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Examining Self-Powered Intelligent Apparel

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Intelligent Apparel
The most popular textile-based energy harvesters utilized in the creation of numerous self-powered smart wearables are PEGs and TEGs, which are briefly discussed in this section.

Because they feel “next to skin,” e-textiles-based sensors and actuators are becoming more and more popular in the wearables industry for a variety of applications. Unfortunately, it is discovered that the vast majority of these gadgets rely on outside power sources. This raises additional sustainability issues in addition to increasing design complexity. An AA battery has a carbon impact of about 0.107 kg CO2 equivalent.

Currently, practically every commercial device on the market for smart wearables depends on external power sources, such as traditional batteries that can be recharged or used once. According to a Swedish Environmental Research Agency study, 150–200 kg of CO2 are produced for every kilowatt hour of batteries produced. Textiles are being designed as power producers to be integrated into micro-electromechanical systems (MEMS) to enable them to run on their own energy. The potential of textiles to harvest and store energy in various forms has been the subject of much continuing research. While scientists, businesspeople, designers, and engineers continue to struggle to create e-textile wearables that are capable of reliable, repeatable, and scalable sensing and actuation, they are investigating the energy harvesting and storage potential of Textiles have also received attention recently. A few textile-based energy harvester examples are briefly discussed in this article.

Because of certain inherent qualities of textiles and those acquired through finishes or structural arrangement within an ensemble, there are multiple ways to harvest energy using textiles. Utilizing diverse energy sources, textile-based energy harvesters are necessary to produce electrical power from textiles. Photovoltaics, thermoelectricity, triboelectricity, and piezoelectricity are the four most often used techniques for this.

It is possible to weave piezoelectric elements into textiles so that, when stretched or bent, they produce electricity. When two materials with dissimilar electrostatic properties come into touch and separate, the triboelectricity property allows for the generation of an electric charge. Solar cells are used in photovoltaic fabrics to turn light into electricity. To capture solar energy, for instance, solar panels or cells can be incorporated into textiles, such as clothes or outdoor fabrics. When there is a temperature difference across materials, thermoelectricity causes the materials to generate electricity. Thermoelectric materials can be incorporated into textiles to harness the temperature differential between the human body and its surroundings and transform it into electrical energy.

These power sources, also known as nano generators, are combined with e-textiles in a small form factor to make MEMS. Triboelectric Nanogenerators (TENGs) are based on the principle of triboelectricity, whereas Piezoelectric Nanogenerators (PENGs) are based on the principle of piezoelectricity. In general, they are referred to as Triboelectric Generators (TEG) and Piezoelectric Generators (PEG). Many prospective autonomous smart wearables have been designed and developed using PEGs and TEGs.

The energy harvesters mentioned above use renewable energy sources, making them a sustainable source of electricity. For instance, wearable gadgets may simply access and utilize bodily movement, heat, and metabolic potential as energy sources. Throughout the day, a human performs a variety of tasks that result in both voluntary and involuntary motions. These motions generate energy, which can be caught by energy harvesters to provide power. The energy produced by a person’s various body parts when walking is shown in Table 1, which is based on the assumption that the individual weighs 80 kg and walks 4 km/h.

Throughout the day, a human performs a variety of tasks that result in both voluntary and involuntary motions. These motions generate energy, which can be caught by energy harvesters to provide power. The following table, which assumes a person weighing 80 kg and walking at a pace of 4 km/h, lists the energy produced by each portion of the human body while walking.

Table 1 : – Walking generates energy in several body areas.

Body parts Power (in watts)
Shoulder 1.34
Elbow 0.78
Hip 7.2
Ankle 18.9
Heel Strike 1-10
Knee 33.5

The goal of this paper is to discuss PEG and TEG design and development. A schematic of piezoelectric energy harvesting in a textile-based ensemble is shown in Figure 1. In this instance, the mechanical force of stress, or pressing, has been employed to facilitate electron movement.

Figure 1: Piezoelectric energy harvesting principle

PENGs that satisfy the required degree of miniaturization for smart textiles and the actuation capabilities connected to human motion have been proposed in a number of designs. As an example, BaTiO3 nanowires aligned with polyvinyl chloride (PVC) polymer resulted in a hybrid arrangement of piezoelectric fibers. These fibers were woven into a plain weave fabric in the warp direction, and in the weft direction, cotton yarns and copper wires were used as insulating spacers and electrodes, respectively. This configuration yielded voltages close to 2V and an output power of 10 nW when used in an elbow band.

Likewise, yarns were manufactured by twisting and plying polyvinylidene fluoride (PVDF) electrospun nanofibres, which were subsequently woven into fabrics. With a 280 mN force, this method produced a voltage output of 2.5 V. ZnO nanorods printed on textiles were explored as a potential alternative for the creation of textile-based PENGs. To serve as one of the PENG electrodes, a homogeneous array of closely spaced, vertically oriented ZnO nanorods was created on the silver-coated surface of a nylon woven fabric. In order to create the sandwich structure, a another piece of the same cloth with a silver coating screen-printed on it was used as the counter electrode. Palm clapping and finger bending were used to produce power outputs of 80 nW and 4 nW, respectively. Interestingly, multiple light-emitting diodes were illuminated by foot-stepping actuation.

Figure 2: PEG developed by a sandwich woven structure

Piezoelectric energy

Figure 3: PEG developed by 3D spacer knit structure of textiles

TEG emerges as the second most potential energy harvesting method after PEG since it focuses on obtaining energy from the majority of naturally occurring motions. Figures 4 and 5 provide schematic representations of various techniques for triboelectricity-based energy harvesting in an ensemble.

Figure 4: Principle of triboelectric energy harvesting

Nanomaterials | Free Full-Text | An Energy Harvester Coupled with a Triboelectric Mechanism and Electrostatic Mechanism for Biomechanical Energy Harvesting

Figure 5: Triboelectricity is produced by both deliberate and involuntary movements in the human body.

A hybrid energy harvester based on triboelectric and photovoltaic principles has been developed by researchers at Georgia Institute of Technology. This allows electricity to be generated by both solar energy and wearer motion from a TENG-based ensemble. A different study conducted at Georgia Tech describes the creation of energy-harvesting yarns based on triboelectricity.

These yarns are washable and work well with any typical clothing composed mainly of polyester, cotton, silk, and wool. They have the ability to gather energy when a dog walks or waves its arms. The design is rather straightforward and takes the shape of a core-shealth structure. The dielectric material in the shealth may be cotton or polyester, and the core would be composed of flexible steel fiber yarn with a diameter of 50 micrometers, which serves as a conductor. The electrons can go from the dielectric to the conductor due to the close proximity of these two materials, which have different levels of electronegativity.

The shealth section becomes closer to the core part when the yarn is stretched, and it disappears when it is relaxed. When two layers of cloth, like a sleeve with a body, rub against one another, current is also produced. Tens of milliwatts or so can be harvested per square meter using these generators. Even while it might not seem like much, a jacket-sized triboelectric generator could produce 100 mW of energy simply from the wearer’s fidgeting, which is sufficient to power tiny sensors or transmit a burst of data several hundred meters distant. A tiny patch made with this yarn was sewed to a sock’s sole for testing. It was discovered to charge a 1V capacitor.

Currently, practically every commercial device on the market for smart wearables depends on external power sources, such as traditional batteries that can be recharged or used once. According to a Swedish Environmental Research Agency study, 150–200 kg of CO2 are produced for every kilowatt hour of batteries produced.

The construction of a triboelectric nanogenerator, including a 4-plied nylon yarn coated with silver, insulated with silicone, and knitted alongside a 3-ply twisted cotton yarn, is schematically depicted in Figure 6. This is an illustration to help readers appreciate the beauty of textiles and the chance they present to build a product through the manipulation of material and structure at many levels and in various forms, whether chemical or physical.

Stretchable Triboelectric Fiber for Self-powered Kinematic Sensing Textile | Scientific Reports

Figure 6: Triboelectric generator based on yarn

I am aware that you have probably seen a ton of lab-tested textile-based energy harvesters by now. A handful that I saw were photovoltaic in nature, which as a Textile Engineering student does not particularly interest me.

In order to incorporate photovoltaic technology into fashionable and comfortable apparel, Dutch designer Pauline van Dongen worked with solar energy specialist Gert Jan Jongerden and Christiaan Holland from the HAN University of Applied Sciences on the Wearable Solar project. The two prototypes are made of wool and leather, and have sections with solar cells that can be folded up discretely when not in use, or exposed when exposed to sunlight.

There are 48 stiff solar cells in the coat and 72 flexible solar cells in the dress. Each prototype can store enough energy to fully charge a common smartphone after one hour of wear in direct sunlight. Exploring sustainable alternatives is crucial when fossil fuels run out, and the Wearable Solar project uses the sun’s abundant energy. Similarly, companies such as Tommy Hilfiger developed jackets that featured silicon solar panels covered by a snap button closure on the back of the jacket. These jackets retailed for US $400 on e-Bay.

Solar garments designed by Pauline van Dongen

Figure 7: Pauline van Dongen’s solar-themed clothing

Pauline revealed her plan in 2022 to “reupholster our built environment” with the use of a cloth that produces solar energy (Figure 7), which she is creating in collaboration with Tentech, a manufacturer. Suntex is the name of the fabric. According to reports, it’s a strong, water-resistant solar textile that may be used to cover whole structures, converting them into enormous solar energy plants. Organic photovoltaic (OPV) solar cells, which are composed of a specific polymer, are woven with recycled yarns to create the fabric.

Indeed, if you investigate the local business market, photovoltaics will be largely in the lead. Despite their apparent promise, PEGs and TEGs have not yet gained commercial traction. However, the time is not far off when producers of smart clothes made with e-textiles will, if not by choice, be forced by legislation to incorporate these energy generators into their products in order to take a more sustainable stance. In addition, the Information Technology Laboratory claimed a few years ago that military personnel use more batteries than bullets during combat.

in part because a soldier must discard 70% of the batteries they would otherwise carry while on the battlefield. At the onset of the mission, all batteries are replaced to guarantee that there will be no battery failure in the field. This process takes approximately forty minutes. With today’s sophisticated weapons and ammunition, one cannot risk the device’s operation due to a lack of batteries or their failure; energy harvesters are among the best alternatives. This information encourages industry and researchers to move further with energy collecting capabilities!

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