A Biaxial Stretchable Interconnect With Liquid-Alloy-Covered Joints on Elastomeric Substrate

This paper reports a biaxial stretchable interconnect on an elastomeric substrate. To increase the stretchability of interconnects, a 2-D diamond-shaped geometry of gold on a polydimethylsiloxane substrate was adopted in which the potentially breakable points were covered with room temperature liquid alloy. Finite element model simulations were performed to identify the most vulnerable points subjected to stress concentration and optimize the design process. Simulations also indicated an optimum gold thickness and linewidth that result in a minimum stress when the substrate is stretched. Four different geometries were designed, fabricated, and characterized. These included: 1) 2-D diamond-shaped gold lines connected at circular junctions with an intersection angle of 90
^deg
; 2) 2-D diamond-shaped gold lines connected at circular junctions with intersection angles of 120
^deg
and 60
^deg
; 3) 2-D diamond-shaped gold lines separated at circular junctions with an intersection angle of 90
^deg
; and 4) 2-D diamond-shaped gold lines separated at circular junctions with intersection angles of 120
^deg
and 60
^deg
. A maximum stretchability (Delta
L
/
L
) of ~ 60% was achieved for the design in which the lines and circles were separated and had intersection angles of 120
^deg
and 60
^deg
. A resistance variation of (Delta
R
/
R
) ~ 30% was measured for this configuration.