Thin-film stretchable electronics technology based on meandering interconnections: fabrication and mechanical performance

Abstract

A new fabrication technology for stretchable electrical interconnections is presented. This technology can be used to connect various non-stretchable polyimide islands hosting conventional electronic components. The interconnections are realized by patterning a 200 nm thick sputter-deposited gold film into meandering horseshoe shapes, functioning as 'two-dimensional springs' when embedded in a silicone elastomer. Polyimide support is introduced around the meandering conductors as a means to improve the mechanical performance. Processing is done on a temporary carrier; the islands and interconnections are embedded in polydimethylsiloxane in a final stage. To this end, a release technique compatible with high temperatures up to 350• C based on the evaporation of a 400 nm thick layer of potassium chloride is developed. Test structures consisting of stretchable interconnections with a varying polyimide support width were fabricated. These were strained up to twice their original length without compromising their functionality. Also cyclic mechanical loading at various strains was performed, indicating the influence of the polyimide support width on the lifetime. At strains of 10%, a minimum lifetime of 500 000 cycles is demonstrated. The presented technology thus provides a promising route towards the fabrication of stretchable electronic circuits with enhanced reliability.

Flexible and stretchable electrodes for dielectric elastomer actuators

“…They found that a "horseshoe" shaped track with a conductive width as small as possible was the best solution, and they reported elongation at break up to 100%, which is slightly above the non-optimized zigzags tracks of Perlrine et al presented in the previous paragraph. The technique was further developed by Verplancke et al by sandwiching the meandering track between two spin-coated polyimide layers as a means to improve mechanical performance [51]. They obtained reproducible uniaxial stretching up to 100% without noticeable change in resistance (R 0 ≈ 180Ω) or hysteresis.…”

Stretchable Magnetoelectronics

“…The approach of metal meanders was mainly used to fabricate highly conductive stretchable interconnects 29 and antennas 53 . Later, the geometry and preparation of the meanders was further optimized to horseshoeshapes 20,30,144 or self-similar 32,52 designs embedded into microstructured polymer supports, which makes these interconnects able to accommodate up to some hundred percent of tensile deformation.…”

Stretchable optical waveguides

“…To make these interconnections mechanically stretchable, 2 approaches have been adopted. In a first approach, traditional conductors such as copper, gold or silicon are patterned as spring-like structures instead of straight lines [4][5][6][7]. In a second approach, an electrically conductive stretchable material itself is used to create the interconnections [8].…”