This study demonstrates an easy way to change surface characteristics, the water contact angle on styrene based shape memory polymer (SMP) surface alters before and after cracking formation and recovery. The contact angle of water on the original SMP surface is about 85 degree, after coating with Al and then kneading from side face at glass transition temperature Tg, cracking appeared both on Al film and SMP; cooling down and removing the Al film, cracks remain on SMP surface while the contact angle reduced to about 25 degree. When reheated above Tg, the cracks disappeared, and the contact angle go back to about 85 degree. The thin Al film bonded on SMP surface was coated by spurting, that constrains the deformation of SMP. Heating above Tg, there are complex interactions between soft SMP and hard metal film under kneading. The thin metal film cracked first with the considerable deformation of soft polymer, whereafter, the polymer was ripped by the metal cracks thus polymer cracked as well. Cracks on SMP can be fixed cooling down Tg, while reheated, cracks shrinking and the SMP recovers to its original smooth surface. Surface topography changed dramatically while chemical composition showed no change during the deformation and recovery cycle, as presented by SEM and EDS. Furthermore, the wetting cycle is repeatable. This facile method can be easily extended to the hydropobicity/hydrophilicity modification of other stimuli-responsive polymers and put forward many potential applications, such as microfluidic switching and molecule capture and release.
Dielectric loading in bandpass double-layer frequency selective surface design is a necessary process. The problem that dielectric loaded inducing the transmission loss in the centre of the frequency response curve is difficult to be avoided. Hexagon aperture FSS array is studied by numerical calculation and simulation analysis. The different way of loading dielectric, the different dielectric constant of double-layer FSS and the different coupling way of the two layer transmission curve have great influence on the transmission characteristics. Simulation results show that decreasing the thickness and permittivity of the dielectric can reduce the transmission loss. Besides, the sunken degree in the centre of the pass-band can be improved by extending the bandwidth. Aiming at comprehensive improving the transmission characteristics like band width, cutoff steepness, polarization and angle insensitivity and transmission loss, a modified dielectric loaded double-layer hexagon aperture FSS array structure is designed.
A high optical transparent and wireless communication band-pass window with hexagon-loop aperture ITO frequency selective surface (FSS) array structure is developed. The parameters of hexagon-loop aperture FSS are designed as h = 5.5mm, w = 0.5mm, d = 2mm according to empirical formula of resonance frequency. The bandpass filtering characteristics of different dielectric-loaded FSS windows with the same dielectric thickness e=0.5mm are simulated and comparatively analyzed. Through calculation results and simulation analysis, it can be found that single-layer dielectric-loaded FSS windows have more stable and desired resonance frequency of 5.8GHz, wider symmetrical bandwidth and independence of incidence angle and polarization than that of double-layer ones at large incidence angles. So it can be concluded that single-layer dielectric-loaded FSS windows are suitable for ISM wireless communication bandpass filtering application.