Modern technology is pushing for devices that harness the environment to power them, and away from larger power sources. Nanogenerators are here to help. Many smaller devices are currently testing nanogenerators. These include implantable medical devices and wearable medical gadgets, IoT technologies, remote monitoring technologies, IoT technology, and self-powered air disinfection system. These are not exhaustive, but they are just some of the areas that have made progress in self-charging technology.
Although the field of energy harvesting with nanogenerators is still relatively young commercially, it does not stop people from being interested in fundamental research. Because they can power small remote devices, other energy storage/energy harvesting technologies may not be feasible or suitable due to their size and power connection requirements. Many small devices could be empowered with nanogenerators to charge themselves and allow remote applications to be made that are not possible otherwise. Although there are many nanogenerators being developed and researched, we will be focusing on the triboelectric (TENG) nanogenerator.
Triboelectric properties of a material harnessed
The use of some external stimuli to create an electrical charge can power small devices. In some cases, however, they can also be used to integrate larger electronic systems. Triboelectric nanogenerators are small, lightweight devices that capture motion from the environment and convert it to an electrical output. TENGs convert mechanical energy to electrical energy using a contact-induced electric mechanism.
Two fundamental mechanisms are used to convert mechanical motion into electrical output in TENGs. Contact electrification is one of the two mechanisms. Electrostatic charge induction is another. To convert energy from mechanical to electric, a TENG must have an active triboelectric material that is electrically charged by the interaction with an external stimulus. Contact electrification generates frictional forces that produce electrical charges on the TENG’s surface. The TENG is then subject to an electrostatic charge induction phase. Here, the surface charges are distributed across the materials of the TENG. The redistribution generates an electric current which can be used to power small-scale attachments.
A number of small-scale physical factors and chemical factors are required to generate and transfer electrical charges across the TENG. These include material deformations and fracturing, heat production, electron and ion transfers, as well as material deformations and fracturing. There is no clear association between the triboelectric effects and the fundamental material properties of a material’s triboelectric characteristics, as many factors can affect its ability to generate and transfer electricity. It is impossible to predict the amount of triboelectricity that a particular material will exhibit. Designers often use the best guess approach to determining suitable materials. They rank them according to their ability lose or gain electrons in contact.
TENGS: Why 2D Materials are Used
Because there is no way to determine if a material is triboelectric, based on its ability lose or gain electrons (which can only be done using best guesses), 2D materials quickly became an attractive candidate for research because of their intrinsic thinness. 2D materials are thin, with some having one atomic layer thickness and others having a few. This means that they are more active than bulkier materials. Therefore, electrons can interact more easily at nanoscales. Additionally, once you get into the realm of the nanoscale–especially thin surfaces such as 2D materials–quantum effects start to be observed that help facilitate the movement of electrons in ways that are not possible with bulkier materials, i.e., quantum tunneling.
TENGs have been tested with a variety of 2D materials. Some of these TENGs were made using 2D materials alone, while others used 2D materials with polymers or polymer combinations. The negative side of a triboelectric junction is usually used by most 2D materials. 2D materials are more likely to gain electrons than most other materials, resulting in a negative charging potential. This process can also be modified via doping. Doping has been successfully used in 2D material research and has been proven to increase electron capture ability in many 2D materials placed in a TENG.
2D materials are able to capture electrons and provide an emetroelectric response to friction and movement in their local environment. There are also other advantages to using 2D materials, including other nanomaterials. These are namely the high degree of flexibility, mechanical strength, durability, and transparency that you get with 2D materials–which you don’t even get with some other nanomaterials–meaning that they can undertake a great deal of mechanical stress and and offer l longevity. This is an important property because mechanical motion and friction can involve bending, depending on the application. The triboelectric materials must be able to resist bending and other mechanical stress.
The TENGs trials included materials that were specifically tailored to the specific application. Sometimes graphene-based materials can be more suitable for external medical devices, as they are more flexible than other 2D materials. They also conform better to the skin of patients. A wide range of applications have been possible with TENGs, including air disinfection, implantable pacemakers, wearable monitoring devices, remote sensor, and even powering LED TVs.
The 2D materials include graphene and its derivatives, MXenes and transition metal dichalcogenides, (TMDCs). Most of the research on graphene has been done. TMDCs are the most well-known, with molybdenum diulfide (MoS 2) being the most prominent among all TMDCs.
Although graphene has been favored in some applications, molybdenum diulfide is considered one of the most promising because it exhibits a quantum confinement effect which acts as a charge-trapping agents. Its energy level and large surface area make it ideal for electron transfer. It is currently a general triboelectric materials for TENGs. It exhibits the highest output voltage, current, and current. However, the use of molybdenum dioxide and other 2D material within TENGs is still controlled by the application requirements. The electrical output is not always the driving factor for certain applications. Flexibility and biocompatibility, for example, may also be driving factors. Many different 2D materials are available to support specific applications. The material options and scope of application will expand over the next few years.
Conclusion
TENGs will see more benefits from 2D materials than bulkier materials or other nanomaterials. 2D materials have a thinner surface which allows for more efficient electron movement and triboelectric responses. They are flexible and durable, making it possible to create TENGs with longevity. Although there is a lot of interest in TENGs being made for remote and small-scale devices, research has shown that TENGs can also be used to power larger electronic devices like TVs.
