Effect of surface charge and gap distance on electroadhesive forces in electret films

Electroadhesion (EA) is the phenomenon of surface adhesion caused by electrostatic attraction due to electric fields, whether externally applied or originating from quasi-permanent surface charges (i.e., passive EA).In the presented study, the adhesion force was provided by the charges stored in the electret polyethylene terephthalate (PET) film.This study provides a clear and quantitative understanding of how a PET electret film behaves as a passive electroadhesive material.The tested film was charged via direct-current corona discharge (point-plane electrode configuration, 10 kV) to impart a quasi-permanent surface charge.Key charge-storage characteristics (including surface potential distribution and charge decay time) were measured.This characterisation revealed a non-uniform (bellshaped) surface potential profile and long charge storage time on the PET film (t 95% > 980 s).Next, the electrostatic adhesion force between the charged film and a grounded conductive surface was quantified at various film-surface separations (0.5 mm to tens of millimeters) using a precision force measurement setup.The attractive force increases with the film surface charge and decreases steeply with increasing separation distance, reaching approximately 16.6 mN at a 0.5 mm separation (corresponding to a surface charge density of about 4.2 mC/m).These results demonstrate the feasibility of corona-charged PET as a low-power electroadhesive material.