Jia Manping, Luo Le, Rolandi Marco
Department of Electrical and Computer Engineering, University of California Santa Cruz, Santa Cruz, California, 95064, USA.
Macromol Rapid Commun. 2022 Mar;43(6):e2100687. doi: 10.1002/marc.202100687. Epub 2022 Feb 4.
Hydrogels have become the material of choice in bioelectronic devices because their high-water content leads to efficient ion transport and a conformal interface with biological tissue. While the morphology of hydrogels has been thoroughly studied, systematical studies on their ionic conductivity are less common. Here, an easy-to-implement strategy is presented to characterize the ionic conductivity of a series of polyelectrolyte hydrogels with different amounts of monomer and crosslinker and correlate their ionic conductivity with microstructure. Higher monomer increases the ionic conductivity of the polyelectrolyte hydrogel due to the increased charge carrier density, but also leads to excessive swelling that may cause device failure upon integration with bioelectronic devices. Increasing the amount of crosslinker can reduce the swelling ratio by increasing the crosslinking density and reducing the mesh size of the hydrogel, which cuts down the ionic conductivity. Further investigation on the porosity and tortuosity of the swollen hydrogels correlates the microstructure with the ionic conductivity. These results are generalizable for various polyelectrolyte hydrogel systems with other ions as the charge carrier and provide facile guidance to design polyelectrolyte hydrogel with desired ionic conductivity and microstructure for applications in bioelectronic devices.
水凝胶已成为生物电子设备中的首选材料，因为其高含水量可实现高效离子传输，并与生物组织形成贴合界面。虽然水凝胶的形态已得到充分研究，但对其离子电导率的系统研究却较少见。在此，我们提出一种易于实施的策略，用于表征一系列具有不同单体和交联剂含量的聚电解质水凝胶的离子电导率，并将其离子电导率与微观结构相关联。较高的单体含量由于电荷载流子密度增加而提高了聚电解质水凝胶的离子电导率，但也会导致过度溶胀，这在与生物电子设备集成时可能会导致器件失效。增加交联剂的用量可以通过提高交联密度和减小水凝胶的网孔尺寸来降低溶胀率，这会降低离子电导率。对溶胀水凝胶的孔隙率和曲折度的进一步研究将微观结构与离子电导率相关联。这些结果对于以其他离子作为电荷载流子的各种聚电解质水凝胶系统具有通用性，并为设计具有所需离子电导率和微观结构的聚电解质水凝胶以用于生物电子设备应用提供了简便的指导。
