3D-Printed Flexible Pressure Sensors Based on Deep Eutectic Ionic Conductors for Motion Monitoring

Flexible pressure sensors have shown broad application prospects in motion monitoring, wearable healthcare, and human–machine interaction. However, conventional sensing systems that rely on rigid electronically conductive fillers to construct conductive pathways often suffer from insufficient compliance, interfacial mismatch, and limited cyclic stability. Deep eutectic solvents (DESs) are attractive candidates because of their facile preparation, tunable composition, abundant hydrogen-bonding interactions, and favorable ionic transport behavior. Hence, we propose a filler-free digital light processing (DLP)-printable ionic elastomer ink based on a pentaerythritol tetrakis(3-mercaptopropionate) (PETMP)/trimethylolpropane triacrylate (TMPTA)/epoxy resin (EP) photocurable matrix and a directly incorporated choline chloride (ChCl)/2-hydroxyethyl methacrylate (HEMA) DES ionic conductive phase. Through combined thiol-ene and thiol-epoxy click reactions, a stable elasticity-dominated network was formed, enabling the fabrication of a ring-shaped flexible pressure sensor with a rhombic pore-array structure. The optimized printable ink exhibited a low viscosity of 16.71 mPa·s and a short rheological gelation time of approximately 6.00 s in the UV-assisted rheological curing test, while the ring-shaped sensor structure could be printed within 24 min 8 s. The as-prepared sensor exhibited a broad response range of 0–281.9 kPa, fast response/recovery times of 80.5/102.4 ms, and stable cyclic performance over 2000 cycles. In addition, the device enabled glove-assisted finger-motion monitoring, discrimination of different compressive strains, and Morse-code signal recognition, indicating its potential for motion monitoring. This study provides a potential strategy for readily fabricating DLP-printable flexible deep eutectic ionic sensors.