NH2SiO2-Cellulose Acetate Equipped Triboelectric Nanogenerator for Pressure Sensors

Abstract

ABSTRACT Synergetic Combination of Holmium Tungstate/Reduced Graphene Oxide for Electrochemical Sensing of Mesalamine In this invention, an amino-functionalized SiO2/cellulose acetate nanocomposite (CA/F-SiO2) is developed as an effective triboelectric positive material for high-performance triboelectric nanogenerators (TENG). The proposed nanocomposite, used in conjunction with PVDF nanofiber, exhibits enhanced triboelectric properties, achieving a peak-to-peak electric output of 74 V and a current of 4 µA, resulting in an instantaneous power density of 16 mW m⁻² at 1 GΩ. The optimal composition of 10% amino-treated SiO2 nanofillers in the CA matrix significantly improves the triboelectric charge density due to the formation of -NH2 chemical bonds on the SiO2 surface. Comprehensive testing demonstrated the CAFS-TENG’s capabilities in capacitor charging, LED powering, and harvesting biomechanical energy from human motions such as walking, running, jumping, and stomping. Furthermore, the device functions effectively as a self-powered pressure sensor, capable of detecting low pressures for various applications. The results indicate that our invention is a promising solution for use as a self-powered pressure sensor, contributing to advancements in sustainable energy harvesting technologies.

Specification

Description:
FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

Complete Specification
(See section 10 and rule 13)


1.Title of the Invention:
NH2SiO2-Cellulose Acetate Equipped Triboelectric Nanogenerator for Pressure Sensors
2. Applicant
Name Nationality Address
KONERU LAKSHMAIAH EDUCATION FOUNDATION Indian Koneru Lakshmaiah Education Foundation, Green Fields, Vaddeswaram, Guntur, Andhra Pradesh 522302
S.R. SRITHER Indian Centre of Excellence for Nanotechnology, Koneru Lakshmaiah Education Foundation, Green Fields, Vaddeswaram, Guntur, Andhra Pradesh 522302


3. Preamble to the Description:
The following specification particularly describes the invention and the manner in which it is to be performed.


4. DESCRIPTION
Field of the Invention
The present invention relates to the field of energy harvesting and self-powered sensing technologies, specifically focusing on the development of triboelectric nanogenerators (TENGs) for harnessing biomechanical energy and for pressure sensing applications. The invention utilizes nanocomposite materials, incorporating amino-functionalized silicon dioxide (SiO₂) nanofillers within a cellulose acetate (CA) matrix, combined with polyvinylidene fluoride (PVDF) nanofibers, to enhance the electrical output performance of the TENG devices. These TENGs are capable of converting mechanical human motion into electrical energy, making them particularly suitable for wearable health monitoring systems and self-powered pressure sensing applications. The fabricated TENG can harvest energy from various human movements, including walking, running, jogging, or other mechanical activities. Additionally, it functions as a self-powered pressure sensor, responding to different forces without requiring external power sources.
Background of the Invention
Initial research focused mainly on enhancing electron-donating and accepting tribomaterials by exploring novel materials with favourable triboelectric polarities [1-3]. Later research tried to boost the surface charge density of triboelectric materials by changing the structure of the device, making the surface rougher, and adding active materials [4-6]. Physical modifications, particularly micro/nanostructure patterning, are widely used to alter the surface morphology of triboelectric materials [7,8]. Additionally, there have been developments in liquid-solid friction materials to replace solid-solid friction materials [9,10]. Researchers are looking into microporous structures that resemble sponges [11] and adding a charge transport layer between electrodes and triboelectric materials [12]. However, physical methods for modifying frictional materials often result in poor mechanical wear resistance, potentially damaging the patterned surface and significantly diminishing the ability to improve frictional charge.
Chemical modification, on the other hand, can be used to treat materials chemically by changing their functional groups so that they can donate or accept electrons without changing the properties of the triboelectric material. Feng et al. [13] suggested using CNTs and amide bonds on the fiber surface to create a hierarchical nanostructure, which is an easy way to improve the triboelectric performance of commercial velvet fabric. Cao et al. published a study on polymer composites with chemically modified Ti3C2 fillers. They functionalized Ti3C2 with PVDF-TrFE and nylon 11 materials to enhance triboelectric output performance [14]. Similarly, there have been very few attempts to chemically modify the triboelectric polarity of the fillers, whereas most of the research focuses on developing tribonegative materials using synthetic polymers [15, 16]. To date, the available tribopositive materials for flexible applications are limited, ineffective, and typically not environmentally friendly. Therefore, investigating environmentally friendly tribopositive materials derived from biopolymers is highly desirable.
Objectives of the Invention
• Develop a novel amino-functionalized SiO2/cellulose acetate nanocomposite (CA/F-SiO2) to serve as an effective triboelectric positive material for enhancing TENG output performance.
• Investigate the effect of different loading ratios of amino-treated SiO2 nanofillers incorporated in the CA matrix to achieve maximum triboelectric output performance and compare the output with that of the cellulose acetate matrix.
• Evaluate the cyclic stability and mechanical durability of the CAFS-TENG device under prolonged operational conditions, including testing the mechanical strength and structural integrity of the tribolayer of the TENG.
• Demonstrate the capacitor charging and LED powering capabilities to showcase the practical applications of the CAFS-TENG in energy harvesting.
• Test the CAFS-TENG device for its ability to harvest biomechanical energy from various human motions, including walking, running, jumping, and stomping.
• Explore the capability of the CAFS-TENG as a self-powered pressure sensor, evaluating its performance in detecting low pressures for various applications.
• Conduct practical real-time demonstrations to highlight the promising potential of the proposed nanocomposite material CA/F-SiO2 for future applications in self-powered motion sensing and pressure sensing.
Summary of the Invention
Novel triboelectric active materials provide triboelectric properties, which are crucial for fabricating high-performance triboelectric nanogenerators (TENG). Currently, the limited availability of triboelectric positive materials necessitates the exploration of attractive triboelectric materials with high positive tribopolarity and environmentally friendly properties. Here, we propose an amino-functionalized SiO2/cellulose acetate nanocomposite (CA/F-SiO2) and employ it as an effective triboelectric positive material, in conjunction with PVDF nanofiber as a negative layer to fabricate a high-output CAFS-TENG. We systematically varied the ratios of amino-treated SiO2 nanofillers in the CA matrix, identifying a 10% loaded concentration as the optimal sample. The CA/F-SiO2-based device had a peak-to-peak electric output of 74 V and 4 µA, and it had an instantaneous power density of 16 mW m-2 at 1 GΩ, which was higher than the CA/SiO2-based TENG. The surface functionalization showed that the NH2 chemical bond formed on the SiO2 surface greatly increased the triboelectric charge density. This improved the TENG's overall output performance when it was separated from the PVDF nanofiber. To demonstrate its capabilities, we conducted capacitor charging and LED powering tests. The cyclic stability test demonstrated excellent electrical performance and mechanical durability over extended cyclic operations. Furthermore, we tested the CAFS-TENG device in real-time analysis to harvest biomechanical energy from rapid human motions like walking, running, jumping, stomping, etc. Additionally, we demonstrated it as a self-powered pressure-sensing device, capable of detecting low pressures for a variety of applications. The CAFS-TENG, as evidenced by the test results and real-time analysis, emerges as a promising candidate for powering electronic components and serving as a self-powered pressure sensor in diverse applications.
Brief Description of accompanying Drawings
Figure 1a illustrates the assembly of PVDF nanofiber and CA/F-SiO nanocomposite layers on acrylic substrates during the fabrication process of the CAFS-TENG device. It gives complete visual representation of its structural design and configuration steps. The positive layer CA/F-SiO2 and negative layer PVDF nanofiber were successfully prepared using spin coating and electrospinning method. Figure 1b displays layer-by-layer schematic process steps and a digital image of the assembled CAFS-TENG. Figure 2a depicts the operational mechanism of the CAFS-TENG, demonstrating the generation of electricity through contact electrification and electrostatic induction upon the contact and subsequent separation of the triboelectric layers. Figure 2b compares the output voltage of CA/SiO₂ and CA/F-SiO₂ TENGs, demonstrated that the CA/F-SiO₂ nanocomposite exhibits superior charge generation due to the functionalization of SiO₂ nanoparticles. Figure 2c shows a simulation from COMSOL Multiphysics of the potential distribution across the device, illustrating how surface potentials change from the initial pressed state to the maximum release state. Figure 3a presents results from mechanical and electrical endurance tests. The results indicated that the CAFS-TENG maintains stable voltage output over numerous operational cycles and is capable of powering at least 58 commercial LEDs connected in series. Figure 3b depicts the voltage response of the CAFS-TENG during various human movements (e.g., finger tapping and leg tapping). The device is operated to demonstrate its ability to harvest biomechanical energy. Figure 3c displays voltage outputs from different rapid movements like walking and jumping, showing how the output voltage varies based on the force and type of activity involved. As expected, our device is capable to harvest electrical energy from all kinds of movements from the body. Figure 3d depicts the output voltage response of individuals with different body weights standing on the device, illustrating the correlation between body weight and generated voltage. Figure 3e shows the TENG working as a pressure sensor that detected the pressure from small-weight objects dropped from a height. The demonstrated results showed a linear relationship between the applied force and the generated voltage.
Detailed Description of the Invention
APTES functionalization of SiO2 nanoparticles
In the nanocomposite preparation, 250 mg of SiO2 nanoparticles are functionalized with 3-aminopropyltriethoxysilane (APTES) to improve their triboelectric properties and integration into nanocomposites. The SiO2 nanoparticles are first dispersed in 9 mL of ethanol, followed by the addition of 1 mL of APTES. This mixture is continuously stirred and heated at 50°C for 24 hours to allow for sufficient surface functionalization. Upon completion of the reaction, the solution is centrifuged to separate the functionalized nanoparticles, which are then washed multiple times with deionized water and ethanol to remove any residual impurities. The resulting APTES-functionalized SiO2 nanoparticles are dried at 50°C, to obtain a fine powder for preparing nanocomposite.
Preparation of positive triboelectric layer: CA/F-SiO2 nanocomposite
To prepare the positive triboelectric layer, different weight ratios of APTES-functionalized SiO2 nanoparticles (1%, 3%, 5%, 10%, and 20% w/v with respect to cellulose acetate (CA) concentration) are dispersed in dimethylacetamide (DMAc) solvent. This dispersion is stirred and sonicated until a fine distribution of nanoparticles is achieved. Then, 10% CA is added to the solution, and the mixture is stirred vigorously at 60°C until a homogenous solution is formed. This blended solution is subsequently spin-coated onto the conducting indium tin oxide (ITO) side of a polyethylene terephthalate (PET)/ITO film substrate. The coated film is then dried for 12 hours in a vacuum oven at 60°C. As a control, pure CA and as-synthesized SiO2 nanoparticles at the same weight ratios are prepared under the same conditions for comparison.

Preparation of negative triboelectric layer: PVDF nanofiber
The negative triboelectric layer is fabricated using polyvinylidene fluoride (PVDF) nanofibers. To prepare the PVDF nanofibers, a 16 wt% PVDF solution is created by dissolving PVDF in a mixture of 3.36 mL N,N-dimethylformamide (DMF) and 2 mL acetone. The solution is stirred and heated at 60°C until it becomes a clear and homogeneous solution with a suitable viscosity for electrospinning. The viscous solution is then loaded into a 5 mL plastic syringe equipped with a 21-gauge needle. During the electrospinning process, a 15 kV direct current (DC) voltage is applied to the needle, and the flow rate is set at 1 mL/h, with a 15 cm gap between the needle and the rotating collector drum. The electrospun PVDF nanofibers are deposited onto the ITO-coated side of the PET film, forming a uniform negative triboelectric layer.

CAFS-TENG device assembly
The triboelectric nanogenerator (TENG) is assembled by combining the positive and negative triboelectric layers. The CA/F-SiO2 nanocomposite layer spin-coated on the PET/ITO film and the PVDF nanofiber-coated PET/ITO film are both cut into 3 × 3 cm² pieces. These two layers are then fixed and mounted on acrylic sheets using double-sided adhesive tape. A OHP transparent sheets are used to cover the two edges of the films to be acted as a spacer, establishing a contact-separation TENG configuration. The ITO electrodes on each film are connected using thin aluminium wires to facilitate the flow of generated charges. This setup allows for efficient energy harvesting through the contact-separation mechanism of the triboelectric layers, with optimized performance due to the chemical and physical modifications introduced to the triboelectric materials.
The above device assembling will enable efficient charge generation and mechanical energy harvesting, incorporating the combination of APTES-functionalized SiO2 nanoparticles in the cellulose acetate matrix for enhanced triboelectric performance.
Operation of the proposed device
Two different triboelectric materials work together to make the CAFS-TENG work by using contact electrification and electrostatic induction to make electricity. The initial neutral mode separates the two triboelectric layers, preventing any accumulation of charges. Applying a vertical force presses these layers together, causing positive and negative charges to accumulate on the CA/F-SiO2 nanocomposite and PVDF layers due to their different electron affinities, as classified by the triboelectric series. Upon releasing the applied force, the layers return to their neutral state. When separated, the dipole moment between the layer's increases, generating a potential difference that drives electrons from the bottom electrode to the top electrode. Reapplying the vertical force causes the dipole moment to decrease, causing electrons to flow in the opposite direction and producing an alternating current (AC) output. Figure 2 illustrates the mechanism of operation for CAFS-TENG.
The power output of the TENG depends significantly on the external load resistance, making it essential for practical applications. By systematically connecting various external load resistances, ranging from 0.01 MΩ to 1 GΩ, it was observed that the output voltage increases with increasing load resistance, consistent with Ohm's law. The instantaneous power density calculated using the formula P = V²/RS (where V is the output voltage, R is the resistance, and S is the contact area of the triboelectric layers), reached a maximum of 16 mW/m² at a load resistance of 1 GΩ. The device's performance is superior when compared to previously reported TENGs. Notably, while others have reported input forces ranging from 10N to 40N, the input force we gave for our device is only 2N. The capacitors were used to store the energy produced by the TENG to provide stable DC power for electronic devices. The device showed consistent output with mechanical durability across many operation cycles.
The device showed consistent output with mechanical durability across many operation cycles. The device also proved its robustness by withstanding mechanical forces up to 20 N, showcasing its potential for industrial applications. Additionally, the CAFS-TENG demonstrated the ability to power commercial LEDs, illuminating up to 58 LEDs in series. We tested the voltage response of the CAFS-TENG in biomechanical energy harvesting applications using human movements such as finger tapping, palm tapping, and foot tapping. Different activities varied the output voltage, and movements involving more forces resulted in a higher voltage. Moreover, we evaluated the voltage response of the TENG device with individuals of varying body weights, finding that higher body weights corresponded to greater voltage output, as shown in Figure 3. As a pressure sensor, the TENG could detect small forces from objects dropped from a height, with voltage output linearly proportional to the applied force. This demonstrates that the CAFS-TENG is capable of capturing a wide range of biomechanical motions and holds potential for applications in human motion sensing and pressure sensing. The economic miniaturization, portability, and deployment capabilities of the CAFS-TENG make the devices promising for all potential diverse pressure-sensing applications.
The main advantages of the present invention are
• We successfully prepare the amino-functionalized SiO2/cellulose acetate nanocomposite (CA/F-SiO2) for use in TENG as a positive material.
• The electrical output of CA/F-SiO2-TENG with a 10% SiO2 loading concentration was much higher than that of the as-synthesized SiO2-based CA/SiO2 TENG.
• The TENG device achieved a maximum instantaneous power per area of 16 mW m-2 at 1 GΩ.
• Cyclic tests demonstrated uniform electrical stability and mechanical durability, with the device able to withstand mechanical forces up to 20 N without electrical output degradation.
• We use TENG to capture biomechanical movements like finger tapping, palm tapping, and leg tapping. Real-time data is recorded for fast human actions such as walking, running, stomping, among others.
• We demonstrate a self-powered pressure sensor test in real-time, and the output demonstrates a linear response to different weights of dropped objects.
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, Claims:CLAIMS
We Claim:
1. A high-performance triboelectric nanogenerator (TENG) device for self-powered pressure sensing, wherein the triboelectric positive layer is made of a cellulose acetate (CA) matrix incorporated with F-SiO₂ nanoparticles, and the triboelectric negative layer is prepared by using polyvinylidene fluoride (PVDF) nanofibers.
2. The high-performance triboelectric nanogenerator (TENG) device for self-powered pressure sensing as claimed in claim 1, wherein the CA/F-SiO₂ nanocomposite maximizes triboelectric charge generation and accumulation of triboelectric charges, thereby achieving high triboelectric charge density and electrical output.
3. The high-performance triboelectric nanogenerator (TENG) device for self-powered pressure sensing as claimed in claim 1, wherein the triboelectric positive layer is fabricated by spin coating method, and the thickness of a coated layer was optimized to enhance maximum electrical efficiency.
4. The high-performance triboelectric nanogenerator (TENG) device for self-powered pressure sensing as claimed in claim 1, wherein the amino-functionalized SiO₂ nanoparticles were incorporated in cellulose acetate matrix at different weight ratios, the best output in electricity was achieved at a weight ratio of 10%.
5. The high-performance triboelectric nanogenerator (TENG) device for self-powered pressure sensing as claimed in claim 1, wherein the triboelectric negative layer is prepared through the electrospinning process with the help of dual solvents, optimizing the viscosity of solution and diameter of fibers at a better performance of the PVDF nanofibers.
6. The high-performance triboelectric nanogenerator (TENG) device for self-powered pressure sensing as claimed in claim 1, wherein the TENG has the capability of stable electrical performance and mechanical durability for long cyclic operation, besides it can harvest biomechanical energy from human movement like walking, running, jumping.
7. The high-performance triboelectric nanogenerator (TENG) device for self-powered pressure sensing as claimed in claim 1, wherein the CA/F-SiO₂ nanocomposite device has an electric output of a maximum peak to peak value of 74 V and 4 µA, with an instantaneous power density value of 16 mW/m² at 1 GΩ.
8. The high-performance triboelectric nanogenerator (TENG) device for self-powered pressure sensing as claimed in claim 1, wherein the electrical output that is observed coming from the device is proportional to the intensity and frequency of biomechanical motions, and which has the suitability of using such a device for real time detection and analysis of human motion.
9. A Detection method of applied force using the TENG of claim 1, wherein the device generates an electrical signal directly proportional to the pressure applied by small objects falling from a predetermined height with the output voltage linearly corresponding to the applied pressure.
10. The Detection method of applied force using the TENG as claimed inclaim 9, wherein the capability for pressure sensing by the TENG enables us to measure applied force through output voltage without the complexity associated with traditional resistance-based sensors.

Dated this the 01st November 2024.




Senthil Kumar B
Agent for the applicant
IN/PA-1549

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