Heterogeneous Networks in 3D-Printed Deep Eutectic Solvent Gels for Tough, Low-Hysteresis Flexible Sensors

Flexible sensors are promising in human health monitoring, soft robotics, and smart healthcare, yet their practical applications remain challenged by complex fabrication, poor mechanical robustness, high hysteresis, and limited environmental adaptability. Herein, we develop a DLP-printable deep eutectic solvent (DES) gel based on heterogeneous network engineering and microstructural design. Using a DES precursor composed of two hydrophilic monomers, acrylamide (AAm) and hydroxyethyl acrylate (HEA), together with choline chloride (ChCl) and water, a microphase-separated DES gel is directly constructed through in situ photopolymerization during the DLP printing process. The resulting microphase-separated structure, arising from the different solvation affinities of PAAm- and PHEA-rich segments toward the ChCl/H 2 O-based DES medium, endows the gel with an excellent combination of high stretchability (>1500%), high toughness (12.4 MJ m –3 ), low hysteresis (∼5%), efficient self-healing capability (95% at room temperature and 77% at −18 °C), favorable ionic conductivity, and low-temperature tolerance. Leveraging these properties, the DES gel is further developed into a resistive strain sensor for stable monitoring of human motion. In addition, DLP-defined microstructured ion-conductive layers enable pressure-dependent interfacial contact modulation, leading to high-sensitivity capacitive sensing of subtle physiological signals. The printed sensor also demonstrates potential for Morse code communication, highlighting its promise in human–machine interaction. This work provides a practical strategy for the development of high-performance flexible electronic devices.