A device for sensing a fingertip signal from a surgical instrument metal grip area

Abstract

This invention provides a device for sensing fingertip signals from the metal grip area of ​​surgical instruments, comprising a dual-mode sensing stack. The dual-mode sensing stack, from the finger towards the metal grip area substrate, sequentially includes a finger contact surface, a pressure sensing layer, a capacitive sensing array, and a shielding layer; the pressure sensing layer and the capacitive sensing array are electrically insulated from each other. The pressure sensing layer includes an upper gridded silver electrode, a piezoresistive ink layer, and a lower gridded silver electrode. Both the upper and lower gridded silver electrodes are formed by interwoven silver wires. The linewidth w of the silver wires (10) is 50–100 μm, and the mesh spacing d is 200–600 μm. The aperture ratio η of the upper and lower gridded silver electrodes satisfies the threshold range: 50% ≤ η ≤ 80%, and the aperture ratio η = (1 − w / d)². The capacitive sensing array includes multiple independent capacitive electrodes, each with a diameter D ≥ 10d. The shielding layer is electrically connected to the analog ground of the acquisition circuit and is DC isolated from the metal grip area substrate. This invention provides a fingertip signal sensing device that, through systematic design of structural parameters, can control the loss rate of pressure signals to 5% to 8% while ensuring high touch sensitivity.

Description

Technical Field

[0001] This invention relates to a medical device sensor, and more particularly to a device for sensing fingertip signals from the metal grip area of ​​a surgical instrument. Background Technology

[0002] The metal grip area of ​​surgical instruments (such as bipolar electrocoagulation forceps) is the main contact area for surgeons to perform delicate operations. Integrating fingertip tactile sensing capabilities in this area can provide surgeons with multi-dimensional information such as the operation position, contact area, and pressure, which helps to improve the safety and accuracy of the operation.

[0003] Currently, sensor technology has been successfully applied in multiple fields. For example, in the field of touchscreens, there are sensor solutions based on metal meshes that can simultaneously sense touch position and pressure. The mesh material can be aluminum, molybdenum, copper, nickel, or titanium, with an equivalent mesh diameter of typically 20–60 μm and a mesh linewidth of 1–5 μm. However, these sensors are mainly designed for transparent insulating substrates and are difficult to directly transfer to the metal grip area of ​​surgical instruments, and they cannot meet the high-precision sensing requirements of extremely small contact areas in this scenario. Summary of the Invention

[0004] To address the deficiency in existing technologies of fingertip signal sensing devices that can control pressure signal loss within an acceptable range while ensuring high touch sensitivity through systematic design of structural parameters, this invention provides a dual-mode sensing device that can achieve high touch sensitivity (stable detection of dynamic capacitance changes as low as 0.5pF, corresponding to a very small touch area of ​​approximately 4mm²) while controlling the pressure signal loss rate to be low at 5% to 8% in the metal grip area of ​​surgical instruments.

[0005] A device for sensing fingertip signals from the metal grip area of ​​a surgical instrument includes a dual-mode sensing stack. From the finger towards the base of the metal grip area, it sequentially comprises: a finger contact surface, a pressure sensing layer, a capacitive sensing array, and a shielding layer. The pressure sensing layer and the capacitive sensing array are electrically insulated. The pressure sensing layer includes an upper meshed silver electrode and a lower meshed silver electrode, and a piezoresistive ink layer sandwiched between them. Both the upper and lower meshed silver electrodes are mesh-like structures formed by interwoven silver wires. The linewidth of the silver wires is 50–100 μm, and the mesh spacing d is 200–600 μm. The upper mesh... The aperture ratio η of the silver electrode and the lower grid silver electrode satisfies: 50%≤η≤80%, and when the mesh shape is square, the aperture ratio η=(1−w / d)²; the capacitive sensing array includes multiple independent capacitive electrodes, and the diameter D of a single capacitive electrode is ≥10d (i.e., the electrode spans at least 10 grid cycles in the plane, which significantly reduces the statistical fluctuation of the coverage ratio and eliminates the capacitance dispersion caused by misalignment); the shielding layer is provided with a grounding terminal, which is used to electrically connect to the analog ground of the external acquisition circuit; the shielding layer is DC isolated from the substrate of the metal gripping area.

[0006] More preferably, the silver wire width of the upper and lower meshed silver electrodes is 70-80 μm, the mesh spacing d is 300-500 μm, and the aperture ratio η of the upper and lower meshed silver electrodes satisfies: 60%≤η≤70%.

[0007] More preferably, the mesh shape of the upper and lower meshed silver electrodes is square, rhomboid, or hexagonal, and the mesh is arranged periodically and uniformly.

[0008] More preferably, an insulating layer is provided between the pressure sensing layer and the capacitive sensing array, the thickness of the insulating layer h ≥ 80 μm, and the relative permittivity is 3.0 to 3.5.

[0009] More preferably, the number of independent capacitor electrodes in the capacitive sensing array is 4 to 8, arranged on a 20mm×15mm gripping area curved surface, the diameter of each capacitor electrode is 3 to 5mm, and the diameter D and the mesh spacing d satisfy D≥10d, and the electrode spacing ≥1.5mm.

[0010] More preferably, the shielding layer is connected to the analog ground of the acquisition circuit via a low-impedance trace, and the shielding layer is DC isolated from the metal gripping area substrate via an insulating layer or an air gap.

[0011] More preferably, the shielding layer is a copper foil, and the projection of the shielding layer in the direction perpendicular to the dual-mode sensing stack covers the entire projection area of ​​the capacitive sensing array.

[0012] A further preferred embodiment is that the finger contact surface is a medical-grade silicone layer.

[0013] More preferably, the thickness of the dual-mode sensing stack and the gradual transition structure of its edges are adapted to be embedded in the compensation thinning area provided on the metal gripping area substrate, and the thinning amount of the compensation thinning area is 0.3 to 0.4 mm; stress relief grooves are provided on the surface of the dual-mode sensing stack near the edge.

[0014] More preferably, the total thickness of the dual-mode sensing stack is 500-600 μm, and the layers are bonded together with medical-grade acrylic pressure-sensitive adhesive.

[0015] Compared with existing technologies, this invention has the following advantages: By designing the continuous silver electrodes in the pressure sensing layer as a mesh structure, and simultaneously limiting the silver wire width (50-100μm), mesh spacing (200-600μm), aperture ratio (50%-80%), and capacitor electrode diameter (D≥10d), the silver mesh maintains a continuous conductive path between the mesh openings, effectively collecting the current signal from the piezoresistive ink layer. Within the full aperture ratio range of 50%-80%, the pressure signal loss does not exceed 15%, which can be eliminated through back-end gain compensation; within the preferred aperture ratio range of 60%-70%, the pressure signal loss can be further reduced to 5%-8%. Simultaneously, this structure ensures stable detection of dynamic capacitance changes as low as 0.5pF (corresponding to a very small touch area of ​​approximately 4mm²), achieving a balance between high touch sensitivity and low pressure signal loss, meeting medical-grade accuracy requirements. Attached Figure Description

[0016] Figure 1 This is an exploded view of the basic structure of the dual-mode sensing stack provided in an embodiment of the present invention.

[0017] Figure 2 This is an exploded view of a dual-mode sensing stack including an insulating isolation layer provided in an embodiment of the present invention.

[0018] Figure 3 This is an exploded view of a dual-mode sensing stack containing a PET substrate provided in an embodiment of the present invention.

[0019] Figure 4 This is a schematic diagram of the local cross-sectional parameters of the gridded silver electrode provided in an embodiment of the present invention.

[0020] Figure 5 This is a schematic diagram showing the direction of electric field lines provided in an embodiment of the present invention.

[0021] Figure 6 This is a cross-sectional schematic diagram of the dual-mode sensing stack assembly on the metal gripping area substrate provided in an embodiment of the present invention.

[0022] Figure 7 This is a schematic diagram of the overall structure of the bipolar electrocoagulation tweezers provided in an embodiment of the present invention.

[0023] Explanation of the labels in the diagram:

[0024] 1. Dual-mode sensing stack; 2. Finger contact surface; 3. Metal gripping area substrate; 4. Pressure sensing layer; 5. Capacitive sensing array; 6. Shielding layer; 7. Upper meshed silver electrode; 8. Lower meshed silver electrode; 9. Piezoresistive ink layer; 10. Silver wire; 11. Capacitive electrode; 12. Insulating layer; 13. Compensation thinning area; 14. Gradient transition structure; 15. Tweezers; 16. Grip portion; 17. First reservoir; 18. Second reservoir; 19. Base; 20. Extension sheet; 21. Signal line. Detailed Implementation

[0025] The following embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention. Any modifications or substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and essence of the invention are within the scope of the present invention.

[0026] In existing technologies, if the continuous silver conductive electrodes of a standard piezoresistive film are used to cover the entire gripping area, a low-impedance conductive surface is formed, resulting in a severe electrostatic shielding effect. This blocks the electric field of the capacitive sensing electrodes below from reaching the finger, causing capacitive touch detection to fail. To solve this physical compatibility problem, this embodiment innovates the electrode structure of the pressure sensing layer 4 and the capacitive sensing array structure.

[0027] Example 1: Mesh Silver Electrode Structure and Piezoresistive Signal Collection Mechanism

[0028] like Figures 1 to 5 As shown, this embodiment of the invention provides a device for sensing fingertip signals from the metal grip area of ​​a surgical instrument. Its core structure includes a dual-mode sensing stack 1. The dual-mode sensing stack 1, from the finger towards the metal grip area substrate 3, sequentially includes: a finger contact surface 2, a pressure sensing layer 4, a capacitive sensing array 5, and a shielding layer 6. The pressure sensing layer 4 and the capacitive sensing array 5 are electrically insulated from each other, and the capacitive sensing array 5 and the shielding layer 6 are adjacent to each other.

[0029] Specifically, such as Figure 1 and Figure 4As shown, the pressure sensing layer 4 includes an upper gridded silver electrode 7 and a lower gridded silver electrode 8, and a piezoresistive ink layer 9 sandwiched between them. Both the upper and lower gridded silver electrodes 7 and 8 are formed by a grid-like structure of interwoven silver wires 10, replacing the traditional continuous planar structure. The linewidth w of the silver wires 10 is 50–100 μm, preferably 70–80 μm, and more preferably 75 μm. The mesh spacing d is 200–600 μm, preferably 300–500 μm, and more preferably 400 μm. The aperture ratio η of the upper and lower gridded silver electrodes satisfies: 50% ≤ η ≤ 80%, preferably 60% ≤ η ≤ 70%, and more preferably 66%. For a square grid, the aperture ratio η = (1 - w / d)²; for a rhomboid or hexagonal grid, the aperture ratio is calculated according to the corresponding geometric relationship, but all satisfy the above ranges. The mesh shape can be a periodic pattern such as square, rhombus or hexagon, and the mesh is arranged periodically and uniformly. For rhombus or hexagonal meshes, the aperture ratio is calculated according to the corresponding geometric relationship. The silver line width, mesh spacing and silver coverage range defined by this invention still meet the dual performance requirements of electric field penetration and piezoresistive collection after conversion.

[0030] The working mechanism of the gridded silver electrode that eliminates electrostatic shielding while retaining piezoresistive collection is as follows:

[0031] Under the approximation of a uniformly wide, orthogonal grid with silver wires, the geometric relationship between the grid aperture ratio (i.e., the proportion of the area that can be penetrated by the electric field without silver wire coverage) η and the silver wire width w and the mesh spacing d is as follows:

[0032]

[0033] The mesh spacing d is defined as the center-to-center distance between adjacent silver lines, i.e., the mesh period. For a square mesh, the aperture ratio η = (1 - w / d)². When the mesh shape is rhomboid or hexagonal, the aperture ratio needs to be converted according to the corresponding geometric relationship (for example, the aperture ratio η of a regular hexagonal mesh is 1 - (2 / 3)·(w / d) + (1 / 3)·(w / d)², where d is the distance between opposite sides). However, the selected parameters must also meet the dual constraints of a capacitance channel signal-to-noise ratio of not less than 10dB and engineering-acceptable pressure signal loss. The mesh parameter range of this invention (line width 50-100μm, d of 200-600μm, silver coverage 20%-50%) can achieve the above effects under common mesh geometries.

[0034] Substituting the preferred values ​​w=75μm and d=400μm, we can obtain the aperture ratio. ≈0.66. This aperture ratio allows the capacitive sensing electric field below to penetrate through the mesh to the finger contact surface 2 (the electric field penetration area is approximately 66%), enabling the capacitor channel signal-to-noise ratio (SNR) to meet the requirement of ≥10dB, thereby stably detecting dynamic capacitance changes as low as 0.5pF.

[0035] Meanwhile, the silver mesh still forms a continuous conductive path between the mesh openings. The equivalent resistance of the meshed piezoresistive channel can be expressed as:

[0036]

[0037] in, The equivalent resistivity of the piezoresistive ink / silver mesh composite channel. The effective current path length along the thickness direction of the stack (i.e., the thickness of the piezoresistive ink layer). The nominal cross-sectional area (electrode area parallel to the stacked plane). The effective coverage factor of the silver grid over the nominal section. Piezoresistive ink varies with pressure The normalized piezoresistive characteristic function decreases monotonically. This formula shows that the mesh structure only increases the reference resistance by a constant coefficient of 1 / (1-η), without changing... The pressure-resistance relationship is monotonic. Therefore, this structure can effectively collect the current signal in the piezoresistive ink layer 9 while ensuring electric field penetration. Taking the preferred parameters (w=75μm, d=400μm, η≈0.66) as an example, actual measurements show that the pressure signal loss (defined as: the attenuation ratio of the output amplitude of this device relative to the output amplitude of the reference device using continuous silver electrodes under the same standard pressure) is approximately 5% to 8%, which is within the acceptable range for medical use.

[0038] It should be noted that the mesh parameter range of this invention (silver line width 50-100 μm, mesh spacing 200-600 μm) is geometrically equivalent to an aperture ratio η (the proportion of area without silver line coverage that the electric field can penetrate) between 50% and 80% (corresponding to a silver coverage rate 1-η of 20%-50%). The conversion relationship is based on a square mesh model: aperture ratio η = (1-w / d)², silver coverage rate = 1-η. When the aperture ratio η = 0.5, the silver coverage rate is 50%; when η = 0.8, the silver coverage rate is 20%.

[0039] At the boundary, the technical effect of the present invention can still be guaranteed:

[0040] Capacitive channel signal-to-noise ratio (SNR) boundary verification: The amplitude of the capacitive signal is approximately proportional to the area through which the electric field penetrates. In the preferred embodiment, w=75μm, d=400μm, η≈0.66, and the measured SNR≥21.6dB (corresponding to a voltage SNR of 12:1). When η=0.5 (50% coverage), the signal amplitude is approximately 0.5 / 0.66≈0.76 times that of the preferred point, and the calculated SNR is approximately 16.4dB, still far exceeding the minimum requirement of 10dB. When η=0.8 (20% coverage), the signal amplitude is approximately 0.8 / 0.66≈1.21 times that of the preferred point, and the calculated SNR≈26.1dB, which also meets the requirement. Therefore, the capacitive touch detection sensitivity meets the standard across the entire aperture ratio range.

[0041] Pressure signal loss boundary verification: Pressure signal loss monotonically increases with increasing aperture ratio η (i.e., the larger η is, the smaller the silver coverage 1-η is, the greater the signal loss). This is because the current of the piezoresistive ink mainly relies on the silver mesh for collection. The higher the silver coverage (i.e., the smaller η is), the more complete the current collection channel, and the smaller the signal loss. Based on the preferred embodiment of this application (w=75μm, d=400μm, η≈0.66), the measured pressure signal loss is 5%~8%. Based on this benchmark and the positive correlation between pressure loss and η, it can be reasonably deduced that: when η=0.5 (silver coverage 50%), because η is smaller (silver coverage higher), the pressure signal loss should be lower than 5%~8%, and the measured value can be controlled at around 3%~5%; when η=0.8 (silver coverage 20%), because η is larger (silver coverage lower), the pressure signal loss should be higher than 5%~8%, and the measured value is about 10%~15%. Therefore, within the entire aperture ratio range of 50% to 80%, the pressure signal loss is within the engineering-acceptable range of ≤15%, and can be eliminated through back-end gain compensation.

[0042] It should be noted that although the pressure signal loss increases monotonically with the increase of the aperture ratio η, the capacitive touch sensitivity also increases monotonically with the increase of the aperture ratio η. There is a contradiction between the two: a low aperture ratio (high silver coverage) is beneficial for pressure signal fidelity but detrimental to capacitive penetration, while a high aperture ratio (low silver coverage) is beneficial for capacitive sensitivity but increases pressure loss. Therefore, this application limits the aperture ratio to between 50% and 80%, ensuring that the capacitive signal-to-noise ratio is not less than 10dB while keeping the pressure signal loss within an acceptable range, achieving a systematic balance in dual-mode performance. Among these, an aperture ratio of 60% to 70% is a more optimal balance range that balances low pressure signal loss (5% to 8%) and high touch sensitivity (corresponding to a silver coverage of 30% to 40%).

[0043] In summary, the aperture ratio η of the upper and lower meshed silver electrodes satisfies: 50% ≤ η ≤ 80%, and when the mesh shape is square, the aperture ratio η = (1 − w / d)². Both meet the signal-to-noise ratio requirement of not less than 10 dB in terms of capacitive detection sensitivity, and the pressure signal loss does not exceed 15% across the entire range, which can be eliminated through back-end gain compensation. For medical-grade high precision (pressure loss 5%–8%), a further optimized aperture ratio η satisfying 60% ≤ η ≤ 70% is preferable.

[0044] Example 2: Anti-interference design of capacitive sensing array and shielding layer

[0045] Based on the above embodiment 1, in order to further eliminate the capacitance dispersion caused by the alignment-free process and improve the anti-interference capability in complex medical environments, this embodiment has made specific designs for the capacitive sensing array 5 and the shielding layer 6.

[0046] like Figure 1 and Figure 2 As shown, the capacitive sensing array 5 (which can be fabricated using FPC flexible printed circuit board technology) includes multiple independent capacitor electrodes 11. To achieve a smooth spatial integration design, this invention limits the diameter D of a single capacitor electrode 11 to ≥ 10d.

[0047] The underlying logic is that when D ≥ 10d, a single capacitor electrode 11 spans at least 10 grid cycles in the plane. Regardless of the random placement of the capacitor electrode 11 relative to the gridded silver electrode above it, the ratio of the discrete silver lines it covers to the mesh openings tends to be consistent (approximately equal to the aperture ratio η). This discrete distribution of the grid is smoothed by spatial integration at the electrode scale, thereby completely eliminating the component-by-component basic capacitance dispersion ΔC0 caused by the lack of precise interlayer alignment.

[0048] Quantitatively speaking, when the electrode spans a sufficient number of grid cycles (N≥10), the statistical fluctuation standard deviation of the coverage ratio decreases significantly with the increase of the number of cycles spanned, thereby ensuring the consistency of the basic capacitance among the electrodes in engineering.

[0049] In the preferred embodiment, the number of independent capacitive electrodes 11 is 4 to 8, arranged on the curved surface of the 20mm × 15mm metal gripping area base 3. The diameter of each capacitive electrode 11 is 3 to 5mm, preferably Φ4mm, and the electrode spacing is ≥1.5mm. It should be noted that when the diameter D of the capacitive electrode is taken from the range of 3 to 5mm, in order to ensure that the relationship D≥10d holds, the mesh spacing d should be selected from the range of 200 to 500μm (i.e., d≤D / 10). For example, when D=3mm, d≤300μm; when D=4mm, d≤400μm; when D=5mm, d≤500μm. This arrangement corresponds to the typical contact areas of the surgeon's thumb pad, index finger, and middle finger, and can simultaneously obtain the contact position and touch area characteristics.

[0050] Furthermore, to suppress electrocoagulation high-frequency interference and prevent the pF-level fingertip capacitance signal from being overwhelmed by parasitic channels, the projection of the shielding layer 6 (such as a grounded copper foil) in the direction perpendicular to the dual-mode sensing stack 1 covers the entire projection area of ​​the capacitive sensing array 5. The shielding layer 6 is provided with a grounding terminal (not shown in the figure), which is used to electrically connect to the analog ground of the external acquisition circuit (such as the ground terminal of the MCU microcontroller unit); DC isolation between the shielding layer 6 and the metal gripping area substrate 3 is achieved through an insulating layer or an air gap.

[0051] The anti-interference mechanism is as follows: the structure connects to the simulated ground through the shielding layer 6, which can effectively isolate the coupling interference between the metal holding area substrate 3 and the capacitor electrode 11; at the same time, the shielding layer 6 and the metal holding area substrate 3 maintain DC isolation (through the insulating layer or air gap), avoiding the formation of a DC grounding loop between the shielding layer and the metal substrate, thereby preventing the introduction of power frequency and electrocoagulation high-frequency noise.

[0052] Example 3: Insulation Layer Parameters and Parasitic Capacitance Model

[0053] like Figure 2 and Figure 3 As shown, an insulating layer 12 (such as a PET polyethylene terephthalate film) is provided between the pressure sensing layer 4 and the capacitive sensing array 5. The thickness h of the insulating layer 12 is ≥80μm (typically 100μm), and the relative permittivity ε_r is 3.0~3.5.

[0054] Parameter setting basis and parasitic capacitance model: The insulating isolation layer 12 introduces parasitic capacitance between the gridded silver electrode and the capacitive electrode 11 in the pressure sensing layer 4. Estimated using a parallel plate model:

[0055]

[0056] in Let A be the vacuum permittivity, and H be the area of ​​the electrode facing outwards. Assuming a single capacitor electrode has a facing area of ​​A≈12.6 mm² and h≈100 μm, ≈3.2 Calculation, the introduced parasitic capacitance Approximately 3.6 pF. Since this parasitic capacitance is a fixed background capacitance, it can be eliminated at the acquisition front end through baseline subtraction or differential measurement. Limiting h ≥ 80 μm ensures... By controlling the capacitance to the pF level, the dynamic range of the front end will not be saturated, thus ensuring that the weak fingertip dynamic capacitance signal in the range of 0.5 to 2 pF is not overwhelmed.

[0057] Example 4: Structural Assembly, Tactile Compensation, and Medical-Grade Reliability

[0058] To meet the delicate operational requirements of surgical procedures and the stringent sterilization standards of medical devices, such as Figure 5 As shown, this embodiment has been optimized in terms of structure and assembly.

[0059] The finger contact surface 2 is a medical-grade silicone layer. The total thickness of the dual-mode sensing stack 1 is controlled between 500 and 600 μm (typically about 560 μm), and the layers (including...) are separated by... Figure 3 The PET substrates shown are bonded together using medical-grade acrylic pressure-sensitive adhesive.

[0060] To ensure that the grip feel after integration and stacking is consistent with the original device, the metal grip area base 3 is provided with a compensation thinning area 13, with a thinning amount of 0.3 to 0.4 mm. The edge of the dual-mode sensing stack 1 is designed with a gradient transition structure 14, so that the outer contour of the grip area after the stack is embedded is basically consistent with the original design.

[0061] Medical-grade reliability mechanism: A stress relief groove (not shown in the figure) is provided near the edge surface of the dual-mode sensing stack 1. This stress relief groove, in conjunction with the compensation thinning zone 13, can effectively alleviate the interlayer shear stress caused by curved surface bonding and the thermal cycle of 134°C high-temperature and high-pressure steam sterilization, preventing delamination failure at the interfaces of the stack. Simultaneously, the overall insulation wrapping design enables the structure to pass a 4000V_rms AC withstand voltage test (leakage current ≤10μA), meeting medical-grade electrical safety requirements. Furthermore, the edges of the dual-mode sensing stack are provided with edge sealing structures (such as silicone edging or edge heat-pressing sealing) to support liquid-proof sealing and anti-delamination after repeated 134°C steam sterilization.

[0062] Example 5: Piezoresistive Signal Mesh Compensation Logic (Matching Method)

[0063] Although the gridded silver electrode controls the pressure signal loss to 5% to 8%, in order to achieve high-precision measurement, this invention employs gain compensation logic in the back-end signal processing stage (in the external MCU).

[0064] Specifically, a two-point or multi-point calibration method is employed: after product assembly, several known standard pressures (e.g., 0.5N, 1N, 2N, 4N) are applied, and the corresponding output voltages are recorded. The "output voltage-pressure" calibration curve and gain coefficient k are obtained through least-squares fitting, aligning the compensated output P=k·g(V_out) with the output of the continuous silver electrode scheme under the same pressure. This eliminates the amplitude attenuation introduced by gridding through a definite and calibrable gain compensation, avoiding unexplainable black-box loops.

[0065] Example 6: Pressure signal loss rate and detection of minute capacitance changes (as low as 0.5pF)

[0066] Pressure signal loss rate detection method:

[0067] (1) Sample preparation:

[0068] Two sets of piezoresistive pressure sensing layer samples were prepared. The first set was the reference sample: continuous silver electrodes (without mesh) were used as the upper and lower electrodes, and the piezoresistive ink layer and PET substrate were the same as those in this application. The second set was the test sample: the meshed silver electrodes described in this application (silver linewidth w=75μm, mesh spacing d=400μm, porosity 66%) were used, and the remaining materials and processes were exactly the same as the reference sample.

[0069] (2) Testing equipment:

[0070] A universal testing machine (such as the Instron 5943) equipped with a flat compression head; a precision source meter (such as the Keithley 2450) or a digital multimeter; and a data acquisition and control system.

[0071] (3) Test steps:

[0072] ① Place the reference sample on the testing machine platform and apply a constant voltage V=3.3V (DC) between the upper and lower gridded silver electrodes (along the stack thickness direction).

[0073] ② Apply pressure at a rate of 0.1 mm / min, sequentially reaching four standard pressure points: 0.5 N, 1 N, 2 N, and 4 N. Hold each pressure point for 5 seconds and record the current value read by the source meter. .

[0074] ③ Repeat steps ①-②, test the sample, and record the current value at the same pressure point. .

[0075] ④ Calculate the signal loss rate at each pressure point using the following formula:

[0076]

[0077] ⑤ Take the arithmetic mean of the loss rates at the four pressure points as the pressure signal loss rate of the sample.

[0078] (4) Result determination:

[0079] When the loss rate of the test sample is between 5% and 8%, it indicates that the attenuation of the piezoresistive signal by the gridded design is within an acceptable range and can be fully recovered through back-end gain compensation.

[0080] Methods for detecting minute capacitance changes (as low as 0.5pF):

[0081] (1) Test sample:

[0082] The dual-mode sensing stack described in this application uses a single independent capacitor electrode (diameter Φ4mm) in the capacitive sensing array as a detection unit, with the shielding layer grounded and the insulation isolation layer having a thickness ≥80μm.

[0083] (2) Testing equipment:

[0084] High-precision capacitance detection chip (such as AD7147 or TI FDC2214), sampling rate ≥100Hz, resolution ≥0.1pF; precision displacement stage; conductive copper foil simulating finger contact area (area 4mm², 10mm², 25mm²); signal acquisition and data analysis system.

[0085] (3) Test steps:

[0086] ① Connect the capacitor electrode to the detection chip, and connect the shielding layer to the chip's simulated ground. Without a finger or copper foil nearby, continuously acquire 100 frames of background capacitance values ​​and calculate the background capacitance. Mean and standard deviation .

[0087] ② Fix a copper foil with an area of ​​4 mm² to the end of the displacement stage, press it vertically above the capacitor electrode with a constant contact pressure of 0.2 N, maintain contact for 3 seconds, and record the real-time capacitance value C output by the capacitance detection chip.

[0088] ③ Calculate the change in capacitance Repeat the measurement 5 times and take the average value.

[0089] ④ Change the copper foil area to 10mm² and 25mm², repeat steps ②-③, and record ΔC for different areas.

[0090] ⑤ Simultaneously record the signal-to-noise ratio (SNR) for each measurement. (Expressed in dB: SNR(dB) = .

[0091] (4) Result determination:

[0092] When the copper foil area is 4 mm², ΔC should be ≥ 0.5 pF, and SNR ≥ 10 dB (i.e., ΔC ≥ 3.16 × σ0). When the copper foil area is 10 mm², ΔC should be ≥ 1.0 pF; when the area is 25 mm², ΔC should be ≥ 2.0 pF. Meeting the above indicators indicates that the device of this application can stably detect dynamic capacitance changes as low as 0.5 pF, corresponding to a very small touch area of ​​approximately 4 mm².

[0093] During the research and development process, the applicant discovered that after making the following modifications to the dual-mode sensing stack described in this application, which deviate from the scope of the claims of this application, the aforementioned dual-mode performance could not be achieved simultaneously (the following are all comparisons and verifications of out-of-boundary parameters):

[0094] Counter-evidence 1 (Aperture ratio below the lower limit): Keeping the linewidth w of the silver wire constant at 75 μm, the mesh spacing d is reduced to 100 μm (d=100 μm is already below the 200 μm lower limit defined in claim 1 of this application). Calculations show that the aperture ratio η=(1-75 / 100)²=(0.25)²=6.25%, far below the 50% lower limit. Test results show that although the silver coverage is as high as 93.75% and the pressure signal loss is extremely low (approximately 2%), due to the excessively small aperture ratio, the capacitive electric field penetration area is severely insufficient, the signal-to-noise ratio is below 5dB, and it is unable to stably detect dynamic capacitance changes of 0.5pF. It also shows no response to the extremely small touch area of ​​4mm². This indicates that when the aperture ratio is below 50%, although the pressure signal is preserved, the capacitive touch sensitivity fails.

[0095] Counter-evidence Example 2 (Aperture ratio exceeding the upper limit): The linewidth w of the silver wire was adjusted to 50μm (still within the linewidth range of this application), and the mesh spacing d was increased to 700μm (d=700μm makes the aperture ratio exceed the 80% upper limit of claim 1 of this application). Calculations showed that the aperture ratio η=(1-50 / 700)²≈(0.9286)²≈86.2%, which is higher than 80%. Test results revealed that although the capacitive electric field has a large penetration area, enabling the detection of 0.5pF capacitance changes and providing good response to a very small area of ​​4mm², the pressure signal loss is as high as 18%–22%, far exceeding the acceptable range of 5%–8%, and exceeding the engineering usable boundary of "pressure signal loss ≤15%" stated in this application. It cannot be restored to medical-grade accuracy through conventional gain compensation. This indicates that when the aperture ratio is higher than 80%, although the touch is sensitive, the pressure loss is too large, resulting in a dual-mode imbalance.

[0096] Counter-evidence Example 3 (Violation of D≥10d condition): Maintaining the grid parameters within the range of this application (w=75μm, d=400μm, η=66%), reducing the diameter D of a single capacitor electrode 11 to 2mm results in D=2mm<10d=4mm, violating the constraint of D≥10d in claim 1 of this application. The test results show that because D<10d, the number of grid periods covering each capacitor electrode is insufficient (only about 5), weakening the spatial integration smoothing effect. Under alignment-free assembly, the basic capacitance dispersion ΔC0 of each electrode increases significantly (standard deviation reaches 0.8pF), making it impossible to stably detect dynamic capacitance changes of 0.5pF. Simultaneously, the drastic fluctuations in basic capacitance are coupled to the pressure signal acquisition link through the insulating layer, introducing additional noise and increasing the pressure signal loss from 5%–8% within the preferred range of this application to 17%–25%, exceeding the acceptable range. This indicates that D≥10d is a necessary condition for achieving dual-mode performance synergy; violating this condition will simultaneously degrade the capacitance detection sensitivity and pressure signal fidelity.

[0097] Example 7: Alternative Solutions and Extended Applications

[0098] Without departing from the core concept of this invention, those skilled in the art may use the following alternative solutions:

[0099] 1. Fabrication process alternatives: In addition to standard screen printing, when the line width requirement is close to or less than 75μm, laser etching or photolithography can be used to fabricate the gridded silver electrode to avoid the yield risk caused by line breakage or smearing, so as to obtain higher line width accuracy and edge sharpness.

[0100] 2. Sensing mode replacement: The capacitive sensing array 5 can be replaced with a resistive or piezoelectric tactile sensing array; the pressure sensing layer 4 can be replaced with a strain gauge or fiber optic pressure sensor to adapt to different electromagnetic compatibility requirements.

[0101] 3. Alternative Layered Structures: In scenarios with extreme thickness requirements, the use of FPC coplanar cross-finger electrodes can be explored, eliminating the need for a separate pressure sensing layer and further reducing the total thickness of the stacked structure to approximately 360 μm. Alternatively, a local windowing approach (creating a circular cutout of approximately Φ3 mm in the silver layer directly above the capacitor electrode) can be employed. Although its penetration area is only about 30% and requires precise alignment, it can still be considered as an alternative in scenarios with low sensitivity requirements.

[0102] 4. Application of instruments: The fingertip signal sensing device provided by this invention is not limited to bipolar electrocoagulation forceps, but can also be widely transplanted to the metal grip area of ​​other handheld surgical instruments such as ultrasonic scalpels, electrocautery hooks, and needle holders, as well as other interactive interfaces that require the integration of fingertip tactile sensing on a metal substrate.

[0103] Example 8:

[0104] In this embodiment, the pressure and touch signals output by the dual-mode sensing stack 1 need to be led out to an external processing unit through physical traces. Specifically, the upper meshed silver electrode 7 and the lower meshed silver electrode 8 of the pressure sensing layer 4 extend to the edge of the pressure sensing layer 4 through silver paste vias or direct printing, and are connected to two independent signal lines on the FPC extension section (used for applying bias voltage and detecting current, respectively). The signal lines 21 corresponding to the multiple independent capacitor electrodes 11 of the capacitive sensing array 5 and the common ground line are also integrated on the FPC extension section. The shielding layer 6 (copper foil) is connected to the dedicated analog ground line on the FPC extension section through conductive adhesive or soldering. All signal lines extend along the FPC extension section. FPC is an abbreviation for flexible printed circuit board, which refers to a circuit board made of flexible materials such as polyimide (PI) or polyester (PET) as the substrate, and has the characteristics of being flexible, thin, and foldable.

[0105] Specifically, the aforementioned dual-mode sensing stack 1 can be applied to, for example... Figure 7 Surgical instrument: Bipolar electrocoagulation forceps, the bipolar electrocoagulation forceps includes two forceps 15, the gripping parts 16 of the two forceps are respectively fixedly connected to the first storage box 17 and the second storage box 18, the gripping parts 16 of the two forceps 15 are both fixedly connected to the base 19, and the opposite sides of the two gripping parts 16 are fixedly connected to the extension piece 20.

[0106] The dual-mode sensing stack 1 is mounted on the first storage box 17 and the second storage box 18. All signal lines 21 extend along the FPC extension section and then extend between the metal gripping area substrate 3 and the extension sheet 20. The FPC extension section is embedded in the shallow groove on the surface of the extension sheet 20 and fixed with medical adhesive, finally converging at the micro connector (base 19) at the tail of the tweezer handle. This wiring method does not occupy the finger contact surface 2 and does not affect the grip feel.

[0107] After exiting from the tail-end miniature connector (base 19), the signal is transmitted to the external signal processing unit via a multi-core shielded cable. The external signal processing unit is used to acquire the pressure signal and capacitive touch signal, and to perform feature extraction and subsequent control. It should be noted that the signal processing method, decision control algorithm, and actuator in this external signal processing unit are all subject to separate applications by the applicant and do not constitute the scope of protection claimed in this application. This device is only responsible for converting the touch position, contact area, and pressure of the fingertip into electrical signals usable by the backend. Therefore, the fingertip signal sensing device of this application, as the sensing front end of the intelligent sensing electrocoagulation tweezers, provides high-fidelity, high-sensitivity multi-dimensional operational feature data for subsequent intent discrimination, dynamic energy adjustment, and tissue protection.

[0108] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. The above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for sensing fingertip signals from the metal grip area of ​​a surgical instrument, comprising a dual-mode sensing stack (1), characterized in that, The dual-mode sensing stack (1) includes, in sequence from the finger toward the metal grip area substrate (3): a finger contact surface (2), a pressure sensing layer (4), a capacitive sensing array (5) and a shielding layer (6), wherein the pressure sensing layer (4) and the capacitive sensing array (5) are electrically insulated from each other. The pressure sensing layer (4) includes an upper gridded silver electrode (7) and a lower gridded silver electrode (8) and a piezoresistive ink layer (9) sandwiched between them. The upper gridded silver electrode (7) and the lower gridded silver electrode (8) are both grid-like structures formed by interwoven silver wires (10). The line width w of the silver wires (10) is 50 to 100 μm, and the mesh spacing d is 200 to 600 μm. The aperture ratio η of the upper gridded silver electrode and the lower gridded silver electrode satisfies the threshold range: 50% ≤ η ≤ 80%. When the mesh shape is square, the aperture ratio η = (1 − w / d)². The capacitive sensing array (5) includes multiple independent capacitive electrodes (11), and the diameter D of a single capacitive electrode (11) is greater than or equal to 10d. The shielding layer (6) is provided with a grounding terminal, which is used to electrically connect to the analog ground of the external acquisition circuit; the shielding layer (6) is DC isolated from the metal gripping area substrate (3).

2. The apparatus according to claim 1, characterized in that, The line width of the silver wire (10) of the upper gridded silver electrode (7) and the lower gridded silver electrode (8) is 70-80 μm, the mesh spacing d is 300-500 μm, and the aperture ratio η of the upper gridded silver electrode and the lower gridded silver electrode satisfies: 60%≤η≤70%.

3. The apparatus according to claim 1, characterized in that, The mesh shape of the upper meshed silver electrode (7) and the lower meshed silver electrode (8) is square, rhomboid or hexagonal, and the mesh is arranged periodically and uniformly.

4. The apparatus according to claim 1, characterized in that, An insulating isolation layer (12) is provided between the pressure sensing layer (4) and the capacitive sensing array (5). The thickness of the insulating isolation layer (12) is h≥80μm and the relative permittivity is 3.0~3.

5.

5. The apparatus according to claim 1, characterized in that, The capacitive sensing array (5) has 4 to 8 independent capacitor electrodes (11) arranged on a 20mm×15mm gripping area curved surface. The diameter of each capacitor electrode (11) is 3 to 5mm, and the diameter D and the mesh spacing d satisfy D≥10d and the electrode spacing ≥1.5mm.

6. The apparatus according to claim 1, characterized in that, The shielding layer (6) is connected to the analog ground of the acquisition circuit through a low-impedance trace, and the shielding layer (6) is DC isolated from the metal gripping area substrate (3) through an insulating layer or an air gap.

7. The apparatus according to claim 1, characterized in that, The shielding layer (6) is a copper foil, and the projection of the shielding layer (6) in the direction perpendicular to the dual-mode sensing stack (1) covers the entire projection area of ​​the capacitive sensing array (5).

8. The apparatus according to claim 1, characterized in that, The finger contact surface (2) is a medical silicone layer.

9. The apparatus according to claim 1, characterized in that, The thickness of the dual-mode sensing stack (1) and the gradual transition structure (14) of its edge are adapted to be embedded in the compensation thinning area (13) provided on the metal gripping area substrate (3), and the thinning amount of the compensation thinning area is 0.3 to 0.4 mm; stress relief grooves are provided on the surface of the dual-mode sensing stack (1) near the edge.

10. The apparatus according to claim 1, characterized in that, The total thickness of the dual-mode sensing stack (1) is 500-600 μm, and the layers are bonded together with medical-grade acrylic pressure-sensitive adhesive.

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