Micropatterning of PAni hydrogel by ink-jet printing (A–C) and spray coating (D).
The future of medical sensors very much depends on the biocompatibility of materials that will be available to make the sensors’ components. Maintaining electric conductivity in a flexible material is another challenge, since metals conduct but don’t bend very well.
A sample of the new electrically conductive hydrogel. Credit: Linda Cicero
Researchers at Stanford have created a new conducting polymer hydrogel that features high electrochemical activity and can be easily deposited onto surfaces using an ink-jet printer or simply sprayed on. The new material also has other desirable properties that may make it highly valued in the medical space space.
More about the material from Stanford:
Bao and Cui made the gel by binding long chains of the organic compound aniline together with phytic acid, found naturally in plant tissues. The acid is able to grab up to six polymer chains at once, making for an extensively cross-linked network.
“There are already commercially available conducting polymers,” said Bao, “but they all form a uniform film without any nanostructures.”
In contrast, the new gel’s cross-linking makes for a complex, sponge-like structure. The hydrogel is marked with innumerable tiny pores that expand the gel’s surface area, increasing the amount of charge it can hold, its ability to sense chemicals, and the rapidity of its electrical response.
Still, the gel can be easily manipulated. Because the material doesn’t solidify until the last step of its synthesis, it can be printed or sprayed as a liquid and turned into a gel after it’s already in place – meaning that manufacturers should be able to construct intricately patterned electrodes at low cost.
Most hydrogels are tied together by a large number of insulating molecules, reducing the material’s overall ability to pass electrical current. But phytic acid is a “small-molecule dopant” – meaning that when it links polymer chains, it also lends them charge. This effect makes the hydrogel highly conductive.
The gel’s conductance is “among the best you can get through this kind of process,” said Cui. Its capacity to hold charge is very high, and its response to applied charge is unusually fast.
The substance’s similarity to biological tissues, its large surface area and its electrical capabilities make it well suited for allowing biological systems to communicate with technological hardware.
Most hydrogels are tied together by a large number of insulating molecules, reducing the material’s overall ability to pass electrical current. But phytic acid is a “small-molecule dopant” – meaning that when it links polymer chains, it also lends them charge. This effect makes the hydrogel highly conductive.
The gel’s conductance is “among the best you can get through this kind of process,” said Cui. Its capacity to hold charge is very high, and its response to applied charge is unusually fast.
The substance’s similarity to biological tissues, its large surface area and its electrical capabilities make it well suited for allowing biological systems to communicate with technological hardware.
Press release: Stanford researchers synthesize printable, electrically conductive gel
Abstract in PNAS: Hierarchical nanostructured conducting polymer hydrogel with high electrochemical activity