Preparation of Flexible Strain Sensor Based on Ag by UV-Assisted Ink Direct Writing

Printable silicone resin is designed as the base layer and conductive silver paste is designed as the functional layer using UV-curing silicone resin (Si-350) as the low polymer, isobornyl acrylate (IBOA) as the monomer, fumed silica (A200) as the rheological modifier and flake silver as the conductive filler. UV-assisted ink direct writing is employed to realize the continuous printing of flexible substrate and patterned conductive functional to fabricate integrated resistance flexible strain sensor. The rheological properties of the base layer and the functional layer inks were characterized by rotational rheometer. The conductivity of the functional layer was tested by four probe tester. The mechanical properties and sensing properties of the sensor were evaluated through universal testing machine and multimeter. The results demonstrate that when the mass ratio of resin Si-350 to monomer IBOA is 2.5∶1 and the addition amount of A200 (m(A200)/(m(Si-350)+m(IBOA)) is 9%, the substrate ink has good printability and the substrate has the best mechanical properties. The functional layer with 70% silver mass fraction shows good printability and conductivity. The sensor with functional layer containing 70% silver mass fraction and 0.30 mm line width exhibits excellent sensitivity and mechanical properties. It can withstand strain exceeding 180%. By designing the functional layer in linear shape through ink direct writing printing, the sensor with curved structure exhibits optimal comprehensive performances with the ability to resist torsion and bending. This sensor is capable of monitoring human movements and holds significant potential for applications in the field of flexible wearable electronic devices.