Increasing the dimensionality of transistors with hydrogels

Transistors, fundamental to modern electronics, are traditionally rigid, planar, and two-dimensional (2D), limiting their integration with the soft, irregular, and three-dimensional (3D) nature of biological systems. Here, we report 3D semiconductors, integrating organic electronics, soft matter, and electrochemistry. These 3D semiconductors, in the form of hydrogels, realize millimeter-scale modulation thickness while achieving tissue-like softness and biocompatibility. This breakthrough in modulation thickness is enabled by a templated double-network hydrogel system, where a secondary porous hydrogel guides the 3D assembly of a primary redox-active conducting hydrogel. We demonstrate that these 3D semiconductors enable the exclusive fabrication of 3D spatially interpenetrated transistors that mimic real neuronal connections. This work bridges the gap between 2D electronics and 3D living systems, paving the way for advanced bioelectronics systems such as biohybrid sensing and neuromorphic computing.