To investigate the surface modification of polyimide（PI）film via dielectric barrier discharge（DBD）in air

a dielectric barrier discharge platform was built to measure the electrical characteristics of DBD of different materials under different air gap distances and to obtain corresponding discharge images

and a uniform DBD discharge mode was achieved.Then

PI films were treated with different time using the plasma

and the contact angle

surface energy and Fourier transform infrared spectra（FTIR）were measured.The action mechanism of plasma was also revealed.The results show that:1)ceramic barrier can achieve more uniform discharge than glass orepoxy resin barrier;2)with the increase of the air gap distance between ceramics

the duration and uniformity of discharge decrease

but the discharge power density is on the contrary

and smaller air gap distance is more suitable for polymer surface modification;3)with the increase of plasma treatment time

the contact angle of PI thin film decreases and the surface energy increases;and 4)the polar hydrophilic groups introduced to the surface of PI thin films

such as-OH andwell as the increase of roughness caused by plasma etching

are the main reasons for the increase of hydrophilicity and surface energy of PI films.