A Printable Deep Eutectic/Copper Conductive Colloid for Wearable Devices

The advancement of wearable electronics has placed higher demands on the comfort and convenience of flexible materials. In this work, a conductive pseudoplastic colloid was developed by utilizing the oxygen elements adsorbed on the surface of copper powder, which forms donor-acceptor interactions with the hydrogen bond donors in a deep eutectic solvent. The flakelike copper powder, serving as a conductive filler, provides more efficient spatial conductive pathways and further enhances the cross-linking ability between the copper powder and the deep eutectic solvent. The resulting deep eutectic/copper colloid not only exhibits low volume resistivity (1.19 × 10^-3 (Ω·m)), high viscosity, and excellent thermal stability but also demonstrates outstanding strain-resistance characteristics. By printing onto a textile substrate, a flexible strain sensor with a wide linear strain range (5-90%) and ultrahigh sensitivity (gauge factor ≈ 1 × 10⁵) was fabricated. This sensor can sensitively and stably detect human body movements such as joint and muscle motions. Furthermore, the sensor has been integrated into a portable glove for motion detection and human-machine interaction, showcasing its great potential as a high-performance wearable strain sensor.