Researchers at Hong Kong University have fabricated a new electroconductive hydrogel using the hybrid assembly of polymeric nanofiber networks, a breakthrough that could find a range of uses in biomedical applications, such as tissue repair, drug delivery and medical implants. The synthetic hydrogels offer excellent mechanical strength and manufacturability, and could also find applications in the engineering of various bioelectronic devices for cardiac or neural interfaces, as well as neural prosthetics, cardiac patches and electronic skin.
Synthetic hydrogels are polymeric materials that are water-rich and resemble biological soft tissues. They are also soft, porous and biocompatible, which enables a physical interface between natural biological tissues and some advanced biomedical tools, and are potential candidate materials for the development of soft electronics and biomedical devices because of their mechanical flexibility and structural permeability.
Despite electroconductive hydrogels already being applied in tissue engineering platforms, implantable bioelectronics and soft actuators, managing high conductivity and mechanical robustness has remained a problem. Existing hydrogels are mechanically weak and hard to make, so here a microscale scaffold was used for the synthesis of conductive hydrogels, an architecture that offered a combination of properties unavailable by other hydrogels.
The team, led by Lizhi Xu, had already developed another novel type of hydrogel that mimics tendons, and which shows excellent mechanical properties similar to those of natural tendons, along with many functionalities well-suited for biomedical applications. In this study, which was reported in the journal Nature Communications [He et al. Nat. Commun. (2023) DOI: 10.1038/s41467-023-36438-8], a 3D nanofiber network was used as a template to help guide the assembly of conducting polymers, including polypyrrole.
The high connectivity of the nanofibers offered structural robustness as well as an effective pathway for electron conduction. As Xu pointed out, “These conductive hydrogels are easy to fabricate. One can pattern them into arrays of electrodes, interconnects, and biosensors, enabling functional systems such as wearable health monitors or cardiac tissue engineering platforms.”
Their patterned conductive nanofiber hydrogels can be used as electrodes and interconnects with favorable electrochemical impedance and charge injection capacity, as well as showing that cardiomyocytes cultured on soft and conductive nanofiber hydrogel substrates demonstrate spontaneous and synchronous beating, which could lead to opportunities in the development of advanced implantable devices and tissue engineering technologies.
For biomedical applications, the device has to withstand repeated mechanical loading similar to body motion, with such mechanical robustness being crucial. The resulting material contains 80% water by weight, but also demonstrates high electrical conductivity and mechanical strength.
“These conductive hydrogels are easy to fabricate. One can pattern them into arrays of electrodes, interconnects, and biosensors, enabling functional systems such as wearable health monitors or cardiac tissue engineering platforms.”Lizhi Xu
Electroconductive hydrogels for wearable electronics Credit: The University of Hong Kong