Water-based conductive ink for highly efficient electromagnetic interference shielding coating

Conductive inks are applied widely in electromagnetic interference (EMI) shielding coating, but the heavy use of organic solvents may cause safety issues and environment pollution. We demonstrated the preparation of an eco-friendly conductive ink that is composed of silver flakes, waterborne polyurethane, and fluorocarbon surfactant (Capstone FS-30), with deionized water as solvent. The conductive ink can be drop-deposited easily on polyethylene terephthalate film to develop a highly efficient EMI shielding coating that achieves an ultrahigh EMI shielding effectiveness (EMI SE) of 74.5 dB at only 10 μm thickness. The shielding coating exhibits sufficient flexibility to ensure an EMI SE retention up to 96%, even after 5000 bending–releasing cycles (bending radius of 2 mm), which reveals an excellent EMI shielding reliability. The shielding coating also possesses a mechanical fastness under ultrasonic treatment and a chemical durability to various organic solvents. These impressive characteristics make our conductive ink attractive for effective electromagnetic protection, especially in high integrated equipment and devices.