In the ongoing NDSC-supported project Soy Protein-based Soft Gels for Sensors and Soft Robotics, we developed a base gel formulation and associated processing procedure to produce gels with high conductivity, good mechanical strength, and high stretchability. In this proposal, we plan to further develop the gel to impart self-adhesion and self-healing capability to the product. These properties allow the health monitoring sensors to be able to adhere to skin without using tapes and increase the durability and reliability of the devices. In the new gel formulation, Ag+ will also be incorporated to give the gel anti-bacterial performance. This further development is expected to improve the functionality of the soy protein based gels.

The goal of this new project is to continue to improve the formulation and processing method to
impart self-adhesion, self-healing, and antibacterial property to the soy protein isolate (SPI)-
based hydrogels developed in the ongoing project.

• A new SPI-based hydrogel with additional desirable properties
• Understanding of the gel properties-formulation/processing parameter relationships
• Fabrication and application guidelines of the new gel

Update:
Mid-year report sent to PM

Update:
Final report sent to PM on 6/29/2023

View uploaded report

Conductive hydrogels, as a typical flexible soft material with structural resemblance to biological tissues and excellent electronic properties, have flourished as promising candidates for applications in the fields of artificial intelligence, soft robotics, and wearable devices. Many of these advanced applications require demanding gel properties including high stretchability, self-healing ability, adhesiveness, multi-environmental tolerance (e.g., drying and freezing), good and durable sensitivity, and comfortability on human bodies. Yet, it remains a challenge to provide all these properties at the same time in one single gel product. The goal of this project is to develop a multifunctional high-performance ionic conductive hydrogel using soy protein isolate (SPI) as a main ingredient.

The hydrogels containing mainly SPI and polyvinyl alcohol (PVA) were developed. A series of other functional agents were also added to the gel formulations to impart different gel functionalities and tailor gel properties. The contents of the ingredients were varied. Gel properties of different formulations including mechanical, self-healing, adhesion, anti-freezing, and conductivity under different temperatures were systematically tested.

It was found that multiple chemical and physical interactions could be established among the ingredients of the gel, which allow the gel’s properties to be tailored significantly by varying its formulation. One of the best formulations produced a gel that shows simultaneous high stretchability (806%), good tensile strength (22.7 KPa), high self-healing efficiency (92.31% after healing for 2 min at room temperature), favorable adhesiveness to different substrates (e.g., skin, stainless steel, glass, PP, ceramic, Teflon, ABS, wood, and paper carton), high ionic conductivity (1.52 S/m) at room temperature, and outstanding anti-freezing property (flexible and conductive at -70 °C). These desirable properties make it a promising material in advanced flexible electronics applications.

An advanced new use for SPI was developed in this project. This new use targets cutting-edge and high-value industries such as robotics, health, biomedical sciences, AI, and more. This innovative utilization holds the potential to yield substantial profits for soybean farmers and the industries.

This project can potentially increase the use of soybean and thus the income of farmers by creating a new use of soy protein.