Inkjet-printed micro-supercapacitors offer viable power source to e-textiles

The development allows for the electrodes to be printed onto the fabric of garments to provide power to wearable technologies that are embedded in the clothing while allowing them to remain wearable and washable.

Supercapacitors store energy electrochemically and have advantages over ordinary batteries, such as being faster to charge and discharge, having longer lifespans and being more cost-effective.

The study – published in Advanced Functional Materials  – shows how inkjet printing ultra-thin layers of two-dimensional (2D) materials including graphene, molybdenum disulfide (MoS2) and hexagonal boron nitride (h-BN) is the most accurate way to form a layered material (a heterostructure), to create a micro-supercapacitor.

In a statement, study supervisor Professor Nazmul Karim, of the Nottingham School of Art & Design at NTU, said: “E-textiles are widely considered to be a promising healthcare solution which can help allow for the unobtrusive monitoring of human health to support diagnoses at the point of care.

“But the lack of thin and flexible power supplies has until now hindered the practical adoption of such products, so we wanted to develop ways to enable textile-based micro-energy storage devices to provide the energy that is needed.

“This research could open a new era in high-performance textile-based micro-supercapacitors which will power the future wearable e-textiles for personalised health care.” The study demonstrates that inkjet printing is the required high-precision method of creating these heterostructures as it allows for materials to be deposited the most precisely on substrate materials such as textiles.

The researchers used graphene as a conductor, MoS2 as a semiconductor, and h-BN as an insulator. The conductive graphene layers were printed on the top and bottom of the heterostructure, while the semiconductor (MoS2) and insulator (h-BN) were sandwiched in the middle.

"The highest capacitance was achieved for graphene-h-BN-graphene-based configurations, a maximum of 32.5 mF cm−2,” said Professor Karim. “The energy and power densities were 18.06µWh cm−2 and 4333.33µW cm−2 respectively.”

Dr Shaila Afroj, an Associate Professor of Sustainable Materials at Exeter University, said: “The key challenge to wearable e-textiles is the requirement for a lightweight, flexible and high-performance power supply unit. “Supercapacitors or ultracapacitors have gained greater attention as energy storage devices compared to batteries, mainly because of their rapid charging and discharging rates, long cycle life and cost-effectiveness. “This study shows how inkjet printing is a promising and sustainable solution for the fabrication of fully smart, wearable, and eco-friendly supercapacitors for wearable electronics applications.”