E.H. Yang Awarded Supercapacitors Patent With Many Clean Energy Applications

Professor's co-invention could impact industries such as wearable technology, health care and even functional fashion

After years of investigating stretchable supercapacitors, E.H. Yang has been granted a patent that promises to provide a multi-use, clean-energy solution that will benefit myriad industries. Yang, a professor in the Department of Mechanical Engineering, was granted the patent for his co-invention "Stretchable Supercapacitors With Vertically-Aligned Embedded Carbon Nanotubes."

Yang and many researchers have been interested in supercapacitors, also known as ultracapacitors, due to their power density and fast charge/discharge properties. So, Yang, alongside Ph.D. students Runzhi Zhang and Junjun Ding, sought a clean-energy solution that would primarily apply to flexible electronics.

A cleaner energy storage solution

Supercapacitors store electrical energy like batteries, but unlike batteries they don't rely on chemical reactions to store energy, which provides advantages over batteries, such as longer lifespans and faster charging times. Instead of a chemical reaction, supercapacitors store energy by separating positive and negative energy on their surfaces. This separation allows them to quickly store and release large amounts of energy. This efficient energy-storage method is important for applications requiring rapid burst of power, such as electric vehicles, renewable energy systems and some electronics.

However, Yang's patent is focused on the application of this technology on a smaller scale.

"Flexible supercapacitors with good mechanical compliance can meet the practical requirements for lightweight, portable and flexible biomedical devices," said Yang. "Flexible supercapacitors can also be applied for wearable electronics, flexible photovoltaics, such as rolled-up displays, self-powered wearable optoelectronics, and electronic skins."

The problem Yang and his team had to account for was the materials used for the electrodes within the supercapacitors. One of the most promising materials for high-performance supercapacitors is carbon nanotubes (CNTs). CNTs have high electrical conductivity and stability, and their structure allows easy access to the electrolyte, which helps store and release energy efficiently. Yang was interested in using vertically aligned carbon nanotubes (VACNTs) because they offer a high surface area and great performance.

With that idea in mind, the biggest obstacle to reaching a breakthrough involved consistent construction of VACNTs onto a polydimethylsiloxane (PDMS) interface.

"This invention is anchored around the unique transfer technique of VACNTs onto PDMS," said Yang. "The CNT carpet must be placed face to face with the partially cured PDMS, letting PDMS infiltrate between each individual carbon nanotube. In this way, tips of interwoven CNTs can be embedded into PDMS. This makes an efficient supercapacitor that is stretchable laterally up to 100 percent."

Eventually, Yang and his fellow researchers grew a thick layer of interwoven CNTs and then transferred them onto a flexible PDMs film, which can stretch and bend. This structure was tested in different conditions and could maintain stable performance even when stretched, bent or twisted multiple times.

The benefits of stretchable supercapacitors

Yang's invention is aimed primarily at wearable technology and medical devices, owing to its ability to conform to the body, endure regular wear and tear, and enable continuous monitoring with minimal discomfort to people. Its lightweight, flexible and compact design also could prove valuable to the consumer electronics industry.

However, stretchable supercapacitors offer potential solutions to larger-scale challenges. Their ability to facilitate the integration of renewable energy systems into unconventional surfaces like clothing or portable shelters could be valuable to the renewable energy industry. Their adaptable design provides more options for automobile and aircraft design. They could even impact the fashion industry via advanced textiles that can power wearable electronics or provide warmth, leading to innovative fashion and functional clothing.

"By enabling more flexible and durable energy storage, stretchable supercapacitors can be used to design lightweight, energy-efficient devices across various industries. This includes the development of smart grids, portable energy solutions and advanced electronics that consume less energy and contribute to lower carbon footprints," said Yang. "The use of carbon-based materials, such as carbon nanotubes, in these supercapacitors aligns with the broader trend of using more sustainable and environmentally friendly materials."