High conductivity in thin, flexible, and stretchable interconnect with polymer composite in a sandwich structure

Flexible conducting materials have been in the forefront of a rapidly transforming electronics industry, focusing on wearable devices for a variety of applications in recent times. Over the past few decades, bulky, rigid devices have been replaced with a surging demand for thin, flexible, light weight, ultra-portable yet high-performance electronics. The interconnects available in the market today only satisfy a few of the desirable characteristics, making it necessary to compromise one feature over another. In this paper, a method to prepare a thin, flexible, and stretchable interconnect is presented with improved conductivity compared to previous achievements. It satisfies most mechanical and electrical conditions desired in the wearable electronics industry. The conducting composite, prepared with the widely available, low-cost silicon-based organic polymer-polydimethylsiloxane (PDMS) and silver (Ag), is sandwiched between two cured PDMS layers. These protective layers improve the mechanical stability of the interconnect. The structure can be stretched up to 120% of its original length without compromising its electrical stability. The interconnect, around 300 µm thick, can be integrated into thin electronic packaging. The synthesis process of the composite material, along with its electrical and mechanical and properties, is presented in detail. Testing methods and results for mechanical and electrical stability are also illustrated over extensive flexing and stretching cycles.