In this project we plan to develop a soy protein-based, freeze-tolerant, conductive, strong, highly stretchable hydrogel for mechanical sensor applications. This gel is based on our patented soy protein resin platform (US patent 17/247,246) developed with the support of ND Soybean Council. Hydrogels have been widely used in pharmaceutical and biomedical applications in the past decades. Most recently, hydrogels that offer high strength, outstanding conductivity, and high stretchability have been intensively studied for potential uses in soft electronics including mechanical sensors, health monitoring devices, wearable devices, and soft robotics. In this project, a double-network structure will be created in the soy based-hydrogels to impart the material strength and stretchability. Chemically modified cellulose nanocrystals will be added for improved mechanical properties and conductivity. A glycerol/H2O binary solvent system will be used to provide anti-freezing property. The formulation and processing method of the gel will be meticulously adjusted and optimized for the application. Proof of concept prototypes including flexible circuit and deformation sensor will be produced and demonstrated.

To develop a novel soy protein-based hydrogel that is suitable for soft/flexible electronics use. The ultimate goal of this project is to expand the use of the patented soy protein resin and further increase soy’s market potential.

• Soy protein-based hydrogels that have the desirable mechanical and electrical properties
• Understanding of the mechanical and electrical behavior of the gel under different deformation and temperature conditions
• Fabrication and user guidelines of the hydrogel

Update:
We have successfully prepared soy protein-based, double-network conductive organo-hydrogels with high mechanical properties and good conductivity. We will proceed to study the gel’s anti-freeze property and drying behavior. We will use optimized gels to demonstrate their applications in flexible electronics.

Update:

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Soy Protein-based Soft Gels for Sensors and Soft Robotics
-Executive Summary-

Long Jiang, Qian Ma
North Dakota State University

Soft and stretchable conductive hydrogels have attracted a lot of attention for their promising applications in the fields of artificial intelligence, soft robotics, and wearable devices. However, most existing conductive hydrogels suffer from the limitations of low mechanical robustness, low stretchability, and vulnerability to drying and freezing, which hinder their durability and application areas/environments in real life. Moreover, most of the existing hydrogels are made from non-renewable materials.

In this project, we developed a soy protein-based hydrogel that is strong, highly stretchable, conductive, and freezing and drying resistant. The strength and flexibility of the new hydrogels are attributed to the double network structure inside the material formed by the soy protein molecules and another polymer. Additives including a salt, low-temperature plasticizer, and a natural fibrous material were incorporated into the hydrogel formulation to offer them the other desirable properties. The formulation was meticulously investigated, and the key ingredients and their contents were identified. The hydrogels with properties suitable for a scope of different applications can therefore be produced by adjusting the formulation.
The flexibility and stretchability of the hydrogels even under very low temperatures (up to -70 °C) are demonstrated in Figure 1, where they are bent and stretched without fracture. At the same time, the conductivity of the hydrogels under these low temperatures is still high enough to lighten up LEDs (Figure 2). The properties exhibited by these new gels make them ideal materials for making wearable sensors and soft robotics. Further development can be pursued to enable industrial applications.

A potential high-volume new use of soy protein that can increase soybean value and farmers’ income