Session: 13-08-01: Mechanics and Materials of Soft Electronics I

Paper Number: 173275

Sustainable Soft Electronics With Recyclable Metal Nanowire Circuits and Biodegradable Substrates 

Soft electronics employs soft dielectric and conductive materials to create devices that are soft, flexible, stretchable, and conformable. Unlike silicon-based rigid electronics, they allow interfacing with nonplanar surfaces expanding their capability in wearable sensing and monitoring as well as next-generation robotics. The current way of manufacturing soft electronics involves the use of synthetic polymers such as polyethylene terephthalate (PET), polyimide (PI), poly(dimethylsiloxane) (PDMS) as substrates that offer advantages such as tunable mechanical properties, durability, and precise control over material properties compared to natural polymers. However, concerns regarding their eco-friendliness have been raised due to their non-biodegradability and environmental impact during production and disposal. Besides, the loss of the noble metals that are used in soft electronics contributes to the depletion of scarce resources, exacerbating environmental concerns. Thus, there is an urgent need to develop “green” soft electronics based on renewable natural polymers and eco-friendly manufacturing methods that can allow recycling and biodegradation after the devices’ end of life. Natural polymers such as agarose, cellulose, chitosan, and proteins such as silk fibroin are prevalent in both plant and animal biomass, offering an environmentally sustainable alternative to their synthetic counterparts. These polymers possess unique physical and chemical properties owing to their abundant functional groups and hierarchical structures, which facilitate their functionalization using diverse manufacturing techniques. 

In this work, sustainable soft electronics are fabricated by incorporating silver nanowires (AgNWs) as recyclable functional material on a biodegradable polymer, i.e., agarose. Glycerol is an effective plasticizer for biopolymers and therefore, it was used to tune the mechanical and chemical properties of agarose and make it suitable for epidermal electronics application. Soft electronics were fabricated by screen-printing an eco-friendly AgNW-based ink on a stretchable agarose/glycerol gel substrate. The mechanical and chemical properties of the agarose/glycerol gel substrate were characterized using optical transmittance, contact angle, water vapor transmission rate, swelling behavior, and thermal properties which provided insights into the material’s structure and composition. The electromechanical properties of the printed AgNW electrodes including stretchability and durability were evaluated. The printed electrodes showed a resistance change of 55% at 20% tensile strain. Furthermore, the AgNW electrodes showed chemical stability in different media such as air, water, and sweat showcasing their feasibility for long-term wearable soft electronic applications. To demonstrate the functionality of the printed AgNWs on the biodegradable agarose/glycerol gel substrate, electrophysiological sensors were fabricated. Finally, the demonstration of the biodegradability of the agarose/glycerol gel substrate and the recyclability of AgNWs was showcased to point toward ways to develop sustainable and eco-friendly soft electronics.

Presenting Author: Yong Zhu NCSU

Presenting Author Biography: Yong Zhu is the Andrew A. Adams Distinguished Professor at NC State University.

Authors:

Darpan Shukla NC State University
Yuxuan Liu NC State University
Yong Zhu NCSU