Surface acoustic wave-assisted fabrication of Ag/PEGDA conductive films for flexible sensing applications

Flexible conductive films have been increasingly demanded for wearable devices that are widely applied. However, existing fabrication methods are limited by uneven particle distribution, complex processes, and material selectivity. Herein, a particle manipulation method based on surface acoustic wave (SAW) technology was proposed to align spherical silver (Ag) particles and fabricate a flexible conductive film with a linear arrangement structure. The process for fabricating conductive films was optimized by investigating the influence of the dielectrophoresis (DEP) effect, along with the effects of chamber height and solution solid content, on the alignment of Ag particles. Besides, the conductivity of the films and their applications in flexible sensing including wrist bending, finger short-term and continuous pressing actions were explored. Results showed that the acoustic radiation force dominates the aggregation of spherical-like Ag particles into periodic stripe patterns along the acoustic pressure node lines at locations distal to the substrate. Ag particles at the potential nodes are dominated by the dielectrophoretic force, leading to the formation of chain-like structures, which can be eliminated by utilizing the electric field shielding layer. The optimized film has a high conductivity of 4774 S/m and exhibits stable resistance characteristics during flexible deformation. The resistance change can be attributed to the changes in particle spacing, the breakage and recovery of conductive paths caused by deformation. The current work provides a new scheme for the fabrication of conductive films with high process controllability in the field of flexible sensing.