Recent progress of 3D-printed polymeric gel sensors for flexible electronics

Solvent-impregnated polymeric gels, distinguished by their remarkable property tunability and excellent mechanical compatibility with biological tissues, emerge as highly promising candidates for flexible sensing materials and devices. These gel sensors are capable of transducing diverse health-related stimuli into detectable signals, thereby facilitating point-of-care diagnostics and advanced cyborg feedback systems. The reliable construction of materials or devices for gel sensors necessitates the development and application of suitable manufacturing techniques. Additive three-dimensional (3D) printing has substantial potential in this context, offering advantages such as high production efficiency and precision. This review provides a comprehensive examination of the materials and applications of 3D-printed gel sensors. The classification and physical properties of polymeric gels are first introduced as a foundation. We then focus on direct ink writing and digital light processing, with a comparative analysis of their key characteristics. Additionally, the diverse application scenarios of gel-based sensors are summarized, highlighting their versatility. Finally, the limitations of current research are critically analyzed, and potential future directions are outlined, providing a strategic framework for advancing this rapidly evolving field.