Ultra-foldable/stretchable wideband RF interconnects using laser ablation of metal film on a flexible substrate

In this paper we demonstrate the feasibility of mechanically flexible and stretchable coplanar waveguide (CPW) transmission lines at millimeter-wave frequencies. Our approach is based on meander horseshoe-shaped CPW line on 125 μm-thick Polyethylene Naphthalate (PEN) dielectric substrate. The desired meander shape pattern of the conductor is structured using a nanosecond pulsed laser source operating at 351 nm wavelength by the precise patterning of a 1 μm-thick conductive film deposited on a plastic foil. The cutout is realized by following the outer meander shape path of the structure providing an ultra-flexible/stretchable interconnect line. An experimental attenuation below 0.12 dB·mm-1 for a 13 mm length of signal conductor has been obtained at 40 GHz. When submitted to bending on a semi-cylinder of known radius, the measured transmission coefficient show small variations less than 0.05 dB even for bending radius in the centimeter range.