Pressure sensor and production and use thereof

Abstract

A pressure sensor structure, a method of manufacturing a pressure sensor structure, a method of using the pressure sensor structure, and a device incorporating the pressure sensor structure. The pressure sensor structure includes a chamber having a closed bottom and an open top; an array of working electrode surfaces disposed within the chamber and extending from the bottom of the chamber to the open top; the counter electrode is formed outside the cavity; wherein the chamber provided with the working electrode surface is configured to trap air when the chamber is immersed in a liquid; wherein the working electrode surface can make electrical contact from the outside of the chamber; and wherein, when air is trapped in the chamber, a change in capacitance between the working electrode and the counter electrode is a measure of a change in pressure of the liquid into which the chamber is immersed.

Description

Field of the Invention

[0001] The present invention broadly relates to a pressure sensor structure, a method of manufacturing a pressure sensor structure, a method of using the pressure sensor structure, and a device including the pressure sensor structure. Background Art

[0002] Any reference to and / or discussion of prior art in this specification should not in any way be taken as an admission that the prior art is widely known or forms part of the common general knowledge in the field.

[0003] Existing pressure sensors typically rely on solid-state sensing elements. When used in liquid environments, these pressure sensors face a performance dilemma: linearity, hysteresis, and sensitivity.

[0004] Embodiments of the present invention aim to provide an alternative pressure sensor structure, a method for manufacturing a pressure sensor structure, a method for using the pressure sensor structure, and a device including the pressure sensor structure, and preferably can solve at least one of the above problems. Summary of the Invention

[0005] According to a first aspect of the present invention, there is provided a pressure sensor structure comprising:

[0006] a chamber having a closed bottom and an open top;

[0007] an array of working electrode surfaces disposed within the chamber and extending from the bottom to the open top of the chamber; and

[0008] a counter electrode formed outside the chamber;

[0009] wherein the chamber in which the working electrode surface is disposed is configured to capture air when the chamber is immersed in a liquid;

[0010] wherein the working electrode surface is electrically accessible from outside the chamber; and

[0011] Wherein, when the air is trapped in the chamber, the change in capacitance between the working electrode and the counter electrode is a measure of the change in pressure of the liquid in which the chamber is immersed.

[0012] According to a second aspect of the present invention, there is provided a method for manufacturing a pressure sensor structure, comprising the following steps:

[0013] providing a chamber having a closed bottom and an open top;

[0014] an array of working electrode surfaces disposed within the chamber and extending from the bottom of the chamber to the open top;

[0015] forming a counter electrode outside the chamber; and

[0016] configuring the chamber within which the working electrode surface is disposed to capture air when the chamber is immersed in a liquid;

[0017] wherein the working electrode surface is electrically accessible from outside the chamber; and

[0018] Wherein, when the air is trapped in the chamber, the change in capacitance between the working electrode and the counter electrode is a measure of the change in pressure of the liquid in which the chamber is immersed.

[0019] According to a third aspect of the present invention, there is provided a method of measuring pressure using the pressure sensor structure of the first aspect, the method comprising the step of monitoring a change in capacitance between a working electrode and a counter electrode as a measure of a change in pressure of a liquid in which a chamber is immersed.

[0020] According to a fourth aspect of the present invention, there is provided a device comprising the pressure sensor structure of the first aspect.

[0021] BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Those skilled in the art will better understand and more readily appreciate the embodiments of the present invention from the following written description which is given by way of example only and in conjunction with the accompanying drawings, in which:

[0023] Figure 1A A schematic diagram of a manufacturing process of a sensor according to an example embodiment is shown.

[0024] Figure 1B A scanning electron microscopy (SEM) image of a device structure of a sensor with a shadow mask according to example embodiments is shown.

[0025] Figure 1C An SEM image of a half-device structure of a sensor with a half-shadow mask cover is shown according to example embodiments.

[0026] Figure 1D An SEM image of a half-device structure of a sensor without a shadow mask is shown according to example embodiments.

[0027] Figure 1E A photograph of a sensor according to an example embodiment is shown.

[0028] Figure 1F A photograph of a sensor according to another example embodiment is shown.

[0029] Figure 2AA schematic diagram of a sensor according to an example embodiment is shown; inset: an equivalent circuit of the sensor;

[0030] Figure 2B The load-unload performance of a sensor according to an example embodiment is shown.

[0031] Figure 2C A schematic diagram of the capacitor composition of a sensor according to an example embodiment is shown, along with surfaces labeled I-IV having different wetting characteristics for tuning the performance of the sensor.

[0032] Figure 2D Schematic diagram showing the performance of a non-ideal pressure sensor with forward / backward thresholds and an ideal pressure sensor with linear and hysteresis-free performance.

[0033] Figure 2E A comparison of the linearity of the sensor according to the preferred embodiment and reported liquid ambient pressure sensors is shown.

[0034] Figure 2F Shown is an SEM image of a hexagonal array device (without pillars) used to study the wettability of surfaces I-IV in an example embodiment.

[0035] Figure 2G The composition of surface IV, the associated wettability, and the resulting device performance in a sensor according to example embodiments are shown.

[0036] Figure 2H The composition of surface III, the associated wettability, and the resulting device performance in a sensor according to example embodiments are shown.

[0037] Figure 2I The composition of surface II, the associated wettability, and the resulting device performance in a sensor according to example embodiments are shown.

[0038] Figure 2J The composition of surface I, the associated wettability and the resulting device performance in a sensor according to a preferred embodiment are shown.

[0039] Figure 2K Plots of the root mean square roughness versus the corresponding advancing angle and contact angle hysteresis for surfaces I-IV are shown; data are mean ± SD (five samples).

[0040] Figure 2L Graphs showing advancing angles and advancing thresholds for sensors having surfaces I-IV according to example embodiments are shown; data are mean ± standard deviation (five samples).

[0041] Figure 2MGraphs showing contact angle hysteresis and receding thresholds for sensors having surfaces I-IV according to example embodiments are shown; data are mean ± standard deviation (five samples).

[0042] Figure 2N Graphs showing contact angle hysteresis and hysteresis (%) for sensors having surfaces I-IV according to example embodiments; data are mean ± standard deviation (five samples).

[0043] Figure 2O Figure 2 shows the relationship between the simulated contact area changes in hexagonal array devices (each device has 169 hexagonal cavities; side length is 40 μm) with surface I-IV treatments and the measured capacitance changes of the corresponding devices. All changes are linear (R2>0.99); data are mean ± SD (five samples).

[0044] Figure 3A SEM images of half a 3D-printed hexagonal wall pillar array device (cross section; scale bar, 200 μm), dome-shaped pillar tips (scale bar, 10 μm), and nanostructures ((120sPAni) / Cr / Au / ODTSAM, total thickness 400 nm) on the pillar surface (scale bar, 100 nm) are shown for use in a sensor according to an example embodiment.

[0045] Figure 3B Confocal images of top views and cross-sectional profiles of water-air interface motion in a hexagonal pilaster array structure for an example embodiment under varying pressure (0-10 kPa) are shown; scale bar, 200 μm.

[0046] Figure 3C The loading-unloading behavior of a sensor according to an example embodiment is shown for different pressure ranges.

[0047] Figure 4A An SEM image of a hexagonal wall pillar array device structure according to example embodiments is shown, wherein the center-to-center spacing between adjacent pillars is 37.5 μm.

[0048] Figure 4B An SEM image of a hexagonal wall pillar array device structure according to example embodiments is shown, wherein the center-to-center spacing between adjacent pillars is 50 μm.

[0049] Figure 4C An SEM image of a hexagonal wall pillar array device structure according to example embodiments is shown, wherein the center-to-center spacing between adjacent pillars is 100 μm.

[0050] Figure 4D The sensitivity performance of a sensor according to an example embodiment is shown as a function of post spacing.

[0051] Figure 4EThe hysteresis performance of a sensor according to an example embodiment is shown as a function of post spacing.

[0052] Figure 4F The linearity (R2) performance of a sensor according to an example embodiment is shown as a function of post spacing.

[0053] Figure 5 Shown are the performance differences between single hexagonal, pillar array, and hexagonal wall pillar array structures in the 0–15 kPa range; all devices use surface I treatment.

[0054] Figure 6 The graph shows a comparison of cycle tests between the sensor according to the embodiment and a commercial sensor (with a built-in resistor and no external circuit) in the range of 0-50 Pa.

[0055] Figure 7 shows the short-time Fourier transform spectrum of a sensor of an example embodiment tested underwater, with a swept frequency acoustic wave of 0–1 kHz applied;

[0056] Figure 8 A graph showing 1,000 cycle durability testing of a sensor according to an example embodiment in the range of 0-5 kPa is shown.

[0057] Figure 9 Shown is a comparison of the advancing angle and contact angle hysteresis of the superslippery surface (surface I, containing 5 cSt silicone oil) before and after 10,000 immersions in 1× PBS solution; data are expressed as mean ± SD (3 samples), and corresponding data points are overlapped.

[0058] Figure 10A Shown is the change in linearity (assessed using R2) over time when the sensor is immersed in 1× PBS solution and pressures are maintained at 0 kPa, 10 kPa, and 15 kPa (three devices at each pressure), as well as the recovery of performance after reapplying lubricant; data are expressed as mean ± SD (three samples).

[0059] Figure 10B The figure shows the change in hysteresis over time when the sensor is immersed in 1×PBS solution and the pressure is maintained at 0 kPa, 10 kPa, and 15 kPa (3 devices at each pressure), as well as the recovery of performance after re-applying lubricant; the data are expressed as mean ± standard deviation (3 samples).

[0060] Figure 10C The figure shows the change in sensitivity over time after the sensor was immersed in 1× PBS solution and maintained at pressures of 0 kPa, 10 kPa, and 15 kPa (3 devices at each pressure), as well as the recovery of performance by reapplying lubricant; the data are expressed as the mean ± standard deviation (3 samples).

[0061] Figure 11 (Left) shows a photograph of a sensor according to an example embodiment under turbulent flow (Reynolds number up to about 6,400); (Right) shows a stability test diagram of the sensor according to an example embodiment under turbulent flow of different Reynolds numbers (0-6,400-0) generated by different stirring speeds (0-1,000-0rpm) under synchronous circulating pressure (0-10kPa).

[0062] Figure 12 A diagram illustrating the relationship between capacitance response and gravity of a sensor tested at different orientations according to an example embodiment is shown.

[0063] Figure 13 Comparison of sensing performance of a sensor according to an example embodiment after exposure to a bovine serum albumin (BSA) solution and after packaging according to another example embodiment is shown.

[0064] Figure 14 A photograph of a sensor according to an example embodiment is shown, the interior of the sensor being filled with a 1×PBS solution (1x PBS solution) and encapsulated with an Ecoflex / Parylene dome.

[0065] Figure 15A Graphs illustrating performance of a sensor before and after packaging according to example embodiments are shown.

[0066] Figure 15B Graphs showing cycle tests of a sensor in the range of 0-10 kPa before and after packaging according to example embodiments are shown.

[0067] Figure 16 The capacitive response of sensors according to example embodiments at different temperatures is shown; the devices were tested in a 1×PBS solution under cyclic pressure.

[0068] Figure 17A A photograph of a rat skull is shown with a sensor and a high-resolution barometer mounted thereon according to example embodiments.

[0069] Figure 17B A schematic diagram illustrating the operating principle of wireless ICP sensing according to an example embodiment is shown.

[0070] Figure 17C Shown is the frequency reading as a function of pressure; inset: photograph of a sensor according to an example embodiment.

[0071] Figure 18Wireless monitoring of intracranial pressure (ICP) in a rat using a sensor according to example embodiments is shown (bottom); applied pressure is tracked by a commercial barometer (top).

[0072] Figure 19 A schematic diagram of the working mechanism of a surgical grasper equipped with a sensor according to an example embodiment is shown, and the grasper is used for pressure sensing during surgery; one of the grasper jaws is equipped with a compressible liquid chamber, which is connected to the sensor chamber via a thin tube filled with PBS; when the grasper grasps tissue, the pressure is transmitted to the sensor according to the example embodiment through the squeezed liquid.

[0073] Figure 20A Shown Figure 19 Technical drawing showing the dimensions of the receptor in the grasping forceps; elastic cap with protrusions (top); rigid fluid chamber (bottom); units used are millimeters.

[0074] Figure 20B A photograph is shown of a grasper integrated with a receiving cavity on a jawbone according to an exemplary embodiment.

[0075] Figure 20C A photograph is shown of a sensor located in a sealed cavity according to an exemplary embodiment, the sensor being used in a grasping forceps according to an exemplary embodiment.

[0076] Figure 20D The sensing performance of sensors integrated with a lumen according to an embodiment is shown; the sensors exhibit high linearity (R2 = 0.99646 ± 0.00112), low hysteresis (5.66 ± 1.38%), and high sensitivity (215.2 ± 5.6 pFN-1) (three devices).

[0077] Figure 20E A graph shows grip force values ​​recorded over time by sensors integrated with grasping forceps while grasping artificial tissue, according to an embodiment. Several scenarios were tested experimentally, including grip adaptation through position sensing, detecting slippage caused by insufficient force, and maintaining a secure grip with appropriate force. Different shaded areas represent operational cycles.

[0078] Figure 21 A photograph showing a test setup for characterizing the pressure sensing performance of a sensor according to an embodiment is shown.

[0079] Figure 22A Graphs showing the evolution of the advancing angle over time for surfaces coated with 350 cSt and 5 cSt silicone oils according to the Examples are shown. The data are presented as mean ± standard deviation (3 samples).

[0080] Figure 22BShown are graphs of contact angle hysteresis versus time for surfaces coated with 350 cSt and 5 cSt silicone oils according to the Examples; data are presented as mean ± standard deviation (3 samples).

[0081] Figure 23A The linearity (assessed using R2) of sensors coated with 350 cSt and 5 cSt silicone oils, according to the Examples, changes over time. The devices were immersed in a 1× PBS solution and subjected to a constant pressure of 15 kPa. Sensing performance was restored by reapplying the corresponding silicone oil. Data are presented as mean ± SD (3 samples).

[0082] Figure 23B A graph showing the hysteresis variation over time for sensors coated with 350 cSt and 5 cSt silicone oils, according to an embodiment. The sensors were immersed in a 1× PBS solution and subjected to a constant pressure of 15 kPa. Sensing performance was restored by reapplying the corresponding silicone oil. Data are presented as mean ± SD (3 samples).

[0083] Figure 23C A graph showing the sensitivity of sensors coated with 350 cSt and 5 cSt silicone oil over time, according to an embodiment. The sensors were immersed in a 1× PBS solution and subjected to a constant pressure of 15 kPa. Sensing performance was restored by reapplying the corresponding silicone oil. Data are presented as mean ± SD (3 samples).

[0084] Figure 23D The performance graphs of the sensor coated with 5 cSt silicone oil in the initial state, after 5 days, and after re-applying silicone oil are shown according to an embodiment.

[0085] Figure 23E Performance curves of a 350 cSt coated sensor in its initial state, after 5 days, and after re-oiling are shown according to an example embodiment.

[0086] Figure 23F This graph shows how the viscosity of the coating oil affects the sensor's hysteresis performance, when the sensor, according to an exemplary embodiment, was coated with the same volume of oil (5 μL, 0.1% v / v silicone oil diluted in n-heptane) and tested at the same pressure (0-10 kPa). Data are presented as mean ± standard deviation (3 samples), with corresponding data points overlaid.

[0087] Figure 24 Graphs showing sensing performance of a sensor according to an example embodiment, coated with 1 kcSt silicone oil, at different pressure change rates.

[0088] Figure 25AThe graph shows the effect of the pressure change rate on the sensitivity of a sensor coated with 5 cSt silicone oil according to an example embodiment. The data are expressed as mean ± standard deviation (3 samples).

[0089] Figure 25B The effect of pressure change rate on the linearity of the sensor of the embodiment coated with silicone oil (5 cSt) is shown. The data are expressed as mean ± standard deviation (3 samples).

[0090] Figure 25C The effect of pressure change rate on hysteresis of an example sensor coated with silicone oil (5 cSt) is shown. The data are presented as mean ± standard deviation (3 samples).

[0091] Figure 26A The effect of test signal frequency on the performance of an example sensor is shown, sweeping from 20 Hz to 2 MHz, with no external pressure applied.

[0092] Figure 26B The capacitance response at different frequencies is shown when cyclic pressure is applied to the example sensor.

[0093] Figure 27A The effect of the volume of coating diluent oil on the sensitivity of the sensor of the embodiment is shown, where the volume of coating diluent oil is 0.1% v / v 5 cSt silicone oil diluted in n-heptane. The data are expressed as mean ± standard deviation (5 samples).

[0094] Figure 27B The effect of the volume of coating diluent oil on the linearity of a sensor according to an example embodiment is shown, along with the volume of coating diluent oil (0.1% v / v 5 cSt silicone oil diluted in n-heptane). Data are presented as mean ± standard deviation (5 samples).

[0095] Figure 27C The effect of the volume of applied diluent oil on the hysteresis of a sensor according to an example embodiment is shown, along with the volume of applied diluent oil (0.1% v / v 5 cSt silicone oil diluted in n-heptane). Data are presented as mean ± standard deviation (5 samples).

[0096] Figure 28A Photographs of bubbles in a sensor under a range of negative pressures are shown according to an example embodiment.

[0097] Figure 28B The sensing performance of the sensor according to an example embodiment is shown over a pressure range of -2 kPa to 15 kPa.

[0098] Figure 28C A graph illustrating sensing performance of a sensor according to an example embodiment over a pressure range of -4 kPa to 15 kPa is shown.

[0099] Figure 28D A graph illustrating sensing performance of a sensor according to an example embodiment over a pressure range of 0 to 50 kPa is shown.

[0100] Figure 29 A flow chart of a method for manufacturing a pressure sensor structure according to example embodiments is shown. DETAILED DESCRIPTION

[0101] An embodiment of the present invention provides a miniature pressure sensor that can achieve accurate static and dynamic pressure sensing in a liquid environment or with liquid as the working medium, and has high sensitivity, ultra-high linearity and ultra-low hysteresis. The sensor according to the example embodiment utilizes aeroelasticity, fine structural design, multi-scale ultra-slippery surface and double layer effect at the electrode-liquid interface to output changes in liquid pressure in a capacitive manner. The sensor according to the example embodiment can be made into a miniature size and can evaluate pressure changes under turbulence, internal body and acoustic vibration. It should be noted that the example embodiments are not limited to pressure sensors intended to work "directly" in a liquid environment, but also include pressure sensors intended to be used in various environments (including non-liquid environments) with liquid as the working medium.

[0102] A preferred embodiment of the present invention adopts a pressure-modulated solid-liquid-liquid-gas four-phase line motion mechanism, which is implemented in a wall pillar array structure. The surface of the structure has low surface energy, hydrophobicity, and is frictionless in terms of sliding friction of related liquids (such as water), collectively referred to as super-slippery surfaces in this article.

[0103] Embodiments of the present invention are inspired by the biomimicry of the surfaces of lotus leaves and pitcher plants (Nepenthes). The surface of the lotus leaf is superhydrophobic and has a hierarchical microstructure with low surface energy. When the lotus leaf is immersed in water, the surface can capture an air layer, so that a bright reflective layer can be observed. The trapped air layer is elastic and deforms with changes in water pressure. Inspired by this phenomenon, according to an exemplary embodiment, a pressure sensor is provided that utilizes the aeroelasticity of trapped air and a multi-scale microstructure that is processed to be ultra-slippery. In an exemplary embodiment, the sensor includes a microstructure electrode and a flat counter electrode. According to an exemplary embodiment, the microstructure electrode is a columnar array with dome-shaped tips and is surrounded by a wall, such as, but not limited to, a hexagonal wall in the exemplary embodiment described herein. In an exemplary embodiment of the manufacturing method, the structure is printed using a dual photopolymerization tool. In an exemplary embodiment, gold is first deposited on the surface of the microstructured electrode to make it conductive, then polyaniline nanowires are electrochemically deposited to give the surface nanotexture, followed by another layer of gold deposited on the polyaniline nanowires to enhance the conductivity of the nanotexture layer and provide an interface for oleophilic treatment, then the gold surface is treated with 1-octadecanethiol to make it oleophilic, and finally silicone oil is coated on the surface to make it superlubricious.

[0104] The sensor according to the example embodiment is pressure sensitive when immersed or encapsulated in a liquid containing ions that can move under the action of an electric field (such as salt water), so that a double-layer capacitor can be formed at the electrode-liquid interface. The sensor converts pressure changes into capacitance changes. When the liquid pressure changes, the liquid wets or dewets the surface of the microstructure electrode and changes the contact area between the liquid and the electrode, thereby changing the response of the interface capacitance to the pressure change. The sensor outputs the change by measuring the capacitance between the counter electrode and the microstructure electrode. The capacitance can be tested using an LCR meter or a capacitance meter under varying liquid pressure. In the example embodiment, the designed structure and low surface energy properties help to trap air in the sensor cavity. It will be understood by those skilled in the art that surface energy is related to the wettability of the surface. Materials with higher surface energy are more easily wetted than materials with lower surface energy, which means that, for example, water has poorer wettability on low surface energy surfaces and therefore has a larger contact angle. When the surface energy of the microstructure electrode is low, water will not completely wet the cavity, thereby ensuring that air is trapped in the cavity, forming a compressible air layer (see also below Figure 2A ).

[0105] The conductive surface beneath the coating oil and the double-layer effect at the oil-liquid interface enable high-capacitance output. The elasticity of the trapped air enables reversible wetting and dewetting as the liquid pressure changes. The surface of the device according to the exemplary embodiment mimics the surface of a pitcher plant, imparting a low-friction, preferably frictionless, surface, also referred to herein as a super-slippery surface, thereby preferably achieving zero hysteresis. The hexagonal pilaster array structure in the exemplary embodiment described herein enables a linear relationship between pressure and output capacitance.

[0106] The working mechanism of the exemplary embodiment includes: 1. Air elasticity; 2. Pillar array structural design; 3. Super-slippery surface, that is, a surface with low surface energy, hydrophobicity and no friction in terms of liquid sliding friction; 4. Interface capacitance. The sensor structure according to the exemplary embodiment creates a space for capturing air, and the liquid does not completely infiltrate the structural space (also referred to as the chamber herein). Because air is elastic and compressible, the liquid (for example, the 1×PBS solution during the test process) can enter and exit the chamber by liquid pressure. The interface capacitance is composed of the double layer capacitance and the surface coating dielectric layer capacitance, which is proportional to the contact area between the 3D electrode surface and the liquid. The super-slip surface preferably allows the solid-liquid-liquid-gas interface of the 3D electrode surface to generate resistance and frictionless motion. The structural design according to the exemplary embodiment preferably forces the infiltration direction of the liquid to be along the columnar structure, which, combined with the air elasticity, makes the contact area between the liquid and the solid linearly proportional to the liquid pressure.

[0107] During operation, when external liquid pressure is applied, the liquid-gas interface sags toward the inner cavity of the sensor according to the exemplary embodiment. In the initial state, when a low external pressure (0-approximately 2 kPa) is applied, only the center of the liquid-gas interface sags, and the central pillars pierce the interface, increasing the contact area between the pillars and the liquid, thereby increasing the capacitance and enabling the sensor to respond to low pressures. Higher pressure increases the depth of the pillars penetrating the liquid from the center of the chamber to the sides / periphery, and the contact area increases linearly with pressure. As pressure increases (greater than approximately 2 kPa and less than 15 kPa), the entire liquid-gas interface moves synchronously into the chamber, and the contact area increases linearly with pressure. When pressure exceeds 15 kPa, air becomes more difficult to compress due to its compressibility. The air pressure in the chamber is inversely proportional to the air volume, so the contact area cannot maintain a linear relationship with the external liquid pressure. Due to the ultra-slippery surface properties of the electrode surfaces in the exemplary embodiment, when external pressure decreases, the liquid-gas interface exhibits a linear relationship with pressure, preferably without hysteresis, returning to its initial state.

[0108] It is noteworthy that the adhesion between liquid molecules and nanoscale rough solid surfaces can lead to liquid pinning. This pinning effect can cause hysteresis in the contact line motion, resulting in poor response of the contact line motion to pressure changes. Therefore, in one exemplary embodiment, a super-slippery surface is provided on the pillars to reduce (and preferably eliminate) liquid pinning and the associated hysteresis in the contact line motion.

[0109] The biomimetic aeroelastic pressure sensor according to the exemplary embodiment is different from the traditional solid-state pressure sensor and can exhibit nearly ideal sensing performance. Using a strategy of multi-scale structured electrodes to capture air and eliminate nanoscale surface pinning, a membraneless pressure sensor design is created according to the exemplary embodiment, which can exhibit nearly ideal performance in a preferred embodiment. For the preferred embodiment described herein, the highest linearity with ultra-low hysteresis and high sensitivity in a liquid environment to date is achieved (ultra-high linearity (R square = 0.99944 ± 0.00015, nonlinearity = (1.49 ± 0.17)%), ultra-low hysteresis ((1.34 ± 0.20)%) and high sensitivity (79.1 ± 4.3 pF / kPa)). The design rules of this membraneless sensor according to the exemplary embodiment will be further explained below. Wireless and implantable devices for monitoring intracranial pressure, and sensing surgical forceps for feedback of gripping force during laparoscopic surgery are presented as example industrial application cases. According to various exemplary embodiments, the flexibility of structural design and surface modification can enable further tuning and customization of sensing performance for various application scenarios, such as pressure monitoring in dynamic fluids or as acoustic underwater hydrophones. It is expected that the strategies proposed for pressure sensing under different liquid and ambient pressures according to the exemplary embodiments will be widely applicable to pressure monitoring applications with ultra-high accuracy and high sensitivity.

[0110] Figure 1A The manufacturing process is shown. Figure 1B -F shows a sensor image according to an example embodiment. Specifically, Figure 1B 1 shows an SEM image of a device structure 150 with a shadow mask cover 151 of a sensor according to an example embodiment, Figure 1C A half device structure 152 with a shadow mask cover 153 is shown. Figure 1D A half device structure 154 is shown without the shadow mask. Shadow masks 151 and 153 are designed to reduce the exposed area of ​​the device during sputtering and to form a pattern of electrodes 156 for wiring. After surface treatment, shadow masks 151 and 153 are removed. Figure 1E A photograph of device 158 mounted on a flexible polyimide substrate 160 is shown. Figure 1F A photograph of a device 162 mounted on a glass substrate 164 is shown.

[0111] refer to Figure 1A , the detailed manufacturing steps according to the example embodiment are as follows:

[0112] 1.Structural design, printing and sputtering:

[0113] The device structure was designed in SolidWorks and printed using a two-photon polymerization lithography system (Photonic Professional GT2, Nanoscribe GmbH & Co. KG), marked as 100. For the hexagonal wall pillar array structure of the exemplary embodiment (e.g., 102), the outermost side length of each side of the hexagonal wall is 615 μm, the height is 520 μm, and the wall thickness is 20 μm. The periodic pillars are arranged in a hexagonal lattice with a spacing of 50 μm. The diameter and height of the pillars with dome tips are 25 μm and 500 μm, respectively. The lower part of the pillar is reduced to 12.5 μm to expand the air volume within the chamber. A grid is used at the bottom of the pillar to further fix the pillar (e.g., see Figure 1C 157 in ). Add a cover to the outside of the structure to act as a shadow mask for the sputtering (see also Figure 1B-1D ), thereby forming an electrode pattern for wiring (see, for example, Figure 1B Figure 156 in the figure) and limit the initial exposed working electrode area. Printing was performed using negative photoresist IP-S (Nanoscribe GmbH & Co. KG) and a 25x objective lens. The printed structure was developed in propylene glycol monomethyl ether acetate (PGMEA, Sigma-Aldrich) for 50 minutes. Subsequently, the printed structure was developed with isopropyl alcohol (Fisher Scientific) and Novec TMThe sample was cleaned with 7100 Engineering Fluid (Sigma-Aldrich) for 5 minutes and then dried. The device structure was then sputter-coated with 50nm / 600nm Cr / Au (indicated by numeral 103) to make the 3D structure conductive. Notably, this process is suitable for mass production of pressure sensor 3D structures, as shown by the fabrication of multiple 3D structures 102 and 104 in a single printing process.

[0114] 2. Surface treatment:

[0115] Different surface treatment methods were used in different exemplary embodiments, also referred to herein as surfaces I-VI. According to a preferred exemplary embodiment, the surface treatment method, also referred to herein as "surface I," was achieved by depositing polyaniline (PAni) nanowires (indicated by numeral 106) followed by sputtering of a Cr / Au layer, 1-octadecanethiol treatment, and oiling (collectively indicated by numeral 108).

[0116] 2.1 Deposition of polyaniline nanowires to form a porous rough nanotexture on the device microstructure. In an exemplary embodiment, the growth of polyaniline nanowires is accomplished by electrochemical deposition. A 2M sulfuric acid (95-97%, Sigma-Aldrich) and 0.5M distilled aniline (Sigma-Aldrich) solution is prepared. The device (e.g., 102) is then immersed in the prepared solution, and a vacuum is applied to press the liquid into the 3D structure. For the electrochemical deposition process, the electrochemical cell is assembled into a three-electrode structure, in which the counter electrode is platinum (Pt), the reference electrode is silver / silver chloride, and the working electrode is a metallized 3D printed structure. Deposition is then performed using an electrochemical workstation (Zahner Zennium E) at a constant potential of 0.75V for 120 seconds. The device is rinsed with deionized water and dried in an oven at 70°C for 1 hour.

[0117] 2.2 Sputtering Cr / Au. Sputter another layer of Cr / Au onto the surface of the polyaniline nanowires to form a hydrophobic interface. The thicknesses of the Cr and Au layers are 10 nm and 120 nm, respectively.

[0118] 2.3 Octadecanethiol (ODT) Treatment. ODT treatment renders the surface of the gold-coated polyaniline nanowires hydrophobic and oleophilic. The treatment method is to prepare a 0.5% v / v ODT solution in anhydrous ethanol and soak the device overnight. After removal, the device is rinsed with ethanol and dried with an air gun.

[0119] 2.4 Oil coating. The oil coating is used to lubricate the surface and make it super-slippery. 0.1% silicone oil (5 cSt, Sigma-Aldrich) was diluted in n-heptane (anhydrous, 99%, Sigma-Aldrich) and applied to the ODT-treated surface. The volume of the silicone oil was controlled using a microsyringe and the silicone oil was added dropwise to the structured working electrode to obtain super-slippery properties. The diluted silicone oil filled the voids in the porous nanostructure. The solvent (n-heptane) evaporated naturally at room temperature. It should be noted that the oiling step was performed after the device assembly was completed.

[0120] 3. Counter electrode preparation:

[0121] A planar counter electrode 120 and an electrode 121 for connecting to a 3D-printed structure 126 were fabricated on a glass slide 122 using photolithography. Typically, 10 nm of chromium and 70 nm of gold were sputtered onto a clean glass slide (a flexible polyimide substrate in various embodiments). A positive photoresist (AZ1512HS, Merck) was then patterned and spin-coated onto the glass slide using UV photolithography. Electrode patterns 120 and 121 were then obtained by etching with a gold etchant (Sigma-Aldrich) and a chromium etchant (22% cerium ammonium nitrate (Sigma-Aldrich) and 8% acetic acid (TCI) in deionized water, respectively). A polyimide insulating layer 124 was fabricated using positive photoresist-assisted photolithography. A 15.0–16.0% solution of poly(pyromellitic dianhydride-co-4,4′-oxydianiline) amic acid (Sigma-Aldrich) was spin-coated onto the substrate. A soft bake was performed at 100°C for 3 minutes, followed by spin coating of AZ1512HS and a soft bake at 100°C for 1 minute. The sample was exposed to UV light and then developed in 2.38% tetramethylammonium. The alkaline tetramethylammonium developer continued to etch the uncrosslinked amic acid layer after rinsing the UV-exposed areas of the AZ1512HS layer. The sample was rinsed with deionized water, and the AZ photoresist was removed with propylene glycol monomethyl ether acetate. Afterwards, a hard bake was performed at 200°C for 2 hours. For the fabrication of flexible flat electrodes, an initial step of spin coating of an amic acid solution and photolithography was added to create a flexible substrate, and the same steps as above were then followed.

[0122] 4. Device assembly:

[0123] The structural working electrode, i.e., a metallized 3D-printed structure, such as 104, with various types of surface treatments, is manually transferred and electrically connected to a planar electrode 121 on a glass slide (or a flexible polyimide substrate in various exemplary embodiments) via adhesion of silver paste (Paron-910, Chang Sung Corp.). Notably, after surface treatment, the printing masks 107 and 109 are removed. The exposed conductive wiring areas 125 of the 3D-printed structure 126 are encapsulated with SU-82002 (MicroChem). Depending on the intended application environment of the pressure sensor in various exemplary embodiments, the sensor can be used as shown by numeral 128. In another exemplary embodiment, a 3D-printed structure, such as 126, is filled with 1× phosphate buffered saline (PBS, BioWhittaker) and then encapsulated in an Ecoflex / Parylene-C preformed dome 130 while immersed in PBS, thereby forming a pressure sensor 132 suitable for various environments, which uses a liquid (PBS in this example) as the working medium.

[0124] Operational mechanisms according to example embodiments.

[0125] Figure 2A A schematic diagram of a sensor 200 according to an example embodiment is shown. The surface of a pillar (e.g., 202) serves as a working electrode 203 and is modified to be super-slippery by injecting a lubricant into the conductive nanostructure, as described above in step "2. Surface Treatment." The liquid 204 can wet / dewet the pillar electrode 203 under varying liquid pressures, preferably without contact angle hysteresis. This process changes the liquid 204-working electrode 203 contact area, thereby changing the capacitance. The inset shows an equivalent circuit 206 of the sensor 200, where C counter is the electric double layer (EDL) capacitance at the liquid 204-counter electrode 208 interface; C EDL.ct is the EDL capacitance at the interface between the liquid 204 and the coating on the columnar surface (e.g., 202); C d.ct is the dielectric capacitance between the working electrode 203 and the interface between the coating on the surface of the column (e.g., 202) and the liquid 200; C d+air is the capacitance between the working electrode 203 and the liquid 200 through the entrained air; C0 is the interfacial capacitance of the inactive area outside the 3D structure.

[0126] Figure 2B The pressure sensing response of a sensor according to an example embodiment is shown.

[0127] Figure 2CA schematic diagram of the capacitor components of sensor 250 according to an example embodiment is shown, along with schematic diagrams of the surfaces of pillars (e.g., 252) labeled I-IV having different wetting characteristics for adjusting the performance of sensor 250, wherein the circuit labels correspond to Figure 2A In the inset, Δθ is the contact angle hysteresis of the surface. As the surface roughness decreases from IV to I, Δθ also decreases, indicating that the liquid transitions from strong pinning to frictionless sliding. These changes in surface properties affect sensor performance in various exemplary embodiments.

[0128] Figure 2D Schematic diagram showing the performance of a non-ideal pressure sensor with forward / backward thresholds and an ideal pressure sensor with linear and hysteresis-free performance.

[0129] Figure 2E The linearity comparison of the sensor designed according to the example embodiment (labeled as eAir) and the reported liquid ambient pressure sensor (see references [1]-

[10] ) is shown. To highlight the difference, the linearity (1 / (1–R 2 )) for comparison. 2 (Coefficient of Determination) is the linear fitting result value of the corresponding device performance curve: the higher the linearity, the better the linearity.

[0130] According to example embodiments, the sensor is optimized.

[0131] In order to utilize trapped air for electronic pressure sensing, it is best to regulate the movement of the contact wire through the electric double layer (EDL) to convert pressure into capacitance. The moving contact wire changes the contact area of ​​the solid-liquid interface, thereby changing the interfacial capacitance generated by the EDL. According to example embodiments, the correlation between the advancing angle and the sensing threshold, as well as the correlation between the contact angle hysteresis and the sensing hysteresis, are revealed and studied. These results show that pressure sensing can be optimized by precisely controlling the structural design and surface chemical properties described in the embodiments. The sensing method described in the embodiments is completely different from traditional solid-state pressure sensors. Such traditional pressure sensors are either not applicable or have performance limitations in liquid environments, such as low linearity, high hysteresis and low sensitivity. Therefore, these traditional sensors are not very suitable for aqueous environments or biomedical applications in body cavities, nor are they very suitable for sensors using liquid working media in various environments.

[0132] In contrast to these solid-state pressure sensors, the sensing strategy of the preferred embodiment of the present invention exploits the essentially pinning-free contact line motion of a multi-scale structured solid-liquid-liquid-gas multiphase system, thereby creating a novel aeroelastic capacitive pressure sensor, also referred to herein as eAir TMSensor. According to an exemplary embodiment, the eAir sensor is a miniature (approximately 0.5 cubic millimeters) sensor that uses a hexagonal pilaster array microstructure, and its ultra-slippery surface design is inspired by the pitcher plant. Figure 2E As shown, compared with other pressure sensors working in liquid environments, according to example embodiments, the sensor can measure subtle pressure fluctuations in liquids and has ultra-low hysteresis (1.34±0.20%), high sensitivity (79.1±4.3pFkPa -1 ) and extremely high linearity (R 2 =0.99944±0.00015; nonlinearity 1.49±0.17%). As described in detail below, exemplary embodiments demonstrate that the eAir sensor can operate under various complex conditions, including turbulent flow, in vivo biological environments, and during laparoscopic surgery, achieving ultra-sensitive pressure monitoring.

[0133] It is noteworthy that for the regular open-cell microscale columnar array prepared by two-photon polymerization three-dimensional printing nanolithography technology and made into a pressure-sensitive device through metallization and hydrophobicization process, its surface exhibits poor repeatability, as well as obvious hysteresis (21.8±7.7%) and forward threshold (1.6±0.5kPa) and backward threshold (2.2±0.3kPa). The inventors recognized that one of the reasons for the poor performance is that this open-cell columnar array sensor structure allows multi-directional liquid wetting under increased pressure. In order to limit the wetting of the liquid-solid-gas three-phase contact line to one direction, a closed-cell design is selected in an exemplary embodiment of the present invention. In a preferred exemplary embodiment, a hexagonal array structure is selected to achieve optimal air containment within a given volume and minimize electrode exposure at the top. The results show that according to the exemplary embodiment, the cycle repeatability of the closed-cell sensor is significantly improved. It is noteworthy that closed-cell columnar cavities of other shapes (such as circular) also help to improve the repeatability between cycles. Back Figure 2C , by adjusting the surface roughness and surface energy, surfaces I-IV with different advancing and receding contact angles were studied. Figure 2F As shown, for ease of fabrication, we obtained the modification and wetting properties using hexagonal array devices without pillars and are summarized in Table 1. It should be noted that the data shown in Table 1 are for Figure 2F The hexagonal array devices shown are obtained without pillars for ease of fabrication.

[0134]

[0135] Table I

[0136] As shown in Table I and Figures 2G to 2JAs shown in the example embodiment, the advancing contact angle of the liquid under increasing liquid pressure is greater than the static contact angle of water on the hydrophobic surface (which may be greater than 65° or greater than 90° according to different definitions) and is less than 160°, less than 135°, less than 115°, and less than 112°, respectively. In addition, the contact angle hysteresis between the advancing contact angle of the liquid under increasing liquid pressure and the receding contact angle of the liquid under decreasing liquid pressure is less than 75°, less than 40°, less than 30°, and less than 1°, respectively.

[0137] The differences in advancing angle and contact angle hysteresis on the differently treated surfaces are due to the fact that the contact line is affected by different degrees of surface roughness. Figure 2G and 2H As shown, PAni nanowire-induced surfaces III and IV exhibit high roughness, significantly enhancing the contact line pinning effect. Furthermore, under liquid pressure, such rough surfaces undergo an irreversible Cassie-Baxter to Wenzel transition, further increasing the advancing angle and contact angle hysteresis after pressure application.

[0138] As the surface roughness decreases to the nanometer level (surface II), the advancing angle and contact angle hysteresis also decrease accordingly, e.g. Figure 2I As shown. Driven by the large surface area provided by the porous PAni nanowires, after the surface I is coated with silicone oil, the surface becomes smooth and super-slippery at the molecular level, as shown Figure 2J As shown, this is similar to smooth liquid-infused porous surfaces (SLIPS) [11,12]. This significantly reduces the contact line pinning effect, thereby reducing the advancing angle and the contact angle hysteresis is negligible, as shown in Figure 2K As shown in Figure 2, the advancing angle and contact angle hysteresis of the four surfaces increase with the increase of roughness.

[0139] A clear trend of the effect of interfacial wetting characteristics on sensing performance was observed: e.g. Figure 2L As shown in , the larger the advance angle, the higher the advance threshold; Figure 2M As shown in Figures 1 and 2, the larger the contact angle hysteresis, the larger the retreat threshold and the hysteresis of the device. Figure 2O The relationship between the simulated contact area change and the measured capacitance change of the corresponding device in hexagonal array devices (169 hexagonal cavities per device; side length 40 μm) treated with surfaces I-IV is shown. All changes are linear (R 2 >0.99). Data are mean ± standard deviation (five samples).

[0140] The advancing angle and contact angle hysteresis of different surface types (I-IV) were also studied without and after applying liquid pressure (10 kPa) for 5 minutes. For surfaces with greater surface roughness (surfaces III and IV), both the advancing angle and contact angle hysteresis increased after pressure was applied, but this trend was not observed for smooth surfaces (surfaces I and II).

[0141] It should be noted that the present invention is not limited to the use of the above-mentioned surfaces. Instead, in various embodiments, other substantially frictionless 3D electrode structure surfaces may be used, including solid and quasi-solid material surfaces. In this regard, in various exemplary embodiments, those skilled in the art will appreciate that, based on different materials and / or different surface treatments, surfaces with similar properties may be used. Figure 2G-2O Other surfaces with similar properties as shown. For preferred embodiments, the contact angle hysteresis may be less than 10°, preferably less than 5°, and more preferably less than 3°.

[0142] In order to further solve the threshold effect and achieve high linearity, a hexagonal wall pillar array structure is selected in a preferred embodiment, such as Figure 3A As shown, the figure shows a scanning electron microscope (SEM) image (scale bar, 100 nm) of a 3D-printed hexagonal wall pillar array device 300 (cross section; scale bar, 200 μm), a pillar 303 with a dome-shaped pillar tip 301 (scale bar, 10 μm), and a nanostructure 302 ((120sPAni) / Cr / Au / ODT self-assembled monolayer (SAM), with a total thickness of 400 nm) located on the surface of the pillar (e.g., 303).

[0143] In a preferred embodiment, the hexagonal wall pillar array device uses an array of dome-shaped tip pillars to alleviate surface tension when the pillars penetrate the water surface under low load pressure conditions. This mitigation is achieved by reducing the length of the initial contact line and changing the direction of surface tension.

[0144] The diffusion resistance of liquids along smooth edges (such as the rounded edge of a dome tip) is much lower than along sharp edges. Once the device is immersed in water, the contact line on the dome tip moves more easily under low pressure. When the water surface contacts the curved dome tip under low external pressure, the contact angle (ideally 180 degrees) means that the contact line cannot maintain equilibrium. The contact line will move downward, seeking a position where the contact angle decreases to at least the advancing contact angle. Due to the unique shape of the curved dome, the reference plane for evaluating the contact angle is the tangent plane at the contact point, which moves as the contact line moves along the dome surface. Furthermore, because the advancing angle of surface I is approximately 111 degrees, in the absence of additional liquid pressure, the contact line only reaches equilibrium when it moves close to the cylindrical surface of the pillar. In a real wetting scenario, water diffuses from one side of the device to the other. During this diffusion process, the liquid front exerts additional pressure on the pillar, causing the pillar to penetrate deeper. It is important to note that the length of the contact line also increases with downward movement, which is determined by the hemispherical shape of the dome. Therefore, during the wetting process of the contact line on the dome, the initial inclination angle of the reference plane and the length of the contact line are both beneficial to reducing the surface tension resistance when the dome tip "penetrates" water under a smaller pressure.

[0145] In contrast, for the flat tip, since the top plane forms a 90-degree angle with the cylindrical surface of the cylinder at the top edge, the initial contact angle is 90 degrees with the cylindrical surface of the cylinder as a reference. The contact line length is initially the circumference of the cylinder, and the contact line is fixed at the top edge until the external pressure pushes the water to reach the advancing angle, at which point the contact line begins to move. To compare intuitively, as the external pressure gradually increases, the direction of the liquid surface tension at the contact line on the flat tip cylinder makes a larger angle with the horizontal plane when the contact line just reaches the advancing contact angle, resulting in a larger vertical component of the surface tension, which in turn leads to a larger resistance to downward wetting of water, resulting in a larger forward threshold.

[0146] Thus, the device with the rounded tip exhibited essentially no forward threshold, whereas the device with the flat tip exhibited a threshold of 1.32 ± 0.37 kPa.

[0147] Using the ultra-slippery surface I, the preferred embodiment with a dome-shaped cylindrical tip can achieve near-zero threshold, no hysteresis, and high linearity pressure sensing performance, such as Figure 2B Confocal microscopy images show the underwater wetting process of the device under different pressures, as shown in Figure 3B The well-overlapped cycle readings indicate excellent performance consistency across the pressure range, as shown in Figure 3CAs shown in Figure 2 , according to a preferred embodiment, the pillar array within the hexagonal wall structure minimizes the forward threshold. Compared to an empty hexagonal chamber, a small initial pressure only causes the liquid-air interface to sag slightly inward without increasing the liquid-electrode contact area. In contrast, according to a preferred embodiment, the pillar array within the hexagonal wall chamber increases the wetted contact area and the corresponding capacitance generated by the pillars at this "drooping" liquid-air interface caused by the small pressure.

[0148] In a preferred embodiment, these pillars are designed with rounded tips and a small diameter (25 μm) to further minimize the contact line movement resistance on the pillars by shortening the initial contact line length and changing the direction of surface tension (as described above). This helps these tips "pierce" the liquid-air interface under less pressure. By comparing the device performance under different pillar densities, we found that the optimal pillar spacing is 50 μm, as shown in Figure 2. Figures 4A-4C shown.

[0149] Therefore, the structural optimization iterations of a preferred embodiment involve three main structures: open-cell pillar arrays, closed-cell hexagonal arrays, and combinations thereof. Figure 5 The performance of the exemplary embodiment is significantly improved by the synergistic effect of the hexagonal wall and columnar array structure. This structural design can achieve a linear pressure-capacitance response, and its forward threshold is negligible even without a thrust angle close to 90°. Figure 6 As shown in Figure 1, the eAir sensor according to the preferred embodiment is able to measure very small pressures with a very high signal-to-noise ratio (SNR) compared to commercial in-vivo pressure sensors. It is worth noting that even with the use of a Wheatstone bridge to reduce noise, the SNR of commercial sensors is still low. This threshold-free feature also enables the response to small dynamic pressure changes, such as underwater acoustic vibrations up to 1kHz, such as Figure 7 shown.

[0150] In terms of stability, the eAir sensor according to the preferred embodiment showed a minimum change of 1.01% over 1,000 load-unload cycles of 0-5 kPa, as shown in Figure 2. Figure 8 The superslippery surface remained stable after 10,000 immersions in phosphate buffer solution (PBS), with negligible changes in advancing angle and contact angle hysteresis, as shown in Figure 2. Figure 9 As shown, it is highlighted that the surface I nanostructure used in the preferred embodiment has excellent lubricant locking ability.

[0151] In addition, if Figures 10A-10CAs shown in Figure 1, the eAir sensor according to the preferred embodiment can still maintain its function after 5 days under constant pressure, and the performance can be restored to its initial state by reapplying lubricant. Although the initial capacitance varies due to the different exposed wiring areas after the electrode insulation, the sensitivity of several eAir sensors according to the preferred embodiment remains consistent (79.1±4.3pFkPa-1). It is worth noting that the eAir sensor according to the preferred embodiment can operate stably even in a highly turbulent liquid environment with a Reynolds number of approximately 6,400, as shown in Figure 1. Figure 11 The device performance in turbulent flow was tested by using a magnetic stirrer (Wiggens digital hot plate / stirrer) to drive a stirring rod (4 cm long) to control the stirring speed in the range of 0-1,000 rpm, while the pressure was cycled between 0 and 10 kPa. To further test the stability, an additional setup was built to place the sensor in a rotating (12 rpm) environment, facing the turbulent flow in different directions. The results obtained with this setup are consistent with those of the Figure 11 The data shown are consistent, further demonstrating the stability of the device's performance under turbulent flow conditions. Furthermore, we tested the sensor in a turbulent flow environment without pressure cycling. When the Reynolds number is above 6,400, high turbulence creates air pockets and voids. Due to the intense mixing of the fluid, these air pockets and voids manifest as bubbles in the water. These bubbles attach to the sensor, causing a sudden drop in capacitance and subsequent breakdown.

[0152] Under turbulence caused by different stirring speeds, the capacitance changes steadily with the external hydrostatic pressure. The eAir sensor according to the preferred embodiment is also not affected by gravity because its internal spacing is much smaller than the capillary length (2.71 mm at room temperature), so it maintains consistent performance in tests at different angles, such as Figure 12 As shown, it should be noted that due to the overlap between the measurements, Figure 12 The different curves in are difficult to distinguish.

[0153] It was found that complex liquid environments (e.g., biological fluids) can affect the sensing behavior, e.g. Figure 13 To expand the usage scenarios of the eAir sensor according to the example embodiment, the sensor device is encapsulated in a thin Ecoflex / Parylene dome film filled with 1×PBS solution to isolate it from the external environment, as shown in FIG. Figure 14 As shown. Figure 15A and Figure 15B As shown, except for the initial capacitance increase, the performance of the packaged device does not change. Although the sensitivity increases with temperature, the eAir sensor according to the preferred exemplary embodiment still maintains high linearity and low hysteresis at different ambient temperatures, as shown in FIG. Figure 16 .

[0154] Animal testing for intracranial pressure (ICP) sensing was conducted using sensors according to example embodiments.

[0155] In vivo ICP monitoring was performed on male Sprague-Dawley rats (5-6 months old, 350-500 g, InVivos) using a sensor according to an example embodiment. The rats were anesthetized by inhalation of isoflurane (1-3%) and intraperitoneal injection of ketamine / xylazine (75 / 10 mg / kg (body weight)) and carprofen (5 mg / kg (body weight)). The hair was clipped from the top of the animal's head and the head was placed in a stereotactic apparatus (David Kopf Instruments) connected to an oxygen and isoflurane flow. Lubricating eye ointment (Alcon) was applied. After disinfection with iodine and isopropyl alcohol, an incision was made in the midline of the scalp, and two burr holes (approximately 2.5 mm in diameter) were created in the bilateral parietal bones through craniotomy using a high-speed drill (RWD LifeScience). Figure 17A As shown, an eAir sensor 1700, packaged on a flexible polyimide substrate and equipped with a wireless module according to an exemplary embodiment, and a sterile silicone tube 1701 with a commercial barometer (DLHR-L60D, Amphenol All Sensors) were connected to the left and right drilled holes, respectively, and sealed with dental cement (Parkell). All experiments were conducted in accordance with the Guide for the Care and Use of Laboratory Animals published by the National Institutes of Health, and the experimental protocol was approved by the Institutional Animal Care and Use Committee of the National University of Singapore.

[0156] Intracranial pressure (ICP) refers to the pressure generated by fluids such as cerebrospinal fluid within the skull and brain tissue. Normal ICP ranges from 5 to 15 mmHg (660 to 2,000 Pa), sustained pressures above 20 mmHg (2,660 Pa) are considered pathological, and severe ICP (greater than 40 mmHg (greater than 5,330 Pa)) indicates life-threatening intracranial hypertension 37. According to example embodiments, the small size and biocompatibility of the eAir facilitate continuous ICP monitoring. This study demonstrates wireless monitoring of ICP by attaching a packaged eAir sensor to a patterned flexible polyimide substrate in a rat model. Reference Figure 17B The eAir sensor 1700 and barometer (not shown) are mounted in corresponding drilled holes, for example, 1702 on a rat skull 1704. To enable wireless ICP readings, the eAir sensor 1700 is connected to a wireless module 1706 that continuously broadcasts an ICP signal to a nearby mobile device 1708. The eAir sensor 1700 is encapsulated in an Ecoflex dome filled with 1×PBS.

[0157] The oscillation circuit converts the pressure fluctuation into a frequency signal that can be digitized. Figure 17C As shown, the oscillator circuit is assembled on a 1712-type rigid printed circuit board (PCB, 18×25 mm) by micro-soldering (NAE-2A, JBC) three surface-mount thin-film resistors (CR0201-FW-1001GLF, CR0201-FW-2001GLF, and CR0201-FW-49R9GLF; Bourns) and a precision amplifier (AD8538WAUJZ-R7, Analog Devices). The oscillator circuit is further connected to a Bluetooth microcontroller unit 1714 (ESP32-WROOM-32D, Espressif Systems) to form a wireless module 1706. It should be noted that in Figure 17C In the example, the Bluetooth microcontroller unit 1714 is hidden under a lithium polymer battery 1716 (100 mAh, 3.7 V), which is powered by a voltage regulator (NCP167AMX330TBG, ON Semiconductor) to power the entire wireless module 1706. The polyimide substrate 1720 with the eAir sensor 1700 is attached to the PCB 1712 using anisotropic conductive tape (7303, 3M). The electronic components are encapsulated with medical silicone adhesive (Kwik-Sil Adhesive) for protection. The frequency response is read by the internal pulse counter of the ESP32 and sent via Bluetooth to an Android smartphone acting as a mobile device 1708 (see Figure 17B The oscillation frequency was also characterized by a mixed domain oscilloscope (MDO3012, Tektronix).

[0158] Calibrate the frequency response of the oscillating circuit to determine the relationship between frequency and pressure, such as Figure 17C The output of the wireless ICP sensor is in good agreement with the barometer output, as shown in Figure 18 As shown, the feasibility and effectiveness of the implantable ICP sensor according to the exemplary embodiment under complex in vivo conditions are verified. The minimally invasive nature and precise dynamic response of the eAir sensor make it a promising candidate for future ICP and other biofluid pressure monitoring.

[0159] According to an example embodiment, an eAir sensor is integrated with a laparoscopic surgical grasper.

[0160] refer to Figure 19, three eAir sensors 1900 are encapsulated in three identical closed chambers 1902 and configured with three corresponding receivers 1904 to form three tactile pixels, which are mounted in one jaw of a gripper with holes 1906 (5 mm in diameter) to evaluate tactile perception. The eAir sensor 1900 is fixed in the encapsulated chamber 1902 with Ecoflex. The receiver 1904 is designed as a rigid chamber 1908 covered by an elastic film 1910 with protrusions 1912 so that it can be fully deformed under external force. The eAir sensor encapsulated chamber 1902 and the receiver 1904 are designed using SolidWorks and printed using a stereolithography-based 3D printer (Formlabs3B+, Formlabs). The elastic top membrane 1910 and the rigid cavity 1908 of the compressible receiver 1904 are printed using commercially available flexible 80A resin and BioMedClear (Formlabs) resin, respectively. The dimensions of the receiver 1904 are as follows Figure 20A The photos of the mandibular receiver and eAir sensor are shown in Figure 20B and Figure 20C As shown. Back Figure 19 , chambers 1902 and 1908 are connected with PTFE tubing 1912 (0.3 mm inner diameter; 0.6 mm outer diameter, 25 cm length) to conduct liquid pressure between the receiver 1904 and the corresponding eAir package chamber 1902. The tactile feedback system is filled with 1×PBS solution, except for the interior of the pillar array of the eAir sensor 1900 due to the hydrophobic nature of the device structure (as described above), which is encapsulated under the liquid to avoid the generation of unnecessary bubbles. It is worth noting that in this embodiment, the Ecoflex dome is not used around the eAir sensor 1900. The various interconnects are sealed with BioMed clear resin and further cured to prevent liquid leakage under increased pressure.

[0161] To create the calibration matrix, a normal force (0-4 N) was applied to the top of the protrusion 1912 of the compressible receiver 1904 using a linear stage-driven digital force gauge (Mark-10MR03-5) with a probe (2 mm × 2.5 mm). To examine the trend of capacitance change under the influence of external force, the eAir sensor 1900 was characterized using three portable impedance analyzers (Digilent Analog Discovery 2). The three eAir sensors 1900 exhibited a linear response to external force. Due to the linear characteristics of the eAir sensor 1900, it can be easily calibrated using the calibration matrix. To verify the performance, the gripping force of the sensor-equipped laparoscopic grasper 1906 was measured. Data from the three eAir sensors 1900 were recorded simultaneously while grasping a reference "tissue" section made of dyed Ecoflex 00-50 (Smooth-On). The data was converted into force using the calibration method mentioned above.

[0162] Therefore, the eAir sensor 1900 can easily provide tactile sensitivity to laparoscopic surgical tools. More than 13 million laparoscopic surgeries are performed each year worldwide. When using laparoscopic graspers, improper gripping force can lead to high complication rates. For example, a study on laparoscopic cholecystectomy found that excessive force was the cause of 11.3% of consequential errors and 19.0% of insignificant grasper-related errors. However, due to large size, complex integration and limited performance, incorporating tactile sensing has been challenging. According to an example embodiment, the working principle of the eAir sensor 1900 relies on fluid, thereby allowing remote force sensing. In an exemplary embodiment of the laparoscopic grasper 1906 with sensor, the eAir sensor 1900 still can excellently transmit force with high linearity (R 2 =0.99646±0.00112), low hysteresis (5.66±1.38%) and high sensitivity (215.2±5.6pFN) -1 ),like Figure 20D shown.

[0163] Back to Figure 19, the application of real-time grip force monitoring in laparoscopic surgery was simulated using a laparoscopic surgical grasper 1906 with a sensor. An initial grasp of the tissue was performed by gradually advancing the grasper 1906 to achieve appropriate contact. The readings from the eAir sensor 1900 showed the precise contact position so that the grasping position could be adjusted accordingly. The tissue was then gently grasped and pulled. The readings showed a gradual decrease in contact pressure, indicating that the tissue was slipping due to insufficient gripping force. In actual laparoscopic surgery, such slippage could lead to patient injury. Finally, the tissue was grasped with greater force and the grasper was shaken. Slight changes in the eAir sensor 1900 readings were observed without any loss of contact, indicating that the jaws had a firm grip on the tissue and prevented tissue slippage, as shown in the figure. Figure 20E This test demonstrated the potential of the eAir sensor according to example embodiments to provide tactile feedback during laparoscopic surgery.

[0164] Testing a Sensor According to Example Embodiments

[0165] Figure 21 A test apparatus for a pressure sensor according to an example embodiment is shown. The sensor 2100 is characterized at different pressures using an LCR meter 2102 (Keysight E4980A). The LCR meter 2102 is set to the Cs-D (series capacitance-dissipation factor) function with a test signal level of 100 mVrms (100 kHz). The applied voltage is too small to induce electrowetting, which is confirmed by observing the device under a confocal microscope (Olympus FV3000) and applying an AC voltage of 100 mVrms. The sensor 2100 is encapsulated in a 1× phosphate buffer solution (PBS, BioWhittaker) in a custom sealed chamber 2104. It should be noted that in order to minimize the pressure difference between the air pressure in the sealed chamber and the pressure applied to the sensor (i.e., the pressure (depth) caused by the liquid itself), a small drop of 1× PBS is used to wrap the 3D structure so that the air pressure in the sealed chamber is consistent with the pressure applied to the sensor.

[0166] Cyclic pressure loading and unloading is achieved by pumping air into and out of a sealed chamber 2104 (i.e., the space above the 1× phosphate buffer solution) using a syringe 2108 driven by a linear stage 2106 and a high-precision commercial barometer 2110 (DLHR-L60D, Amphenol All Sensors Corporation) as feedback. The rate of pressure change is controlled by the velocity of the linear stage 2106. For acoustic frequency response testing, a speaker (not shown) is used to generate vibrations in the frequency range of 0-1 kHz.

[0167] For in vivo sensor characterization testing, the real resistance change was recorded using an LCR meter 2102, and the sensor was tested using its official evaluation module (equipped with a Wheatstone bridge and signal conditioning circuitry to output calibrated pressure readings).

[0168] To evaluate the stability of the superslippery surface (surface I), its stability was tested under cyclic liquid shear and long-term immersion in 1×PBS solution. After 10,000 immersions in phosphate buffer solution (1×PBS), the advancing angle and contact angle hysteresis remained almost unchanged, indicating good stability (see Figure 9 ). In addition, a glass slide coated with surface I (coated with 5 cSt silicone oil) was completely immersed in a 1× PBS solution for 5 days to monitor the changes in the surface wetting properties. The results showed that both the advancing angle and the contact angle hysteresis increased with increasing immersion time. However, it is worth noting that this increase is not excessive but within a reasonable range, as shown in Figure 2. Figure 22A and Figure 22B The advancing angle increased by only 1.20 ± 0.11°, and the contact angle hysteresis remained within 4°. The slight decrease in slip performance can be attributed to the loss of oil due to its slow diffusion into the PBS solution during the long immersion period (5 days).

[0169] According to example embodiments, changes in contact angle over time may cause eAir performance drift. To evaluate the stability of the eAir sensor when immersed in water, the device was tested by immersing it in 1×PBS solution (pressure of 0kPa, 10kPa and 15kPa respectively). The device was monitored for 5 days to observe performance changes, especially in terms of linearity, hysteresis and sensitivity. The device was still functioning normally on the 5th day, but the performance degraded over time. Specifically, a decrease in linearity and an increase in hysteresis and sensitivity were observed. The degradation in device performance observed during the stability test was within expectations, as the performance of the ultra-slippery surface deteriorates over time and the air inside the device slowly dissolves into the water over time. As previously mentioned, the loss of oil from the ultra-slippery surface reduces its frictionless performance, resulting in a delay in the motion of the multiphase contact line. In addition, the loss of oil also reduces the thickness of the dielectric layer, resulting in an increase in capacitance.

[0170] Although performance degradation was observed, the performance changes within 48 hours were small and acceptable, with sensitivity changes of less than 10%, negligible linearity changes (R2 changes within 0.1%), and hysteresis remaining within 2.5%. After more than 48 hours, the performance changes continued to increase, but the device continued to operate normally without any performance failures. This indicates that there is still enough air in the device that is not completely dissolved. In theory, if the volume ratio between water and air is high, the water-air interface may be easily broken, resulting in a transition from the Cassie state to the Wenzel state. In the testing of the example embodiments described in this article, there are two scenarios:

[0171] 1. Performance testing is performed in an airtight chamber. First, the PBS solution is stored in an atmospheric environment (plenty of air) and has reached an air-saturated state at atmospheric pressure. During device testing, the device is placed in a large airtight chamber and covered / wrapped with a small drop of air-saturated PBS solution. There is plenty of air in the sealed chamber compared to the air inside the device. Since the PBS is already full of air, no more air will dissolve into the PBS solution without increasing the pressure. When the pressure increases, the contact area between the applied droplet and the large amount of air in the sealed chamber is larger than the smaller contact area between the air inside the device and the droplet, causing the droplet to be saturated with the air in the sealed chamber more quickly. Rapid saturation hinders any significant air dissolution inside the device.

[0172] 2. Devices using Ecoflex dome packages. In this case, because the PBS solution used is already saturated with air, the air inside the device does not dissolve further into the PBS solution at atmospheric pressure. However, when pressure increases, the small amount of PBS solution in the dome package is insufficient to significantly dissolve the trapped air inside the device.

[0173] Furthermore, reapplying oil to the structured surface of the device restored the sensing performance to its initial state, with a sensitivity change of less than 1%, negligible linearity change (R2 change within 0.1%), and hysteresis maintained within 2%. Therefore, the performance degradation of the eAir sensor according to the example embodiment can be fully recovered. Even for encapsulated devices, re-oiling is easy because the encapsulation film can be easily removed. Furthermore, this process is simple and does not require any specialized equipment, and can be performed by the user. Within the low-pressure test range, the stability of the sensor according to the example embodiment can be maintained for up to 5 days of continuous measurement. By re-oiling, the service life of the device can be extended. For the example applications of grasping forceps usage conditions and intracranial measurements, the current service life meets the necessary requirements, so the sensor according to the example embodiment is a viable and suitable choice.

[0174] To further enhance the stability of the device in the example embodiment, the viscosity of the silicone oil can be increased. While lower viscosity oils are beneficial for achieving lower friction and higher contact line fluidity, higher viscosity results in lower oil loss rates and higher stability, making it suitable for creating more stable super-slippery surfaces on the device. To evaluate the feasibility of this strategy, devices coated with silicone oils of different viscosities were tested under a maximum pressure of 15 kPa. Specifically, we monitored the sensing performance of devices coated with 350 cSt and 5 cSt silicone oils over time. The device was immersed in a 1× PBS solution and a constant pressure of 15 kPa was applied. As Figure 22A and Figure 22B As shown in Figure 2, 350 cSt silicone oil resulted in less change in surface properties, especially contact angle hysteresis. Figure 23A -C shows that compared with 5cSt silicone oil, the improvement of surface stability makes its linearity, hysteresis and sensitivity change smaller. Therefore, due to the lower oil loss rate of high viscosity silicone oil, the performance is more stable (comparison Figure 23D and Figure 23E ). Therefore, according to example embodiments, increasing oil viscosity is an effective method to enhance device stability. Figure 23F This figure shows the effect of coating oil viscosity on the eAir hysteresis performance. The eAir sensors were coated with the same volume of oil (5 μL, 0.1% v / v silicone oil diluted in n-heptane) and tested at the same pressure. Data are presented as mean ± SD (3 samples), with corresponding data points overlaid.

[0175] An eAir sensor with 1 kcSt silicone oil according to an example embodiment was also tested and found to exhibit linear and low hysteresis performance at a low pressure change rate of 0.2 kPa / s. Figure 24 However, the sensing performance is greatly affected by different pressure change rates. The difference is that for the device coated with low viscosity silicone oil (5cSt), as shown in Figures 25A-25C As shown, the sensitivity is not affected by the pressure change rate, and the linearity and hysteresis decrease slightly with the increase of the pressure change rate. Overall, the sensor with coated surface I in Example 1 shows good performance consistency under different pressure change rates.

[0176] In the sensor performance recovery test, the silicone oil on the device was washed away with n-heptane, then reapplied with silicone oil and the device performance was tested. A circulating water bath (CORIO Cooling / Heating Circulator CD-200F) was used to control the liquid ambient temperature and test the effect of temperature on device performance.

[0177] Figure 16The capacitive response of an eAir sensor with a surface I-type structure at different temperatures, according to an exemplary embodiment, is shown. It maintains linearity and low hysteresis over a range of 5°C to 45°C. The eAir sensor was tested under cyclic pressure in 1×PBS. Regarding the effect of temperature, the eAir sensor's sensitivity increases with increasing temperature, while maintaining high linearity and low hysteresis across various ambient temperatures.

[0178] like Figure 26A As shown in Figure 3, the effect of frequency on the performance of the eAir sensor with surface I-type structure was studied by sweeping the test signal frequency from 20 Hz to 2 MHz without applying external pressure. Figure 26B Figure 2 shows the capacitive response of the eAir with surface I-type structure tested at different frequencies under applied cyclic pressure.

[0179] Figures 27A-27C This figure shows the effect of the volume of diluent oil applied on the sensing performance of the eAir sensor. Sensitivity, linearity, and hysteresis vary with the volume of diluent oil applied (0.1% v / v 5 cSt silicone oil diluted in n-heptane). All three performance parameters are optimized after applying 5 μL of diluent oil. Data are expressed as mean ± SD (5 samples).

[0180] According to example embodiments, sensors at negative and high pressures:

[0181] The air trapped in the eAir sensor will remain in the device even at negative pressures as low as -60kPa and will not fall off. Figure 28A As shown, when the submerged eAir device was subjected to various negative pressures, a noticeable bubble 2800 was observed protruding from the top of the eAir structure 2802 when the pressure dropped to -10 kPa. As the pressure was further reduced, the bubble size increased; however, even when the pressure reached -60 kPa (the lowest pressure the test apparatus could reach), the edge of the bubble 2804 remained pinned to the top edge of the structure 2806 wall. This negative pressure is significantly lower than the 0-15 kPa operating range of the eAir device described above.

[0182] Furthermore, the study found that even at pressures as low as -2 kPa, the eAir sensor maintains essentially the same sensitivity and linear response as in the 0-15 kPa range. Figure 28B This is because, at zero pressure, the dome-shaped pillars have already partially penetrated the water. Under slight negative pressure, the water-air interface moves outward but does not separate from the pillars until the pressure drops below -2 kPa. However, when the pressure reaches -4 kPa, the water at the center of the structure begins to fall away from the pillars, creating a bubble that "breaks away" from the internal structure, causing the device to no longer exhibit a linear response to pressure, as shown in Figure 2. Figure 28C shown.

[0183] According to an example embodiment, the eAir sensor can also respond to pressures exceeding the specified 15kPa. Figure 28D As shown, the eAir sensor can respond to pressures up to 50 kPa. It can actually respond to higher pressures, but due to the limited pressurization capacity of the test setup, only pressures up to 50 kPa can be measured. The eAir sensor exhibits low hysteresis in the 0-50 kPa range and maintains a linear relationship between capacitance and pressure from 0-15 kPa. However, as pressure continues to increase, sensitivity gradually decreases, exhibiting nonlinearity. This is because air becomes increasingly difficult to compress as pressure increases. The same pressure change results in a smaller change in air volume, and the change in the water-electrode contact area also decreases with increasing pressure.

[0184] Definitions of hysteresis, linearity, and sensitivity:

[0185] Hysteresis (H) is defined here as the maximum absolute difference between the loading curve and the unloading curve at the same pressure as a percentage of the full range span (YFS).

[0186] Linearity is quantified in two ways. One is to use a simple linear regression model (calculated by OriginPro software) to perform a linear fit on the loading and unloading conditions and calculate its coefficient of determination (R square). The other is to calculate the nonlinearity of the device performance curve. Here, the nonlinearity (L non. ) is expressed as the percentage of the maximum absolute value of the linear fitting line to the full scale (YFS) of the difference between the absolute values ​​of the loading curve and the unloading curve at the same pressure.

[0187] Sensitivity is defined as the change in output value per unit change in pressure. An ideal high-precision pressure sensor should exhibit linearity, zero threshold, no hysteresis, and a sensitive response. Specifically, poor hysteresis and linearity can lead to sensing errors and signal distortion. Furthermore, such sensors have limited sensitivity consistency across their operating range, necessitating additional pressure output calibration.

[0188] Capacitance Analysis of Sensors According to Example Embodiments

[0189] Figure 2C The capacitance (C) component of a sensor and its equivalent circuit according to an example embodiment are shown, along with surface coating details between the structure's working electrode and the liquid.

[0190] The device capacitance can be expressed as:

[0191]

[0192] Where C0 is the interfacial capacitance of the inactive area, which is located outside the chamber, that is, the top area of ​​the structured working electrode in contact with the liquid and the wires encapsulated with the insulating layer (SU-8 and polyimide). The active area is defined as the inner surface area of ​​the chamber, that is, the area where dynamic wetting occurs. Since the capacitance of each component follows the physical principle of a parallel plate capacitor, its value can be calculated using εA / d, where ε is the dielectric constant of the dielectric material, A is the plate area, and d is the equivalent distance between the two plates. The C between the non-contact area of ​​the structured electrode and the liquid-air interface is through the surface coating and air. d+air It can be ignored because its equivalent d is much larger than other capacitors. C d.ct and C EDL.ct Can be regarded as the interface capacitance C ct , that is, the interfacial capacitance between the structured electrode and the liquid within the liquid-electrode contact area.

[0193] Therefore, Equation 1 can be simplified to:

[0194]

[0195] For surface I, the dielectric layer consists of ODTSAM and silicone oil, as the polyaniline nanowires and the gold coated on the nanowires are conductive. The ODTSAM is a few nanometers thick (thickness ≈ 2 nm, dielectric constant: approximately 2.1), and the silicone oil is infused between the nanostructures induced by the polyaniline nanowires. Therefore, the dielectric layer is very thin. The unit capacitance of the electrode treated with surface I was measured to be 1.87 ± 0.30 nF / mm. 2 .

[0196] For Surface II, the dielectric layer is ODTSAM. The unit capacitance of the surface treated with Surface II was measured to be 6.79 ± 0.64 nF / mm 2 .

[0197] For surfaces III and IV, since polyaniline nanowires are conductive, the dielectric layer is the air between the surface nanostructures induced by ODTSAM and polyaniline nanowires (coated with gold). The unit capacitance of the surface III and surface IV treated electrodes was measured to be 7.05±0.16nF / mm, respectively. 2 and 7.98±0.54nF / mm 2 .

[0198] The unit capacitance of the bare gold electrode was measured to be 97.3±10.1nF / mm 2 The unit capacitance is measured by placing two electrodes of the same area (1cm 2) were immersed in a 1× PBS solution, spaced 1 cm apart, and a 100 mVrms, 100 kHz voltage was applied. It is important to note that the measured capacitance decreases with increasing distance between the electrodes in the solution. In actual device structures, the distance between the electrodes and the counter electrode is much less than 1 cm, so the unit capacitance obtained here is smaller than the unit capacitance within the eAir device.

[0199] In addition, among all devices with different surfaces, the liquid-electrode contact area on the structured working electrode is much smaller than that on the counter electrode (3.2 mm 2 ), which has been confirmed by simulation results. In addition, the capacitance of the inactive area can be divided into two parts: i) the exposed area on the top of the working electrode and the electrode area on the wall for leading out the unpackaged wire. This part is less than 0.6mm 2 , and varies with the manual encapsulation of SU-8. This area has the same surface treatment as the device, so when considering these two areas, the capacitance C0 is the same as C ct are of the same order of magnitude; ii) the area of ​​the wire encapsulated by the insulating layer (SU-8 and polyimide). Since the insulating layer is very thick compared to the surface treatment, this part of the capacitance can be ignored. Therefore, all devices with different surface finishes follow the same capacitance relationship: C counter >>C ct +C0.

[0200] Therefore, C counter >>(C ct +C0) / C counter is much smaller than 1, and Formula 2 can be further understood as,

[0201] C≈C ct +C0 (Formula 3).

[0202] C ct It can be calculated as:

[0203] C ct =ε ct A ct / d ct , ε ct (Formula 4)

[0204] Among them, ε ct and d ct are the equivalent dielectric constant and electrode distance between the structure electrode and liquid coating interface, A ct is the change in contact area between the liquid and the treated structure working electrode caused by the liquid pressure. Since the dielectric constant and distance are constant for a fixed surface treatment, a constant k = ε can be defined. ct / d ctTherefore, for all devices with different surfaces, the following formula applies:

[0205] C≈C0+kA ct (Formula 5)

[0206] Therefore, it can be considered that the capacitance of the eAir device is linearly proportional to its liquid electrode contact area within the designed structure according to example embodiments.

[0207] In one embodiment, a pressure sensor structure is provided, comprising: a chamber having a closed bottom and an open top; an array of working electrode surfaces disposed within the chamber and extending from the bottom of the chamber to the open top; and a counter electrode formed outside the chamber; wherein the chamber in which the working electrode surfaces are disposed is configured to capture air when the chamber is immersed in a liquid; wherein the working electrode surfaces are electrically contactable from outside the chamber; and, when air is captured in the chamber, a change in capacitance between the working electrode and the counter electrode is a measure of a change in pressure of the liquid in which the chamber is immersed.

[0208] The working electrode surfaces may all be formed on the inner wall of the chamber.

[0209] The working electrode surfaces may be formed on pillars formed at the bottom of the chamber. The pillars may comprise a sharp tip portion, such as a dome-shaped or conical top, preferably with a gradual tangential transition between the bottom of the sharp tip portion and the main body of the pillar.

[0210] The working electrode surface can be modified to provide a hydrophobic interface with the liquid. The working electrode surface can be modified to provide an advancing contact angle of the liquid under increasing liquid pressure that is greater than the static contact angle of water on the hydrophobic surface and is less than 160°, preferably less than 135°, more preferably less than 115°, and even more preferably less than 112°.

[0211] The working electrode surface can be modified to provide an advancing contact angle for the liquid under increasing liquid pressure and a receding contact angle for the liquid under decreasing liquid pressure, the contact angle hysteresis being less than 10°, preferably less than 5°, and more preferably less than 3°.

[0212] The capacitance between the working electrode surface and the counter electrode may include a double layer at the interface between the working electrode surface and the liquid and at the liquid and the counter electrode surface.

[0213] The pressure sensor structure may include a packaging structure for encapsulating a chamber and a counter electrode, the chamber being immersed in a liquid and air being trapped in the chamber, such that a change in capacitance between the working electrode and the counter electrode can be used as a measure of a pressure change on the packaging structure.

[0214] The chamber and the counter electrode may be formed on a rigid substrate.

[0215] The chamber and the counter electrode may be formed on a flexible substrate.

[0216] Figure 29 A flowchart 2900 is shown illustrating a method for fabricating a pressure sensor structure according to an exemplary embodiment. In step 2902, a chamber having a closed bottom and an open top is provided. In step 2904, an array of working electrode surfaces is disposed within the chamber, the array extending from the bottom of the chamber to the open top. In step 2906, a counter electrode is formed outside the chamber. In step 2908, the chamber having the working electrode surfaces is configured to trap air when immersed in a liquid, wherein the working electrode surfaces are electrically contactable from outside the chamber, and when air is trapped in the chamber, a change in capacitance between the working electrode and the counter electrode is a measure of a change in pressure of the liquid in which the chamber is immersed.

[0217] The method may include forming a working electrode surface on an interior wall of the chamber.

[0218] The method may include forming a working electrode on a pillar formed in the bottom of the chamber. The method may include providing the pillar with a pointed portion, such as a domed or conical top, preferably with a gradual tangential transition between the bottom of the pointed portion and the body of the pillar.

[0219] The method may include modifying the working electrode surface to provide a hydrophobic interface with the liquid. The method may include modifying the working electrode surface to provide an advancing contact angle of the liquid under increasing pressure on the liquid that is greater than the static contact angle of water on the hydrophobic surface and is less than 160°, preferably less than 135°, more preferably less than 115°, and more preferably less than 112°.

[0220] The method may comprise modifying the working electrode surface to provide a contact angle hysteresis of less than 10°, preferably less than 5°, more preferably less than 3°.

[0221] The capacitance between the working electrode surface and the counter electrode may include an electrical double layer at the interface between the working electrode surface and the liquid and at the liquid and the counter electrode surface.

[0222] The method may include packaging a chamber and a counter electrode together, wherein the chamber is immersed in a liquid and air is encapsulated in the chamber within the packaging structure, such that a change in capacitance between the working electrode and the counter electrode can be used as a measure of a change in pressure on the packaging structure.

[0223] The method may include forming a chamber and a counter electrode on a rigid substrate.

[0224] The method may include forming a chamber and a counter electrode on a flexible substrate.

[0225] In one embodiment, a method of measuring pressure using the pressure sensor structure of any embodiment is provided, the method comprising monitoring a change in capacitance between a working electrode and a counter electrode as a measure of a change in pressure of a liquid immersed in a chamber.

[0226] The packaging structure may enclose a chamber and a counter electrode, the chamber being immersed in the liquid and containing air, and the method may include monitoring a change in capacitance between the working electrode and the counter electrode as a measure of a change in pressure on the packaging structure.

[0227] In one embodiment, a device is provided that includes the pressure sensor structure of any embodiment.

[0228] The device may include a surgical grasping forceps having one or more receivers formed on one of its jaws, wherein the receivers maintain closed fluid communication with one or more pressure sensor structures such that a change in capacitance between a working electrode and a counter electrode of the one or more pressure sensor structures can be used as a measure of a change in pressure on the one or more receivers.

[0229] The device may include a wireless module for transmitting data representing changes in capacitance between the working electrode and the counter electrode.

[0230] Embodiments of the present invention may have one or more of the following features and associated advantages / benefits:

[0231]

[0232] Industrial Applications of Example Embodiments:

[0233] Traditional pressure sensors made only of solid-state materials have difficulty in achieving high sensitivity, hysteresis and linearity at the same time in a liquid environment, and face a three-pronged dilemma. The embodiments of the present invention solve this problem by utilizing aeroelasticity, sophisticated structural design, multi-scale ultra-slippery surfaces, and the double layer effect at the electrode-liquid interface. The sensor according to the preferred embodiment can achieve the best pressure sensing performance to date, that is, as far as the inventors know, the highest linearity (R square = 0.99944 ± 0.00015, nonlinearity = (1.49 ± 0.17)%). The sensor exhibits ultra-low hysteresis ((1.34 ± 0.20)%) and high sensitivity (79.1 ± 4.3 pF / kPa) in a liquid environment. The sensor can work in complex liquid environments such as turbulence and in vivo, and can also sense acoustic vibrations.

[0234] Various aspects of the systems and methods described herein, such as the generation of sensor outputs, can be implemented on computing devices, including cloud-based computing devices and / or IoT computing devices, for example, as functions programmed into various circuits, including programmable logic devices (PLDs), such as field programmable gate arrays (FPGAs), programmable array logic (PAL) devices, electrically programmable logic and memory devices, and standard cell-based devices, as well as application-specific integrated circuits (ASICs). Other possibilities for implementing various aspects of the system include: microcontrollers with memory (e.g., electrically erasable programmable read-only memory (EEPROM)), embedded microprocessors, firmware, software, and the like. Furthermore, various aspects of the system can be embodied in microprocessors with software-based circuit simulation, discrete logic (sequential and combinational), custom devices, fuzzy (neural) logic, quantum devices, and hybrids of any of the aforementioned device types. Of course, the underlying device technology can employ a variety of component types, such as metal oxide semiconductor field effect transistor (MOSFET) technology (e.g., complementary metal oxide semiconductor (CMOS)), bipolar technology (e.g., emitter coupled logic (ECL)), polymer technology (e.g., silicon conjugated polymer and metal conjugated polymer-metal structures), mixed analog and digital technology, and the like. The various functions or processes disclosed herein, in terms of their behavior, register transfers, logic components, transistors, layout geometries, and / or other characteristics, can be described as data and / or instructions embodied in various computer-readable media. Computer-readable media that can embody such formatted data and / or instructions include, but are not limited to, various forms of non-volatile storage media (e.g., optical, magnetic, or semiconductor storage media) and carrier waves that can be used to transmit such formatted data and / or instructions via wireless, optical, or wired signal media, or any combination thereof. When such data and / or instructions are received into various circuits (e.g., computers), they can be processed by a processing entity (e.g., one or more processors).

[0235] It will be understood by those skilled in the art that various variations and / or modifications may be made to the invention shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. Therefore, the present embodiments are to be considered in all respects as illustrative and not restrictive. Furthermore, the present invention encompasses any combination of features described for the various embodiments (including in the Abstract), even if such feature or combination of features is not expressly specified in the claims or detailed description of the embodiments of the invention.

[0236] In general, in the following claims, the terms used should not be construed to limit the systems and methods to the specific embodiments disclosed in the specification and claims, but should be construed to encompass all processing systems that operate within the scope of the claims. Accordingly, the systems and methods are not limited by the present disclosure, but rather the scope of the systems and methods is to be determined entirely by the claims.

[0237] Throughout the specification and claims, unless the context clearly requires otherwise, the words “include,” “comprising,” and similar expressions should be construed in an inclusive sense, and not in an exclusive or exhaustive sense; that is, to mean “including, but not limited to.” Words using the singular or plural number also include the plural or singular number, respectively. In addition, the words “herein,” “under,” “above,” “below,” and words of similar import refer to the entire application and not to any particular part of the application. When the word “or” is used in reference to a list of two or more items, the word encompasses all of the following interpretations: any item in the list, all of the items in the list, and any combination of the items in the list.

[0238] References

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Claims

1. A pressure sensor structure, comprising: a chamber having a closed bottom and an open top; an array of working electrode surfaces disposed within the chamber and extending from the bottom to the open top of the chamber; and a counter electrode formed outside the chamber; wherein the chamber in which the working electrode surface is disposed is configured to capture air when the chamber is immersed in a liquid; wherein the working electrode surface is electrically accessible from outside the chamber; and Wherein, when the air is trapped in the chamber, the change in capacitance between the working electrode and the counter electrode is a measure of the change in pressure of the liquid in which the chamber is immersed.

2. The pressure sensor structure according to claim 1, wherein: The working electrode surfaces are all formed on the inner wall of the chamber.

3. The pressure sensor structure according to claim 1 or 2, wherein: The surfaces of the working electrodes are all formed on the columns formed at the bottom of the chamber.

4. The pressure sensor structure according to claim 3, wherein: The pillar comprises a sharp tip portion, such as a dome-shaped or conical top, and preferably, the base of the sharp tip portion has a gradual tangential transition to the main body of the pillar.

5. The pressure sensor structure according to claim 1, wherein: The surfaces of the working electrodes are modified to provide a hydrophobic interface with the liquid.

6. The pressure sensor structure according to claim 5, wherein: The surfaces of the working electrodes are modified to provide an advancing contact angle of the liquid as the pressure on the liquid increases, the advancing contact angle being greater than the static contact angle of water on the hydrophobic surface and being less than 160°, preferably less than 135°, more preferably less than 115°, and more preferably less than 112°.

7. The pressure sensor structure according to claim 5 or 6, wherein: The surfaces of the working electrodes are modified so that the contact angle hysteresis between the advancing contact angle of the liquid when the pressure on the liquid increases and the receding contact angle of the liquid when the pressure on the liquid decreases is less than 10°, preferably less than 5°, and more preferably less than 3°.

8. A pressure sensor structure according to any one of the preceding claims, wherein: The capacitance between the working electrode surface and the counter electrode includes a double electrical layer at the interface between the working electrode surface and the liquid and at the liquid and the counter electrode surface.

9. The pressure sensor structure according to any one of the preceding claims comprises a packaging structure for encapsulating the chamber and the counter electrode, the chamber being immersed in the liquid and having air trapped in the chamber, so that the capacitance change between the working electrode and the counter electrode can be used as a measure of the pressure change on the packaging structure.

10. A pressure sensor structure according to any one of the preceding claims, wherein: The chamber and the counter electrode are formed on a rigid substrate.

11. The pressure sensor structure according to any one of claims 1 to 9, wherein: The chamber and the counter electrode are formed on a flexible substrate.

12. A method for manufacturing a pressure sensor structure, comprising the following steps: providing a chamber having a closed bottom and an open top; an array of working electrode surfaces disposed within the chamber and extending from the bottom of the chamber to the open top; forming a counter electrode outside the chamber; as well as configuring the chamber within which the working electrode surface is disposed to capture air when the chamber is immersed in a liquid; wherein the working electrode surface is electrically accessible from outside the chamber; and Wherein, when the air is trapped in the chamber, the change in capacitance between the working electrode and the counter electrode is a measure of the change in pressure of the liquid in which the chamber is immersed.

13. The method of claim 12, comprising forming the working electrode surface on an inner wall of a chamber.

14. The method of claim 12 or 13, comprising forming the working electrode on a pillar formed on the bottom of the chamber.

15. A method according to claim 14, comprising providing the pillar with a sharp tip portion, such as a domed or conical top, preferably with a gradual tangential transition between the base of the sharp tip portion and the body of the pillar.

16. A method according to any one of claims 12 to 15 comprising modifying the working electrode surface to provide a hydrophobic interface with the liquid.

17. The method according to claim 16 comprises modifying the surface of the working electrode so that when the pressure on the liquid increases, the advancing contact angle of the liquid is greater than the static contact angle of water on the hydrophobic surface and is less than 160°, preferably less than 135°, more preferably less than 115°, and more preferably less than 112°.

18. The method according to claim 16 or 17 comprises modifying the surface of the working electrode so that the contact angle hysteresis between the advancing contact angle of the liquid when the pressure on the liquid increases and the receding contact angle of the liquid when the pressure on the liquid decreases is less than 10°, preferably less than 5°, and more preferably less than 3°.

19. The method according to any one of claims 12 to 18, wherein The capacitance between the working electrode surface and the counter electrode includes a double electrical layer at the interface between the working electrode surface and the liquid and at the liquid and the counter electrode surface.

20. The method according to any one of claims 12 to 19, comprising packaging the chamber and the counter electrode together, immersing the chamber in the liquid, and trapping air in the chamber in the packaging structure, so that the change in the capacitance between the working electrode and the counter electrode can be used as a measure of the pressure change on the packaging structure.

21. A method according to any one of claims 12 to 20, comprising forming the chamber and the counter electrode on a rigid substrate.

22. The method of any one of claims 12 to 20, comprising forming the chamber and the counter electrode on a flexible substrate.

23. A method of measuring pressure using the pressure sensor structure according to any one of claims 1 to 11, comprising the step of monitoring changes in the capacitance between the working electrode and the counter electrode as a measure of pressure changes in the liquid in which the chamber is immersed.

24. The method according to claim 23, wherein The packaging structure encapsulates the chamber and the counter electrode, the chamber is immersed in the liquid, and air is trapped in the chamber. The method includes monitoring the change in capacitance between the working electrode and the counter electrode as a measure of the pressure change on the packaging structure.

25. A device comprising the pressure sensor structure according to any one of claims 1 to 11.

26. The device according to claim 25, wherein The device includes a surgical grasping forceps having one or more receivers formed on one of its claws, wherein the multiple receivers maintain closed fluid communication with one or more of the pressure sensor structures, so that a change in capacitance between the working electrode and the counter electrode in the one or more pressure sensor structures can be used as a measure of a pressure change on the one or more receivers.

27. The apparatus of claim 25 or 26, comprising a wireless module for transmitting data representing changes in the capacitance between the working electrode and the counter electrode.

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