Carbon nanotube-enhanced piezoresistive sensor

Abstract

The invention relates to the fabrication of carbon nanotube (CNT)-reinforced polymer-based composite filaments by solvent dispersion and the production method of a volumetric conductive piezoresistive sensor with a Gyroid Triple Periodic Minimum Surface (TPMS) geometry using Melt Deposition Modeling (FDM) with these filaments. Figure 1

Description

1 TARIFF Carbon nanotube-enhanced piezoresistive sensor TECHNICAL AREA 5 The invention relates to materials, additive manufacturing, structural health monitoring, aviation, and more in general. It relates to self-sensing pressure-strain sensors in the automotive industry. The invention specifically concerns 10 carbon nanotube (CNT) doped products produced by solvent dispersion method. Production of polymer-based composite filaments and melt processing using these filaments. Gyroid Triple Periodic Minimum Surface Area using Stacked Modeling (SPM) Method Volumetric conductive piezoresistive sensor with (TPMS) geometry and manufacturing method. It is related to. STATE OF THE ART Piezoresistive sensors detect mechanical force, pressure, or strain applied to them. by measuring the change in electrical resistance that occurs as a result. These are the elements that make up structural health monitoring, wearable electronics, and the automotive industry. The use of self-sensing systems in components is increasing every day. It is becoming widespread. Today, conductive filaments are made with carbon nanotube (CNT) reinforced polymers. They are produced. 3D printers can print using conductive filaments. 25 and by producing various TPMS (Triply Periodic Minimal Surface) / Lattice structures It is used as a sensor. TPMS stands for "Triple Periodic Minimum Surface". It is known that the mean curvature is zero and it is regular in three spatial dimensions (x, y, z). These are mathematical surfaces that repeat. A lattice structure, on the other hand, has an interior that is completely filled with... They are structures composed of non-filling, porous, and repeating cell networks. TPMS 30 Lattice structures with a base offer very high mechanical resistance and impact resistance relative to their weight. It offers damping capacity. Piezoresistive sensors are basically... They are produced using conventional methods or additive manufacturing methods. In the conventional method of production, a conductive material is placed inside an insulating polymer matrix. 2 placement of materials (Copper-Cu, Silver-Ag, CNT, etc.) or layered structures It is based on the principle of creation. However, produced by conventional methods Manufacturing piezoresistive sensors in complex or specific geometric shapes is quite challenging. This takes a long time and results in high production costs. Furthermore, this... In these methods, a homogeneous volumetric electrical conductivity is obtained within the conductive packing matrix. 5 It is quite difficult to achieve this. In additive manufacturing methods based on coating or painting, Insulating and non-conductive TPMS or mesh structures produced with 3D printers. surfaces; conductive nanoreinforcements such as CNT, carbon black (CB), graphene or graphite spray coating or dip coating with solutions containing It is coated in the following way. 10 These current practices in technology bring with them significant technical shortcomings and This brings about problems: - Conductive lattice structures based on surface coating or painting, It is subjected to friction under mechanical load and repeated deformation. 15 Over time, the conductive layer on the surface wears away or flakes off. This This situation leads to deterioration of the conductive network and a loss of accuracy in the sensor over time. This causes it to suffer or become completely incapacitated. - Carbon-based conductive nano-reinforcements in polymer matrices (ABS, PLA) It is a process that is difficult to achieve homogeneous distribution (dispersion) within it. Insufficient 20 Agglomeration in the composite structure due to dispersion and discontinuities in electrical conductivity occur along the filament. It is coming. - To achieve high electrical conductivity, excess material is added to the polymer matrix. Adding a certain amount of nano-additives improves the mechanical and fluid properties of the matrix by 25%. It has a negative impact. - Conventional lattice / frame geometries exhibit axial resistance under mechanical load. It can exhibit unstable deformation, and this situation affects resistance changes. leading to nonlinear, unstable and noisy electrical feedback. It opens. 30 Document KR102784869B1, encountered under the known state of the art, is a 3D document. This document relates to wearable devices based on printed metadata structure. It discusses FDM (Fully Depressant Medium). a printed elastic gyroid meta-structure is first inflated in an organic solvent, 3 then dispersed into conductive fibers (e.g., carbon nanofibers, metal microfibers, etc.). obtained by immersion and drying, with a surface coated with a conductive layer. A 3D-printed structure is described. In this structure, conductivity is only... Since it is achieved by surface coating obtained through the dipping method, repeated Coating layer 5 is affected by external factors such as mechanical loading, friction, abrasion and moisture. It can delaminate and lose conductivity / sensor function. During the production phase, first the insulating structure is printed, then it is soaked in a chemical solvent. Because it requires a two-stage production process, namely inflation and dipping, the production the duration is increasing, intra-batch repeatability is decreasing, and complex internal components such as gyroids are becoming more difficult to process. Homogeneous coating cannot be obtained in these geometries. Furthermore, signal stability is 10 High resistance to repeated loading due to its dependence on coating integrity. It carries the risk of deviation. Document number US2025332541A1 specifies the triple periodic minimal for carbon capture. This document relates to surface-absorbing contactors. It describes the use of 3D 15 for carbon capture purposes. Polymer ink and sorbent (zeolite, MOF, amine, etc.) filler in a printed PVA plate. injection followed by non-solvent induced templated phase inversion Simultaneously with Templed Phase Inversion (TPI), the PVA template dissolves and Internally microporous TPMS sorbent contactor via polymer solidification. It describes its production. The configuration mentioned in this document is not a sensor, but gas 20 It is a contactor intended for separation / carbon capture; electrical conductivity, It does not have pressure / strain sensing or piezoresistive mechanical measurement capabilities. In this production method, the final part cannot be directly printed with FDM; it uses PVA molding. complex processes such as printing, ink injection and stencil phase inversion (TPI) It involves indirect steps. 25 As a result, improvements are being made in piezoresistive sensor manufacturing methods. Therefore, it will eliminate the disadvantages mentioned above and the existing New structures are needed to provide solutions to these systems. 4 THE PURPOSE OF THE INVENTION The present invention meets the aforementioned requirements and overcomes all the disadvantages. a piezoresistive sensor manufacturing method that eliminates the need for a separate process and offers some additional advantages It is related to 5. The main purpose of the invention is to achieve homogeneous distribution by solvent-based ultrasonic dispersion method. Development of CNT-reinforced ABS / PLA-based composite filaments and this The filaments are processed using FDM additive manufacturing method to form a Gyroid TPMS geometry. The goal is to produce volumetric conductive piezoresistive sensors. 10 One aim of the invention is to integrate CNT nano-reinforcements into a polymer matrix (ABS or PLA) structure. surface coating or by volumetric homogeneous integration. The aim is to eliminate the need for painting. Thus, mechanical wear is reduced. and the aim is to completely prevent shedding problems due to friction. 15 Another purpose of the invention is ultrasonic homogenization applied in solvent media. Thanks to the method and the use of a dispersion agent, with low-rate CNT supplementation achieving a low percolation threshold; processability and mechanical properties of the polymer The aim is to ensure volumetric electrical conductivity is achieved while maintaining the required level. 20 Another aim of the invention is to create a gyroid with a continuous, uninterrupted, and smooth surface area. Force and electrical conductivity under mechanical load applied with TPMS geometry. The aim is to ensure a homogeneous distribution of the network. This allows for a reduction in electrical resistance variation. The aim is to achieve a more stable, repeatable, and linear graph tracing. 25 Another purpose of the invention is to enable additive manufacturing (FDM) integration. By customizing the sensors to the desired geometric dimensions and shapes, fast and low-cost solutions are possible. The goal is to ensure that it is produced at a cost. All the advantages mentioned above and explained in detail below. The present invention aims to realize self-sensing and self-aware technologies in various sectors. Used for structural monitoring as a pressure-strain sensor, it consists of an upper electrode and a lower electrode. It is a piezoresistive sensor containing a gyroid matrix located between the electrodes; solvent-based. Produced by ultrasonic dispersion method and homogenized within the polymer matrix carbon nanotube reinforced composite with volumetric conductivity Gyroid obtained by processing the filament using additive manufacturing method. A matrix-based structure has been obtained. The structural and characteristic features and all the advantages of the invention are given in the figures below. And thanks to the detailed explanation written with references to these figures, it becomes clearer. This will be understood as such. Therefore, the evaluation should also be based on these forms and details. This should be done taking the explanation into consideration. BRIEF DESCRIPTION OF THE FIGURES The best way to utilize the advantages of the existing invention, together with its structure and additional elements. For understanding, it should be evaluated together with the figures explained below. is necessary. Figure 1 shows a representative view of the piezoresistive sensor that is the subject of the invention. 15 REFERENCE NUMBERS 1. Upper electrode 2. Lower electrode 3. Gyroid matrix 20 DETAILED EXPLANATION OF THE INVENTION This detailed explanation describes the preferred method for manufacturing the piezoresistive sensor that is the subject of the invention. the structures that were created were solely for the purpose of better understanding the subject and 25 It is explained in a way that will not create any limiting effects. The invention is suitable for use as a self-sensing and pressure-strain sensor in various sectors. Used for structural monitoring, between an upper electrode (1) and a lower electrode (2). It is a piezoresistive sensor containing a Gyroid matrix (3); solvent-based ultrasonic 30 produced by the dispersion method and homogeneously within the polymer matrix a carbon nanotube reinforced composite filament with volumetric conductivity, 6 Gyroid matrix (3) obtained by processing with additive manufacturing method It includes. Figure 1 shows a representative view of the piezoresistive sensor that is the subject of the invention. The piezoresistive sensor in question generally consists of an upper electrode (1) and a lower electrode 5 It consists of a Gyroid matrix (3) located between (2). The mentioned Gyroid matrix (3) is produced by solvent ultrasonic dispersion method and polymer Carbon nanotubes with homogeneous volumetric conductivity within the matrix obtained by processing reinforced composite filament using additive manufacturing method. It has been done. 10 Composite with volumetric conductivity during the production of the gyroid matrix (3) Filament production begins with the removal of moisture from the material. This In this context, ABS or PLA polymers, selected as the matrix material, are placed in a vacuum. While being dried in an oven at 85 °C for 12 hours, the conductive nano-reinforcement material 15 The carbon nanotube, which is also present, was placed in a vacuum oven at 85 °C for 1 hour. They are subjected to a drying process. The dried carbon nanotubes have a structure. To prevent agglomeration, carbon nanotubes are used in a suitable environment. It is added to the solvent (acetone or dichloromethane) and the dispersing agent to the mixture. Polyethylene glycol (PEG) is added. This resulting mixture is then ultrasonically 20 The carbon nanotubes are completely dispersed in the solvent by processing in a homogenizer. Simultaneously dried polymers are also suitable. They are dissolved in solvents; at this stage, acetone is used for ABS polymer and for PLA polymer. Dichloromethane (DCM) solvent is preferred. The polymer solution is in a dissolved state. by combining ultrasonically dispersed carbon nanotube dispersion with 25 They are mixed again in an ultrasonic homogenizer. This process involves the carbon nanotubes. the molecular-level and homogeneous impregnation of the polymer matrix It provides. After the mixing process, solvent melting and homogenization. in order to completely remove the moisture and solvent that enters the structure during the stages The resulting homogenized structure was placed in a vacuum oven at 55 °C for 6 hours. They are dried. The conductive composite films obtained as a result of drying, The material is ground into granules to achieve a particle size suitable for the extrusion process. It is transformed into a conductive form. The resulting conductive granules are fed into an extruder device. 1.75 mm suitable for printing via Fused Deposition Modeling (FDM) by feeding. 7 They are drawn into volumetric conductive filaments of a certain diameter. This special method is applied. Thanks to the preparation process, it contains an extremely low percentage of only 3% by weight. The percolation threshold is reached in terms of carbon nanotube ratio, and the processability of the polymer is improved. This allows for the creation of a continuous volumetric conductive network while maintaining mechanical strength. The 1.75 mm diameter conductive composite filament produced can be fed into a 3D printer in 5 steps. Gyroid is fed and processed at appropriate temperatures using FDM additive manufacturing technique. Gyroid matrix with periodic minimal surface (TPMS) in three axes having geometry (3) It is printed in this form. The top electrode (1) and the bottom surfaces of this printed matrix are printed. The final piezoresistive sensor structure is obtained by placing the lower electrode (2). The upper electrode (1) and lower electrode (2) mentioned herein are made of copper or silver material. It is possible. The operating principle of the piezoresistive sensor, which is the subject of this invention, is that it is conductive under mechanical load. the detection of changes occurring in the network as an electrical resistance difference It is based on. During the study, an external 15 is connected to the upper electrode (1) and the lower electrode (2). A constant and low-level DC (Direct Current) voltage is applied from the source. When any axial force, pressure, or strain is applied to the sensor, The Gyroid matrix (3), which has a flexible structure, undergoes mechanical deformation. As a result of deformation, the Gyroid matrix (3) is homogeneously distributed within it. The contact points of carbon nanotubes with each other, the tunneling distances between them are 20 and consequently, the contact resistances change. Gyroid TPMS geometry, Because it has a smooth and uninterrupted large surface area, it is applied The mechanical load is distributed homogeneously throughout the matrix (3). This homogeneous load Thanks to its distribution, the change in electrical resistance is stable, noiseless and extremely precise. It exhibits a linear characteristic. The resulting resistance change was measured and 25 The amount of load, pressure, or strain on the sensor is measured precisely and reliably. It is being detected. In addition, carbon nanotubes are directly embedded in the polymer volume. Because of this condition, the surface remains stable even under repeated mechanical deformations. technical issues such as wear, peeling, or conductive shedding observed in coatings Deficiencies are completely prevented. 30

Claims

8 REQUESTS 1. Self-sensing and pressure-strain sensors in various sectors. Used for structural monitoring, between an upper electrode (1) and a lower electrode (2). It is a piezoresistive sensor containing a Gyroid matrix (3), and its feature is solvent-based 5 Produced by ultrasonic dispersion method and homogenized within the polymer matrix carbon nanotube reinforced composite with volumetric conductivity obtained by processing the filament using the additive manufacturing method It contains a gyroid matrix (3).

2. It is a piezoresistive sensor that conforms to Claim 1, and its feature is that it is a Gyroid matrix (3) It contains 3% carbon nanotubes by weight.

3. It is a piezoresistive sensor that conforms to claim 1 and has the characteristic of being the aforementioned Gyroid matrix (3) ABS or PLA-based composite filament as polymer raw material 15 It includes.

4. Self-sensing and pressure-strain sensors in various sectors. Used for structural monitoring, between an upper electrode (1) and a lower electrode (2). This is a piezoresistive sensor manufacturing method containing a Gyroid matrix (3), 20 feature; • Matrix raw material polymers and carbon nanotubes in a vacuum oven drying, • carbon nanotubes dispersed in a suitable solvent with the addition of a dispersion agent Mixing in an ultrasonic homogenizer, 25 • Dissolving matrix raw material polymers in a suitable solvent, • ultrasonic dissolution of polymers and carbon nanotubes mixing in a homogenizer, • polymer and carbon nanotube mixture dried in a vacuum oven removal of moisture, 30 • Grinding the obtained conductive composite structure into granules, • Production of conductive composite filament by processing granules in an extruder, • Gyroid in a 3D printer using conductive composite filament produced. Printing of the matrix (3), 9 • The upper electrode (1) is applied to the upper and lower surfaces of the printed Gyroid matrix (3) respectively. and placement of the lower electrode (2) It includes the steps of the process.

5. This is a piezoresistive sensor manufacturing method that complies with Claim 4, and its characteristic is; raw matrix 5 The material polymer used is either ABS or PLA polymer.

6. A piezoresistive sensor manufacturing method conforming to Claim 4, characterized by its carbon fiber structure. Acetone or acetone can be used as a solvent in the process step of mixing nanotubes. Dichloromethane is used with polyethylene glycol (PEG) as a dispersion agent. 10 7. This is a piezoresistive sensor manufacturing method that complies with Claim 4, and its characteristic feature is; raw matrix. in the process step of dissolving the polymeric substances in a suitable solvent Acetone is used as a solvent for ABS polymer, and dichloromethane (DCM) is used as a solvent for PLA polymer. It is the use of. 15 8. A piezoresistive sensor manufacturing method conforming to Claim 4, characterized by the use of polymers and The drying process for carbon nanotubes is carried out at a temperature of 85 °C.

9. This is a piezoresistive sensor manufacturing method that complies with Claim 4, and its characteristic is; polymer and 20 The drying process of the carbon nanotube mixture was carried out at a temperature of 55 °C for 6 hours. It is to be done.

10. This is a piezoresistive sensor manufacturing method that complies with Claim 4, and its characteristic feature is that the manufactured conductive material... 25-part periodic composite filament modeled using melt deposition (FDM) method Printing process step of Gyroid matrix with minimum surface (TPMS) geometry (3) It includes.

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