to a metal end, and one of the metal ends is then connected to the support tube.

[0013] The device's tail pad is integrated on a metal end or support tube and is connected to a pressure sensor and a stimulation electrode via a long-extension wire; the device's tail pad is also connected to an external device.

[0014] The multiple pressure sensors and stimulation electrodes are integrated on the surface of the microsphere to form an array of stimulation electrodes and pressure sensors.

[0015] Furthermore, the number of pressure sensors and stimulation electrodes are the same, and they are stacked in the vertical direction to form a pressure sensor and stimulation electrode module.

[0016] The pressure sensor includes a pressure sensor encapsulation layer, a pressure sensor sensitive layer, and a pressure sensor encapsulation layer; the stimulation electrode includes a stimulation electrode encapsulation layer, a stimulation electrode conductive layer, and a pressure sensor encapsulation layer; the pressure sensor encapsulation layer serves as both the encapsulation layer of the pressure sensor and the substrate layer of the stimulation electrode.

[0017] The pressure sensor and stimulation electrode module, from top to bottom, consist of a stimulation electrode encapsulation layer, a stimulation electrode conductive layer, a pressure sensor encapsulation layer, a pressure sensor sensitive layer, and a pressure sensor substrate layer. The pressure sensor and stimulation electrode module are integrated on the surface of the microsphere using an elastic adhesive, enabling the stimulation electrode and pressure sensor array to expand synchronously with the microsphere.

[0018] Furthermore, the pressure-sensitive structure in the pressure sensor sensitive layer includes a pressure sensor signal terminal and a pressure sensor ground terminal; the pressure sensor ground terminal is grounded, and the pressure sensor signal terminal is connected to an external circuit; when the pressure sensor is subjected to force, the inter-electrode capacitance changes, and the corresponding electrical signal is collected and analyzed to finally obtain the corresponding pressure value.

[0019] Furthermore, the materials of the stimulation electrode encapsulation layer, the pressure sensor encapsulation layer, and the pressure sensor substrate layer are polymer thin film materials.

[0020] Furthermore, the polymer film material is polyimide (PI), polyethylene terephthalate (PET), or parylene, with a thickness of 3-7 μm.

[0021] Furthermore, the material of the conductive layer of the stimulation electrode is gold, platinum, or a platinum-iridium alloy; the material of the sensitive layer of the pressure sensor is silver or platinum.

[0022] Furthermore, there are 9 pressure sensors and stimulation electrode modules, arranged in groups of 3, with each group arranged in a straight line along the axis of the balloon catheter; the 3 groups are evenly distributed axially at 120° intervals on the upper half of the microballoon surface away from the device tail pad, forming an array of stimulation electrodes and pressure sensors.

[0023] A method for fabricating a microsphere-integrated stretchable stimulation electrode and pressure sensor array includes the following steps:

[0024] Step 1: Cover one side of the silicon-aluminum alloy aluminum sheet with photoresist material, and use photolithography to pattern the photoresist material to obtain the pressure sensor substrate layer;

[0025] Step 2: Metal is deposited on the surface of the pressure sensor substrate using a sputtering process, and the metal is patterned using a dry etching process to obtain the pressure sensor sensitive layer;

[0026] Step 3: Cover the pressure sensor sensitive layer with photoresist material, and use photolithography to pattern the photoresist material to obtain the pressure sensor encapsulation layer, exposing the device tail pad structure;

[0027] Step 4: Metal is deposited on the surface of the pressure sensor packaging layer using a sputtering process, and the metal is patterned using a dry etching process to obtain the conductive layer of the stimulation electrode.

[0028] Step 5: Cover the conductive layer of the stimulation electrode with photoresist material, and use photolithography to pattern the photoresist to obtain the stimulation electrode encapsulation layer, exposing the device tail pad structure;

[0029] Step 6: Use a wet etching process to etch the aluminum sheet, releasing the prepared stimulation electrode and pressure sensor module from the silicon wafer;

[0030] Step 7: Use water-soluble tape to remove the stimulation electrode and pressure sensor module from the silicon wafer surface;

[0031] Step 8: Use a flexible adhesive to attach the stimulation electrode and pressure sensor module to the surface of the microsphere, remove the water-soluble tape, and expose the pads at the end of the device.

[0032] Furthermore, in step 7, after the stimulation electrode and pressure sensor module are transferred from the silicon wafer surface, water-soluble adhesive tape is used to first transfer the stimulation electrode and pressure sensor module to the surface of a flexible substrate, and then step 8 is performed.

[0033] Furthermore, after step 8 is completed, a layer of sealing material is sprayed or drop-coated onto the surface of the microsphere to improve the reliability of the integration of the stimulation electrode with the pressure sensor array and the microsphere.

[0034] The beneficial effects of this invention are as follows:

[0035] 1. High space utilization. The stimulation electrodes and pressure sensor array are vertically stacked and integrated in situ on the surface of the microsphere, which greatly improves space utilization and meets the requirement of simultaneous electrical stimulation and in-situ monitoring of the pressure at the stimulation electrode interface.

[0036] 2. Strong flexibility and adaptability. The interconnecting wires adopt a serpentine wire form, which can adapt to situations where there is a need for large deformation in a small space. It is more adaptable to situations where the flexibility requirements of flexible array devices integrated on the surface of a balloon are high.

[0037] 3. High integration reliability. When the stimulation electrode and pressure sensor array are integrated from a two-dimensional plane onto the surface of the curved microsphere, the relative positional misalignment between the large-extension wires caused by transfer printing can be effectively avoided. This allows the stimulation electrode and pressure sensor array to expand synchronously with the microsphere and maintain conformal contact, ensuring high integration reliability. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the extendable stimulation electrode and pressure sensor array integrated on the surface of the balloon catheter according to the present invention.

[0039] Figure 2 This is a schematic diagram of the location of the device array on the balloon surface of the present invention and a schematic diagram of the cross-sectional structure of any device site.

[0040] Figure 3 This is a schematic diagram of the layered structure of the stimulation electrode and pressure sensor array of the present invention.

[0041] Figure 4 This is a flowchart illustrating the fabrication and integration process of the stimulation electrode and pressure sensor array of the present invention.

[0042] Figure 5 This is a flowchart illustrating the fabrication process of the stimulation electrode and pressure sensor array in Embodiment 2 of the present invention.

[0043] Figure 6 This is a flowchart illustrating the fabrication process of the stimulation electrode and pressure sensor array in Embodiment 3 of the present invention.

[0044] The markings in the diagram represent: 1. Balloon catheter; 2. Metal end; 3. Pressure sensor; 4. Stimulating electrode; 5. Microballoon; 6. Support tube; 7. Device tail pad; 8. Large extension wire; 9. Stimulating electrode encapsulation layer; 10. Stimulating electrode conductive layer; 11. Pressure sensor encapsulation layer; 12. Pressure sensor sensitive layer; 13. Pressure sensor substrate layer; 14. Elastic adhesive; 15. Pressure sensor signal terminal; 16. Pressure sensor ground terminal. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0046] To address the deficiencies and gaps in existing technologies, this invention provides a process method for integrating a stretchable stimulation electrode and a pressure sensor array into a microballoon. This method has practical and innovative value in improving the reliability of integrating pressure sensors and stimulation electrodes on the surface of a microballoon, and can effectively solve the shortcomings of low integration of functional devices, low space utilization, high stretchability, and poor reliability of microballoon interface integration.

[0047] This design primarily involves a fabrication method for integrating a stretchable stimulating electrode and a pressure sensor array into a microsphere. The fabrication process utilizes MEMS technology for layer-by-layer fabrication, resulting in high efficiency. The integration process employs water-soluble adhesive tape to transfer the stimulating electrode and pressure sensor array onto the surface of the microsphere coated with an elastic adhesive, achieving conformal contact. The elastic adhesive is then used for reliable integration, enabling the stimulating electrode and pressure sensor array to expand synchronously with the microsphere.

[0048] A microballoon-integrated array of extendable stimulation electrodes and pressure sensors includes a balloon catheter 1, a pressure sensor 3, a stimulation electrode 4, a device tail pad 7, and a large-extension wire 8.

[0049] The balloon catheter 1 includes a metal end 2, a microballoon 5, and a support tube 6; each end of the microballoon 5 is connected to a metal end 2, and one of the metal ends 2 is then connected to the support tube 6.

[0050] The device's tail pad 7 is integrated on the metal end 2 or the support tube 6, and is connected to the pressure sensor 3 and the stimulation electrode 4 respectively through a large extension wire 8; the device's tail pad 7 is also connected to external devices.

[0051] The multiple pressure sensors 3 and stimulation electrodes 4 are integrated on the surface of the microsphere 5 to form an array of stimulation electrodes and pressure sensors.

[0052] The pressure sensors 3 and stimulation electrodes 4 are the same in number and are stacked in the vertical direction to form a pressure sensor and stimulation electrode module.

[0053] The pressure sensor 3 includes a pressure sensor encapsulation layer 11, a pressure sensor sensitive layer 12, and a pressure sensor encapsulation layer 13; the stimulation electrode 4 includes a stimulation electrode encapsulation layer 9, a stimulation electrode conductive layer 10, and a pressure sensor encapsulation layer 11; the pressure sensor encapsulation layer 11 serves as both the encapsulation layer of the pressure sensor 3 and the substrate layer of the stimulation electrode 4.

[0054] The pressure sensor and stimulation electrode module, from top to bottom, consist of a stimulation electrode encapsulation layer 9, a stimulation electrode conductive layer 10, a pressure sensor encapsulation layer 11, a pressure sensor sensitive layer 12, and a pressure sensor substrate layer 13. The pressure sensor and stimulation electrode module are integrated on the surface of the microsphere 5 by an elastic adhesive 14, so that the stimulation electrode and the pressure sensor array expand synchronously with the microsphere 5.

[0055] The pressure-sensitive structure in the pressure sensor sensitive layer 12 includes a pressure sensor signal terminal 15 and a pressure sensor ground terminal 16; the pressure sensor ground terminal 16 is grounded, and the pressure sensor signal terminal 15 is connected to an external circuit; when the pressure sensor 3 is subjected to force, the inter-electrode capacitance changes, and the corresponding electrical signal is collected and analyzed to finally obtain the corresponding pressure value.

[0056] The materials of the stimulation electrode encapsulation layer 9, the pressure sensor encapsulation layer 11, and the pressure sensor substrate layer 13 are polymer thin film materials.

[0057] The polymer film material is polyimide (PI), polyethylene terephthalate (PET), or parylene, with a thickness of 3-7 μm.

[0058] The material of the conductive layer 10 of the stimulation electrode is gold, platinum, or a platinum-iridium alloy; the material of the sensitive layer 12 of the pressure sensor is silver or platinum.

[0059] There are 9 pressure sensors and stimulation electrode modules, arranged in groups of 3, with each group arranged in a straight line along the axis of the balloon catheter 1; the 3 groups are evenly distributed axially at 120° intervals on the upper half of the surface of the microballoon 5 away from the device tail pad 7, forming an array of stimulation electrodes and pressure sensors.

[0060] A fabrication process for integrating a microballoon with a stretchable stimulation electrode and a pressure sensor array includes the following steps:

[0061] Step 1: Cover one side of the silicon-aluminum alloy aluminum sheet with photoresist material, and pattern the photoresist material using photolithography to obtain the pressure sensor substrate layer 13;

[0062] Step 2: Metal is deposited on the surface of the pressure sensor substrate 13 using a sputtering process, and the metal is patterned using a dry etching process to obtain the pressure sensor sensitive layer 12.

[0063] Step 3: Cover the pressure sensor sensitive layer 12 with photoresist material, and use photolithography to pattern the photoresist material to obtain the pressure sensor encapsulation layer 11, exposing the structure of the device tail pad 7.

[0064] Step 4: Metal is deposited on the surface of the pressure sensor encapsulation layer 11 using a sputtering process, and the metal is patterned using a dry etching process to obtain the stimulation electrode conductive layer 10.

[0065] Step 5: Cover the conductive layer 10 of the stimulation electrode with photoresist material, and use photolithography to pattern the photoresist to obtain the stimulation electrode encapsulation layer 9, exposing the structure of the device tail pad 7.

[0066] Step 6: Use a wet etching process to etch the aluminum sheet, releasing the prepared stimulation electrode and pressure sensor module from the silicon wafer;

[0067] Step 7: Use water-soluble tape to remove the stimulation electrode and pressure sensor module from the silicon wafer surface;

[0068] Step 8: Use elastic adhesive 14 to adhere the stimulation electrode and pressure sensor module to the surface of the microsphere 5, remove the water-soluble tape, and expose the device tail pad 7.

[0069] In step 7, after the stimulation electrode and pressure sensor module are transferred from the silicon wafer surface, water-soluble tape is used to transfer the stimulation electrode and pressure sensor module to the surface of the flexible substrate first, and then step 8 is performed.

[0070] After step 8 is completed, a layer of sealing material is sprayed or dripped onto the surface of the microballoon 5 to improve the reliability of the integration of the stimulation electrode with the pressure sensor array and the microballoon 5.

[0071] The pressure sensor is an interdigitated microstructure capacitive pressure sensor that monitors changes in pressure at the stimulation electrode interface by varying the capacitance between the two electrodes.

[0072] The fabrication process of the stimulation electrode and pressure sensor array utilizes photolithography to pattern photoresist as the encapsulation material for the pressure sensor and stimulation electrode. The sensitive layer of the pressure sensor and the conductive layer of the stimulation electrode are vertically stacked to achieve in-situ monitoring of the interface pressure of the stimulation electrode.

[0073] The pressure sensor sensitive layer and the stimulation electrode conductive layer are made of metal thin films sandwiched between two polymer thin films. The pressure sensor sensitive layer can be made of silver (Ag), platinum (Pt), etc., and the stimulation electrode conductive layer can be made of gold (Au), platinum (Pt), platinum-iridium alloy (Pt / Ir), etc. Specific implementation examples:

[0075] This invention proposes a process method for integrating a microballoon with a stretchable stimulation electrode and a pressure sensor array, such as... Figure 1As shown, the stimulation electrode and pressure sensor array are fabricated using MEMS technology and integrated onto the surface of the microballoon 5. The balloon catheter mainly includes the microballoon 5, metal ends 2 at both ends of the microballoon 5, and support ends 6. After device integration, the device tail pad 7 is integrated onto the surface of the metal end 2, and the stimulation electrode 4 and pressure sensor 3 are integrated onto the surface of the microballoon 5. Nine sets of stimulation electrodes 4 and pressure sensors 3 are evenly distributed axially at 120° intervals on the upper half of the microballoon 5 surface away from the device tail pad 7, forming a stimulation electrode and pressure sensor array. The pressure sensor 3 and stimulation electrode 4 are connected to the device tail pad 7 through a large extension wire 8. The device tail pad 7 is then connected to an external device, ultimately realizing pressure sensing and electrical stimulation functions.

[0076] This invention proposes a process method for integrating a microballoon with a stretchable stimulation electrode and a pressure sensor array, such as... Figure 2 The diagram shows the location of the device array on the surface of the microsphere and a cross-sectional view of any device site. From top to bottom, the diagram shows the stimulating electrode encapsulation layer 9, the stimulating electrode conductive layer 10, the pressure sensor encapsulation layer 11, the pressure sensor sensitive layer 12, the pressure sensor encapsulation layer 13, the elastic adhesive 14, and the microsphere 5. The pressure sensor encapsulation layer 11 serves as both the encapsulation layer for the pressure sensor 3 and the substrate layer for the stimulating electrode 4. The stimulating electrode and the pressure sensor array are reliably integrated using the elastic adhesive 14, enabling synchronous expansion of the stimulating electrode and the pressure sensor array along with the microsphere 5.

[0077] This invention proposes a process method for integrating a microballoon with a stretchable stimulation electrode and a pressure sensor array, such as... Figure 3 The diagram shows a layered schematic of the stimulation electrode and pressure sensor array. From top to bottom, the layers are: stimulation electrode encapsulation layer 9, stimulation electrode conductive layer 10, pressure sensor encapsulation layer 11, pressure sensor sensitive layer 12, and pressure sensor encapsulation layer 13. The pressure sensor 3 and stimulation electrode 4 are stacked vertically. The pressure-sensitive structure in the pressure sensor sensitive layer 12 includes a pressure sensor signal terminal 15 and a pressure sensor ground terminal 16. The ground terminals 16 of all nine pressure sensors are uniformly grounded. The pressure sensor signal terminals 15 are connected to an external circuit. When the pressure sensor is subjected to force, the inter-electrode capacitance changes, and the corresponding electrical signal is collected and analyzed to obtain the corresponding pressure value.

[0078] This invention proposes a process method for integrating a microballoon with a stretchable stimulation electrode and a pressure sensor array, such as... Figure 4 The diagram shows the fabrication and integration process of the stimulation electrode and pressure sensor array. The process mainly includes the following steps:

[0079] Step 1: Using photolithography, a suitable photoresist material is patterned to obtain the pressure sensor encapsulation layer 13. The substrate material is a polymer thin film, such as polyimide (PI), polyethylene terephthalate (PET), or parylene, with a thickness of 3-7 μm.

[0080] Step 2: Deposit the pressure layer metal (silver, 300nm) on the substrate surface using a sputtering process, and then pattern the pressure sensing layer metal using a dry etching process to obtain the pressure sensor sensitive layer 12. The pressure sensing structure includes a pressure sensor signal terminal 15 and a pressure sensor ground terminal 16, with an inter-electrode spacing of 5-10μm.

[0081] Step 3: Using photolithography, the photoresist is patterned to obtain the pressure sensor encapsulation layer 11, exposing the structure of the device's tail pad 7. After encapsulation, the distance between the encapsulation layer and the edge of the metal conductive layer is 10 μm.

[0082] Step 4: The metal of the stimulation electrode layer is deposited on the surface of the pressure sensor packaging layer by sputtering process. Then, the metal of the stimulation electrode layer is patterned by dry etching process to obtain the conductive layer 10 of stimulation electrode (chromium / gold, 30nm / 300nm), wherein the diameter of stimulation electrode 3 is 200μm and the width of large extension wire 8 is 10μm.

[0083] Step 5: Using photolithography, the photoresist is patterned to obtain the stimulation electrode encapsulation layer 9, exposing the complete structure of the device tail pad 7;

[0084] Step 6: The prepared device is removed from the silicon wafer using a wet etching process (hydrochloric acid etching of aluminum, with a dilute hydrochloric acid solution (5%)).

[0085] Step 7: Use water-soluble tape to transfer the device off the silicon wafer surface;

[0086] Step 8: The device is adhered to the surface of the microsphere using the elastic adhesive 14. The water-soluble tape is then removed in 45°C warm water, exposing the stimulation electrode 4 and the stimulation electrode and pressure sensor array, thus completing the integration.

[0087] In another specific embodiment, the transfer integration process of the stimulation electrode with the pressure sensor array and the microsphere 5 is improved, such as... Figure 5As shown, after completing the wet etching process for the stimulation electrode and pressure sensor array, the device is first transferred to the surface of a flexible substrate using water-soluble tape. Then, the device is integrated onto the surface of the microsphere 5 using the flexible substrate. Because the flexible substrate has better ductility than the water-soluble tape, it ensures more reliable contact between the stimulation electrode / pressure sensor array and the microsphere 5, thus improving the reliability of the integration of the stimulation electrode and pressure sensor array.

[0088] In another specific embodiment, improvements are made to the reliability of the transfer integration of the stimulation electrode with the pressure sensor array and the microsphere 5, such as... Figure 6 As shown, after the stimulating electrode is integrated with the pressure sensor array and microsphere 5 and the water-soluble adhesive tape is removed, the reliability of the transfer integration of the stimulating electrode with the pressure sensor array and microsphere 5 is improved by spraying / drip coating a layer of sealing material onto the surface of the microsphere device. It should be noted that the stimulating electrode 4 needs to be shielded by a mask when spraying / drip coating the sealing material. The sealing material can be an elastic silicone material such as Ecoflex.

Claims

1. A microballoon integrating a stretchable stimulation electrode and a pressure sensor array, characterized in that, This includes a balloon catheter, pressure sensor, stimulation electrode, device tail pad, and extension wire; The balloon catheter includes a metal end, a microballoon, and a support tube; each end of the microballoon is connected to a metal end, and one of the metal ends is connected to the support tube. The device's tail pad is integrated on a support tube and connected to multiple pressure sensors and multiple stimulation electrodes via extension wires; the device's tail pad is also connected to external devices. The multiple pressure sensors and multiple stimulation electrodes are integrated on the surface of the microsphere to form an array of stimulation electrodes and pressure sensors; wherein, the pressure sensor is an interdigitated microstructure capacitive pressure sensor. The pressure sensors and stimulation electrodes are of the same number and are stacked vertically to form a pressure sensor and stimulation electrode module. The pressure sensor includes a pressure sensor encapsulation layer, a pressure sensor sensitive layer, and a pressure sensor substrate layer; the stimulation electrode includes a stimulation electrode encapsulation layer, a stimulation electrode conductive layer, and a pressure sensor encapsulation layer; the pressure sensor encapsulation layer serves as both the encapsulation layer of the pressure sensor and the substrate layer of the stimulation electrode. The pressure sensor and stimulation electrode module, from top to bottom, consist of a stimulation electrode encapsulation layer, a stimulation electrode conductive layer, a pressure sensor encapsulation layer, a pressure sensor sensitive layer, and a pressure sensor substrate layer. The pressure sensor and stimulation electrode module are integrated on the surface of the microsphere using an elastic adhesive, enabling the stimulation electrode and pressure sensor array to expand synchronously with the microsphere. The pressure sensor sensitive layer and the stimulation electrode conductive layer are vertically stacked, so that the pressure sensor sites and stimulation electrode sites are vertically stacked and integrated in situ on the surface of the microsphere, achieving in-situ monitoring of the pressure at the stimulation electrode interface. Nine pressure sensors and stimulation electrode modules are provided, with three in each group. The three pressure sensors and stimulation electrode modules in each group are arranged in a straight line along the axis of the balloon catheter. The three groups of pressure sensors and stimulation electrode modules are evenly distributed circumferentially at 120° intervals on the upper half of the microballoon surface away from the device tail pad, forming a stimulation electrode and pressure sensor array. The pressure-sensitive structure in the pressure sensor sensitive layer includes a pressure sensor signal terminal and a pressure sensor ground terminal; the pressure sensor ground terminal is grounded, and the pressure sensor signal terminal is connected to an external circuit; when the pressure sensor is subjected to force, the inter-electrode capacitance changes, the corresponding electrical signal is collected and analyzed, and finally the corresponding pressure value is obtained; The materials of the stimulation electrode encapsulation layer, the pressure sensor encapsulation layer, and the pressure sensor substrate layer are polymer thin film materials. The polymer film material is polyimide (PI), polyethylene terephthalate (PET), or parylene, with a thickness of 3-7 mm. μ m; The material of the conductive layer of the stimulation electrode is gold, platinum, or a platinum-iridium alloy; the material of the sensitive layer of the pressure sensor is silver or platinum.

2. A method for fabricating a microsphere-integrated stretchable stimulation electrode and pressure sensor array as described in claim 1, characterized in that, Includes the following steps: Step 1: Cover one side of the aluminum sheet of the silicon-aluminum alloy wafer with photoresist material, and use photolithography to pattern the photoresist material to obtain the pressure sensor substrate layer; Step 2: Metal is deposited on the surface of the pressure sensor substrate using a sputtering process, and the metal is patterned using a dry etching process to obtain the pressure sensor sensitive layer; Step 3: Cover the pressure sensor sensitive layer with photoresist material, and use photolithography to pattern the photoresist material to obtain the pressure sensor encapsulation layer, exposing the device tail pads; Step 4: Metal is deposited on the surface of the pressure sensor packaging layer using a sputtering process, and the metal is patterned using a dry etching process to obtain the conductive layer of the stimulation electrode. Step 5: Cover the conductive layer of the stimulation electrode with photoresist material, and use photolithography to pattern the photoresist material to obtain the stimulation electrode encapsulation layer, exposing the device tail pad. The pressure sensor sensitive layer and the conductive layer of the stimulation electrode are stacked vertically to realize in-situ monitoring of the pressure at the stimulation electrode interface, forming a pressure sensor and stimulation electrode module. Step 6: Use a wet etching process to etch one side of the aluminum sheet of the silicon-aluminum alloy sheet to release the prepared pressure sensor and stimulation electrode module from the silicon-aluminum alloy sheet; Step 7: Use water-soluble tape to transfer the pressure sensor and stimulation electrode module from the silicon-aluminum alloy sheet to the surface of the flexible substrate, and then use the flexible substrate to integrate the pressure sensor and stimulation electrode module onto the surface of the microsphere. Step 8: Use elastic adhesive to adhere the pressure sensor and stimulation electrode module to the surface of the microsphere, remove the water-soluble tape, and expose the device tail pads so that the pressure sensor sites and stimulation electrode sites are vertically stacked and integrated in situ on the surface of the microsphere. Step 9: Spray or drop-coat a layer of sealing material onto the surface of the microsphere to improve the reliability of the integration of the stimulation electrode with the pressure sensor array and the microsphere.

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