Researchers at Stanford recently reported the synthesis of an electrically conducting hydrogel that possesses high electrical activity comparable to metals. It is easy to fabricate and patterns can be printed on its surface using a simple inkjet printer.
Professors Zhenan Bao and Yi Cui with their associates developed this new gel. They published their study in the Proceedings of the National Academy of Sciences.
The material was synthesized by binding six chains of polyaniline with phytic acid, an organic compound found in plant tissues. The resulting product is a complex cross-linked network.
Bao said there are many commercially available conducting polymers, but these are fabricated as uniform films without nanostructures. In contrast, their product has a sponge-like structure with tiny pores.
The porous structure gives the new conducting polymer its remarkable electrical activity. The pores allow expansion of the gel’s surface area, increasing the amount of charge it can hold and its ability to sense chemicals.
Cui added that most commercial polymers are tied together with large numbers of insulating molecules, which reduces the overall conducting ability of the material. In their synthesis, they chose phytic acid, which is a small molecules and functions as a dopant. This means it lends or transfers charge to the polymer chains. This further enhances the conductivity of the gel.
An important feature in the fabrication of the polymer is that it solidifies in the last step of the synthesis. This allows ease of manipulation in terms of designing patterns that can be printed or sprayed before the product hardens into a gel. As Cui said: “You can’t print Jell-O, but with this technique, we can print it and make it Jell-O later.”
The properties of the new hydrogel that includes large surface area, high conducting capacity, and fast response time to applied charges, gives it a wide array of possible applications. It can be use as medical probes, laboratory biosensors, biofuel cells and high-energy density capacitors.